Ratiometric antifouling electrochemical biosensors based on designed Y-shaped peptide and MXene loaded with Au@ZIF-67 and methylene blue.

Based on the designed inverted Y-shaped peptide and MXene nanocomposite (MXene-Au@ZIF-67), a ratiometric anti-pollution electrochemical biosensor was designed and applied to the detection of biomarkers in serum. Au@ZIF-67 inserted into the interior of MXene can not only prevent the accumulation of MXene but also provide a large amounts of binding sites for capturing biomolecules. A designed multifunctional Y-shaped peptide containing anchoring, antifouling, and recognition sequences was anchored onto MXene-Au@ZIF-67 through Au-S bonds. Electrochemical signal molecules, ferrocenecarboxylic acid (Fc) and methylene blue (MB), were modified to another end of multifunctional peptide and interior of MXene-Au@ZIF-67, respectively, to produce a ratiometric electrochemical signal. We selected prostate specific antigen (PSA) as the model compound. PSA specifically recognizes and cleaves the recognition segment in the Y-shaped peptide, and the signal of Fc is reduced, while the signal of MB remains unchanged. The ratiometric strategy endows the present biosensor high accuracy and sensitivity with a detection limit of 0.85 pg/mL. In addition, the sensing surface has good antifouling ability due to the antifouling sequence of the two branching parts of the Y-shaped peptide. More importantly, by replacing the recognition segment of peptides also other targets are accessible, indicating the potential application of the universal detection strategy to the detection of various biomarkers in clinical diagnosis.

Low fouling electrochemical biosensors based on designed Y-shaped peptides with antifouling and recognizing branches for the detection of IgG in human serum.

The nonspecific adsorption and accumulation of biomolecules on electrode interfaces remains a challenge for sensitive and accurate detection of disease markers in complex biological media, and it is highly desired to develop antifouling biosensors capable of assaying targets in complicated real liquids. Herein, an efficient and simple antifouling biosensor was constructed based on a self-designed Y-shaped peptide. The Y-shaped peptide was designed with two branches: one branch with the peptide sequence of EKEKEKE for antifouling, and the other branch with the peptide sequence of HWRGWVA for recognizing of human IgG. Under optimized experimental conditions, electrodes modified with Y-shaped peptides exhibited excellent antifouling and electrochemical sensing performances. The developed biosensor was able to effectively resist biofouling in various protein solutions and even serum samples, and the linear range of the biosensor for human IgG detection was from 100 pg mL-1 to 10 µg mL-1, with a relatively low limit of detection of 32 pg mL-1 (S/N = 3). The antifouling biosensor possesses the capability of assaying human IgG in real serum samples, and this strategy of developing low fouling biosensors based on Y-shaped peptides can be readily expanded to the construction of other biosensing systems for different targets.