Controllable Preparation and Performances of Monodisperse Genipin-Cross-Linked Gelatin–Chitosan Composite Embolic Microspheres

The controllable fabrication and performances of monodisperse genipin-cross-linked gelatin-chitosan composite (GGC) embolic microspheres with both uniform sizes and adjustable characteristics of elasticity and degradation are reported for the first time. Monodisperse emulsion droplets are fabricated as templates by using gelatin and chitosan aqueous solution as the disperse phase in a microfluidic device, and the chemical cross-linking of gelatin and chitosan inside droplet templates is achieved with genipin that transfers from the collection bath into the droplets. The sizes of droplet templates and the resultant GGC microspheres can be flexibly controlled and predicted by adjusting the fluid flow rates and the device dimensions. The elastic property of GGC microspheres can be flexibly regulated by adjusting the molar ratio of gelatin/chitosan in the disperse phase. The <i>in vitro</i> degradation-caused dynamic volume shrinkage of GGC microspheres can be flexibly regulated by adjusting the molar ratio of gelatin/chitosan, the chitosan deacetylation degree, and the enzyme concentration in degradation solution. Based on the Box-Behnken design-response surface method, a second-order equation is developed for the first time to predict the <i>in vitro</i> degradation-caused dynamic volume shrinkage ratios of microspheres prepared with different molar ratios of gelatin/chitosan and different chitosan deacetylation degrees in degradation solutions with different enzyme concentrations. The fabricated GGC microspheres show good repeatable embolization performances in an <i>in vitro</i> embolization chip system. The results of this study provide valuable guidance for controllable fabrication of degradable microspheres with both uniform sizes and on-demand elastic and degradation characteristics for efficient application in embolization therapy.