A Colorimetric Biosensing Platform with Aptamers, Rolling Circle Amplification and Urease‐Mediated Litmus Test

Abstract

Here we report on an ultra‐sensitive colorimetric sensing platform that takes advantage of both the strong amplification power of rolling circle amplification (RCA) and the high efficiency of a simple urease‐mediated litmus test. The presence of a target triggers the RCA reaction, and urease‐labelled DNA can hybridize to the biotinylated RCA products and be immobilized onto streptavidin‐coated magnetic beads. The urease‐laden beads are then used to hydrolyze urea, leading to an increase in pH that can be detected by a simple litmus test. We show this sensing platform can be easily integrated with aptamers for sensing diverse targets via the detection of human thrombin and platelet‐derived growth factor (PDGF) utilizing structure‐switching aptamers as well as SARS‐CoV‐2 in human saliva using a spike‐binding trimeric DNA aptamer. Furthermore, we demonstrate that this colorimetric sensing platform can be integrated into a simple paper‐based device for sensing applications.

Aptamers and Nanobodies as New Bioprobes for SARS-CoV-2 Diagnostic and Therapeutic System Applications

“…Regarding the colorimetric assay, it is worth noting that it is the simplest, most basic, highly visible, and relatively inexpensive method available for detection [ 79 , 83 , 88 , 115 , 116 ]. A representative example is the enzyme-linked aptamer-based sandwich assay (ELASA), which utilizes aptamers instead of Abs in an enzyme-linked immunosorbent assay (ELISA).…”

“…[ 83 ]. The strategy of rolling circle amplification (RCA)-urease based biosensing has also been reported for the detection of SARS-CoV-2 [ 88 ]. This sensor exploits the yellow-to-pink transition of phenol due to urease activity enhanced by RCA, achieving an LOD of 3.2 × 10 3 copies/mL for pseudovirus.…”

Artificial Intelligence in Point-of-Care Biosensing: Challenges and Opportunities

“…Transduction is key to biosensing systems as it provides a means to convert molecular interactions into signals that are more easily processed and analyzed. The most common transduction methods include electrochemical [ 11 , 13 ], electronic [ 27 ], colorimetric [ 28 , 29 ], optical [ 30 ], acoustic [ 31 ], thermal [ 32 ], and piezoelectric [ 33 ] methods.…”