Highly selective detection of adenine and guanine by NH2-MIL-53(Fe)/CS/MXene nanocomposites with excellent electrochemical performance

Imine-linked covalent organic framework with high crystallinity for constructing sensitive purine bases electrochemical sensor

In this work, a covalent organic framework (TADM-COF) with high crystallinity and large specific surface area (2597 m2 g-1) has been successfully synthesized using 1,3,5-(4-aminophenyl) benzene (TAPB) and 2,5-dimethoxy-p-phenyldiformaldehyde (DMTP). The COF was grown in situ on oxide particles to form core-shell nanocomposites (SiO2@TADM COF, Fe3O4@TADM COF and Co3O4@TADM COF) to realize its function as a shell material. Among them, the Co3O4@TADM COF with the highest electrochemical response to purine bases was further cross-linked with multi-walled carbon nanotubes (MWCNT) to construct a novel electrochemical sensor (Co3O4@TADM COF/MWCNT/GCE) for detection of purine bases. In this nanocomposite, Co3O4 possesses rich catalytic active sites, MWCNT ensures superior electrical conductivity and COF provides a stable environment for electrocatalytic reactions as the shell. At the same time, regular pore structure of the COFs also offers smooth channels for the transfer of analytes to the catalytic site. The synergistic effect among the three components showed remarkable sensing performance for the simultaneous detection of guanine (G) and adenine (A) with a wide linear range of 0.6-180 μM and low limits of detection (LODs) of 0.020 μM for G and 0.024 μM for A (S/N = 3), respectively. The developed sensor platform was also successfully applied in the detection of purine bases in thermally denatured herring DNA extract. The work provided a general strategy for amplifying signal of COF and its composite in the electrochemical sensing.

Highly crystalline polyimide covalent organic framework as electrochemical sensing platform for the ultrasensitive detection of purine bases in DNA

It is of great significance to propose simple methods to detect DNA bases sensitively for biological analysis and medical diagnosis. Herein, a highly crystalline polyimide covalent organic framework (TAPM-COF) has been successfully synthesized via a solvothermal route using pyromellitic dianhydride (PMDA) and tris(4-aminophenyl) amine (TAPA), which possessed large specific surface area (2286 m2 g-1) and excellent thermal stability. Intriguingly, the crystallinity of the TAPM-COF improved significantly with the increase of water content in the reaction medium. To verify this phenomenon, we synthesized TPPM-COF with two pores by pyromellitic dianhydride (PMDA) and N,N,N',N'-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA), which bonding was similar to TAPM-COF. Furthermore, the prepared TAPM-COF-0.3 was used to construct a novel and independent electrochemical biosensor on glassy carbon electrode for simultaneously determination of adenine (A) and guanine (G) without other additives. However, to further improve signal of TAPM-COF in electrochemical sensing, the crystalline TAPM-COF-0.3 can be readily integrated with amino-functionalized multiwalled carbon nanotubes (NH2-MWCNT) to form core-shell TAPM-COF-0.3@NH2-MWCNT driven by a π-π stacking interaction for more sensitive electrochemical sensing toward purine bases. In comparison to TAPM-COF/GCE, the TAPM-COF@NH2-MWCNT/GCE exhibited more favorable linear range and lower limit of detection. The work provided a new strategy for amplifying signal of COF in the field of electrochemical sensors.

Constructed MXene matrix composites as sensing material and applications thereof: A review

Most studies on MXene matrix composites for sensor development have primarily focused on synthesis and application. Nevertheless, there is currently a lack of research on how the introduction of different materials affects the sensing properties of these composites. The rapid development of MXene has raised intriguing questions about improving sensor performance by combining MXene with other materials such as polymers, metals and inorganic non-metals. This review will concentrate on the construction of MXene-based composites and explore ways to enhance their sensor applications. Specifically, this review describes why the introduction of materials to the system brings the advantage of low concentration and high sensitivity assays, as well as the MXene-based frameworks that have been recently investigated. Lastly, in order to capture the current trend of MXene-based composites in sensor applications and identify promising research directions, this review will critically evaluate the potential applications of newly developed MXene systems.