Yue Zheng,Xiaoyu Wang,Shengquan He,Zehua Gao,Ya Di,Kunling Lu,Kun Li,Jidong Wang
A electrochemical biosensing strategy was developed for green and ultrasensitive detection of tumor cells by combining aptamer-DNA concatamer-CdTe quantum dots (QDs) signal amplification probe with mercury-free anodic stripping voltammetry (ASV). First, aptamer-DNA concatamer- CdTe QDs probes were designed by DNA hybridization and covalent assembling, which contained specific recognition of aptamer and signal amplification incorporating the DNA concatamer with QDs. Meanwhile, the capture electrode, glassy carbon electrode (GCE)/Graphene oxide (GO)/Polyaniline (PANI) / Glutaraldehyde (GA) / concanavalin A (Con A) was fabricated by a layer-by-layer assembling technique. K562 cells , as model cancer cells were detected to demonstrate the feasibility of this sensing strategy. Then, novel composite, graphene (GR)- Poly diallyldimethylammonium chloride (PDDA)/ L -Cysteine (L- Cys), was explored in ASV which replaced mercury electrodes using for determination of tumor cells. The proposed electrochemical biosensor showed high sensitivity with the detection limit of 60 cells mL −1 . More importantly, this novel design of signal amplification probes and the exploration of new composites in mercury-free ASV analysis would provide a promising method for ultrasensitive biosensor preparation and green electrochemical detection of tumor cells.
A sensitive electrochemical biosensor was designed for determination of aflatoxin B1 (AFB1) using a copper-based metal-organic framework (Cu-MOF), which has strong electrochemical activity and exonuclease III (Exo III)-assisted recycling for dual signal amplification. Hairpin DNA (S1) was immobilized on the electrode. The AFB1 was recognized by aptamer DNA (S2) and complementary DNA (S3) was released. The S3 hybridized with the hairpin S1 to form the Exo III hydrolyzed double-stranded DNA, leaving a partial sequence of hairpin DNA (S1′) on the electrode and releasing S3 for the next cycle of the opening and digestion of hairpin S1. The amplified S1′ then was able to combine with more signal probes. Cu-MOF bond gold nanoparticles (AuNPs) by -NH2 were immobilized to capture DNA (S4) to obtain Cu-MOF/AuNPs/S4. This signal probe Cu-MOF/AuNPs/S4 was able to hybridize with the electrode and generate an amplified electrochemical signal. Under the optimized conditions, this electrochemical biosensor for AFB1 exhibited a low detection limit of 6.7 × 10−7 ng/mL at a signal-to-noise equal to 3 and a wide linear range from 10−6 to 1 ng/mL. The biosensor was also used to analyze AFB1-spiked beer sample with recovery values between 96% and 103%. This method has the potential to become a valuable technology for detecting various toxins by the selection of the appropriate aptamer DNA.
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