Effect of collagen fiber and gelatin on gelling properties of alginate gels

Mixed gelatin-alginate gels are widely studied as encapsulating matrices. However, the dissolution of gelatin at mild temperatures (close to body temperature) imparts low stability for these systems, particularly as delivery matrices. In this context, collagen fiber arises as an alternative due to its water binding properties. Thus, the main objective of this work was to evaluate the effect of substituting gelatin for collagen fiber in alginate mixed gels. Thereunto, alginate and gelatin/collagen fiber were firstly mixed before added to water at 45°C. Solutions were magnetically stirred during 90 minutes and were set in dialysis membrane. The membranes were sealed and put into a vessel containing a calcium chloride solution. The influence of biopolymer gelling conditions on the characteristics of the formed gel was also evaluated by inducing the gelation of alginate prior to the protein (dialysis prior to cooling) or simultaneously. Gels were evaluated according to its visual aspect, compression tests (mechanical properties) and shrinkage after 24-hours at room temperature. Generally, collagen-mixed gels were larger than gelatin ones, with lower shrinkage observed after the 24-hour storage. Mechanical properties results showed that gelatin-alginate mixed gels were quite similar to pure alginate gels. Similar behaviour was observed for collagen-mixed systems in which biopolymers gelation occurred simultaneously, indicating that these systems may be a good alternative to the substitute gelatin in delivery systems.