Nanostructured wearable electrochemical and biosensor towards healthcare management: a review

In recent years, there has been a rapid increase in demand for wearable sensors, particularly these tracking the surroundings, fitness, and health of people. Thus, selective detection in human body fluid is a demand for a smart lifestyle by quick monitoring of electrolytes, drugs, toxins, metabolites and biomolecules, proteins, and the immune system. In this review, these parameters along with the main features of the latest and mostly cited research work on nanostructured wearable electrochemical and biosensors are surveyed. This study aims to help researchers and engineers choose the most suitable selective and sensitive sensor. Wearable sensors have broad and effective sensing platforms, such as contact lenses, Google Glass, skin-patch, mouth gourds, smartwatches, underwear, wristbands, and others. For increasing sensor reliability, additional advancements in electrochemical and biosensor precision, stability in uncontrolled environments, and reproducible sample conveyance are necessary. In addition, the optimistic future of wearable electrochemical sensors in fields, such as remote and customized healthcare and well-being is discussed. Overall, wearable electrochemical and biosensing technologies hold great promise for improving personal healthcare and monitoring performance with the potential to have a significant impact on daily lives. These technologies enable real-time body sensing and the communication of comprehensive physiological information.

Label free flexible electrochemical DNA biosensor for selective detection of Shigella flexneri in real food samples

An effective tool for early-stage selective detection of the foodborne bacterial pathogen Shigella flexneri (S. flexneri) is essential for diagnosing infectious diseases and controlling outbreaks. Here, a label-free electrochemical DNA biosensor for monitoring S. flexneri is developed. To fabricate the biosensor, detection probe (capture probe) is immobilized on the surface of poly melamine (P-Mel) and poly glutamic acid (PGA), and disuccinimidyl suberate (DSS) functionalized flexible indium tin oxide (ITO) electrode. Anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) is used as a signal indicator for the detection of S. flexneri. The proposed DNA biosensor exhibits a wide dynamic range with concentration of the targets ranging from 1 × 10^-6 to 1 × 10^-21 molL^-1 with a limit of detection (LOD) of 7.4 × 10^-22 molL^-1 in the complementary linear target of S. flexneri, and a detection range of 8 × 10¹⁰-80 cells/ml with a LOD of 10 cells/ml in real S. flexneri sample. The proposed flexible biosensor provides high specificity for the detection of S. flexneri compared to other target signals such as discrete base mismatches and different bacterial species. The developed biosensor displayed excellent recoveries in detecting S. flexneri in spiked food samples. Therefore, the proposed biosensor can serve as a model methodology for the detection of other pathogens in a broad span of industries.

Development of a hematite nanotube and tyramine-based drug carrier against drug-resistant bacteria Klebsiella pneumoniae

In this study, hematite nanotube (HNT) and tyramine-based advanced nano-drug carriers were developed for inhibiting the growth of Klebsiella pneumoniae (K. pneumoniae). The HNT was synthesized by following the Teflon line autoclaved assisted hydrothermal process and tyramine was incorporated on the surface of the HNT to fabricate the formulated nano-drug. The nano-drug was prepared by conjugating meropenem (MP) on the surface of Tyramine-HNT and characterized using different techniques, such as scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared (ATR-FTIR), etc. Furthermore, the drug-loading efficiency and loading capacity were measured using a UV-vis spectrometer. The pH, amount of Tyr, and HNT required for drug loading were optimized. A controlled and gradual manner of pH-sensitive release profiles was found after investigating the release profile of MP from the carrier drug. The antibacterial activity of MP@Tyramine-HNT and MP was compared through the agar disc diffusion method which indicates that antibacterial properties of antibiotics are enhanced after conjugating. Surprisingly, the MP@Tyramine-HNT exhibits a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of K. pneumoniae lower than MP itself. These results indicate the nanocarrier can reduce the amount of MP dosed to eradicate K. pneumoniae.

Graphitic carbon nitride and APTES modified advanced electrochemical biosensor for detection of 17β-estradiol in spiked food samples

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples. The biosensing system is based on graphitic carbon nitride (g-C₃N₄) and a conductive polymer 3-aminopropyltriethoxysilane (APTES). The proposed biosensor shows the ability to detect E2 in attomolar levels within a wide linear logarithm concentration range of 1 × 10⁻⁶ to 1 × 10⁻¹⁸ mol L⁻¹ with a limit of detection (LOD) of 9.9 × 10⁻¹⁹ mol L⁻¹. The selectivity of the developed biosensor was confirmed by conducting the DPV of similarly structured hormones and naturally occurring substances. The proposed biosensor is highly stable and applicable to detect E2 in the presence of spiked food and environmental samples with satisfactory recoveries ranging from 95.1 to 104.8%. So, the designed electrochemical biosensor might be an effective alternative tool for the detection of E2 and other endogenous substances to attain food safety.

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples.

Development of an advanced DNA biosensor for pathogenic Vibrio cholerae detection in real sample

Due to the epidemics of emerging microbial diseases worldwide, the accurate and rapid quantification of pathogenic bacteria is extremely critical. In this work, a highly sensitive DNA-based electrochemical biosensor has been developed to detect Vibrio cholerae using gold nanocube and 3-aminopropyltriethoxysilane (APTES) modified glassy carbon electrode (GCE) with DNA carrier matrix. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) experiments were performed to interrogate the proposed sensor at each stage of preparation. The biosensor has demonstrated high sensitivity with a wide linear response range to target DNA from 10^-8 to 10^-14 (R²= 0.992) and 10^-14 to 10^-27 molL^-1 (R²= 0.993) with a limit of detection (LOD) value of 7.41 × 10^-30 molL^-1 (S/N = 5). The biosensor also exhibits a selective detection behavior in bacterial cultures that belong to the same and distant genera. Moreover, the proposed sensor can be used for six consecutive DNA assays with a repeatability relative standard deviations (RSD) value of 5% (n = 5). Besides, the DNA biosensor shows excellent recovery for detecting V. cholerae in poultry feces, indicating that the designed biosensor could become a powerful tool for pathogenic microorganisms screening in clinical diagnostics, food safety, and environmental monitoring.

Synthesis and characterization of nanozeolite based composite fertilizer for sustainable release and use efficiency of nutrients

In this research work, we propose macronutrients incorporated slow-release based nano-fertilizer using nanozeolite as a carrier. A simple chemical approach was used to synthesis the proposed nanozeolite composite fertilizer (NZCF). To gain an insight into the properties, morphology and structure of the synthesized NZCF, it was further characterized by different techniques such as powder XRD, FT-IR, SEM, and TG/DTA. A considerable enhancement of the quality and the water retention capacity of the soil was observed as a result of applying the proposed NZCF when compared with a commercial fertilizer. Furthermore, the swelling ratio and the equilibrium water content of NZCF were compared to the commercial fertilizer and their effect on plant growth was observed. Slow-release studies were carried out for both NZCF and the commercial fertilizer. The results of these studies reveled that NZCF possessed a long-term release pattern of the macronutrients and that showed a great potential for promoting plant growth. Hence, the prepared nanocomposite fertilizer can be safely used as an environment-friendly source of nutrients to enhance plant growth.

N-Hydroxysuccinimide crosslinked graphene oxide–gold nanoflower modified SPE electrode for sensitive detection of chloramphenicol antibiotic

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs). Furthermore, a screen printed electrode (SPE) modified with the introduced composite is electrochemically reduced to obtain an SPE/rGO–NHS–AuNFs electrode for sensitive and selective determination of chloramphenicol (CAP) antibiotic drug. The morphological structure of the as-prepared nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, Fourier-transform infrared spectroscopy and electrochemical impedance spectroscopy. The proposed sensor demonstrated excellent performance with a linear concentration range of 0.05 to 100 μM and a detection limit of 1 nM. The proposed electrode offers a high level of selectivity, stability, reproducibility and a satisfactory recovery rate for electrochemical detection of CAP in real samples such as blood serum, poultry feed, milk, eggs, honey and powdered milk samples. This further demonstrates the practical feasibility of the proposed sensor in food analysis.

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs).

Recent Biosensors for Detection of Antibiotics in Animal Derived Food

Antibiotics are extensively employed as bacteriostatic agents for fighting against microbial infection in animals. However, inappropriate doses of antibiotic drugs may result in antibiotic residues in food of animal origin and may cause various side effects on human health. Moreover, the transferor of antibiotic-resistant bacteria to humans through the food chain may induce serious health hazards. Hence, it is vital to develop sensitive and selective methods for rapid screening and regular monitoring of antibiotic residues in animal-derived foods. The conventional different chromatographic and spectroscopic techniques are time-consuming, expensive and require skilled personnel. To overcome such limitations, biosensors have emerged as an innovative approach recently and integrated with nanotechnologies for sensitive, rapid and on-site monitoring of different antibiotic residues in animal origin foods. This mini-review aims to give an overview of the currently available biosensing techniques to detect antibiotic residue in foods.

Influence of nanoparticle-based nano-nutrients on the growth performance and physiological parameters in tilapia (Oreochromis niloticus)

The present study was conducted to evaluate the effects of dietary nano-nutrients on the growth, physiological and amino acid responses in tilapia fish. Vitamins were incorporated with chemically synthesized nanoparticles (Fe, Zn, Cu and Se) to form a nano-nutrient complex (NNC). Powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) analyses were performed to confirm the structure and morphology of the as-prepared nutrients. A commercial basal diet without the addition of any NNC was used as a control and compared with the other two diets formulated with different levels of NNC. In a 60 day feeding trial, the fish fed with a diet of NNC60 showed significant differences in final weight and length compared with the basal diet. Furthermore, a high value of nutrient content was observed in the muscles of fish fed with nano diets. In addition, protein, total fat, vitamin C, and essential amino acid levels were significantly higher in the NNC60-treated fish compared with the other groups. The present study suggests that the addition of NNC to a commercial diet has the potential to enhance the growth performance and biochemical parameters in tilapia fish.

Detection of xanthine in food samples with an electrochemical biosensor based on PEDOT:PSS and functionalized gold nanoparticles

An innovative biosensor assembly relying on glassy carbon electrodes modified with nanocomposites consisting of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a host matrix with functionalized gold nanoparticles (GCE/PEDOT:PSS-AuNPs) is presented for the selective and sensitive detection of xanthine (XA). The developed sensor was successfully applied for the quantification of XA in the presence of significant interferents like hypoxanthine (HXA) and uric acid (UA). Different spectroscopy and electron microscopy analyses were done to characterize the as-prepared nanocomposite. Calibration responses for the quantification of XA was linear from 5.0 × 10⁻⁸ to 1.0 × 10⁻⁵ M (R² = 0.994), with a detection limit as low as 3.0 × 10⁻⁸ (S/N = 3). Finally, the proposed sensor was applied for the analyses of XA content in commercial fish and meat samples and satisfactory recovery percentage was obtained.

An innovative biosensor with glassy carbon electrodes modified with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate nanocomposites as a host matrix with functionalized gold nanoparticles for the selective and sensitive detection of xanthine.

Au-PDA@SiO2 core-shell nanospheres decorated rGO modified electrode for electrochemical sensing of cefotaxime

In this work, we have successfully synthesized core-shell structured Au-PDA@SiO2 nanospheres and decorated on reduced graphene oxide (rGO) modified glassy carbon electrode for the electrochemical detection of cefotaxime. The one-pot hydrothermal method was used to synthesis core-shell nanostructures by loading Au nanoparticles on polydopamine (PDA) coated SiO2 nanospheres. The as-prepared Au-PDA@SiO2 nanospheres were used to fabricate electrochemically reduced graphene oxide (rGO) modified glassy carbon electrode (Au-PDA@SiO2/rGO/GCE) for electrochemical determination of cefotaxime. Scanning electron microscopy, powder x-ray diffraction, transmission electron microscopy, and Fourier-transform infrared spectroscopy were used to confirm the structure and morphology of the as-prepared nanospheres. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed for electrochemical characterizations different modified electrodes. It was revealed that the nanocomposite modified electrodes exhibited excellent electrochemical performances for electrooxidation of target analytes and could achieve ultra-sensitive detections. A linear relationship was observed between peak currents and concentrations in the ranges of 1.0 × 10-9 to 5.0 × 10-8 M (R2 = 0.9877), and 1.0 × 10-7 to 5.0 × 10-6 M (R2 = 0.9821) for cefotaxime with a detection limit (S/N = 3) of 1.0 × 10-10 M. It can be deduced that the proposed sensor is suitable for the sensitive detection of cefotaxime in pharmaceutical samples.

Rapidly screening of α-glucosidase inhibitors from Dioscorea opposita Thunb. peel based on rGO@Fe3O4 nanocomposites microreactor

Present study aimed to immobilise the α-glucosidase on suitable supports to construct enzymatic microreactors and their subsequent applicability in efficient inhibitor screening from the Chinese Yam (Dioscorea opposita Thunb.) peel. A type of lamellar and porous composites (rGO@Fe3O4) were synthesised with a facile one-step solvothermal method and employed as carriers to construct enzymatic microreactors for screening α-glucosidase ligand from the Chinese Yam peel in league with the high performance liquid chromatography and mass spectrometry (HPLC-MS). The immobilisation amount of α-glucosidase on rGO@Fe3O4 under the optimised conditions was about 40 μg α-glucosidase/mg carriers. Furthermore, the binding capacities of screened inhibitors, 2,4-dimethoxy-6,7-dihydroxyphenanthrene and batatasin I, were 35.6 and 68.2%, respectively. Hence, considering their high screening efficiency and excellent magnetic separation ability, these as-prepared nanocomposite consisting of rGO and Fe3O4 may be potential supports for the enzyme (such as α-glucosidase) immobilisation for rapid α-glucosidase inhibitors screening from the diverse nature resources.

Investigation of the interaction of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase using inhibition kinetics, CD, FT-IR and molecular docking methods

Applying enzyme kinetics, spectroscopic, and molecular docking methods, the interaction properties of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase were systematically investigated. The α-glucosidase inhibitory activities (IC₅₀ = 0.40 mM) were significantly higher than that of acarbose (as control) and the spectrometric results revealed that 2,4-dimethoxy-6,7-dihydroxyphenanthrene inhibited α-glucosidase in a reversible and noncompetitive manner, which is that the inhibitor bind to the inactive region of α-glucosidase and could be separated from the bind sites. Hydrogen bond was the key interaction force obtained from the results of the molecular docking study, and the binding energy was -27.754 kJ/mol. The CD studies showed that the content of α-helix in α-glucosidase increased from 17.2% to 17.8% with the concentration varying of 2,4-dimethoxy-6,7-dihydroxyphenanthrene. The α-helix increasing trend (19.70% - 21.43%) of α-glucosidase secondary structure was further proved by Fourier transform infrared spectra (FT-IR) results and the FT-IR spectra of α-glucosidase resulted in obvious red shift with the addition of 2,4-dimethoxy-6,7-dihydroxyphenanthrene. All the measurements proved the interaction of 2,4-dimethoxy-6,7-dihydroxyphenanthrene with α-glucosidase and revealed the conformational change of α-glucosidase secondary structure.