Chetna Dhand

Recent advances in polyaniline based biosensors.

The present paper contains a detailed overview of recent advances relating to polyaniline (PANI) as a transducer material for biosensor applications. This conducting polymer provides enormous opportunities for binding biomolecules, tuning their bio-catalytic properties, rapid electron transfer and direct communication to produce a range of analytical signals and new analytical applications. Merging the specific nature of different biomolecules (enzymes, nucleic acids, antibodies, etc.) and the key properties of this modern conducting matrix, possible biosensor designs and their biosensing characteristics have been discussed. Efforts have been made to discuss and explore various characteristics of PANI responsible for direct electron transfer leading towards fabrication of mediator-less biosensors.

Methods and strategies for the synthesis of diverse nanoparticles and their applications: a comprehensive overview

Ongoing advances in nanotechnology research have established a variety of methods to synthesize nanoparticles (NPs) from a diverse range of materials, including metals, semiconductors, ceramics, metal oxides, polymers, etc. Depending upon their origin and synthesis methods, NPs possess unique physicochemical, structural and morphological characteristics, which are important in a wide variety of applications concomitant to electronic, optoelectronic, optical, electrochemical, environment and biomedical fields. This review provides a comprehensive overview on various physical, chemical and bio-assisted methods largely employed to synthesize and fabricate NPs of varying size, surface characteristics, functionalities and physicochemical behavior. The key applications of nanoparticles have also been discussed.

Electrophoretic fabrication of chitosan-zirconium-oxide nanobiocomposite platform for nucleic acid detection.

The present work describes electrophoretic fabrication of nanostructured chitosan-zirconium-oxide composite (CHIT-NanoZrO(2)) film (180 nm) onto indium-tin-oxide (ITO)-coated glass plate. This nanobiocomposite film has been explored as immobilization platform for probe DNA specific to M. Tuberculosis as model biomolecule to investigate its sensing characteristics. It is revealed that pH-responsive behavior of CHIT and its cationic skeleton is responsible for the movement of CHIT-NanoZrO(2) colloids toward cathode during electrophoretic deposition. The FT-IR, SEM, TEM, and EDX techniques have been employed for the structural, morphological, and composition analysis of the fabricated electrodes. The morphological studies clearly reveal uniform inter-linking and dispersion of hexagonal nanograins of ZrO(2) (30-50 nm) into the chitosan matrix, resulting in homogeneous nanobiocomposite formation. Electrochemical response measurements of DNA/CHIT-NanoZrO(2)/ITO bioelectrode, carried out using cyclic voltammetry and differential pulse voltammetry, reveal that this bioelectrode can specifically detect complementary target DNA up to 0.00078 μM with sensitivity of 6.38 × 10(-6) AμM(-1).

Molecularly imprinted polyaniline film for ascorbic acid detection.

Molecularly imprinted polyaniline (PANI) film (∼100 nm thick) has been electrochemically fabricated onto indium–tin–oxide (ITO) coated glass plate using ascorbic acid (AA) as template molecule. Fourier transform infra‐red spectroscopy, scanning electron microscopy, cyclic voltammetry and differential pulse voltammetry (DPV) studies indicate the presence of AA in PANI matrix, which also acts as a dopant for PANI. Further, the AA selective molecularly imprinted PANI electrode (AA‐MI‐PANI/ITO) has been developed via over‐oxidation of AA doped PANI electrode which leads to the removal of AA moieties from PANI film. The response studies using DPV technique have revealed that this molecularly imprinted AA‐MI‐PANI/ITO electrode can detect AA in the range of 0.05–0.4 mM with detection limit of 0.018 mM and sensitivity of 1.2 × 10−5 AmM−1. Interestingly, this AA‐MI‐PANI/ITO electrode shows excellent reusability, selectivity and stability. Copyright

Bio-inspired in situ crosslinking and mineralization of electrospun collagen scaffolds for bone tissue engineering.

Bone disorders are the most common cause of severe long term pain and physical disability, and affect millions of people around the world. In the present study, we report bio-inspired preparation of bone-like composite structures by electrospinning of collagen containing catecholamines and Ca(2+). The presence of divalent cation induces simultaneous partial oxidative polymerization of catecholamines and crosslinking of collagen nanofibers, thus producing mats that are mechanically robust and confer photoluminescence properties. Subsequent mineralization of the mats by ammonium carbonate leads to complete oxidative polymerization of catecholamines and precipitation of amorphous CaCO3. The collagen composite scaffolds display outstanding mechanical properties with Youngs modulus approaching the limits of cancellous bone. Biological studies demonstrate that human fetal osteoblasts seeded on to the composite scaffolds display enhanced cell adhesion, penetration, proliferation, differentiation and osteogenic expression of osteocalcin, osteopontin and bone matrix protein when compared to pristine collagen or tissue culture plates. Among the two catecholamines, mats containing norepinephrine displayed superior mechanical, photoluminescence and biological properties than mats loaded with dopamine. These smart multifunctional scaffolds could potentially be utilized to repair and regenerate bone defects and injuries.

Polyaniline/carbon nanotubes platform for sexually transmitted disease detection.

Polyaniline/carbon nanotubes composite (PANI‐CNT) electrochemically deposited onto indium‐tin‐oxide (ITO) coated glass plate has been utilized for Neisseria gonorrhoeae detection by immobilizing 5′‐amino‐labeled Neisseria gonorrhoeae probe (aDNA) using glutaraldehyde as a cross‐linker. PANI‐CNT/ITO and aDNA‐Glu‐PANI‐CNT/ITO electrodes have been characterized using scanning electron microscopy (SEM), Fourier Transform Infrared (FT‐IR) spectroscopy, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). This bioelectrode can be used to detect N. gonorrhoeae using methylene blue (MB) as redox indicator with response time of 60 s and stability of about 75 days when stored under refrigerated conditions. DPV studies reveal that this bioelectrode can detect complementary DNA concentration from 1 × 10−6 M to 1 × 10−17 M with detection limit of 1.2 × 10−17 M. Further, this bioelectrode (aDNA‐Glu‐PANI‐CNT/ITO) exhibits specificity toward N. gonorrhoeae species and shows negative response with non‐Neisseria gonorrhoeae Neisseria species (NgNS) and other gram negative bacteria (GNB). Copyright

Molecularly imprinted polyaniline-polyvinyl sulphonic acid composite based sensor for para-nitrophenol detection

We report results of the studies relating to the fabrication and characterization of a conducting polymer based molecularly imprinted para-nitrophenol (PNP) sensor. A water pollutant, para-nitrophenol is electrochemically imprinted with polyvinyl sulphonic acid (PVSA) doped polyaniline onto indium tin oxide (ITO) glass substrate. This PNP imprinted electrode (PNPI-PANI-PVSA/ITO) prepared via chronopotentiometric polymerization and over-oxidation is characterized by Fourier transform infra-red spectroscopy (FT-IR), UV-visible (UV-vis) spectroscopy, contact angle (CA), scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies. The response studies of PNPI-PANI-PVSA/ITO electrode carried out using DPV reveal a lower detection limit of 1×10(-3) mM, improved sensitivity as 1.5×10(-3) A mM(-1) and stability of 45 days. The PNPI-PANI-PVSA/ITO electrode shows good precision with relative standard deviation of 2.1% and good reproducibility with standard deviation of 3.78%.

Zirconia grafted carbon nanotubes based biosensor for M. Tuberculosis detection

Zirconia (ZrO2) grafted multiwalled carbon nanotubes (CNTs) (crystallite size of ZrO2 ∼ 28.63 nm), obtained via isothermal hydrolysis of zirconium oxychloride in presence of CNT, have been electrophoretically deposited onto indium-tin-oxide (ITO) coated glass plate. High resolution electron microscopic investigations reveal assemblage of the ZrO2 nanostructure inside and around CNT cavities. Electrochemical impedance spectroscopic studies indicate ∼3.5 fold enhancement in charge transfer behaviour of NanoZrO2-CNT/ITO electrode compared to that of NanoZrO2/ITO electrode. Considering the synergy between biocompatible ZrO2 and electrochemically superior CNT, this nanobiocomposite has been explored to develop an impedimetric nucleic acid biosensor for M. Tuberculosis detection.

Multifunctional Polyphenols- and Catecholamines-Based Self-Defensive Films for Health Care Applications

In an era of relentless evolution of antimicrobial resistance, there is an increasing demand for the development of efficient antimicrobial coatings or surfaces for food, biomedical, and industrial applications. This study reports the laccase-catalyzed room-temperature synthesis of mechanically robust, thermally stable, broad spectrum antimicrobial films employing interfacial interactions between poly(vinyl alcohol), PVA, and 14 naturally occurring catecholamines and polyphenols. The oxidative products of catecholamines and polyphenols reinforce the PVA films and also alter their surface and bulk properties. Among the catecholamines-reinforced films, optimum surface and bulk properties can be achieved by the oxidative products of epinephrine. For polyphenols, structure-property correlation reveals an increase in surface roughness and elasticity of PVA films with increasing number of phenolic groups in the precursors. Interestingly, PVA films reinforced with oxidized/polymerized products of pyrogallol (PG) and epinephrine (EP) display potent antimicrobial activity against pathogenic Gram-positive and Gram-negative strains, whereas hydroquinone (HQ)-reinforced PVA films display excellent antimicrobial properties against Gram-positive bacteria only. We further demonstrate that HQ and PG films retain their antimicrobial efficacy after steam sterilization. With an increasing trend of giving value to natural and renewable resources, our results have the potential as durable self-defensive antimicrobial surfaces/films for advanced healthcare and industrial applications.

Insight into membrane selectivity of linear and branched polyethylenimines and their potential as biocides for advanced wound dressings.

UNLABELLED We report here structure-property relationship between linear and branched polyethylene imines by examining their antimicrobial activities against wide range of pathogens. Both the polymers target the cytoplasmic membrane of bacteria and yeasts, eliciting rapid microbicidal properties. Using multiscale molecular dynamic simulations, we showed that, in both fully or partially protonated forms LPEI discriminates between mammalian and bacterial model membranes whereas BPEI lacks selectivity for both the model membranes. Simulation results suggest that LPEI forms weak complex with the zwitterionic lipids whereas the side chain amino groups of BPEI sequester the zwitterionic lipids by forming tight complex. Consistent with these observations, label-free cell impedance measurements, cell viability assays and high content analysis indicate that BPEI is cytotoxic to human epithelial and fibroblasts cells. Crosslinking of BPEI onto electrospun gelatin mats attenuate the cytotoxicity for fibroblasts while retaining the antimicrobial activity against Gram-positive and yeasts strains. PEI crosslinked gelatin mats elicit bactericidal activity by contact-mediated killing and durable to leaching for 7days. The potent antimicrobial activity combined with enhanced selectivity of the crosslinked ES gelatin mats would expand the arsenel of biocides in the management of superficial skin infections. The contact-mediated microbicidal properties may avert antimicrobial resistance and expand the diversity of applications to prevent microbial contamination. STATEMENT OF SIGNIFICANCE Current commercially available advanced wound dressings are either impregnated with metallic silver or silver salts which have side effects or may not avert antimicrobial resistance. In this article, we have used multidisciplinary approach comprising of computational, chemical and biological methods to understand the antimicrobial properties and biocompatibility of linear (LPEI) and branched (BPEI) polyethylenimines. We then applied this knowledge to develop dual purpose wound dressings containing these polymers, which encourages healing while maintain antimicrobial activity. In addition, the approach can be expanded to rationalize the antimicrobial vs. cytotoxicity of other cationic polymers and the method of crosslinking would enhance their potentials as biocides for advanced materials.