Biomedical subjects

Brij Moudgil

Publications and source records attributed to Brij Moudgil.

5 recordsLinked to original sources

PubMed2006

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes.

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye. The PHF molecules adsorbed to the surface of titanium dioxide due to electrostatic forces, with adsorption density being higher at lower pH values. The surface coverage of titanium dioxide nanoparticles by PHF molecules determined the extent of enhancement, with an optimum dosed weight ratio of PHF to titanium dioxide at 0.001. Hydroxylation and concomitant solubilization of fullerenes allow their unique electronic properties to be harnessed for photocatalysis.

Adsorption↗

PubMed2006

Nanoparticles for bioimaging.

The emergence of synthesis strategies for the fabrication of nanosized contrast agents is anticipated to lead to advancements in understanding biological processes at the molecular level in addition to progress in the development of diagnostic tools and innovative therapies. Imaging agents such as fluorescent dye-doped silica nanoparticles, quantum dots and gold nanoparticles have overcome many of the limitations of conventional contrast agents (organic dyes) such as poor photostability, low quantum yield, insufficient in vitro and in vivo stability, etc. Such particulates are now being developed for absorbance and emission in the near infrared region, which is expected to allow for real time and deep tissue imaging via optical routes. Other efforts to facilitate deep tissue imaging with pre-existing technologies have lead to the development of multimodal nanoparticles which are both optical and MRI active. The main focus of this article is to provide an overview of properties and design of contrast agents such as dye-doped silica nanoparticles, quantum dots and gold nanoparticles for non-invasive bioimaging.

Contrast Media↗

PubMed2006

Research strategies for safety evaluation of nanomaterials, part V: role of dissolution in biological fate and effects of nanoscale particles.

Dissolution, translocation, and disposition have been shown to play a key role in the fate and effects of inhaled particles and fibers. Concepts that have been applied in the micron size range may be usefully applied to the nanoscale range, but new challenges are presented based on the small size and possible change in the dissolution:translocation relationship. The size of the component molecule itself may be on the nanoscale. Solute concentration, surface area, surface morphology, surface energy, dissolution layer properties, adsorbing species, and aggregation are relevant parameters in considering dissolution at the nanoscale. With regard to the etiopathology caused by these types of particulates, the metrics of dose (particle number, surface area, mass or shape) is not yet well defined. Analytical procedures for assessing dissolution and translocation include chemical assay and particle characterization. Leaching of substituents from particle surfaces may also be important. Compartmentalization within the respiratory tract may add another dimension of complexity. Dissolution may be a critical step for some nanoscale materials in determining fate in the environment and within the body. This review, combining aspects of particle toxicology, material science, and analytical chemistry, is intended to provide a useful basis for developing relevant dissolution assay(s) for nanoscale particles.

Animals↗

PubMed2005

Morphology and mechanical properties of surfactant aggregates at water-silica interfaces: molecular dynamics simulations.

Dilute and concentrated surfactant systems at the solid-liquid interface are examined using classical molecular dynamics simulations. Particular emphasis is placed on understanding how surfactants aggregate and form the micellar structure, how micelles change shape at high concentrations in aqueous media and in the presence of hydrophilic surfaces, and at what force this micellar structure breaks apart during indentation of micelle-covered surfaces with a proximal probe microscope tip. The specific system of interest is C12TAB (n-dodecyltrimethylammonium bromide) surfactant in an aqueous medium that is modeled with empirical potentials. The simulations predict that the micelle structure in water is compact and either spherical or elliptical in shape. In the presence of a hydrophilic surface of silica, the structure evolves into a flat elliptical shape, in agreement with experimental findings. The simulated indentation of the micelle/silica system causes the micelle to break apart at an indentation force of about 1 nN and form a surfactant monolayer. The predicted force curve is in excellent agreement with experimental measurements.

Journal Article↗

PubMed2005

Inactivation of bacterial endospores by photocatalytic nanocomposites.

A novel biocidal photocatalytic nanocomposite, composed of TiO(2) and multi-walled carbon nanotubes (MWNTs), was synthesized via wet chemistry followed by a heat treatment. Uniform anatase coatings on MWNTs were successfully obtained with a thickness of a few nanometers. The nanostructure of the composite was determined by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The needle-like shape of the nanocomposite provided more than three times higher photocatalytic specific surface area than commercial TiO(2) nanoparticles (Degussa P25) when dispersed in water. Moreover, under ultraviolet (UV) radiation the excited electrons can be trapped at the interface between the TiO(2) layer and MWNTs and they can also be scavenged through the conductive graphitic layers. Thus, an intense photochemical reaction yielding a powerful biocide can be expected. Irradiating bacterial endospores (Bacillus cereus) with solar UV lamps in presence of the novel photocatalyst successfully inactivated the spores while solar UV lamps only or solar UV Lamps with Degussa P25 showed no significant inactivating behavior. Performance of photocatalytic nanocomposites was assessed based on time to achieve 90% inactivation of spores (LD(90)) and also in terms of time required to achieve a 1.0 log(10) reduction of spores in the tail region of the inactivation curve.

Animals↗