Chitosan/bovine serum albumin (BSA) ultrathin films were fabricated on modified quartz wafer through layer by layer deposition.The effects of experimental conditions, such as pH value, molecular weight of CS, ionic strength and polyanions coexisting in BSA solution, on the fabrication and the stability of films were investigated with a radio\|labeled method. The results show that the absorbed BSA is almost proportional to the number of assembly cycle except the first 2 cycles, and chitosan/BSA films are favorable to be fabricated in chitosan aq AcOH at pH=5.2 as compared with at pH=1.0. When two different molecular weight (MW) chitosans were used ( M η≈1.2×10 5, M η≈1.0×10 6), the lower MW chitosan adsorbs more BSA, but less stable ultrathin films are fabricated. Similar results were obtained that the amount of adsorbed BSA is higher but the films formed are less stable in water than in phosphate buffered saline (PBS). The adsorption of BSA is restricted greatly in the presence of poly(sodium styrene sulfonate) (PSS) mainly because of the competitive adsorption.
On the substrate of modified quartz, two kinds of self assembled ultra thin films were fabricated through layer by layer electrostatic deposition with diazoresin′s sulfonate(DRS) as the polyanion, and chitosan(CS) as the polycation. The self assembly process was monitored by UV Vis spectra and confirmed that the layer by layer deposition takes place regularly. The films obtained both from DRS, CS(CS/DRS film) and from DR, DRS, CS(DR/DRS/CS/DRS film) were photo sensitive. Under irradiation of ultraviolet light, the stability of the films towards polar solvents increases significantly. The kinetic study shows that the rate of the photodecomposition reaction of DR/DRS/CS/DRS films is higher than that of CS/DRS films and doesnt show the first order reaction for both films.
