Improving the sensitivity of cellulose fiber-based lateral flow assay by incorporating barriers into nitrocellulose membrane

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University of New Brunswick


‘Test, test, test’ is the key to curb the spreading of infectious diseases, especially for COVID-19. Rapid testing devices with cellulose membrane-based lateral flow assay (LFA) could play a significant role due to the immense advantageous features. The World Health Organization (WHO) defined that diagnostic as ASSURED: affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverable to end-users; and they are getting much attraction in point-of-care (POC) centers. Compared to the time consuming, expensive lab-based testing, it still lags behind due to its lower sensitivity. Herein, to increase the LFA sensitivity, we designed and developed three low-cost, facile methods to modify cellulose membrane of LFA: 1) introduction of a compressed double barriers concept; 2) incorporation of two-sugar barriers; 3) integration of a water-dissolvable PVA dam. For the first and second approaches, one barrier was placed between the conjugate pad and test line, and the other barrier between the test and control lines, lead to delay the sample flow, thus, improving its sensitivity. ORF1ab nucleic acid of COVID-19 was used as the model target to demonstrate the concept. In the first method, no additional chemicals/materials are added. The sensitivity was enhanced by 4-fold for the compressed double barriers modified LFA, and 5-fold for the two-sugar barrier methods, respectively. For the third approach, two modifications were implemented: (1) using cellulose fibers, rather than glass fibers, for a sample pad, and (2) incorporating a one-step simple PVA dam between the conjugate pad and test line; both delayed the sample flow, then gradual increased, and controlled the flow rate distribution across the thickness of the NC membrane. Combinedly, a 20-times increase in the sensitivity was achieved in the modified LFA device. These low-cost, easy-to-fabricate, environment friendly and easy-to-integrate LFA sensitivity enhancement methods may have potential applications in other cellulose paper-based platforms including point-of-care (POC), Do-It-Yourself (DIY)-based microfluidics paper-based analytical devices to control and prevent infectious diseases including COVID-19, food safety, and environment monitoring.