In Situ Biomineralized Phosphorylated Poly(l-Glutamic Acid)/Sodium Alginate Injectable Hydrogels

Biomineralized hydrogels have attracted much attention as biomaterials for bone regeneration. In our research described here poly(L-glutamic acid) (PLGA) was activated by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysulfosuccinimide to prepare PLGA-NHS active ester, which was then reacted with adipic acid hydrazide (ADH) and phosphorylethanolamine (PA) to obtain phosphonic and hydrazide-modified poly(L-glutamic acid) (PLGA-ADH-PA). The Schiff base reaction between PLGA-ADH-PA and oxidized alginate (OALG) led to the formation of phosphorylated PLGA/ALG injectable hydrogels. The nano-hydroxyapatite (nHA)/PLGA/ALG composite hydrogels were obtained by in situ biomineralization of the phosphorylated PLGA/ALG hydrogels in simulated body fluid. The chemical structure and rheological properties of the hydrogels before and after mineralization, and the size and morphology of the nHA were studied. After biomineralization, the growth of HA with soaking time was detected at the surface and interior of the PLGA/ALG hydrogels. The average sizes of the nHA particles were 120 nm and 350 nm, respectively, at 12 h and 5 d. The amount of hydroxyapatite deposited increased with the increase of PA grafting degree. Compared with unmineralized hydrogels, the mechanical properties of the mineralized hydrogels were significantly improved.