Fabrication of Carboxylated Silicon Nitride Sensor Chips for Detection of Antigen–Antibody Reaction Using Microfluidic Reflectometric Interference Spectroscopy

Abstract

In this study, we report label-free detection of alpha-fetoprotein (AFP), which has been used as a biomarker for hepatocellular carcinoma, by a microfluidic reflectometric interference spectroscopy (RIfS) system adopting a simple halogen light source and an inexpensive silicon-based sensor chip. Introduction of carboxy groups on a silicon nitride sensor chip to immobilize anti-AFP monoclonal antibody (anti-AFP) was carried out simply by immersion in aqueous solution containing triethoxysilylpropylmaleamic acid bearing a carboxy group and a silanol group. The RIfS system with the anti-AFP-immobilized sensor chip was found to give a reversible response through 100 on/off cycles using a regeneration buffer with high reproducibility (coefficient of variation (CV) = 5.7%). The limit of detection (LOD) of AFP was 100 ng mL(-1), and the measurement range spanned 3 orders of magnitude. Furthermore, the sensor chip showed no cross-reactivity with human serum albumin, Immunoglobulin G, transferrin, or fibrinogen at 100 μg mL(-1) without the use of blocking reagents such as bovine serum albumin. Consequently, the proposed RIfS system is a potentially effective tool for biomarker detection and in vitro diagnostics.

Two-layer reflectometric interference spectroscopy-based immunosensing for C-reactive protein

“…Although the baseline noise was observed on the sensitive layer (Fig. 4a), the concentration-dependent increase of Δλ values upon CPR injections indicate that anti-CRP was successfully embedded by LPD, and CRP was recognized by the embedded anti-CRP, resulting in modulation of reflectance spectra [18][19][20][21]. By the LPD process in the presence of PL as a binder, and the binding activity toward CRP was remained because of preferable interaction between cationic charge located on a sensor chip and F c region of anti-CRP [7].…”

“…The interference layers have been fabricated by dry processes such as sputtering and vapour deposition using TiO 2 and SiN (n=2.0-2.5) on silicone substrates (n=3.5-5.5) [17][18][19][20][21]. Compared with the dry process, LPD can provide the layer with low costs and good energy efficiency, since the process proceeds in aqueous solution at room temperature and requires no special equipment [8].…”

RGD-Functionalized Fe3O4 nanoparticles for magnetic hyperthermia

“…A fine adjustment of the synthetic conditions allows for obtaining oleic acid and oleylamine capped magnetite nanoparticles with defined shapes and sizes [32]. These iron oxide nanoparticles dispersed in organic medium have been transferred into aqueous phase by ligand interchange using dimercaptosuccinic acid (DMSA) [33], N-(triethoxysilylpropyl)-maleamic acid (TESPMA) [34] and by adding poly(maleic anhydride-alt-1-octadecene) (PMAO) [35].…”

Surface patterned graft copolymerization of hydrophilic monomers onto hydrophobic polymer film upon UV irradiation

“…The images of the drops on the films were captured within five seconds of drop deposition to minimize error due to evaporation. The thickness of the p(MMA/DMAB) film was estimated from the wavelength shift of the minimum value in the reflectance spectra taken with a reflectometric interference spectroscopy system before and after spin‐coating using a Konica Minolta, MI‐Affinity LCR‐01 ,. XPS measurements were carried out using a Physical Electronics.…”