Correlations between structure, material properties and bioproperties in self-assembled beta-hairpin peptide hydrogels.

A de novo designed beta-hairpin peptide (MAX8), capable of undergoing intramolecular folding and consequent intermolecular self-assembly into a cytocompatible hydrogel, has been studied. A combination of small angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM) have been used to quantitatively investigate the MAX8 nanofibrillar hydrogel network morphology. A change in the peptide concentration from 0.

Chitosan and lactic acid-grafted chitosan nanoparticles as carriers for prolonged drug delivery.

Nanoparticles of approximately 10nm in diameter made with chitosan or lactic acid-grafted chitosan were developed for high drug loading and prolonged drug release. A drug encapsulation efficiency of 92% and a release rate of 28% from chitosan nanoparticles over a 4-week period were demonstrated with bovine serum protein. To further increase drug encapsulation, prolong drug release, and increase chitosan solubility in solution of neutral pH, chitosan was modified with lactic acid by grafting D,L-lactic acid onto amino groups in chitosan without using a catalyst.

Tissue response and Msx1 expression after human fetal digit tip amputation in vitro.

Regeneration of mammalian digit tips is well described; however, associated cellular or molecular events have not been studied in humans. We describe an in vitro human fetal model of response to digit tip amputation, and report expression of the transcription repressor Msx1 in the developing and regrowing human digit tip. Human fetal digits from specimens ranging from 53 to 117 days' estimated gestational age (EGA) were cultured in a defined serum-free medium with supplemented oxygen for time periods from 4 days to 4 weeks.

PEG-grafted chitosan as an injectable thermosensitive hydrogel for sustained protein release.

Thermosensitive polymer hydrogels that undergo a sol-to-gel transition in response to temperature changes are of great interest in therapeutic delivery and tissue engineering as injectable depot systems. A chitosan-based, injectable thermogel was prepared by grafting an appropriate amount of PEG onto the chitosan backbone and studied for drug release in vitro using bovine serum albumin (BSA) as a model protein. When more than approximately 40 wt.

Chitosan-alginate hybrid scaffolds for bone tissue engineering.

A biodegradable scaffold in tissue engineering serves as a temporary skeleton to accommodate and stimulate new tissue growth. Here we report on the development of a biodegradable porous scaffold made from naturally derived chitosan and alginate polymers with significantly improved mechanical and biological properties as compared to its chitosan counterpart. Enhanced mechanical properties were attributable to the formation of a complex structure of chitosan and alginate.

Biphasic calcium phosphate nanocomposite porous scaffolds for load-bearing bone tissue engineering.

A novel biodegradable nanocomposite porous scaffold comprising a beta-tricalcium phosphate (beta-TCP) matrix and hydroxyl apatite (HA) nanofibers was developed and studied for load-bearing bone tissue engineering. HA nanofibers were prepared with a biomimetic precipitation method. The composite scaffolds were fabricated by a method combining the gel casting and polymer sponge techniques.

Preparation of porous hydroxyapatite scaffolds by combination of the gel-casting and polymer sponge methods.

A new technique of combining the gel-casting and polymer sponge methods is introduced in this study to prepare macroporous hydroxyapatite scaffolds, which provides a better control over the microstructures of scaffolds and enhances their mechanical properties. With this technique, we were able to produce scaffolds with mechanical and structural properties that cannot be attained by either the polymer sponge or gel-casting method. The scaffolds prepared have an open, uniform and interconnected porous structure with a pore size of 200-400 microm.