A Study on Application of Multiplexed Diagnostic Sensors using Paper-Based Biosensing Platforms

Abstract

Performance, user convenience, and affordability of diagnosis platforms, including those used for cancer, have been studied. Owing to the development of bioreceptors and transducers, it is no longer necessary to choose only one of them for miniaturization and equipment performance. Platforms that are small enough and perform better are emerging. There have also been several attempts to achieve higher sensitivity and shorter assay time than conventional equipment. Multiplexing diagnosis has become a hot topic in the clinical field with the discovery of various biomarkers for diseases—with the correlations between their onsets and progressions now revealed. Besides achieving greater diagnostic accuracy, new criteria can be created when multiple biomarkers are measured and analyzed at once. Considering user convenience and cost, the paper-based sensor is a good alternative to lab-centered diagnostic devices. It is a platform replacing the presence of a target analyte by the signal of a bioreceptor and a transducer, as it passes with capillary flow through a porous matrix. Structurally, there are lateral and vertical flows separately. Selecting a platform appropriate to the situation can create suitable results for clinical settings. In addition, it is even possible to derive results effortlessly, because paper sensors have an effective range of choices for fabrication and immobilization. In these studies, we developed a multichannel paper-sensor that can be used in areas requiring multiple diagnoses. We checked whether it worked in the actual diagnosis area. For tetrahydrocannabinol (THC) diagnosis, which requires quick results while satisfying the standard sensitivity, a radial-flow assay was developed by modifying the vertical-flow assay, which can measure 0.1 ng/mL THC in saliva within 3 min (Chapter 2). A test for prostate cancer-specific antigen (PSA) is always performed first in the diagnosis of prostate cancer (PCa). However, owing to the characteristics of biogenesis, PSA is generated not only in PCa but also in prostatitis or benign prostatic hyperplasia. Therefore, the PSA test was not highly accurate. Additional tests caused patient discomfort and increased medical costs. To solve this problem and increase the diagnostic accuracy to 98% (Chapter 3), a dual-channel LFA sensor was developed. It helped measure PSA and sialyated PSA (added with sialic acid) simultaneously. Finally, to detect ovarian cancer at an early stage through multiple diagnoses, patient-derived exosomes were analyzed using a trident LFA sensor (Chapter 4). Until now, structural multi-diagnosis has been possible, but a non-specific signal is generated when bioreceptors are as diverse as the number of targets used. It deteriorates sensor performance owing to cross-activity between the bioreceptors (detection antibodies). This is an inevitable problem when moving from single diagnosis to multiple diagnosis, and this problem is structurally difficult to solve. However, it can be solved by using exosomes. As they are heterogeneous nano-sized particles with several biomarkers present on the surface, multiple diagnoses are possible using only one type of detection-antibody. Using this principle, ovarian cancer was diagnosed, and the expression levels of biomarkers between cancer cell lines were also distinguished.