Artificial cells in immobilization biotechnology.

Artif Cells Blood Substit Immobil Biotechnol Downloaded from informahealthcare.com by UB Kiel on 12/29/14 For personal use only.

BIOMAT., ART. CELLS & IMMOB. BIOTECH., 20(5), 1121-1143 (1992)

ARTIFICIAL CELLS IN lMMOBlLIZATION BIOTECHNOLOGY Thomas Ming S w i Chang, O.C.,M.D.,Ph.D.,FRCP(C) Professor a n d Director Artificial Cells & Organs Research Centre F a c u l t y of Medicine, McCill University 3655 Drummond Street, Montreal, P.Q., Canada, H 3 G 1Y6 ABSTRACT Artificial cells contain biologically active materials. Artificial cells containing adsorbents have been a routine f o r m of treatment in hemoperfusion f o r patients. This includes acute poisoning, high blood a l u m i n u m a n d iron, a n d supplement t o dialysis i n kidney failure. Artificial cells a r e being tested f o r use a s r e d b l o o d c e l l s u b s t i t u t e s . A r t i f i c i a l c e l l s e n c a p s u l a t e d c e l l c u l t u r e a r e being tested in animals f o r t h e treatment of diabetes a n d liver f a i l u r e . A novel 2 s t e p method h a s p r e v e n t e d x e n o g r a f t rejection. A r t i f i c i a l cells containing enzymes a r e being studied f o r treatment in hereditary enzyme d e f i c i e n c y diseases a n d o t h e r diseases. R e c e n t d e m o n s t r a t i o n of e x t e n s i v e e n t e r o r e c i r c u l a t i o n of a m i n o a c i d s in t h e i n t e s t i n e h a s a l l o w e d i t s o r a l a d m i n i s t r a t i o n t o d e p l e t e s p e c i f i c a m i n o acids. A r t i f i c i a l cells c o n t a i n i n g complex enzyme system convert wastes like urea a n d ammonia into esscntial a m i n o acids. A r t i f i c i a l cell is b e i n g used f o r t h e p r o d u c t i o n of monoclonal antibodies, interferons a n d other biotechnological products. It is also being i n v e s t i g a t e d f o r d r u g d e l i v e r y , a n d f o r use i n o t h e r a p p l i c a t i o n s i n biotechnology, chemical engineering a n d medicine. I. I N T R O D U C T I O N i. Immobilization

A n international committee o n nomenclature used the term IMMOBILIZATION t o classify the following 4 groups of technology used in biotechnology ( I ) : I . Covalent Linkage 2. Adsorption 3. Matrix e n t r a p m e n t 4. Microencapsulation (Artificial Cells)

This is a n expanded a n d updated version of the opcning lecturc prcscntcd a t t h e X Intcrnational Symposium on Hcmopcrfusion,Sorbents & Immobilized Bioreactnnts, Rome, Italy.

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Copyright 0 1992 by Marcel Dekker, Inc.

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Fig. I Schematic representation of artificial cells: I - Intracellular environment of artificial cell x - Substrates and other materials entering the artificial cell y - Products, secretions etc leaving the artificial cell

ii. Basic prineiple of artificial cells

What is artificial cell ? I n t h e author's 1972 book on Artificial Cells (7). he gave the following description: "Artificial cell is not a specific physical entity. It is a n idea involving t h e p r e p a r a t i o n of a r t i f i c i a l s t r u c u t r e of c e l l u l a r d i m e n s i o n s f o r p o s s i b l e r e p l a c e m e n t o r s u p p l e m e n t of d e f i c i e n t cell f u n c t i o n s . I t i s c l e a r t h a t d i f f e r e n t approaches c a n be used to demonstrate this idea." a r t i f i c i a l c e l l s is s u c h t h a t i t s m a j o r The basic principle of applications a r e in Medicine a n d Biotechnology. Figure I summarises t h e basic prinicplc of artificial cells. T h e permeability can be controlled over a wide range. This way, t h e enclosed material can be retained a n d separated f r o m undcsirable external materials (Fig. I ) . At the same time, the large s u r f a c e area a n d the ultrathin membrane allows selected substrateso(), a n d products(Y) to permeate rapidly (Fig. I ) . Mass transfer across 100 ml of artificial cells can be 100 times higher t h a n t h a t f o r a standard hemodialysis machine.


CELLS IN IMMOBILIZATION BIOTECHNOLOGY

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Fig. 2 Variations in contents. O n e o r more of the above materials c a n be enclosed within t h e same a r t i f i c i a l cell.

L i k e b i o l o g i c a l c e lls , a r t i f i c i a l c e l l s c o n t a i n b i o l o g i c a l l y a c t i v e materials. However, the content of a rtific ia l cells can be more v a r i e d t h a n biological cells ( Fig 2 ) . These inc lude both biological a n d s y n t h e t i c materials. T h e m em br anes of a rtfic ia l cells c a n also be extensively v a r i e d using s y n t h e t i c or biological materials.

iii. A r t i f i ci al cells in t h e last 35 years By 1965, h e T h e a u t h o r firs t reported a rtific ia l cells 35 years a g o (2). showed t he feasibility of a rtific ia l cells for blood subsitutes; e n z y m e therapy; encapsulation of cell c ulture s f o r dia be te s a n d liver f a i l u r e ; d r u g delivery, u r e a r e m o v a l a n d o t h e r a p p l i c a t i o n s (3,4,5). U n f o r t u n a t e l y , a t t h a t t i m e , o t h e r s s h o w e d l i t t l e o r n o i n t e r e s t in d e v e l o p i n g t h i s a p p r o a c h . T h e f i r s t major interest shown by othe r groups was a f t e r t h e author’s r cpor t on his research a n d development of a rtific ial cells f o r h e m o p e r f u s i o n in 1966(4). This interest intensified a f t e r successful clinical trials a n d a ppl i cat i on of hemoperfusion in pa tie nts here (7). T h e second major impetus was in the 1980’s. T h i s was t h e time o f incrcasing i n t e r n a t i o n a l interests in all a r e a s of biotcchnology. M a n y m a j o r g r o u p s s t ar t ed to actively c a r r y out rescarch a n d dcvclopcmcnts o n t h e biotechnological T h e p o t e n t i a l problem of appr oaches of ar t ific ia l cells s ta rte d in t h e 1960’s. AIDS in t r ans f us i o n blood is a nothe r major stimulus in a n o t h e r a r e a of research of ar t i f i ci al cell, blood substitutes. T h e r e a r e now n u m c r o u s major c e n t r e s a c t i v e l y c a r r y i n g out research on a r t i f i c i a l cells f o r immobilization biotechnology. This ha s led to very ra pid progress in this field in the recent years (8-1 I ) .

11. P R E P A R A T I O N , M A T E R I A L S A N D CONTENTS.

Many methods a r c now a va ila ble f o r the pr e p a r a t i o n of a r t i f i c i a l cells. Thi s brief over vie w is not t h e place to describe these methods. G e n c r n l l y speaking, t he most commonly used approaches a r e based on:

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Fig. 3 Preparation of small artificial cells by emulsification method.

i. hlethod of preparation

Sinall artificial cells. This is prepared by emulsification procedures which a r e u s u a l l y m o d i f i c a t i o n s of t h e a u t h o r ' s b a s i c p r o c e d u r e s ( 2 - 6 ) ( F i g . 3 ) . However, there has been tremendous improvements and modifications by d i f f e r e n t centre. This has resulted in d i f f e r e n t procedures f o r specific applications (7I I) Larger artificial cells. Drop techniques a r c generally used to prepare l a r g e r a r t i f i c i a l c e l l s , e s p e c i a l l y f o r e n c a p s u l a t i o n o f cells. T h e a u t h o r ' s original d r o p technique ( 5 - 7 ) forms t h e basis of these methods. T h e large n u m b e r of c e n t r e s i n t h i s a r e a h a s p r o d u c e d e x t e n s i v e i m p r o v e m e n t s a n d This will be discussed variations f o r d i f f e r e n t biotechnological applications. later. A r t i f i c i a l cells containing sorbents. This is usually based o n t h e author's use of ultrathin membrane coating of sorbcnt granules (4,7,12). Again d i f f e r e n t approaches a r e n o w available f o r d i f f e r e n t applications.

ii. Variations in membrane materials. a. Synthetic polymers.Different types of synthetic polymers can be used (Fig.4). Variations in configuration a r e also possible(Fig.4). A single ultrahin polymer membrane is the most common one. T h e unlimited type of polymers used allow for possible v a r i a t i o n s in permeability, b i o c o m p a t i b i l i t y a n d o t h e r Artificial cells can also be made to contain smaller characteristics (2-1 I). "intracellular compartments" ( 5 - 7 ) (Fig.4). Others c a n be prepared t o f o r m s o l i d p o l y m e r m i c r o s p h e r e s c o n t a i n i n g m i c r o d r o p l e t s of b i o l o g i c a l l y a c t i v e Liquid hydrocarbons f o r m microdroplets containing biologically materials ( 5 ) . active materials which a r c useful i n biotechnology a n d other applications (13).



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Fig. 4

b.Biodegradable or biological materials. These a r e useful f o r a r t i f i c i a l cells w i t h shorter d u r a t i o n of functions a f t e r injection. D i f f e r e n t materials have been used. This is outlined schematically (Fig. 5). Protein Protein membrane artificial cells a n d polyhemoglobin a r e t w o examples (3.5-7). Lipid T h e use of lipid is another common approach. T h i s includes the use of lipid-protein membrane (7). concentric lipid membranes a n d submicron ultrathin lipid membrane (14). Biodegradale synthetic polymer Another approach is biodegradable synthetic polymer. T h e first one used is polylactide (15) (Fig.5). Many types of polylactides a n d polyglycolic acids a r e being used f o r artificial cells a t p r e s e n t (16). O t h e r s y n t h e t i c b i o d e g r a d a b l e p o l y m e r s c a n a ls o b e u s e d . Polyanhydride is one example (17). Biodegradable artificial cells is n o w a very active field iii. Variations in contents As discussed earlier (Fig.Z), extensive variation i n contents is possible. Figure 6 shows the first report of some of the most commonly studied systems. Some of thcse will be discussed.


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Fig. 5

Biological and biodegradable a r t i f i c i a l cells

Fig. 6 Examples of variations of cantciits



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Fig. 7 Schematic representation of artificial cells containing activated charcoal f o r hemoperfusion.

111. S O R B E N T S A N D I M M U N O S O R B E N T S IN HEhlOPERFUSION

This is t h e simplest f o r m of artificial cells which h a s already been used in routine clinical applications f o r some time. i. General. Sorbents like activated charcoal, resins a n d immunosorbents cannot be used in direct blood perfusion. T h i s is becausc of particulate embolism a n d blood cells removal. T h e a u t h o r showed t h a t sorbents like activated charcoal inside artificial cells n o longer caused particulate cmbolism a n d blood cells removal (4,7,12)(Fig.7)

T h i s was therefore developed a n d used succcssfully i n patients (7). T h e hemoperfusion dcvicc being used in patcints is shown in Fig. 8. It contains 70 gm o f a r t i f i c i a l cells. E a c h a r t i f i c i a l cell is f o r m c d by applying a n ultrathin coating of collodion membrane on each of the 100 micron diameter activated charcoal microsphcres. T h e mass t r a n s f e r f o r t h i s s m a l l d c v i c c is m a n y t i m e s higher t h a n t h a t for a standard dialysis machine. Extcnsive clinical d a t a is now available f r o m this a n d other groups. Fig. 8


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Fig. 9 Preparation of artificial cclls encapsulating intact biological cells

ii. Acute poisoning.Our demonstration of its use i n patients with acute This is now a routine poisoning (18), is now supported by other groups. t r e a t m e n t f o r b o t h a d u l t a n d p e d i a t r i c p a t i e n t s (19). T h e r e a r e c e r t a i n requirements (19). I . Drug o r toxin can be adsorbed by activated charcoal. 2 . Volume distribution should allow sufficient level in circulating blood f o r removal. 3. Treatment must be started before irreversible damage. iii. Chronic renal failure. In chronic renal failure, we showed that it is more effective t h a n hernodialysis in removing organic metabolites (7,12,20). T h i s is b e i n g u s e d i n 2 w a y s . ( I ) In s e r i e s w i t h d i a l y s i s , w e s h o w e d t h a t i t shortened dialysis time a n d improved dialysis resistant symptoms (7,20). This i s s u p p o r t e d b y m a n y o t h e r g r o u p s (21-25). ( 2 ) In s e r i e s w i t h a s m a l l ultrafiltrator (20) it can replace t h e dialysis machine (20). Here we used oral adsorbents to control potassium a n d phosphates. A n urea removal system is being developed t o complete t h e hemoperfusion-ultrafiltratorapproach. i v . Liver failure. The a u t h o r showed that t h e detoxifying functions of hemoperfusion resulted in temporary recoveries of coma in grade IV hepatic coma patients (26). Williams, Odaka, Winchester, Agishi a n d others supported this o b s e r v a t i o n ( 19,22,23,24,25,27). We c a r r i e d o u t r a n d o m i z e d c o n t r o l s t u d i e s i n f u l m i n a n t hepatic f a i l u r e ( F H F ) rats(28). Hemoperfusion significantly increased the survival rates of F H F rats in earlier coma but not i n latc coma(28) Williams’ g r o u p l a t e r r e p o r t e d t h e s a m e r e s u l t i n p a t i e n t s ( 19,27). Hemoperfusion is more effective than the liver in detoxication. On the other h a n d , i t d o e s n o t f u l f i l l t h e o t h e r c o m p l e x h e p a t i c f u n c t i o n s . In a l a t e r s e c t i o n w e s h a l l be d i s c u s s i n g t h e use of a r t i f i f i c i a l c e l l s c o n t a i n i n g hepatocytes as possible supplement to hemoperfusion

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(1st ref: Chang,1965, Chang et al 1 9 6 6 )

YE

SUBSTRATES OXYGEN NUTRIENTS TOXINS,WASTES

ANTIBODIES

Y

LEUCOCYTES

CRETIONS ormones etc)

-+ PRODUCTS

pq -4Fig. 10 Schematic representation of use of artificial cells cncapsulated cells to prevent rejection.

v . Aluminium and Iron overload. We used this with desferroxaimine in patients with high a l u m i n u m levels (29). This is now a routine treatment f o r removing a l u m i n u m or iron in patients (19,30).

v i . lininunosorbents a n d other adsorbents T h e a u t h o r used a r t i f i c i a l cells for other sorbents (4.7) a n d immunosorbents ( 3 1 ) . This is a n o t h e r exciting a r e a under laboratory a n d clinical investigation by a number of groups.

IV. ARTIFICIAL CELLS C O N T A J N I N C LIVING BIOLOGICAL CELLS i. Basic principle In 1965, the a u t h o r devised a d r o p method to microencapsulate biological cells(5) (Fig. 9). A crosslinked protcin membrane was used(5,6,7). His earlier d r o p technique bascd on interfacial coacervation (2) could also be used.

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Fig. 1 1 Standard procedure f o r the preparation of alginate-polylysine-alginate membrane artificial cells containing cells

The a u t h o r proposed this f o r use as follows (5,6,7) (Fig. 10): " . . p r o t e c t e d f r o m . . i m m u n o l o g i c a l p r o c e s s ... e n c p a s u l a t e d e n d o c r i n e c e l l s might survive a n d maintain a n effective supply of hormone" (5)

"For organ deficiency ...cultures of liver cells...in artificial cells"(5) i i . Diabetes We persuaded Connaught Laboratory of insulin f a m e to develop this f o r diabetes. Finally, Sun a t Connaught with Lim (32) a n d later others (33.34) reported t h e i r studies. T h e y s h o w e d t h a t islets inside a r t i f i c i a l cells a r e indeed prevented f r o m immunorejection a f t e r implantation into animals. Islets c a n indeed remain viable a n d continued to secrete insulin to control t h e glucose levels of diabetic rats. Goosen a n d Sun improved t h e biocompatibility by t h e use of a alaginate-polylysine-alginate membrane improved biocompatbility (33). SoonShiong's group used a special alginate to f u r t h e r improve t h e biocompatibility (34).

iii. Liver failure Wong a n d Chang f o u n d t h a t artificial cells containing hepatocytes increased t h e survival time of f u l m i n a n t hepatic f a i l u r e rats (35). T h e y also showed t h a t xenografts of r a t hepatocytes i n artificial cells were not immunorejected in mice (36). Instead of rejection the viability of t h e enclosed liver cells increased a f t e r intraperitoneal implantation(36). Kansani a n d C h a n g showed t h a t this was d u e to the accumulation of hepatotrophic f a c t o r in t h e artificial cells (36). Hepatocytes secrete a hepatotrophic factor (36). B r u n i a n d C h a n g showed t h a t a f t e r i m p l a n t a t i o n , hepatocytes in a r t i f i c i a l cells c a n lower t h e high



F i g u r e 12 Partial exposure of evcn I cell on the s u r f a c e of artificial cell c a n result i n imrnunorejection of thc artificial cell.

Fig. 13 N e w 2 Step method of encapsulation of cells to prevent exposure of cells on s u r f a c e of artificial ccll.

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Fig. 14 New 2 step method prevents the exposure of cells o n the s u r f a c e of artificial cells

bilirubin level in the G u n n rats (37). Recent reports by the groups of S u n , Shu, Dixit a n d others (38) also support the use of artificial cells containing hepa tocytes. iv. Novel method t o improve t h e alginate-polylysine-alginate method The most commonly used method a t present f o r cell encapsulation is thc alginate-polylysine-alginate method (33). T h i s m e t h o d is t h e r e s u l t o f extensive research by Sun’s group to improve our original method ( 5 ) (Fig. 10). We recently f o u n d t h a t using this method, occasional hepatocytcs were sometimes exposed on t h e s u r f a c e of artificial cells (Fig. 1 1 , 12). Partial cxposurc of just 1 hepatocyte would result i n the rejection of the whole artificial(Fig. 12).

We have therefore devised a new method to allow f o r better inimuneisolation of cells in artificial cells (39) (Fig. 13, 14). v. Artificial cells containing microorganisms and other cells Artificial cells containing microorganisms can convert cholesterol in serum in-vitro into carbon dioxide (40)(Fig 15). Many other groups a r e also s t u d y i n g a r t i f i c i a l cells c o n t a i n i n g living cells. These include those of Sefton, Tice a n d Meyer, Goosen, Shiotani, Soon-Shiong a n d many others (41). T h i s approach is also useful in biotechnology. For example, Damon Co. in B o s t o n u s e d a r t i f i c i a l c e l l s c o n t a i n i n g hybridoma f o r the production of monoclonal a n t i bodies.

Fig. 15


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ENZYMES

IN ARTIFICIAL CELLS Artif Cells Blood Substit Immobil Biotechnol Downloaded from informahealthcare.com by UB Kiel on 12/29/14 For personal use only.

(1st Ref: Chang,l957,1964)

+RODUCTS

SUBSTRATES--

ANTIBODIES

\ DESTRUCTIVE SUB

Fig. 16 Schematic representation of enzyme inside artificial cells

IV. A R T I F I C I A L CELLS C O N T A I N I N G ENZYMES, A N D M U L T I E N Z Y M E S Y S T E M S

i. Principle Artificial cell protects t h e enclosed enzyme f o r immunological rejection or tryptic enzymes (3-7) (Fig. 16). Substrates can equilibrate rapidly into t h e artificial cells for conversion into products (Fig. 16). ii. U r e a removal We showed t h a t artificial cells containing urease c a n convert urea to ammonia which is t h e n removed by ammonia adsorbent (3-7). T h i s approach has been developed f u r t h e r by us a n d other groups including Sparks, G a r d n c r a n d others (8-1 l,42). I n 1981, Kjellstrand’s group showed t h e clinical feasibility of this approach in uremic patients (42). We a r c continuing with research to of i m p r o v e i t s c a p a c i t y (43). A l a t e r s e c t i o n w i l l d e s c r i b e o u r s t u d i e s artificial cells to convert urea a n d ammonia to essential a m i n o acids. i v . Hereditary enzyme d e f e c t s

A r t i f i c i a l c c l l s h a v e b e e n uscd i n h c r c d i t a r y e n z y m c d c f c c t s . T h i s i n c l u d c s i t s use b y C h a n g a n d P o z n a n s k y f o r r e p l a c e m c n t of c a t a l a s c i n acatalasemic mice (44). Chang a n d Chong studied asparaginase artificial cclls f o r asparaginc removal (45). Shu a n d Chang studied t h e use of tyrosinasc a r t i f i c i a l c c l l s f o r r e m o v i n g t y r o s i n e (46). B o u r g e t a n d C h a n g u s c d

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Fig.17 Extensive enterorecirculation of body amino acids. Oral enzyme artificial cells can deplete specific body amino acids.

Fig. 16

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ARTIFICIAL CELLS FOR BILIRUBIN REMOVAL


( D a t a & Chang.1989)

-oxidation

bilirubin

GLUCOSE OXIDASE

glucose

Fig. 19

phcnylalanine ammonia lyase artificial cells in phenylketonuria (47). K h a n n a a n d C h a n g used histidinasc artificial cclls to remove histidine (48). C h a n g a n d his collaborators studied orally administercd artificial cclls containing x a n t h i n e oxidase(49). T h i s resulted in decrcase in systemic hypoxanthine in a pediatric patient with hypoxanthinuria (Lesch-Nyhan Disease) (49). Wang a n d Shao (50) s t u d i e d lactase a r t i f i c i a l cells f o r possible a p p l i c a t i o n i n lactoseintolerance. iv. Enterorecirculation Chang a n d Lister (51) f o u n d a n extensive enterorecirculation of a m i n o acids in the intestine. T h i s allows them to give enzyme artificial cclls orally to selectively remove specific a m i n o acids f r o m the body(51) (Fig. 17). v. Multienzyme system

Most enzymes in biological cells f u n c t i o n as complex enzyme systems. We have prepared artificial cells to contain multienzyme systems w i t h cofactor recycling (52). Gu a n d Chang ( 5 3 ) used this approach to convert urea a n d ammonia into csscntial a m i n o acids like lcucine, isoleucine a n d valine (Fig. 18). Daka a n d Chang (54) prepared artificial cells containing hemoglobin with pseudoperoxidase activity a n d glucose oxidase t o remove bilirubin (Fig. 19). Protein bound bilirubin can be removed this way using cross-linked system w i t h thc enzyme systems exposed on t h e s u r f a c e (54).

V. RED BLOOD CELL SUBSTITUTES.

The 2 major approaches are ( i ) Modified hemoglobin a n d (ii) Perfluorochemicals. Detailed reviews by t h e a u t h o r a n d experts in t h e field a r e availablc in rcccnt symposium volumes in this journa1(55,56). Therefore the prcscnt overview on artificial cell only includes a vcry brief s u m m a r y of this very large a n d active field. Please r e f e r to t h e symposium volumes(55,56) of this journal f o r specific references which will not be repeated here.

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i. Modified hemoglobin: ]Microencapsulated hemoglobin. T h e author prepared t h e first modified hemoglobin i n the f o r m of artificial red cells microencapsulating hemoglobin (2). T h e enclosed hemoglobin continued to reversibly c a r r y oxygen. We showed t h a t these artificial red blood cells h a d n o blood group antigens(5,7). T h e We modified their s u r f a c c circulating time a f t e r infusion was short (3.5-7). properties a n d diameter. This increased the circulating time (3,5-7). In 1980, Djordjevich & Miller prepared lipid membrane artificial red cells of submicron sizes(S5). T h i s r e s u l t e d i n f u r t h e r i n c r e a s e in c i r c u l a t i n g t i m e (55). M a n y other groups have since made f u r t h e r important progress - Hunt, Farmer, Tsuchida, Schmidt, Rudolph, Beissingcr, a n d many others (55,561. Crosslinked hemoglobin. In 1964 the author reported cross-linking hemoglobin into polyhemoglobin or conjugated hemoglobin to f o r m membranes or small microspheres (3.5-7). In 1968, Bund & Jondl prepared soluble polyhemoglobin to increase circulating time (55.56). In 1975, Benesch pyridoxalated hemoglobin to improve the P50 of polyhemoglobin (52). F u r t h e r studies by many groups include new crosslinking agents, intramolecular crosslinkage, conjugated hemoglobin, These groups bovine hemoglobin, physiopathology a n d clinical trials (55,S6). include Abuchowski, Agishi, Bakker,Biro, Bucci,Chang, DeVenuto, Estep, Faivre, Feola, Grccnburg, Hedlund, Hori, Hsia, Iwashita, Jesch, Messmer, Moss, Nose, Pristoupil, Sekiguchi, Sideman, Valeri, Winslow, Wong a n d many others (55,56). New approaches. T w o new approaches a r e in t h e horizon (56). Tsuchida in Japan incorporates synthetic heme into artificial cells. T h e other is t h e use of recombinant techniques to produce human hemoglobin in microorganisms or in animals. Present status. Most modified hemoglobins a r e effective as short-term blood substitute (5536). As a result clinical trials a r e forthcoming. However, animal safety results a r e not complctely applicable t o human. We used h u m a n plasma f o r testing complement activation of modified hemoglobin (57). This test may bridge t h e g a p between animal studies a n d clinical trials i n h u m a n (57). ii. Perfluorochemicds: Developments. Fluorocarbon ( 5 5 ) was first studied i n 1966 by Clark a n d later Sloviter f o r organ perfusion. I n 1968 Geyer showed t h a t i t can replace all blood in rats breathing oxygen (55). Naito’s group in J a p a n developed this f o r clinical trials in 1976 (55). One of the problems i n these initial clinical trials was complement activation (55). Changing t h e surfactant, especially i n studies by Reiss’s group, has solved this problem (56). Present status. It is now used in coronary perfusion i n patients (56). Its use f o r transfusion is being explored(56). This includes f u r t h e r studies on increase in oxygen carrying capacity a n d effects o n t h e reticulocndothelial systems(56). M a n y g r o u p s h a v e been m a k i n g i m p o r t a n t p r o g r e s s i n perfluorochemical research. These a r e Chen, Clark, F a i t h f u l , Geyer, Goldstick, Long, Lowe, Lutz, Meinert, Mitsuno, Ohyanagi, Riess, Rockwell, Shrewsbury, Spence, Teicher, Yokoyama a n d many others (55.56). V1. BIODEGRADABLE ARTIFICIAL CELLS

Another a r e a is the use of biodegradable artificial cells especially for d r u g delivery. T h i s has a l r e a d y been discussed u n d e r t h e section on p r e p a r a t i o n . We h a v e used c r o s s - l i n k e d p r o t e i n (3,s-7) a n d b i o d e g r a d a b l e


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TABLE I PRESENT S T A T U S O F ARTIFICIAL CELLS IN IMMOBILIZATION BIOTECHNOLOGY AND MEDICINE 1. Hemoperfusion for a c u t e poisoning - routine treatment in patients 2. Hemoperfusion f o r a l u m i n i u m a n d iron overload - routine treatment in patients 3. Supplement to hemodialysis in end-stage renal f a i l u r e - routine treatment in patients 4. Artificial liver support: hemoperfusion a n d hybrid systems - experimental 5. Red blood cell substitutes f o r transfusion - clinical trial & experimental 6. Blood group antibodies removal (immunosorbents) - clinical trial 7. Hereditary enzyme deficiency - clinical trial 8. Clinical laboratory analysis - clinical application 9. Production of monoclonal antibodies 10. Diabetic mcllitus a n d other endocrine diseases - animal experiment 11. D r u g delivery systems - clinical application a n d experimental 12. Conversion of cholesterol into carbon dioxide - experimental 13. Bilirubin removal - experimental 14. Production of f i n e biochemicals 15. Food a n d a q u a t i c culture 16. Conversion of wastes i n t o useful products - experimental 17. O t h e r biotechnological a n d medical applications

Many groups a r e extending these approaches polylactide artificial cells ( I 5). for use in drug delivery (medications,hormones, peptides and proteins)( 16,17,58,59). We prepared lipid-protein a n d lipid-polymer artificial cells to encapsulate biologically active materials(60). Later, Gregoriadis prepared concentric lipid membrane liposomes containing enzymes (14). Liposomes a r e multiple lipid layers onion-skin-like microspheres originally used by Bangham f o r basic membrane research. Workers in liposomes more r e c e n t l y t u r n c d t o p r e p a r i n g small submicron a r t i f i c i a l cells with a single bilayer lipid membrane. These lipid membrane artificial cells a r e no longer concentric lipid membrane liposomes. Some s t i l l c o n t i n u e t o c a l l t h e s e " l i p o s o m e s " ( 1 4 ) . T h i s h a s c r e a t e d s o m e confusions i n t h e field. These submicron bilayer lipid membrane a r t i f i c i a l cells a r e now used f o r microencapsulation of hemoglobin f o r red blood cell substitutes(55,56). T h e most extensive research is in its use f o r d r u g delivery (14). Since d r u g delivery is not the subject of the present overview, readers a r e referred to t h e detailed reference on this topic(l4).

V I I . P R E S E N T S T A T U S AND F U T U R E PERSPECTIVES

T a b l e I summarizes t h e present status. Artificial cells can contain a n unlimited number of biologically active materials. T h e r e a r e t h e r e f o r e m a n y other a r e a s of applications a n d research. For example, t h e a u t h o r h a s enclosed This magnetic a n d biological materials together inside artificial cells ( 4 ) . allows for localization with external magnetic fields (4). K a t o appplied magnetic f i e l d a p p l i e d o u t s i d e t h e b o d y of a n i m a l s ( l 1 ) . T h i s c a n d i r e c t magnetic artificial cells containing radioactive materials a n d chemotherapeutic agents to specific sites of bladder cancer. Magnetic artificial cells a r e also used i n bioreactors. Others have used artificial cells in laboratory analysis of f r e e a n d protein-bound hormones in patients ( 1 1 ) . We have studied its use for I-shot vaccine (61) a n d for removing large lipophyllic molecules f r o m small h y d r o p h y l l i c m o l e c u l e s (62). Still1 o t h e r s h a v e used a r t i f i c i a l c e l l s f o r

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industrial a q u a t i c culture f o r shrimps, lobsters a n d oysters. We have also studied artificial cells containing hepatic rnicrosomes a n d cytosol (63). Spirin used this approach f o r gene expression in biotechnology (64). Future perspective The a u t h o r wrote the following f u t u r c pcrspcctive i n his 1972 book on "Artificial Cells"(7). T h i s f u t u r e perspective is even more valid i n 1992

" A r t i f i c i a l c e l l is a c o n c e p t ; t h e e x a m p l e s d e s c r i b c d ....a r e b u t p h y s i c a l examples f o r demonstrating this idea. In addition to extending and modifying t h e p r e s e n t p h y s i c a l e x a m p l e s , c o m p e t e l y d i f f e r e n t s y s t e m s c o u l d be m a d e a v a i l a b l e t o f u r t h e r d e m o n s t r a t e ...... t h e i d e a o f a r t i f i c i a l c e l l s . T h e i s l i m i t e d o n l y b y one's i m a g i n a t i o n . A n p o t e n t i a l o f a r t i f i c i a l c e l l s ___. entirely new horizon is waiting impatiently to be explored." V I I I . ACKNOWLEDGMENTS T h e support of t h e Medical Research Council of C a n a d a in t h e operating term grant (MT-9100) a n d the MRC career invcstigatorship is gratefully acknowledged. T h e support of the Quebec Ministry of Education, Science a n d Technology f o r the Virage Award of C e n t r e of Excellence in Biotechnology i n 1985 a n d its permanent integration into this research centre in 1990 is also gratefully acknowledged.

IX. BIBLIOGRAPHY: 1. S u n d a r u m P V , P y e E K ,ChangTMS,EdrvardsVH,HumphreyAE,KaplanNO,KatchalskiE,LevinY,LillyMD, Manecke G , Mosbach K, Patchornik A, Porath J , Weetall HH, Wingard LB Jr. Recommendations for standardization of nomenclature in eneyme technology. Biotechnol. & Bioenn. 1972J4.15-18,Syrnp. vol. 3.15-182 Chang TMS Hemoglobin corpasulea. Research Report for Honours Physiology, Medical Library, MeGill University 1957. 3. Chang TMS. Semipermeable microcapsules.

1964;146:524-525.

4 . Chang TMS. Semipermeable aqueous microcapsules ("artificial cella"): with emphasison experiments in an extracorporeal shunt system. Trans Am Soc Artif Intern Oraans 1966;12:13-19.

5. Chang TMS.Semipermeable aqueous microcapsules. Ph.D.Theais, McGill University, 1965. 6. Chang TMS, Macintosh FC,Mason SG. Semipermeable aqueous microcnpsules. I. Preparation and properties.

Can. J. Phvsial

Pharmacol., 1966;44:116-128 Chang TMS, MaclntoshFC,MasonSG. Encapsulated hydrophilic compositions and methods ofmaking them Canadian Patent, 873,815, 1971. 7.Chang TMS. Artificial Cells. Springfie1d:C.C. Thomas Publisher, 1972

8. Chang TMS. Biotechnological and medical applications based on immobilization of hepatocytes, microorganisms or eneyme syatema by microencapsulation in artificial cella. Enevrne Enmneering 1990.10(613):l09-115, in Annals, New York Academy of Sciences. 9. ChangTMS Artificial Cells. In:DulbeccoR, e d . E n c v e l a ~ e d i a o f H u m a n B i o l oSanDiego: ~. AcademicPress, 1991,1:377-83.

10.ChangTMS Recent advances in artificial cells with emphasis on bioteehnological and medical approaches based on microencapaulation. Chapter in "Microcapsules and Nanaparticles in Medicine and Pharmacology' (ed Donbrow M), CRC Press, USA, 1992; pp. 323-339.

11. Chang TMS Biotechnology of artificial cella including application to artificialorgans. In: Moo-YoungM, ed. Com~rehen3lveBiotechnolom: -Principles. applications &Renulationa OfBiotechnolom h l n d u s t r y Apriculture and Medicine. New Yark: Pergamon Press, 1985:53-72.

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1 2 . Chang TMS. Removal ofendogenous and exogenous toxins by a microencapsulated absorbent. Can J Phvsioi Phormacol., 1969,47(12):1043-5. Chang TMS. Nonthrombogenic microcapsules. U.S P a t e n t , 3, 522, 346, 1970 Chang TMS Nonthrombogenic microcapsules. Canadian P a t e n t , 876, 100, 1971. Chang TMS. Blood compatible microcapsules cantainmg detoxicants. U S P a t e n t , 3, 725, 113, 1973 Chang TMS. Blood compatible microcapsules containing detoxicants. Canadian P a t e n t , 982, 941, 1976. Chang TMS Microencapsulated adsorbent hemoperfusion for uremia, intoxication and hepatic failure. Kidnev I n t . 7.S387-S392, 1975.

13.May SW, LI NN. Thecirculation ofureaseue,ngIiquid-surfactunt membranes Biochem. Bioph Res. Comm 1972;47:1179. 14. Gregoriadis F Liposames as d r u g carriers: Recent trends and urogress New York: John Wiley & Sons, 1989. 15. Chang TMS Biodegradable semipermeable microcapsules containing ensymes, hormones, vaccines, and other biologicals J Bioengineering 1976;1:25-32

16. Jalil R, Nixon JR. Biodegradable poly(1actic acid) and poly(1actide-co-glyeolide)microspheres. Microencaps 1990;7.297.

J

17. Mathiowits E,Langer R. "Polyanhydride mieraspheree as drug delivery systems" from"Microeapsu1es and Nanoparticlea in Medicine and Pharmacology" (ed. Danbmw M ) . CRC Press, Boca Raton, USA, 1992, pp. 99-123 18. ChangTMS, Coffey JF,ListerC,Taroy E,Stark A. Methaqualone,methyprylon,a n d glutethimdieclearance by the ACAC microcapsule artificial kidney: i n v i t r o a n d i n patientswith acuteintoxication.TransAmSocArtif Intern Oraans 1973;19:87-91. Chang TMS, Coffey J F , Barre P , Gonda A , Dirks JH,Levy M,Linter G. Microcapsule artificial kidney: treatment of patientB with acute drug Intoxication. Can. Med. Assoc J . 1973;108 429-433 Chang TMS, Espinosa-Melendee E , Francoeur T E , Eade NR. Albumin-collodion activated coated charcoal hemoperfusion in the treatment of severe theophylline intoxication in a 3-year-old patient. Pediatrics 1980;65(4):811-814

19 Winchester J F . Hemoperfusion. I n Maher J F , ed. Replacement of R e n a l Function by Dialysis. Boston: Kluwer Academic PublLsher, 1988:439-50. 20 Chang TMS, Gonda A, Dirks J H , Malave N ClinicalevaluationafEhronie,intermittent,andshort-term hemoperfusions in patients with chronic renal failure using semipermeable microcapsules (artifical cells) formed from membrane-coated activated charcoal. T r a m Am. Soc Artif. Intern Organs 1971;17-246-252. ChangTMS, GondaA,Dirks J H , Coffey J F , Lee-BurnaT ACAC microcapsule artificial kidney for the long term a n d short term management of eleven patients with chronic renalfailure. Trans. Am. Soc.Artif. Intern. 1972;18:465-472. ChangTMS, ChiritoE, B a r r e P , ColeC, HewishM. ClinicalpeformancDeharacteristicecfanewcombined system for simultaneous hemoperfusian-hemodialsys-ultrafiltratio" In eerie.. Trans. Am. Soc Artif. Intern. 1975;21:502-608. Chang TMS Hemoperfusion alone and in aeries with ultrafiltration ordialysisforuremia,poisoningand liver failure Kidnev Int 1976,S305-S311 Chang TMS, Chirito E , Barre P . Cole C , Lister C, Resurreccion E Clinical evaluation of the clearance

profiles of a portable, compact, dialysate-free system incorporating microenapsulnted charcoal hemoperfusion for blood purification with ultrafiltration for fluid removal. J Dialysis 1977,1(3).239-259. Chang TMS. Chirito E , Barre P, Cole C. Lister C , Reaurreecion E Long-term clinical vsaesament of combined ACAC hemoperfusion-ultranltratlan in uremia. Artif. Organs 1979;3(2):127-131 Chung TMS, Barre P , Kuruvilla S , Messier D , Man N, Resurreccion E. Phase one clinical trial of a new composite artificial kidney. A single unit combining dialysis with hemoperfusion. T r a n s Am. Soc Artif. Intern OrKanS 1982,28:43-48. Chang TMS, Barre P , Kuruvilla S. Long-term reduced time hernoperfusran-hemodialyslacompvred to standard dialysis. A preliminary crossover analysie Trans. Am Soc Artif. Intern. O r ~ a n s1985;31:572-576. Bonomini V, Stefoni S, Feliciangeli G , Cali L, Scolari M P , Orst, C , Nanni Costa A, Prandini R, Galanti S Shortened treatment time by combined hernodialysis and hemoperfusion. Contr. Nephrol., 1985;44 57 B o n o m m V . Sefton S, Caseiani CU, Taccone Gallucci M , Albertaeei A , Cappelli P , M i d i V,Mantrangelo F , Rizzelli S. Multicentre experience wlth hemodiulysislhemoperfusionin chronic renal failure Contr. Nephrol. 1982;29.133-142

21

2 2 . Agishi T , Yamashita N. O t a K Clinical results of direct charcoal hemoperfusion for endogenous and oxogenous intoxication, in Hemonerfusian. Kidney and Liver Suuport and Detoxification, P a r t I, Sideman S and Chang TMS, eds., Hemisphere, Washington, D.C., 1980,255-263.

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23,OdakaM,TabataY,KobayashiH,NomuraY, SomaM,HirasawaH,Sato H , S u e n g a E , NobetaK. Three hour maintenance hemodialyaia combining direct hemoperfusion and hemodinlysis. Proc Eur. Dlal. TransDiant. &, 1976;13:257.


2 4 . O t a K , O h t a T , K o b a y a s h i M , Yosh,daS,KanekoI,AgishlT, SugiharaM Petroleum basedactivated charcoal for direct hemoperfusion. Proc. Eur. Dial. Transplant. & 1976;13 250. 2 5 . Bonomini V, Chang TMS, eds. "Hemoperfusion" Contribution to Nepholony, Knrger, London, 148, 1982 Sideman S, ChangTMS, eds. '"Hemoperfusion- I Artificial Kidney and Liver Supnort &Detoxific:ition", Hemisphere Publishing Corp., Washington, D.C., 1980,473 pages. Piskin E , Chang TMS, eds. "Hemoperfusion and Artificial Organs", Artificial Organs Society, 1082;187 pngcs Chang TMS, Ho BL, eds. Hemoperfusion and Artificial Oranns", China Academic Publishers, Beijing, China, 1985;464 pages. Chang TMS, Trevino-Becerra A, eda "Hemoperfusion", Symposxum volume Int. J . Artificial Organs, 1986;9.279-368. Chang TMS, Nicolaev N, eds. "Hemoperfusion. Sorbent and lmmobdieed Bioreactants", Special Symposium volume, Int. J. Biomaterials, Artificial Celle and Artificial Organa, 1987;15.1-321. Klinkmann H, Falkenhagen D , Chang TMS, eds. "Hemoperfusion. Sorbent and Immobilized Bioreactants", Special symposium volume, Biomateriala, Artificial Cells and Immobllwation Biotechnology, 1990;18:455-568 ChangTMS, O d a k a M , eda. "Hemoaerfusion.Sorbent and Immobilized Bioreactants", Special Symposium volume. Bmmateriali, Artificial Cells and Immobilieation Biotechnology, an international journal, 1991;19.1-298 Casciani C, Splendiani G , Chang TMS, eds. "Hemoperfusion, Sorbent and Immobilized Bioreactants", Special Sympasiumvolumes,Biomateriala, Artificial Cells and Immobilieation Biotechnology P a r t 1,1992,this issue; P a r t 2, 1993

Lancet

26 Chsng TMS. Hemoperfusion over microencapsulated adsorbent in a patient with hepatic eomn 1972,ii:1371-2. Chang TMS, MigchelsenM. Characterisation of possib1e"toxic" metabolites in uremia and hepnticcama based an the clearancespeetrumforlnrgermoleeules by the ACAC microcapsule artificial kidney. Trans. Am. Soc Artif. Intern 1973;19:314-319.

_--

a

27 G a u a r d B G , P o r t m a n n B A , WestonMJ,Langley PG,Murray-LyonIM,DunlopEA,FInxH,MeIlonPJ,ReeordC O , Ward MB, Williams R. Charcoal hemoperfusion in the treatment of fulminant hepatic failure. 1974;1:1301. Hughes R, Williams R Clinical experience with charcoal and resm hemoperfusion. Semi" Liver Dis. 1986;6.164.

Lancet

28. Chang TMS, Lister C. Chirito E , O'Keefe P , Resurreccion E. Effects of hemoperfusion rate and time of initiation of ACAC charcoal hemoperfusion on the survival offulminant hepatic failure rats Trans Am Soe Artif Inter Oraans 1978;24:243-5. T a b u t a Y , ChangTMS. Comparisonsofsix artificial liver support regimes)" fulminant hepatic comarats. Trans Am. Sac Artif. Intern. Ornans 1980;26:394-399

29. C h a n s TMS, Barre P . Effect of desferrioxamine o n removal of aluminium and iron by coated charcoal hemoperfusion and hemodialysis. Lancet 1983;Nov:1051-3. Chang TMS, Barre P , Linter C , Kuruvilla S Artificial cells in medical applicatmns with emphasis on hemoperfusion for aluminium removal and C ~ O B B O Ycontrol ~ ~ clinical trial o n hemoperfusion-hemodialysis. Contributions Nephrology 1989;70:237-249. 30.Hakim RM, Schulman J M , Laearus JM. Hemoperfusion in the treatment of aluminum (Al) and iron (Fe)induced bone disease. Abstracts Am. Soe. NeDhrol., 1985;18:65A. 31. ChangTMS. Blood compatiblecoatingofsyntheti=immunoadsorbents T r a n s A m Soe Artif Intern Ornans 1980,26.546-9. 32. Lim

F, S u n AM Microencapsulated islets

8s biovrtificial endocrine pancreas.

1980;210 9C8-909.

33,GoosfnMFA,O'SheaGM,GharapetianHM,Chou S, Sun AM. Optimizntionofmicraencvpsulotionparnmeters Semipermeable microcapsules as a bioartificial pancreas. Biotechnol. Bioeng, 1085.27.146-50.

34.Soon-ShiongP,OtterlieM,Skjak-BmekG,SmidsrodO,HeinteR,LvneaRP,EspevikT. An immunologic bvsia for the fibrotic reaction t o implanted microcapsules. Transpl. P 1901;23:758-59 35. Wong H, Chang TMS. Biaartificial liver: implanted artificial cells mrcroencapsulzted living hepntoeytes increases survival of liver failure ratli. I n t J Artif Orunns 1986;9:335-6.

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36.Wong H, Chang TMS. T h e viability and regeneration ofartificial cell microencapsulated rat hepatocyte xenograft transplants in mice. J Biomat Artif Cells and Artif Oraans 1988;16:731-40. Kashani S.Chang TMS. Physicalchemical characteristics of hepatic Stirnulatory factor prepared fromcell free supernatant of hepatacyte cultures. 3- BiOmaterialS, Artificial Cells and Immobilimtian Biotechnology 1991;19:565-578. Kaahani S, ChangTMS. Effectsofhepatic stimulatory factor released fromfree or microencapsulated hepatocytes on galactoaamine inducedfulminant hepatic failure animal model. JBiamaterials.Artificial Cells and lmmobilimtion Biotechnoloa 1991;19:579-598.


-_

37. Bruni S , Chang TMS. Hepatocytea immobilized by microencapsulation in artificial cells: Effects an hyperbilirubinemia in Gunn Rats. J Biomat Artif Cells and Artif Oraans 1989;17:403-12. Bruni S, Chang TMS. Encapsulated hepatocytes for controlling hyperbilirubinemia in Gunn Rats. Int.J Artificial Oraana 1991;14:239-241.

V, Darvasi R,Arthur M, BreBina M, Lewin K, Gitnick G. Restorationofliver function in Gunn rat8 without immunoauppreasion using transplanted microencapsulated hcpatocytea. HeDatol., 1990;12:1342-49. 38. Dixit

39. Wong H, ChangTMS. A novel two step procedure for immobiliringlivingcells in microcapsuleafor improving xenograft survival. Biomaterials, Artificial Cells and Immobilicing Biotechnoloa 1991;19:687-698. Chang TMS, Wons H . A navel method for cell encapsulation. Patent U.S.A. granted, 1991. WongH, ChangTMS. Microencapsulation of cells within alginate poly-L-lysine microcapsules prepared with standard single step drop technique: Histologically identified membrane imperfectioni and the associated graft rejection. 1_ Biomaterials, Artificial Cells and Immobilifiation Bioteehnology 1991;675-686. 40. Garofala F , Chang TMS. lmmobilirstion of P . pictorum in open pore agar, alginate polylysina-alginate microcapsules for aerum choleiterol depletion. J Biomat. Artif Cella and Artif Organs 1989;17:271-90. Garofalo F , Chang, TMS. Effects of mads transfer and reaction kinetics on serum cholesterol depletion rates of free and immobhsed Pseudomonas pictorum. ADDlied Biochemistry & Bioteehnology 19Q1;27:75-91

41.GaosenMFA,KingGA,McKnightCA,Marcottt,N.Animalcellcultureengineeringus~ngalginatepolycation microcpasules of controlled membrane molecular weight cut-off. Journal of

Membrane

Science 1989;40:233-243.

42. Kjellstrand C , Barges H, Pru C , Guduer D , Fink D. On t h e clinical use of microencapsulated zirconium phosphate urease for treatment of chronic renal failure. Trans. Am. SOC. Artif. Intern. Oraans, 1981;27:24-30 43. Wolfe EA, Chang TMS Orally ingeated microencapsulated urease and an adsorbent, eireonium phosphate, to remove urea in kidney failure. Int. J . Artif. Oraans 1987;10:269-275. CattaneoM, Chang TMS. The potentislofmicroencapsulatedureaae-reolite oral sorbent for the removal of urea in uremia. TASAIO - Official Journal of the American Society of Artificial Internal Organs 1991;37:80-87 44. Chang TMS, Pocnanaky MJ. Semipermeable microcapsules COntainhgcata~aSefor encyme replacement in acatalaaemic mice. Nature 1968;218(5138):242-245. Pornansky M J , ChangTMS. Comparison o f t h e enzyme kinetics and immunological properties ofcatalase immobilimd by microencapsulation and catalase in free solution foreniyme replacement. Biochim. BioDhys. Aeta 1974;334:103-115.

45. Chang TMS. The in vivo effects of semipermeable microcapeulea containing L-asparaginase on 6C3HED lymphosarcoma. Nature 1971;229(528):117-118. ChangTMS. L-Aaparaginaae immobilised within semipermeable microcapsules: In vitro and in vivo atahility. 1973;14(2):96-104. Chong ES, Chang TMS. I n vivo effects of intraperitoneally injected L-asparaginase solution and Lasparaginaseimmobili.ed within semipermeable nylon microcapsules with emphasis on blood L-asparaginse, 'body' L-aaparaginase, and plasma L-wparagine levels. EnEyme 1974;18:218-239. Chong ED, Chang TMS L-Asparaginme as a model for enEyme therapy of substrate-dependentn tumors. "Biomedical Applications ofImmobilir,ed EnEymes and Proteins" (Chang TMS, ed.), Plenum Press, New York, 1977;OO. 105-120. 46. Shu CD, Chang TMS. Tyroiinase immobilired within artificial cells for detoxification in liver failure.

I. Preparation and in vitro Btudiei. Int. J. Artif. Oraans 1980;3(5):287-291. Shu CD, Chanp TMS. Tyrosinwe immobilired within artificial cells for detoxification in liver failure 11. In vivo atudiea in fulminant hepatic failure rats. Int. J. Artif. Oraans 1981;4:82-84. 47 Bourget L, Chang TMS.Phenylalsnina ammonia-lyiue immobiliied in aemipermeable microcapaulesfor enzyme replacement in phenylketonuria. Federation of EuoDean Biochemical Societies (FEBS Letters) 1985;1805-8. Bourget L, ChangTMS. Phenylalanine ammonia-lysse immobilised in microcapsuleafor the depletureof phenylalanine in plasma in phenylketanuric rat modal. Biochim. BioDhys. Acta. 1986;883:432-438. Bourget L, Chsng TMS. Effects of oral administration of artificial cells immobilieed phenylalanine ammonia-lysse on inteatinal amino acids of phenylketonuric rats. J . Biomat. Art. Cells and Art. Oraans 1989;17:161-181.

CHANG

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48.K h a n n a R , Chang TMS Charaeterieatian ofL-histidine ammonia-lyase immobiliced by microencapsulation In artificial cells Preparation kinetics, stabiiity, and in vitro depietion of histidine. Int. J . Art. Or& 1990;13.189-195.


49.Chang TMS Preparation and characterization ofxanthine oxidase immobdized by microencapsulation in artificial cells for the removal of hypoxanthine. J Biomat, Artif Cells and Artif Oranns 1989;17.611-16 PalmaurRM, Goodyer P , R e a d e T , ChangTMS Microencapsulatedxanthine oxidase as experimental therapy Lesch-Nyhm Disease. Lancet 1989,2(8664).687-8

In

50 Wang XL, Shno

JY. An approach to t h e preparation of digestive enzyme-drug for oral admrnirtration' Complex lactaw microcapsules Acta Academiae Medicinae Sinicae 1991,13.435-438. 51. Chang TMS, Lister C. Plnsma/lntestinal concentration patterns suggestive of entero-portal recirculation of amino acids. Effects of oral administration of asparaginase, glutaminaae and tyrosinase immobilized by microencapsulation in artificial cells. J Biomat, Artif Cells and Artif Oraans 1988/89;16:915-26. Chang TMS, Bourget L, Lister C . US patent granted, 1992.

5Z.CampbellJ. ChanaTMS. Eneymaticreeyelingofcoenzymea by amulti-enzymesystem immobilieedwulthm semipermeable collodion microcapsules Biochim. Biophvs Acta 1975;397.101-109. Cousrneau J , Chang TMS. Formation ofamino acid from urea and ammonia by sequential enzyme reaction using a microencapsulated multieneyme system. Biochem. Bio h B Res Commun. 1977;79(1):24-31. Grunwnld J, Chang TMS. Continuous recycling of N A D f g ; immobilieed system of collodion microcvpsulescontainingdextran-NAD', alcoholdehydrogenase, and rnalicdehydrogenase. J. Applied Biochem 1979;1:104-114. ChangTMS, Malouf C. EffectaofglucosedehydrogenaseIn convertingurea and ammonia into amino acid uaing artificial cells. A d f Or ans 1979,5(1)~38-41 Grunwald J , Chang T M k m o b i l i e a t i o nof alcohol dehydrogenase, maiic dehydrogenase and dextran-NAD' within nylon-polyethyleneimine microcapsules: Preparation and eofactor recyling. J. Molecular Catalysis 1981;11.83-90 Wahl IIP, ChangTMS. Recyclmgaf NAD' cross-linked to albumin orhemoglobin immobilized with multienzyme systems In artificial cells. J . of Molecular Catalysis 1986;39.147-154. Chang TMS Recycling of NAD(P) by multienzyme systems immobilized by microencapsulation in artificial ceils. Methods in Enevmoloay 1987.136:67-82. 53. Gu KF. Chang TMS Conversion of ammonia or urea into L-leucine, L-vsline, and L - i d e u c i n e using I. Glucose dehydrogenase for cofsctor artificial cell immobilizing multieneyme ayatem and dextran-NADH'. recycling. ASAIO - Official J Am Soc Artif Intern Orruns 1988,11:24-8. G u K F , ChangTMS. Conversionof -ketoglutarateinto L-glutamic acid withureaas ammoniumsource using multieneymesystemanddextran-NAD' immobilized by microencapsulation with artificial cells in a bioreactor. J Bioena. Biotech. 1088,32.363-368. G u K F , ChangTMS. Production ofessential L-branched-chained amino acida, in biareactors containing artificial cells immobilized multienzyme systems and dextrun-NAD'. Applied Bioehemistrv a&Biotechnolocry 1090;26%3-269. 54. D a k a J N , Chang TMS. Bilirubin removal by thepseudoperoxidase activity offree andimmobilimd hemoglobin and hemoglobin eo-immobilized w t h glucose oxidase. J Biomat, Artif Cells and Artif Oraana 1989;17:553-62. ChangTMS, D a k a J N . Removal of bilirubin by the pseudoperoxidase activityofimmobrlieedhemoglobin U.S. Patent No. 4820416,1989. 5 5 . Chang TMS. Geyer R , eda. Blood mbstitutes. New Yark. Marcel Dekker

Publisher, 1988.

Chang TMS, Geyer R , eds Blood substitutes. 3 Biomateriala, Artificial Cells a n d Artificid Organs

1989;16:1-704. 56 Chang TMS, ed. Blood Substitutes and Oxvaen Carriers. New York. Marcel Dekker Publisher, 1992. Chang TMS (ed.). Blood Substitutes and Oxygen Carriers. J Biomateriala, Artificial Cells and Immobilization Biotechnolopy, 1992,ZO154-941 57. Chang TMS, Lister C A screening test of modified hemoglobin blood substitute before clinical use in patients - based on complement activation of human plasma. J Biomet, Artif Cells and Artif Organs 1990;1a(~)-6~3-702. Chang TMS, Lister C. An in-wtro screening test for modified hemoglobin to bridge the g a p between animal safety studies and clinical use in patients. J Biomaterials, Artificial Cells and Immobiliration Bioteehnolom 1992;20:481-487.

E from polylactic acid and microcapsules, microparticlee and modified microparticles. L M m a e n a e . , 198815.27-32. ZhouMX, ChangTMS. Effect ofpolyactic acid microcapsulescontainingproataglandin E onthesurvival rates of grade I1 galactosamine-induced fulminant heaptic failure rati. J Biomat. Art. %lls. and Art. 1987;15:549-558. 5 8 . Zhou MX, Chang TMS. Control release of prostaglandin


1143


59 Ike 0 . Hitoni, Shimiqu Y et al. Administration of adriamycin containing poly(lactic acid) microspheres into the pleural cavity of patients with malignant pleural effusion Drur Delivery System 1990;5.23. 60. Chang TMS. Lipid coated spherical ultrathin membranes of polymer or cross-linked protein as possible cell membrane model. Fed Proc. Fed. Am. Soc E x p B i d . , 1969;28:461. Rosenthal AM, Chang TMS The incorporation of lipid and Na+-K+-ATPase into the membranes of semipermeable microcapsules. J. Membrane Science 1980,6(3).329-338. Y u YT, Chang TMS Lipid-polymer membrane artificial eella containing multieneyme systems. cofsctors and substrates for the removal of ammonia and urea. Trans. Am. Sac Artif. I n t e r n . Orcans 1981,27535-538 Y u YT, Chang TMS. Immobilization of multreneymes and cafactors within lipid-polyamide membrane microcapsules for the multistep conversion oflipophilic and lipophobie substrates. Enevrne M m o b . Technol. 1982,4.327-331. llan E , Chang TMS Modification of lipid-polyamide microcapsules for immobilization offreecofactors and multieneymesysternfor thecanversion ofammonia toglutamate. Annlied Biochemistry& Biotechnolou 1986;13:221-230. 61. Chang TMS. The one shot vaccine. "Soeio-Economic and Ethical Implications of Enryme Engineering" (Heden CG, ed ), International Federation oflnetitutes for Advanced Studies, Stockholm, Sweden, 1975;pp.17-18.

R,Bannard RAB, Chang TMS. Adaorption of large lipophilic molecules with exclusion ofemall hydrophilic molecules by microencapsulated activated charcoal formed by coating with polyethylene membrane Journal of Membrane Science 1986;29:277-286. Sipehia R , Bannard RAB, ChangTMS. Poly(vinyhdene fluoride) o r paly(wny1idene chloride/vinyl chloride) - coated activated charcoal for the adsorption oflarge lipophilic molecules with exclusion of small hydorphilic molecules J. Membrane Science 1989,47.293-301 6 2 . Sipehia

63. Yuan ZY,Chang TMS. Rat rnicrosomea and cytosol immobrlired by microencapsulation m artificial cells Int. J. Artif. 1986;9(1).63-68. 64. Spirin A.S. "Cell free protein synthesis bioreactor" from Frontier. in Bioprocessin< SK and Bier M ) , 1991

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