The Preparation Of CS/PVP-Calcium Alginate Composite Medical Dressing

Medical dressings can play a temporality barrier function in wound healing, which can protect the wound, control wound infection and provide a good environment to heal wound. With the increasing of burns and chronic unclear wound, the demand for medical dressings is getting greater.In this article, the two-layer structure dressing consist of CS/PVP film and calcium alginate porous sponge was prepared. CS/PVP film can separate wound area and hydrophilic sponge from external environment, forming wet micro-environment which is conducive to wound healing. Calcium alginate porous sponge used as internal layer has three-dimensional reticulated and porous structure which provides place for cell adhesion, proliferation and differentiation and it also has good biocompatibility and biodegradation. The microstructure, degree of crystallinity, tensile strength, water absorption rate of CS/PVP film were tested by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), universal testing machine. The microstructure, cross-linking, water absorption, tensile strength, volume expansion ratio of alginate calcium were tested by SEM, FTIR, universal testing machine. Mechanical property, water absorption rate and peel strength were determined to research best curing time and temperature. The main research contents and results as follows:A new stereolithography method, acid-base neutralization titration followed by conventional papermaking process for the preparation of chitosan film has been introduced in this subject. Membrane solution volume, drying method and the way of titration process on the influence of film formation is discussed to determine the best process:25ml of membrane solution volume was prepared by way of needle tubing titration, natural drying. By scanning electron microscopy test, the CS/PVP film is of relatively uniform, smooth, dense structure, without macroscopic phase separation, showing good physical compatibility. Contact Angle test shows that both CS and PVP is hydrophilic material and proportional control can change its hydrophilicity. Its hydrophilic is better than pure CS membrane. CS membrane is qualitatively hard and brittle, while adding PVP improves the mechanical properties, becoming softer. It also shows the tensile strength of the dry film is greater than the tensile strength of the wet membrane. With the increase of PVP content, the tensile strength becomes increasingly greater. But when content reaches certain value, the membrane solution concentration is too heavy, which is not helpful for film formation. With the best ratio of CS and PVP is1:1, air permeability can be1842-13g·m-2·24h, moisture retention rate is26.82%, water absorption rate is36.65, showing the fact that composite film can absorb wound exudates easily, and has certain air permeability. With the freeze drying, the sodium alginate sponge reacts to form cross-linked calcium alginate sponge in calcium chloride solution quickly. The cross-linked sponge is of certain directed, regular layer and porous structure. In the process of gel reaction, with the increase of calcium ion concentration, equilibrium swelling degree is reduced, showing enhanced stability of the sponge. The moisture content of calcium alginate sponge is over90%, while the volume expansion degree is varied until the calcium ion concentration over0.6mo1/1. With the increase of calcium ion, the stability and mechanical properties improves.The two-layer dressing, like badge, is combined by CS/PVP film and porous calcium alginate sponge with hot melt adhesive. The best curing schedule is35℃for2hours.The peel strength of CS/PVP film made by best curing conditions is1.76N/cm, in conformity with the provisions of medical adhesive tape peel strength requirements in YY0418-0418. The water vapor rate of two-layer structure compound dressing is1759.79g/m2, slightly lower than that of CS/PVP film. Composite dressings water absorption rate averages21.22times, higher than that of CS/PVP film11.80and calcium alginate sponge10.94, and it shows that hot melt adhesive did not influence water absorption rate of compound dressing, the average tensile strength is1.88MPa, compared with CS/PVP film, the tensile strength of composite dressing is better than that of CS/PVP film.