Polyacrylonitrile membrane interposition between a xenograft and a patient in fulminant liver failure: the concept of xenohemodiafiltration in clinical practice

Fulminant hepatic failure is an important cause of morbidity and mortality in intensive care units. Conventional therapies are not sufficiently effective. Liver transplantation may be life saving, but a "bridge therapy" is needed until transplantation is performed. Hepatic extracorporeal xenohemodiafiltration (XHDF) is aimed at the transitory support of a patient with fulminant hepatic failure. The first clinical case of XHDF is presented. The system consisted of cross-circulation between a porcine liver and a patient with fulminant liver failure through a polyacrylonitrile membrane. The procedure lasted for 5 hours and produced hemodynamic, biochemical, and metabolic improvements. Intracranial pressure decreased from 34 to 5 cm H2O, serum ammonia fell from 673 to 370 ng/dl, lactic acid from 11 to 5.3 mmol/L, and bilirubin from 7.4 to 2.5 mg/dl. Hemodynamic values were maintained stable throughout the procedure. The patient was able to undergo transplantation and remains alive 11 months later. XHDF is a clinical experimental method that can constitute an alternative clinical therapy to support patients with fulminant hepatic failure until an organ is available for transplantation.

Surface modification of poly(ethylene-co-vinyl alcohol) (EVA). Part I. Introduction of carboxyl groups and immobilization of collagen

To enhance the surface biocompatibility of poly(ethylene-co-vinyl alcohol) (EVA) and high-density polyethylene (HDPE), carboxyl groups were introduced by ozone exposure. Type I collagen was immobilized onto the surface through polyion complexing. The carboxyl groups on the EVA were characterized by electron spectroscopy for chemical analysis and neutralization. The amounts of the carboxylic group and collagen increased with increases in time and temperature of exposure. Water-soluble fragments were produced by ozone exposure to EVA, and they acted as collagen crosslinkers. The differences in charge distribution of carboxyl groups affected the amount of collagen immobilization. Graft polymerization of acrylic acid was also carried out onto EVA and HDPE surfaces. The amount of collagen immobilized by graft polymerization was much higher than that by ozone exposure despite the introduction of almost the same amounts of carboxylic groups. It was suggested that the negative charge distribution influences the amount of collagen immobilized onto films.

Development of artificial articular cartilage

Attempts have been made to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which the lubrication and load-bearing mechanisms of natural and artificial joints are compared. Polyvinyl alcohol hydrogel (PVA-H), 'a rubber-like gel', was investigated as an artificial articular cartilage and the mechanical properties of this gel were improved through a new synthetic process. In this article the biocompatibility and various mechanical properties of the new improved PVA-H is reported from the perspective of its usefulness as an artificial articular cartilage. As regards lubrication, the changes in thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading were measured and it was found that PVA-H had a thicker fluid film under higher pressures than polyethylene (PE) did. The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times that of PE. Histological studies of the articular cartilage and synovial membranes around PVA-H implanted for 8-52 weeks showed neither inflammation nor degenerative changes. The artificial articular cartilage made from PVA-H could be attached to the underlying bone using a composite osteochondral device made from titanium fibre mesh. In the second phase of this work, the damage to the tibial articular surface after replacement of the femoral surface in dogs was studied. Pairs of implants made of alumina, titanium or PVA-H on titanium fibre mesh were inserted into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. The clinical implications of the possible use of this material in articular resurfacing and joint replacement are discussed.

In vivo evaluation of 2-cyanoacrylates as surgical adhesives

To evaluate 2-cyanoacrylates as surgical adhesives, the bond strength in vivo as well as the tissue reaction was investigated using methyl-, ethyl-, isobutyl-, and ethoxyethyl-2-cyanoacrylate. In addition, their set time and spreading on blood were studied. When the 2-cyanoacrylates were applied to an incised site of rabbit skin, they could maintain the skin closure without suturing during the first week and the bond strength increased during the second week. Significant inflammatory response was observed around the subcutaneous tissue glued with methyl- and ethoxyethyl-2-cyanoacrylate and persisted for approximately one week. All the 2-cyanoacrylate polymers were absorbed and the tissues treated were healed two weeks after the operation. There was a mild inflammatory reaction in the tissue treated with ethyl- and isobutyl-2-cyanoacrylate, and their polymers still remained at the wound site at the second week postoperatively. The disappearance rate of the 2-cyanoacrylate polymers was roughly in proportion to the inflammatory tissue response. Ethoxyethyl-2-cyanoacrylate spread more broadly on tissues than the other 2-cyanoacrylates, while its set time was shorter than that of methyl- and ethyl-2-cyanoacrylates.

Biodegradation and tumorigenicity of implanted plates made from a copolymer of epsilon-caprolactone and L-lactide in rat

Flat plates made from a copolymer of epsilon-caprolactone and L-lactide (P-CL-LA) [50:50 (w/w), molecular weight 1.62 x 10(5); 20 x 10 x 1 mm size] were subcutaneously implanted into 50 young, male Wistar rats (P-CL-LA group). After 24 months the plates had become a mass of small pieces, which were concentrated in an area of 3 x 2 x 1 mm. For comparison, 50 rats were implanted with medical-grade polyethylene plates (PE group) while another set of 50 rats was subjected to the same operation but without an implant (Sham Op group). Tumors arose in 25 rats from the P-CL-LA group: 24 were malignant mesenchymal tumors at the implant sites. In the PE group, tumors appeared in 16 rats (14 at the implant sites and two ectopically). The average tumor latency was 578+/-84 days in the P-CL-LA group and 452+/-102 days in the PE group. There was no difference in tumor incidence between the P-CL-LA and PE groups (p < 0.05). In the Sham Op group, two malignant tumors appeared over 2 years. Pathologically, these induced tumors arose from the inflammatory cells surrounding the degrading fragments of P-CL-LA within the tissue capsule. This indicates that relatively slowly degrading material can induce malignant tumors at a similarly high rate to nonabsorbable medical grade PE, at least in this animal model.

Experimental and clinical evaluation of cisplatin-containing microspheres as intraperitoneal chemotherapy for ovarian cancer

BACKGROUND

We aimed to evaluate the in vitro and in vivo effects of poly [L-lactic acid] microsphere containing cisplatin (CDDP-MS) for intraperitoneal (i.p.) chemotherapy for ovarian cancer.

METHODS

We initially examined the in vitro and in vivo profile of cisplatin release from the CDDP-MS, then this drug delivery system was evaluated in 15 patients.

RESULTS

The in vitro study showed that cisplatin was released constantly over a 3-week period. Rats in the CDDP-MS group had a significantly lower peak serum concentration of platinum compared with rats in the aqueous cisplatin solution (CDDP-S) group; the serum concentration of platinum showed a gradual decline. The ascitic fluid concentration of platinum also gradually decreased in the CDDP-MS group. We treated 15 patients with recurrent ovarian cancer with CDDP-MS containing 200 mg of cisplatin (n = 5) or CDDP-S containing 100 mg of cisplatin (n = 10) administered i.p. The peak serum and ascites concentrations of platinum were lower immediately after administration of CDDP-MS than after administration of CDDP-S, but increased over time in the CDDP-MS group, reflecting the slow-release effect of CDDP-MS. Grade 1 to 2 leukopenia and/or neutropenia occurred in 2 of 5 patients. No thrombocytopenia or renal or neurologic toxicity was observed;

CONCLUSION

These findings indicate that the i.p. administration of CDDP-MS increased the dose intensity of cisplatin and appeared to be safe and effective for the treatment of ovarian cancer.

Occlusive effects of lactic acid-glycolic acid copolymer membrane on gingival fibroblasts in vitro

The cell occlusive effects on human gingival fibroblasts of degradable lactic acid-glycolic acid copolymer membranes (noncoated membranes) and membranes coated with a sucrose ester of fatty acid (coated membranes) were studied and compared with those of expanded polytetrafluoroethylene (e-PTFE) membranes. The membranes were immersed in a culture medium periodically for 21 days and interposed into a chemotaxis chamber, and the fibroblasts then were cultured in the chamber for another 7 days. The passage rate of cells through the membranes was calculated and the change in surface structure of each membrane after immersion for 28 days was observed by an environmental scanning electron microscope. The passage rate of coated membranes (3.4+/-2.2%) was significantly lower than that of noncoated (25.7+/-5.1%) at the 28th day whereas the passage rate of e-PTFE membranes was 0.8-1.5%. Many pores were observed on the noncoated membranes before immersion while the coating material covered most of the pores on the coated membranes. The average pore size of the noncoated membranes was larger than that of the coated membranes at day 28. The structure of the e-PTFE membranes underwent no change. The passage rate of the coated membranes was not different from the e-PTFE membranes, suggesting an effect that might be useful for a guided tissue regeneration procedure.

Synthesis of polylactides with different molecular weights

The synthesis of poly(lactic acid) through polycondensation of the lactic acid monomer gave weight average molecular weights (Mw) lower than 1.6 x 10(4), whereas ring-opening polymerization of lactides in bulk at 130 degrees C for 72 h using stannous octoate as catalyst in the concentration range from 0.003 to 0.8 wt% produced polylactides with viscosity average molecular weight (Mv) ranging from 2 x 10(4) to 6.8 x 10(5). The monomer conversion and Mv showed a maximum at a catalyst concentration around 0.05 wt%. The monomer conversion and Mv increased almost linearly with polymerization time up to a monomer conversion of 80%, but both the conversion and Mv decreased after passing through a maximum, when the polymerization reaction was allowed to proceed for longer periods of time. This time dependence was pronounced at higher polymerization temperatures. The decrease in Mv at prolonged polymerization and higher polymerization temperatures was attributed to thermal depolymerization of resultant polylactides, but no significant optical rotation of poly(L-lactide) was noticed.

Polyacrylonitrile membrane interposition between a xenograft and an animal in fulminant liver failure. The concept of xenohemodiafiltration

In fulminant liver failure (FLF) there is need for support as a bridge to liver transplantation. Based on the concepts of hemofiltration and xenotransplantation, the authors present a model of liver support in FLF. The authors performed a portacaval shunt and ligature of the hepatic artery in 12 pigs. In six pigs (Group A) continuous hemofiltration through a polyacrylonitrile membrane was performed. Six isolated dog's livers were catheterized through the portal vein and perfused with autologous erythrocytes, albumin, and electrolytes in a closed circuit. With the use of the auxiliary liver, the circuit was connected to one of the lateral outlets of the hemofilter, while the other lateral outlet was connected to the portal vein through the pump. Thus, a polyacrylonitrile exchange membrane was created between the blood of the pig with FLF and the auxiliary liver's circulation. In Group B (controls), six pigs were connected directly to the auxiliary liver through a pump. In Group A, the auxiliary liver worked for 8 hr, without evidence of macroscopic or histologic damage. Lactic acid and ammonia levels improved: lactic acid, 8.2 +/- 6 mmol/L to 1.6 +/- 1 mmol/L; ammonia 487 +/- 110 micrograms/dl to 117 +/- 13 micrograms/dl, p < 0.1. The lidocaine clearing (MEGX) test results remained at functional levels (> 90 ng/ml) at the end of the perfusion. In Group B, the perfusion was discontinued at 60 +/- 15 min because of evidence of necrosis of the auxiliary liver. Lactic acid levels increased from 8.19 +/- 1.1 mmol/L to 13 +/- 4 mmol/L, ammonia levels remained high (390 +/- 15 micrograms/dl to 480 +/- 80 micrograms/dl), and the MEGX test results showed levels below functional activity by the end of the perfusion (45 +/- 30 ng/ml). The authors conclude that the concept of xenohemodiafiltration based on the interposition of a polyacrylonitrile membrane between a xenograft and an animal in FLF is adequate to support functions of detoxification and could be used in the future in the support of patient with FLF.

New biodegradable oligoesters for pharmaceutical application

Tartaric acid, malic acid, and glyceric acid were copolycondensed with glycolic acid at various molar ratios in feed to quickly synthesize biodegradable oligoesters. They were likely to have a moderately cross-linked structure with relatively low molecular weights and hydrophilic groups on the chains. In addition to macroscopic gels which were insoluble in any solvents, we could obtain the oligoesters which were insoluble in water but soluble in N,N-dimethylformamide. The degradation rate of the oligoesters was higher than that of lactic acid (LA) oligomers having molecular weights of a few thousands. On the contrary, their glass transition and flow temperatures were much higher than those of LA oligomers, indicating that their handling during the preparation of drug delivery dosage forms was much improved. The formulation of microspheres containing drugs from the oligoesters revealed that they were useful as biodegradable matrices having high degradation rates.

Degradation of high molecular weight poly(L-lactide) in alkaline medium

To study the effect of molecular weight and morphology on hydrolytic degradation, four poly(L-lactide)s (PLLAs) with average molecular weight of 3.0 x 10(5), 4.5 x 10(5), 6.5 x 10(5) and 3 x 10(6) were used. PLLA films with different morphologies were obtained by solution casting. Degradation of the films was performed at 37 degrees C in 0.01 N NaOH solution and this alkaline hydrolysis seemed to simulate well the real case while offering significant acceleration of the degradation process. Diverse microscopy techniques (light, polarizing and scanning electron) were used to study the surface change of morphology and erosion of the PLLA films. Swelling was visualized by scanning electron microscopy, particularly on the spherulites, which were eroded from the centre by hydrolysis. In the case of highly amorphous film, crystallization took place as degradation proceeded. The reduction in transparency of PLLA films, measured by a spectrophotometer at 570 nm, was ascribed to the increased density of spherulites. Differential scanning calorimetry revealed that the crystallinity of PLLA increased with degradation time, in accordance with accelerated spherulite formation.

Clinical evaluation of uniaxially oriented poly-L-lactide rod for fixation of experimental femoral diaphyseal fracture in immature cats

Transverse diaphyseal fractures of the femur were experimentally made in immature cats, and were fixed by an intramedullary pinning technique using an uniaxially oriented poly-L-lactide (PLLA) rod, a biodegradable polymer. The healing process was evaluated radiographically and histologically. Formation of bony callus was completed in 8 weeks, and cortical bony union followed. The remodeling process was then observed form 12 to 16 weeks. The healing process was almost the same as when a metallic implant was used. Abundant periosteal callus formation may be attributable to the lower elasticity of the PLLA rod compared with metallic implants. Since no other abnormalities such as growth deformities were detected, it was concluded that the combined use of a uniaxially oriented PLLA rod and an external splint is clinically useful for the repair of diaphyseal fractures in immature cats.

Scleral plug of biodegradable polymers for controlled drug release in the vitreous

We designed a new device, a scleral plug, that releases drugs into the vitreous after being implanted and fixed at the pars plana. Use of the plug for provision of doxorubicin hydrochloride was evaluated in rabbits. The scleral plug (8.5 mg) was made of poly(lactic-glycolic acid) (molecular weight, 40,000 daltons) containing 1% doxorubicin. Vitreous concentrations of doxorubicin were measured after the implantation. In vitro studies showed that the plug released 26% of the drug during 4 weeks. In vivo studies demonstrated that the concentration in the vitreous humor was maintained at a therapeutic range for longer than 4 weeks. No substantial toxic reactions were observed by electroretinographic and histopathologic evaluations. Our findings suggested that a scleral plug made of biodegradable polymers is a promising device for a controlled drug-release system in the vitreous.

Bioabsorbable struts made from poly-L-lactide and their application for treatment of chest deformity

Poly-L-lactide, a polymer of lactic acid, shows slow degradation in living tissue. Poly-L-lactide plate of high molecular weight maintains more than 90% of its initial mechanical properties for more than 3 months after implantation. Using struts made from poly-L-lactide plate, we performed chest wall reconstruction in 56 patients: for postoperative chronic sternal dehiscence in 23 and sternal elevation for pectus excavatum in 33 cases. The postoperative external appearances of the anterior chest were improved in comparison with the preoperative state in all cases. The internal features were evaluated by computed tomographic scan. Neither postoperative wound infection nor respiratory complication was observed, and no tendency for regression of the anterior chest occurred in any of the patients. In 3 of 56 cases (5.4%; one in the sternal dehiscence group and two in the pectus excavatum group), it was necessary to remove part of the strut because of overgrowth of granulation tissue around the implanted material after 4, 12, and 13 postoperative months, respectively. In the pectus excavatum group, the computed tomographic evaluations showed that poly-L-lactide strut maintained sufficient strength to support the thoracic wall 5 months after implantation. These findings suggest that the bioabsorbable poly-L-lactide strut is a promising material for surgical treatment of chest deformity.

Effect of polylactic acid on osteoinduction of demineralized bone: preliminary study of the usefulness of polylactic acid as a carrier of bone morphogenetic protein

To evaluate the usefulness of polylactic acid (PLA), a bioabsorbable and plastic polymer, as a carrier of bone morphogenetic protein (BMP), a preliminary study has been carried out to investigate any negative effect of PLA on osteoinduction of demineralized bone (DB). PLA (10,600 mol. wt) was mixed with DB particles (1-1.5 mm square) prepared from rat femurs and laid subcutaneously on the intercostal muscle of 4-week-old Wistar rats. The PLA/DB pellets were harvested at 2, 4, 8 and 24 weeks after the operation, and prepared for light microscopic examination. Histological examination revealed cartilage formation at 2 weeks and new bone formation at 4 weeks. Extensive bone and marrow formation were observed at 24 weeks. PLA was gradually absorbed and completely disappeared at 24 weeks to be replaced by connective tissue. These results demonstrate that PLA does not have a negative influence on the osteoinductive activity and that PLA could well be a promising bioabsorbable carrier of BMP.

Tumorigenicity of poly-L-lactide (PLLA) plates compared with medical-grade polyethylene

Poly-L-lactide (PLLA) plates, 20 x 10 x 1 mm in size, with flat surfaces, were implanted into 50 young male Wistar rats subcutaneously, and the incidence of tumors for 2 years under specific pathogen-free (SPF) conditions was evaluated. Tumors arose in 22 rats (at the implant sites in 20, and distant from the implantation site in 2). As a control, plates of medical-grade polyethylene of the same shape were implanted into 50 rats. Tumors appeared in 23 of these rats (21 at the sites of the plates, and 2 ectopically). In 30 rats given sham operations, no tumors appeared in the 2 year observation period. Histologically, all the tumors were mesenchymal malignant tumors resembling fibrosarcoma or malignant fibrous histocytoma (MFH) in humans. In 6 of the PLLA tumors and 3 of the PE tumors, bone formation was observed. There was no significant difference between the incidence of tumors caused by PLLA plates and that of tumors caused by medical-grade polyethylene plates. Macroscopically, PLLA plates retained their initial shape for 2 years. Scanning electron microscopy revealed small holes on the surfaces of the plates, and their molecular weight was reduced to 8% of the initial value.

Poly(vinyl alcohol) hydrogels as soft contact lens material

A new type of soft contact lens was developed from the poly(vinyl alcohol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent. The PVA contact lens materials had a water content of 78% and a tensile strength of 50 kg/cm2, five times as strong as that of commercial poly(2-hydroxyethyl methacrylate) soft contact lens. The amount of proteins adsorbed to the PVA soft hydrogel material was half to one thirtieth of that of conventional soft contact lenses. Histological and scanning electron microscopic observation of rabbit eyes which had worn the PVA soft contact lens for 12 weeks showed no difference in corneal epithelium and cell arrangement in the corneal epithelium from the non-wearing eyes.

Pharmacologic effects of cisplatin microspheres on peritoneal carcinomatosis in rodents

BACKGROUND

A new drug-delivery formulation of cisplatin, whereby cisplatin was incorporated in lactic acid oligomer microspheres (CDDP-MS), has been developed in dosage form for peritoneal carcinomatosis and has been designed to release 70% of the incorporated cisplatin slowly during a period of 3 weeks. In this study, its pharmacologic effects were examined in rodents.

METHODS

CDDP-MS was tested to determine (1) tissue distribution of cisplatin after intraperitoneal administration of cisplatin at 3.0 mg/kg body weight to rats, (2) acute toxicity in mice when injected intraperitoneally, and (3) therapeutic effects on peritoneal carcinomatosis induced by transplantable M5076 tumors in mice.

RESULTS

These experiments revealed the following: (1) CDDP-MS resulted in a higher cisplatin concentration in tissues adjacent to the peritoneum for a longer period, and the concentration of cisplatin measured in the rest of the body was lower than that delivered by the cisplatin aqueous solution; (2) the 50% lethal dose value, determined by the Litchfield-Wilcoxon method, was 23.8 mg/kg body weight in CDDP-MS in terms of cisplatin, whereas in the cisplatin aqueous solution it was 13.5 mg/kg body weight; (3) CDDP-MS enhanced therapeutic effects when compared with the same toxicity dosage of cisplatin aqueous solution.

CONCLUSIONS

Intraperitoneal CDDP-MS releases cisplatin into the peritoneal cavity for a long time, and it results in less systemic toxicity and greater therapeutic effects on peritoneal carcinomatosis than does cisplatin aqueous solution.