Encapsulation of porcine pancreatic islets within an immunoprotective capsule comprising methacrylated glycol chitosan and alginate.

Encapsulation of cells in biocompatible polymer matrices represents a powerful tool for cell-based therapies and therapeutic delivery systems. This technology has successfully been used to deliver pancreatic islets to humans for the treatment of Type 1 diabetes. However, the clinical impact of this technology may be improved by reducing the inflammatory response brought on after implantation of capsules in vivo.

Improving alginate-poly-L-ornithine-alginate capsule biocompatibility through genipin crosslinking.

DIABECELL® capsules comprise an inner core of alginate (Alg) coated with a polycationic polymer, poly-L-ornithine (PLO), designed as a stabilizing agent for strengthening the capsule wall, which is masked by an outer layer of biocompatible Alg. These polymeric microcapsules have demonstrated excellent mechanical properties and a reduction in hypoglycemia after tranplantation in human clinical trials; however, degradation of the outer Alg layer leaves the underlying layers of PLO exposed, which ultimately leads to reduced biocompatibility in vivo. Here we aim to improve capsule biocompatibility and to increase the hydrophilic properties of the capsule surface through chemical crosslinking/modification of the PLO layer using genipin.

Effect of genipin cross-linking on the cellular adhesion properties of layer-by-layer assembled polyelectrolyte films.

Use of polyelectrolyte multi-layers as biomaterials for cell attachment has been limited due to their gel-like characteristics. Herein, we attempt to improve the cellular adhesion properties of multi-layer films, reduce their gel-like nature and rigidify them through chemical cross-linking with genipin; a natural and non-cytotoxic compound. Chitosan (CH), hyaluronan (HA) and alginate (Alg) were used to assemble [CH-HA]n CH and [CH-Alg]n CH films, and the effects of genipin cross-linking on the cell adhesion properties of these multi-layers were investigated.

Design and evaluation of thin and flexible theophylline imprinted polymer membrane materials.

The aim of this work was to produce a thin, flexible and diffusion able molecularly imprinted polymeric matrix with good template accessibility. Membranes were prepared using a non-covalent molecular imprinting approach and their physical characteristics and binding capabilities investigated. Two materials were used, a poly(tri-ethyleneglycol dimethyacrylate-co-methyl methacrylate-co-methacrylic acid) copolymer containing 14% cross-linker and a monomer (g) to porogen (ml) ratio of 1:0.

Biorecognition through layer-by-layer polyelectrolyte assembly: in-situ hybridization on living cells.

Encapsulated cells were formed from the assembly of cationic and anionic alternating layers using a number of polyelectrolyte-based systems. Chitosan, alginate, hyaluronic acid, and oligonucleotides were used as polyelectrolytes to encapsulate individual E. coli cells, which were used as a model.

The type IIs restriction endonuclease BspMI is a tetramer that acts concertedly at two copies of an asymmetric DNA sequence.

Type IIs endonucleases recognize asymmetric DNA sequences and cleave both strands at fixed positions downstream of the sequence. Many type IIs enzymes, including BspMI, cleave substrates with two sites more rapidly than those with one site. They usually act sequentially on DNA with two sites, but BspMI converted such a substrate directly to the final products cut at both sites.