A Label-Free Aptamer-Based Fluorescent Assay for Cadmium Detection

Abstract

Selective detection of ultratrace amounts of cadmium (Cd 2+ ) is extremely important for food safety and environmental monitoring because of its toxicity and widespread use. In this work, we developed a facile, rapid, sensitive, and highly selective method for the detection of Cd 2+ based on a label-free aptasensor using an unmodified double-stranded deoxyribonucleic acid-specific dye (PicoGreen). The linear range was 0.10-100 µg/mL, and the detection limit (0.038 ng/mL) was lower than the guideline from the World Health Organization for Cd 2+ in drinking water (3 ng/mL). The sensor exhibited excellent selectivity towards Cd 2+ ions. We tested the aptasensor in application to a series of real water samples spiked with different concentrations of Cd 2+ . Compared with atomic absorption spectrometry, the results showed good tolerance to the matrix effect. The developed approach shows great potential for on-site and high-throughput analysis in routine monitoring.

DNA–RNA complementation on silicon wafer for thyroid cancer determination

“…These interactions include protein-protein, protein-antibody, protein-aptamer, DNA-DNA, DNA-RNA, probe-receptor, probe-glycan, and probe-lipid. With these wide range options, panels of biosensors were generated [11,[36][37][38][39]. However, the preferences fall with the affinity between the desired target molecule/biomarker of interest against the probe, which can capture the targeted molecule.…”

Bio-Recognition in Spectroscopy-Based Biosensors for *Heavy Metals-Water and Waterborne Contamination Analysis

“…A label-free aptasensor approach for Cd (II) detection was independently exploited by Y. Luan et al [72] and B. Zhou et al [73], combining an aptamer with unmodified dsDNA-specific dye. Based on the principle that hybridization of two aptamers boosts the fluorescence engendered during the reaction, B. Zhou et al showed that, in the absence of Cd 2+ , SYBR green-I binds to the small groove of dsDNA (aptamer-complementary strand) establishing the dsDNA–dye complex and generating high fluorescence signal.…”

“…After the introduction of complementary strands and Pico Green dye (PG), a hybrid with the residual free aptamers that did not bind with Cd 2+ is formed. This results in a higher PL signal (Figure 4e), allowing a higher sensitivity (LOD of 0.038 ng/mL) [72].…”

“…( e ) Random coil structure to aptamer–Cd 2+ complex. After the addition of complementary strands and PG, the residual free aptamer that did not bind with Cd 2+ forms a hybrid with complementary strands and PG dye which results in a big fluorescent enhancement [72]. ( f ) Pb 2+ -induced hydrolytic cleavage signal-off.…”

Label-Free and Sensitive Determination of Cadmium Ions Using a Ti-Modified Co3O4-Based Electrochemical Aptasensor

“…Currently, two different aptamers of Cd 2+ have been respectively selected by two independent groups [26,27]. Then, colorimetric [28] and fluorescent methods [26,29] were exploited to determine Cd 2+ . As for electrochemical methods, they are sensitive, and some portable devices are already commercial and available, including pocketSTAT2 (Ivium Technologies, Netherlands), PalmSens4 (Palmsens, Netherlands), μStat-i 400 (Metrohm, Switzerland) and CHI1200C (CH Instruments, China).…”