Preparation and Characterization of Microspheres Based on Gelatin-Sodium Alginate-Genipin by the Formation of Polyelectrolyte Complex

The Biodegradable polymers with non-toxic and biocompatible nature have applications in tissue engineering and drug delivery. The use of natural polymer microbeads independently or in combination with other materials is gaining ground in various applications including injectable biomaterials. In this research, the interaction of gelatin and sodium alginate biopolymers was investigated in the manufacture of microsphere. The interaction between these two polymers was influenced by their pH, charge, and concentration. The electrostatic reaction between positively charged proteins and anionic polysaccharides led to the formation of soluble and insoluble phases. Therefore, the effect of pH and colloidal ratio was examined on the Coacervation. First, gelatin molecular weight was narrowed by Desolvation method, and GPC confirmed the elimination of low molecular weight gelatin. The supernatants of colloidal mixtures were analyzed by UV-Vis test, and the results revealed that optimum coacervation occurred at a gelatin/sodium alginate ratio of four and a pH value of 3.65. During this process, microsphere formed with smooth surfaces in a size range of 10-25 µm. An increase in the amount of genipin raised the aggregation tendency in independent microbeads. A slight change of gelatin in Circular Dichroism (CD) reflected the interaction with sodium alginate, which was confirmed by the amide functional group in the Fourier-transform infrared (FTIR) spectroscopy. Results of Thermogram of Differential Scanning Calorimetry (DSC) indicated an increase in the degradation temperature of microspheres containing higher amounts of genipin.