The preparation of the chronic hyper-endotoxemia experimental animal model by means of a drug delivery system

A drug delivery system (DDS) consisting of lipopolysaccharide (LPS) as a drug and 2-hydroxyethyl methacrylate (HEMA)-diethylene glycol dimethacrylate (2G) or -polyethylene glycol dimethacrylate (4G, 9G) copolymer was prepared, and used for the efficient preparation of an experimental animal model of chronic hyper-endotoxemia. The release profiles of LPS in the in-vitro test were greatly influenced by the composition of HEMA-2G, 4G, 9G in the copolymer. It was found that LPS release from the DDS continued gradually and constantly throughout 2 weeks. In the in-vivo experiment with rats, the DDS maintained a high blood concentration level of LPS for 3 days. These results strongly suggest the possibility of convenient and reproducible preparation of a chronic hyper-endotoxemia animal model.

[Prolonged antinociceptive effect of poly (DL-lactic acid)-fentanyl composites after their intrathecal injection in rats]

We synthesized poly (DL-lactic acid)-fentanyl composites and compared the duration of analgesia after the administration of a single intrathecal dose of these agents in rats. The drug was injected with an intrathecal catheter into the intrathecal space. Fentanyl composites or plain fentanyl in doses of 2.5 or 25 micrograms were administered, respectively. Animals were then tested for analgesia using the tail-flick test. The release rate of fentanyl from fentanyl composites in vitro was also evaluated. The antinociceptive effect of fentanyl composites (25 micrograms) was significantly longer than that of plain fentanyl. Administration of poly (DL-lactic acid) alone did not induce the antinociceptive effect. Four of 7 animals given plain fentanyl (25 micrograms) exhibited temporary respiratory depression, but none of the animals given fentanyl composites showed this response. In vitro experiments demonstrated a slow release of fentanyl from the fentanyl composites. We conclude that the antinociceptive effect of fentanyl can be prolonged when administered as a poly (DL-lactic acid)-fentanyl composite in the intrathecal space with decreased systemic side effects compared with the plain formulation.

Ipsilateral dominance of human olfactory activated centers estimated from event-related magnetic fields measured by 122-channel whole-head neuromagnetometer using odorant stimuli synchronized with respirations

The aim of this study was to measure and analyze olfactory event-related magnetic fields using a whole-cortex biomagnetometer (122-channel SQUID gradiometer). Amyl-acetate gas (approx. 1%) was administered for 300 msec into either the right or left nostril in synchronization with respiration using a mask and an optical fiber sensor. Clear olfactory event-related magnetic fields were asymmetrically obtained on both sides of the forehead in all six subjects. The generators of olfactory magnetic fields were estimated at two regions located fairly asymmetrivally near the bilateral frontal deep areas. The goodness-of-fit was better for the two-dipole model than the one-dipole model in all experiments. In almost all subjects the latency and intensity of ipsilateral olfactory magnetoencephalography (MEG) responses were shorter and larger than those of the contralateral responses, respectively. These results suggest that the olfactory MEG responses on the ipsilateral side are generally larger and more dominant than those on the contralateral side in the human olfactory system.

[Prolonged antinociceptive effect after epidural injection of polyethylene glycol-morphine composites in rats]

Epidurally administered morphine is useful in the management of postoperative or cancer pain, and a reliable method which can produce prolongation of analgesia with a single dose may be very useful. We synthesized a polyethylene glycol-morphine (PEG-morphine) composites and examined the duration of analgesia after a single epidural administration dose of this agent in the rat. The molecular weight of PEG was functionally evaluated. PEG-morphine was injected surgically along the epidural space. Morphine in doses of 2.5, 5.0 and 7.5 mg and PEG only were administered. A second group of animals received intramuscular injections of PEG-morphine (5.0mg). Animals were then tested for analgesia using the tail-flick test. The antinociceptive effect of 7.5mg was significantly longer than that of 2.5mg or 5.0mg. Neither PEG alone nor intramuscular administration of PEG-morphine induced antinociceptive effect. Sensory blockade was reversible and the animal appeared to have normal sensory perception. We conclude that the antinociceptive effect of morphine is dose-dependent and its duration can be prolonged when administered as a PEG-morphine composite in the epidural space.

Interstitial chemotherapy with biodegradable ACNU pellet for glioblastoma

For patients with nonresectable glioblastoma (GB) or recurrent GB, we have recently been using an interstitial chemotherapy with biodegradable polylactic acid pellets containing nimustine chloride (ACNU), in combination with superselective arterial ACNU injection, routine irradiation and chemotherapy. The ACNU pellets are prepared by mixing polylactic acid powder and ACNU, and then melting the mixture at low temperature and moulding it into a thin pellet. Pharmacological anticancer activity was experimentally demonstrated by the finding that a region of suppression was present surrounding an ACNU pellet placed in a B6 melanoma cell culture disc, but that no such suppression was present around a control pellet. In order to determine the spatial and temporal distribution of ACNU, a small pellet (ACNU: 0.6 mg) was implanted in the frontal lobe of rats. ACNU concentration determined by HPLC was 61.0 micrograms/g brain tissue on day 1. 22.5 on day 3, and 5.5 on day 7; small amounts of ACNU were in fact released for at least 4 weeks after implantation. This pellet was used for the clinical treatment of 11 GB patients. Four patients had several pieces of pellets implanted immediately after CT-guided stereotactic biopsy, and the other 7 had pellets placed in residual tumor after partial removal at craniotomy. No ACNU was detectable in serum. CT studies obtained at subsequent appropriate intervals disclosed gas formation around the pellets, a slight increase in edema, and necrosis or decrease in CT enhancement of tumor beginning around day 12 after implantation. Bone marrow suppression did not occur, since ACNU was administered interstitially and in the range of 50-200 mg (average: 126 mg) per patient.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo release of cisplatin from a needle-type copolymer formulation implanted in rat kidney

Cisplatin, cis-dichlorodiamine platinum (II), was incorporated in a needle-type copolymer formulation (0.8 mm diameter, 6 mm long) by radiation-induced polymerization. The copolymer used was copoly(diethylene glycol dimethacrylate/polyethylene glycol #600 dimethacrylate, 80/20 vol%). This copolymer, containing 6 mg of cisplatin, was implanted into the kidney of adult male Wistar rats (420 +/- 20 g). A total of 70 d was required for 100% release of cisplatin in vivo. The kidney tissue surrounding the formulation was strongly necrotized by the action of cisplatin. Two layers of necrosis could be distinguished: necrotic tissue surrounding the formulation and necrobiotic tissue surrounding the necrotic tissue. The amount of necrotic tissue changed markedly over time, but no change was apparent in the amount of necrobiotic tissue. The maximal amounts of necrotized tissue were observed 14 d after implantation: 3100 microns and 600 microns thick for the necrotic and necrobiotic tissues, respectively.

Studies of the slow releasing of testosterone from radiation-polymerized testicular prostheses implanted subcutaneously in the back of castrated rabbits

A controlled release testicular prosthesis containing testosterone, which was previously dissolved in 2-hydroxyethyl methacrylate (HEMA) at a temperature of 80 degrees C, was prepared by radiation-induced polymerization in the supercooled state at a low temperature. The daily dose of testosterone released in vitro from the poly(HEMA) testicular prosthesis was kept constant at a rate of 5.5 +/- 1.5 mg/d throughout an experimental period of 900 d. In the in vivo experiments, the poly(HEMA) testicular prosthesis was implanted subcutaneously in the back of castrated rabbits over a maximum period of 11 mnth. The cumulative amounts of testosterone released in vitro and in vivo from the poly(HEMA) testicular prosthesis for a period of 11 mnth were found to be 2.1 g (30.0 wt% of initial drug) and 0.9 g (12.8 wt% of initial drug), respectively. The serum testosterone level in castrated rabbits with a poly(HEMA) testicular prosthesis rapidly decreased for periods up to 2 mnth (after increasing during the first 2 wk), then showed a moderate decrease for a few months, and finally held constant at a level of 10 ng/ml throughout the experimental period. It was concluded that a slight amount of testosterone is continuously released in vivo from the radiation-polymerized poly(HEMA) testicular prosthesis over a long period analogous with that in vitro.

[Treatment of malignant brain tumors with slowly releasing anticancer drug-polymer composites]

The purpose of this study is to present the methodology and results of a clinical trial of local chemotherapy of malignant brain tumors based on slowly-releasing anticancer drug-polymer composites. The slowly releasing drugs were prepared by combining and mutually dispersing anticancer agents with glassified monomers containing 10% polymetacrylic methyl acid and then this compound was frozen at -78 degrees C and exposed to 1 X 10(6) rad of gamma rays from cobalt 60. Thus we prepared a compound of polymers and anticancer agents. We used needle-shaped capsules of this compound. These capsules release the drug very slowly over 40 days. We administered locally to the malignant brain tumors with either slowly releasing mitomycin, slowly releasing adriamycin, slowly releasing ACNU or slowly releasing 5 Fu drugs. The following techniques were employed in implantation these capsules. Implantation into the remaining tumor wall at the time of excision. Implantation into the tumor by CT-guided stereotactic method. We implanted these drugs into tumor of 55 cases, thereafter we conducted both radiation and chemotherapy with ACNU in most patients. This method has the following advantages: It is possible to be employed to different types of anticancer agents. Both dosage and releasing time can be adjusted. It is possible to administer these capsules postoperatively by the stereotactic method. The clinical study consists of 55 patients, 20 cases of anaplastic astrocytoma, 23 cases of glioblastoma multiforme, 5 cases of oligodendroglioma, 3 cases of medulloblastoma and 4 cases of others. Survival rate estimated by Kaplan-Meier method was 47% in glioblastoma at 12 months and 91% in anaplastic astrocytoma at 18 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of drug-vinyl copolymer delivery composites on the rat prostate

A radiation polymerized drug-vinyl copolymer delivery composite (0.8 mm in diameter, 3 mm long) was inserted into the right-lobe ventral prostate (I), into the right testis (II), and subcutaneously (III) into the back of male Wistar rats. The implantation was carried out over a period of 12 weeks maximum. From the relationship between the site of surgical insertion of the implant and the physiologic response (as measured by the decrease in the weight of the prostatic organs, e.g., ventral prostates, dorsolateral prostates, and seminal vesicles), it was found that in an AA560-containing composite (36 micrograms daily), the physiologic response is increased in order of (III) greater than (II) greater than (I). The same tendency was observed in the Estracyt-containing composite system (15 micrograms daily). The difference in the physiologic response owing to the site of surgical insertion of the implant was not observed in an E2-17 beta-containing composite (6 micrograms daily), although this composite showed the strongest physiologic response. No physiologic response in rats with CMA-containing composite (28 micrograms daily) was noted.

Sheets obtained by radiation polymerization for enzyme immunoassay

Immobilized anti-alpha-fetoprotein sheets, which were attached to sticks, for enzyme immunoassay of alpha-fetoprotein were prepared by radiation polymerization of hydrophilic monomers. The relationship between the preparation conditions and the activity of the sheets was studied. The activity varied with monomer concentration, hydrophilicity of polymer matrix, the amount of coating solution, and antibody concentration. The sheets obtained at relatively low monomer and antibody concentrations appeared to give a high activity. It was found that the sheets are applicable for the enzyme immunoassay of alpha-fetoprotein with high sensitivity.

Preparation by irradiation of a solid support for enzyme immunoassay

Reagents (immobilized anti-alpha-fetoprotein discs) having a porous structure were prepared for enzyme immunoassay of alpha-fetoprotein by radiation polymerization at low temperatures. Discs were attached to sticks for easy handling. The activity (determined by absorbance at 492 nm) of the discs varied with the hydrophilic properties and size of the disc. The discs are sufficiently sensitive and precise for enzyme immunoassay of alpha-fetoprotein.

Immobilization of enzymes masks their active site

We studied the effect of immobilizing cellulase to carboxycellulose sodium by radiation polymerization on the masking of the active site of the enzyme. Masking of the enzyme during the preparation of immobilized enzyme was assayed at low temperature. The activity of immobilized enzyme was retained during repeated batch reactions, indicating that the enzyme was firmly trapped in the polymer matrix. Various compounds (designated monomers) were used to dissolve the carboxymethylcellulose; enzyme activity was affected by the nature of the monomer, by the monomer concentration, and by the solubility of the substrate in monomer.

Behavior of enzyme activity in immobilized proteases

Proteases such as trypsin, alpha-chymotrypsin, papain, and thermolysin were immobilized by radiation polymerization of various monomers at low temperatures, and behavior of enzyme activity in immobilized proteases was studied. The enzyme activity in immobilized proteases appeared to be different by the kind of proteases; the order of the magnitude of the enzyme activity was papain greater than trypsin greater than thermolysin greater than alpha-chymotrypsin. This difference of the enzyme activity was explained by the change of the molecular conformation in enzyme reaction.

Polymeric microspheres for immunoresearch

New microspheres having functional aldehyde groups have been prepared by radiation polymerization of acrolein solution containing hydroxyethyl methacrylate and glutalardehyde. The size distribution in the microspheres was narrow and average particle diameter was 1 - 2 micron. The binding ability of the microspheres to antigen increased by increasing the concentration of glutalardehyde. The preparation procedure of the microspheres is simple. The microspheres can be used for immunoresearch.

Cell culture on polymers prepared by radiation-induced grafting of various monomers

The adhesion and growth of tissue cells on polymers prepared by radiation grafting was investigated. The apparent rates of initial attachment and growth of Chang liver and C6 cells were promoted on surfaces with increased wettability and with a heterogeneous structure for grafted polyvinyl fluoride film. The degree of cell attachment and growth on surfaces having a dense microblock structure, formed by grafting of methyl methacrylate in acetone solvent, was greater than that caused by other factors, such as wettability.

Polyacrolein microspheres as immunoreagents

Polyacrolein microspheres were prepared by radiation polymerization of acrolein in the absence of emulsifying or stabilizing agent. The microspheres had functional surface aldehyde groups permitting covalent binding with antibody in 1 step. The particle size of the microspheres varied with polymerization conditions, especially irradiation temperature. The microsphere antibody conjugates obtained by binding immunoglobulins to polyacrolein microspheres were used to label cells. The reactivity of microsphere antibody conjugates was shown by specific aggregation by antigen.

Immobilization of E. coli cell as an antigen by radiation polymerization method

E. coli NIJ cells were immobilized by radiation polymerization of 2-hydroxyethyl methacrylate at low temperatures. The immobilized E. coli cells as an antigen were reacted with peroxidase labeled anti-E. coli in competition with the free E. coli cells. It was found that E. coli cells can be assayed quantitatively with the immobilized E. coli cells in disc form. Microorganisms such as gram negative bacteria had no specific affinity to anti-E. coli. Cross reactivity of the immobilized E. coli cells with the E. coli cells from various strains was examined.

Polymer cellulose sheets immobilizing antibody by radiation polymerization

Antibody such as anti-alpha-fetoprotein was immobilized on cellulose fibril sheets by radiation polymerization of hydrophilic monomers. The nature of the immobilized anti-alpha-fetoprotein sheets was examined by measuring the enzyme activity in an antibody-antigen complex reaction. The relationship between the activity and the polymerization condition was studied. The degree of hydration of the polymer matrix giving a maximum activity appeared to be about 0.2. The activity varied with monomer concentration and with monomer composition in copolymerization of acrylate and diacrylate monomer. The activity was increased by the addition of polyethylene glycol diacrylate monomers, in which the activity increased with increasing length of the oxyethylene unit chain.

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization

Immobilization of antibodies and enzyme-labeled antibodies by radiation polymerization at low temperatures was studied. The antibody activity of antibody was not affected by irradiation at an irradiation dose of below 8 MR and low temperatures. Immobilization of peroxidase-labeled anti-rabbit IgG goat IgG, anti-peroxidase, peroxidase, and anti-alpha-fetoprotein was carried out with hydrophilic and hydrophobic monomers. The activity of the immobilized enzyme-labeled antibody membranes varied with the thickness of the membranes and increased with decreasing membrane thickness. The activity of the immobilized antibody particles was varied by particle size. Immobilized anti-alpha-fetoprotein particles and membranes can be used for the assay of alpha-fetoprotein by the antigen-antibody reaction, such as a solid-phase sandwich method with high sensitivity.

Cell culture on polymers prepared by radiation-induced polymerization of various glass-forming monomers

The growth of cells on polymers prepared by the radiation polymerization of monomethacrylate and dimethacrylate was investigated. Cell growth was affected greatly by such properties of the polymers as water content, wettability, and porosity. Growth was promoted remarkably by rinsing the polymers with warm water at 60-70 degrees C and by irradiation of polymers with an electron beam. Cell growth decreased with increasing oxyethylene length (n) in the polymerized dimethacrylate of same series, CH2C(CH3)CO(OCH2CH2)nOCOC(CH3)CH2. A decrease in the hydrophilicity of the polymer increased cell growth rate. Formation of pore structures in the polymer films also increased the cell growth.

In vivo release of testosterone from vinyl polymer composites prepared by radiation-induced polymerization

Polymer-testosterone composites with long periods of controlled slow release were made by radiation-induced polymerization in a supercooled state at low temperature using glass-forming monomers. The in vitro release of testosterone from various vinyl polymer composites was found to follow a matrix-controlled process (Q-t1/2). The rate of drug delivery was accelerated with increasing water content of polymers. In experiments in vivo, the composites were implanted subcutaneously in the back of castrated rats during the 30 day test period. The in vivo release rate of testosterone was a little smaller than in vitro. This difference between two releases also increased with the increase of hydrophilicity of polymer. The physiological response in rats was investigated by measuring the weight of ventral prostate and serum testosterone concentration with testosterone-containing composites. The weight of ventral prostate increased linearly with increasing rate of drug release and the serum testosterone concentration could be correlated with the release and with the weight increase of ventral prostate. It was found from microscopic observation that the used polymer carriers had relatively good biocompatibility to cause little foreign body reaction.

Effect of water soluble polymer, polyethyleneglycol, and glass-forming compounds on cell fusion

The cell fusion of Molt T-cells was investigated in the presence of water soluble polymer, polyethyleneglycol (PEG) and glass-forming monomers. In cell fusion with PEG only, inactivation of the cell occurred within 2 min. However, in the presence of PEG and water soluble polymer, most of the fused and unfused cells lived even after fusion times of more than 10 min. It was observed that water soluble polymer prevented the inactivation of cells during fusion as a protectant. As the result, ratio of fused cells increased in the presence of water soluble polymers. Some glass-forming monomers used as new fusogens such as M-23G (n = 23) and M-50G (n = 50) monomers having long oxyethylene chains in the methoxypolyethyleneglycol methacrylate, CH3O-(-CH2CH2-O)n-CO-C(CH3) = CH2 as well as PEG #2000 indicated large promoting and protecting effects on cell fusion.

In vivo release of testosterone from protein--vinyl polymer composites

Hydrophilic vinyl polymer-protein composites containing testosterone were made by means of thermal denaturation of albumin after radiation-induced polymerization of 2-hydroxyethylmethacrylate (HEMA) at--78 degrees C. The albumin-HEMA mixed polymer can be considerably digested with trypsin. The degree of digestion was smaller than that expected from calculation. It was deduced that the digestion of the albumin component was retarded in the presence of HEMA. The same tendency was observed in in vivo experiments. At the same time, in vivo release of testosterone was depressed in albumin-HEMA mixed polymer composite in accordance with the weight decrease of polymer composite resulting from digestion. The effect of testosterone on the weight of ventral prostate was investigated using composites in castrated Wistar rats. The effect was larger in the controlled slow release from implanted composites rather than that of dosage by injection. The microscopic observation showed that the inflammation and foreign body reaction in rat tissue were retarded in albumin-HEMA mixture polymer composite compared with 100% albumin composite.

Immobilization of yeast cells by radiation-induced polymerization

Radiation-induced polymerization method was applied to the immobolization of yeast cells. The effects of irradiation, cooling and monomer, which are necessary for polymerization, were recovered completely bu subsequent aerobic incubation of yeast cells. The ethanol productive in immobilized yeast cells increased with the increase of aerobic incubation period. The growth of yeast cells in immobilized yeast cell was indicated. The maximum ethanol productivity in immobilized yeast cell system was around three times as much as that in free yeast cell system.

Immobilization of erythrocytes by radiation polymerization of glass-forming monomers at low temperatures

The immobilization of erythrocyte as the whole cell without hemolysis was studied. It found that erythrocyte could be treated and immobilized stably by radiation polymerization of specific monomers having high viscous and long oxyethylene units chain such as methoxypolyethyleneglycol methacrylate (M-23G) and polyethyleneglycol dimethacrylate (14G). Irradiation dose without hemolysis was limited less than 1 X 10(5) r and a comonomer system consisting of M-23 G-14G, 1:1 and small quantity of glutaraldehyde (GA) was the optimum carrier composition. The functional properties of the immobilized erythrocyte was also investigated. It was found that the immobilized cell could be carried out carbon monoxide-oxygen gas exchange effectively and reversibly so as in the intact cell. The immobilized erythrocyte also showed the catalase activity just as in the intact cell. The stability of erythrocyte increased greatly by the immobilization for standing at low and room temperatures and hardly hemolyzed in non-isotonic medium such as pure water. It was observed in scanning electron microscope that the immobilized erythrocyte had a hollow disk shape same as in intact cell and covered with a thin polymer layer.

Stabilization of Photosystem II (O(2) Evolution) of Spinach Chloroplasts by Radiation-induced Immobilization

Spinach chloroplasts were immobilized with vinyl monomers by radiation-induced polymerization at low temperature and stored in buffer containing bovine serum albumin. The lifetime of O(2) evolution activity in photosystem II was prolonged remarkably in immobilized chloroplasts. Thermostability of immobilized chloroplasts stored in buffer containing bovine serum albumin was far better than that of immobilized chloroplasts in pure buffer and that of intact chloroplasts. When immobilized chloroplasts were stored in buffer including polyethylene glycol, the lifetime of O(2) evolution activity was longer than for those stored in buffer containing bovine serum albumin.

Effect of Viscous Solvents and Monomer on Conservation of Intact and Immobilized Chloroplasts

O2 evolution activity of PS II in chloroplast stored in buffer including various supercooling solvents was studied. Viscous solvents such as polyethylene glycol (PEG) was remarkably effective for the increase of lifetime of intact chloroplast. Lifetime of immobilized chloroplast by means of radiation polymerization was prolonged more than 40 days in buffer including PEG 70% (v/v). It was found that viscous solvents having PEG units in molecular chain were effective and methoxypolyethyleneglycol methacrylate monomer (M-23G) was most suitable as a im­mobilization carrier. The immobilized chloroplast with M-23G retained the high activity yield more than 30 days in buffer including PEG.

Effect of Irradiation and Immobilization on Spinach Chloroplast Activities

The effect of y-ray irradiation and immobilization by means of radiation polymerization on PS II activity (O2 evolution) of isolated chloroplasts from spinach was investigated. Reduction of O2 evolution activity by irradiation was small at lower temperatures below – 24 °C, but the activity decreased slightly by freezing at extremely low temperature below –78 °C. So the optimum low temperature range for the treatment was observed. The immobilized chloroplast in a hydrophilic polymer matrix showed the stable duration of O2 evolution activity more than 700 h at 4 °C . Thermo-stability of chloroplast was also improved greatly by immobilization. The active center of PS II in immobilized chloroplasts was retained even after 60 min standing at 50 °C.

Immobilization of enzymes for medical uses on plastic surfaces by radiation-induced polymerization at low temperatures

The immobilization of some medically useful enzymes were studied by means of radiation-induced polymerization at -78 degrees C. Glucose oxidase and glucose peroxidase were immobilized in the form of thin membranes inside polyvinyl chloride tubes and on polyethylene films; these membranes showed considerable activity yield, as well as good activity retention. Two effective methods were adopted to improve the surface properties of the base materials and to facilitate firm immobilization by coating: that is, an undercoating method followed by radiation curing of the undercoating and an irradiation grafting method with a monomer. Both were tested with good results. An immobilization of urokinase was also carried out successfully by similar methods. The thrombogenicity of the immobilized urokinase showed a remarkable effect on thombus formation.

Controlled slow release of chemotherapeutic drugs for cancer from matrices prepared by radiation polymerization at low temperatures

The vinyl polymer-chemotherapeutic agent composites of various shapes (rod, tablet, membrane, microsphere, and powder) were prepared by radiation polymerization at low temperatures for the purpose of durable controlled slow release of drugs from implanted matrices. Bleomycin hydrochloric acid, mitomycin C, and 5-fluorouracil were tested as chemotherapeutic drugs entrapped in poly(diethylene glycol dimethacrylate) including a small quantity of a polymer such as poly(styrene), poly(vinyl formal), poly(vinyl acetate), poly(methyl methacrylate) on polyethylene glycol No. 600. The release rates from the matrices depended much on the kind of polymer, drug, and monomer concentration in polymerization and also on the shape of the composite. The release of these drugs from polymer matrices obeyed the diffusion-controlled release mechanism based on Higuchi's equation and was durable for more than thirty days. It was found that the release rate can be controlled easily by design of the shapes and structures of the polymer matrices.

Controlled release of multi-component cytotoxic agents from radiation polymerized composites

Multi-component cytotoxic (anticancer) agents such as mitomycin C (MMC), adryamycin (ADM) and 1-(2-tetrahydrofuryl-5-fluorouracil) (FT-207), were entrapped in a single common composite by radiation-induced polymerization of glass-forming monomers in the presence of polymers. The release profiles of each cytotoxic agent were controlled by the contents and compositions of three cytotoxic agents in the matrix. The release rates of each cytotoxic agent were retarded by addition of an adsorbent and accelerated by addition of a pore-making agent. The release fom the common matrix of a cytotoxic agent and its promoter which have markedly different molecular weights [e.g. MMC and urokinase (UK)] was also investigated. A double entrapping method was successfully used for controlled release in such cases. In conclusion it was found that the release profiles of multi-components in a single matrix could be controlled by using these techniques.

Controlled drug dissolution by radiation-induced polymerization in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer or methacrylic acid-methyl acrylate copolymer

Polymer-containing tablet preparation was studied using radiation-induced polymerization of glass-forming monomers at low temperatures in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer or methyl acrylate-methacrylic acid copolymer. Drug dissolution from tablets was in the pH 3.0-8.0 range. A copolymer contained in the tablets dissolved in the dissolution medium at a specific pH. Drug dissolution from tablets took place rapidly at pH greater than 6.0 in the presence of methyl acrylate-methacrylic acid copolymer and at pH less than 5.0 in the presence of dimethylaminoethyl methacrylate-methyl methacrylate copolymer. The polymers had fibrous or capillary pore structures in contrast to the spherical pore structures formed in the presence of polyethylene glycol 600.

Enzyme immobilization by radiation-induced polymerization of hydrophobic glass-forming monomers at low temperatures

Enzyme immobilization was studied by means of radiation-induced polymerization of hydrophobic glass-forming monomers at low temperatures. The polymerized hydrophobic composite was generally obtained in microspheric form. Enzymatic activity showed little decrease with repeated use in these systems. The particle size of the microsphere increased with increasing monomer concentration, and activity yield had a maximum at an optimum monomer concentration. Immobilization by copolymerization of hydrophilic and hydrophobic comonomers was also investigated and a maximum activity yield was found at a certain monomer concentration. A model scheme for immobilization at low temperatures was proposed and discussed.

Enzyme immobilization by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperatures

Enzyme immobilization by radiation-induced polymerization of hydrophilic glass-forming monomers, such as 2-hydroxyethyl methacrylate, was studied. Enzyme radiation damage could be sufficiently retarded at low temperatures. The immobilized enzyme activity yield was markedly higher at low temperature than at higher temperature polymerization. At low temperatures the polymerized composite had a porous structure owing to ice crystallization which depends on the monomer concentration. It was deduced that the enzyme was partially trapped on the polymer surface, partially isolated in the pore, and partially occluded inside the polymer matrix. A decrease in activity caused by enzyme leakage was observed with repeated use in enzyme reactions where the composites had a large porosity. The activity yield showed a maximum at certain optimum porosities, i.e., at optimum monomer concentrations. Continuous enzyme reaction was preferably carried out using immobilized enzyme columns.