Highly Sensitive Photothermal Microfluidic Thread-Based Duplex Immunosensor for Point-of-Care Monitoring

Abstract

Herein, we successfully developed a thread-based analytical device (μTAD) for simultaneous immunosensing of two biomolecules with attomolar sensitivity by using a photothermal effect. A photothermal effect exploits a strong light-to-heat energy conversion of plasmonic metallic nanoparticles at localized surface plasmon resonance. The key innovation is to utilize the cotton thread to realize this sensor and the use of chitosan modification for enhancing the microfluidic properties, for improving the efficiency of photothermal conversion, and for sensor stability. The developed μTAD sensor consists of (i) a sample zone, (ii) a conjugation zone coated with gold nanoparticles bound with an antibody (AuNPs-Ab 2 ), and (iii) a test zone immobilized with a capture antibody (anti-Ab 1 ). The prepared μTAD is assembled in a custom three-dimensional (3D) printed device which holds the laser for illumination and the thermometer for readout. The 3D-printed supportive device enhances signal response by focusing light and localizing the heat generated. For proof of concept, simultaneous sensing of two key stress and inflammation biomarkers, namely, cortisol and interleukin-6 (IL-6), are monitored using this technique. Under optimization, this device exhibited a detection linear range of 2.0−14.0 ag/mL (R 2 = 0.9988) and 30.0−360.0 fg/mL (R 2 = 0.9942) with a detection limit (LOD) of 1.40 ag/mL (∼3.86 amol/L) and 20.0 fg/mL (∼950.0 amol/L) for cortisol and IL-6, respectively. Furthermore, the analysis of both biomolecules in human samples indicated recoveries in the range of 98.8%−102.88% with the highest relative standard deviation being 3.49%, offering great accuracy and precision. These results are the highest reported sensitivity for these analytes using an immunoassay method. Our PT-μTAD strategy is therefore a promising approach for detecting biomolecules in resource-limited point-of-care settings.

Gold Nanomaterial-Based Microfluidic Paper Analytical Device for Simultaneous Quantification of Gram-Negative Bacteria and Nitrite Ions in Water Samples

“…AuNPs were synthesized according to our previous procedure with slight modifications . Briefly, 50.0 mL of a HAuCl 4 solution at 40.0 mmol/L was heated for 30 min while stirring.…”

“…AuNPs were synthesized according to our previous procedure with slight modifications. 21 Briefly, 50.0 mL of a HAuCl 4 solution at 40.0 mmol/L was heated for 30 min while stirring. Subsequently, 2.0 mL of 2.0% (w/v) sodium citrate was introduced immediately into the solution while heating and stirring.…”

“…Gold nanoparticles (AuNPs) have recently gained significant attention in colorimetric analysis due to their size and shape-dependent optical properties based on surface plasmon resonance (SPR). , Functionalization of AuNPs enables their customization for specific applications, including selective detection and signal amplification . The use of AuNPs in colorimetric analysis demonstrates great promise for the development of sensitive and selective analytical platforms .…”

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer

“…† Furthermore, our developed dPADs offer a highly practical approach to monitoring compared to previous methods, as indicated in Table 1. 6,7,10,11,[35][36][37][48][49][50][51][52][53][54][55] Though some of these prior methods employ techniques such as resonance Raman, immunosensing, and photothermal detection that can exhibit greater sensitivity than our method, it is important to note that they still need expensive instrumentation and rely on expensive antibodies for biorecognition. On the other hand, our dPADs present an instrument-free analytical sensor for timely monitoring of associated cytokine levels for clinical POC testing.…”

Simple distance-based thread analytical device integrated with ion imprinted polymer for Zn2+ quantification in human urine samples

“…† The outermost layer of natural cotton fibers is typically covered in wax. [57][58][59] Most of the wax is composed of long fatty acid chains, which renders cotton fibers hydrophobic and diminishes the material's capacity to wick liquid. To remove the wax and enhance the hydrophilic property of the thread, we treated the thread with Na 2 CO 3 solution, resulting in a higher amount of the hydroxyl (-OH) groups on the surface of the thread.…”