Disposable urea biosensor based on nanoporous ZnO film fabricated from omissible polymeric substrate

Potential of Zinc Oxide Nanostructures in Biosensor Application

The burgeoning field of biosensors has seen significant advancements with the induction of zinc oxide (ZnO) nanostructures, because of their unique structural, electrical, and optical properties. ZnO nanostructures provide numerous benefits for biosensor applications. Their superior electron mobility enables effective electron transfer between the bioreceptor and transducer, enhancing sensitivity and reducing detection limits. Furthermore, ZnO's biocompatibility and non-toxicity make it ideal for in vivo applications, reducing the chances of adverse biological responses. This review paper explores the prospects of ZnO nanostructures in the development of biosensors, focusing on their morphological and structural characteristics. Various synthesis techniques, that include sol-gel, sputtering, and chemical vapor deposition, were successfully employed to prepare different ZnO nanostructures, like nanorods, nanotubes, and nanowires. The various findings in this field underscore the efficacy of ZnO nanostructures in enhancing the specificity and sensitivity of biosensors, presenting a promising avenue for the advancement of point-of-care diagnostic devices.

Watermelon Derived Urease Immobilized Gold Nanoparticles-Graphene Oxide Transducer for Direct Detection of Urea in Milk Samples

Urea contamination in milk poses significant health risks, including kidney failure, urinary tract obstruction, fluid loss, shock, and gastrointestinal bleeding. This highlights the need for sensitive, rapid, and reliable methods to detect traces amount of urea in milk. In this study, we designed an electrochemical transducer for urea detection by utilizing purified watermelon urease (Urs), gold nanoparticles (AuNPs), and graphene oxide (GO). The nanomaterials and biosensor probe were characterized using UV-vis spectroscopy, XPS, TEM, XRD, FTIR, AFM, CV, EIS, and DPV. The engineered probe (GCE/AuNPs/GO/Urs) demonstrated a broad linear detection range of 5 to 90 mg/dL and a low limit of detection (LOD) of 0.037 (±0.012) mg/dL (RSD < 3.7%). The biosensor was tested for potential interferents that may be present in adulterated milk and an exceptionally low coefficient of selectivity (ksel <0.1) was obtained. Evaluation of milk samples from a local dairy farm showed good recovery rates from 93.13% to. 98.79% (RSD < 4.28%, n = 3), indicating reliable detection capabilities. Stability tests confirmed the sensor's reproducibility and consistent performance. Additionally, a comparison study of the system was carried out using the purified watermelon urease and the commercially available urease. Herein, the results obtained using the sensor probe was finally validated with the gold standard method.

Nanostructured Metal Oxide-Based Electrochemical Biosensors in Medical Diagnosis

Nanostructured metal oxides (NMOs) provide electrical properties such as high surface-to-volume ratio, reaction activity, and good adsorption strength. Furthermore, they serve as a conductive substrate for the immobilization of biomolecules, exhibiting notable biological activity. Capitalizing on these characteristics, they find utility in the development of various electrochemical biosensing devices, elevating the sensitivity and selectivity of such diagnostic platforms. In this review, different types of NMOs, including zinc oxide (ZnO), titanium dioxide (TiO2), iron (II, III) oxide (Fe3O4), nickel oxide (NiO), and copper oxide (CuO); their synthesis methods; and how they can be integrated into biosensors used for medical diagnosis are examined. It also includes a detailed table for the last 10 years covering the morphologies, analysis techniques, analytes, and analytical performances of electrochemical biosensors developed for medical diagnosis.

Recent advancements in urea biosensors for biomedical applications

The quick progress in health care technology as a recurrent measurement of biochemical factors such as blood components leads to advance development and growth in biosensor technology necessary for effectual patient concern. The review wok of authors present a concise information and brief discussion on the development made in the progress of potentiometric, field effect transistor, graphene, electrochemical, optical, polymeric, nanoparticles and nanocomposites based urea biosensors in the past two decades. The work of authors is also centred on different procedures/methods for detection of urea by using amperometric, potentiometric, conductometric and optical processes, where graphene, polymer etc. are utilised as an immobilised material for the fabrication of biosensors. Further, a comparative revision has been accomplished on various procedures of urea analysis using different materials-based biosensors, and it discloses that electrochemical and potentiometric biosensor is the most promise one among all, in terms of rapid response time, extensive shelf life and resourceful design.

Dimensionally Stable Anode Based Sensor for Urea Determination via Linear Sweep Voltammetry

Urea is an added value chemical with wide applications in the industry and agriculture. The release of urea waste to the environment affects ecosystem health despite its low toxicity. Online monitoring of urea for industrial applications and environmental health is an unaddressed challenge. Electroanalytical techniques can be a smart integrated solution for online monitoring if sensors can overcome the major barrier associated with long-term stability. Mixed metal oxides have shown excellent stability in environmental conditions with long lasting operational lives. However, these materials have been barely explored for sensing applications. This work presents a proof of concept that demonstrates the applicability of an indirect electroanalytical quantification method of urea. The use of Ti/RuO₂-TiO₂-SnO₂ dimensional stable anode (DSA^®) can provide accurate and sensitive quantification of urea in aqueous samples exploiting the excellent catalytic properties of DSA^® on the electrogeneration of active chlorine species. The cathodic reduction of accumulated HClO/ClO⁻ from anodic electrogeneration presented a direct relationship with urea concentration. This novel method can allow urea quantification with a competitive LOD of 1.83 × 10⁻⁶ mol L⁻¹ within a linear range of 6.66 × 10⁻⁶ to 3.33 × 10⁻⁴ mol L⁻¹ of urea concentration.

Urea biosensors: A comprehensive review

Present study is specially designed for the recent advances in biosensors to detect and quantify urea concentration. Urea (carbamide) is an organic compound made up of the carbonyl (C=O) functional group with two -NH₂ groups having chemical formula CO (NH₂ )₂ . In nature, urea is found everywhere as the result of various processes, and in the human body, urea is an end product of nitrogen metabolism. An excessive concentration of urea in the human body is responsible for different critical diseases such as indigestion, acidity, ulcers, cancer, malfunctioning of kidneys, renal failure, urinary tract obstruction, dehydration, shock, burns, gastrointestinal bleeding, and so on. Moreover, below the normal level may cause hepatic failure, nephritic syndrome, cachexia, and so on. As well as in various fields such as fishery, dairy, food preservation, agriculture, and so on, urea is normally found and its detection is necessary. In urea biosensors, enzyme urease (Urs) is used as a bioreceptor element and retains its long last activity is the critical issue in front of the researcher. During recent decades, different nanoparticles (zinc oxide, nickel oxide, iron oxide, titanium dioxide, tin(IV) oxide, etc.), conducting polymer (polyaniline, polypyrrole, etc.), conducting polymer-nanoparticles composites, carbon materials (carbon nanotubes, graphene oxide, reduced graphene oxide graphene), and so on are used in urea biosensors. The main emphasis of the present study is to provide cumulative and comprehensive information about the sensing parameters of urea biosensors based on the materials used for enzyme immobilization. Besides this special task, this review provides a fruitful discussion on the basics of biosensors briefly for new and upcoming researchers. Thus, the present study may act as a gift for a large audience that come from different fields and are working in biosensors research.

A DNA Based Biosensor Amplified With ZIF-8/Ionic Liquid Composite for Determination of Mitoxantrone Anticancer Drug: An Experimental/Docking Investigation

An ultrasensitive DNA electrochemical biosensor based on the carbon paste electrode (CPE) amplified with ZIF-8 and 1-butyl-3-methylimidazolium methanesulfonate (BMIMS) was fabricated in this research. The DNA/BMIMS/ZIF-8/CPE was used for the selective determination of a mitoxantrone anticancer drug in aqueous solution, resulting in a good catalytic effect and a powerful ability for determining mitoxantrone. Also, the interaction of the mitoxantrone anticancer drug with guanine bases of ds-DNA was used as a powerful strategy in the suggested biosensor, which was confirmed with docking investigation. Docking study of mitoxantrone into the ds-DNA sequence showed the intercalative binding mode of mitoxantrone into the nitrogenous-based pairs of ds-DNA. The effective factors such as ds-DNA concentration, temperature, buffer types, and incubation time were also optimized for the fabricated mitoxantrone biosensor. The results showed that, under optimum conditions (T = 25°C; incubation time=12 min; pH= 4.8 acetate buffer solution and [DNA] = 50 mg/L), the DNA/BMIMS/ZIF-8/CPE could be used in mitoxantrone assay in a concentration ranging from 8.0 nM to 110 μM with a detection limit of 3.0 nM. In addition, recovery data between 99.18 and 102.08% were obtained for the determination of mitoxantrone in the injection samples using DNA/ZIF-8/BMIMF/CPE as powerful biosensors.

Advancements in Microfabricated Gas Sensors and Microanalytical Tools for the Sensitive and Selective Detection of Odors

In recent years, advancements in micromachining techniques and nanomaterials have enabled the fabrication of highly sensitive devices for the detection of odorous species. Recent efforts done in the miniaturization of gas sensors have contributed to obtain increasingly compact and portable devices. Besides, the implementation of new nanomaterials in the active layer of these devices is helping to optimize their performance and increase their sensitivity close to humans' olfactory system. Nonetheless, a common concern of general-purpose gas sensors is their lack of selectivity towards multiple analytes. In recent years, advancements in microfabrication techniques and microfluidics have contributed to create new microanalytical tools, which represent a very good alternative to conventional analytical devices and sensor-array systems for the selective detection of odors. Hence, this paper presents a general overview of the recent advancements in microfabricated gas sensors and microanalytical devices for the sensitive and selective detection of volatile organic compounds (VOCs). The working principle of these devices, design requirements, implementation techniques, and the key parameters to optimize their performance are evaluated in this paper. The authors of this work intend to show the potential of combining both solutions in the creation of highly compact, low-cost, and easy-to-deploy platforms for odor monitoring.

Comparing glucose and urea enzymatic electrochemical and optical biosensors based on polyaniline thin films

Analytical sensors that can detect chemical (including biological) analytes are becoming increasingly widespread within the field of analytical chemistry. More than this, in a world tending towards the 'internet-of-things', the miniaturization of such devices is becoming increasingly urgent. Accordingly, electrochemical methods that are simultaneously multiplexable and effective at a miniature scale are receiving much attention. In the present work, we compare the label-free electrochemical response of enzymatic biosensors with the response of their optical counterpart. As a proof-of-concept we compare the electrochemical impedimetric response and the first time described capacitive response of enzymatic biosensors to their optical reflectance response (measured in the visible region using a portable handset spectrophotometer). The target was the detection of glucose and urea. The chemical platform of the sensors was composed of enzymatically functionalized polyaniline thin films. Sensitivity, linearity, and the limit of detection were analyzed for both electrochemical and optical instrumental settings. We found that the impedimetric/capacitive electrochemical setup produced a response that was of a similar quality to the optical response (sensitivities of 10.7 ± 0.7, 7.4 ± 0.7 and 4.3 ± 0.2% per decade for impedimetric, capacitive and optical glucose biosensors, respectively) with a broader linear range (10^-4 to 10^-1 mol L^-1 for both glucose and urea biosensors) and similar limit-of-detection in the range of 1 μmol L^-1 within a relevant and practical diagnosis range for biomedical applications.

Evaluation of Pt,Pd-Doped, NiO-Decorated, Single-Wall Carbon Nanotube-Ionic Liquid Carbon Paste Chemically Modified Electrode: An Ultrasensitive Anticancer Drug Sensor for the Determination of Daunorubicin in the Presence of Tamoxifen

Measuring the concentration of anticancer drugs in pharmacological and biological samples is a very useful solution to investigate the effectiveness of these drugs in the chemotherapy process. A Pt,Pd-doped, NiO-decorated SWCNTs (Pt,Pd-NiO/SWCNTs) nanocomposite was synthesized using a one-pot procedure and combining chemical precipitation and ultrasonic sonochemical methods and subsequently characterized by TEM and EDS analysis methods. The analyses results showed the high purity and good distribution of elements and the ~10-nm diameter of the Pt,Pd-NiO nanoparticle decorated on the surface of the SWCNTs with a diameter of about 20-30 nm. Using a combination of Pt,Pd-NiO/SWCNTs and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (1B23DTFB) in a carbon paste (CP) matrix, Pt,Pd-NiO/SWCNTs/1B23DTFB/CP was fabricated as a highly sensitive analytical tool for the electrochemical determination of daunorubicin in the concentration range of 0.008-350 μM with a detection limit of 3.0 nM. Compared to unmodified CP electrodes, the electro-oxidation process of daunorubicin has undergone significant improvements in current (about 9.8 times increasing in current) and potential (about 110 mV) decreasing in potential). It is noteworthy that the designed sensor can well measure daunorubicin in the presence of tamoxifen (two breast anticancer drugs with a ΔE = 315 mV. According to the real sample analysis data, the Pt,Pd-NiO/SWCNTs/1B23DTFB/CP has proved to be a promising methodology for the analysis and measuring of daunorubicin and tamoxifen in real (e.g., pharmaceutical) samples.

Glucose Oxidase/Nano-ZnO/Thin Film Deposit FTO as an Innovative Clinical Transducer: A Sensitive Glucose Biosensor

In the present research, a new biocompatible electrode is proposed as a rapid and direct glucose biosensing technique that improves on the deficiencies of fast clinical devices in laboratory investigations. Nano-ZnO (nanostructured zinc oxide) was sputtered by reactive direct current magnetron sputtering system on a precovered fluorinated tin oxide (FTO) conductive layer. Spin-coated polyvinyl alcohol (PVA) at optimized instrumental deposition conditions was applied to prepare the effective medium for glucose oxidase enzyme (GOx) covalent immobilization through cyanuric chloride (GOx/nano-ZnO/PVA/FTO). The electrochemical behavior of glucose on the fabricated GOx/nano-ZnO/PVA/FTO biosensor was investigated by I-V techniques. In addition, field emission scanning electron microscopy and electrochemical impedance spectroscopy were applied to assess the morphology of the modified electrode surface. The I-V results indicated good sensitivity for glucose detection (0.041 mA per mM) within 0.2-20 mM and the limit of detection was 2.0 μM. We believe that such biodevices have good potential for tracing a number of biocompounds in biological fluids along with excellent accuracy, selectivity, and precise analysis. The fast response time of the fabricated GOx/nano-ZnO/PVA/FTO biosensor (less than 3 s) could allow most types of real-time analysis.

A simple sonochemical approach to fabricate a urea biosensor based on zinc phthalocyanine/graphene oxide/urease bioelectrode

A novel zinc phthalocyanine/graphene oxide (ZnPh/GO) nanocomposite modified glassy carbon electrode (GCE) was prepared by using sonochemical approach and simple drop casting method. Urease (Urs) was used as the specific enzyme for urea detection and was physically immobilized onto the surface of ZnPh/GO nanocomposite. The fabricated ZnPh/GO/Urs matrix was successfully characterized by UV-vis-spectroscopy, FT-IR spectroscopy, scanning electron microscopy (SEM), raman spectrum, thermogravimetric analysis, cyclic voltammetric (CV) and amperometric techniques. The electrocatalytic performance of the ZnPh/GO/Urs electrode was investigated by urea biosensor. Our results demonstrate that the modified electrode has excellent electrocatalytic activity towards the sensing of urea in 0.1 M phosphate buffer solution (PBS, pH 7.2). The biosensor tolerated a wide linear concentration range for urea from 0.4 to 22 μM (R² = 0.991), with a detection limit of 0.034 µM (S/N = 3). The ZnPh/GO/Urs bioectrode has several excellent properties, including a fast response time, high reproducibility and stability.