Portable glucose biosensor based on polynorepinephrine@magnetite nanomaterial integrated with a smartphone analyzer for point-of-care application

Paper-based uric acid assay in whole blood samples by Zn2+ protein precipitation and enzyme-free colorimetric detection

Uric acid (UA) is an important biomarker, as a high concentration in blood can lead to gout and further renal syndrome. Although several point-of-care testing (POCT) devices have been reported to detect UA, there are some limitations such as the requirement for uricase and the complicated pretreatment of serum/plasma samples, which restricts their use at home or in undeveloped areas. In this work, we developed an approach by applying Zn2+ to precipitate proteins and cells in whole blood to avoid interference with the chromogenic reaction. We used carboxymethylcellulose (CMC) to immobilize tetramethylbenzidine (TMB) on a nitrocellulose membrane for colorimetric detection. Using the oxidization properties of H2O2, which turns TMB into oxidized tetramethylbenzidine (TMBox) in the presence of catalyst gold nanoparticles (AuNPs), we successfully constructed an enzyme-free paper-based POCT device using the reduction reaction of UA and TMBox for simple, speedy, and cheap colorimetric detection of UA, achieving a detection time of 8 min, a linear range of 0-150 μg/mL, and an LOD of 25.79 μg/mL. The UA concentration in whole blood samples was further measured and correlated well with the clinical value (R2 = 0.8212). Thus, the proposed assay has the potential for POCT diagnosis, monitoring, and prognosis of diseases related to UA.

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.

Flexible genosensors based on polypyrrole and graphene quantum dots for PML/RARα fusion gene detection: A study of acute promyelocytic leukemia in children

Acute promyelocytic leukemia (APL) in children is associated with a favorable initial prognosis. However, minimal residual disease (MRD) follow-up remains poorly defined, and relapse cases are concerning due to their recurrent nature. Thus, we report two electrochemical flexible genosensors based on polypyrrole (PPy) and graphene quantum dots (GQDs) for label-free PML-RARα oncogene detection. Atomic force microscopy (AFM), scanning electron microscope (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the technological biosensor development. M7 and APLB oligonucleotide sequences were used as bioreceptors to detect oncogenic segments on chromosomes 15 and 17, respectively. AFM characterization revealed heterogeneous topographical surfaces with maximum height peaks for sensor layers when tested with positive patient samples. APLB/Genosensor exhibited a percentage change in anode peak current (ΔI) of 423 %. M7/Genosensor exhibited a ΔI of 61.44 % for more concentrated cDNA samples. The described behavior is associated with the biospecific recognition of the proposed biosensors. Limits of detection (LOD) of 0.214 pM and 0.677 pM were obtained for APLB/Genosensor and M7/Genosensor, respectively. The limits of quantification (LOQ) of 0.648 pM and 2.05 pM were estimated for APLB/Genosensor and M7/Genosensor, respectively. The genosensors showed reproducibility with a relative standard deviation of 7.12 % for APLB and 1.18 % for M7 and high repeatability (9.89 % for APLB and 1.51 % for M7). In addition, genetic tools could identify the PML-RARα oncogene in purified samples, plasmids, and clinical specimens from pediatric patients diagnosed with APL with high bioanalytical performance. Therefore, biosensors represent a valuable alternative for the clinical diagnosis of APL and monitoring of MRD with an impact on public health.

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.

Enzymatic Electrochemical/Fluorescent Nanobiosensor for Detection of Small Chemicals

The detection of small molecules has attracted enormous interest in various fields, including the chemical, biological, and healthcare fields. In order to achieve such detection with high accuracy, up to now, various types of biosensors have been developed. Among those biosensors, enzymatic biosensors have shown excellent sensing performances via their highly specific enzymatic reactions with small chemical molecules. As techniques used to implement the sensing function of such enzymatic biosensors, electrochemical and fluorescence techniques have been mostly used for the detection of small molecules because of their advantages. In addition, through the incorporation of nanotechnologies, the detection property of each technique-based enzymatic nanobiosensors can be improved to measure harmful or important small molecules accurately. This review provides interdisciplinary information related to developing enzymatic nanobiosensors for small molecule detection, such as widely used enzymes, target small molecules, and electrochemical/fluorescence techniques. We expect that this review will provide a broad perspective and well-organized roadmap to develop novel electrochemical and fluorescent enzymatic nanobiosensors.

Advances on microfluidic paper-based electroanalytical devices

Since the inception of the first electrochemical devices on paper substrates, many different reports of microfluidic paper-based electroanalytical devices (μPEDs), innovative hydrophobic barriers and electrode fabrication processes have allowed the incorporation of diverse materials, resulting in different applications and a boost in performance. These advancements have led to the creation of paper-based devices with comparable performance to many standard conventional devices, with the added benefits of pumpless fluidic transport, component separation and reagent storage that can be exploited to automate and handle sample preprocessing. Herein, we review μPEDs, summarize the characteristics and functionalities of μPEDs, such as separation, fluid flow control and storage, and outline the conventional and emerging fabrication and modification approaches for μPEDs. We also examine the recent application of μPEDs in biomedicine, the environment, and food and water safety, as well as some limitations and challenges that must be addressed.

Rationally designed molecularly imprinted polymer membranes as antibody and enzyme mimics in analytical biotechnology

The paper is a self-review of works on development of new approaches to formation of mimics of receptor and catalytic sites of biological macromolecules in the structure of highly cross-linked polymer membranes and thin films. The general strategy for formation of the binding sites in molecularly imprinted polymer (MIP) membranes and thin films was described. A selective recognition of a number of food toxins, endocrine disruptors and metabolites is based on the results of computational modeling data for the prediction and optimization of their structure. A strategy proposed for the design of the artificial binding sites in MIP membranes was supported by the research performed by the authors on development of a number of the MIP membrane-based affinity and catalytic biosensors for selective and sensitive measurement (detection limits 0.3-100 nM) of the target analytes. Novel versatile approaches aimed at improving sensitivity of the developed biosensor systems were discussed.

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.

Development and Practical Application of Glucose Biosensor Based on Dendritic Gold Nanostructures Modified by Conducting Polymers

In this study, graphite rod (GR) electrodes were electrochemically modified by dendritic gold nanostructures (DGNs) followed by immobilization of glucose oxidase (GOx) in the presence of mediator phenazine methosulfate (PMS). Modified with polyaniline (PANI) or polypyrrole (Ppy), GOx/DGNs/GR electrodes were used in glucose biosensor design. Different electrochemical methods were applied for the registration of glucose concentration, and constant potential amperometry (CPA) was chosen as the best one. PANI and Ppy layers synthesized enzymatically on the GOx/DGNs/GR electrodes extended the linear glucose determination range, the width of which depended on the duration of PANI- and Ppy-layers formation. Enzymatically formed polypyrrole was determined as the most suitable polymer for the modification and formation of the glucose biosensor instead of polyaniline, because it was 1.35 times more sensitive and had a 2.57 times lower limit of detection (LOD). The developed glucose biosensor based on the Ppy/GOx/DGNs/GR electrode was characterized by appropriate sensitivity (59.4 μA mM⁻¹ cm⁻²), low LOD (0.070 mmol L⁻¹), wide linear glucose determination range (up to 19.9 mmol L⁻¹), good repeatability (8.01%), and appropriate storage stability (33 days). The performance of the developed glucose biosensor was tested in biological samples and beverages.

Smartphone-Based Electrochemical Systems for Glucose Monitoring in Biofluids: A Review

As a vital biomarker, glucose plays an important role in multiple physiological and pathological processes. Thus, glucose detection has become an important direction in the electrochemical analysis field. In order to realize more convenient, real-time, comfortable and accurate monitoring, smartphone-based portable, wearable and implantable electrochemical glucose monitoring is progressing rapidly. In this review, we firstly introduce technologies integrated in smartphones and the advantages of these technologies in electrochemical glucose detection. Subsequently, this overview illustrates the advances of smartphone-based portable, wearable and implantable electrochemical glucose monitoring systems in diverse biofluids over the last ten years (2012-2022). Specifically, some interesting and innovative technologies are highlighted. In the last section, after discussing the challenges in this field, we offer some future directions, such as application of advanced nanomaterials, novel power sources, simultaneous detection of multiple markers and a closed-loop system.

Effect of Electrode Modification with Chitosan and Nafion® on the Efficiency of Real-Time Enzyme Glucose Biosensors Based on ZnO Tetrapods

Noninvasive, continuous glucose detection can provide some insights into daily fluctuations in blood glucose levels, which can help us balance diet, exercise, and medication. Since current commercially available glucose sensors can barely provide real-time glucose monitoring and usually imply different invasive sampling, there is an extraordinary need to develop new harmless methods for detecting glucose in non-invasive body fluids. Therefore, it is crucial to design (bio)sensors that can detect very low levels of glucose (down to tens of µM) normally found in sweat or tears. Apart from the selection of materials with high catalytic activity for glucose oxidation, it is also important to pay considerable attention to the electrode functionalization process, as it significantly contributes to the overall detection efficiency. In this study, the (ZnO tetrapods) ZnO TPs-based electrodes were functionalized with Nafion and chitosan polymers to compare their glucose detection efficiency. Cyclic voltammetry (CV) measurements have shown that chitosan-modified ZnO TPs require a lower applied potential for glucose oxidation, which may be due to the larger size of chitosan micelles (compared to Nafion micelles), and thus easier penetration of glucose through the chitosan membrane. However, despite this, both ZnO TPs modified with chitosan and Nafion membranes, provided quite similar glucose detection parameters (sensitivities, 7.5 µA mM⁻¹ cm⁻¹ and 19.2 µA mM⁻¹ cm⁻¹, and limits of detection, 24.4 µM and 22.2 µM, respectively). Our results show that both electrodes have a high potential for accurate real-time sweat/tears glucose detection.

Hybrid Nanobioengineered Nanomaterial-Based Electrochemical Biosensors

Nanoengineering biosensors have become more precise and sophisticated, raising the demand for highly sensitive architectures to monitor target analytes at extremely low concentrations often required, for example, for biomedical applications. We review recent advances in functional nanomaterials, mainly based on novel organic-inorganic hybrids with enhanced electro-physicochemical properties toward fulfilling this need. In this context, this review classifies some recently engineered organic-inorganic metallic-, silicon-, carbonaceous-, and polymeric-nanomaterials and describes their structural properties and features when incorporated into biosensing systems. It further shows the latest advances in ultrasensitive electrochemical biosensors engineered from such innovative nanomaterials highlighting their advantages concerning the concomitant constituents acting alone, fulfilling the gap from other reviews in the literature. Finally, it mentioned the limitations and opportunities of hybrid nanomaterials from the point of view of current nanotechnology and future considerations for advancing their use in enhanced electrochemical platforms.

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

A novel non-enzymatic glucose sensor based on poly(caffeic acid)@multi-walled carbon nanotubes decorated with CuO nanoparticles (PCA@MWCNT-CuO) was developed. The described approach involves the complexation/accumulation of Cu(II) on PCA@MWCNT followed by electrochemical CuO deposition in an alkaline electrolyte. The morphology and surface characteristics of the nanomaterial were determined by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), Raman spectroscopy, and inductively coupled plasma mass spectrometry (ICP-MS). A hybrid-support sensor device was then developed to assess the glucose concentration in different solutions. The sensitivity of the electrode is 2412 μA mM^-1 cm^-2. The electrode exhibited a broad linear range of 2 µM to 9 mM and a low limit of detection (LOD) of 0.43 µM (relative standard deviation, RSD = 2.3%) at + 0.45 V vs Ag/AgCl. The excellent properties obtained for glucose detection were most likely due to the synergistic effect of the combination of individual components: poly(caffeic acid), MWCNTs, and CuO. Good accuracy and high precision were demonstrated for quantifying glucose concentrations in human serum and blood samples (the recovery ranged from 95.0 to 99.5%). The GC/PCA@MWCNT-CuO sensor represents a novel, simple, and low-cost approach to the fabrication of devices for amperometric sensing of glucose.