Effect of calcium phosphate-based fillers on the structure and bonding strength of novel gelatin-alginate bioadhesives

Interest in soft and hard tissue adhesives as alternatives for conventional wound closing and bone fixation applications has increased in recent decades as a result of numerous possible advantages such as better comfort and lower cost. A novel bioadhesive based on the natural polymers GA has recently been developed and studied in our laboratory. Hydroxyapatite and tricalcium phosphate are two bioactive ceramics known for their ability to enhance bone regeneration. In the current study, these two bioactive fillers were incorporated into the bioadhesive at concentrations of 0.125, 0.25 and 0.5% w/v, and their effects on the resulting adherence properties to soft and hard tissues were studied. Porcine skin and cortical portions of bovine femurs were used as soft and hard tissue specimens, respectively. The bonding strength was evaluated using an Instron universal testing machine in tensile mode, and the microstructure analysis was based on environmental scanning electron microscope observations. Both bioactive fillers were found to have a reinforcing effect on the adhesives, significantly improving their adhesion to soft tissues in certain concentrations. The best bonding strength results were obtained for 0.25% hydroxyapatite and 0.5% w/v tricalcium phosphate-18.1 ± 4.0 and 15.2 ± 2.6 kPa, respectively, compared with 8.4 ± 2.3 kPa for adhesive with no fillers. The improved adherence is probably related to the stiffness of the insoluble hydroxyapatite and tricalcium phosphate particles which reinforce the adhesive. These particles can clearly be observed in the environmental scanning electron microscope analysis. The potential of these fillers to increase the bonding strength of the adhesive to hard tissues was also demonstrated. Hydroxyapatite and tricalcium phosphate thus improve our new gelatin-alginate bioadhesives, which can be used for both soft and hard tissue adhesive applications.