Preparation Of Polylactic Acid And Modified Polylactic Acid Nanofibes Via Electrospinning Technology

Polylactic acid (PDLLA) is a kind of medical macromolecular materials with good biodegradability and biocompatibility. It has been extensively applied in bone repairing and fixing, drug releasing system, and systematization project. But PDLLA is one kind of polyester, lacking of hydrophilic groups in its structure, and its surface is strong hydrophobic, as will badly influence its appetency with cells, and could restrict PDLLA's application in medical field. Therefore, in this article, we studied the modified PDLLA by maleic anhydride (MAH). By introducing active anhydride group on PDLLA, maleic anhydride modified PDLLA (MPDLLA) was prepared and the synthesization technologies were optimized. The performance and structures of PDLLA and MPDLLA were tested.We prepared PDLLA nanofibrous membrane by electrospinning was prepared. The process parameters, including electrostatic voltage, solution concentration, collection distance, aperture of injector nozzle, temperature and conductance, affect electrospinning, were analyzed detailedly. The basic reason of influencing on electrospining from intermolecular force, electric field force, surface tension and so on were analyzed.To our best knowledge, on report on the preparation of MPDLLA nanofibrous membrane has been found yet. We successfully prepared MPDLLA nanofibrous membrane and observed it under scanning electron microscope. Compared with PDLLA nanofibrous membrane, the arrangement of MPDLLA nanofibrous membrane is more confusion. Also, MPDLLA nanofiber is thinner than PDLLA nanofiber, which may have something to do with its fine hydrophilicity.As nanofibrous membrane, it should have much more three-dimensional bore structure, higher porosity, comparative stability and certain mechanical property. So for PDLLA nanofiber and MPDLLA nanofibrous membrane, it is necessary to carry on some evaluation in vitro in these aspects. In this paper, we try to study PDLLA nanofiber and MPDLLA nanofibrous membrane in contact angle, porosity, mechanics property and degradation completely. Moreover, we make a comparison between the two, and at the same time compare them with their casting membrane respectively. The measurement of porosity indicates that the porosity of MPDLLA is big (88.1%); and that of PDLLA is small (83.7%), showing that the contact angle of MPDLLA nanofibrous membrane is obviously smaller than that of PDLLA nanofibrous membrane. This explains that the hydrophilicity of MPDLLA nanofibrous membrane is better than PDLLA nanofibrous membrane. The measurement of viscosity shows that the molecular weights of these four kinds of materials reduce continuously because of degradation. At the same time during immersing, the loss of viscosity of the four materials is greater than that of weight. In weight loss aspect, both nanofibrous membrane and casting membrane are not big, which may be because the diffluence of degradation product is getting behind with the hydrolysis of PDLLA molecule. When PDLLA begins to degrade, PDLLA macrochain breaks off gradually first because of hydrolysis. But the start of hydrolysis does not mean weight loss begins. Just when the hydrolysis reaches to a certain extent, small member materials coming from degradation begin to dissolve out. So it appears that the loss of viscosity is greater than that of weight.PDLLA electrospinning membrane and casting membrane are different in structure, resulting in difference in their degradation. However, judged by the change in intrinsic viscosity, casting membrane reduces more quickly than spinning scaffold. It proves that the degradation of casting membrane is faster than electrospinning membrane, which can be explained by the diffluence mechanism of degradation product and the autocatalysis mechanism during the degradation of PLA. Lactic acid, which is the degradation product of PDLLA, has autocatalytic action to the degradation of PLA. It is called autocatalytic action of PLA. Because the degradation product from casting membrane liberates to solution more slowly than porous spinning framework, PLA content in non-spinning membrane is higher than in spinning scaffold. Under the same condition, the PDLLA molecular participating in hydrolysis in non-spinning membrane is more than that in spinning scaffold, so the intrinsic viscosity of non-spinning reduces more quickly.Whether casting membrane or electrospinning membrane, the viscosity of MPDLLA reduces more quickly than PDLLA. It proves no matter what structure it is; the degradation rate is quicker than PDLLA obviously.In this paper, we first carried out electrospinning nanofiber s load to gatifloxacin carries and releases successfully. See as a result from the SEM images, the distribution of PDLLA nanofiber loading 15% gatifloxacin is more uniform than that without drug. From 25000 times SEM images, we found the surface of PDLLA nanofiber loading 15% drug is very smooth, and there is no grain within the fiber. We finished the drug encaplated inside the electrospinning nanofiber. Then we further studied drug release in vitro of the electrospinning nanofiber-loading drug.