An Electrochemical Ti3C2Tx Aptasensor for Sensitive and Label-Free Detection of Marine Biological Toxins

Abstract

Saxitoxin (STX) belongs to the family of marine biological toxins, which are major contaminants in seafood. The reference methods for STX detection are mouse bioassay and chromatographic analysis, which are time-consuming, high costs, and requirement of sophisticated operation. Therefore, the development of alternative methods for STX analysis is urgent. Electrochemical analysis is a fast, low-cost, and sensitive method for biomolecules analysis. Thus, in this study, an electrolyte-insulator-semiconductor (EIS) sensor based on aptamer-modified two-dimensional layered Ti3C2Tx nanosheets was developed for STX detection. The high surface area and rich functional groups of MXene benefited the modification of aptamer, which had specific interactions with STX. Capacitance-voltage (C-V) and constant-capacitance (ConCap) measurement results indicated that the aptasensor was able to detect STX with high sensitivity and good specificity. The detection range was 1.0 nM to 200 nM and detection limit was as low as 0.03 nM. Moreover, the aptasensor was found to have a good selectivity and two-week stability. The mussel tissue extraction test suggested the potential application of this biosensor in detecting STX in real samples. This method provides a convenient approach for low-cost, rapid, and label-free detection of marine biological toxins.

A Novel SELEX Based on Immobilizing Libraries Enables Screening of Saxitoxin Aptamers for BLI Aptasensor Applications

“…The ELISA detection [ 6 ] method is cumbersome (>1 h) and prone to cross-reaction. Although some methods have lower detection limits, such as Electrochemical Ti3C2Tx [ 53 ]: 0.03 nM (0.01ng/mL), Colorimetric aptasensor [ 54 , 55 ]: 42.46–142.3 pM (0.01–0.04 ng/mL), Fluorescence assay [ 34 ]: 0.39 ng/mL, Electrochemical aptasensor [ 28 , 56 ]: 0.11–0.28 ng/mL, SE aptasensor [ 31 ]: 0.11 ng/mL, the detection limit of the sensor (0.5 ng/mL) obtained from this work is significantly lower than the maximum permitted limit of STX (3 ng/mL, toxicity equivalents) in drinking water, which was standardized by Australia, Brazil, and New Zealand [ 29 , 53 ]. Furthermore, compared with the other detection methods, this aptasensor has unique merits.…”

Rapid Advances of Versatile MXenes for Electrochemical Enzyme‐Based Biosensors, Immunosensors, and Nucleic Acid‐Based Biosensors

“…3.30 fg mL À 1 0.01 to 1.00 pg mL À 1 HT/H2/dep Au/Ru@MXene/Nafion/GCE Mucin 1 26.9 ag mL À 1 100 ag mL À 1 to 10 ng mL À 1 [36] Model DNA À AgNCs/target DNA/MCH/HP DNAs, swing arm-blocker/ Au@Ti 3 C 2 @PEIÀ Ru(dcbpy) 3 2 + /Nafion/GCE SARS-CoV-2 RdRp gene 0.21 fM 1 fM to 100 pM [37] GCE/Au-g-C 3 N 4 /TDNAs/MCH/SARS CoV-2 RdRp/PEIÀ Ru@Ti 3 C 2 @AuNPsÀ S7 SARS-CoV-2 RdRp gene 7.8 aM 10 aM to 10 pM [38] Ru(dcbpy) 3 2 + /AuNPs@Ti 3 C 2 /GCE Siglec-5 20.22 fM 20 fM to 100 pM [39] dsDNA/CCB/MNP/aptamer/Ti 3 C 2 T x /ZIF-8/GCE HIV-1 protein 0.3 fM 1 fM to 1 nM [40] Electrolyte insulator-semiconductor (EIS) sensor Saxitoxin 0.03 nM 1.0 nM to 200 nM [41] T4 RNA ATP/GN/MoS 2 @Ti 3 C 2 T x MXene/SPEC Thyroxine 0.39 pg mL À 1 7.8 × 10 À 1 to 7.8 × 10 À 6 pg mL À 1 linearly related to the concentration of the target. The enzymebased biosensor is not affected by color, turbidity or particle size and still possesses unique advantages such as high specificity and high sensitivity.…”

“…Wang et al [40] explored the ECL aptasensor of Ti 3 C 2 /ZIF-8 by combining Ti 3 C 2 with ZIF-8, in which the aptamer could effectively recognize HIV-1 protein. Ullah et al [41] proposed Ti 3 C 2 -aptamer for aptasensor analysis of saxitoxin based on the conformational changes that occurred when aptamer contacted the target, and an electrolyte-insulator-semiconductor sandwich structure as a transducer of the aptasensor.…”

A simple electrochemical aptasensor for saxitoxin detection

“…26 Over time, this led to the emergence of diverse aptamer-based detection methods for STX. [27][28][29] For example, Hou et al designed an electrochemical aptasensor modied with the STX aptamer and multiwalled carbon nanotubes/self-assembled monolayer (MWCNTs/SAM), in which methylene blue (MB) served as indicator for STX detection, providing the detection limit of 0.38 nM and good selectivity. 27 Ullah et al developed an aptasensor using aptamer-modied MXene for STX detection, whose efficiency was assessed via capacitance-voltage and constant-capacitance measurements.…”

“… 27 Ullah et al developed an aptasensor using aptamer-modified MXene for STX detection, whose efficiency was assessed via capacitance–voltage and constant-capacitance measurements. 29 The detection range of the aptasensor was 1.0–200 nM and the detection limit was 0.03 nM. Park et al 30 fabricated an electrochemical biosensor using round-type micro-gap electrodes as working electrode, and the sensitivity for STX detection was improved by introducing the porous platinum nanoparticle (pPtNP) that enhanced the electrochemical sensitivity.…”