Influence of gelatin and collagen incorporation on peroxidase-mediated injectable pectin-based hydrogel and bioactivity of fibroblasts.

Pectin has recently attracted increasing attention for biomedical and pharmaceutical applications. Due to the lack of adhesion molecules in polysaccharides, phenolic hydroxyl conjugated gelatin was added to enzymatically-gellable peroxidase-modified pectin derivative and compared with phenolic hydroxyl -pectin/collagen. Both pectin and gelatin were modified by tyramine hydrochloride in the presence of EDC/NHS. The phenolic hydroxyl -pectin/phenolic hydroxyl -gelatin, phenolic hydroxyl-pectin/collagen, and phenolic hydroxyl -pectin hydrogels were prepared using horseradish peroxidase and hydrogen peroxide. The hydrogels were characterized by gelation time analysis. Morphology, enzymatic biodegradation, mechanical and swelling properties as well as water vapor transmission rate were also evaluated. Fibroblasts were cultured for 7 days, and the survival rate was evaluated using conventional MTT assay. Hydrogels composed of Ph-pectin/Ph-gelatin showed decreased biodegradation rate, and WVTR and further improved mechanical performance in comparison with other groups. Both phenolic hydroxyl -pectin/collagen and phenolic hydroxyl -pectin/phenolic hydroxyl -gelatin hydrogels exhibited porous structures. The hydrogels composed of collagen promoted cell survival rate 1.4 and 3.5 times compared to phenolic hydroxyl -gelatin and phenolic hydroxyl -pectin based hydrogels at the end of 7 days, respectively (p < 0.001). The study demonstrated the potential of enzymatically-gellable pectin-based hydrogels as cost-effective frameworks for use in tissue engineering applications.

Gelatin improves peroxidase-mediated alginate hydrogel characteristics as a potential injectable hydrogel for soft tissue engineering applications.

To develop an efficient injectable alginate-based hydrogel for soft tissue engineering applications, phenol moiety (Ph) was introduced into alginate (Alg-Ph), and the influence of gelatin as cell adhesive molecule was evaluated on the peroxidase-mediated alginate hydrogel properties and cultured chondrocytic cell behavior. Addition of gelatin (1.5% w/v) to Alg-Ph (1.5% w/v) hydrogels (Alg-Ph/gelatin) regulated characteristics of the enzymatically gellable alginate hydrogel with increasing gelation time to 5.1 min (76%). Swelling ratio and degradation rates of the Alg-Ph/gelatin hydrogel also increased 60 and 100%, respectively, while the mechanical strength value was 35% less than the Alg-Ph hydrogel. Scanning electron microscopy images showed that the addition of gelatin could also increase uniformity of pore sizes inside the Alg-Ph/gelatin hydrogels. The chondrocyte cells maintained their original phenotype and revealed statistically more metabolic activities in the Alg-Ph/gelatin hydrogel. Hydrogels subscutaneously implanted in rats could also be identified readily without complete absorption and signs of toxicity or any untoward reactions after 1 month. Viable chondrocyte cells inside globular aggregates were seen as red colored areas in the cell-laden hydrogels. The study demonstrates that enzymatically gellable alginate/gelatin hydrogel has fair potential as a natural-based injectable hydrogel for soft tissue engineering applications.