Dipti Biswal

Hydrogel nanocomposites: a review of applications as remote controlled biomaterials

In the past few years, there has been increased interest in the development and applications of hydrogel nanocomposites, specifically as a new class of biomaterials. In some cases, the nanoparticles (e.g., gold, magnetic, carbon nanotubes) can absorb specific stimuli (e.g., alternating magnetic fields, near-IR light) and generate heat. This unique ability to remotely heat the nanocomposites allows for their remote controlled (RC) applications, including the ability to remotely drive the polymer through a transition event (e.g., swelling transition, glass transition). This review highlights some of the recent studies in the development of the RC hydrogel nanocomposites. In particular, some of the important applications of RC nanocomposites as RC drug delivery devices, as RC actuators, and in cancer treatment are discussed.

Synthesis and characterization of poly(antioxidant β-amino esters) for controlled release of polyphenolic antioxidants

Attenuation of cellular oxidative stress, which plays a central role in biomaterial-induced inflammation, provides an exciting opportunity to control the host tissue response to biomaterials. In the case of biodegradable polymers, biomaterial-induced inflammation is often a result of local accumulation of polymer degradation products, hence there is a need for new biomaterials that can inhibit this response. Antioxidant polymers, which have antioxidants incorporated into the polymer backbone, are a class of biomaterials that, upon degradation, release active antioxidants, which can scavenge free radicals and attenuate oxidative stress, resulting in improved material biocompatibility. In this work, we have synthesized poly(antioxidant β-amino ester) (PAβAE) biodegradable hydrogels of two polyphenolic antioxidants, quercetin and curcumin. The degradation characteristics of PAβAE hydrogels and the antioxidant activity of PAβAE degradation products were studied. Treatment of endothelial cells with PAβAE degradation products protected cells from hydrogen-peroxide-induced oxidative stress.

Lysozyme-imprinted polymer synthesized using UV free-radical polymerization

Molecular imprinting is a method to fabricate a polymeric material (molecularly imprinted polymer or MIP) capable of selectively recognizing template molecules. Molecular imprinting of small molecules has been studied widely. Less common, however, is the imprinting of biological macromolecules, including proteins, among which lysozyme is an important molecule in the food, pharmaceutical, and diagnostic sciences. In this study, lysozyme MIP was fabricated in two steps. First, lysozyme, PEG600DMA, and methacrylic acid were used as the template molecule, cross-linking monomer, and the functional monomer, respectively, in a UV free-radical polymerization process to synthesize a polymeric gel. Second, lysozyme was removed by enzymatic digestion. Non-imprinted polymer (NIP) was synthesized without lysozyme addition. To evaluate the preferential binding capability of MIP, lysozyme, RNase A, or a 50:50 mixture of lysozyme and RNase A was added to MIP and NIP and then released by digestion. It was found that when more lysozyme was added to the reaction mixture, the quantity of protein released from the polymer increased, reflecting more potential binding sites. Tests of MIP with a competitive binding mixture of lysozyme and RNase A showed the MIP preferentially bound a greater amount of lysozyme, up to 20 times more than RNase A. NIP bound only small amounts of both proteins and did not show a preference for binding either lysozyme or RNase A. These results demonstrate that lysozyme was successfully imprinted into the MIP by UV free-radical polymerization, and the fabricated MIP was able to preferentially bind its template protein.

Nanostructured materials for multifunctional applications under NSF-CREST research at Norfolk State University

Magnetic nanoparticles of CoFe2O4 have been synthesized under an applied magnetic field through a co-precipitation method followed by thermal treatments at different temperatures, producing nanoparticles of varying size. The magnetic behavior of these nanoparticles of varying size was investigated. As-grown nanoparticles demonstrate superparamagnetism above the blocking temperature, which is dependent on the particle size. The anomalous magnetic behavior is attributed to the preferred Co ions and vacancies arrangements when the CoFe2O4 nanoparticles were synthesized under applied magnetic field. Furthermore, this magnetic property is strongly dependent on the high temperature heat treatments, which produce Co ions and vacancies disorder. We performed the fabrication of condensed and mesoporous silica coated CoFe2O4 magnetic nanocomposites. The CoFe2O4 magnetic nanoparticles were encapsulated with well-defined silica layer. The mesopores in the shell were fabricated as a consequence of removal of organic group of the precursor through annealing. The NiO nanoparticles were loaded into the mesoporous silica. The mesoporous silica coated magnetic nanostructure loaded with NiO as a final product may have potential use in the field of biomedical applications. Growth mechanism of ZnO nanorod arrays on ZnO seed layer investigated by electric and Kelvin probe force microscopy. Both electric and Kelvin force probe microscopy was used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 °C, which is in the range of right surface potentials and energy measured between 500 °C and 700 °C. We demonstrated from both EFM and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods. This study will provide important understanding of growth of other nanostructures. ZnO nanolayers were also grown by atomic layer deposition techniques. These nanolayers of ZnO demonstrate remarkable optical and electrical properties. These nanolayers were patterned by the Electron Beam Lithography (EBL) technique. A major goal of nanotechnology is to couple the self-assembly of molecular nanostructures with conventional lithography, using either or both bottom-up and top-down fabrication methods, that would enable us to register individual molecular nanostructures onto the functional devices. However, combining the nanofabrication technique with high resolution Electron Beam Lithography, we can achieve 3D bimolecular or/and DNA origami that will be able to identify nucleic acid sequences, antigen targets, and other molecules, as for a perfect nano-biosensor. We have explored some of the nanopatterning using EBL in order to fabricate biomolecule sensing on a single chip with sub nm pitch. The applications are not limited for the bioactivity, but for enhancing immunoreactions, cell culture dishes, and tissue engineering applications.

Synthesis and characterization of functionalized magnetic nanoparticles

Magnetic nanoparticles have been used in a wide array of industrial and biomedical applications due to their unique properties at the nanoscale level. They are extensively used in magnetic resonance imaging (MRI), magnetic hyperthermia treatment, drug delivery, and in assays for biological separations. Furthermore, superparamagnetic nanoparticles are of large interest for in vivo applications. However, these unmodified nanoparticles aggregate and consequently lose their superparamagnetic behaviors, due to high surface to volume ratio and strong dipole to dipole interaction. For these reasons, surface coating is necessary for the enhancement and effectiveness of magnetic nanoparticles to be used in various applications. In addition to providing increased stability to the nanoparticles in different solvents or media, stabilizers such as surfactants, organic/inorganic molecules, polymer and co-polymers are employed as surface coatings, which yield magnetically responsive systems. In this work we present the synthesis and magnetic characterization of Fe3O4 nanoparticles coated with 3-aminopropyltriethoxy silane (APS) and citric acid. The particles magnetic hysteresis was measured by a superconducting quantum interference device (SQUID) magnetometer with an in-plane magnetic field. The uncoated and coated magnetic nanoparticles were characterized by using fourier transform infrared (FTIR), UV-vis, X-ray diffraction, transmission electron microscopy, and thermo-gravimetric analysis.