Fundamental properties of transition metal complex doped-calcium phosphate/porous silicon/silicon structures

Abstract

Silicon is typically not regarded as a promising biomaterial due to its poor biocompatibility. The demonstration of the growth of hydroxyapatite (the mineral phase of bone, Ca 10 (PO 4 ) 6 (OH) 2 ) on porous Si/Si substrate in 1995 has altered its potential landscape as a biomaterial. In this work, the incorporation of cis-platin (cis-diamminedichloroplatinum(II)), carbo-platin ([cis-diammine(cyclobutane-1,1-dicarboxylato]platinum(II)), and Pt(en)Cl 2 (ethylenediam mine dichloro platinum (II)) within layers of calcium phosphate on porous Si/Si structures have been investigated. In this context, one could visualize the construction of an electrically responsive biocompatible Si device capable of localized drug delivery. The influence of initial platinum concentration in the deposition process, the effect of thermal heating of the calcium phosphate/porous Si matrix, and the effect of varying the coordination sphere of Pt complexes on their ability to diffuse into the surroundings have been evaluated. Selected Ru complexes (i.e., [Ru(bpy) 3 ]Cl 2 , [Ru(phen) 3 ]Cl 2 , etc.) can also be incorporated within calcium phosphate/porous Si/Si. Upon solvent exposure, the effect of thermal heating of the doped calcium phosphate/porous Si/Si matrix was investigated by monitoring the emission of the complexes originating from the calcium phosphate surface and from the solution. One can also alter the amount and rate of Ru complex delivered to the surroundings by applying anodic bias on the PS/Si. Loading of the complex in the calcium phosphate can be adjusted by varying the duration of cathodic bias during the deposition process. In order to achieve immobilization of the Ru complex in the calcium phosphate for possible application of this type of material as a Si-based DNA biosensor, the effect of varying the coordination sphere of a series of Ru complexes (i.e., Ru(bpy) 3 2+ , Ru(bpy) 2 Cl 2 , Ru(bpy) 2 (O 3 SCF 3 ) 2 ) on their diffusion have been examined. It is also important to understand how the diffusion of the complexes can be affected by their interactions to their perceived biological targets (i.e., DNA) for any applications of these material in drug delivery systems or biosensing. Results show that the addition of a large excess of DNA into a [Ru(phen) 3 ]Cl 2 -doped calcium phosphate/porous Si/Si structure in water causes the diffusion of [Ru(phen) 3 ]Cl 2 from relatively deep regions of the calcium phosphate layers into the surroundings.