TRANSPORT OF PHARMACEUTICALS THROUGH SILK FIBROIN MEMBRANE

The transport of pharmaceuticals through silk fibroin membranes has be en investigated. The membrane was prepared from Chinese cocoon. The pe rmeability coefficients of five kinds of pharmaceutical, i.e. 5-fluoro uracil (5FU), L-(+)-ascorbic acid (Vc), resorcinol (Res), sodium pheno lsulfonate (SPS) and benzyltrimethylammonium chloride (BTAC), were mea sured in the pH range from 3.0 to 9.0. The silk fibroin membrane was a n amphoteric ion-exchange membrane composed of both weak acidic and we ak basic groups. Membrane-potential measurements revealed that the iso electric point of the membrane was about pH 4.5. The positively charge d pharmaceutical, BTAC, was excluded from the membrane below the isoel ectric point. On the other hand, the negatively charged one, SPS, had a permeability that decreased as the pH increased. The neutral molecul e, Res, however, penetrated through the membrane independently of pH v alue over the measured pH range. In the case of 5FU and Vc, the permea bility coefficients decreased steeply above pH 7 and pH 4, respectivel y, because 5FU and Vc were negatively charged above pH 7 (pK(a) = 8.0) and pH 4 (pK(a) = 4.25), respectively.