Emerging Trends and Recent Progress of MXene as a Promising 2D Material for Point of Care (POC) Diagnostics

Recent advances using MXenes in biomedical applications

An MXene is a novel two-dimensional transition metal carbide or nitride, with a typical formula of Mn+1XnTx (M = transition metals, X = carbon or nitrogen, and T = functional groups). MXenes have found wide application in biomedicine and biosensing, owing to their high biocompatibility, abundant reactive surface groups, good conductivity, and photothermal properties. Applications include photo- and electrochemical sensors, energy storage, and electronics. This review will highlight recent applications of MXene and MXene-derived materials in drug delivery, tissue engineering, antimicrobial activity, and biosensors (optical and electrochemical). We further elaborate on recent developments in utilizing MXenes for photothermal cancer therapy, and we explore multimodal treatments, including the integration of chemotherapeutic agents or magnetic nanoparticles for enhanced therapeutic efficacy. The high surface area and reactivity of MXenes provide an interface to respond to the changes in the environment, allowing MXene-based drug carriers to respond to changes in pH, reactive oxygen species (ROS), and electrical signals for controlled release applications. Furthermore, the conductivity of MXene enables it to provide electrical stimulation for cultured cells and endows it with photocatalytic capabilities that can be used in antibiotic applications. Wearable and in situ sensors incorporating MXenes are also included. Major challenges and future development directions of MXenes in biomedical applications are also discussed. The remarkable properties of MXenes will undoubtedly lead to their increasing use in the applications discussed here, as well as many others.

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.

Two-dimensional layered MoSe2/graphene oxide (GO) nanohybrid coupled with the specific immune-recognition element for rapid detection of endosulfan

Endosulfan (En) is an organochlorine biocide (OCB), that ends up in the environment due to the enzymatic and microsomal activity even though it is not accumulated in living tissue. Endosulfan acts as an organic micro-pollutant which disrupts land as well as aquatic ecosystem. In the present study, we chemically modified endosulfan and conjugated it with a carrier protein to produce an immune response. The generated antibodies were tested for specificity against En, and characterized before further use. Transition Metal Chalcogenides (TMC) showed excellent optoelectrical potential due to its direct bandgap and distinct physical as well as chemical characteristics. Herein, we synthesized a novel nanohybrid using MoSe2 in combination with graphene oxide (GO) and characterized thoroughly. This was similar to graphene-based metal chalcogenides which were further used in this study to fabricate biosensor for the sensitive detection of En. The in-house developed antibodies (En-Ab) were coupled with the nanohybrid to make MoSe2/GO/En-Ab electrode. Fabricated electrode was tested for electrochemical parameters using differential pulse voltammetry (DPV). Working efficiency of the fabricated electrode i.e., limit of detection (LOD), was found to be 7.45 ppt. In conclusion, we hypothesized that the synthesized TMC nanohybrids could be employed for biosensing of endosulfan, and can likely be developed to test field samples.