Ashok Raichur

Indian Institute of Science | IISC · Department of Materials Engineering

Dielectric properties for nanocomposites with metallic fillers inside a polymer matrix were determined using CST STUDIO SUITE—Electromagnetic field simulation software followed by the free-space Nicolson–Ross–Weir procedure. The structure is randomly generated to simulate the intrinsic non-uniformity of real nanomaterials. Cubic insertions were equ...

The current study explores the synergistic effect of graphene oxide and nano & hollow silica particle composite as a reinforcing agent for improved mechanical and thermal properties of tetrafunctional epoxy nanocomposites. The unique architecture of the reinforcing agent prevents the agglomeration of graphene oxide sheets during the drying process...

In this work, improved fracture toughness of tetra-functional epoxy polymer was obtained using two-dimensional (2H polytype) molybdenum disulfide (MoS2) nano-platelets as a filler. Simultaneous in-situ exfoliation and functionalization of MoS2 were achieved in the presence of cetyltrimethylammonium bromide (CTAB) via sonication. The aim was to impr...

High-performance epoxy composites find application in the aerospace industry. Although epoxy is a high-performance polymer, its fracture toughness is compromised due to its highly cross-linked nature. Nanomaterials such as carbon nanotubes (CNTs), graphene derivatives, and inorganic 2-dimensional (2D) nanomaterials are being explored to improve epo...

Introduction: SARS-CoV-2 has fatally affected the whole world with millions of deaths. Amidst the dilemma of a breakthrough in vaccine development, hydroxychloroquine (HCQ) was looked upon as a prospective repurposed candidate. It has confronted numerous controversies in the past few months as a chemoprophylactic and treatment option for COVID-19....

Epoxy is a high performance yet brittle thermosetting resin. To deem epoxy fit for aircraft applications, its mechanical properties, especially fracture toughness, must be improved. In this work, epoxy resin was reinforced with 0.1, 0.5 and 1.0 wt.% polystyrene-graphene oxide (PS-GO) core-shell nano-particles to enhance its fracture toughness. Styr...

In the present work, we designed mesoporous silica nanoparticles (MSNs) capped with chitosan-glucuronic acid (CHS-GCA) conjugate for pH-responsive targeted delivery of 5-fluorouracil (5-FU). The influence of the synthesis parameters on the shape and particle size of the MSNs was investigated. The size and morphology of the MSNs were found to be dep...

Antimicrobial materials with enhanced mechanical and thermal properties must be developed for innovative applications in medicine, food and packaging, etc. This study presents ionic liquid-assisted fabrication of graphene oxide, silver nanoparticles and poly (vinyl alcohol) based composite films (PVA/Ag/GO-IL) for antibacterial applications. The mo...

2D materials such as graphene oxide and molybdenum sulfide exhibit certain properties such as photoluminescence, photothermal and photodynamic effects that have potential in diagnosing and treating cancer. However, their application is limited by low cellular uptake of the sheet-like structure. In this study, we present a facile route for convertin...

Un-doped and nitrogen (N) doped titanium dioxide (TiO 2) nano-particles (NPs) were synthesized by the sol-gel method at room temperature (RT) using titanium tetra-isopropoxide as the precursor material of TiO 2. The TiO 2 and N-TiO 2 NPs were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), FTIR...

Un-doped and nitrogen (N) doped titanium dioxide (TiO 2) nano-particles (NPs) were synthesized by the sol-gel method at room temperature (RT) using titanium tetra-isopropoxide as the precursor material of TiO 2. The TiO 2 and N-TiO 2 NPs were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), FTIR...

The mechanical and thermal properties of epoxy composites were improved by using poly (allyl amine) (PAA) grafted graphene oxide (GO) as a toughening agent. The GO was first converted to GO-COOH where all the hydroxyl groups on the basal plane were converted to COOH containing groups. GO-COOH was reacted with PAA to yield GO-g-PAA. The effect of PA...

Chitosan derived from chitin is one of the most abundant naturally occurring biocompatible polymers obtained from fungi and arthropods. In this work, we report the enhancement in the bactericidal efficacy of CHI in the presence of a sharp nanotopography. High-aspect ratio nanostructured surface (NSS) was fabricated using a single-step deep reactive...

In the present study, fluoride removal from drinking water is investigated using layer-by-layer (LbL) fabricated poly(sodium 4-styrene-sulfonate) (PSS)/Al2O3 thin films. The surface morphology of the fabricated thin films is characterized using atomic force microscopy and field emission-scanning electron microscopy. Optical profilometry is used to...

Detection of foodborne contaminants is essential before they are released into the market. We have developed simple colorimetric detection methods for contaminants like melamine, malathion, and foodborne pathogens, like Escherichia coli O157:H7 in food items using silver and gold-based nanoparticles. The detection of these contaminants is principal...

Highly tuneable architecture of PEMs with nanometres precision is the most promising aspect to utilize them for variety of applications. The bulk loading properties of polyelectrolyte multilayer thin films (PEM) motivate researchers to utilize them as a carrier for biomedical applications. For designing an efficient carrier polymeric assembly for t...

The synergistic relationship between structure and the bulk properties of polyelectrolyte multilayer (PEM) films has generated tremendous interest in their application for loading and release of bioactive species. Layer-by-layer (LbL) assembly is the simplest, cost effective process for fabrication of such polyelectrolyte multilayers (PEM) films, l...

The bulk properties of polyelectrolyte multilayer thin films (PEM) are the key to make them a potential candidate for the applications like biosensing, drug delivery and tissue engineering applications. For all these biomedical applications, the location or availability and release of encapsulated molecules are defined by their ability to diffuse t...

In the present study, noncovalently functionalized tungsten disulfide (WS2) nanosheets were used as toughening agent for epoxy nanocomposites. WS2 was modified with branched polyethyleneimine (PEI) to increase the degree of interaction of nanosheets with epoxy matrix, prevent restacking and agglomeration of the sheets in the epoxy matrix. The funct...

Arginine decorated nanocarriers exhibited intravacuolar targeting capability which was utilized to deliver antibiotics into the intracellular niche of pathogens like Salmonella and Mycobacterium. The arginine based nanocarrier system (Arg-MSN) was developed on a mesoporous silica nanoparticle (MSN) template by conjugating L-arginine to protamine an...

The present study deals with the toxicity assessment of two differently synthesized zero valent iron nanoparticles (nZVI, chemical and biological) as well as Fe2+ ions on Artemia salina at three different initial concentrations of 1, 10 and 100 mg/L of these particles. The assessment was done till 96h at time intervals of 24h. EC50 value was calcul...

Iron nanoparticles (NPs) of size less than 20nm were synthesized using an in-house developed cryomill. These NPs exhibit values of saturation magnetisation (~180 emu/gm) close to that of pure iron. The particles were found to be nontoxic at concentrations required for MRI imaging as indicated by MTT assay. In vivo studies demonstrated the suitabili...

A comparative study on detection of melamine with different sized citrate capped AuNPs namely 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) was carried out by fluorescence spectroscopy. The AuNPs emitted strong fluorescence at 421 nm with different intensity at 116.122, 220.511 and 253.665 for AuNPs-I, AuNPs-II and AuNPs-III respectively...

In recent years, nanoparticles (NPs) based on biopolymers or peptides are gaining popularity for the encapsulation and release of drug molecules, especially for cancer therapy, due to their ability for targeted and controlled release. The use of collagen peptide (CP) for the preparation of chitosan (CN) NPs is especially interesting as it results i...

Layer by layer (LbL) technique was employed to modify the surface of doxorubicin (Dox) loaded bovine serum albumin (BSA) nanoparticles using hyaluronic acid (HA) to enable targeted delivery to over expressed CD44 receptors in metastatic breast cancer cells. LbL technique offers a versatile approach to modify the surface of colloidal nanoparticles w...

In the present study, a suitable carrier system was developed for the delivery of dsRNA into Penaeus monodon (P. monodon) post larvae to silence the Monodon baculovirus (MBV) structural gene of p74. The carrier system was developed by layer by layer adsorption of oppositely charged chitosan-dextran sulfate, on charged silica nanoparticles. The sili...

Gold nanoparticles (GNPs) of different sizes were used to carry out comparative fluorometric detection study on endotoxin. At excitation wavelength, 308 nm the GNPs exhibited strong emission intensity at wavelength 421 nm with varying intensities at 215.122, 234.965 and 262.551 for 15 nm (GNPs-I), 30 nm (GNPs-II) and 40 nm (GNPs-III), respectively....

The measurement of molecular transport within polymer films yields information about the internal structural organization of the films and is useful in applications such as the design of polymeric capsules for drug delivery. Layer-by-Layer assembly of polyelectrolyte multilayer films has been widely used in such applications where the multilayer st...

We report an efficient and a simple synergistic antimicrobial therapy for lysing pathogenic E. coli K12 MG1655 using layer-by-layer (LbL) films of graphene oxide (GO) and poly(allylamine hydrochloride) (PAH). Two kinds of antimicrobial therapies have been tested in this study. The first therapy involves the inherent antimicrobial property of GO stu...

Investigation of the interactions between graphene oxide (GO) and biomolecules is very crucial for the development of biomedical applications based on GO. This study reports the first observation of the spontaneous formation of self-assembled liquid crystals and three-dimensional hydrogels of graphene oxide with double-stranded DNA by simple mixing...

Chemotherapy is the gold standard strategy for effective treatment of cancer. Polymer drug delivery technology involving conjugations of therapeutics such as polymer–drug conjugations, polymer–protein conjugations, lipid–drug conjugations, ligand–drug conjugations, or antibody–drug conjugations have been studied extensively. Polysaccharides includi...

A simple rapid method was developed using gold nanorods for the colorimetric detection of lipopolysaccharide extracted from the generic strain, E. coli K12, which was used as a surrogate for the pathogenic strain, E. coli O157:H7. The principle is based on the aggregation of the cetyltrimethylammonium bromide-capped gold nanorods in the presence of...

Porous CaCO3 microparticles have been used earlier for sustained drug release of hydrophilic drugs but have certain drawbacks for use with hydrophobic drugs. Hence, to overcome these drawbacks, a novel composite of CaCO3 along with cyclodextrin (CD-CaCO3) for the delivery of hydrophobic drugs was developed. Cyclodextrins (CDs), when incorporated wi...

Iron nanoparticles (NPs) of size less than 20 nm were synthesized using an in-house developed cryomill. These NPs exhibit values of saturation magnetisation (∼180 emu g⁻¹) close to that of pure iron. The particles were found to be nontoxic at concentrations required for MRI imaging as indicated by MTT assay. In vivo studies demonstrated the suitabi...

Titania nanoparticles were successfully supported on carbon-covered alumina (CCA) supports via the impregnation method to form carbon-covered alumna titania (CCA/TiO 2 ). The CCA supports were synthesised through an equilibrium adsorption of toluene 2,4-diisocyante where the N=C=O irreversibly adsorbs on the alumina and pyrolysis at 700°C affords C...

Enzyme- and pH-responsive polyelectrolyte nanocapsules having diameters in the range of 200 ± 20 nm were fabricated by means of Layer-by-Layer assembly of biopolymers, protamine, and heparin, and then loaded with anticancer drug doxorubicin. The incorporation of the FDA-approved peptide drug protamine as a wall component rendered the capsules respo...

Polyelectrolyte multilayer (PEM) thin film composed of weak polyelectrolytes was designed by layer-by-layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) for multi-drug delivery applications. Environmental stimuli such as pH and ionic strength showed significant influence in changing the film morphology fro...

A novel and highly sensitive sensing strategy for detection of organophosphorus compounds (OPs) based on the catalytic reaction of acetylcholinesterase (AChE) and acetylcholine (ATCh) during the modulated synthesis of silver nanoparticles (AgNPs) has been developed. The enzymatic hydrolysis of ATCh by AChE yields thiocholine (TCh), which induces th...

Layer-by-layer assembly of polyelectrolytes, is a simple technique based on the self-assembly of polycations and polyanions by electrostatic interaction, which has gained considerable scientific interest for its versatility of applications. Ease of fabrication process, inexpensive approach and use to coat surfaces with various geometries enables re...

Two antineoplastic agents, Imatinib (IM) and 5-Fluorouracil (FU) were conjugated by hydrolysable linkers through an amide bond and entrapped in polymeric Human Serum Albumin (HSA) nanoparticles. The presence of dual drugs in a common carrier has the advantage of reaching the site of action simultaneously and acting at different phases of the cell c...

Thin films of zinc ferrite (ZnFe 2 O 4 ) were deposited on glass, quartz and p-silicon (100) substrates by the sol-gel method. The structural properties of the films were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD data show the film having a spinel structure and the crystalli...

Thin films of zinc ferrite (ZnFe 2O4) were deposited on glass, quartz and p-silicon (100) substrates by the sol-gel method. The structural properties of the films were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD data show the film having a spinel structure and the crystalline...

This work proposes the fabrication of a novel targeted drug delivery system based on mesoporous silica-biopolymer hybrids that can release drugs in response to biological stimuli present in cancer cells. The proposed system utilizes mesoporous silica nanoparticles as a carrier to host the drug molecules. A bio-polymer cap is attached onto these par...

In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwate...

Multidrug resistance is a major therapeutic challenge faced in the conventional chemotherapy. Nanocarriers are beneficial in the transport of chemotherapeutics by their ability to bypass the P-gp efflux in cancers. Most of the P-gp inhibitors under Phase II clinical trial are facing failures and hence there is a need to develop a suitable carrier t...

Zinc oxide (ZnO) thin films were prepared on p-silicon (100) substrates by the sol-gel technique using zinc acetate dehydrate as a precursor material with and without surfactant. The films were heat treated by microwave-assisted method and annealed at various temperatures in ambient air. Different nano-structures were obtained by the varying anneal...

The effect of TiO2 (5, 10 and 15 mg) nano-particles on optical, electrical and mechanical properties of Poly (vinyl alcohol) (PVA) films were reported. The un-doped PVA films showed high transmittance in the visible region, however with the increase of TiO2 doping the transmittance has decreased. The films with sandwich structures of the type Al-PV...

A simple colorimetric detection of melamine was studied using 15nm (AuNPs-I), 30nm (AuNPs-II), and 40 nm (AuNPs-III) sized citrate-capped gold nanoparticles (AuNPs). The AuNPs get aggregated in aqueous solution the presence of melamine, showing a visual color change from red to blue. This color change led to a shift in the peak from 527nm, 526nm an...

Lipid coated mesoporous silica nanoparticle (L-MSN) were synthesized for oral delivery of ciprofloxacin for intracellular elimination of Salmonella pathogen. The particle size was found to be between 50-100 nm with a lipid coat of approximately 5 nm thickness. The lipid coating was achieved by sonication of liposomes with the MSN particles and eval...

Titanium dioxide (TiO2) thin films were deposited on glass and silicon (100) substrates by the sol–gel method. The influence of film thickness and annealing temperature on optical transmittance/reflectance of TiO2 films was studied. TiO2 films were used to fabricate metal–oxide–semiconductor capacitors. The capacitance–voltage (C–V), dissipation–vo...

There is a persistent need to assess the effects of TiO2 nanoparticles on the aquatic ecosystem owing to their increasing usage in consumer products and risk of environmental release. The current study is focused on TiO2 nanoparticle-induced acute toxicity at sub-ppm level (≤1ppm) on the three different freshwater sediment bacterial isolates and th...

We report the fabrication of a dual enzyme responsive hollow nanocapsule which can be targeted to deliver anticancer agents specifically inside cancer cells. The enzyme responsive elements integrated in the nanocapsule walls can undergo degradation in presence of either of the enzymes trypsin or hyaluronidase leading to the release of encapsulated...

Saccharomyces boulardii was encapsulated by layer-by-layer technique (LbL) using oppositely charged polyelectrolytes, chitosan and dextran sulfate to protect from degradation during its gastrointestinal transit. The protective effect of the coating was evaluated by checking viability after subjecting the coated cells to lyophilisation and simulated...

One of the most widely studied fields of research in recent decades is nanotechnology which involves the synthesis, manipulation and application of nanoparticles. Nanosystems have gained interest due to their distinctive properties which vary significantly as compared to the bulk material. Due to their unique properties, nanoparticles are used in a...

The fabrication of a mesoporous silica nanoparticle (MSN)−protamine hybrid system (MSN−PRM) is reported that selectively releases drugs in the presence of specific enzyme triggers present in the proximity of cancer cells. The enzyme trigger involved is a protease called trypsin, which is overexpressed in certain specific pathological conditions, su...

A novel approach towards the synthesis of hollow silver nanoparticle (NP) cages built with building blocks of silver NPs by layer-by-layer (LbL) assembly is demonstrated. The size of the NP cage depends on the size of template used for the LbL assembly. The microcages showed a uniform distribution of spherical silver nanoparticles with an average d...

The industrial production and commercial applications of titanium dioxide nanoparticles have increased considerably in recent times, which has increased the probability of environmental contamination with these agents and their adverse effects on living systems. This study was designed to assess the genotoxicity potential of TiO2 NPs at high exposu...

Titanium dioxide (TiO2) thin films were synthesized by the sol-gel method. The titanium (IV) isopropoxide and ethanol were used as precursor of TiO2 and solvent, respectively. The TiO2 sol was spin coated on glass substrates and pre-heated at 50°C for 15 min. The films were annealed at different temperatures for two hours in ambient air to obtain T...

We report a simple method to fabricate multifunctional polyelectrolyte thin films to load and deliver the therapeutic drugs. The multilayer thin films were assembled by the electrostatic adsorption of Poly (allylamine hydrochloride) (PAH) and Dextran sulfate (DS). The silver nanoparticles (Ag NPs) biosynthesized from novel Hybanthus enneaspermus le...

The emergence of multi-drug resistant bacteria is a global threat for human society. There exists recorded data that silver has been used as an antimicrobial agent by the ancient Greeks and Romans during 8(th) century. Silver nanoparticles (AgNPs) are of potential interest because of their effective antibacterial and antiviral activity, with minima...

Novel composite cyclodextrin (CD)-CaCO3 spherical porous microparticles have been synthesized through Ca2+-CD complex formation, which influences the crystal growth of CaCO3. The CDs are entrapped and distributed uniformly in the matrix of CaCO3 microparticles during crystallization. The hydrophobic fluorescent molecules coumarine and nile red (NR)...

Metal-doped anatase nanosized titania photocatalysts were successfully synthesized using a sol-gel process. Different amounts of the dopants (0.2, 0.4, 0.6, 0.8 and 1.0%) of the metals (Ag, Ni, Co and Pd) were utilized. The UV-Vis spectra (solid state diffuse reflectance spectra) of the doped nanoparticles exhibited a red shift in the absorption ed...