Glucose determination using amperometric non-enzymatic sensor based on electroactive poly(caffeic acid)@MWCNT decorated with CuO nanoparticles

Smartphone-enabled flow injection amperometric glucose monitoring based on a screen-printed carbon electrode modified with PEDOT@PB and a GOx@PPtNPs@MWCNTs nanocomposite

This study presents a modified screen-printed carbon electrode (SPCE) to determine glucose in a custom-built flow injection system. The biosensor was constructed by immobilizing glucose oxidase on porous platinum nanoparticles decorated on multi-walled carbon nanotubes (GOx@PPtNPs@MWCTNs). The fabrication of the biosensor was completed by coating the GOx@PPtNPs@MWCTNs nanocomposite on an SPCE modified with a nanocomposite of poly(3,4-ethylenedioxythiophene) and Prussian blue (GOx@PPtNPs@MWCTNs/PEDOT@PB/SPCE). The fabricated electrode accurately measured hydrogen peroxide (H2O2), the byproduct of the GOx-catalyzed oxidation of glucose, and was then applied as a glucose biosensor. The glucose response was amperometrically determined from the PB-mediated reduction of H2O2 at an applied potential of -0.10 V in a flow injection system. Under optimal conditions, the developed biosensor produced a linear range from 2.50 μM to 1.250 mM, a limit of detection of 2.50 μM, operational stability over 500 sample injections, and good selectivity. The proposed biosensor determined glucose in human plasma samples, achieving recoveries and results that agreed with the hexokinase-spectrophotometric method (P > 0.05). Combining the proposed biosensor with the custom-built sample feed, a portable potentiostat and a smartphone, enabled on-site glucose monitoring.

Anodized CuO-based reusable non-enzymatic glucose sensor as an alternative method for the analysis of pharmaceutical glucose infusions: a cyclic voltammetric approach

Analyzing pharmaceutical products is a quality control requirement in a production facility. This study presents a CuO electrode-based reusable non-enzymatic sensor as an alternative method for rapid analysis of glucose levels in glucose infusions. CuO is extensively employed as an electrode material in non-enzymatic glucose sensors. Conventionally, these electrodes are fabricated using chemical synthesis of CuO followed by immobilization to the electrode substrate. In contrast, here, Cu metal was mechanically modified to create a grooved surface, followed by electrochemical anodization and subsequent annealing process to grow a seamless CuO layer in situ with enhanced catalytic activity. The morphology of the electrodes was characterized using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The direct electrocatalytic activity of the developed CuO-modified electrode towards glucose oxidation in alkaline media was investigated by cyclic voltammetry in detail. The CuO-modified electrode commenced the oxidation process around 0.10 V vs. Ag pseudo-reference electrode, demonstrating a significant reduction in the overvoltage for glucose oxidation compared to the bare Cu electrode. The sensor is capable of detecting glucose at low oxidation potentials such as 0.2 V with a sensitivity value of 0.37 µA ppm-1, a wide linear range (80-2300 ppm), limit of quantification (LOQ) of 1 ppm, greater repeatability, 1% precision, 3% bias, a short response time (80 s), good reproducibility and excellent reusability (196 consecutive attempts). The enhanced performance and cost-effectiveness make this sensor a promising alternative method for product analysis in glucose injection solutions.

P-incorporated CuO/Cu2S heteronanorods as efficient electrocatalysts for the glucose oxidation reaction toward highly sensitive and selective glucose sensing

Currently, tremendous efforts have been made to explore efficient glucose oxidation electrocatalysts for enzymeless glucose sensors to meet the urgent demands for accurate and fast detection of glucose in the fields of health care and environmental monitoring. In this work, an advanced nanostructured material based on the well-aligned CuO/Cu2S heteronanorods incorporated with P atoms is successfully synthesized on a copper substrate. The as-synthesized material shows high catalytic behavior accompanied by outstanding electrical conductivity. This, combined with the unique morphology of unstacked nanorod arrays, which endow the entire material with a greater number of exposed active sites, make the proposed material act as a highly efficient electrocatalyst for the glucose oxidation reaction. Density functional theory calculations demonstrate that P doping endows P-doped CuO/Cu2S with excellent electrical conductivity and glucose adsorption capability, significantly improving its catalytic performance. As a result, a non-enzymatic glucose sensor fabricated based on our proposed material exhibits a broad linear detection range (0.02-8.2 mM) and a low detection limit (0.95 μM) with a high sensitivity of 2.68 mA mM-1 cm-2 and excellent selectivity.

Optimized Copper-Based Microfeathers for Glucose Detection

Diabetes is expected to rise substantially by 2045, prompting extensive research into accessible glucose electrochemical sensors, especially those based on non-enzymatic materials. In this context, advancing the knowledge of stable metal-based compounds as alternatives to non-enzymatic sensors becomes a scientific challenge. Nonetheless, these materials have encountered difficulties in maintaining stable responses under physiological conditions. This work aims to advance knowledge related to the synthesis and characterization of copper-based electrodes for glucose detection. The microelectrode presented here exhibits a wide linear range and a sensitivity of 1009 µA∙cm-2∙mM-1, overperfoming the results reported in literature so far. This electrode material has also demonstrated outstanding results in terms of reproducibility, repeatability, and stability, thereby meeting ISO 15197:2015 standards. Our study guides future research on next-generation sensors that combine copper with other materials to enhance activity in neutral media.

Nature-Inspired Biomolecular Corona Based on Poly(caffeic acid) as a Low Potential and Time-Stable Glucose Biosensor

Herein, we present a novel biosensor based on nature-inspired poly(caffeic acid) (PCA) grafted to magnetite (Fe3O4) nanoparticles with glucose oxidase (GOx) from Aspergillus niger via adsorption technique. The biomolecular corona was applied to the fabrication of a biosensor system with a screen-printed electrode (SPE). The obtained results indicated the operation of the system at a low potential (0.1 V). Then, amperometric measurements were performed to optimize conditions like various pH and temperatures. The SPE/Fe3O4@PCA-GOx biosensor presented a linear range from 0.05 mM to 25.0 mM, with a sensitivity of 1198.0 μA mM-1 cm-2 and a limit of detection of 5.23 μM, which was compared to other biosensors presented in the literature. The proposed system was selective towards various interferents (maltose, saccharose, fructose, L-cysteine, uric acid, dopamine and ascorbic acid) and shows high recovery in relation to tests on real samples, up to 10 months of work stability. Moreover, the Fe3O4@PCA-GOx biomolecular corona has been characterized using various techniques such as Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Bradford assay.

Carbon nanotubes: a powerful bridge for conductivity and flexibility in electrochemical glucose sensors

The utilization of nanomaterials in the biosensor field has garnered substantial attention in recent years. Initially, the emphasis was on enhancing the sensor current rather than material interactions. However, carbon nanotubes (CNTs) have gained prominence in glucose sensors due to their high aspect ratio, remarkable chemical stability, and notable optical and electronic attributes. The diverse nanostructures and metal surface designs of CNTs, coupled with their exceptional physical and chemical properties, have led to diverse applications in electrochemical glucose sensor research. Substantial progress has been achieved, particularly in constructing flexible interfaces based on CNTs. This review focuses on CNT-based sensor design, manufacturing advancements, material synergy effects, and minimally invasive/noninvasive glucose monitoring devices. The review also discusses the trend toward simultaneous detection of multiple markers in glucose sensors and the pivotal role played by CNTs in this trend. Furthermore, the latest applications of CNTs in electrochemical glucose sensors are explored, accompanied by an overview of the current status, challenges, and future prospects of CNT-based sensors and their potential applications.

In situ embedding of glucose oxidase in amorphous ZIF-7 with high catalytic activity and stability and mechanism investigation

Glucose oxidase (GOx) has a great application potential in the determination of glucose concentration. However, its sensitivity to the environment and poor recyclability limited its broader application. Herein, with the assistance of DA-PEG-DA, a novel immobilized GOx based on amorphous Zn-MOFs (DA-PEG-DA/GOx@aZIF-7/PDA) was developed to impart excellent properties to the enzyme. SEM, TEM, XRD, and BET analyses confirmed that GOx was embedded in amorphous ZIF-7 with ~5 wt% loading. Compared with free GOx, DA-PEG-DA/GOx@aZIF-7/PDA exhibited enhanced stability, excellent reusability, and promising potential for glucose detection. After 10 repetitions, the catalytic activity of DA-PEG-DA/GOx@aZIF-7/PDA can maintain 95.53 % ± 3.16 %. In understanding the in situ embedding of GOx in ZIF-7, the interaction of zinc ion and benzimidazole with GOx was studied by using molecular docking and multi-spectral methods. Results showed that zinc ions and benzimidazole had multiple binding sites on the enzyme, which induced the accelerated synthesis of ZIF-7 around the enzyme. During binding, the structure of the enzyme changes, but such changes hardly affect the activity of the enzyme. This study provides not only a preparation strategy of immobilized enzyme with high activity, high stability, and low enzyme leakage rate for glucose detection, but also a more comprehensive understanding of the formation of immobilized enzymes using the in situ embedding strategy.

Progress on the influence of non-enzymatic electrodes characteristics on the response to glucose detection: a review (2016–2022)

Glucose sensing devices have experienced significant progress in the last years in response to the demand for cost-effective monitoring. Thus, research efforts have been focused on achieving reliable, selective, and sensitive sensors able to monitor the glucose level in different biofluids. The development of enzyme-based devices is challenged by poor stability, time-consuming, and complex purification procedures, facts that have given rise to the synthesis of enzyme-free sensors. Recent advances focus on the use of different components: metal-organic frameworks (MOFs), carbon nanomaterials, or metal oxides. Motivated by this topic, several reviews have been published addressing the sensor materials and synthesis methods, gathering relevant information for the development of new nanostructures. However, the abundant information has not concluded yet in commercial devices and is not useful from an engineering point of view. The dependence of the electrode response on its physico-chemical nature, which would determine the selection and optimization of the materials and synthesis method, remains an open question. Thus, this review aims to critically analyze from an engineering vision the existing information on non-enzymatic glucose electrodes; the analysis is performed linking the response in terms of sensitivity when interferences are present, stability, and response under physiological conditions to the electrode characteristics.

Fluorogenic gemcitabine based light up sensor for serum albumin detection in complex biological matrices

Herein we report fluorogenic derivative of gemcitabine (GEM-DNS), synthesized from gemcitabine hydrochloride and dansyl chloride in a single step. Owing to its large stoke shift of ∼200 nm and intriguing photophysical properties, the said dye has been utilized to estimate albumin concentration in complex bio-media such as human urine and blood serum. High sensitivity and selectivity towards albumin make the aforementioned dye a powerful diagnostic tool to detect ailments such as liver cirrhosis, diabetes, hypertension etc.

Innovative electrochemical electrode modified with Al2O3 nanoparticle decorated MWCNTs for ultra-trace determination of tamsulosin and solifenacin in human plasma and urine samples and their pharmaceutical dosage form

A simple, cheap, sensitive, and time-saving square wave voltammetric (SWV) procedure using a carbon paste electrode modified with aluminum oxide nanoparticle decorated multi-walled carbon nanoparticles (Al2O3-NPs/MWCNTs/CPE) is presented for the ultra-sensitive determination of tamsulosin (TAM) and solifenacin (SOL), one of the most prescribed pharmaceutical combinations in urology. Characterization of the developed electrode was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM) and FT-IR spectrophotometry. The voltammetric behavior of TAM/SOL was evaluated using Al2O3-NPs in different content and electrode compositions. The use of Al2O3 functionalized MWCNTs as a CPE modifier increased the process of electron transfer as well as improved the electrode active surface area therefore, ultra-sensitive results were acquired with a linear range of 10-100 and 12-125 ng ml-1 for TAM and SOL respectively, and a limit of the detection value of 2.69 and 3.25 ng ml-1 for TAM and SOL, respectively. Interestingly, the proposed method succeeded in quantifying TAM and SOL with acceptable percentage recoveries in dosage forms having diverged concentration ranges and in the biological fluids with very low peak plasma concentration (C max). Furthermore, the proposed method was validated, according to the ICH criteria, and shown to be accurate and reproducible.