The Preliminary Study Of Constructing Injectable Scaffolds Via Self-assembling Of Natural Polysaccharides Microspheres

When calcium alginate (ALG) microspheres were used to construct microsphere based injectable scaffolds, the microspheres in the scaffolds usually had a migration phenomenon due to the low linkage of the adjacent microspheres, which could have effect on the mechanical performance of the scaffolds. In order to enhance the interaction force between the adjacent calcium alginate microspheres, the positively charged chitosan (CS) microspheres were prepared to attach the negatively charged calcium alginate microspheres together, forming self-assembly injectable scaffolds via electostatic interaction force.The reason of chosing chitosan to prepare the positively charged microspheres was that chitosan was a kind of natural positively charged polysaccharides, positively charged microspheres could be prepared by controlling the ratio of the CS:TPP. Two kinds of chitosan microspheres were prepared by emulsion-ionic gelation and spray drying technique, respectively. In the method of emulsion-ionic gelation, the factors of affecting the morphology of the microspheres, the average diameters and the distribution of the particle size were analysed to determine the suitable condition of preparing the chitosan microspheres. The suitable condition was:the viscosity was 260cps, the concentration of span80 was 2.5%, the concentration of chitosan was 2.5%, the speed of stiring was 700rpm, the volume ratio of oil to water was 2:1, the weight ratio of CS:TPP was 5:1, theζpotential of the chitosan microspheres was+ 5.3mv,and the average diameter was 47.48um; the other chitosan microspheres were prepared by spray drying, which theζpotential was + 8.5mv and the average diameter was 3.03um; the negatively charged calcium alginate microspheres were prepared by emulsion-internal gelation, which could meet the requirement of the experiment.Self-assembly scaffolds were fabricated by attaching the adjacent calcium alginate microspheres together via electrostatic interaction force. The phenomenon of electrostatic attachment was characterized by optical microscopy and scanning electron microscopy. The positively charged chitosan microspheres could attach onto the surface of the calcium alginate microspheres and anchor the adjacent calcium alginate microspheres together. This kind of microsphere based scaffolds could exhibit elastic compress modulus at a certain extent, and it was found that the elastic compress modulus of the scaffold which composed by spray drying chitosan microsphreres and calcium alginate microspheres, showed better than the other. The drug released from the self-assembly scaffolds was investigated in this research, too.It was a simple but effectively method to enhance the interaction of the adjacent microspheres to form the self-assembly scaffolds via electrostatic interaction force.