Developing new synthetic biomimetic nanocomposite adhesives: Synthesis and evaluation of bond strength and solubilization

Complex coacervate adhesive analog of the glue secreted by a marine polychaete (Phragmatopoma California) was studied for gluing a wet bone. The aim of this in-vitro study is to investigate bond strength and solubilization of a complex, coacervate adhesive. A complex coacervate adhesive was synthesized by mixing aminated gelatin and polyphosphodopamid. Polyphosphodopamide (Poly (DMA-co-MOEP)) was synthesized by free radical polymerization of 2-(methacryloyloxy) ethyl phosphate (MOEP) and dopamine methacrylamide (DMA) (in the three ratios of MOEP to DMA: 11, 7, and 3) initiated with Azobisisobutyronitrile (AIBN) in MeOH at 60 °C for 24 h. The structure of polymers was characterized by IR and 1H NMR spectra. The surface charges of aminated gelatin were positive, and its average zeta potential was about 31.08 mV: this shows gelatin was slightly aminated. For obtaining the optimum condition of adhesive, at first we changed the amount of the cross-linkable groups, dopamine (DOPA) sidechains in DMA, and then we investigated bond strength and solubilization behaviors. After obtaining the optimal amount of DOPA sidechains in the adhesive, we added 10% Wt human bone nanopowder (HBN) to the adhesive as filler and surveyed that behavior again. Results showed that with increase in DOPA sidechains in the adhesive, bond strength increased and solubilization rate decreased. Also, by adding bone nanopowder to the adhesive, bond strength and solubilization rate increased. The SEM images of this complex coacervate adhesive show a porous structure where in most of the porosities are in the range of 10-50 μm. Cytotoxicity effect of the adhesive and the nanocomposite adhesive were investigated on bone marrow mesenchymal primer cells: the results demonstrated cell growth and proliferation. This study shows that complex coacervate nanocomposite adhesive is a good candidate to act as a bone adhesive for sternal closure.