Biomimetic Bone Tissue Engineering Substrate Materials Based On Poly(D,L-Lactic Acid) Modifications

"Biomimetic modification or engineering of materials"is a new requirement of the third-generation biomaterials. Here, poly(D,L-lactic acid) (DL-PLA) with high molecular weight was prepared from D,L-lactide and modified in the bulk through a series of chemicals with the purpose of overcoming the drawbacks of DL-PLA in clinical use and building novel DL-PLA based biomimetic extracellular matrix materials. The characterization of the obtained polymers was by the means of multi-angle laser light scattering (MALLS), fourier transform infrared spectrometry (FTIR), nuclear magnetic resonance spectrometer (NMR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimeter (DSC), amino acid analyzer (AAA) and classical chemical analysis to explore the structures and the properties. Thereafter, surface wettability, biodegradation and biocompatibility of the synthetic materials were investigated. The main works and conclusions are included as follows:â‘´Poly(D,L-lactic acid) with high molecular weight was synthesized by melt ring-opening polymerization of D,L-lactide using a novel co-initiating system. Then, an extensive investigation effort was expended in understanding the reacting mechanism, the effects of coinitiator and its dosage towards the molecular weight.â‘ FTIR, ¹³C NMR, ¹H NMR and XPS analysis showed that DL-PLA was successfully prepared by using above-mentioned co-initiating system. Glass transition temperature of the synthetic polymer determined by DSC was 63.6℃.â‘¡The results of MALLS analysis indicated that the co-initiating system could accelerate the polymerization rate and shorten the reacting time. Moreover, decreasing the concentration of coinitiator in reacting system yielded polymer with higher molecular weight and narrower polydispersity.â‘¢Regression analysis revealed the maximal Mw of DL-PLA was only 116,600 by using single Sn(Oct)2 initiating system. However, sigmoidal fit discovered that the ultimate Mw of polymer prepared from co-initiating system was 153,300. Therefore, by controlling the initiator and coinitiator dosage into the optimum range, DL-PLA with maximum molecular weight was obtained.⑵Based on the design strategy of"bulk biomimetic modification or engineering of materials", poly(D,L-lactic acid) was modified in the bulk with maleic anhydride (MA), aliphatic diamine (DA) and bioactive peptide Arg-Gly-Asp-Ser (RGDS),...