Recent Advances in MOF-Based Materials for Biosensing Applications

Metal-organic frameworks (MOFs) or coordination polymers have gained enormous interest in recent years due to their extraordinary properties, including their high surface area, tunable pore size, and ability to form nanocomposites with various functional materials. MOF materials possess redox-active properties that are beneficial for electrochemical sensing applications. Furthermore, the tunable pore size and high surface area improve the adsorption or immobilization of enzymes, which can enhance the sensitivity and selectivity for specific analytes. Additionally, MOF-derived metal sulfides, phosphides, and nitrides demonstrate superior electrical conductivity and structural stability, ideal for electrochemical sensing. Moreover, the functionalization of MOFs further increases sensitivity by enhancing electrode-analyte interactions. The inclusion of carbon materials within MOFs enhances their electrical conductivity and reduces background current through optimized loading, preventing agglomeration and ensuring uniform distribution. Noble metals immobilized on MOFs offer improved stability and catalytic performance, providing larger surface areas and uniform nanoparticle dispersion. This review focuses on recent developments in MOF-based biosensors specifically for glucose, dopamine, H2O2, ascorbic acid, and uric acid sensing.

Electrochemical sensor based on molecularly imprinted polypyrrole-MWCNTs-OH/covalent organic framework for the detection of ofloxacin in water

A platform was developed to accurately detect the content of ofloxacin (OFX) based on molecularly imprinted polypyrrole-MWCNTs-OH/1,3,5-Tris(4-aminophenyl) benzene (TAPB)-2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTP)-covalent organic framework (MIP-MWCNTs-OH/COF)-modified glassy carbon electrode (GCE) sensor (MIP-MWCNTs-OH/COF/GCE). The complex of MWCNTs-OH and COF synergistically enhanced the active area and electrochemical signal, based on which a molecularly imprinted membrane was polymerized on its surface to further improve the selectivity. Under optimized conditions, the prepared MIP-MWCNTs-OH/COF/GCE sensor exhibited strong detection performance to OFX in a linear range 1.969 × 10-11-9.619 × 10-9 M with the limit of detection (LOD, 3S/N) of 4.989 × 10-12 M, excellent selectivity, stability, and reproducibility. Furthermore, the MIP-MWCNTs-OH/COF/GCE sensor can be successfully applied to the detection of OFX in lake water and eye drops with a relative standard deviation (RSD) of less than 4.95%, indicating its high potential in practical applications.

Electrochemical analysis of anticancer and antibiotic drugs in water and biological specimens

The increasing prevalence of pharmaceuticals in water and complex matrices necessitates accurate measurement and monitoring of their environmental contamination levels. This is crucial not only for environmental conservation but also for comprehending the intricate mechanisms involved and developing more effective treatment approaches. In this context, electrochemical techniques show significant potential for the detection of pharmaceuticals across various matrices. Specifically, voltammetry is advantageous due to its rapid, straightforward, and cost-effective nature, allowing for the simultaneous analysis of multiple anticancer and antibiotic drugs. By utilizing nanomaterial-modified electrochemical sensors, the sensitivity and selectivity of detection methods can be significantly improved. The small size and customizable properties of nanomaterials enable these sensors to identify trace amounts of drugs in diverse samples. However, challenges persist in achieving reliable and accurate electrochemical monitoring of drugs in water and biological samples. Biofluids such as saliva, urine, and blood/serum, along with environmental samples from lakes and rivers, often contain numerous interfering substances that can diminish analyte signals. This review examines electrochemical methods and their potential applications for detecting pharmaceuticals and their metabolites, while also addressing the mechanisms of action and harmful effects of these drugs on both ecosystems and human health. Recent developments in electrochemical sensors utilizing nanomaterials for the detection of health-threatening pharmaceutical contaminants are examined, providing important insights into their underlying mechanisms. The emphasis is placed on the detection of anticancer agents and antibiotics, which relies on the electrocatalytic properties of the sensor materials. Additionally, discussions on density functional theory studies are included, along with an exploration of the emerging challenges and future directions in this area, aimed at enhancing readers' comprehension of the field and underscoring the necessary actions for a sustainable future.

Synthesis of highly luminescent core-shell nanoprobes in a single pot for ofloxacin detection in blood serum and water

Antibiotics are commonly used as antibacterial medications due to their extensive and potent therapeutic properties. However, the overconsumption of these chemicals leads to their accumulation in the human body via the food chain, amplifying drug resistance and compromising immunity, thus presenting a significant hazard to human health. Antibiotics are classified as organic pollutants. Therefore, it is crucial to conduct research on precise methodologies for detecting antibiotics in many substances, including food, pharmaceutical waste, and biological samples like serum and urine. The methodology described in this research paper introduces an innovative technique for producing nanoparticles using silica as the shell material, iron oxide as the core material, and carbon as the shell dopant. By integrating a carbon-doped silica shell, this substance acquires exceptional fluorescence characteristics and a substantial quantum yield value of 80%. By capitalising on this characteristic of the substance, we have effectively constructed a fluorescent sensor that enables accurate ofloxacin analysis, with a detection limit of 1.3 × 10-6 M and a linear range of concentrations from 0 to 120 × 10-6 M. We also evaluated the potential of CSIONPs for OLF detection in blood serum and tap water analysis. The obtained relative standard deviation values were below 3.5%. The percentage of ofloxacin recovery from blood serum ranged from 95.52% to 103.28%, and from 89.9% to 96.0% from tap water.

Quantitative monitoring ofloxacin in beef by TLC-SERS combined with machine learning analysis

Ofloxacin is one kind of quinolone antibiotic drugs, the abuse of ofloxacin in livestock and aquaculture may bring bacterial resistance and healthy problem of people. The illegally feeding cattle with ofloxacin will help it keep health, but the sedimentation of ofloxacin could bring problem in food safety. The accurate, simple and instant monitoring ofloxacin from beef by portable sensor was of vital issue in food quality. A simple and reliable method was proposed for instant and quantitative detecting ofloxacin in beef, in which the thin-layer chromatography (TLC) -surface-enhanced Raman scattering (SERS) spectroscopy was in tandem with machine learning analysis base one principal component analysis-back propagation neural network (PCA-BPNN). The TLC plate was composed with diatomite, that was function as the stationary phase to separate ofloxacin from beef. The real beef juice was directly casted onto the diatomite plate for separating and detecting. The directly monitor ofloxacin from beef was achieved and the sensitivity down to 0.01 ppm. The PCA-BPNN was used as reliable model for quantitative predict the concentration of ofloxacin, that shown superior accuracy compared with the traditional model. The results verify that the diatomite plate TLC-SERS combined with machine-learning analysis is an effective, simple and accurate technique for detecting and quantifying antibiotic drug in meat stuff to improve the food safety.

A direct electrochemical sensor based on covalent organic frameworks/platinum nanoparticles for the detection of ofloxacin in water

A direct electrochemical sensor based on covalent organic frameworks (COFs)/platinum nanoparticles (PtNPs) composite was fabricated for the detection of ofloxacin (OFX) in water. Firstly, the COF material was synthesized via the condensation reaction of 1,3,5-tris(4-aminophenyl)benzene (TAPB) with terephthalaldehyde (TPA) and integrated with PtNPs by in situ reduction. Then, TAPB-TPA-COFs/PtNPs composite was loaded onto the surface of the glassy carbon electrode (GCE) by drip coating to construct the working electrode (TAPB-TPA-COFs/PtNPs/GCE). The electrochemical performance of TAPB-TPA-COFs/PtNPs/GCE showed a significant improvement compared with that of TAPB-TPA-COFs/GCE, leading to a 3.2-fold increase in the electrochemical signal for 0.01 mM OFX. Under optimal conditions, the TAPB-TPA-COFs/PtNPs/GCE exhibited a wide linear range of 9.901 × 10-3-1.406 µM and 2.024-15.19 µM with a detection limit of 2.184 × 10-3 µM. The TAPB-TPA-COFs/PtNPs/GCE-based electrochemical sensor with excellent performance provides great potential for the rapid and trace detection of residual OFX.

An electrochemical sensor based on synergistic enhancement effects between nitrogen-doped carbon nanotubes and copper ions for ultrasensitive determination of anti-diabetic metformin

Metformin (MET) is the primary medicine for type II diabetes, which produces carcinogenic byproducts during chlorine disinfection, so the detection of MET in aqueous environment is crucial. In this work, an electrochemical sensor based on nitrogen-doped carbon nanotubes (NCNT) has been constructed for ultrasensitive determination of MET in the presence of Cu(II) ions. The excellent conductivity and rich π-conjugated structure of NCNT facilitate the electron transfer rate of fabricated sensor and benefit the adsorption of cation ions. Cu(II) ions can chelate with MET to form MET-Cu(II) complex, which are easily accumulated on the surface of NCNT through cation-π interaction. Attributing to the synergistic enhancement effects of NCNT and Cu(II) ions, the fabricated sensor exhibits excellent analytical performances with a low detection limit of 9.6 nmol L^-1, high sensitivity of 64.97 A mol^-1 cm^-2 and wide linear range of 0.3-10 μmol L^-1. The sensing system has been successfully applied for rapid (20 s) and selective determination of MET in real water samples with satisfactory recoveries (90.2 %-108.8 %). This study provides a robust strategy for MET detection in aqueous environment and holds great promise for rapid risk assessment and early warning of MET.

Cyclodextrin-metal-organic frameworks in molecular delivery, detection, separation, and capture: An updated critical review

Metal-organic frameworks (MOFs) are coordination compounds with tuneable structures and controllable functions. However, the biological toxicity of traditional MOFs materials is often inevitable, making their application in the biological field have many limitations. Therefore, frontier research increasingly focuses on developing biocompatible MOFs materials. Cyclodextrins (CDs), derived from starch, are favored by various biomaterials due to their good biosafety and are often seen in the preparation and application of MOFs materials. This review describes the features of MOFs materials, and the various preparation methods of CD-MOFs are analyzed in detail from the perspective of CD classification. Additionally, the promising applications of CD-MOFs materials for delivery, detection, separation, and capture of active molecules in recent studies are systematically discussed and summarized. In terms of safety, the CD-MOFs materials are meticulously summarized. Finally, this review presents the challenges and future prospects regarding the current CD-MOFs-based materials, which will shed new light on the application of such materials in various fields.

MXene-based composites as an electrochemical sensor for ultrasensitive determination of ofloxacin

Sensitive determination of ofloxacin (OFL) is very essential for human health and environmental protection. Here, a novel composite of gold nanoparticles(nAu)@MXene(Ti₃C₂T_x)/poly-p-aminobenzene sulfonic acid (PABSA) was fabricated on the surface of glassy carbon electrode (GCE) and used to sensitively determine OFL. The results of experiments showed that the obtained nAu@Ti₃C₂T_x/PABSA/GCE electrode could be used as an electrochemical sensor to directly detect ofloxacin (OFL) by differential pulse voltammetry (DPV). Under the optimal conditions, the proposed electrode displayed a broader linear range and a lower detection limit (LOD) for OFL determination when it was compared to those similar sensors. The linear range was from 5.0 × 10^-8 to 5.0 × 10^-4 mol/L and the LOD was 3.7 × 10^-8 mol/L (S/N = 3). The nAu@Ti₃C₂T_x/PABSA/GCE electrode also showed good selectivity, repeatability, and reproducibility. Finally, the proposed electrode was used to detect OFL in commercial samples by the standard addition method. The obtained recovery was from 97.3% and 105.7% showing its potential applications in actual sample analysis.

Organo-macrocycle-containing hierarchical metal-organic frameworks and cages: design, structures, and applications

Developing hierarchical ordered systems is challenging. Using organo-macrocycles to construct metal-organic frameworks (MOFs) and porous coordination cages (PCCs) provides an efficient way to obtain hierarchical assemblies. Macrocycles, such as crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, can be incorporated within MOFs/PCCs and they also endow the resultant composites with enhanced properties and functionalities. This review summarizes recent developments of organo-macrocycle-containing hierarchical MOFs/PCCs, emphasizing applications and structure-property relationships of these hierarchically porous materials. This review provides insights for future research on hierarchical self-assembly using macrocycles as building blocks and functional ligands to extend the applications of the composites.

Determination of luteolin in Chrysanthemum tea with a ultra-sensitive electrochemical sensor based on MoO3/poly(3,4-ethylene dioxythiophene)/gama-cyclodextrin metal-organic framework composites

Chrysanthemum tea is a tranditional Chinese health drink, which contains luteolin, a flavonoid with vesatile health benefit activities. Herein, A sensitive electrochemical sensor based on composite materials consisting of MoO₃ nanorods, poly (3, 4-ethylene dioxyethiophene)(PEDOT), and γ-cyclodextrin metal-organic framework(CD-MOF) was prepared.The materials were characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Due to the synergisticeffects of the materials, the sensor showed a wide linear range of 0.4 nM -1800 nM and a low detection limit (LOD) of 0.1 nM (S/N = 3) for luteolin under optimized conditions. Besides, the influences of some coexistent phenolic compounds and common metal ions on luteolin detection were evaluated and no significant interference was observed. Finally, the sensor was successfully applied to the detection of luteolin in real Chrysanthemum tea samples.

Ultrasensitive detection of PCB77 based on Exonuclease III-powered DNA walking machine

In view of the urgent need to determine polychlorinated biphenyls (PCBs) in the environment, we report a simple and sensitive electrochemical aptasensor to detect 3,3',4,4'-tetrachlorobiphenyl (PCB77) based on Exonuclease III-powered Deoxyribonucleic Acid (DNA) walking machine using poly (diallyldimethylammonium chloride) (PDDA), which was functionalized hollow porous graphitic carbon nitride/ Ni-Co hollow nanoboxes/ Au-Pd-Pt nanoflowers composite material. Upon the addition of PCB77, the specific binding between PCB77 and the aptamer (Apt) could trigger the Exo III-assisted cyclic amplification process and release unlocking probes to deblock the Swing arm/Blocker duplex. Finally, the hybridized hairpin 3 (HP3), a short oligonucleotide, was left on the electrode via Exo III digestion of hybridized HP2, and thus a strong methylene blue (MB) signal was obtained. As expected, the proposed aptasensor exhibits exceptional PCB77 detection performances with a very low detection limit of 5.13 pg/L and a wide linear range of 0.01-100 ng/L based on the calibration curve. Moreover, the aptasensor presents a high level of selectivity and stability, with an acceptable degree of reproducibility. The results of this study have indicated that the proposed aptasensor has great potential application prospects, as demonstrated by its successful use in real environmental water samples.

Ru(bpy)32+ encapsulated cyclodextrin based metal organic framework with improved biocompatibility for sensitive electrochemiluminescence detection of CYFRA21-1 in cell

Metal-organic frameworks (MOFs) have attracted strong interest from researchers. Here, for the first time, we report a sandwich-type electrochemiluminescent biosensor as a signal probe prepared from cyclodextrin-based MOF (CD-MOF)-encapsulated Ru(bpy)₃²⁺. Due to the combination of the two materials, the obtained CD-MOF@Ru(bpy)₃²⁺ nanocomposites exhibited excellent biocompatibility and electrochemical performance. At the same time, CD-MOF@Ru(bpy)₃²⁺ adhered to the electrode surface closely because Ru(bpy)₃²⁺ was successfully encapsulated by the CD-MOF. In this paper, CD-MOF@Ru(bpy)₃²⁺ and glutaraldehyde were modified on a glassy carbon electrode (GCE) surface to provide excellent conductivity and to immobilize primary antibodies. Under the optimal experimental conditions, the established biosensor exhibited high sensitivity, a low limit of detection and a great linear range for cytokeratin 19 fragment antigen 21-1 (CYFRA21-1). Finally, this designed biosensor was further applied to the determination of CYFRA21-1 in A549 lung cancer cells. According to the results of the toxicity test, CD-MOF@Ru(bpy)₃²⁺ exhibited hypotoxicity to living bodies. These results all indicate that this biosensor has great potential for a promising approach to the evaluation of biomarkers.

Synergizing Functional Nanomaterials with Aptamers Based on Electrochemical Strategies for Pesticide Detection: Current Status and Perspectives

Owing to the high toxicity and large-scale use of pesticides, it is imperative to develop selective, sensitive, portable, and convenient sensors for rapid monitoring of pesticide. Therefore, the electrochemical detection platform offers a promising analytical approach since it is easy to operate, economical, efficient, and user-friendly. Meanwhile, with advances in functional nanomaterials and aptamer selection technologies, numerous sensitivity-enhancement techniques alongside a widespread range of smart nanomaterials have been merged to construct novel aptamer probes to use in the biosensing field. Hence, this study intends to highlight recent development and promising applications on the functional nanomaterials with aptamers for pesticides detection based on electrochemical strategies. We also reviewed the current novel aptamer-functionalized microdevices for the portability of pesticides sensors. Furthermore, the major challenges and future prospects in this field are also discussed to provide ideas for further research.

Raman spectroscopy-based sensitive, fast and reversible vapour phase detection of explosives adsorbed on metal–organic frameworks UiO-67

A sensitive, selective, rapid, and reversible detection of explosive molecules in the vapour phase, adsorbed on metal–organic frameworks (MOFs) under ambient laboratory conditions is demonstrated using Raman spectroscopy.

Platinum nanoparticle-deposited multi-walled carbon nanotubes as a NADH oxidase mimic: characterization and applications

The effective regeneration of bioactive NAD+ plays an important role in numerous dehydrogenase-dependent applications including biocatalysis and biosensing. However, this process usually suffers from high thermodynamic barrier, instability and high cost associated with natural enzymes. The emergence of nanomaterials with enzyme mimic characteristics has offered a potential alternative to many enzyme-catalyzed processes. Platinum nanoparticles (PtNPs), for example, have been extensively studied for their peroxidase- and oxidase-like activities. However, their behavior as a NADH oxidase mimic has barely been characterized in detail. Herein, we report a facile approach for preparing PtNP-deposited multi-walled carbon nanotubes (PtNPs@MWCNTs) as the nanozyme for NADH oxidation. Its enzymatic activity was investigated in depth, revealing that it is a NADH oxidase instead of a peroxidase and the catalytic process generates O2˙-, rather than OH˙ or 1O2, from dissolved O2. The recovery yield of bioactive NAD+ regeneration by the nanozyme could reach ∼100% with a total turnover number of ∼6000. Besides, it exhibited terrific electrochemical performance for NADH oxidation and sensing by greatly boosting the response and lowering the oxidation overpotential. It could also work on biomimetic cofactors with even higher activity. Finally, xylose dehydrogenase was immobilized with the nanozyme to constitute a hybrid bioelectrode for xylose sensing. The biosensor had a xylose detecting range of 5-400 μM with the limit of detection as low as 1 μM and can retain its performance after being reused several times. Our results suggest that the PtNPs@MWCNTs characterized as a NADH oxidase nanozyme hold great promise in the applications of biocatalysis and biosensing, which intensively deal with dehydrogenases and natural or biomimetic cofactors.

Detection of anabolic steroids via cyclodextrin-promoted fluorescence modulation

Reported herein is the detection of anabolic steroids through the use of cyclodextrin-promoted interactions between the analyte of interest and a high quantum yield fluorophore, which lead to measurable, analyte-specific changes in the fluorophore emission signal. By using a variety of β-cyclodextrin derivatives (unmodified β-cyclodextrin, methyl-β-cyclodextrin, and 2-hydroxypropyl-β-cyclodextrin) in combination with high quantum yield fluorophore rhodamine 6G, we detected five anabolic steroid analytes with 100% differentiation between structurally similar analytes and micromolar level limits of detection. Overall, these results show significant potential in the development of practical, fluorescence-based steroid detection devices.