Effect Of Incorporation Of Strontium Into Photocrosslinked Alginate Gels

Objective To Explore the changes of mechanical and biological properties of photocrosslinked alginate gels doped strontium ions.Materials and methods After methacrylated alginate(MA)to form photocrosslinked methacrylated alginate hydrogels(PMA),photocrosslinked alginate hydrogels chelated strontium ions(Sr-co-PMA)were prepared by soaking PMA in strontium ion solution of different concentrations(0,10,30,50,80 and 100mmol/L);then the swelling ratio,degradation and elastic modulus of the gels were measured,and the surface morphology and elements of the materials were analyzed by SEM and EDS,respectively.Fourier transform infrared spectrometer was used to analyze the functional group changes of the hydrogel,and Cytotoxicity of the hydrogels was tested using Live/Dead staining and CCK-8;MC3T3-E1 cells were seeded on the surface of photocrosslinked alginate gels that were incorporated with different concentrations of strontium ion for 4 hours,then Live/Dead staining was used to observe cell adhesion,and Live/Dead staining was also used to determined cell spreading on the third day of the cell culture.Cell proliferation within the hydrogel was also tested.The cell osteogenesis in vitro was observed by alizarin red staining and Von Kossa staining;alkaline phosphatase activity of the cells in the hydrogel was tested using an alkaline phosphatase kit and a BCA protein kit.Results(1)Scanning electron microscope showed that the density of photocrosslinked alginate gels increased and the pore size decreased with the increase of strontium ion concentration.(2)From the EDS,the strontium content on the surface of the gels increased along with the augment of the strontium ion concentration.(3)FTIR indicates that the introduction of strontium ions does not alter the functional groups of photocrosslinked alginate hydrogels.(4)with the increase of strontium ion concentration,the swelling ratio of the hydrogels gradually decreased and the degradation was slower and slower while the elastic modulus of photocrosslinked alginate gels gradually increased.(5)Cytotoxicity tests show that the cells maintain high viability.(6)As strontium ion concentration increased,the early adhesion rate of MC3T3-E1 cells on the surface of photocrosslinked alginate gels showed an increasing trend,and the cell extension became better and better.(7)The results of Alizarin Red staining and Von Kossa staining showed that the mineralization matrix of the cells increased with the increase of the strontium ion concentration.(8)The alkaline phosphatase activity was tested,and found that the alkaline phosphatase activity increased with the augment of the concentration of strontium ions.Conclusion The results showed that the incorporation of strontium ions into the photocrosslinked alginate hydrogel can improve its mechanical properties and promote cell adhesion and osteogenic activity.Moreover,the mechanical and biological properties can be adjusted by changing the concentration of strontium ions.