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Consumption of water contaminated with pathogenic bacteria is a major cause of water-borne diseases. To address this challenge, we have developed a novel and sensitive sensing scheme for the rapid detection of bacteria (Escherichia coli B40) on a fiber-optic platform using bacteriophage (T4) as a bio-recognition element. The novelty of our sensing scheme is that instead of bacteriophages, bacteria (analyte) were first captured on the sensing surface and then the sensing surface was subjected to bacteriophages for specific detection of bacteria. The sensor was subjected to 100 to 107 cfu/mL of E. coli B40 spiked in a lake water matrix, and the least concentration of bacteria that could be easily detected was found to be 1000 cfu/mL. The control studies were performed with nonhost bacteria Pseudomonas aeruginosa. Bacteriophage T4, being specific to its host E. coli B40, did not interact with P. aeruginosa captured on the sensing probe, giving a negligible nonspecific response. Due to the specificity of bacteriophages to its host bacteria, it is possible to use this scheme to carry out the detection of specific bacteria in a mixed sample (containing a combination of bacteria) using bacteriophages specific to it. The sensor was able to detect E. coli B40 (target bacteria) even in the presence of a very high concentration (1000 times higher) of P. aeruginosa (nontarget bacteria).

This paper presents a hybrid pattern recognition with temperature compensation (HPR-TC) used within an E-Nose system. HPR-TC with E-nose has the novelty, amongst MEMS sensor platforms, of having two modes of operation i.e., rapid mode of detection to be used in time-critical conditions and comprehensive analysis mode for improved detection accuracy. Two modes of operations in HPR-TC are possible because of the implementation of hybrid PR featuring a combination of two different data analysis techniques for explosive sensing. The first part of the hybrid PR is the binary PR based on threshold-based detection and the second one is the analog PR based on PCA and K-mean. The E-Nose system with proposed HPR-TC is validated with two different highly sensitive MEMS sensor types, i.e., SU8 and Si3Nx piezo-resistive cantilever. These MEMS sensors are coated with surface receptors, 4-MBA, 6-MNA and 4-ATP, to improve the selectivity. The E-Nose system can detect explosive compounds such as TNT, RDX, and PETN, in a controlled environment at a concentration as low as 16ppb of TNT, 56ppb of RDX and 134ppb of PETN. Furthermore, measurements show that E-Nose with temperature compensated binary PR can detect the explosives with a detection accuracy higher than 74% as true positives and higher than 79% as true negatives in a short time, within initial 17 seconds of the experiment. However, the temperature compensated analog PR gives a detailed classification of explosives with a higher detection accuracy of 80% as true positives and 86% as true negatives after approximately 95 seconds.

Artificially ripened mango is harmful for health due to generation of some toxic chemicals. An electrochemical biosensor based on a molecularly imprinted polymer (MIP) was prepared for identifying artificial ripening of mango through its biomarker Furaneol (FU). Furaneol is found disappear on exposure to acetylene during artificial ripening. Methacrylic acid (MAA) copolymerized with ethylene glycol dimethacrylate (EGDMA) was utilized in developing FU imprinted sensor. The response characteristics of the sensor were evaluated by measuring the current response to FU with sensitivity factor of 0.017 A/M with wide detection range. The sensor response found to be highly selective to FU irrespective of other interfering analytes. The limit of detection of the graphite based poly-MAA imprinted Furaneol (PMAA-FU/G) sensor is 11 nM with wide linear detection range of $0.5~\mu \text{M}$ – $500~\mu \text{M}$ . Further the sensor was applied to natural and acetylene treated mangoes and compared with GC-MS data. The sensor is very successful with high recovery and sensitivity.

Large-scale purification of monoclonal antibodies using Protein A affinity chromatography continues to be one of the dominant processes in the production of biopharmaceuticals. In order to reduce the processing cost, ensure the purity of the product, and enable safe resin reuse, it is important to (a) estimate the quality of these resins, and (b) quantify the process-related impurities. This article presents the possibility of using a sensitive, rugged optical system as a process analysis tool for the assessment of resin fouling by quantification of the impurities like Protein A, host cell proteins (HCPs), and histones present in the elute. We have developed a conducting polymer-coated fiber optic sensor to detect these impurities, a flow cell to bypass the column elute directly toward the sensor, and associated electronics to make it a portable device for onsite applications. Protein A impurities (3 to 100 ng/mL) have been measured in pure buffer samples, while HCPs (100 to 350 ng/mL) and histone impurities (5 ng/mL to $1~\mu \text{g}$ /mL approximately) were detected in composite elute samples. In comparison to enzyme linked immunosorbent assay (ELISA)-based techniques, this low-cost, user-friendly sensing device demonstrates fast detection and high sensitivity for real-time monitoring of all process-related impurities.

Detection of bacterial colonies in water is a pressing issue in recent times owing to its implications on human health, leading to an urgent need for low cost, disposable sensors. In this work, we report a disposable impedimetric sensor for detection of total bacterial colonies present in water samples. The sensor consists of a polyaniline coated filter paper functionalized with a homo-bi functional crosslinker, glutaraldehyde. Prior to the functionalization step, two Ag electrodes are deposited on the filter paper using conductive silver paste. The aldehyde groups of glutaraldehyde bind with the amine functional groups present on bacterial cell wall resulting in a change in dielectric constant, and consequently, the capacitive effect between the two Ag electrodes. Also, bacterial metabolism affects the medium conductivity and in turn, the medium resistance changes. The combined effect of changes in capacitive effect as well as resistance is reflected as a change in AC impedance measured using a frequency response analyzer (FRA). E. coli and Pseudomonas aeruginosa bacteria are detected in PBS buffer up to ~ 500 cfu/mL. Testing is also carried out by spiking tap water and grey water with known concentrations of bacteria samples. The detection limits obtained are 500 – 1000 cfu/mL with a response time of ~ 20 minutes. The developed sensor provides rapid, moderately sensitive, cost-effective solution for detecting total bacterial load in water samples.

This paper presents E-Nose, a novel cost-effective, field-deployable portable system that constitutes a 4-channel signal conditioning circuit and multi-coated piezo-resistive micro-cantilever sensors for explosive sensing. E-Nose also features an embedded PCA and K-means based pattern recognition (PR) algorithm for the classification of explosives from non-explosives. The 4-channel configuration is a stack of two 2-channel circuits that are capable of measuring the change in the sensor resistance or capacitance in four optional modes of $\Delta \text{R}$ - $\Delta $ R, $\Delta \text{R}$ - $\Delta \text{C}$ , $\Delta $ C- $\Delta \text{R}$ , and $\Delta \text{C}$ - $\Delta \text{C}$ by using time multiplexing. The circuit uses a bidirectional AC current excitation method to drive the sensor bridge for significant reduction of DC offset errors, 1/f noise, line noise, and DC drifts. The proposed signal conditioning circuit uses the phase-sensitive synchronous rectification (PSSR) method for AC-to-DC conversion by using balanced demodulation. The circuit can measure a wide range of resistors that range from $100~\Omega $ to 4 $\text{M}\Omega $ , with a sensitivity of 0.4mV/ppm and the worst relative error of 2.6%. The capacitive measurement range is from 100pF to $100~\mu \text{F}$ with the worst relative error of 3.3%. The entire data processing and the PR algorithms run on Raspberry Pi (R-Pi), which is integrated into the E-Nose system. The system performance is tested with MEMS cantilevers for the detection of explosive compounds, such as TNT and its derivatives, RDX and PETN in a controlled environment at a concentration that was as low as 16ppb TNT, 56ppb RDX and 134ppb of PETN. Measurements show that the E-Nose can detect explosives with 77% as true positive results without considering the environmental and mixed vapor effects.

An aminosilane-based surface functionalization strategy was adopted to immobilize silver nanoparticles (AgNPs) on to silica materials to minimize leaching of silver into the aqueous environment. The disinfection potential and silver release of immobilized-AgNPs and chloridized silver surfaces were investigated for simulated lake water under varying water chemistry conditions. While the presence of both hardness and natural organic matter (NOM) adversely affected the disinfection kinetics and silver release from immobilized-AgNPs, alkalinity had only minor impact on disinfection performance over the concentration range 30–600 mg L−1. The higher disinfection efficacy of immobilized-AgNPs was ascribed to their contact-killing mechanism of action. In contrast, chloridized Ag that caused disinfection through the release of silver ions showed lower disinfection efficacy. Divalent cations and NOM greatly influenced the surface characteristics and morphology of the immobilized-AgNPs. However, immobilized AgNPs were more shielded than colloidal AgNPs when exposed to similar harsh conditions characterized by high hardness and NOM concentration. Under all the tested conditions, where 100% disinfection was achieved, the amount of silver release from immobilized AgNPs was less than 22 µg L−1, which is well below the USEPA permissible limit. The disinfection kinetics of immobilized-AgNPs was best fitted by the Hom model (R2 = 0.974), where its lumped parameters kh and m were found to vary with variation in background water quality. Sensitivity analyses indicated that for ‘m’ value higher than 1.9, complete disinfection could not be achieved regardless of many fold increase in ‘kh’ value.

Mercury is a diversely bioaccumulating heavy metal pollutant toxic to all life forms. In this work, an optical biosensor has been developed and calibrated for universal detection and quantification of mercuric ions, in the range 0.1–540 parts per billion, in biological and environmental samples. Chitosan capped gold nanoparticles on bovine serum albumin are proposed as an ultrasensitive plasmonic mercury receptor on U-bend optical fiber platform. The sensor was calibrated and tested with tap water, sewage contaminated water, marine water, long lived sea fish tissue, fossil fuel fly ash contaminated soil and vegetable samples. The sensor performance was validated with real samples inherently containing mercury. Overall standard error of less than 15% and a coefficient of variation less than 12% (n = 3) was found across all samples, indicating good fitness for diverse usage. Experimentally determined limit of detection of mercuric ions was 0.1 parts per billion in tap water (twenty times lesser than the Environment protection agency limit of 2 parts per billion in drinking water) and 0.2 parts per billion in sea fish and vegetable samples with negligible cross sensitivity towards other metal ions.

Heavy metal contamination of water bodies has an adverse effect on human health and the environment even at very low concentrations. In this paper, we report U-shaped fiber optic probe coated with glucose capped silver nanoparticles (AgNPs) for label-free detection of mercury ions in aqueous solution. The reaction between glucose capped AgNPs and mercury ions resulted in a reduction in the plasmonic absorbance. The developed sensor probe was able to detect mercury ions concentration as low as 2 ppb, which is less than the World Health Organization acceptable limit for mercury ions in drinking water. The sensor probes displayed excellent selectivity towards mercury ions over other metal ions. Furthermore, the developed sensor probe was able to detect mercury ions down to 5 ppb in domestic tap water, i.e., selective detection of mercury even in real matrix having high concentration mixtures of various essential ions. The response of AgNPs coated sensor probe was found to be better than glucose capped gold nanoparticles and hollow gold-silver nanostructures coated fiber-optic probes.

A vegetable mustard (MUS) oil based quartz crystal microbalance (QCM) sensor has been developed to detect Ocimene (OCM), one of the significant flavor enhancing compounds in mango. After testing with all the vegetables oils, MUS oil is found to be the most efficient with sensitivity factor of 0.276 Hz/ppm with satisfactory repeatability and reproducibility. The sensor exhibits a linear range of concentration (1–1000 ppm) with limit of detection of 1.04 ppm.The sensor is demonstrable in detecting the intended OCM with high selectivity from other dominant flavors involved in mango. The sensor can be used upto three months with minimum drift in frequency. Additionally, sensor response shows a good congruence with the GC–MS data with a correlation factor of 0.96. Further, the response of MUS-QCM sensor to the real mango samples has been found to be verifiable for quality assessment of most popular mango varieties viz. Alphonso, Gulabkhas, and Himsagar.

Rapid and sustained disinfection of surfaces is necessary to check the spread of pathogenic microbes. The current study proposes a method of synthesis and use of copper nanoparticles (CuNPs) for contact disinfection of pathogenic microorganisms. Polyphenol stabilized CuNPs were synthesized by successive reductive disassembly and reassembly of copper phenolic complexes. Morphological and compositional characterization by transmission electron microscope (TEM), selected area diffraction and electron energy loss spectroscopy revealed monodispersed spherical (ϕ5-8 nm) CuNPs with coexisting Cu, Cu(I) and Cu (II) phases. Various commercial grade porous and non-porous substrates, such as, glass, stainless steel, cloth, plastic and silk were coated with the nanoparticles. Complete disinfection of 107copies of surrogate enveloped and non-enveloped viruses: bacteriophage MS2, SUSP2, phi6; and gram negative as well as gram positive bacteria:Escherichia coliandStaphylococcus aureuswas achieved on most substrates within minutes. Structural cell damage was further analytically confirmed by TEM. The formulation was well retained on woven cloth surfaces even after repeated washing, thereby revealing its promising potential for use in biosafe clothing. In the face of the current pandemic, the nanomaterials developed are also of commercial utility as an eco-friendly, mass producible alternative to bleach and alcohol based public space sanitizers used today.

Consumption of water contaminated with pathogenic bacteria is a major cause of water-borne diseases. To address this challenge, we have developed a novel and sensitive sensing scheme for the rapid detection of bacteria (

This study explored the application of colloidal and immobilized silver nanoparticles (AgNPs) for inactivation of bacteriophages. Coliphages that are commonly used as indicators for enteric viruses, were used in this study. Colloidal AgNPs were synthesized via a chemical reduction approach using sodium borohydride as reducing agent and trisodium citrate as stabilizing agent. AgNP-immobilized glass substrate was prepared by immobilizing AgNPs on amine-functionalized glass substrate by post-immobilization method. The AgNP-immobilized glass substrate was also tested so as to minimize the release of AgNPs in the treated water. The characterization of AgNPs and the AgNP-immobilized glass surface was done using field emission gun-transmission electron microscopy and scanning electron microscopy. Studies conducted with varying concentrations of colloidal AgNPs displayed good antiviral activity for MS2 and T4 bacteriophage. Colloidal AgNPs at a dose of 60μg ml−1could completely inactivate MS2 and T4 bacteriophage within 30 and 50 min with an initial concentration of 103PFU ml−1. Contaminated water (100 ml) in an unstirred batch reactor with an initial bacteriophage concentration of 103PFU ml−1could be inactivated by the AgNP-immobilized glass substrate (1 cm × 1 cm, containing 3.7μg cm−2silver) suspended centrally in the batch reactor. Complete 3-Log bacteriophage inactivation was achieved within 70 and 80 min for MS2 and T4 bacteriophage, respectively, while the aqueous silver concentration was less than 25μg l−1. This is significantly lower than the recommended standard for silver in drinking water (i.e. 100μg l−1, US EPA). Thus, AgNP-immobilized glass may have good potential for generating virus-free drinking water.

The size and shape of silver nanoparticles (AgNPs) can potentially influence their antibacterial activity. In this study, a photochemical approach was adopted for the synthesis of decahedral AgNPs and their antibacterial activity was tested and compared against that of spherical AgNPs of similar size synthesized using the chemical reduction approach. The UV–vis spectra indicated the synthesis of decahedral AgNPs with a localized surface plasmon resonance (LSPR) peak at 502 nm. The spherical AgNPs exhibited the LSPR peak at 416 nm. Analysis of field emission gun-transmission electron microscopy (FEG-TEM) micrographs demonstrated the average diameter of decahedral silver nanoparticles as 52.1 ± 5.7 nm with side length as 33.2 ± 3.1 nm. In contrast, the average size of spherical AgNPs was 44.2 ± 6.3 nm. The decahedral AgNPs demonstrated ten times higher bactericidal activity as compared to the spherical AgNPs across all the bacterial strains tested. The minimum inhibitory concentration (MIC) for decahedral AgNPs was in the range of 4–8 μg/ml for all the four bacterial strains tested, whereas, for spherical nanoparticles of comparable size, the MIC was in the range of 40–80 μg/ml. The minimum bactericidal concentration (MBC) for decahedral AgNPs was in the range of 6–10 μg/ml. At the same time, spherical AgNPs of comparable size exhibited MBC in the range of 60–100 μg/ml for the four bacterial strains. In terms of bactericidal effect, Escherichia coli MTCC 443 was found as the most sensitive strain, while in terms of growth inhibition, Bacillus subtilis was the most sensitive strain. Staphylococcus aureus NCIM 5021 was the most resistant among the tested bacterial strains.

β-Lactam antibiotics such as penicillins and cephalosporins are extensively used for human infection therapy. Consistent unintended exposure to these antibiotics via food and water is known to promote antibiotic-resistant bacterial pathogenesis with high morbidity and mortality in humans. An optical enzymatic biosensor for rapid and point-of-use detection of these antibiotics in food and water has been developed and tested. Enzymatic hydrolysis of β-lactams, on the electroactive polyaniline nanofibers, altered the polymeric backbone of the nanofibers, from emeraldine base form to emeraldine salt, which was measured as an increase in evanescent wave absorbance at 435 nm. The sensors were calibrated by spiking antibiotic-free milk with ceftazidime (as a model β-lactam analyte) in a linear range of 0.36−3600 nM (R2 = 0.98). The calibration was further validated for packaged milk, local cow milk, and buffalo milk. A similar calibration was devised for chicken meat samples in a linear range of 9−1800 nM (R2 = 0.982) and tap water in a linear range of 0.18−180 nM (R2 = 0.99). Interestingly, it was possible to use the same calibration for the determination of other β-lactam antibiotics (ampicillin, amoxicillin, and cefotaxime), which reflects the usefulness of the sensor for wide-scale deployment. The sensor performance was validated with a wastewater sample, from a wastewater treatment plant (WWTP), qualitatively analyzed by high-resolution liquid chromatography coupled with mass spectroscopy for detection of β-lactams. The sensor scheme developed and tested is of grassroot relevance as a quick solution for measurement of β-lactam residues in food and environment.

The response time of the fiber-optic immunosensor is diffusion-limited. A frequency- modulated vibration setup has been designed. For 15 Hz frequency, the initial response time and 75% saturation time improved by ~80% and ~40%, respectively.

In the present study, E.coli B40 bacteria were explored as possible receptors on localized surface plasmon resonance (LSPR) based biosensor for sensing heavy metal ions viz. mercury (Hg2+) and cadmium (Cd2+) in water. The E.coli B40 bacteria were immobilized on gold nanoparticles (AuNP) coated fiber-optic probes by depositing two bi-layers of oppositely charged polyelectrolytes. The E.coli immobilized sensor probes were subjected to different concentrations of Hg2+ and Cd2+ ions, ranging from 0.5 ppb to 2000 ppb. These metal ions interact with the thiols and other surface groups present on the bacterial cells, resulting in the change of refractive index around AuNP coated sensor probes, thereby modulating the sensor response. The detection was performed by spiking de-ionized (DI) water and tap water with metal ions and the limit of detection was found to be 0.5 ppb. The proposed sensor could detect heavy metal ions within 10 min from a small sample (

Novel U-shaped, polymer optical waveguides are demonstrated as localized surface plasmon resonance (LSPR) based sensors for various biosensing applications. Commercially available materials like polyester overhead projector sheets (OHP), poly (methyl methacrylate) (PMMA) and acrylonitrile butadiene styrene (ABS) were effectively deployed as core materials for fabrication of optical waveguides, due to their malleability and excellent combination of optical and mechanical properties. Single-step fabrication of waveguides has been achieved using simple tools like 3D printer and laser cutting technology, rather than utilizing moulds or clean room facilities. Resilient and repeatable bio-functionalization of waveguides with successful immobilizing of gold nanoparticles (GNP) was obtained on the waveguide surface. The sensor response for each of the fabricated polymer waveguides was characterized by evaluating the bulk refractive index (RI) sensitivity. Highest refractive index sensitivity of 14.79 ΔA/RIU was obtained for GNP immobilized PMMA waveguides. A biosensing application using an affinity based labelled assay was demonstrated on PMMA waveguides. Limit of detection (LOD) of 0.25 μg/mL was achieved with a non-specific response of only 5.3%. The proposed LSPR based polymer optical waveguide sensor is inexpensive, robust and provides a platform for point of care detection system.

Background: This paper examines the suitability of extant governance frameworks at an international level for addressing antimicrobial resistance (AMR), which is a creeping crisis for global health security. Methods: Our study begins by evaluating the place of antimicrobial resistance (AMR) within United Nations (UN) Sustainable Development Goals (SDG) targets and indicators. This is followed by a discussion of the global health security agenda (GHSA). We examine how AMR needs to be taken more seriously within global policy frameworks based on adopting a One Health approach. The research is supported by a systematic analysis of the national action plans for addressing AMR published by the World Health Organisation (WHO). Results: We determine that political leaders need to do more to promote the problem of AMR and that global health institutions need to invest more energy in thinking about how AMR is governed as part of an already busy global health security agenda. This includes building capacities within health systems, embedding evaluation processes, and enhancing public service leadership within this area. Conclusions: Our review of global policy frameworks and the national plans for AMR highlight the patchy coverage of AMR strategies globally and nationally. This article represents a springboard for future research including whether and to what extent a One Health approach to AMR in the environment has been implemented in practice within national health and environmental systems.

A comparative life cycle assessment of CO2 capture potential of microalgae, Scenedesmus dimorphus, during autotrophic cultivation in closed airlift photobioreactor and open raceway pond under Indian conditions has been carried out. The LCA inventory inputs for the both the systems were entirely based on primary experimental data obtained by algal cultivation in 1000-L pilot-scale raceway pond and 5-L airlift photobioreactor, respectively. The primary energy demand, environmental impacts and Net CO2 capture efficiency of both the systems were evaluated. The results indicated that the primary energy demand and GWP of airlift photobioreactor were 3.7-fold higher than raceway pond. The NERCO2 (defined as net emission ratio of CO2 and estimated as ratio of CO2 sequestered/CO2 emitted) of raceway pond was fourfold higher as compared to airlift photobioreactor; however, both the cultivation systems were observed to be net negative in terms of CO2 sequestration. However, the process can become net CO2 positive, with up to fourfold and 7.5-fold enhancement in biomass productivities (wrt base value) for raceway pond and airlift photobioreactor, respectively. Further, LCA predictions indicated that utilization of energy-efficient motors with lower specific energy consumptions for microalgae cultivation would facilitate algal cultivation systems to achieve net CO2-positive sequestration.