Abstract
Portable systems for detecting biomolecules have attracted considerable attention, owing to the demand for point-of-care testing applications. This has led to the development of lab-on-a-chip (LOC) devices. However, most LOCs are developed with a focus on automation and preprocessing of samples; fluorescence measurement, which requires additional off-chip detection instruments, remains the main detection method in conventional assays. By incorporating optical biosensors into LOCs, the biosensing system can be simplified and miniaturized. However, many optical sensors require an additional coupling device, such as a grating or prism, which complicates the optical path design of the system. In this study, we propose a new type of biosensor based on gradient waveguide thickness guided-mode resonance (GWT-GMR), which allows for the conversion of spectral information into spatial information such that the output signal can be recorded on a charge-coupled device for further analysis without any additional dispersive elements. A two-channel microfluidic chip with embedded GWT-GMRs was developed to detect two model assays in a buffer solution: albumin and creatinine. The results indicated that the limit of detection for albumin was 2.92 μg/mL for the concentration range of 0.8–500 μg/mL investigated in this study, and that for creatinine it was 12.05 μg/mL for the concentration range of 1–10,000 μg/mL. These results indicated that the proposed GWT-GMR sensor is suitable for use in clinical applications. Owing to its simple readout and optical path design, the GWT-GMR is considered ideal for integration with smartphones or as miniaturized displays in handheld devices, which could prove beneficial for future point-of-care applications.
Highlights
Label-free (LF) biosensors that can directly measure the concentration of target analytes without the need for fluorescence labels have numerous uses, such as in the diagnosis of diseases, monitoring of the environment, development of drugs, and the detection of biological warfare agents and chemicals [1,2]
The results indicated that the gradient waveguide thickness guided-mode resonance (GWT-guided-mode resonance (GMR)) sensor achieves an limit of detection (LOD) of 2.92 μg/mL for albumin for the concentration range of 0.8–500 μg/mL investigated in this study
We demonstrated that our proposed GWT-GMR sensor is capable of detecting albumin with an LOD of 2.92 μg/mL within a concentration range of 0.8–500 μg/mL, and that it is capable of detecting creatinine with an LOD of 12.05 μg/mL within a concentration range of 1–10,000 μg/mL
Summary
Label-free (LF) biosensors that can directly measure the concentration of target analytes without the need for fluorescence labels have numerous uses, such as in the diagnosis of diseases, monitoring of the environment, development of drugs, and the detection of biological warfare agents and chemicals [1,2]. Several optical devices have been employed as LF biosensors, including photonic crystals [5,6] and ring resonators [7]; LF biosensors that make use of phenomena such as surface plasmon resonance (SPR) [8], localized surface plasma resonance [9], and guided-mode resonance (GMR) [10,11] have been developed. Among these phenomena, SPR has been the most widely used in LF biosensors. GMR-based biosensors, which have a high resolution and simple readout design, have been widely investigated by researchers and commercialized by several companies as components of desktop systems for high-throughput applications [12]
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