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MOF/COF-based hybrids show the properties of precisely tunable compositions and structures, and provide a broad range of potential applications in gas sorption and separation, catalysis, energy transfer, biomedicine, etc.

A novel label-free surface plasmon resonance (SPR) aptasensor has been constructed for the detection of N-gene of SARS-CoV-2 by using thiol-modified niobium carbide MXene quantum dots (Nb 2 C-SH QDs) as the bioplatform for anchoring N-genetargeted aptamer. In the presence of SARS-CoV-2 N-gene, the immobilized aptamer strands changed their conformation to specifically bind with N-gene. It thus increased the contact area or enlarged the distance between aptamer and the SPR chip, resulting in a change of the SPR signal irradiated by the laser (He-Ne) with the wavelength (λ) of 633 nm. Nb 2 C QDs were derived from Nb 2 C MXene nanosheets via a solvothermal method, followed by functionalization with octadecanethiol through a self-assembling method. Subsequently, the gold chip for SPR measurements was modified with Nb 2 C-SH QDs via covalent binding of the Au-S bond also by self-assembling interaction. Nb 2 C-SH QDs not only resulted in high bioaffinity toward aptamer but also enhanced the SPR response. Thus, the Nb 2 C-SH QD-based SPR aptasensor had low limit of detection (LOD) of 4.9 pg mL −1 toward N-gene within the concentration range 0.05 to 100 ng mL −1 . The sensor also showed excellent selectivity in the presence of various respiratory viruses and proteins in human serum and high stability. Moreover, the Nb 2 C-SH QD-based SPR aptasensor displayed a vast practical application for the qualitative analysis of N-gene from different samples, including seawater, seafood, and human serum. Thus, this work can provide a deep insight into the construction of the aptasensor for detecting SARS-CoV-2 in complex environments.

Tunable electrochemical biosensors based on analogous Zr-MOFs were developed for protein detection, the performances of which rely on the pore sizes and surroundings of the MOFs that show diverse binding behaviors to aptamers and then the targeted proteins. The optimized Zr-MOF-based sensor has high selectivity to lysozyme in a wide concentration range and a low detection limit of 3.6 pg mL, with good repeatability, stability, and applicability in real samples. This work will establish a new platform for biosensing and extend the application scope of MOF materials.