Research On Fabrication Of Hydrophobic Drug Microencapsules By Layer-by-layer Assembly And Their Release Property

Layer-by-layer (LBL) assembly method with the advantage of versatility, simplicity and easy operation was widely applied, because the thickness, structure and function of films obtained were controllable. The study of microencapsulated drugs by using LBL technique was very active. Thus the basic research of LBL has received considerable interest.In this paper, the alternate assembly of poly (dimethyldiallyl ammonium chloride) (PDDA), poly (styrene sulfonate) (PSS), chitosan lactate (CHI), quaternary chitosan salt were studied. Influence of assembling condition on the properties of the multilayer membrane was investigated with ultraviolet spectrometer (UV), atom force microscope (AFM) and Contact Angle meter.Layer-by-layer self-assembled membranes of poly (styrene sulfonate) (PSS) and poly (dimethyldiallyl ammonium chloride) (PDDA) with a wide concentration range of polyelectrolytes were prepared at different concentrations of sodium chloride. The relation between ultraviolet (UV) absorbance of the self-assembled membrane and the solution concentrations of polyelectrolyte (Cp) and added salt (Cs) in the layer-by-layer processes was investigated. It was found that the UV absorbance (A) exhibited increasing, constant and decreasing trend with increasing C_P respectively, which depended on added salt concentration; furthermore, most A^C_P curves displayed a discontinuous phenomenon, which was related to the critical concentration of the polyelectrolyte in solution. So the solution concentrations of polyelectrolyte (C_P) and added salt (Cs) affected the assembed amount of polyelectrolyte in the membrane.Layer-by-layer self-assembled membranes of PDDA/PSS and CHI/PSS were prepared at different concentrations of added alcohol, that its concentration was expressed as C_alcohol. The UV absorbance of according multilayer prepared from these solutions was also expressed as A. Each of the intrinsic viscosity ([η])^C_alcohol curve has maximum point, at the same time, each of the A^C_alcohol curve has minimum point. When C_alcohol is same, the maximum point of [η ]^C_alcohol curve is near to the minimum one of A^C_aloohol curve.