Adsorption/desorption characteristics of cis-platin on mercapto-silylated silica surfaces

High-dose cancer treatment with cis-platin (CP, cis-[Pt(NH3)(2)Cl-2]), alth ough of therapeutic value, is limited by its toxicity. Fast removal of exce ss drug shortly after administration and site-specific drug release are pot ential partial solutions of this problem. As a first stage toward these sol utions, several adsorption/desorption properties of CP have been determined and analyzed. The main adsorbent selected for this study was silica silyla ted with (3-mercaptopropyl)trimethoxysilane (MPTS). The properties of this mercapto-derivatized silica (SiSH) were compared with an organically modifi ed silica sol-gel material (Ormosil) using MPTS as modifier and with nonder ivatized silica (SiOH). Although Langmuirian at first glance, a more detail ed analysis of the adsorption isotherm of the CP/SiSH system revealed a coo perative mechanism of adsorption, namely, an increase in adsorption affinit y with coverage. This cooperativity was detected by employing a coverage-de pendent adsorption-equilibrium constant. Active shifting of the adsorption equilibrium toward the desorption side was achieved with 2,3-dimercapto-1-p ropane sulfonic acid sodium salt in solution. On the basis of the differenc es in adsorption affinities between SiSH and SiOH, we demonstrated, we beli eve for the first time, the ability to achieve interparticle migration of a n adsorbate (CP) from one matrix to another.