Sarani Sen

Bio: Sarani Sen is an academic researcher from University of Calcutta. The author has contributed to research in topics: Materials science & Cyclic voltammetry. The author has an hindex of 3, co-authored 5 publications receiving 36 citations.

A novel third-generation xanthine biosensor with enzyme modified glassy carbon electrode using electrodeposited MWCNT and nanogold polymer composite film

Abstract: A novel nanobiocomposite for immobilization of xanthine oxidase (XO) was developed by incorporating functionalized MWCNT in nanogold doped poly(o-phenylenediamine) (PPD) (Au–PPD) film on glassy carbon electrode (GCE) for selective and sensitive detection of xanthine in real samples e.g. blood, urine, fish. Stable colloid of o-phenylenediamine (OPD) and HAuCl4 in acidic environment was electropolymerized on working electrode (GCE) to form an ultrathin film of AuNP–PPD which possessed permselectivity and no interference against electroactive species such as ascorbic acid and uric acid. Spectrophotometric and microscopic analysis confirmed the doping behaviour of AuNP. Electrodeposition of carboxylated MWCNT onto the Au–PPD film increased conductivity, sensitivity and also facilitated a microenvironment to entrap XO enzyme by covalent bonding, enhancing storage stability. The conductive nature of the electrode after every step of modification was investigated by electrochemical impedance spectroscopy. High Imax/Kmap value was achieved by the XO/fMWCNT/Au–PPD modified electrode. Oxidation of xanthine on this modified electrode was diffusion-controlled involving two electrons in the rate-determining step with a transfer coefficient (α) of about 0.596. Differential pulse voltammetric study of XO/fMWCNT/Au–PPD/GCE exhibited good analytical characteristics e.g. low detection limit (12 nM) (S/N = 3), a wide linear range of 0.01–300 μM (R2 = 0.994), good sensitivity (14.03 μA μM−1 cm−2), fast response (6 s) at anodic potential of +0.625 V vs. Ag/AgCl (pH 7.0). It retained 91% of its initial activity even after 210 times of use over a period of 4 months when stored at 4 °C. The applicability of the xanthine biosensor was tested by performing reproducibility, repeatability and interference study on real samples.

A new diagnostic tool for measuring total antioxidants in tea

Abstract: The purpose of this research was to develop a sensory system to measure antioxidant level in tea with a view to assessing the quality of different grades of tea available in the market. We proposed an easy, reliable sensory system to quantify the total antioxidant capacity (TAC) of tea infusion. A preformed ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate)] radical cation (ABTS(+)) was used in the bulk electrolyte in presence of glassy carbon (GC) or platinum (Pt) working electrode. Total antioxidant present in sample was determined by amperometric response at optimum redox potential of 0.552 V dictated by cyclic voltammogram. Linear calibrations for standard antioxidants such as gallic acid, caffeic acid, ascorbic acid, catechin hydrate and chlorogenic acid were obtained in the range of 1-250 mu g/mL. Quantitative estimation of antioxidants in tea samples were expressed as gallic acid equivalent (GAE) with a detection limit of 2.34 mu g/mL. The amperometric sensor showed optimum response at pH 5.8 at around 25 degrees C. Excellent correlations were obtained with standard spectrophotometric assays. The system might be useful for quality control of various grades of tea due to its specificity, simplicity and quick response of measurement procedures. The present research gave excellent opportunity to grade tea on the basis of antioxidant levels. Similarly the system might have useful applications in determining antioxidants in other common food items such as fruit juices and other beverages.

A Double‐Stimuli‐Responsive Fluorescent Center for Monitoring of Food Spoilage based on Dye Covalently Modified EuMOFs: From Sensory Hydrogels to Logic Devices

Abstract: Unsafe food is a huge threat to human health and the economy, and detecting food spoilage early is an ongoing and imperative need. Herein, a simple and effective strategy combining a fluorescence sensor and one-to-two logic operation is designed for monitoring biogenic amines, indicators of food spoilage. Sensors (methyl red@lanthanide metal-organic frameworks (MR@EuMOFs)) are created by covalently modifying MR into NH2 -rich EuMOFs, which have a high quantum yield (48%). A double-stimuli-responsive fluorescence center is produced via energy transfer from the ligands to Eu3+ and MR. Portable sensory hydrogels are obtained by dispersing and solidifying MR@EuMOFs in water-phase sodium salt of carboxy methyl cellulose (CMC-Na). The hydrogels exhibit a color transition upon "smelling" histamine (HI) vapor. This transition and shift in the MR-based emission peak are closely related to the HI concentration. Using the HI concentration as the input signal and the two fluorescence emissions as output signals, an advanced analytical device based on a one-to-two logic gate is constructed. The four output combinations, NOT (0, 1), YES (1, 0), PASS 1 (1, 1), and PASS 0 (0, 0), allow the direct analysis of HI levels, which can be used for real-time food-freshness evaluation. The novel strategy suggested here may be a new application for a molecular logic system in the sensing field.

Visual monitoring of food spoilage based on hydrolysis-induced silver metallization of Au nanorods

Abstract: Colorimetric detection of biogenic amines, well-known indicators of food spoilage, plays an important role for monitoring of food safety. However, common colorimetric sensors for biogenic amines suffer from low color resolution or complicated design and intricate output for the end-users. Herein, we explored a simple but effective strategy for visual monitoring of biogenic amines with multiple color change based on hydrolysis-induced silver metallization reaction to tune the localized surface plasmon resonance (LSPR) adsorption of Au nanorods (NRs). The color change and blue shift of longitudinal LSPR peak of Au NRs were closely related to the concentration of biogenic amines. This strategy provided a simple, sensitive, robust, nondestructive, cost-effective, and user-friendly platform for in situ evaluating the freshness of foodstuffs.

Recent progress in nanomaterial-based electrochemical and optical sensors for hypoxanthine and xanthine. A review

Abstract: This review (with 160 ref.) summarizes the progress that has been made in the methods for chemical or biochemical sensing of hypoxanthine and xanthine, which are produced as part of purine metabolism and are precursors of uric acid. An introduction discusses the importance of hypoxanthine and xanthine as analytes due to their significance in the clinical and food science, together with the conventional methods of analysis. A large section covers methods for the electrochemical hypoxanthine and xanthine sensing. It is divided into subsections according to the nanomaterials used including carbon nanomaterials, meal oxide nanoparticles, metal organic frameworks, conductive polymers, and bio-nanocomposites. A further large section covers optical methods for hypoxanthine and xanthine sensing, with subsections on nanomaterials including carbon nanomaterials, nanosheets, nanoclusters, nanoparticles, and their bio-nanocomposites. A concluding section summarizes the current status, addresses current challenges, and discusses future perspectives. Graphical abstractSchematic representation of the hypoxanthine and xanthine electrochemical and optical sensors incorporating various nanomaterials like graphene, carbon nanotubes (CNT), quantum dots (QD), nanoparticles and polymers, which are implemented in clinical and food analysis.