Sudarsan Sujesh, Shetty Prashil, Chinnappan Raja, Mani Naresh Kumar
Microfluidics, Sensors and Diagnostics (μSenD) Laboratory, Centre for Microfluidics, Biomarkers, Photoceutics and Sensors (μBioPS), Department of Biotechnology, Manipal Institute of Technology, Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India.
College of Medicine, Alfaisal University, 11533, Riyadh, Saudi Arabia.
Anal Bioanal Chem. 2023 Nov;415(26):6449-6460. doi: 10.1007/s00216-023-04921-2. Epub 2023 Sep 4.
This study investigated the colorimetric response of standard glucose, serum glucose, and nucleic acid assays on various paper surfaces with different wettability, including hydrophilic, hydrophobic, and nearly superhydrophobic surfaces. Water contact angles (WCA) formed by water droplets on each surface were measured using ImageJ software. The hydrophilic surface showed no contact angle, while the hydrophobic and nearly superhydrophobic surfaces exhibited contact angles of 115.667° and 133.933°, respectively. The colorimetric sensitivity of the standard glucose assay was analyzed on these surfaces, revealing enhanced sensitivity on the nearly superhydrophobic surface due to the high molecular crowding effect owing to its non-wetting behavior and eventually confined reaction product at the sample loading zone. The hydrophobic nature of the surface restricts the spreading and diffusion of the reaction product, leading to a controlled and localized concentration of the assay product leading to moderate colorimetric intensity. On the other hand, the hydrophilic surface showed the least enhancement in colorimetric sensitivity; this is attributed to the high wettability of the hydrophilic surface causing the reaction product to spread extensively, resulting in a larger area of dispersion and consequently a lower colorimetric intensity. The measured limit of detection (LOD) for nucleic acid on nearly superhydrophobic surfaces was found to be 16.15 ng/µL, which was almost four-fold lower than on hydrophilic surfaces (60.08 ng/µL). Additionally, the LODs of standard glucose and clinical serum samples were two-fold lower on nearly superhydrophobic surfaces compared to hydrophilic surfaces. Our findings clearly highlight the promising potential of utilizing superhydrophobic surfaces to significantly enhance colorimetric sensitivity in paper-based diagnostic applications. This innovative approach holds promise for advancing point-of-care diagnostics and improving disease detection in resource-limited settings.
本研究调查了标准葡萄糖、血清葡萄糖和核酸检测在具有不同润湿性的各种纸张表面（包括亲水性、疏水性和近超疏水性表面）上的比色响应。使用ImageJ软件测量水滴在每个表面上形成的水接触角（WCA）。亲水性表面没有接触角，而疏水性和近超疏水性表面的接触角分别为115.667°和133.933°。在这些表面上分析了标准葡萄糖检测的比色灵敏度，结果表明，由于近超疏水性表面的非润湿行为导致高分子拥挤效应，并最终将反应产物限制在样品加载区，因此其比色灵敏度有所提高。表面的疏水性限制了反应产物的扩散，导致检测产物的浓度得到控制和局部化，从而产生适度的比色强度。另一方面，亲水性表面的比色灵敏度增强最少；这归因于亲水性表面的高润湿性导致反应产物广泛扩散，从而导致更大的分散面积，进而导致比色强度较低。发现在近超疏水性表面上核酸的测量检测限（LOD）为16.15 ng/µL，几乎比亲水性表面（60.08 ng/µL）低四倍。此外，与亲水性表面相比，近超疏水性表面上标准葡萄糖和临床血清样品的LOD低两倍。我们的研究结果清楚地突出了利用超疏水表面在基于纸张的诊断应用中显著提高比色灵敏度的潜在前景。这种创新方法有望推动即时诊断，并改善资源有限环境中的疾病检测。
