Development and Characterization of Curcumin Loaded Silver Nanoparticle Hydrogels for Antibacterial and Drug Delivery Applications

The present work involves the development of curcumin loaded silver hydrogel nanocomposites based on acrylamide and 2-acrylamido-2-methyl propanesulfonic acid, as a template by redox co-polymerization in the presence of hydrophilic crosslinker N,N ¹-methylenebisacrylamide. Silver nitrate was taken as the metal precursor and sodium borohydride as a reducing agent. The formation of silver nanoparticles was monitored using UV–Vis absorption spectroscopy. The developed hydrogel silver nanocomposites (HSNC) were characterized by FTIR, UV–Vis, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. The curcumin loading and release characteristics were performed for different hydrogel systems. The developed HSNCs were evaluated for preliminary antibacterial applications.     

Optical,morphological, electrical properties of ZnO-TiO2-SnO2/CeO2 semiconducting ternary nanocomposite

Low dielectric constant and low dielectric loss with moderate wide bandgap, novel semiconducting metal oxide composites are useful materials for applying optoelectronic, microwave dielectric ceramics. A less dielectric constant is required for wireless communication to reduce the cross pairing between conductors and also for fast signal transmission. In the present study, the structural, optical, and dielectric properties of ternary ZnO - TiO₂ added with SnO₂/CeO₂ semiconducting nanocomposite materials were investigated and synthesized by the solid-state gelation method. The samples were sintered at a temperature of 450 ⁰C. The X-ray diffraction patterns of composites revealed the existence of TiO₂ anatase phase, SnO_2, and CeO₂. The average crystallite size at d₁₀₁ was measured using the Scherer method, ranging from 6.18 nm to 9.13 nm. The overall crystallite size was calculated using the Size-strain plot method, and it is in the range of 14.8 nm to 17.16 nm. The surface morphology of all samples appears uniform in size and spherical shape. The average particle size of grains was 35 nm. The absorbance properties studied by UV–Visible spectroscopy and bandwidth were 2.6 eV calculated using Tauc’s plot method, and it reveals the formation of new energy levels. The dielectric properties of pellet dimensions of 1 mm thickness and 10 mm diameter, measured from the LCR meter, are indicated at 1 kHz frequency. The most significant dielectric constant (ε_r) and lowest loss tangent (Tan δ) are 53.89 and 0.25 for pure ZnO - TiO₂, and the lowest dielectric constant (ε_r) and less loss tangent (Tan δ) are 9.69 and 0.38 for 1 wt% CeO₂ doped to ZnO - TiO₂. The conductivity of the composite is in the range of 10^-7 S/cm. With additive concentration to ZnO - TiO₂, both SnO₂ and CeO₂ are equally potential and modifies the parameters due to the similar bandgaps and more oxygen availability.     

Hydrogel–silver nanoparticle composites: A new generation of antimicrobials

Design of consistant and eco‐friendly methods for the synthesis of silver nanoparticles (AgNPs) is a significant forward direction in the field of application of antibacterial bionanotechnology. One among the available options is hydrogel templates, which are highly useful to achieve this goal. This investigation involves the development of poly(acrylamide)/poly(vinyl alcohol) hydrogel–silver nanocomposites (HSNCs) to achieve AgNPs of ～2–3 nm size in gel networks. The nanocomposite synthesis process is quite convenient, direct, and very fast, and the obtained hydrogel AgNP composites can be used for antibacterial and wound dressing applications. All the nanocomposite aqueous solutions have shown absorption peaks at 420 nm in UV–visible absorption spectrum corresponding to the Plasmon absorbance of AgNPs. X‐ray diffraction spectrum of the HSNC exhibited 2θ values matching with silver nanocrystals. Transmission electron microscopy images of nanocomposites represent discrete AgNPs throughout the gel networks in the range of 2–3 nm. The developed nanocomposites were evaluated for antibacterial application on E. coli. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Design and development of temperature sensitive porous poly(NIPAAm‐AMPS) hydrogels for drug release of doxorubicin‐a cancer chemotherapy drug

Temperature sensitive polymer network porous hydrogels were developed with N‐Isopropylacrylamide (NIPAAm) and AMPS (2‐acrylamido‐2‐methyl‐1‐propanesulfonicacid), as well as with sucrose as porogen by crosslinking with hydrophilic crosslinker N,N¹‐methylenebisacrylamide (MBA). The temperature responsive behaviour, the swelling/deswelling kinetics of the hydrogels were investigated. The structural and morphological characterizations of the developed hydrogels were obtained from FTIR spectroscopy and scanning electron microscopy (SEM). The increment in the lower critical solution temperature (LCST) of NIPAAm hydrogels can be done with the help of AMPS and it is confirmed with differential scanning calorimetry (DSC) as well as temperature dependent swelling curves. The model cancer chemotherapy drug Doxorubicin (Dox) was loaded into theses hydrogels and the release studies as well as the released profiles of the drug showed that more than 8–54% of the loaded drug was released in the first half‐an‐hour at a buffer solution of 7.4 and the rest of the drug was released slowly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of magnetic nanoparticles embedded in hydrogels for protein purification and metal extraction

The present work involves the development of hydrogel magnetic nanocomposites for protein purification and heavy metal extraction applications. The magnetic nanoparticles (MNPs) were prepared in situ in poly(acrylamide)-gum acacia (PAM-GA) hydrogels. The formation of magnetic nanoparticles in the hydrogel networks was confirmed by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Scanning electron (SEM) microscopy studies revealed the formation of MNPs throughout the hydrogel networks. The average size of MNPs formed in the hydrogel networks was 3–5 nm as determined by transmission electron microscopy (TEM). The thermal properties of the hydrogel magnetic nanocomposites were evaluated by dynamic scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The magnetic properties of the developed hydrogel magnetic nanocomposites were determined by a vibrating sample magnetometer (VSM). The swelling properties of the hydrogel and the hydrogel magnetic nanocomposites were studied in detail. The hydrogel magnetic nanocomposites are utilized for the removal of toxic metal ions such as Co(II), Ni(II), and Cu(II) and for protein purification. The results confirm that the hydrogel magnetic nanocomposites exhibit superior extraction properties to hydrogels.     

Preparation of antibacterial temperature‐sensitive silver‐nanocomposite hydrogels from N‐isopropylacrylamide with green tea

This article reports the temperature‐sensitive, green tea (GT)‐based silver‐nanocomposite hydrogels for bacterial growth inactivation. The temperature‐sensitive hydrogels were prepared via free‐radical polymerization using temperature‐sensitive N‐isopropylacrylamide (NIPAM) monomer with GT as the hydrogel matrix. The nanocomposite hydrogels were encapsulated with silver ions via swelling method, which was later reduced to silver nanoparticles using Azadirachta indica leaf extract. The temperature‐sensitive silver nanocomposite hydrogels were analyzed by using Fourier transforms infrared, UV–visible spectroscopy, differential scanning calorimetry–thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The prepared hydrogels exhibited higher phase volume transition temperature than the NIPAM. The inhibition zone study of the inactivation of bacteria on the developed hydrogels was carried out against Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus), which revealed that the prepared hydrogels are helpful for the inactivation of these bacteria due to the high stabilization of antibacterial properties of the silver nanoparticles. The developed hydrogels are promising for biomedical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45739.     

Magnetic and electric responsive hydrogel–magnetic nanocomposites for drug‐delivery application

Magnetic and electrically responsive hydrogel networks were developed for drug‐delivery applications. The hydrogel matrices were synthesized by the polymerization of acrylamide monomer in the presence of carboxymethylcellulose (CMC) or methylcellulose (MC) with N,N‐methylenebisacrylamide, a crosslinker with the redox initiating system ammonium persulfate/tetramethylethylenediamine. The magnetic nanoparticles were generated throughout these hydrogel matrices by an in situ method by the incorporation of iron ions and their subsequent reduction with ammonia. A series of hydrogel–magnetic nanocomposites (HGMNCs) were developed with various CMC and MC compositions. The synthesized HGMNCs were characterized with spectral (Fourier transform infrared and ultraviolet–visible spectroscopy), X‐ray diffraction, thermal, and microscopy methods. These HGMNCs contained iron oxide (Fe₃O₄) nanoparticles with an average particle size of about 22 nm, as observed by transmission electron microscopy. The dielectrical properties of the pure hydrogel (HG); the hydrogel loaded with iron ions, or the hydrogel iron‐ion composite (HGIC); and the HGMNCs were measured. These results suggest that HGMNCs exhibited higher dielectric constants compared to HG and HGICs. The curcumin loading and release characteristics were also measured for HG, HGIC, and HGMNC systems. These data revealed that there was a sustained release of curcumin from HGMNCs because of the presence of magnetic nanoparticles in the hydrogel networks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

FORMATION OF CONTINUOUS PRECURSOR FIBERS FOR OXIDE-CERAMIC FIBERS: EXPERIMENTS IN POLYSOL-GEL ROUTES FOR SILICA FIBERS

Issues related to the formation of continuous precursor fibers for oxide ceramic fibers via polysol-gel routes are addressed through an experimental study of polysol-gel route to silica fibers. The emphasis is on integrating the requirements for forming stable, spinnable polysols with appropriate mechanisms for producing continuous precursor fibers. A pronounced change is shown to occur in the nature of the highly spinnable polysols produced through acid-catalyzed hydrolysis and potycondensation of tetraethylorthosilicate (TEOS) over a narrow range of water to TEOS concentration ratio. Solution-wet and solution-dry jet-wet spinning routes, with new catalyzed gelation/coagulation schemes, are shown to be viable options for continuous spinning from these polysols. The benefits of incorporating high molecular weight organic polymers and drying control chemical additives (DCCA) as aids for rheological and cohesive drying purposes are demonstrated through appropriate examples.     

Structural and dielectric studies of some niobate-titanate systems

Ferroelectric ceramics of the general formulax (Li_1/2 La_1/2 TiO₃) (1−x) (LiNbO₃) have been found to have tungsten bronze (TTB) and ilmenite type structure in the ranges 0·8≤x≤1·0 and 0≤x≤0·2 respectively. The system is biphasic in the other ranges. All single phase materials exhibit dielectric anomalies in the temperature range 300–600 K. The high dielectric constant of the TTB phase is explained as due to the existence of localised rotational excitons arising from a large number of defect structural units and their coupling with one of the low frequency lattice modes. Information about the lattice modes to which the rotational excitons are coupled has been obtained from Raman spectra. Deceased     

The effect of capping agents on the structural and magnetic properties of cobalt ferrite nanoparticles

Microwave-assisted co-precipitation method was adopted to analyze the effect of polyethylene glycol (PEG) and urea concentrations on the properties of cobalt ferrite nanoparticles (NPs). The average crystallite size of single phase cubic spinel cobalt ferrite NPs was controlled within 10–14 nm with the effect of PEG, urea and the combination of them. The transmission electron micrographs revealed that the morphology of cobalt ferrites was not significantly influenced by the different concentration of capping agents but almost uniform morphology with nearly narrow size distribution was obtained. The interaction of PEG and urea molecules on the surface of nanoparticles was mediated through –OH hydroxyl group affected the crystal growth rate. The possible interaction mechanism was proposed with the help of IR vibrational spectra. All the samples exhibited ferromagnetism at room temperature and it was found that the capping agents showed an effect on the magnetic properties. The maximum saturation magnetization of 58 emu/g was achieved when the urea of 60 mg was used and the maximum coercivity of 311 Oe was attained when the mixture of PEG (40 mg) and urea (20 mg) were used. Ultrafine and hydrophilic cobalt ferrite NPs that showed appreciable magnetic properties obtained in the present experimental procedure would be of great interest in various biomedical applications.