Phosphonate based organosilane modification of a simultaneously protein resistant and bioconjugable silica surface

Abstract

A facile method to coat silica surfaces with THPMP is introduced, forming simultaneously a protein resistant and bioconjugable surface.The coating is experimentally identified and its anti-fouling and bioconjugable characteristics are demonstrated.Chemical modication of surfaces, which enables unprecedented manipulation of the characteristics of materials, can be attained by a virtually indenite number of different compounds and methods. Regarding the accommodation of molecules over surfaces, self-assembly strategies depending on spontaneous interactions of the molecules with the surface for the formation of mono-or multilayers are among the most frequently utilized. Self-assembly generally occurs via functional head groups having high affinity towards the substrate, anchoring the molecule covalently or non-covalently to the surface. Among various different head groups, silanes are particularly important and widely used, while the knowledge regarding their assembly is far more empirical, besides being practical. Silanes are assumed to form monolayers over the surfaces; yet this is a controversial issue since their assembly depends highly on the environmental conditions, obstructing the formation of lms with well-dened characteristics. Also polymerization frequently occurs during their assembly. 1The characteristics of a silane based coating depend on many factors such as density, 2 chain length and functional group.3 Having a coating with simultaneously more than one function thus represents a challenge for silane based molecules, since an alteration in one directly affects the nature of whole coating. Coating with more than one molecule is hypothetically possible, either simultaneously or sequentially. However, it is not practical to perform in every case due to easy polymerization and unpredictable assembly behavior of silanes. 1Here we propose an alternative strategy for realizing antifouling surfaces with bioconjugation capability by using only a single molecule for surface modication. We utilized THPMP, a commercial small silane-based molecule, to produce a bioconjugable and anti-fouling silica surface (see ESI † for details). Phosphonates have been used as functional groups stabilizing silica containing nanoparticles against aggregation 4 or sites for covalently anchoring primary amines to other molecules such as nucleic acids.5 Also, it has been shown previously that methylphosphonate containing silica nanoparticles exhibited signicantly reduced non-specic biological interactions, 6 and our research group has recently demonstrated that methylphosphonate conjugation particularly decreased protein adsorption on silica nanoparticles.7 However, to the best of our knowledge, neither the characteristics of these phosphonatebased lms were investigated in detail, nor were their bioconjugation properties utilized together with their protein resistant characteristics. In this study, we experimentally characterized the THPMP lm, and examined it regarding its protein resistance and bioconjugation characteris...

Real-Time and Selective Detection of Single Nucleotide DNA Mutations Using Surface Engineered Microtoroids

“…The C 1s scan of an APTES/TMMS coated microtoroid showed three peaks located at 286, 285, and 284 eV verifying C−N, 31 C−C 32 and C−H, 32 and C−Si 33 bondings, respectively, due to covalent bonding of APTES/TMMS molecules ( Figure S7). Also, the O 1s peak located at 530.5 eV 34 and the increase in intensity of the higher energy Si 2p peak after coating, verifies the Si−O bonding. 35 N 1s scan showed two peaks at 401.6 and 399.2 eV arising from protonated amine (−NH 3 + ) and free amine (−NH 2 ) groups 36,32 due to covalent conjugation of APTES molecules, respectively.…”

Label-Free Biosensing with High Selectivity in Complex Media using Microtoroidal Optical Resonators

“…Recently, we have suggested that coating of an organosilane molecule having methylphosphonate functional group could be used to form a simultaneously protein resistant and bioconjugable silica surface 24 . In this article, we demonstrate, for the first time, that this multifunctional coating could indeed solve the aforementioned problem of biosensing with the WGM microresonators by enabling recognition of antigens after functionalization of microtoroids with corresponding antibodies with high sensitivity in complex media and also by suppressing non-specific interactions simultaneously.…”

“…The Q measured here is 3.95 × 10 6 . Microtoroids were first coated with 3-(Trihydroxysilyl) propyl methylphosphonate (THPMP), which forms an anti-fouling layer over silica surfaces, using a slightly modified recipe than we used in our previous research 24 (Methods). Piranha cleaned and THPMP coated microtoroids were compared regarding non-specific adsorption of albumin–fluorescein isothiocyanate conjugate (FITC-BSA) by confocal microscopy.…”

Label-Free Optical Biodetection of Pathogen Virulence Factors in Complex Media Using Microtoroids with Multifunctional Surface Functionality

“…The R q value for the bare SiO 2 surface was obtained as 0.45 nm, in agreement with our previous report. 35 The corresponding line profile of the 2D image, shown with a blue line, was given in Figure 1F, demonstrating a smooth SiO 2 surface. As can be seen in the 3D AFM image of the α-Exotoxin A functionalized surface ( Figure 1E) and in the corresponding line profile (Figure 1G), the surface roughness was increased apparently and the R q value was calculated as 1.24 nm.…”

“…One strategy for eliminating such lower spectral shifts is by creating biointerfaces which suppress only the nonspecific interactions, while not interfering with the biodetection ability. As a step forward in achieving this task, we previously demonstrated a surface modification approach, using 3-(trihydroxysilyl) propyl methylphosphonate (THPMP) molecules, 35 for selective human interleukin 2 antigen sensing in a diluted fetal bovine serum. 36 In this study, using the same surface modification approach, we performed optical biodetection of Pseudomonas aeruginosa exotoxin A in a diluted artificial sputum medium, prepared by mimicking the respiratory environment of Cystic Fibrosis (CF) patients.…”