A Nanotechnology-Based Approach to Biosensor Application in Current Diabetes Management Practices

Diabetes mellitus is linked to both short-term and long-term health problems. Therefore, its detection at a very basic stage is of utmost importance. Research institutes and medical organizations are increasingly using cost-effective biosensors to monitor human biological processes and provide precise health diagnoses. Biosensors aid in accurate diabetes diagnosis and monitoring for efficient treatment and management. Recent attention to nanotechnology in the fast-evolving area of biosensing has facilitated the advancement of new sensors and sensing processes and improved the performance and sensitivity of current biosensors. Nanotechnology biosensors detect disease and track therapy response. Clinically efficient biosensors are user-friendly, efficient, cheap, and scalable in nanomaterial-based production processes and thus can transform diabetes outcomes. This article is more focused on biosensors and their substantial medical applications. The highlights of the article consist of the different types of biosensing units, the role of biosensors in diabetes, the evolution of glucose sensors, and printed biosensors and biosensing systems. Later on, we were engrossed in the glucose sensors based on biofluids, employing minimally invasive, invasive, and noninvasive technologies to find out the impact of nanotechnology on the biosensors to produce a novel device as a nano-biosensor. In this approach, this article documents major advances in nanotechnology-based biosensors for medical applications, as well as the hurdles they must overcome in clinical practice.

New Miniaturized Disposable Screen-Printed Microchip Integrated with Molecularly Imprinted Polymer for Metronidazole Benzoate Drug Detection

A novel potentiometric microelectrode incorporating a molecularly imprinted polymer (MIP) was fabricated, characterized, and successfully applied to the recognition and quantification of the drug, metronidazole benzoate. The elaborated MIP-based sensor was realized by thermal polarization, using metronidazole benzoate as the template material, 1-vinyl-2-pyrrolidine (VP) as a functional monomer, and ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent in the presence of benzoyl peroxide as the initiator. The MIP-based sensor exhibited a super-Nernstian response (61.5 ± 0.5, mV/decade) covering the linear concentration range of 1 × 10^-8-1 × 10^-3 mole L^-1 of metronidazole benzoate with a fast response time (≤10, s.) and detection limit of 7 × 10^-9 mole L^-1. The microchip showed high selectivity toward the template drug molecule in the presence of many investigated interfering species. The chip electrode was successfully used in the quantification of metronidazole benzoate in some real biological samples with high accuracy (recovery, 95.4%) and precision (RSD, 1.5). Moreover, the merits offered by the elaborated MIP-based MB microchip assembly include small size, miniaturization, integration, and consequently, automation feasibility.

Chitosan-based enzyme ink for screen-printed bioanodes

In this study, magnesium oxide (MgO)-templated mesoporous carbon (MgOC) and chitosan cross-linked with genipin (chitosan-genipin) were considered bio-composite inks for screen-printed bioanodes. The fabrication processes were optimized using rheological and structural data, and a bioanode ink containing glucose oxidase (GOx) and 1,2-naphthoquinone (1,2-NQ) was successfully developed. The optimal bioanode-ink contained MgOC pre-treated by washing to achieve a hydrophilic and neutral surface, which helped maintain enzyme activity and resulted in a highly porous electrode structure, which is essential for the accessibility of glucose to GOx. A bioanode fabricated using this ink showed a linear response current dependency up to 8 mM glucose with a sensitivity of 25.83 μA cm-2 mM-1. Combined with a conventional biocathode, an electromotive force of 0.54 V and a maximal power density of 96 μW cm-2 were achieved. These results show that this bio-composite ink can be used to replace the multi-step process of printing with conventional ink followed by drop-casting enzyme and mediator with a one-step printing process.

Precise and rapid solvent-assisted geometric protein self-patterning with submicron spatial resolution for scalable fabrication of microelectronic biosensors

Precise and high-resolution coupling of functional proteins with micro-transducers is critical for the manufacture of miniaturized bioelectronic devices. Moreover, electrochemistry on microelectrodes has had a major impact on electrochemical analysis and sensor technologies, since the small size of microelectrode affects the radial diffusion flux of the analyte to deliver enhanced mass transport and electrode kinetics. However, a large technology gap has existed between the process technology associated with such microelectronics and the conventional bio-conjugation techniques that are generally used. Here, we report on a high-resolution and rapid geometric protein self-patterning (GPS) method using solvent-assisted protein-micelle adsorption printing to couple biomolecules onto microelectrodes with a minimum feature size of 5 μm and a printing time of about a minute. The GPS method is versatile for micropatterning various biomolecules including enzymes, antibodies and avidin-biotinylated proteins, delivering good geometric alignment and preserving biological functionality. We further demonstrated that enzyme-coupled microelectrodes for glucose detection exhibited good electrochemical performance which benefited from the GPS method to maximize effective signal transduction at the bio-interface. These microelectrode arrays maintained fast convergent analyte diffusion displaying typical steady-state I-V characteristics, fast response times, good linear sensitivity (0.103 nA mm^-2 mM^-1, R² = 0.995) and an ultra-wide linear dynamic range (2-100 mM). Our findings provide a new technical solution for the precise and accurate coupling of biomolecules to a microelectronic array with important implications for the scaleup and manufacture of diagnostics, biofuel cells and bioelectronic devices that could not be realized economically by other existing techniques.

Development of glucose oxidase-chitosan immobilized paper biosensor using screen-printed electrode for amperometric detection of Cr(VI) in water

Hexavalent chromium is a toxic heavy metal getting discharged into the environment and water bodies through various industrial processes. Conventional analysis methods call for expensive equipment and complicated sample pretreatment that made unsuitable for onsite detection. Paper is used as an enzyme immobilization platform because of its property to wick the liquid by capillary action; lightweight, cheap and can be easily patterned or cut according to the requirements for developing biosensor. In this study, enzyme immobilization of glucose oxidase (GOx) on filter paper were examined using three polysaccharides such as chitosan, sodium alginate and dextran for entrapment efficiency, activity and stability of the immobilized enzyme. Among the three, chitosan proved efficient for enzyme entrapment with about 90% efficiency at 0.3% (w/v) chitosan. The stability was checked after 1 week at 4 °C and room temperature, where the chitosan entrapped enzyme retained nearly 97% stability at 4 °C. Enzyme inhibition study of GOx and Cr(VI) was carried out using chronoamperometry shown uncompetitive type of inhibition. A paper-based electrochemical biosensor strip was developed by immobilizing GOx enzyme on filter paper using chitosan as an entrapping agent and associating it with a screen-printed carbon electrode for amperometric measurements. The linear range of detection was obtained as 0.05-1 ppm with the limit of detection as 0.05 ppm for Cr(VI), which is the standard permissible limit in potable water. The relative standard deviation (5.6%) indicates good reproducibility of the fabricated biosensor.

Phthalocyanine Modified Electrodes in Electrochemical Analysis

Phthalocyanines are aromatic or macrocyclic organic compounds and attract great attention due to their numerous properties. They have many high-tech applications in different areas of the industry such as dyestuffs, thermal printing screens, photovoltaic solar cells, membrane catalytic reactors, semiconductor materials and gas sensors. In the last decade, electrochemical sensor studies have accelerated with the catalytic lighting. It plays a dominant role in the development and implementation of new generation sensors. The aim of this study is to review the electrochemical methods based on electrode modification with phthalocyanines and to shed light on new application areas of phthalocyanines. The focal point was based on the sensor applications of phthalocyanines in the determination of drugs, pesticides, organic materials and metals etc. by electrochemical methods. Experimental conditions and some validation parameters of the sensor applications such as metal phthalocyanine types, indicator electrodes, selectivity, working ranges, detection limits, and analytical applications were discussed. Consequently, this is the first review dealing with the applications of phthalocyanines in electrochemical sensors for the sensitive determination of analytes in a variety of matrices.

Reusable, Non-Invasive, and Ultrafast Radio Frequency Biosensor Based on Optimized Integrated Passive Device Fabrication Process for Quantitative Detection of Glucose Levels

The increase in the number of people suffering diabetes has been the driving force behind the development of glucose sensors to overcome the current testing shortcomings. In this work, a reusable, non-invasive and ultrafast radio frequency biosensor based on optimized integrated passive device fabrication process for quantitative detection of glucose level was developed. With the aid of the novel biosensor design with hammer-shaped capacitors for carrying out detection, both the resonance frequency and magnitude of reflection coefficient can be applied to map the different glucose levels. Meanwhile, the corresponding fabrication process was developed, providing an approach for achieving quantitative detection and a structure without metal-insulator-metal type capacitor that realizes low cost and high reliability. To enhance the sensitivity of biosensor, a 3-min dry etching treatment based on chlorine/argon-based plasma was implemented for realizing hydrophilicity of capacitor surface to ensure that the biosensor can be touched rapidly with glucose. Based on above implementation, a non-invasive biosensor having an ultrafast response time of superior to 0.85 s, ultralow LOD of 8.01 mg/dL and excellent reusability verified through five sets of measurements are realized. The proposed approaches are not limited the development of a stable and accurate platform for the detection of glucose levels but also presents a scheme toward the detection of glucose levels in human serum.

Paper-based electrodes modified with cobalt phthalocyanine colloid for the determination of hydrogen peroxide and glucose

Cobalt(ii) phthalocyanine (CoPc) was suspended in aqueous medium and the colloidal system was used as catalyst for the electrochemical determination of hydrogen peroxide on paper-based electrodes modified with carbon nanomaterials.

Impact of nano-morphology, lattice defects and conductivity on the performance of graphene based electrochemical biosensors

Diverse properties of graphenic materials have been extensively explored to determine properties that make good electrochemical nanomaterial-based biosensors. These are reviewed by critically examining the influence of graphene nano-morphology, lattice defects and conductivity. Stability, reproducibility and fabrication are discussed together with sensitivity and selectivity. We provide an outlook on future directions for building efficient electrochemical biosensors.

Band Electrodes in Sensing Applications: Response Characteristics and Band Fabrication Methods

This Review surveys the fabrication methods reported for both single microband electrodes and microband electrode arrays and their uses in sensing applications. A theoretical section on band electrodes provides background information on the structure of band electrodes, their diffusional profiles, and the types of voltammetric behavior observed. A short section summarizes the currently available commercial microband electrodes. A section describing recent (10 years) sensing applications using band electrode is also presented.

Support-Material-Free Microfluidics on an Electrochemical Sensors Platform by Aerosol Jet Printing

Printed electronics have led to new possibilities in the detection and quantification of a wide range of molecules important for medical, biotechnological, and environmental fields. The integration with microfluidics is often adopted to avoid hand-deposition of little volumes of reagents and samples on miniaturized electrodes that strongly depend on operator's skills. Here we report design, fabrication and test of an easy-to-use electrochemical sensor platform with microfluidics entirely realized with Aerosol Jet Printing (AJP). We printed a six-electrochemical-sensors platform with AJP and we explored the possibility to aerosol jet print directly on it a microfluidic structure without any support material. Thus, the sacrificial material removal and/or the assembly with sensors steps are avoided. The repeatability observed when printing both conductive and ultraviolet (UV)-curable polymer inks can be supported from the values of relative standard deviation of maximum 5% for thickness and 9% for line width. We designed the whole microfluidic platform to make the sample deposition (20 μL) independent from the operator. To validate the platform, we quantified glucose at different concentrations using a standard enzyme-mediated procedure. Both mediator and enzyme were directly aerosol jet printed on working electrodes (WEs), thus the proposed platform is entirely fabricated by AJP and ready to use. The chronoamperometric tests show limit of detection (LOD) = 2.4 mM and sensitivity = 2.2 ± 0.08 µA/mM confirming the effectiveness of mediator and enzyme directly aerosol jet printed to provide sensing in a clinically relevant range (3-10 mM). The average relative standard inter-platform deviation is about 8%. AJP technique can be used for fabricating a ready-to-use microfluidic device that does not need further processing after fabrication, but is promptly available for electrochemical sample analysis.

Non-Enzymatic Impedimetric Sensor Based on 3-Aminophenylboronic Acid Functionalized Screen-Printed Carbon Electrode for Highly Sensitive Glucose Detection

A highly sensitive glucose sensor was prepared by a one-step method using 3-aminophenyl boronic acid as a unit of recognition and a screen-printed carbon electrode (SPCE) as an electrochemical transducer. Scanning Electron Microscopy confirmed the success of the functionalization of the SPCE due to the presence of clusters of boronic acid distributed on the carbon surface. In agreement with the Electrochemical Impedance Spectroscopy (EIS) tests performed before and after the functionalization, Cyclic Voltammetry results indicated that the electroactivity of the electrode decreased 37.9% owing to the presence of the poly phenylboronic acid on the electrode surface. EIS revealed that the sensor was capable to selectively detect glucose at a broad range of concentrations (limit of detection of 8.53 × 10-9 M), not recognizing fructose and sucrose. The device presented a stable impedimetric response when immediately prepared but suffered the influence of the storage time and some interfering species (dopamine, NaCl and animal serum). The response time at optimized conditions was estimated to be equal to 4.0 ± 0.6 s.

Novel grafted electrochemical interface for covalent glucose oxidase immobilization using reactive pentafluorophenyl methacrylate

One of the most important factors for the proper functioning of enzymatic electrochemical biosensors is the enzyme immobilization strategy. In this work, glucose oxidase was covalently immobilized using pentafluorophenyl methacrylate (PFM) by applying two different surface modification techniques (plasma polymerization and plasma-grafting). The grafted surface was specifically designed to covalently anchor enzyme molecules. It was observed using QCM-D measurements the PFM plasma-grafted surfaces were able to retain a higher number of active enzyme molecules than the PFM polymerized surfaces. An amperometric glucose biosensor using titanium dioxide nanotubes array (TiO₂NTAs) modified by PFM plasma-grafted surface was prepared. The resulting biosensor exhibited a fast response and short analysis time (approximately eight minutes per sample). Moreover, this biosensor achieved high sensitivity (9.76 μA mM^-1) with a linear range from 0.25 to 1.49 mM and a limit of detection (LOD) equal to 0.10 mM of glucose. In addition, the glucose content of 16 different food samples was successfully measured using the developed biosensor. The obtained results were compared with the respective HPLC value and a deviation smaller than 10% was obtained in all the cases. Therefore, the biosensor was able to overcome all possible interferences in the selected samples/matrices.