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Enzyme-mediator bioconjugation is emerging as a building block for designing electrode platforms for the construction of biosensors and biofuel cells. Here, we report a one-pot bioconjugation technique for flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) and thionine (TH) using a series of cross-linkers, including epoxy, N-hydroxysuccinimide (NHS), and aldehydes. In this technique, FAD-GDH and thionine are conjugated through an amine cross-linking reaction to generate a redox network, which has been successfully employed for the oxidation of glucose. The bioconjugation chemistry of cross-linkers with the amino groups on FAD-GDH and thionine plays a vital role in generating distinct network structures. The epoxy-type cross-linker reacts with the primary and secondary amines of thionine at room temperature, thereby producing an FAD-GDH-TH-FAD-GDH hyperbranched bioconjugate network, the aldehyde undergoes a rapid cross-linking reaction to produce a network of FAD-GDH-FAD-GDH, while the NHS-based cross-linker can react with the primary amines of both FAD-GDH and thionine, forming an FAD-GDH-cross-linker-TH polymeric network. This reaction has the potential to enable the conjugation of a redox mediator with a FAD-GDH network, which is particularly essential when designing an enzyme electrode platform. The data demonstrated that the polymeric cross-linked network based on the NHS cross-linker exhibited a considerable increase in electron transport while producing a catalytic current of 830 μA cm–2. The cross-linker spacer arm length also affects the overall electrochemical function of the network and its performance; an adequate spacer length containing a cross-linker is required, resulting in a faster electron transfer. Finally, a leaching test confirmed that the stability of the enzyme electrode was improved when the electrode was tested using the redox probe. This study elucidates the relationship between cross-linking chemistry and redox network structure and enhances the high performance of enzyme electrode platforms for the oxidation of glucose.

•Recent progress of enzyme immobilized in metal organic frameworks (MOFs) in biosensing applications are summarized.•Comprehensive classification of enzyme-MOF composite synthesis through post synthesis and direct mixing method.•Advancements in MOF with redox active metal or redox active ligand provide enzyme mimicking activity.•Comparative studies of MOF with COF have drawn interest owing to their potential for use in electrochemical biosensing applications.

The recent trend on metal organic framework (MOF) studies has shifted to the development of MOFs with many metal nodes, also known as multi metallic MOF (MM-MOF). Many studies have shown that MM-MOF display much better performance compared to single metallic MOFs. In addition, derived MM-MOF products such as metal hybrids, MM-MOF composites, and MOF-on-MOF also provide interesting unique characteristics. In this review, we summarize the synthesis strategy of MM-MOF and their derivates in three different approaches, including one-pot synthesis/direct mixing, post-synthesis modification, and MOFs derivative preparation. In many applications, such as cancer markers detection, diabetic disease detection, metabolic disease detection, infectious disease detection, and toxic pollutant detection, MM-MOF based biosensors displayed excellent sensing performance as well as stability, selectivity, and reproducibility. This review provides a point of view on the recent development, preparation, and application of MM-MOF including the challenge and future prospect of this material.

This study reports on an enzymatic glucose sensor based on mesoporous TiO2nanoparticles (MTNPs) synthesized by a simple solvothermal method. The unique structure of MTNPs with a fairly homogenous shape, porous, and high crystallinity is the consequence of the use of PVP yang during the synthesis process. PVP plays an important role in creating the uniform morphology and mesoporous structure of MTNPs-2. The success of glucose oxidase immobilization on the surface of MTNPs was proven by FTIR and UV–vis characterizations. The prepared GCE/MTNPs-2/GOx electrode successfully detects glucose molecules with good sensing performance with a sensitivity of 0.4098 μA mM−1cm−2, a wide linear range of 0.1–1 mM, and a relatively low detection limit of 73 μM.

Electrochemical biosensors have attracted a tremendous attention for many researchers recently due to its facile synthesis process, tunability easiness by tailoring the material properties or composition, and wide range of biological analyte types detection. To obtain an excellent electrochemical biosensor performance, a material that facilitates fast electron transfer, large surface area, excellent electrocatalytic activity, and abundant available sites for bioconjugation is immensely needed. Metal-organic frameworks in the two-dimensional form (2D MOFs) provide all of the criteria needed as the sensing material for electrochemical biosensors application. However, the design and preparation of 2D MOFs, which have high stability and sensitivity as well as good selectivity for biological analyte detection, is still quite challenging. This review provides the recent studies and development of 2D MOFs as electrochemical biosensor. A detailed discussion about 2D MOFs structures, their synthesis strategy and control, 2D MOFs materials in electrochemical biosensor application, and the future challenges is thoroughly explained in this review. Hopefully, this review will also provide a new inspiration to advance future studies of 2D MOFs materials development as electrochemical biosensor.