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The present study aims to develop an electroanalytical method to determine one of the most significant antineoplastic agents, topotecan (TPT), using a novel and selective molecular imprinted polymer (MIP) method for the first time. The MIP was synthesized using the electropolymerization method using TPT as a template molecule and pyrrole (Pyr) as the functional monomer on a metal-organic framework decorated with chitosan-stabilized gold nanoparticles (Au-CH@MOF-5). The materials' morphological and physical characteristics were characterized using various physical techniques. The analytical characteristics of the obtained sensors were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). After all characterizations and optimizing the experimental conditions, MIP-Au-CH@MOF-5 and NIP-Au-CH@MOF-5 were evaluated on the glassy carbon electrode (GCE). MIP-Au-CH@MOF-5/GCE indicated a wide linear response of 0.4-70.0 nM and a low detection limit (LOD) of 0.298 nM. The developed sensor also showed excellent recovery in human plasma and nasal samples with recoveries of 94.41-106.16 % and 95.1-107.0 %, respectively, confirming its potential for future on-site monitoring of TPT in real samples. This methodology offers a different approach to electroanalytical procedures using MIP methods. Moreover, the high sensitivity and selectivity of the developed sensor were illustrated by the ability to recognize TPT over potentially interfering agents. Hence, it can be speculated that the fabricated MIP-Au-CH@MOF-5/GCE may be utilized in a multitude of areas, including public health and food quality., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A new electrochemiluminescence (ECL) cytosensor is proposed for the simultaneous determination of phosphatidylserine (PS) and epidermal growth factor receptor (EGFR) based on the ECL signals of metal-organic framework-5 (MOF-5) loaded CdS quantum dots and N-(aminobutyl)-N-(ethylisoluminol)-polyethylenimine capped Au and Ag nanoparticles. Apoptosis promotes the exposure of PS and reduces the expression of EGFR in cell membranes. Two spatially resolved areas on dual-disk glassy carbon electrodes were designed to eliminate the interference from different ECL probes. Using HepG2 cells treated with resveratrol to induce apoptosis, the cytosensor exhibited high sensitivity, simplicity, and high reproducibility, demonstrating its potential in drug screening and rapid apoptotic cell detection. The strategy reported provides a promising platform for the highly sensitive cytosensing and convenient screening of clinically relevant anticancer drugs., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A novel aptasensor has been designed for quantitative monitoring of epinephrine (EP) based on cerium metal-organic framework (CeMOF) loaded gold nanoparticles (AuNPs). The aptamer, specific to EP, is immobilized on a flexible screen-printed electrode modified with AuNPs@CeMOF, enabling highly selective binding to the target biomolecule. Under optimized operational conditions, the peak currents using voltammetric detection measured at voltage of 83 mV (vs. Ag/AgCl) for epinephrine exhibit a linear increase within concentration in the range 1 pM-10 nM. Following this detection strategy, a boasted limit of detection of 0.3 pM was achieved, surpassing the sensitivity of most reported methods. The developed biosensor showcased exceptional performance in detection of EP in spiked serum sample, with remarkable recovery range of  95.8-113% and precision reflected by low relative standard deviation (RSD) ranging from 2.23 to 6.19%. These results indicate the potential utility of this biosensor as a valuable clinical diagnostic tool. Furthermore, in vitro experiments were carried out using the presented biosensor to monitor the release of epinephrine from PC12 cells upon extracellular stimulation with K + ions., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

A novel ratiometric electrochemical sensor was developed based on a carbon cloth electrodeposited with silver nanoparticles and drop-coated by covalent organic framework (COF-LZU1) for simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS). Carbon cloth exhibited a significantly larger electrochemical active area than common glassy carbon electrodes (27.5 times). Silver nanoparticles not only provided a stable reference signal but also enhanced electroactivity for the oxidation of BPA and BPS. COF-LZU1 with good adsorption performance and large periodic π-arrays promoted the enrichment of BPA and BPS to further increase the current response. Compared with the traditional single-signal electrochemical sensor, the developed ratiometric sensor exhibited better reproducibility and a wider linear range for BPA and BPS from 0.5 to 100 μM with a limit of detection of 0.15 μM. Furthermore, the developed sensor showed excellent stability and superior anti-interference ability. The real sample analysis for BPA and BPS has been successfully carried out in mineral water, electrolyte drink, tea, juice, and beer with recoveries of 88.3-111.7%. The developed ratiometric sensor is expected to be a candidate for the preparation of other electrochemical sensors and the analysis of additional practical samples., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Horseradish peroxidase (HRP) was highly loaded into large holes of nanometer-scale metal-organic frameworks (i.e., PCN-333(Al)) for signal amplification in enzyme-linked immunosorbent assay (ELISA). The enzyme-labeled antibody complex prepared using nanometer-scale PCN-333(Al) maintained a high catalytic efficiency. Its V m and K cat values with 3,3',5,5'-Tetramethylbenzidine (TMB)-H 2 O 2 as substrates were 4.84 × 10 -5  mM/s and 4.84 × 10 4  min -1 , respectively. We demonstrated an HRP@PCN-333 signal amplification strategy for colorimetric assay of human prostate-specific antigen (PSA). The linear range of PSA detection by using this method was 15-165 pg/mL, and the limit of detection was 6 pg/mL (S/N = 3), indicating the potential application of this method in detecting disease markers under clinical conditions. The presented strategy exhibited the characteristics of significantly increased amount of labeled enzymes, improved stability and utilization of enzymes, simple preparation process of enzyme-labeled antibodies, and low cost., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Herein, we report a new polydopamine (PDA)-coated metal-organic framework (MOF) as a label to improve the sensitivity of lateral flow immunoassay (LFIA). The MOF, UiO-66-NH 2 , was synthesized via the hydrothermal method, and it exhibited the advantageous features of ordered pore structure, strong absorbance, and high specific surface area. Subsequently, UiO-66-NH 2 was coated with PDA to improve the antibody coupling effectivity and light absorption ability. The optical intensity and antibody coupling efficiency of UiO-66@PDA were superior to those of gold nanoparticles (AuNPs). Under the optimum condition, the limit of detection and cutoff value of UiO-66@PDA-LFIA in detecting enrofloxacin were 0.045 and 1.0 ng/mL, respectively, which were lower than those of AuNPs-LFIA (0.095 and 5 ng/mL). The recoveries of UiO-66@PDA-LFIA in low-fat milk and whole milk were 85.6-107.4% and 79.3-115.5%, respectively, with coefficients of variation of 2.91-9.59% and 3.91-11.8%, respectively, as further confirmed by liquid chromatography-tandem mass spectrometry. These results indicate that UiO-66@PDA can be used as a novel probe for LFIA development and applications. Graphical abstract., (© 2022. Springer-Verlag GmbH Germany, part of Springer Nature.)

Chains of nickel nanoparticles coated with few nitrogen-doped graphitic carbon layers (Ni@NC) are synthesized by hydrogen-assisted pyrolysis of Ni-ZIF. Hydrogen and temperature can play key roles in the formation of oriented Ni@NC nanoparticle chains, and carbon shells can protect Ni nanoparticles from external oxidation and aggregations. Under the optimized potential (0.60 V vs. Ag/AgCl), the Ni@NC7H nanoparticle chains obtained at 700 °C under H 2 /Ar atmosphere (Ni@NC7H) demonstrate outstanding performances, such as high sensitivity of 1.44 mA mM -1  cm -2 (RSD = 1.0%), low detection limit of 0.34 μM (S/N = 3), broad linear range from 1 μM to 1.81 mM, and excellent application potential in artificial sweat and human serum. Therefore, the findings above indicate that this study will provide a general methodology for the synthesis of chains-like core-shell nanoparticle electrocatalysts for non-enzymatic glucose detection., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

An ultrasensitive electrochemical sensor has been constructed for the detection of single nucleotide polymorphisms (SNPs) based on DNA-functionalized Cd-MOFs-74 as cascade signal amplification probe under enzyme-free conditions. Interestingly, the introduction of an auxiliary probe did not disturb the detection of SNP targets, but could bind more Cd-MOFs-74 signal elements to enhance the different pulse voltammetry electrochemical signal 2~3 times as compared to sensing system without auxiliary probe, which obviously improves the sensitivity of the proposed sensor. Experimental results taking p53 tumor suppressor gene as SNP model demonstrated that the proposed method can be employed to sensitively and selectively detect target p53 gene fragment with a linear response ranging from 0.01 to 30 pmol/L (detection limit of 6.3 fmol/L) under enzyme-free conditions. Utilizing this strategy, the ultrasensitive SNP electrochemical sensor is a promising tool for the determination  of SNPs in biomedicine. Graphical Abstract., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)