Fourier spotting: a novel setup for single-color reflectometry

Abstract

Single-color reflectrometry is a sensitive and robust detection method in optical biosensor applications, for example for bioanalysis. It is based on the interference of reflected monochromatic radiation and is label free. We present a novel setup for single-color reflectometry based on the patented technology of Berner et al. from 2016. Tilting areas of micro-mirrors allow us to encode the optical reflection signal of an analyte and reference channel into a particular carrier frequency with the amplitude being proportional to the local reflection. Therefore, a single photodiode is sufficient to collect the signals from both channels simultaneously. A 180∘ phase shift in the tilt frequency of two calibrated micro-mirror areas leads to a superposition of the analyte and reference signal which enables an efficient reduction of the baseline offset and potential baseline offset drift. A performance test reveals that we are able to detect changes of the refractive index n down to Δn < 0.01 of saline solutions as regents. A further test validates the detection of heterogeneous binding interaction. This test compromises immobilized testosterone-bovine serum albumin on a three-dimensional layer of biopolymer as ligand and monoclonal anti-testosterone antibodies as analyte. Antibody/antigen binding induces a local growth of the biolayer and change in the refractive index, which is measured via the local change of the reflection. Reproducible measurements enable for the analysis of the binding kinetics by determining the affinity constant KA = 1.59 × 10− 7 M− 1. In summary, this work shows that the concept of differential Fourier spotting as novel setup for single-color reflectometry is suitable for reliable bioanalysis.

Interpol Review of Drug Analysis 2019-2022

“…2019 sensors for the detection of illicit drugs [ 1092 ]; electrochemical sensor for detection of clonazepam in pharmaceutical formulations [ 1093 ]; sensor for the detection of ephedrine in pharmaceutical samples [ 1094 ]; colorimetric aptamer-based sensor for visual detection of illicit drugs and toxins in various sample matrices [ 1095 ]; 2020 review of advancements in electrochemical detection of drugs of abuse [ 1096 ]; 2021 sensor for simultaneous determination of paracetamol, diclofenac, and tramadol [ 1097 ]; sensor for electrochemical determination of naloxone [ 1098 ]; 2022 review of the advances in the field of biosensors for the detection of commonly abused drugs, both prescribed (codeine and morphine), and illegal narcotics (cocaine) [ 1099 ]; a novel setup for single-color reflectometry optical biosensor applications [ 1100 ].…”