A polylactic acid-carbon nanofiber-based electro-conductive sensing material and paper-based colorimetric sensor for detection of nitrates.

Plastics are ubiquitous in today's lifestyle, and their indiscriminate use has led to the accumulation of plastic waste in landfills and oceans. The waste accumulates and breaks into micro-particles that enter the food chain, causing severe threats to human health, wildlife, and the ecosystem. Environment-friendly and bio-based degradable materials offer a sustainable alternative to the vastly used synthetic materials. Here, a polylactic acid and carbon nanofiber-based membrane and a paper-based colorimetric sensor have been developed. The membrane had a surface area of 3.02 m2 g-1 and a pore size of 18.77 nm. The pores were evenly distributed with a pore volume of 0.0137 cm3 g-1. The membrane was evaluated in accordance with OECD guidelines and was found to be safe for tested aquatic and terrestrial models. The activated PLA-CNF membrane was further used as a bio-based electrode for the electrochemical detection of nitrates (NO3-) in water samples with a detection limit of 0.046 ppm and sensitivity of 1.69 × 10-4 A ppm-1 mm-2, whereas the developed paper-based colorimetric sensor had a detection limit of 156 ppm for NO3-. This study presents an environment-friendly, low-carbon footprint disposable material for sensing applications as a sustainable alternative to plastics.

A paper-based chromogenic strip and electrochemical sensor for the detection of 4-(dimethylamino)azobenzene.

Natural and synthetic dyes are added to different food commodities to enhance their appearance and acceptance by consumers. Acute and chronic exposure owing to the consumption of non-permitted dyes may lead to health concerns such as allergic reactions, eczema, and asthma. 4-(Dimethylamino)azobenzene (4-DMAAB) is a non-permitted dye that has been reported in adulterated mustard oil. Consumption of 4-DMAAB poses severe risks due to its mutagenic and carcinogenic properties. Several sensitive methods such as FT-NIR, FT-MIR and SERS are available for the detection of 4-DMAAB. Here, a spectrophotometric method was developed for the detection of 4-DMAAB. The developed method was translated to a point-of-test paper-based, chromogenic strip which showed a detection limit of 0.025 mM for 4-DMAAB. Also, an electrochemical sensor was developed by electro-depositing the test solution on a screen-printed electrode. The electrochemical sensor showed an LOD of 0.027 ± 0.008 mM with recovery in the range of 91-107% of 4-DMAAB. Oil samples collected from the market were processed by liquid-liquid extraction and the content of 4-DMAAB was assessed. The developed point-of-use sensors for the detection of 4-DMAAB have potential for use by the consumers, food industry and regulatory agencies for on-site analysis and assuring the quality of edible oils.

A QR code-integrated chromogenic paper strip for detection of hydrogen peroxide in aqueous samples.

Hydrogen peroxide (H2O2) is commonly used as a preservative, disinfectant, bleach, and oxidizing agent. The prolonged consumption of H2O2 adulterated milk is harmful to human health when consumed in the diet. Exposure to H2O2 can lead to oxidative stress, cell damage and tissue injury. Due to the potential adverse effects, the use of hydrogen peroxide is regulated in certain applications, such as in food, water treatment plants and medical products. Several methods are available for the detection of H2O2 in various matrices. Here, a method and QR code-integrated chromogenic paper strip for the detection of H2O2 in aqueous samples has been developed. The spectrophotometric method showed an LOD and LOQ of 0.00087 ± 8.70 ×10-5% (v/v) and 0.0037 ± 0.0003% (v/v), respectively. The paper-based chromogenic strip prepared by immobilizing recognition solution onto a QR code was able to detect 0.0005% v/v of H2O2 in aqueous samples. The QR integrated chromogenic paper strip sensors can serve as a useful tool for consumers, regulatory agencies, and the food industry to assess food quality and authenticity.

Chitosan-carbon nanofiber based disposable bioelectrode for electrochemical detection of oxytocin.

Bioelectrodes with low carbon footprint can provide an innovative solution to the surmounting levels of e-waste. Biodegradable polymers offer green and sustainable alternatives to synthetic materials. Here, a chitosan-carbon nanofiber (CNF) based membrane has been developed and functionalized for electrochemical sensing application. The surface characterization of the membrane revealed crystalline structure with uniform particle distribution, and surface area of 25.52 m2/g and pore volume of 0.0233 cm3/g. The membrane was functionalized to develop a bioelectrode for the detection of exogenous oxytocin in milk. Electrochemical impedance spectroscopy was employed to determine oxytocin in a linear concentration range of 10 to 105 ng/mL. The developed bioelectrode showed an LOD of 24.98 ± 11.37 pg/mL and sensitivity of 2.77 × 10-10 Ω / log ng mL-1/mm2 for oxytocin in milk samples with 90.85-113.34 percent recovery. The chitosan-CNF membrane is ecologically safe and opens new avenues for environment-friendly disposable materials for sensing applications.

Polylactic acid/tapioca starch/banana peel-based material for colorimetric and electrochemical biosensing applications.

The rapidly growing electronic and plastic waste has become a global environmental concern. Developing advanced and environmentally safe agro-based materials is an emerging field with an enormous potential for applications in sensors and devices. Here, an agro-based material as membrane has been developed by incorporating tapioca starch and banana peel powder in polylactic acid, with uniform dispersibility and amorphous nature. The material was used for the development of electrochemical sensor for S-gene of SARS-CoV-2. Further, the membrane was used for the development of a non-invasive, colorimetric skin patch for the detection of glucose and a sensor for the assessment of fruit juice quality. Using OECD-recommended model systems, the developed membrane was found to be non-toxic towards aquatic and terrestrial non-target organisms. The developed conductive material opens new avenues in various electrochemical, analytical, and biological applications.

Sensor-integrated biocomposite membrane for food quality assessment.

The use of biopolymers is gaining momentum owing to their compatibility with various food commodities and acceptability by the industry and consumers. Biopolymers integrated with natural pigments can be used for assessing the quality of perishable packaged food products. Here, a biodegradable composite membrane of starch and chitosan, integrated with anthocyanin has been developed. The chromogenic response of the developed biocomposite membrane was used to assess spoilage in milk. The surface roughness recorded using atomic force microscopy and scanning electron microscopy showed smooth membrane surface, and a pore size 4.21 nm was determined by Brunauer-Emmett-Teller analysis. The water vapour transmissibility of the membrane was 4.616E-09 and 1.147E-08 g/h Pa.mm and water solubility was 5.6 and 5.8 % at 25 and 37 ℃, respectively, indicating high water resistance and low vapour transmission rate. The developed biocomposite membrane offers an environment friendly substrate for biosensing with a promising potential in smart food-packaging applications.

Development and Clinical Validation of RT-LAMP-Based Lateral-Flow Devices and Electrochemical Sensor for Detecting Multigene Targets in SARS-CoV-2.

Consistently emerging variants and the life-threatening consequences of SARS-CoV-2 have prompted worldwide concern about human health, necessitating rapid and accurate point-of-care diagnostics to limit the spread of COVID-19. Still, However, the availability of such diagnostics for COVID-19 remains a major rate-limiting factor in containing the outbreaks. Apart from the conventional reverse transcription polymerase chain reaction, loop-mediated isothermal amplification-based (LAMP) assays have emerged as rapid and efficient systems to detect COVID-19. The present study aims to develop RT-LAMP-based assay system for detecting multiple targets in N, ORF1ab, E, and S genes of the SARS-CoV-2 genome, where the end-products were quantified using spectrophotometry, paper-based lateral-flow devices, and electrochemical sensors. The spectrophotometric method shows a LOD of 10 agµL-1 for N, ORF1ab, E genes and 100 agµL-1 for S gene in SARS-CoV-2. The developed lateral-flow devices showed an LOD of 10 agµL-1 for all four gene targets in SARS-CoV-2. An electrochemical sensor developed for N-gene showed an LOD and E-strip sensitivity of log 1.79 ± 0.427 pgµL-1 and log 0.067 µA/pg µL-1/mm2, respectively. The developed assay systems were validated with the clinical samples from COVID-19 outbreaks in 2020 and 2021. This multigene target approach can effectively detect emerging COVID-19 variants using combination of various analytical techniques at testing facilities and in point-of-care settings.

Challenges in assessing the quality of fruit juices: Intervening role of biosensors.

The quality of packaged fruit juices is affected during their processing, packaging and storage that might cause deteriorative biological, chemical and physical alterations. Consumption of spoiled juices, either from biological or non-biological sources can pose a potential health hazard for the consumers. Sensitive and reliable methods are required to ensure the quality of fruit juices. Standard analytical methods such as chromatography, spectrophotometry, electrophoresis and titration, that require sophisticated equipment and expertise, are traditionally used to assess the quality of fruit juices. Using biosensors, that are simple, portable and rapid presents a promising alternative to the tedious analytical methods for the detection of various degradation and spoilage indicators formed in the packaged fruit juices. Here, we review the challenges in maintaining the quality of fruit juices and the recent developments in techniques and biosensors for quick analysis of fruit juice components.

A quick and simple paper-based method for detection of furfural and 5-hydroxymethylfurfural in beverages and fruit juices.

Improper storage and transportation of non-alcoholic beverages can, over longer periods, induce Maillard reaction, degrading nutritional components and generating genotoxic and carcinogenic by-products such as furfural and 5-hydroxymethylfurfural (HMF), rendering products unsafe for human consumption. Here, we describe a rapid quantitative solution-based method and test-strips for detection of furfural and HMF. The standard spectroscopic method indicated an LOD of 0.006 ±â€¯0.003% (v/v) and 0.005 ±â€¯0.002% (v/v) for furfural and HMF, respectively in fruit juice samples. The novel chromogenic test-strip has sensitivity of 0.008% (v/v) and 0.004% (v/v) for furfural and HMF, respectively in the same samples of fruit juice. Thus, the developed method and test-strips were specific for furfural and HMF and can be used to help ensure food safety and quality in various industrial applications.

Recent advances in the sustainable design and applications of biodegradable polymers.

The progression of plastic pollution is a global concern. "Reuse, reduce and recycle" offers a solution to the burdening issue, although not enough to curb the rampant use of plastics. Biodegradable plastics are gaining acceptability in agriculture and food packaging industries; nevertheless, they occupy a rather small section of the plastic market. This review summarizes recent advances in the development of biodegradable plastics and their safe degradation potentials. Here, biodegradable plastics have been categorized and technology and developments in the field of biopolymers, their applicability, degradation and role in sustainable development has been reviewed. Also, the use of natural polymers with improved mechanical and physical properties that brings them at par with their counterparts has been discussed. Biodegradable polymers add value to the industries that would help in achieving sustainable development and consequently reinforce green economy, reducing the burden of greenhouse gases in the environment and valorisation of waste biomass.