Study On The Synthesis And Properties Of Collagen Peptide-Modified Poly(Lactic Acid)

Poly （lactic acid）（PLA） was widely used and recognized in the medical fields dueto favorable properties of biodegradability, renewability and biocompatibility, such asmedical surgical sutures, injection capsules and microspheres. However, there weresome defects in the properties of PLA. For example, a large number of ester bonds and asmall amount of hydrophilic and active groups on the straight-chain structure of PLAleaded to its hydrophobicity, which reduced its biocompability. Moreover, the relativelywide molecular weight distribution of PLA resulted in difficult controlled degradationcycle, which caused high local acidity. In order to overcome the above-mentionedperformance deficiencies of PLA and meet the better material requirements of somemedical fields, a great deal of modified works of PLA have been done.In this study, self-made PLA was used as raw materials, the collagen modified PLA（CPLA） was synthesized via acylation. Briefly, the carboxylic group （-COOH） at theend of PLA was acylated into acyl-chloric group （-COCl） with PCl₅or PCl₃as chloridereagent, then, short blocks of collagen were introduced into PLA. At the same time,three types of CPLA were prepared by chemical modification and physical blending.Two types of CPLA among these were synthesized by chemical modification withdicyclohexyl carbodiimide（DCC） as dehydrating agent and glutaraldehyde ascross-linking agent respectively. Then these three types of CPLA was compared withCPLA synthesized with PCl₅or PCl₃from aspects of material properties.The characterization of copolymers were studied by infrared spectroscopy （FTIR）and fluorescence spectroscopy and photoelectron spectroscopy（XPS） and differentialscanning calorimetry （DSC） and by ninhydrin. Analysis of FTTR, fluorescencespectroscopy, XPS and DSC showed that–NH2and–NH–absorption peaks in amidegroups appeared in the CPLA and the peak was most obvious in CPLA synthesized withPCl₅, CPLA had significantly emission spectra near510-550nm and excitation spectrain490-500nm and PLA had not spectra in relative position, element “N” was justdetected in CPLA rather than PLA, and only one glass transition temperature appearedon DSC curve of CPLA. These results all indicated that the hydrolyzed collagen hasgrafted on PLA successfully. And cell proliferation curves also show that the the cellproliferation rate of CPLA was always significantly higher than the PLA group.The hydrophilicity test showed that the contact angle of CPLA was61, smaller than PLA, while the water absorption was3.49%, significantly higher than PLA. Theintrinsic viscosity tests in degradation process showed that the degradation trend ofCPLA and PLA was basically same at the first three weeks. But the degradation trend ofCPLA was obviously more stable and more flat than PLA from the fourth week. Theweight loss test also showed that the same conclusion, in addition, there was noacid-catalyzed self-accelerating degradation behavior in the degradation process ofCPDLA.3T3cell compatibility tests showed the morphologies of cells attached toCPLA substratum were mostly short spindle and triangular observed by microscope.The cell density was high and most of cells linked up into pieces, the cell proliferationpromoted by CPLA was better than PLA and the control group.The results of this study showed that the hydrophilicity of CPLA synthesized byPCl₅method was significantly better than PLA, the degradation process of CPLA wasmore flat than PLA, and there was no acid-catalyzed self-accelerating degradationbehavior in the degradation process of CPLA. In addition, CPLA exhibited better cellcompatibility than PLA. Therefore, CPLA prepared by acylation was expected tobecome a new type of medical polymer materials.