Metal oxide nanomaterials based electrochemical and optical biosensors for biomedical applications: Recent advances and future prospectives.

The amalgamation of nanostructures with modern electrochemical and optical techniques gave rise to interesting devices, so-called biosensors. A biosensor is an analytical tool that incorporates various biomolecules with an appropriate physicochemical transducer. Over the past few years, metal oxide nanomaterials (MONMs) have significantly stimulated biosensing research due to their desired functionalities, versatile chemical stability, and low cost along with their unique optical, catalytic, electrical, and adsorption properties that provide an attractive platform for linking the biomolecules, for example, antibodies, nucleic acids, enzymes, and receptor proteins as sensing elements with the transducer for the detection of signals or signal amplifications. The signals to be measured are in direct proportionate to the concentration of the bioanalyte. Because of their simplicity, cost-effectiveness, portability, quick analysis, higher sensitivity, and selectivity against a broad range of biosamples, MONMs-based electrochemical and optical biosensing platforms are exhaustively explored as powerful early-diagnosis tools for point of care applications. Herein, we made a bibliometric analysis of past twenty years (2004-2023) on the application of MONMs as electrochemical and optical biosensing units using Web of Science database and the results of which clearly reveal the increasing number of publications since 2004. Geographical area distribution analysis of these publications shows that China tops the list followed by the United States of America and India. In this review, we first describe the electrochemical and optical properties of MONMs that are crucial for the creation of extremely stable, specific, and sensitive sensors with desirable characteristics. Then, the biomedical applications of MONMs-based bare and hybrid electrochemical and optical biosensing frameworks are highlighted in the light of recent literature. Finally, current limitations and future challenges in the field of biosensing technology are addressed.

Antidiabetic potential of Gymnemic acid mediated gold nanoparticles (Gym@AuNPs) on Streptozotocin-induced diabetic rats-An implication on in vivo approach.

Gymnemic acid is glycosides of triterpene with recognized and valuable applications for several chronic diseases, mainly diabetics. Despite this, it requires a delivery system in order to range its therapeutic target due to its limited solubility and bioavailability. Therefore, the Gymnemic acid mediated gold nanoparticles (Gym@AuNPs) was synthesised by eco-friendly approach. The synthesised Gym@AuNPs was confirmed by the colour change from light yellow to a deep ruby red. UV - visible spectroscopy results showed a strong narrow peak at 530 nm, confirming the controlled synthesis of monodispersed Gym@AuNPs. The reduction potential of standard Gymnemic acid (Gym) on synthesis of Gym@AuNPs was confirmed by using HPLC analysis. The spherical shaped Gym@AuNPs was observed by FESEM and HR-TEM studies with average size of 48.52 ± 5.53 nm. The XRD analysis exhibited a face-centered cubic (FCC) crystalline nature of Gym@AuNPs. The in vivo antidiabetic activity of Gym and Gym@AuNPs were validated using Streptozotocin induced diabetic Albino wistar rats. The Gym@AuNPs and Gym were regulates the glucose and lipid levels in experimental animals. The histopathology outcomes shown that the Gym@AuNPs were restoration of pancreatic islets cells in the animals. This investigation demonstrated that the Gym@AuNPs had the potential anti-diabetic properties.

Hierarchical SnO2nanoflower sensitized by BNQDs enhances the gas sensing performances to BTEX.

In this study, the SnO2nanoflowers with hierarchical structures sensitized by boron nitride quantum dots (BNQDs) were prepared through a simple hydrothermal method. It was applied for the detection of the BTEX vapors. Further investigation showed that the response value of SnO2sensitized by different amounts of BNQDs to the BTEX gases have a certain improvement. Especially 10-BNQDs/SnO2gas sensor exhibited a significant improvement in gas sensing performance and its response values to different BTEX gases was increased up to 2-4 folds compared with the intrinsic SnO2sensor. In addition, SnO2nanoflowers based gas sensor showed surprisingly fast response and recovery time for BTEX gases with 1-2 s. That can be attributed to the sensitization of BNQDs and the hierarchical structure of SnO2nanoflowers, which provided an easy channel for the gas diffusion. An economically viable gas sensor based on BNQDs sensitized SnO2nanoflowers exhibited a great potential in BTEX gas detection due to the simple synthesis method, environmentally friendly raw materials and excellent gas sensing performance.

Silver nanoparticles decorated reduced graphene oxide: Eco-friendly synthesis, characterization, biological activities and embryo toxicity studies.

This study was aimed on the eco-friendly synthesis of silver nanoparticles (AgNPs), reduced graphene oxide (rGO) and AgNPs decorated rGO (rGO/AgNPs) nanocomposite and appraisal of their bioactivities and toxicity. As-prepared nanomaterials were established through high resolution X-ray diffraction (HR-XRD), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-Vis. spectroscopy and Fourier transform infrared spectroscopy (FT-IR). In this study, leaves extract, graphene oxide (GO) and rGO did not show antibacterial and anticancer activities; no significant embryo toxicity was recorded. On the other hand, AgNPs displayed good antibacterial and anticancer activities; however, higher toxic effects were observed even at the lowest test concentration (0.7 µg/ml). In case of rGO/AgNPs nanocomposite, significant antibacterial activity together with low cytotoxicity was noticed. Interestingly, the embryo toxicity of AgNPs was significantly reduced by rGO, implying the biocompatible nature of as-synthesized nanocomposite. Taken together, these results clearly suggest that rGO/AgNPs nano hybrid composite could be developed as the promising biomaterial for future biomedical applications.

A review on the toxicity of silver nanoparticles against different biosystems.

Despite significant progress made in the past two decades, silver nanoparticles (AgNPs) have not yet made it to the clinical trials. In addition, they showed both positive and negative effects in their toxicity from unicellular organism to well-developed multi-organ system, for example, rat. Although it is generally accepted that capped (bio)molecules have synergistic bioactivities and diminish the toxicity of metallic Ag core, convincing evidence is completely lacking. Therefore, in this review, we first highlight the recent in vivo toxicity studies of chemically manufactured AgNPs, biologically synthesized AgNPs and reference AgNPs of European Commission. Then, their toxic effects are compared with each other and the overlooked factors leading to the potential conflict of obtained toxicity results are discussed. Finally, suggestions are given to better design and conduct the future toxicity studies and to fast-track the successful clinical translation of AgNPs as well.

Synthesis, characterization and biological applications of mycosynthesized silver nanoparticles.

Silver nanoparticles (AgNPs) have been known for their inhibitory and bactericidal effects. In the present study, less toxic AgNPs using Cunninghamella echinulata is reported for the first time. The obtained AgNPs were characterized using UV-Visible spectrophotometer, XRD, FT-IR, FE-SEM with EDAX and HR-TEM. AgNPs showed the maximum absorbance at 420-430 nm. The transmission electron micrograph revealed the formation of considerably uniform-sized AgNPs with an average size of 20-50 nm. The reducing and capping agents responsible for AgNP synthesis were identified by FT-IR. AgNP-incorporated cotton fabrics exhibited promising antibacterial activity against pathogenic bacteria. In addition, the in vitro cell viability of Vero cells (African green monkey kidney cells) was analyzed and the IC50 value of AgNPs was found to be 62.8 µg/mL. Taken together, these results clearly reveal less toxic AgNPs which could be exploited for various biomedical applications.

Prevalence of Campylobacter jejuni and enteric bacterial pathogens among hospitalized HIV infected versus non-HIV infected patients with diarrhoea in southern India.

A prevalence study on Campylobacter jejuni and other enteric bacterial pathogens was carried out in 200 HIV infected and 200 non-HIV infected subjects with diarrhoeal symptoms at an AIDS Hospital in southern India. Diarrhoeal specimens were inoculated onto standard culture media as well as onto Columbia and Campylobacter blood agar media for C. jejuni isolation. All the C. jejuni isolates were tested for antimicrobial susceptibility using Kirby-Bauer's method. A significant difference in recovery rates was observed between the 2 groups in relation to C. jejuni (p < or = 0.02; 95% CI 5.5 (1-10) and Shigella spp. (p < or = 0.02; 95% CI 6.5 (1-12). 21 isolates of Shigella spp., 16 C. jejuni, 5 Salmonella typhi, 3 Arcobacter spp., 3 Yersinia enterocolitica, and 2 Aeromonas hydrophila were recovered from the HIV infected cases. All the C. jejuni isolates were sensitive to ciprofloxacin whereas 1 strain was resistant to nalidixic acid. Interestingly, all the 29 Shigella spp. (21 from HIV and 8 from non-HIV cases) were resistant to erythromycin and most were resistant to many other antibiotics used. Our observations underline the need for epidemiological investigations to screen C. jejuni and Shigella spp. in HIV infected subjects with diarrhoea and analyse their antibiograms periodically to minimize disease burden in HIV/AIDS.