3D Prussian blue/Pt decorated carbon nanofibers based screen-printed microchips for the ultrasensitive hydroquinone biosensing

CoCu@NC Nanozyme with pH-Switchable and Dual Enzymatic Activity: Highly Sensitive Colorimetric Sensing of Doxorubicin and Naked-Eye Detection of H2O2-Induced DNA Damage

The development of nanomaterials with multienzyme activity for advanced sensing and biosensing assays has attracted attention. In this study, a Cu-Co bimetallic nitrogen-doped carbon catalyst (CoCu@NC) was synthesized. The prepared nanomaterials exhibit catalase- and oxidase-like mimicking activities by adjusting the pH. The catalase-like activity of the CoCu@NC was investigated by quenching of terephthalic acid (TA) fluorescence at pH 11 in the presence of H2O2, while its oxidase behavior was confirmed by oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) as chromogenic substrate in the presence of O2 at pH 3. Furthermore, CoCu@NC's oxidase-like activity was used successfully to detect hydroquinone (HQ) at a concentration range of 1-900 nM with a detection limit of 0.22 nM and the anticancer drug doxorubicin (DOX) with a wide linear response ranging from 5 fM to 200 pM and an exceptionally low detection limit of 1.66 fM by reduction of oxTMB to TMB. DOX interacts in situ with single-stranded (ssDNA) and double-stranded DNA (dsDNA), reducing the quinone ring in its structure to hydroquinone (HQ) and oxidizing guanine bases to 8-oxoguanine. Based on this phenomenon, we designed a label-free colorimetric sensor for measuring DNA damage (ranging from 1 pM to 1 μM), in which this sensor operates by the disappearance of the blue oxTMB solution and the presence of the DNA/DOX. Furthermore, this designed sensor is sensitive to the number of guanine bases in ssDNA and dsDNA. As the number of guanine bases (1-12) in DNA sequences increases, a greater color change is observed. Finally, in the presence of H2O2-induced DNA damage, no intercalation occurred between DOX and the DNA-damaged sequences, with the color change observable with the naked eye. Therefore, this visualization assay demonstrates a low-cost, simple, rapid, sensitive, and effective method for detecting DOX drug and damaged DNA. Additionally, CoCu@NC magnetic nanostructures could be easily recollected and reused by applying a magnetic field.

Mesoporous DNA-Co@C nanofibers knitted aptasensors performing onsite determination of trace kanamycin residues

The abuse of kanamycin (KAN) poses an increasing threat to human health by contaminating agricultural and animal husbandry products, drinking water, and more. Therefore, the sensitive detection of trace KAN residues in real samples is crucial for monitoring agricultural pollution, ensuring food safety, and diagnosing diseases. However, traditional assay techniques for KAN rely on bulky instruments and complicated operations with unsatisfactory detection limits. Herein, we developed a novel label-free aptasensor to achieve ultrasensitive detection of KAN by constructing mesoporous DNA-cobalt@carbon nanofibers (DNA-Co@C-NFs) as the recognizer. Leveraging the extended π-conjugation structure, prominent surface area, and abundant pores, the Co@C-NFs can effectively load aptamer strands via π-π stacking interactions, serving as KAN capturer and reporter. Due to the change in DNA configuration upon binding KAN, this aptasensor presented an ultralow detection limit and ultra-wide linear range, along with favorable precision and selectivity. Using real tap water, milk, and human serum samples, the aptasensor accurately reported trace KAN levels. As a result, this convenient and rapid autosensing technique holds promise for onsite testing of other antibiotic residues in agriculture, food safety, and clinical diagnosis.

Nanomaterial-based electrochemical enzymatic biosensors for recognizing phenolic compounds in aqueous effluents

With the rapid development of industrial society, phenolic pollutants already identified in water are severe threats to human health. Traditional detection techniques like chromatography are poor in the ability of cost-effectiveness and on-site detection. In recent years, electrochemical enzymatic biosensors have attracted increasing attention for use in the recognition of phenolic compounds, which is considered an effective strategy for the product transfer of portable analytical devices. Although electrochemical enzymatic biosensors provide a fast, accurate on-site detection technique, the difficulties of enzyme deactivation, poor stability and low sensitivity remain to be solved. Thus, effective immobilization methods of enzymes and nanomaterials with excellent properties have been extensively researched to obtain a high-sensitivity and high-stability biosensing platform. Simultaneous detection of multiple phenols may become the focus of further research. In this review, we provide an overview of recent progress toward electrochemical enzymatic biosensors for the detection of phenolic compounds, including enzyme immobilization approaches and advanced nanomaterials, especially nanocomposites with attractive properties such as good conductivity, high specific surface area, and porous structure. We will comprehensively discuss the features and mechanisms of the main enzymes adopted in the construction of different phenolic biosensors, as well as traditional methods (e.g., adsorption, covalent bonding, entrapment, encapsulation, cross-linking) of enzyme immobilization. The most effective method is based on the properties of enzymes, supports and application objective because there is no one-size-fits-all method of enzymatic immobilization. The emphasis will be given to various advanced nanomaterials, including their special nanostructures, preparation methods and performance. Finally, the main challenges in future research on electrochemical phenolic biosensors will be discussed to provide further perspectives for practical applications in dynamic and on-site monitoring. We believe this review will deliver an important inspiration for the construction of novel and high-performance electrochemical biosensors from enzyme selection to nanomaterial design for the detection of various hazardous materials. We believe this review will deliver an important inspiration on the construction of novel and high-performance electrochemical biosensors from the enzyme selection to the nanomaterial design for detections of various hazardous materials.

Molecularly imprinted sensing platform based on electrochemically modified graphite paper for efficient detection of 3-monochloropropane-1,2-diol

In this study, a molecularly imprinted polymer (MIP) electrochemical sensor based on electrochemically modified graphite paper (EM-GP) was developed for the detection of 3-MCPD for the first time. To this end, Prussian blue (PB) was electrodeposited on EM-GP to yield uniformly distributed PtNPs. The successful preparation of Pt@PB/EM-GP was verified by SEM, Raman spectroscopy, XRD,XPS, and EDS. MIP was then prepared by CV electropolymerization with template molecules (3-MCPD), and density functional theory (DFT) at M06-2X/6-31 + g (d,p) level was used to calculate the molecular-level interaction between 3-MCPD and MIP. Under the optimum conditions, the dynamic linear range of the sensing platform varied from 1 × 10^-8mol/L to 5 × 10^-5mol/L with a detection limit estimated to 5 × 10^-9 mol/L (S/N = 3). Overall, these findings look promising for the construction of selective and quick detection platforms of 3-MCPD in food samples.

A highly efficient rGO grafted MoS2 nanocomposite for dye adsorption and electrochemical detection of hydroquinone in wastewater

Scheme depicting the synthesis and the fabrication of rGO–MoS2 nanocomposite-based enzymatic biosensor for estimation of hydroquinone.