Chemical stabilization of porous silicon for enhanced biofunctionalization with immunoglobulin

Abstract

Porous silicon (PSi) is widely used in biological experiments, owing to its biocompatibility and well-established fabrication methods that allow tailoring its surface. Nevertheless, there are some unresolved issues such as deciding whether the stabilization of PSi is necessary for its biological applications and evaluating the effects of PSi stabilization on the surface biofunctionalization with proteins. In this work we demonstrate that non-stabilized PSi is prone to detachment owing to the stress induced upon biomolecular adsorption. Biofunctionalized non-stabilized PSi loses the interference properties characteristic of a thin film, and groove-like structures resulting from a final layer collapse were observed by scanning electron microscopy. Likewise, direct PSi derivatization with 3-aminopropyl-triethoxysilane (APTS) does not stabilize PSi against immunoglobulin biofunctionalization. To overcome this problem, we developed a simple chemical process of stabilizing PSi (CoxPSi) for biological applications, which has several advantages over thermal stabilization (ToxPSi). The process consists of chemical oxidation in H 2 O 2 , surface derivatization with APTS and a curing step at 120• C. This process offers integral homogeneous PSi morphology, hydrophilic surface termination (contact angle θ = 26• ) and highly efficient derivatized and biofunctionalized PSi surfaces (six times more efficient than ToxPSi). All these features are highly desirable for biological applications, such as biosensing, where our results can be used for the design and optimization of the biomolecular immobilization cascade on PSi surfaces.

Surface Wettability of Oxygen Plasma Treated Porous Silicon

“…Surface chemical bonding modifications induced by oxygen plasma are discussed. A simple empirical model is developed to study the possible reaction kinetics on p-Si surface with a view to establishing a first model which can be potentially exploited in applications such as biosensors and drug delivery, where precise controls of p-Si surface wetting properties are required [4,21,22].…”

Nanoporous silicon-based surface patterns fabricated by UV laser interference techniques for biological applications

“…Surface functionalization was performed by the immersion of the nanoPS in aminopropyltriethoxysilane (APTS):toluene (2:1000) solutions for 15 min. In this process, the presence of SiO 2 on the surface of nanoPS (formed by the oxidation as a result of stabilization process), reacts with the APTS-based solution leading to a large surface density of amino groups [21]. It is worth mentioning that amino groups were selected for this study given…”

Biofunctional porous silicon micropatterns engineered through visible light activated epoxy capping and selective plasma etching

“…Relevantly, recent reports have demonstrated that oxidation of PSi can be catalyzed upon exposure to visible light, leading to an increase of free electrons at the PSi interface, which can efficiently reduce metals [13]. Here we propose that the electron density induced upon light activation can catalyze the heterogeneous condensation reactions of (3-glycidyloxy-propyl)-trimethoxy-silane (GPTMS) with the surface of the oxidized PSi, avoiding previous thermal or chemical oxidation [12]. Epoxy groups in GPTMS are able to react with different nucleophilic groups providing strong linkages not drastically altering protein function [14], which is exploited to develop protocols for enzyme immobilization.…”

“…Assembly has been previously proposed by visible light activated hydrosilylation (reaction between hydrogen-terminated silicon and molecules containing double bonds) [9,10] but surface modification with organosilane assemblies allows diversifying the chemical functionalities and provides biomolecular selectivity [11]. Relevantly, the assembly of organosilanes on PSi surfaces requires a previous oxidation that has been traditionally promoted by thermal process or peroxidation [12].…”