Preparation And Physicochemical Properties Of Sodium Alginate Based Composite Hydrogels

Alginate hydrogel is a natural anionic polymer polysaccharide,compared with other polymers,alginate hydrogel has many advantages,such as abundant sources,low cost,good plasticity and good biocompatibility.It is widely used in the study of injectable hydrogels.However,because of its poor bioactivity and poor mechanical properties,and how to improve its mechanical properties has always been the focus of research on alginate based hydrogels.In this paper,a dopamine-modified alginate hydrogel combined with bioceramics is designed,which is cross-linked via the in situ slow release of divalent ions by the hydrolysis of GDL.And its structure and physicochemical properties were also studied.In this paper,hydroxyapatite with different Sr substitution degrees was prepared by hydrothermal method.Through XRD phase characterization and crystal structure analysis,it was proved that this method can prepare the Sr substituted hydroxyapatite without impurity phase and had good high crystallinity.Through FTIR spectra analysis of the functional groups of the samples,it was found that the substitution of Sr²⁺for Ca²⁺affected the vibration of the anion group,resulting in the increase of the bond length of OH···O hydrogen bond in apatite,and the alignment of[PO₄]tetrahedron and the bond length of P-O bond were also affected;The morphology of the sample is observed by SEM and TEM,and it was found that the addition of strontium ions affects the crystal morphology of HA,which will change from rod shape to particle shape.When the substitution degree of strontium was 50%which the lattice distortion is the most serious,the particle shape was observed more obvious,and then with the increase of strontium substitution,the crystal shape gradually returned to rod shape.The surface area of HA50 was 73.07 m²/g and Sr HA was 33.77m²/g.Alg-DA was synthesized by the grafting of dopamine onto the alginate backbone by a carbodiimide coupling reaction,and its structure was characterized.Through the calibration curve,the grafting rate of dopamine was calculated and the value was15.2%.Dopamine-modified alginate hydrogel combined with bioceramics were cross-linked via the in situ slow release of divalent ions by the hydrolysis of GDL.Composite injectable hydrogel gelation mechanism was also studied.The compressive strength of this injectable hydrogel is enhanced by 4.6 times compared with that of the hydrogel without the addition of GDL,and the compressive strength is enhanced by 4.0 times compared with that of the unmodified alginate hydrogel at strain values ranging from 10%to 50%.The hydrogels combined with strontium hydroxyapatite exhibited a more compact,suitable pore size,with a three-dimensional network structure,and the particle size was 50-100μm.The gel performance and gelation time can be controlled by adjusting the concentration of GDL.This study provides a new idea for improving the mechanical properties of alginate based hydrogel materials,which can release calcium and strontium ions during the degradation process,and has good bone induction and bone conduction ability.It has broad application prospects in bone tissue regeneration engineering and drug release.