Rapid detection of eugenol in perch utilizing electrochemical method by transition metal substituted polyoxometalates

Food safety concerns caused by the application of spice allergens to fish anaesthesia. In this paper, a chitosan-reduced graphene oxide/polyoxometalates/poly-l-lysine (CS-rGO/P₂Mo₁₇Cu/PLL) modified electrode was constructed by electrodeposition and successfully applied to the quantitative analysis of eugenol (EU). The detection limit was 0.4490 μM in the linear range of 2x10^-6 M to 1.4x10^-5 M. It was applied to the determination of EU residues in kidney, liver and meat tissues of perch with recoveries ranging from 85.43 to 93.60%. Besides, the electrodes demonstrate high stability (2.56% drop in current value after 70 days at room temperature), high reproducibility (RSD of 4.87% for 6 parallel electrodes) and extremely fast response time. This study provided a new material for the electrochemical detection of EU.

Direct Electron Transfer of Glucose Oxidase on Pre-Anodized Paper/Carbon Electrodes Modified through Zero-Length Cross-Linkers for Glucose Biosensors

A disposable paper-based glucose biosensor with direct electron transfer (DET) of glucose oxidase (GOX) was developed through simple covalent immobilization of GOX on a carbon electrode surface using zero-length cross-linkers. This glucose biosensor exhibited a high electron transfer rate (ks, 3.363 s-1) as well as good affinity (km, 0.03 mM) for GOX while keeping innate enzymatic activities. Furthermore, the DET-based glucose detection was accomplished by employing both square wave voltammetry and chronoamperometric techniques, and it achieved a glucose detection range from 5.4 mg/dL to 900 mg/dL, which is wider than most commercially available glucometers. This low-cost DET glucose biosensor showed remarkable selectivity, and the use of the negative operating potential avoided interference from other common electroactive compounds. It has great potential to monitor different stages of diabetes from hypoglycemic to hyperglycemic states, especially for self-monitoring of blood glucose.

Graphene, an Interesting Nanocarbon Allotrope for Biosensing Applications: Advances, Insights, and Prospects

Graphene, a relatively new two-dimensional (2D) nanomaterial, possesses unique structure (e.g. lighter, harder, and more flexible than steel) and tunable physicochemical (e.g. electronical, optical) properties with potentially wide eco-friendly and cost-effective usage in biosensing. Furthermore, graphene-related nanomaterials (e.g. graphene oxide, doped graphene, carbon nanotubes) have inculcated tremendous interest among scientists and industrials for the development of innovative biosensing platforms, such as arrays, sequencers and other nanooptical/biophotonic sensing systems (e.g. FET, FRET, CRET, GERS). Indeed, combinatorial functionalization approaches are constantly improving the overall properties of graphene, such as its sensitivity, stability, specificity, selectivity, and response for potential bioanalytical applications. These include real-time multiplex detection, tracking, qualitative, and quantitative characterization of molecules (i.e. analytes [H₂O₂, urea, nitrite, ATP or NADH]; ions [Hg²⁺, Pb²⁺, or Cu²⁺]; biomolecules (DNA, iRNA, peptides, proteins, vitamins or glucose; disease biomarkers such as genetic alterations in BRCA1, p53) and cells (cancer cells, stem cells, bacteria, or viruses). However, there is still a paucity of comparative reports that critically evaluate the relative toxicity of carbon nanoallotropes in humans. This manuscript comprehensively reviews the biosensing applications of graphene and its derivatives (i.e. GO and rGO). Prospects and challenges are also introduced.

Self-Propelled and Targeted Drug Delivery of Poly(aspartic acid)/Iron-Zinc Microrocket in the Stomach

For many medical treatments, particularly cancer, it is necessary to develop a biocompatible microscale device that can carry a sufficient amount of a drug and deliver it to target sites. While chemically powered micromotors have been applied in live animal therapy, many of them are difficult to biodegrade in vivo, which might cause toxicity and side effects. Here, we report on a microdevice that consists of a poly(aspartic acid) (PASP) microtube, a thin Fe intermediate layer, and a core of Zn. This device can be propelled using gastric acid as a fuel. After adsorption of doxorubicin onto a PASP surface, the microrocket can carry drugs, magnetically locate targets, permeate the gastric mucus gel layer, and increase drug retention in the stomach without inducing an obvious toxic reaction. All materials in the microrockets are biocompatible and biodegradable and can be readily decomposed by the gastric acid or by proteases in the digestive tract. Such microrockets, made with poly(amino acid)s, will extend the practical biomedical applications of micro- and nanomotors.

A novel electrochemical immunosensor for highly sensitive detection of prostate-specific antigen using 3D open-structured PtCu nanoframes for signal amplification

Herein, a novel electrochemical ultrasensitive immunosensor was designed for detecting prostate-specific antigen (PSA) with three-dimensional (3D) PtCu hollow nanoframes (PtCu HNFs) as signal amplification. The highly opened PtCu HNFs were synthesized by a one-pot solvothermal method with cetyltrimethylammonium chloride (CTAC) and trishydroxymethyl aminomethane (Tris) as co-structuring directors. The architectures enlarged the loading of prostate specific antibodies (Ab) and efficiently catalyzed hydrogen peroxide (H₂O₂) reaction, ultimately amplifying the signals. And polylysine was used to disperse PtCu HNFs, improve the biocompatibility and bind the Ab on the electrode surface. The fabricated immunosensor exhibited lower detection limit (0.003 ng mL^-1, S/N = 3), and wider linear range (0.01-100.0 ng mL^-1), along with the improved reproducibility, selectivity and stability for the assay of PSA. Thus, it is a desirable platform for PSA detection in clinical diagnosis and practical applications.

Highly sensitive detection of hesperidin using AuNPs/rGO modified glassy carbon electrode

The highly sensitive and selective electrochemical sensor of hesperidin based on gold nanoparticles (AuNPs) and reduced graphene oxide (rGO) modified glassy carbon electrode (GCE) is reported.

Simultaneous Detection of Dopamine and Uric Acid Using a Poly(l-lysine)/Graphene Oxide Modified Electrode

A novel, simple and selective electrochemical method was investigated for the simultaneous detection of dopamine (DA) and uric acid (UA) on a poly(l-lysine)/graphene oxide (GO) modified glassy carbon electrode (PLL/GO/GCE) by differential pulse voltammetry (DPV). The electrochemically prepared PLL/GO sensory platform toward the oxidation of UA and DA exhibited several advantages, including high effective surface area, more active sites and enhanced electrochemical activity. Compared to the PLL-modified GCE (PLL/GCE), GO-modified GCE and bare GCE, the PLL/GO/GCE exhibited an increase in the anodic potential difference and a remarkable enhancement in the current responses for both UA and DA. For the simultaneous detection of DA and UA, the detection limits of 0.021 and 0.074 μM were obtained, while 0.031 and 0.018 μM were obtained as the detection limits for the selective detection of UA and DA, using DPV in the linear concentration ranges of 0.5 to 20.0 and 0.5 to 35 μM, respectively. In addition, the PLL/GO/GCE demonstrated good reproducibility, long-term stability, excellent selectivity and negligible interference of ascorbic acid (AA). The proposed modified electrode was successfully implemented in the simultaneous detection of DA and UA in human blood serum, urine and dopamine hydrochloride injection with satisfactory results.

In situ synthesis and analytical investigation of porous Hb–Mn3(PO4)2 hybrid nanosheets and their biosensor applications

An enzyme–inorganic conjugate constructed from slack Hb–Mn₃(PO₄)₂·3H₂O nanosheets was prepared by a simple and effective in situ immobilization method.

Glucose sensing by a glassy carbon electrode modified with glucose oxidase and a magnetic polymeric nanocomposite

Glucose sensing by using of glucose oxidase and a biocompatible poly(p-phenylenediamine)-based nanocomposite.

Enzymatic electrochemical glucose biosensors by mesoporous 1D hydroxyapatite-on-2D reduced graphene oxide

A hydrothermally synthesized mesoporous 1D HAp-on-2D RGO sheets exhibiting direct electrochemistry of glucose biosensing.

Simultaneous determination of uric Acid and xanthine using a poly(methylene blue) and electrochemically reduced graphene oxide composite film modified electrode

Poly(methylene blue) and electrochemically reduced graphene oxide composite film modified electrode (PMB-ERGO/GCE) was successfully fabricated by electropolymerization and was used for simultaneous determination of uric acid (UA) and xanthine (Xa). Based on the excellent electrocatalytic activity of PMB-ERGO/GCE, the electrochemical behaviors of UA and Xa were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). Two anodic sensitive peaks at 0.630 V (versus Ag/AgCl) for UA and 1.006 V (versus Ag/AgCl) for Xa were given by CV in pH 3.0 phosphate buffer. The calibration curves for UA and Xa were obtained in the range of 8.00 × 10(-8)~4.00 × 10(-4) M and 1.00 × 10(-7)~4.00 × 10(-4) M, respectively, by SWV. The detection limits for UA and Xa were 3.00 × 10(-8) M and 5.00 × 10(-8) M, respectively. Finally, the proposed method was applied to simultaneously determine UA and Xa in human urine with good selectivity and high sensitivity.