Synthesize And Properties Of Mussel-Inspired Poly(Aspartic Acid) Tissue Adhesive

Mussel biomimetic tissue adhesives have attracted wide attention due to their unique wet adhesive properties.By introducing the catechol groups into polymer segments,a dopamine-modified adhesive with outstanding wet adhesion was successfully synthesized,but it still remain some problems such as complex synthesis processes,the use of organic solvents in the synthesis process,and poor water solubility of the synthesized adhesive.Moreover,how to further improve the wet bonding strength and inherent biological functional characteristics of the adhesive need to be solved urgently.In this paper,PSI was synthesized by solid phase polymerization of L-aspartic acid.Then,dopamine-grafted poly（aspartic acid）（PLASP-DA）was synthesized by sodium bicarbonate as hydrolysis agent.The crosslinking agent system was composed of odium periodate（PI）solution,MgO nanoparticles and hydroxyapatite（HA）nanoparticles,which not only improved the mechanical properties and bond strength of bioadhesive but also gave the system inherent antibacterial properties and biological activity.The PLASP-DA was characterized by infrared spectroscopy（FTIR）,¹H-nuclear magnetic resonance spectroscopy（¹H-NMR）,ultraviolet spectroscopy（UV-Vis）and gel chromatography（GPC）.The effects of crosslinking agent composition on the gelling time,gel content,swelling ratio,the mechanical and degradation propertieswere systematically studiedand the internal mechanism was also revealed.The antibacterial properties of these composite adhesives were also evaluated.Under the alkaline condition of NaHCO₃,dopamine was successfully grafted to the polyaspartic acid through the ring-opening reaction of PSI and dopamine.The chain structure of the PLASP-DA polymer was confirmed by FTIR and ¹H-NMR spectra.The GPC results showed that the molecular weight of the PLASP-DA polymer initially increased and then decreased with the increase of alkali concentration.The UV-spectrum analysis showed that the grafting ratio of dopamine in the PLAPS-DA polymer could reach 9.50%under different hydrolysis conditions.The composition of the cross-linking system had a great influence on the gelling time of the composite adhesive.The addition of MgO and HA nanoparticles decreased the gelling time of the adhesive and the influence of MgO nanoparticles on the gelling time was more significant than that of HA nanoparticles.The gelling time of the composite adhesive varied from a few seconds to hundreds of seconds through adjusting the composition of the cross-linking system.The addition of nanoparticles had little effect on the gel content while decreased the swelling ratio of the composite adhesive.The tensile test results showed that the addition of MgO nanoparticles could significantly improve the tensile properties of the composite adhesive.The elastic modulus,tensile strength and the elongation at break of the composite adhesive increased with the addition of MgO nanoparticles.However,the tensile properties decreased with further addition of HA nanoparticles.The bond strength test results showed that the addition of MgO and HA nanoparticles could apparently enhance the bond strength of the composite adhesive.The bond strength of the PLASP-DA/MgO composite adhesive reached the maximum of713.0KPa when adding 4wt%MgO nanoparticles of the second group on the gelatin substrate.The addition of MgO nanoparticles decreased the degradation rate of the composite adhesive while the addition of HA nanoparticles improved it.The antibacterial experiment results showed that the composite adhesive with MgO nanoparticles had obvious antibacterial effect on E.coli and S.aureus and the antibacterial ratio was almost 100%when adding 8wt%MgO nanoparticles.