A novel amperometric biosensor based on ZnO:Co nanoclusters for biosensing glucose

Electronic Tongue Based on ZnO/ITO@glass for Electrochemical Monitoring of Spiciness Levels

Capsaicin, a chemical compound present in chili peppers, is widely acknowledged as the main contributor to the spicy and hot sensations encountered during consumption. Elevated levels of capsaicin can result in meals being excessively spicy, potentially leading to health issues, such as skin burning, irritation, increased heart rate and circulation, and discomfort in the gastrointestinal system and even inducing nausea or diarrhea. The level of spiciness that individuals can tolerate may vary, so what may be considered incredibly hot for one person could be mild for another. To ensure food safety, human healthcare, regulatory compliance, and quality control in spicy food products, capsaicin levels must be measured. For these purposes, a reliable and stable sensor is required to quantify the capsaicin level. To leverage the effect of zinc oxide (ZnO), herein, we demonstrated the one-step fabrication process of an electronic tongue (E-Tongue) based on an electrochemical biosensor for the determination of capsaicin. ZnO was electrodeposited on the indium tin oxide (ITO) surface. The biosensor demonstrated the two notable linear ranges from 0.01 to 50 μM and from 50 to 500 μM with a limit of detection (LOD) of 2.1 nM. The present study also included the analysis of real samples, such as green chilis, red chili powder, and dried red chilis, to evaluate their spiciness levels. Furthermore, the E-Tongue exhibited notable degrees of sensitivity, selectivity, and long-term stability for a duration of more than a month. The development of an E-Tongue for capsaicin real-time monitoring as a point-of-care (POC) device has the potential to impact various industries and improve safety, product quality, and healthcare outcomes.

Ag-Decorated Vertically Aligned ZnO Nanorods for Non-Enzymatic Glucose Sensor Applications

The non-enzymatic glucose sensing response of pure and Ag-decorated vertically aligned ZnO nanorods grown on Si substrates was investigated. The simple low-temperature hydrothermal method was employed to synthesize the ZnO NRs on the Si substrates, and then Ag decoration was achieved by sputtering. The crystal structure and surface morphologies were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The Ag incorporation on the ZnO NR surfaces was confirmed using EDS mapping and spectra. Furthermore, the chemical states, the variation in oxygen vacancies, and the surface modifications of Ag@ZnO were investigated by XPS analysis. Both the glucose/ZnO/Si and glucose/Ag@ZnO/Si device structures were investigated for their non-enzymatic glucose sensing performances with different glucose concentrations. Based on EIS measurements and amperometric analysis, the Ag@ZnO-NR-based glucose sensor device exhibited a better sensing ability with excellent stability over time than pure ZnO NRs. The Ag@ZnO NR glucose sensor device recorded 2792 µA/(mM·cm²) sensitivity with a lowest detection limit of 1.29 µM.

Different coatings on magnetic nanoparticles dictate their degradation kinetics in vivo for 15 months after intravenous administration in mice

BACKGROUND

The surface coating of iron oxide magnetic nanoparticle (MNPs) drives their intracellular trafficking and degradation in endolysosomes, as well as dictating other cellular outcomes. As such, we assessed whether MNP coatings might influence their biodistribution, their accumulation in certain organs and their turnover therein, processes that must be understood in vivo to optimize the design of nanoformulations for specific therapeutic/diagnostic needs.

RESULTS

In this study, three different MNP coatings were analyzed, each conferring the identical 12 nm iron oxide cores with different physicochemical characteristics: 3-aminopropyl-triethoxysilane (APS), dextran (DEX), and dimercaptosuccinic acid (DMSA). When the biodistribution of these MNPs was analyzed in C57BL/6 mice, they all mainly accumulated in the spleen and liver one week after administration. The coating influenced the proportion of the MNPs in each organ, with more APS-MNPs accumulating in the spleen and more DMSA-MNPs accumulating in the liver, remaining there until they were fully degraded. The changes in the physicochemical properties of the MNPs (core size and magnetic properties) was also assessed during their intracellular degradation when internalized by two murine macrophage cell lines. The decrease in the size of the MNPs iron core was influenced by their coating and the organ in which they accumulated. Finally, MNP degradation was analyzed in the liver and spleen of C57BL/6 mice from 7 days to 15 months after the last intravenous MNP administration.

CONCLUSIONS

The MNPs degraded at different rates depending on the organ and their coating, the former representing the feature that was fundamental in determining the time they persisted. In the liver, the rate of degradation was similar for all three coatings, and it was faster than in the spleen. This information regarding the influence of coatings on the in vivo degradation of MNPs will help to choose the best coating for each biomedical application depending on the specific clinical requirements.

Carbon Nano-Onion-Decorated ZnO Composite-Based Enzyme-Less Electrochemical Biosensing Approach for Glucose

This study investigates the enzyme-less biosensing property of the zinc oxide/carbon nano-onion (ZnO/CNO) nanocomposite coated on a glassy carbon electrode. The ZnO/CNO nanocomposite was synthesized using the ex situ mixing method, and the structural characterization was done using XRD, SEM, and TEM, whereas functional groups and optical characterization were done through FTIR and UV-visible spectroscopy. The electrochemical sensing response of the ZnO/CNO nanocomposite for the linear range of glucose concentration (0.1-15 mM) was examined using cyclic voltammetry (CV) with a potential window of -1.6 to +1.6 V using 0.1 M NaOH as an electrolyte. The ZnO/CNO nanocomposites showed enhanced sensing ability toward glucose with a sensitive value of 606.64 μA/mM cm². Amperometric i-t measurement supports the finding of CV measurement and showed good sensing ability of the electrode ZnO/CNO nanocomposite material for up to 40 days. The enhanced electrocatalytic activity of the ZnO/CNO nanocomposite is explained due to the synergetic effect of both ZnO and CNO. Our findings suggest a high potential for ZnO/CNO nanocomposite-based glucose biosensors, which could be further utilized to develop noninvasive skin-attached sensors for biomedical applications.

Scaling-up medical technologies using flexographic printing

Medical technologies, such as point-of-care devices and biological and chemical assays which rely on functional materials deposited on top of substrates, are in great demand due to an increase in the prevalence of diseases worldwide. A significant number of these medical technologies are still in their infancy with respect to commercialization because of the high cost, material and complexity of the conventionally available fabrication techniques. As a result, medical technologies, in broad terms, require low cost and mass production fabrication methods in order to overcome the commercialization challenges. Recently, researchers have explored the flexographic printing technique which is widely employed for food packaging and newspaper production. This technique has proved cost-effective, facile, rapid and industrially compatible fabrication technique of functional materials for various applications. In this review, we provide an account of the attempts of flexographic printing made to scale up functional materials on surfaces for biomedical applications. Firstly, we offer justification for demanding high-throughput fabrication techniques. We then present the facile working principle of the flexographic printing and its use in different medical applications, for example chronic disease monitoring devices, colorimetric sensors, electrochemical sensors, assays and drugs. Finally, we discuss challenges of the fabrication technique. The main purpose of this review is to give insights into the usefulness of flexographic printing to the health care industry.

Facile Method for Obtaining Gold-Coated Polyester Surfaces with Antimicrobial Properties

The antimicrobial and antifungal activity of polymers used in medical devices has been extensively studied due to the growing impact of hospital-related infections in patients. The ideal biocidal polymeric materials should be very effective in the microorganism’s inhibition, not toxic to the human body, and environmentally friendly. In this context, this work is aimed at obtaining antimicrobial and antifungal properties at the polyester film surfaces without introducing toxic effects. Poly (ethylene terephthalate) (PET) films were functionalized with Ar plasma and then immersed in a solution containing gold nanoparticles (AuNps). The results demonstrated the appearance of the hydrophilic groups on the film surface after modification of PET film by plasma Ar treatment and the formation of the polar groups such as C=O, COO-, and OH, which then reacted with AuNps. The changes induced in the treated polymer samples were investigated in terms of AuNp adsorption efficiency on polyester film by contact angle, profilometry, Scanning Electron Microscopy (SEM), Attenuated Total Reflectance Spectroscopy-Fourier Transform Infrared (ATR-FTIR), and X-ray Photoelectron Spectroscopy (XPS) measurements. The morphological and structural analyses have shown a good adhesion of AuNps at treated film surfaces. The results of biocompatibility antimicrobial and antifungal tests proved the nontoxic behavior of the sample and its good antimicrobial and antifungal activity.

ZnO Nanolower-Based NanoPCR as an Efficient Diagnostic Tool for Quick Diagnosis of Canine Vector-Borne Pathogens

Polymerase chain reaction (PCR) is a unique technique in molecular biology and biotechnology for amplifying target DNA strands, and is also considered as a gold standard for the diagnosis of many canine diseases as well as many other infectious diseases. However, PCR still faces many challenges and issues related to its sensitivity, specificity, efficiency, and turnaround time. To address these issues, we described the use of unique ZnO nanoflowers in PCR reaction and an efficient ZnO nanoflower-based PCR (nanoPCR) for the molecular diagnosis of canine vector-borne diseases (CVBDs). A total of 1 mM of an aqueous solution of ZnO nanoflowers incorporated in PCR showed a significant enhancement of the PCR assay with respect to its sensitivity and specificity for the diagnosis of two important CVBDs, Babesia canis vogeli and Hepatozoon canis. Interestingly, it drastically reduced the turnaround time of the PCR assay without compromising the yield of the amplified DNA, which can be of benefit for veterinary practitioners for the improved management of diseases. This can be attributed to the favorable adsorption of ZnO nanoflowers to the DNA and thermal conductivity of ZnO nanoflowers. The unique ZnO nanoflower-assisted nanoPCR greatly improved the yield, purity, and quality of the amplified products, but the mechanism behind these properties and the effects and changes due to the different concentrations of ZnO nanoflowers in the PCR system needs to be further studied.

A Review of the Construction of Nano-Hybrids for Electrochemical Biosensing of Glucose

Continuous progress in the domain of nano and material science has led to modulation of the properties of nanomaterials in a controlled and desired fashion. In this sense, nanomaterials, including carbon-based materials, metals and metal oxides, and composite/hybrid materials have attracted extensive interest with regard to the construction of electrochemical biosensors. The modification of a working electrode with a combination of two or three nanomaterials in the form of nano-composite/nano-hybrids has revealed good results with very good reproducibility, stability, and improved sensitivity. This review paper is focused on discussing the possible constructs of nano-hybrids and their subsequent use in the construction of electrochemical glucose biosensors.

The design, fabrication, and applications of flexible biosensing devices

Flexible biosensors form part of a rapidly growing research field that take advantage of a multidisciplinary approach involving materials, fabrication and design strategies to be able to function at biological interfaces that may be soft, intrinsically curvy, irregular, or elastic. Numerous exciting advancements are being proposed and developed each year towards applications in healthcare, fundamental biomedical research, food safety and environmental monitoring. In order to place these developments in perspective, this review is intended to present an overview on field of flexible biosensor development. We endeavor to show how this subset of the broader field of flexible and wearable devices presents unique characteristics inherent in their design. Initially, a discussion on the structure of flexible biosensors is presented to address the critical issues specific to their design. We then summarize the different materials as substrates that can resist mechanical deformation while retaining their function of the bioreceptors and active elements. Several examples of flexible biosensors are presented based on the different environments in which they may be deployed or on the basis of targeted biological analytes. Challenges and future perspectives pertinent to the current and future stages of development are presented. Through these summaries and discussion, this review is expected to provide insights towards a systematic and fundamental understanding for the fabrication and utilization of flexible biosensors, as well as inspire and improve designs for smart and effective devices in the future.

Microstructured prealloyed Titanium-Nickel powder as a novel nonenzymatic hydrogen peroxide sensor

At present, commercial pure Titanium (Ti) and microstructured pre-alloyed Titanium-Nickel (TiNi) powders are employed as a sensitive electrochemical hydrogen peroxide (H₂O₂) sensor. Surface characterization of these materials are performed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical characterization is achieved via cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) on Ti and TiNi modified glassy carbon electrode (GCE). The electrochemical behavior of H₂O₂ at the pure Ti/GCE and microstructure pre-alloyed TiNi/GCE are studied by CV in 0.1 M phosphate buffer solution (PBS) containing as the supporting electrolyte. In addition, CA is employed for the determination of H₂O₂ at the applied potential of 0 V vs. Ag/AgCl. The sensor has a linear response range of 0.5-17.5 mM with a sensitivity of 280 µA mM^-1 cm^-2. Moreover, the limit of detection (LOD) and limit of quantification (LOQ) are 0.5 µM and 1.7 µM, respectively. The electrochemical sensor exhibits fast and selective responses to H₂O₂ concentration. The applicability of the sensor is checked using a hair coloring as a real sample with satisfactory results.

Biofunctionalized "Kiwifruit-Assembly" of Oxidoreductases in Mesoporous ZnO/Carbon Nanoparticles for Efficient Asymmetric Catalysis

A mesoporous ZnO/carbon composite is designed for coimmobilization of two oxidoreductases involving a novel "kiwifruit-assembly" pattern. The coimmobilization of (S)-carbonyl reductase II-glucose dehydrogenase on nanoparticles (SCRII-GDH_nano ) exhibits 40-50% higher specific activity than the free enzyme and significantly improves stabilities of enzymes to heat, pH and solvents. It performs asymmetric catalysis of 75 × 10^-3 m substrate with a perfect yield of 100% and an excellent enantioselectivity of 99.9% within 1 h. SCRII-GDH_nano gives an over 72% yield and 99.9% enantioselectivity after it is reused for ten times. Even with a highly concentrated (400 × 10^-3 m) substrate, it shows about 60% yield and 99.9% enantioselectivity within 4 h. SCRII-GDH_nano presents 4.5-8.0-fold higher productivity in 2.0-8.0-fold shorter reaction time than the free enzyme. This work provides a general, facile, and unique approach for the immobilization of two oxidoreductases and gives high catalytic efficiency, long-term and good recycling stabilities by triggering radical proton-coupled electron transfer.

Doping Ag in ZnO Nanorods to Improve the Performance of Related Enzymatic Glucose Sensors

In this paper, the performance of a zinc oxide (ZnO) nanorod-based enzymatic glucose sensor was enhanced with silver (Ag)-doped ZnO (ZnO-Ag) nanorods. The effect of the doped Ag on the surface morphologies, wettability, and electron transfer capability of the ZnO-Ag nanorods, as well as the catalytic character of glucose oxidase (GOx) and the performance of the glucose sensor was investigated. The results indicate that the doped Ag slightly weakens the surface roughness and hydrophilicity of the ZnO-Ag nanorods, but remarkably increases their electron transfer ability and enhances the catalytic character of GOx. Consequently, the combined effects of the above influencing factors lead to a notable improvement of the performance of the glucose sensor, that is, the sensitivity increases and the detection limit decreases. The optimal amount of the doped Ag is determined to be 2 mM, and the corresponding glucose sensor exhibits a sensitivity of 3.85 μA/(mM·cm²), detection limit of 1.5 μM, linear range of 1.5 × 10^-3-6.5 mM, and Michaelis-Menten constant of 3.87 mM. Moreover, the glucose sensor shows excellent selectivity to urea, ascorbic acid, and uric acid, in addition to displaying good storage stability. These results demonstrate that ZnO-Ag nanorods are promising matrix materials for the construction of other enzymatic biosensors.

A novel polyurethane/nano ZnO matrix for immobilization of chitinolytic enzymes and optical sensing of chitin

Purified chitinase from Vigna mungo and N-acetyl β glucosaminidase (NAGase) from Canavalia ensiformis were immobilized on to the novel polyurethane (PU)/zinc oxide nanoparticles (nano ZnO) composite matrix with a conjugation yield of 0.785±0.01mg/cm² and 96.19±0.85% retention of specific activity. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) also confirmed the presence of nano ZnO and enzymes on the PU support. Thus synthesized PU/nano ZnO/chitinase/NAGase conjugates were optimized with respect to pH, temperature and substrate concentration and successfully employed for development of an absorbance based optical biosensor for chitin determination in stored wheat grains. The limit of detection was 0.01mM with linearity from 0.1 to 10.0mM. The% recoveries of added chitin (0.1 and 0.2mM) were >95.0% and >96.5% respectively and within-day and between-day coefficients of variations were 1.03% and 1.78% respectively. The method showed good correlation (R²=0.996) with the popular 3,5-dinitrosalicylic acid method. PU/nano ZnO bound chitinase/NAGase showed good thermal and storage stabilities and could be reused 10 times without any appreciable loss of activity.

Flower-like ZnO nanostructure assisted loop-mediated isothermal amplification assay for detection of Japanese encephalitis virus

In this study, we described a novel and effective flower-like ZnO nanostructure assisted Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) method to detect Japanese Encephalitis Virus (JEV). The effects of different concentrations of ZnO nanoflower on the RT-LAMP reaction were investigated. With the increase of concentration of ZnO nanoflower, RT-LAMP reaction obtained optimization, until the concentration exceeded 1.5nM, RT-LAMP reaction was inhibited. Made 1nM as optimum concentration of ZnO nanoflower, we found that optimum RT-LAMP reaction temperature and time were 60°C and 30min, respectively. The optimization might be connected with good adsorption to DNA and thermal conductivity of ZnO nanoflower, but mechanism of the RT-LAMP reaction affected by ZnO nanoflower needs to be explored further.

A multi-walled carbon nanotube–zinc oxide nanofiber based flexible chemiresistive biosensor for malaria biomarker detection

A flexible, lightweight and disposable chemiresistive biosensor for label free detection of the malaria biomarker.

Nanotextured Surface on Flexographic Printed ZnO Thin Films for Low-Cost Non-Faradaic Biosensors

In this work, the formation of a nanotextured surface is reported on flexographic printed zinc oxide thin films which provide an excellent platform for low-cost, highly sensitive biosensing applications. The ability to produce nanotextured surfaces using a high-throughput, roll-to-roll production method directly from precursor ink without any complicated processes is commercially attractive for biosensors that are suitable for large-scale screening of diseases at low cost. The zinc oxide thin film was formed by printing a zinc acetate precursor ink solution and annealing at 300 °C. An intricate nanotexturing of the film surface was achieved through 150 °C drying process between multiple prints. These surface nanostructures were found to be in the range of 100 to 700 nm in length with a width of 58 ± 18 nm and a height of between 20 and 60 nm. Such structures significantly increase the surface area to volume ratio of the biosensing material, which is essential to high sensitivity detection of diseases. Nonfaradaic electrochemical impedance spectroscopy measurements were carried out to detect the pp65-antigen of the human cytomegalovirus using the printed device, which has a low limit of detection of 5 pg/mL.

One step biofunctionalized electrospun multiwalled carbon nanotubes embedded zinc oxide nanowire interface for highly sensitive detection of carcinoma antigen-125

Ovarian cancer is the most leading cause of cancer-related death in women . The carcinoma antigen-125, which is found on the surface of many ovarian cancer cells is known to be a gold standard clinical biomarker associated with life-threatening gynecological malignancy. In this work, we demonstrate a novel biosensor platform based on multiwalled carbon nanotubes embedded zinc oxide nanowire for the ultrasensitive detection of carcinoma antigen-125. Label free detection of the carcinoma antigen-125 was accomplished by differential voltammetry technique that demonstrated excellent sensitivity (90.14µA/(U/mL)/cm²) with a detection limit of 0.00113UmL^-1 concentration. The fabricated immunosensor exhibits good performance with wider detection range (0.001UmL^-1-1kUmL^-1), reproducibility, selectivity, acceptable stability, and thus is a potential cost-effective methodology for point-of-care diagnosis. The multiwalled carbon nanotubes (MWCNTs) embedded highly oriented zinc oxide (ZnO) nanowires were synthesized by simple, low cost electrospinning technique. Compared to pure ZnO nanowires, electrochemical activity of MWCNTs embedded ZnO nanowires was found to be much higher. The calcination temperature was optimized to avoid any decomposition of the CNTs and to obtain multiwalled carbon nanotubes embedded highly crystalline ZnO nanowires. The salient feature of this biosensing platform is that one step calcination process is enough to create the functional groups on MWCNT-ZnO nanowire surface that are effective for the covalent conjugation of antibody without further surface modification. To the best of our knowledge, this is the first report on MWCNT-ZnO nanowire based immunosensor explored for the detection of cancer biomarker.

Fundamental Properties of One-Dimensional Zinc Oxide Nanomaterials and Implementations in Various Detection Modes of Enhanced Biosensing

Recent bioapplications of one-dimensional (1D) zinc oxide (ZnO) nanomaterials, despite the short development period, have shown promising signs as new sensors and assay platforms offering exquisite biomolecular sensitivity and selectivity. The incorporation of 1D ZnO nanomaterials has proven beneficial to various modes of biodetection owing to their inherent properties. The more widely explored electrochemical and electrical approaches tend to capitalize on the reduced physical dimensionality, yielding a high surface-to-volume ratio, as well as on the electrical properties of ZnO. The newer development of the use of 1D ZnO nanomaterials in fluorescence-based biodetection exploits the innate optical property of their high anisotropy. This review considers stimulating research advances made to identify and understand fundamental properties of 1D ZnO nanomaterials, and examines various biosensing modes utilizing them, while focusing on the unique optical properties of individual and ensembles of 1D ZnO nanomaterials specifically pertaining to their bio-optical applications in simple and complex fluorescence assays.

Fundamental Properties of One-Dimensional Zinc Oxide Nanomaterials and Implementations in Various Detection Modes of Enhanced Biosensing

Recent bioapplications of one-dimensional (1D) zinc oxide (ZnO) nanomaterials, despite the short development period, have shown promising signs as new sensors and assay platforms offering exquisite biomolecular sensitivity and selectivity. The incorporation of 1D ZnO nanomaterials has proven beneficial to various modes of biodetection owing to their inherent properties. The more widely explored electrochemical and electrical approaches tend to capitalize on the reduced physical dimensionality, yielding a high surface-to-volume ratio, as well as on the electrical properties of ZnO. The newer development of the use of 1D ZnO nanomaterials in fluorescence-based biodetection exploits the innate optical property of their high anisotropy. This review considers stimulating research advances made to identify and understand fundamental properties of 1D ZnO nanomaterials, and examines various biosensing modes utilizing them, while focusing on the unique optical properties of individual and ensembles of 1D ZnO nanomaterials specifically pertaining to their bio-optical applications in simple and complex fluorescence assays.

Effect of changing the nanoscale environment on activity and stability of nitrate reductase

Nitrate reductase (NR) is employed for fabrication of nitrate sensing devices in which the enzyme in immobilized form is used to catalyze the conversion of nitrate to nitrite in the presence of a suitable cofactor. So far, instability of immobilized NR due to the use of inappropriate immobilization matrices has limited the practical applications of these devices. Present study is an attempt to improve the kinetic properties and stability of NR using nanoscale iron oxide (nFe3O4) and zinc oxide (nZnO) particles. The desired nanoparticles were synthesized, surface functionalized, characterized and affixed onto the epoxy resin to yield two nanocomposite supports (epoxy/nFe3O4 and epoxy/nZnO) for immobilizing NR. Epoxy/nFe3O4 and epoxy/nZnO support could load as much as 35.8±0.01 and 33.20±0.01μg/cm(2) of NR with retention of about 93.72±0.50 and 84.81±0.80% of its initial activity respectively. Changes in surface morphology and chemical bonding structure of both the nanocomposite supports after addition of NR were confirmed by scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). Optimum working conditions of pH, temperature and substrate concentration were ascertained for free as well as immobilized NR preparations. Further, storage stability at 4°C and thermal stability between 25-50°C were determined for all the NR preparations. Analytical applications of immobilized NR for determination of soil and water nitrates along with reusability data has been included to make sure the usefulness of the procedure.

A highly sensitive self assembled monolayer modified copper doped zinc oxide nanofiber interface for detection of Plasmodium falciparum histidine-rich protein-2: Targeted towards rapid, early diagnosis of malaria

Rapid, ultrasensitive diagnostic/triaging kits for early detection of malarial parasites are critical for prevention of malarial epidemic, especially in developing and tropical countries. Unlike traditional microscopic diagnosis, these kits rely on the detection of antigens specific to malarial parasites. One such antigen which is routinely used in these diagnostic kits is Histidine-rich protein-2; a protein synthesized and released into the blood stream by the parasite Plasmodium falciparum. In this paper, we demonstrate an ultrasensitive nanobiosensor detection platform for Histidine-rich protein-2 having a limit of detection of attogram/ml. This nanobiosensor platform comprises of Mercaptopropylphosphonic acid functionalized copper doped zinc oxide nanofibers synthesized by electrospinning technique. Ultrasensitivity of attogram/ml can be attributed to the complimentary effects of Mercaptopropylphosphonic acid and copper doping in zinc oxide. Mercaptopropylphosphonic acid enhances the functional groups required for immobilizing antibody. Copper doping in zinc oxide not only increases the conductivity of the nanofibers but also pre-concentrates the target analyte onto the Mercaptopropylphosphonic acid treated nanofiber surface due to inherent electric field generated at the copper/zinc oxide heterojunction interface. The impedimetric detection response of copper-doped zinc oxide nanofiber modified electrode shows excellent sensitivity (28.5 kΩ/(gm/ml)/cm(2)) in the detection ranges of 10 ag/ml-10 µg/ml, and a detection limit of 6 attogram/ml. In addition, the proposed biosensor is highly selective to targeted HRP2 protein with a relative standard deviation of 1.9% in the presence of various interference of nonspecific molecules. To the best of our knowledge, this biosensor shows the lowest detection limit of malarial parasites reported in the literature spanning different nanomaterials and different detection mechanisms. Since the nanobiosensor platform is based on immunoassay technique, with a little modification, it can be extended for developing point-of-care diagnostic devices for several biomarkers of importance.

Glucose oxidase stabilized fluorescent gold nanoparticles as an ideal sensor matrix for dual mode sensing of glucose

A simple, facile and green route for the preparation of glucose oxidase stabilized simple Au NPs and fluorescent Au NPs for the dual mode bio-sensing application of glucose using colourimetric and electrochemical methods is demonstrated.

Low-Index ZnO Crystal Plane-Specific Binding Behavior of Whole Immunoglobulin G Proteins

Crystallographic surface-resolved examination of protein-ZnO interactions can greatly enhance the fundamental understanding of protein adsorption on these technologically important solid surfaces which, in turn, will be tremendously valuable for the emerging applications of ZnO-based biomaterials and biosensors. We examine experimentally and via computer simulations the intriguing differences in the adsorption preferences and binding behavior of whole immunoglobulin G (IgG) proteins to various, low-index ZnO crystal surfaces at the individual biomolecule level. By performing direct atomic force microscopy imaging, we determine that IgG predominantly binds to the ZnO plane of (101̅0) relative to the other three low-index planes of (0001), (0001̅), and (112̅0). This phenomenon is highly unusual, particularly considering the fact that the average binding energy of amino acids (AAs) on the ZnO (0001) facet is higher than that on the (101̅0) plane. In conjunction with combined Monte Carlo-molecular dynamics simulations, we further explain the possible origins of our unusual experimental findings with critical factors such as the specific spatial locations of strongly binding AAs in the protein and their spatial distributions on the exterior surface of the protein.

Protein adsorption onto nanomaterials for the development of biosensors and analytical devices: a review

An important consideration for the development of biosensors is the adsorption of the biorecognition element to the surface of a substrate. As the first step in the immobilization process, adsorption affects most immobilization routes and much attention is given into the research of this process to maximize the overall activity of the biosensor. The use of nanomaterials, specifically nanoparticles and nanostructured films, offers advantageous properties that can be fine-tuned to maximize interactions with specific proteins to maximize activity, minimize structural changes, and enhance the catalytic step. In the biosensor field, protein-nanomaterial interactions are an emerging trend that span across many disciplines. This review addresses recent publications about the proteins most frequently used, their most relevant characteristics, and the conditions required to adsorb them to nanomaterials. When relevant and available, subsequent analytical figures of merits are discussed for selected biosensors. The general trend amongst the research papers allows concluding that the use of nanomaterials has already provided significant improvements in the analytical performance of many biosensors and that this research field will continue to grow.

A novel electrochemiluminescent immunosensor based on CdS-coated ZnO nanorod arrays for HepG2 cell detection

In this work, the highly oriented CdS-coated-ZnO nanorod arrays have been fabricated. The CdS-coated-ZnO nanorod arrays show high electrochemiluminescence intensity, fast response and good stability. All of the desirable properties spur the development of an ECL immunosensor for the detection of the liver cancer cell line (HepG2 cells). Two successive modification steps of 3-aminopropyltriethoxysilane and gold nanoparticles onto the CdS-coated-ZnO nanorod arrays not only offer the substrates for conjugation of antibody, but also effectively enhance the ECL signal, resulting in production of the high performance ECL immunosensor. The ECL immunosensor exhibits a sensitive response to HepG2 cells in a linear range of 300-10,000 cells mL(-1) with a detection limit of 256 cells mL(-1). The proposed sensor characteristics of high specificity, good reproducibility and remarkable stability will provide a sensitive, selective, and convenient approach for the clinical detection of cancer cells.

Electrodeposition of ZnCo2O4 nanoparticles for biosensing applications

Electrochemical sensing properties of electrodeposited ZnCo₂O₄ nanoparticles towards glucose and dopamine are investigated.

Ultrasensitive non-enzymatic glucose sensor based on three-dimensional network of ZnO-CuO hierarchical nanocomposites by electrospinning

Three-dimensional (3D) porous ZnO-CuO hierarchical nanocomposites (HNCs) nonenzymatic glucose electrodes with different thicknesses were fabricated by coelectrospinning and compared with 3D mixed ZnO/CuO nanowires (NWs) and pure CuO NWs electrodes. The structural characterization revealed that the ZnO-CuO HNCs were composed of the ZnO and CuO mixed NWs trunk (~200 nm), whose outer surface was attached with small CuO nanoparticles (NPs). Moreover, a good synergetic effect between CuO and ZnO was confirmed. The nonenzymatic biosensing properties of as prepared 3D porous electrodes based on fluorine doped tin oxide (FTO) were studied and the results indicated that the sensing properties of 3D porous ZnO-CuO HNCs electrodes were significantly improved and depended strongly on the thickness of the HNCs. At an applied potential of + 0.7 V, the optimum ZnO-CuO HNCs electrode presented a high sensitivity of 3066.4 μAmM(-1)cm(-2), the linear range up to 1.6 mM, and low practical detection limit of 0.21 μM. It also showed outstanding long term stability, good reproducibility, excellent selectivity and accurate measurement in real serum sample. The formation of special hierarchical heterojunction and the well-constructed 3D structure were the main reasons for the enhanced nonenzymatic biosensing behavior.

Electrospun Porous ZnO Nanofibers for Glucose Biosensors

Porous 1 dimensional (1D) ZnO nanofibers were synthesized by electrospinning technology and sequent annealing process. The ZnO nanofibers have many nanopores in it and connect to each other to form a porous film. The diameters of the nanofibers are about 100 nm, and their lengths are so long as tens of millimeters. Owing to the porous nanofibers based matrix has 1D channels and high isoelectric point, the prepared ZnO porous film is wonderful platform to immobilize glucose oxidase enzyme for glucose biosensing. The as-fabricated biosensor exhibited high sensitivity (69 μA/mMcm-2), fast response (3 s) and low detection limit (10 μM), due to the nanomaterial with large surface-to-volume ratio for enzyme immobilization and excellent electrical properties. The biosensors can be fabricated controllably and repeatedly. These excellent results indicate the biosensors are attractive for application.