Abstract
This paper presents a compact spectral detection system for common fluorescent and colorimetric assays. This system includes a gradient grating period guided-mode resonance (GGP-GMR) filter and charge-coupled device. In its current form, the GGP-GMR filter, which has a size of less than 2.5 mm, can achieve a spectral detection range of 500–700 nm. Through the direct measurement of the fluorescence emission, the proposed system was demonstrated to detect both the peak wavelength and its corresponding intensity. One fluorescent assay (albumin) and two colorimetric assays (albumin and creatinine) were performed to demonstrate the practical application of the proposed system for quantifying common liquid assays. The results of our system exhibited suitable agreement with those of a commercial spectrometer in terms of the assay sensitivity and limit of detection (LOD). With the proposed system, the fluorescent albumin, colorimetric albumin, and colorimetric creatinine assays achieved LODs of 40.99 and 398 and 25.49 mg/L, respectively. For a wide selection of biomolecules in point-of-care applications, the spectral detection range achieved by the GGP-GMR filter can be further extended and the simple and compact optical path configuration can be integrated with a lab-on-a-chip system.
Highlights
Colorimetric and fluorescent assays are among the most popular techniques for quantifying target analytes in a liquid sample
To verify that the proposed detection platform (GGP-guided-mode resonance (GMR)/charge-coupled device (CCD) system) can detect both the intensity and peak wavelength, one fluorescent dye that is commonly used in the polymerase chain reaction for deoxyribonucleic acid (DNA) detection was tested
The results of the serial dilution tests in practical assays based on fluorescence-based and two colorimetric measurements revealed that the grating period guided-mode resonance (GGP-GMR)/CCD system achieved comparable sensitivity and limit of detection (LOD) results to those obtained of the commercial spectrometer
Summary
Colorimetric and fluorescent assays are among the most popular techniques for quantifying target analytes in a liquid sample. Such quantification has varied applications, including food safety, water quality monitoring, biomarker detection, and pathogen detection [1,2,3,4,5]. The intensity of a specific wavelength can be monitored to be correlated with the analyte concentration. Colorimetric assays, such as the commonly used enzyme-linked immunosorbent assay for biomolecule detection [9], typically measure changes in the color or intensity of a liquid sample through the reaction of reagents with the targeted analyte to produce colored products [2,9]. The absorbance at a specific wavelength can be correlated with the analyte concentration in the liquid sample
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