Insulation by Solution 3-Mercaptopropyltrimethoxysilane (MPS) Coating: Effect of pH, Water, and MPS Content

Abstract

We have investigated the effect of 3-mercaptopropyltrimethoxysilane (MPS) concentration, water content, and pH on the thickness and insulation quality of a MPS coating layer on a gold electrode obtained in an MPS solution in ethanol. We showed that controlling the MPS concentration, water content, and pH were all important for the insulation coating. With 1% MPS and 0% water, the coating rate remained well below 1 nm/h at all pH and at 2 and 8 nm/h in 0.1% MPS with 0.5% water at pH 9 and in 1% MPS with 1% water at pH 9, respectively. Furthermore, the surface of the MPS coating obtained with 0.1% MPS and 0.5% water at pH 9 was smooth for optimal binding surface stress induced detection resonance shift in a piezoelectric plate sensor. The width-mode resonance frequency of a piezoelectric plate sensor insulated with a MPS coating obtained in 0.1% MPS with 0.5% water at pH 9 for 36 h was shown to be stable for more than 24 h in a phosphate buffered saline solution.

Quartz‐crystal Microbalance Measurements of CD19 Antibody Immobilization on Gold Surface and Capturing B Lymphoblast Cells: Effect of Surface Functionalization

“…The condensation of MPS in aqueous ethanol solution at high pH provides that the functionalized sensor surface is more compact than the coating with non‐condensed MUA . In the study of Oh et al ., it was reported that Protein G molecules in a solution form cloud‐like structures, and they are adsorbed onto a bare Au surface as a clustered pattern .…”

“…Even though MPS coating results in a uniform protein G layer on the sensor surface, the BSA layer on MPS and pH reduces the cell binding. Also MPS is pH, coating repetition and time sensitive that makes it difficult to control the surface uniformity .…”

“…Method B uses the formation of MPS self assembled monolayer on gold surface , then for activation of the surface Sulfo‐SMCC linker layer was formed. The main steps of the immobilization procedure are: …”

“…At appropriate conditions, those processes could be controlled to provide adequate electrical insulation, favorable surface morphology and chemistry for sensors used for bio‐detection in ionic bio‐fluids. The condensed layer of MPS on a piezoelectric sensor measuring binding surface stress induces detection resonance shift, and enables optimal binding on a structurally smooth surface .…”

Enhancing detection sensitivity of piezoelectric plate sensor by increasing transverse electromechanical coupling constant

“…For electrical insulation, we followed an optimized wetchemical deposition method developed by Soylu et al 43 First, a PEPS was cleaned in a 1-in-40 diluted piranha solution (piranha solution is a 3:1 mixture of sulfuric acid and 30% hydrogen peroxide) for 10 min followed by de-ionized (DI) water and ethanol rinsing. It was then soaked in a 0.1 mM mercaptopropyltrimethoxysilane (MPS) (Sigma) solution in ethanol (Fisher) with 0.1% DI water for 30 min followed by soaking in a 0.1% MPS solution in ethanol with 0.5% DI water at pH 9 for 48 h where the MPS solution was replaced with a fresh one every 12 h. For each MPS solution replacement, the PEPS was first rinsed with DI water and followed by ethanol before immersing in a fresh MPS solution.…”