A lateral flow aptasensor for detection of cadmium

Abstract

An aptamer-based lateral flow assay (ALFA) was developed for the rapid detection of cadmium (Cd2+). This sensor integrates a fast, easy-to-use lateral flow assay and a specific aptamer probe for Cd2+ detection. The operation of the ALFA strip begins by mixing a cadmium-specific aptamer probe (apCd) with the sample. A gold nanoparticle labeled with an aptamer probe (apAuNPs), containing two specific regions—(i) complementary region designed to hybridize with the test line and (ii) a poly-thymine region designed to hybridize with poly-adenine the control line—is then added to the solution. This mixed solution is applied onto an ALFA strip immobilized with specific test and control lines. In the absence of Cd2+, the structure of the apCd probe remains available, allowing it to hybridize with the apAuNPs probe. The duplex structure between apCd and apAuNPs probe cannot bind with the aptamer probe on the test line, resulting in no colored band on the test line, which is interpreted as “negative”. In the presence of Cd2+, the apCd probe bind specifically to Cd2+, making the apCd probe unavailable for hybridization, thus leaving apAuNPs probe free to hybridize with the test line. This results in visible colored band, interpreted as “positive”. Under optimal conditions, the ALFA effectively identified the presence of Cd2+ within a detection range of 1–5000 ppb, with a detection limit of 0.02 ppb. Moreover, the device demonstrated non-interference with common metals (Zn2+, Fe3+, Cu2+, Co2+, Bi3+, Ag+, Pb2+, and As3+). The ALFA strip was successfully applied to detect Cd2+ in drinking water, tap water, and river water samples, showing acceptable % recovery of 96.15% for drinking water, 91.87% for tap water, and 91.37% for river water. These results were in good agreement with those obtained from standard methods (Inductively coupled plasma atomic emission spectroscopy: ICP-AES). Therefore, the proposed device is an easy-to-use, rapid, and portable tool for screening Cd2+ in water from various sources.