Sequential antibiotic and growth factor releasing chitosan-PAAm semi-IPN hydrogel as a novel wound dressing.

The aim of this study is to prepare a novel wound dressing material which provides burst release of an antibiotic in combination with sustained release of growth factor delivery. This might be beneficial for the prevention of infections and to stimulate wound healing. As a wound dressing material, the semi-interpenetrating network (semi-IPN) hydrogel based on polyacrylamide (PAAm) and chitosan (CS) was synthesized via free radical polymerization. Ethylene glycol dimethacrylate was used for cross-linking of PAAm to form semi-IPN hydrogel. The hydrogel shows high water content (∼1800%, in dry basis) and stable swelling characteristics in the pH range of the wound media (∼4.0-7.4). The antibiotic, piperacillin-tazobactam, which belongs to the penicillin group was loaded into the hydrogel. The therapeutic serum dose of piperacillin-tazobactam for topic introduction was reached at 1st hour of the release. Additionally, in order to increase the mitogenic activity of hydrogel, epidermal growth factor (EGF) was embedded into the CS-PAAm in different amounts. Cell culture studies were performed with L929 mouse fibroblasts and the simulated cell growth was investigated by 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide assay. The successful sustained release behavior of CS-PAAm hydrogel for EGF maintained the presence of EGF in the culture up to 5 days and the highest mitochondrial activities were recorded for the 0.4 µg EGF-loaded/mg of hydrogel group. In conclusion, CS-PAAm semi-IPN hydrogel loaded with piperacillin-tazobactam and EGF could be proposed for an effective system in wound-healing management.

Derivation, characterization and expansion of fetal chondrocytes on different microcarriers.

Fetal chondrocytes (FCs) have recently been identified as an alternative cell source for cartilage tissue engineering applications because of their partially chondrogenically differentiated phenotype and developmental plasticity. In this study, chondrocytes derived from fetal bovine cartilage were characterized and then cultured on commercially available Cytodex-1 and Biosilon microcarriers and thermosensitive poly(hydroxyethylmethacrylate)-poly(N-isopropylacrylamide) (PHEMA-PNIPAAm) beads produced by us. Growth kinetics of FCs were estimated by means of specific growth rate and metabolic activity assay. Cell detachment from thermosensitive microcarriers was induced by cold treatment at 4 °C for 20 min or enzymatic treatment was applied for the detachment of cells from Cytodex-1 and Biosilon. Although attachment efficiency and proliferation of FCs on PHEMA-PNIPAAm beads were lower than that of commercial Cytodex-1 and Biosilon microcarriers, these beads also supported growth of FCs. Detached cells from thermosensitive beads by cold induction exhibited a normal proliferative activity. Our results indicated that Cytodex-1 microcarrier was the most suitable material for the production of FCs in high capacity, however, 'thermosensitive microcarrier model' could be considered as an attractive solution to the process scale up for cartilage tissue engineering by improving surface characteristics of PHEMA-PNIPAAm beads.