Design of a core-shelled polymer cylinder for potential programmable drug delivery.

A cylindrical dosage form comprising a laminated composite polymer core and a hydrophobic polycarbonate coating was proposed for programmable drug delivery. In the core, poly[(ethyl glycinate) (benzyl amino acethydroxamate) phosphazene] was synthesized as drug-loaded layers for its strong pH-sensitive degradation (eroded after 1.5 days at pH 7.4 and more than 20 days at pH 5.0 and 6.0). Poly(sebacic anhydride)-b-polyethylene glycol or poly(sebacic anhydride-co-trimellitylimidoglycine)-b-poly(ethylene glycol) was selected as isolating layers for their good processing properties at room temperature and suitable erosion duration. The in vitro drug release studies of these devices were conducted under physiological conditions (pH 7.4). The results revealed that the model drugs (brilliant blue, FITC-dextran, myoglobin) could be released in typical pulsatile manner. Moreover, the duration time of drug release (24-40 h) and the lag time (18-118 h) could be separately regulated by the mass of polyphosphazene and the type or mass of polyanhydride. In this experiment, the cooperative effect of polyanhydrides and pH-sensitive degradable polyphosphazene was specially demonstrated, which offers a new idea to develop a programmable drug delivery system for single dose vaccine and other related applications.