New Metal Complexes and Metal-Organic Frameworks (MOFs) with Potential Biological Applications.

As a cornerstone of synthetic chemistry, the coordination of organic ligands to ions/clusters has been used to prepare many types of materials, including metal complexes, metal–organic polyhedral, porous coordination polymers, porous coordination networks, and metal–organic frameworks (MOFs) [1]. These metal–organic materials are assembled by metal coordination, hydrogen bonding, electrostatic interactions or – stacking [2], exhibiting tunable structures, compositions and properties. Therefore, they are considered as promising candidates in the fields of catalysis, gas adsorption and separation, sensors, functional devices, etc [3]. Notably, biomedical applications have greatly benefited from the progress made by these metal–organic materials in the fields of diagnosis, monitoring, and therapy. Some of the biomedical applications of metal–organic materials include biosensors, biocatalysis, bioimaging, drug delivery, anticancer, antibacterial, and wound healing. This part mainly focuses on different types of metal complexes and MOFs for biomedical applications, specifically, for antibacterial and biosensing applications

Semiconducting CuxNi3-x(hexahydroxytriphenylene)2 framework for electrochemical aptasensing of C6 glioma cells and epidermal growth factor receptor

A 2D CuNi metal-organic framework (MOF) named CuxNi3-x(HHTP)2 was synthesized with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the linker and was used as a sensitive scaffold to adsorb aptamer strands for the electrochemical detection of living C6 glioma cells and one of their biomarkers, epidermal growth factor receptor (EGFR). Different from conventional MOFs, the CuxNi3-x(HHTP)2 MOF comprises long-range delocalized electrons, a graphene-analog nanostructure, multiple metal states (Cu0/Cu+/Cu2+ and Ni2+/Ni3+), and abundant oxygen vacancies. With these features, the CuxNi3-x(HHTP)2 MOF anchored a large amount of C6 cell-targeted aptamer strands via coordination among metal centers, oligonucleotides, pi-pi stacking, and van der Waals force. The CuxNi3-x(HHTP)2-based cytosensor showed a low limit of detection (LOD) of 21 cells mL-1 toward C6 glioma cells within a wide range from 50 cells mL-1 to 1 * 105 cells mL-1. Moreover, the proposed aptasensor displayed high selectivity, good stability, acceptable reproducibility, and a low LOD of 0.72 fg mL-1 for detecting EGFR with the concentration ranging from 1 fg mL-1 to 1 ng mL-1. The aptasensor based on the CuxNi3-x(HHTP)2 MOF exhibited superior sensing performance over those based on its monometallic analogues such as Cu3(HHTP)2 MOF and Ni3(HHTP)2 MOF. Hence, this sensing strategy based on a bimetallic semiconducting MOF shows great potential for cancer diagnosis

Electrochemical aptasensing strategy based on a multivariate polymertitanium-metal-organic framework for zearalenone analysis

: An electrochemical aptasensing strategy was developed with a novel bioplatform based on a multivariate titanium metal-organic framework, i.e. MTV polyMOF(Ti), to detect zearalenone (ZEN). MTV polyMOF(Ti) was prepared by using mixed linkers of polyether polymer (pbdc-xa or L8, pbdc = poly(1,4-benzenedicarboxylate) and 1,4-benzenedicarboxylic acid (H2bdc or L0) as well as tetrabutyl titanate as nodes (MTV polyMOF(Ti)-L8,0). Compared with Ti-MOFs synthesized by using the single ligand of L8 or L0, MTV polyMOF(Ti)-L8,0 shows more porous structure assembled with multilayered nanosheets. In light of the improved electrochemical activity and strong bioaffinity to the aptamer, the aptasensor based on MTV polyMOF(Ti)-L8,0 shows excellent performance for detecting ZEN with the ultralow detection limit at fg mL-1 level in the linear range of 10 fg mL-1 to 10 ng mL-1, along with good selectivity, reproducibility, stability, regenerability, and applicability

Trinuclear copper cluster-based COF with a high content of Cu–N2 single-atom sites: A multivariate signal-amplified photoelectrochemical aptasensor for the sensitive detection of mycotoxins

A novel amplified photoelectrochemical (PEC) aptasensor was developed based on the photoelectronic active and donor–acceptor (D–A) conjugated covalent organic framework (COF) for the efficient detection of zearalenone (ZEN). The D–A-conjugated COF synthesized through the reaction between trinuclear copper cluster (Cu3L3) and 4,4′,4′’-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) (denoted as Cu3L3–TAPT–COF) comprised rich Cu–N2 single-atom sites and exhibited high photoactivity, narrow bandgap, and n-type semiconductor feature. It was simultaneously employed as PEC electrode and bioplatform for anchoring single-stranded DNA. Moreover, the p-type ZnIn2S4 semiconductor anchors hairpin probe strands that hybridized with the ZEN-target aptamer. By combining the target-modulated competitive binding method and the multivariate signal-amplified strategy, the Cu3L3–TAPT–COF-based PEC aptasensor exhibited a wide linear range from 0.1 pg mL−1 to 20 ng mL−1 and a low detection limit of 24 fg mL−1, along with excellent and widespread practical applicability, offering promising applications in food safety

Aptamer-Templated Silver Nanoclusters Embedded in Zirconium Metal–Organic Framework for Bifunctional Electrochemical and SPR Aptasensors toward Carcinoembryonic Antigen

This study reported a novel biosensor based on the nanocomposite of zirconium metal–organic framework (Zr-MOF, UiO-66) embedded with silver nanoclusters (Ag NCs) using the carcinoembryonic antigen (CEA)-targeted aptamer as template (AgNCs@Apt@UiO-66). The synthesized AgNCs@Apt@UiO-66 nanocomposite not only possesses good biocompatibility, active electrochemical performance, and strong bioaffinity, but also can be dispersed to form two-dimensional nanocomposite with nanoscale thickness. As such, the use of the AgNCs@CEA-aptamer enables AgNC@Apt@UiO-66 with sensitive and selective detection capacity of trace CEA, further concurrently being exploited as scaffold for surface plasmon resonance spectroscopy (SPR) and electrochemical biosensors. The results showed that the proposed electrochemical AgNC@Apt@UiO-66-based aptasensor exhibits high sensitivity with a low detection limit (LOD) of 8.88 and 4.93 pg·mL^–1 deduced from electrochemical impedance spectroscopy and differential pulse voltammetry, respectively, within a broad linear range of the CEA concentration (0.01–10 ng·mL^–1). Meanwhile, the developed SPR biosensor exhibited a slightly high LOD of 0.3 ng·mL^–1 within the CEA concentration of 1.0–250 ng·mL^–1. Both the electrochemical and SPR aptasensors displayed high selectivity, good reproducibility, stability, acceptable regenerability, and applicability in real human serum samples. These results proved that the proposed aptamer-targeted Zr-MOF nanocomposite can be utilized in multiple-functionally biosensing, further promoting the potential application of Zr-MOF-related nanomaterials in clinical diagnosis