Research Of Preparation And Properties Of Poly(L-glutamic Acid) Based Hydrogels

Hydrogels as tissue engineer materials have received extensive intrest of theresearchers, as its mechanical properties and structure are similar to manyextracellular matrix of organs. Poly (L-glutamic acid)(PLGA) is a syntheticpolyamino acids, it can mimic the protein composition of extracellular matrix. In thispaper, we prepared PLGA hydrogels by chemical cross-linking. However, themechanical properties of single polymer hydrogels is still poor. Hydroxyapatite (HA)is main inorganic component hard tissue of human, which has a good biologicalactivity, biocompatibility and bone conductibility, but it is brittle. Combination ofpolymer together with HA may solve these problems, at the same time it can mimicbone extracellular matrix components. Therefore, on the basis of fabrication ofPLGA hydrogels, we adopted the method of biomineralization to prepare PLGA/HAcomposite hydrogels and study its properties.1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC HCl) andadipic acid hydrazide (ADH) were used as the activator and cross-linking agentrespectively to prepare PLGA hydrogels. Forming mechanism of the hydrogels wasanalysised, the influence of different solid content and amount of crosslinking agentand activator were discussed. The SEM results showed the micropores oflyophilizated PLGA hydrogel were interconnected, and the diameters of which were50~200μm. The results of swelling degree, rheological properties and degradationperformance research indicated that with the increase of solid and EDC content,crosslinking degree increased, swelling degree decreased, degradation rate slowed,and composite modulus and viscoelastic modulus increased. However, with theincrease of ADH content, the swelling degree, degradation rate decreased first，andthen increased, while the mechanical properties showed opposite trend. When themole ratio of ADH to PLGA was0.325, the mechanical performance of PLGAhydrogels was the best. PLGA is a kind of anionic amino acids, the structure and physical and chemicalproperties make it easy to enrichment of calcium ions and induced HA crystalgrowth. PLGA hydrogels were chosen (6wt%, mole ratio of EDC to PLGA is1,ADH to PLGA is0.325) as a template, and were soaked in simulating bodyfluid(SBF) to mineralize. Finally, the PLGA/HA composite hydrogels were obtained.The influence of mineralization days and SBF concentration were studied. SEMresults showed that the compound hydrogels were uniformly covered with HAparticles both surface and inside. With the increase of soaking time or SBFconcentration, the HA content in PLGA/HA composite hydrogels increased, thethermal stability, thermal weightlessness rate were reduced and composite modulusincreased.Comparing the biological properties of PLGA hydrogels before mineralizationand mineralized for14days. Staining of cells, confocal microscope(CLSM) resultsshows cells inside hydrogels were distributed evenly, only a small amount of cellapoptosised after14days, which confirmed a good biocompatibility of hydrogels. Asmall amount of cells in hydrogels before mineralization growth in a group, whilecells in hydrogels mineralized for14days can survive and proliferate well. Theresult showed that the PLGA/HA composite hydrogels were benefit for cell adhesionand proliferation.