Macroporous hydrogel membranes for a hybrid artificial pancreas. I. Synthesis and chamber fabrication.

We report development of special macroporous semipermeable membranes and diffusion chambers made of polymerized 2-hydroxyethyl methacrylate (pHEMA), synthesized specifically to enclose living insulin-producing pancreatic islet cells for the treatment of diabetes. This material was selected to minimize the fibrotic encapsulation which has limited hybrid artificial pancreas efforts with other membranes, including Millipore and Nuclepore filters. The pore density and pore size distribution were dependent on the ratio of water to HEMA monomer and also on the crosslinker (EGDMA) concentration. A macroporous membrane resulted only when the ratio of water/HEMA monomer was greater than 50%. 125I-insulin permeability was studied in vitro. A technique is also described to fuse the membranes to form diffusion chambers used for implantation into diabetic rats.

A new biomaterial for the control of infection in the burn wound.

A synthetic dressing has been developed that isolates the burn wound to protect patients from microbial contamination. This dressing is unique as it is formed from a 2-component system directly on the wound, leaving no voids for microbial proliferation. The synthetic cover, HYDRON Burn Dressing, adheres to the entire wound surface so that additional dressings are not required. It is sufficiently flexible to permit patient mobility. The components used to form the dressing are an ultra-pure, high molecular weight form of HYDRON, a hydrophilic polymer, poly (2-hydroxyethyl methacrylate) and Polethylene Glycol-400. The dressing is intended to be applied directly to the wound immediately post-burn, prior to sloughing or removal of the eschar, a period in the burn therapy regimen for which satisfactory alternative dressings are not readily available. Decreased frequency of dressing changes compared to conventional procedure provides an additional benefit with a corresponding reduction in pain to the patient. Gross examination of the wounds under the dressing has shown that the healing process proceeds similarly to that of wounds under conventional treatment. There is no evidence of fluid accumulation or maceration or desiccation of the eschar. In our series of 32 patients the barrier dressing formed on the wound has offered a new, effective procedure for treatment of the burn wound.

Biocompatible implants for the sustained zero-order release of narcotic antagonists.

Implantable, sustained release drug delivery devices offer benefits not obtained through oral ingestion or injection. These include delivery at a constant therapeutic rate, thus avoiding adverse intermittent and massive dose effects, as well as reliance upon patients taking their prescribed dosages. The drawbacks to their widespread acceptance have been their inability to maintain a zero-order release rate over an extended period of time and poor biocompatibility. Devices capable of satisfying these requirements have been developed and tested extensively for in vitro release of the narcotic antagonist cyclazocine. By using implant models prepared from Hydron, a hydrophilic polymer known to exhibit excellent tissue compatibility, we have found that the release rate could be precisely regulated by proper geometry, copolymer composition, concentration of ionogenic groups and cross-link density. Devices in such varied forms as capusles, barrier-film coated tablets and bulk polymerized rods have been tested in vitro for periods approaching 1 year.