Adaptive interferometry of protein on a BioCD

Abstract

Adaptive spinning-disk interferometry is capable of measuring surface profiles of a thin biolayer with subnanometer longitudinal resolution. High-speed phase modulation in the signal beam arises from the moving surface height profile on the spinning disk and is detected as a homodyne signal via dynamic two-wave mixing. A photorefractive quantum-well device performs as an adaptive mixer that compensates disk wobble and vibration while it phase-locks the signal and reference waves in the phase quadrature condition (͞2 relative phase between the signal and local oscillator). We performed biosensing of immobilized monolayers of antibodies on the disk in both transmission and reflection detection modes. Single-and dual-analyte adaptive spinning-disk immunoassays were demonstrated with good specificity and without observable cross-reactivity. Reflection-mode detection enhances the biosensing sensitivity to one-twentieth of a protein monolayer, creates a topographic map of the protein layer, and can differentiate monolayers of different species by their effective optical thicknesses.

Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

“…Several different ways to establish quadrature have been developed. These include microdiffraction of the focused laser beam off the microstructures on the disk surface, 124 a phase-contrast configuration 125 that detects local changes in protein density, an in-line ͑IL͒ configuration 126 that detects the direct protein and disk surface topology, and an adaptive optical approach 127 that uses an adaptive beam mixer. All of the BioCD quadrature classes incorporate high stability as a fundamental and intrinsic component of the detection 22 by using a common-path configuration 24 in which both the signal and the reference waves are generated from the same location on the disk and share common paths to the detector.…”

Investigation on Optimally Performing Sensor Substrates through Bio-fouling of Immunoglobulin-Conjugated Gold Nanoparticles

“…In this respect, there are various kinds of sensors and sensing substrates that are employed for the detection of biomolecules under optimized conditions [6][7][8][9]. Among these substrates, gold (Au) and silica (SiO 2 ) are commonly utilized for sensor development due to their biocompatibility [10][11][12][13][14][15][16][17][18][19][20][21][22]. Indeed, several factors make Au a desirable material, including easy water dispersal, compatibility with surface functionalization, biological non-reactivity, and ability to be customized (i.e., uniform or different nano-sizes) [23][24][25][26][27].…”

High-speed spinning-disk interferometry on the BioCD for human diagnostic applications

“…The micro-diffraction class [1,5,6] uses microstructures on the disc in an approach that is closest to digital compact disks, but that converts the digital readout to a sensitive analog signal. The adaptive optical class [7,8] uses a nonlinear adaptive optical mixer [9,10] to phase-lock the signal and reference beams. The phase-contrast class of BioCD [11] uses differential phase contrast laser scanning to detect spatial gradients caused by protein binding.…”