Fabrication and Characterization of Gelatin/Chitosan Microspheres for Drug Release

In Vitro Biodegradation, Drug Absorption, and Physical Properties of Gelatin-Fucoidan Microspheres Made of Subcritical-Water-Modified Fish Gelatin

This study aimed to prepare gelatin-fucoidan microspheres with enhanced doxorubicin binding efficiency and controllable biodegradation using fish gelatin combined with low molecular weight (LMW) gelatin and fucoidan at fixed ratios. The MW of gelatin was modified by subcritical water (SW), which is known as a safe solvent, at 120 °C, 140 °C, and 160 °C. In addition, gelatin-fucoidan microspheres were prepared using a solvent exchange technique. Our findings revealed that particle size decreased, the surface was rougher, the swelling ratio increased, and particle shape was irregular in microspheres composed of SW-modified gelatin. Doxorubicin binding efficiency was improved by fucoidan and SW-modified gelatin at 120 °C but not at 140 °C and 160 °C. Interestingly, an increase in in vitro enzymatic degradation was observed in the microspheres consisting of SW-modified fish gelatin, although the cross-linking degree between them was not significantly different. This is because LMW gelatin could form more cross-linked bonds, which might be weaker than the intramolecular bonds of gelatin molecules. Gelatin-fucoidan microspheres consisting of SW-modified fish gelatin with controlled biodegradation rates could be a candidate for a short-term transient embolization agent. In addition, SW would be a promising method to modify the MW of gelatin for medical applications.

A new emulsification-crosslinking technique for preparation of physically crosslinked chitosan microspheres

A new emulsification-crosslinking method was developed for the preparation of chitosan microspheres. The new method uses an aqueous alkali–urea solution, instead of the commonly used acidic solvents, to dissolve chitosan. After emulsification, the water-in-oil droplets are solidified by heating, taking advantage of the unique in situ thermal gelling behavior of the alkaline chitosan solution, instead of by crosslinking with a usually toxic crosslinker. The size of the microspheres can be controlled by the concentration of chitosan solution, stirring speed, emulsifier concentration, and the curing temperature. The resulting microspheres are physically crosslinked, instead of chemically crosslinked, and they are ready to dissolve in dilute acetic acid. The resulting chitosan microspheres are non-toxic and can be degraded by lysozyme. Bovine serum albumin, a model protein, can be facilely loaded into the microspheres by adsorption, and then released from the microspheres.