Hydrophobically-modified gelatin hydrogel as a carrier for charged hydrophilic drugs and hydrophobic drugs.

Gelatin molecules have been chemically crosslinked using potentially cytotoxic reagents to prepare stable hydrogels. Hydrophobic interaction is a means of forming physical crosslinks that is a good candidate for enhancing the stability of gelatin hydrogels without using cytotoxic chemicals. In this study, we proposed a new method to fabricate hydrogels from hydrophobically-modified gelatin (HMG) with high content of hydrophobic segments. HMG was first dissolved in dimethyl sulfoxide and poured into a vial with the desired shape. After the solution was freeze-dried, the solid construct was hydrated. The HMG hydrogel containing basic fibroblast growth factor promoted angiogenesis in vivo, indicating that the positively charged hydrophilic growth factor formed an electrostatic complex with negatively charged HMG hydrogel and was gradually released in vivo with the degradation of the hydrogel. In addition, we showed that the hydrophobic segments of HMG enhanced the adsorption of fluorescein sodium, a model for hydrophobic therapeutic agents, to the hydrogel through hydrophobic interaction. Furthermore, in vitro experiments indicated that the hydrophobic agents would be released from the hydrogel in a controlled manner in vivo. These results show that the HMG hydrogel has significant potential as a carrier for both charged hydrophilic drugs and hydrophobic drugs.

Autoclavable physically-crosslinked chitosan cryogel as a wound dressing.

Moist wounds were known to heal more rapidly than dry wounds. Hydrogel wound dressings were suitable for the moist wound healing because of their hyperhydrous structure. Chitosan was a strong candidate as a base material for hydrogel wound dressings because the polymer had excellent biological properties that promoted wound healing. We previously developed physically-crosslinked chitosan cryogels, which were prepared solely by freeze-thawing of a chitosan-gluconic acid conjugate (CG) aqueous solution, for wound treatment. The CG cryogels were disinfected by immersing in 70% ethanol before applying to wounds in our previous study. In the present study, we examined the influence of autoclave sterilization (121°C, 20 min) on the characteristics of CG cryogel because complete sterilization was one of the fundamental requirements for medical devices. We found that optimum value of gluconic acid content of CG, defined as the number of the incorporated gluconic acid units per 100 glucosamine units of chitosan, was 11 for autoclaving. An increased crosslinking level of CG cryogel on autoclaving enhanced resistance of the gels to enzymatic degradation. Furthermore, the autoclaved CG cryogels retained favorable biological properties of the pre-autoclaved CG cryogels in that they showed the same hemostatic activity and efficacy in repairing full-thickness skin wounds as the pre-autoclaved CG cryogels. These results showed the great potential of autoclavable CG cryogels as a practical wound dressing.