Synthesis and charactrization of MXene-based materials for biosensing applications

Abstract

MXenes are a new member of the two-dimensional (2D) material family that have piqued the interest of many researchers in recent years. Niobium carbide (Nb2CTx), one of the MXenes compositions, has excellent metal conductivity, large surface area and tunable bandgap, which makes it appealing for a variety of applications. However, the use of a very toxic fluoride-containing etchant and a rather long etching time in the traditional synthesis process has severely limited future research of MXene, particularly its biological use. Considering that rapid aluminum clearance of E-etching strategy, excellent chemical stability, and biocompatibility of the obtained E-etching MXene, a fluoride-free Nb2CTx/acetylcholinesterase (AChE)-based biosensor was constructed, realizing the sensitive and selective detection of phosmet with the limit of detection down to 0.046 ng mL−1. The proposed Nb2CTx-enzyme based biosensor outperforms the counterpart manufactured from hydrofluoric acid-etching Nb2CTx, showing that fluoride-free MXene can improve enzyme activity and electron transfer in the biosensor. Due to the linear output, great repeatability, low cost, and sample operation process, this fluoride-free Nb2CTx/AChE electrochemical biosensor has the great potential in pesticide detection with ultrahigh sensitivity and selectivity. Furthermore, as a robust and biocompatible nanoplatform, the electrochemical biosensor based on the fluorine-free Nb2CTx/enzyme will be expanded to the application of viral screening, with the goal of realizing affordable, fast, and point-of-care detection. We are currently experiencing the COVID-19 outbreak, a global public health crisis that has claimed the lives of millions. Large-scale population screening is an effective way of limiting viral transmission that has the potential to dramatically reduce disease burden and deaths. However, the conventional RT-PCR method for viral detection necessitates specialized equipment, well-trained personnel, and lengthy waiting periods. Because of the strong fluorescence quenching ability of E-etching Nb2CTx and the lack of autofluorescence background of Ln3+-based nanoprobes, we built a UCNPs/Nb2CTx integrated biosensor for multiplexed viral oligo detection. The proposed technique, which is based on the weakening of the luminescence resonance energy transfer (LRET) interaction between UCNP and Nb2CTx MXene, seeks to provide a simple method for luminescence readout for the detection of viral oligonucleotides. Longer Förster distance with the addition of viral oligonucleotides resulted in a rise in UCL intensities, which was used to evaluate virus quantity. The sensor realizes multiplexed detection of target gene of SARS-CoV-2 (ORF1ab, E, N gene) in less than 10 min of incubation time, with a limit detection of 59 pM for ORF1ab and 476 pM for N gene. We strongly believe that this simple and sensitive biosensor might be utilized for real-time sample analysis in the future. Although 2D materials based biosensing systems for DNA detection have been extensively investigated due to their many interesting electrical, optical, mechanical, and catalytic properties. Since the negatively charged surface of these materials, the ease of probe modification and DNA adsorption are still challenging for designing a 2D nanobiosensors. Herein we developed a novel one-step strategy for fast packaging single strand DNA on MXene in 5 min via introducing of noble metal ion as a bridge , facilitating to construct a stable biosensing system for detecting DNA or other analytes. In addition, considering the mild reducibility, flatness, flexible surface chemistry and large surface area of MXene, as well as selective affinity of the DNA to the specific facets in the noble metal crystals, the anisotropic morphology of noble metal nanostructure on MXene in a sequence-dependent manner can be achieved. The morphology transformation of anisotropic noble metal nanoparticles (ANPs), may have a response to the plasmonic signal, endowing this nanoplatform with the potential for molecular biosensing. Furthermore, coupling such ANPs on the MXene surface has been proved to be enhanced functionalities. Our work makes the fabrication of ANPs-MXene heterostructure or 2D MXene-based DNA biosensor easier, stimulating further explorations of physical, chemical, and biological applications.