Abstract
A new and facile approach to selectively functionalize the internal and external surfaces of porous silicon (pSi) for drug delivery applications is reported. To provide a surface that is suitable for sustained drug release of the hydrophobic cancer chemotherapy drug camptothecin (CPT), the internal surfaces of pSi films were first modified with 1-dodecene. To further modify the external surface of the pSi samples, an interlayer was applied by silanization with (3-aminopropyl)triethoxysilane (APTES) following air plasma treatment. In addition, copolymers of N-(2-hydroxypropyl) acrylamide (HPAm) and N-benzophenone acrylamide (BPAm) were grafted onto the external pSi surfaces by spin-coating and UV crosslinking. Each modification step was verified using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, water contact angle (WCA) measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). In order to confirm that the air plasma treatment and silanization step only occurred on the top surface of pSi samples, confocal microscopy was employed after fluorescein isothiocyanate (FITC) conjugation. Drug release studies carried out over 17 h in PBS demonstrated that the modified pSi reservoirs released CPT continuously, while showing excellent stability. Furthermore, protein adsorption and cell attachment studies demonstrated the ability of the graft polymer layer to reduce both significantly. In combination with the biocompatible pSi substrate material, the facile modification strategy described in this study provides access to new multifunctional drug delivery systems (DDS) for applications in cancer therapy.
Highlights
Selective modification on porous silicon (pSi) outer surfaces was first reported by Cunin and coworkers[31]
Exploring a drug delivery systems (DDS) composed of pSi and a polymer with antifouling properties is desirable as the fate of biomaterials can be adversely affected by non-specific protein adsorption and cell attachment when applied in vivo
PSi films were first hydrosilylated with hydrocarbon chains, treated with air plasma, which was expected to remove the organic species on the top surface of pSi and leave behind a thin oxide layer
Summary
De-Xiang Zhang[1,2], ChiakiYoshikawa[2,3], Nicholas G. A three step functionalization procedure consisting of two hydrosilylation reactions separated by the selective etching of the external surface was described This procedure provides the outer pSi surface with hydrophilic groups while restricting hydrophobization to the inner pore walls, which was demonstrated by angle-resolved X-ray photoelectron spectroscopy (XPS) using pSi macro pores[35]. PSi films were first hydrosilylated with hydrocarbon chains, treated with air plasma, which was expected to remove the organic species on the top surface of pSi and leave behind a thin oxide layer This was followed by silanization and loading with the hydrophobic drug camptothecin (CPT). The CPT was loaded into the pores of the pSi matrix by physical adsorption and the release kinetics was adjusted by both hydrophobic inner pore wall modification and the grafting of an outer polymer barrier. Protein adsorption and cell attachment experiments were conducted to evaluate the antifouling properties of the outer polymer coating on pSi surfaces
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