Physical,mechanical, and transdermal diltiazem release analysis of nanosilica tailored various poly(vinyl alcohol) membranes

Hybrid membranes based on poly(vinyl alcohol) (PVA) of widely different molecular weights and ex situ nanosilica were synthesized and characterized as transdermal delivery device for Diltiazem hydrochloride. Investigations showed that change in PVA molecular weight strongly influenced physico‐mechanicals of the hybrids especially at low nanosilica content than at higher levels. As for example at 1 wt %, low molecular weight PVA induced finer dispersion of silica nanoparticles resulting into higher dry state crystallinity and mechanical strength but slightly lower biocompatibility as compared to high molecular weight PVA. Those variations in physico‐mechanicals finally affected Diltiazem retention and its elution from those membranes under physiological conditions. Low molecular weight PVA produced highest drug retention as well as slowest yet steady release than both high molecular weight PVA and neat PVA membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2076–2086, 2013     

Thermal properties and degradation characteristics of polylactide,linear low density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer-grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882-91. Based on this, LLDPE 80 (80 wt% LLDPE & 20 wt% PLLA) and M-g-L 80/4 (80 wt% LLDPE, 20 wt% PLLA and 4 parts compatibilizer per hundred parts of resin) were found to be an optimum composition. FTIR reveals that the presence of compatibilizer shifts carbonyl peak hence some increase in interaction between LLDPE and PLLA. Morphological characteristics of the fracture surface of with and without compatibilizer blends were examined by scanning electron microscopy. It shows that use of compatibilizer enhances the dispersions of PLLA in LLDPE matrix. Thermogravimetric (TG) analysis of blends shows the M-g-L 80/4 blend has higher thermal stability among studied blends. The degradation study under different pH of soil compost gives that in alkaline condition and the presence of compatibilizer was favorable for degradation. This blend may be used for packaging application.     

Degradation behaviors of linear low‐density polyethylene and poly(L‐lactic acid) blends

In this study, the degradability of linear low‐density polyethylene (LLDPE) and poly(L ‐lactic acid) (PLLA) blend films under controlled composting conditions was investigated according to modified ASTM D 5338 (2003). Differential scanning calorimetry, X‐ray diffraction, and Fourier transform infrared spectroscopy were used to determine the thermal and morphological properties of the plastic films. LLDPE 80 (80 wt % LLDPE and 20 wt % PLLA) degraded faster than grafted low‐density polyethylene–maleic anhydride (M‐g‐L) 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) and pure LLDPE (LLDPE 100). The mechanical properties and weight changes were determined after composting. The tensile strength of LLDPE 100, LLDPE 80, and M‐g‐L 80/4 decreased by 20, 54, and 35%, respectively. The films, as a result of degradation, exhibited a decrease in their mass. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Imaging Cancer Cells Expressing the Folate Receptor with Carbon Dots Produced from Folic Acid

Development of new imaging tools for cancer cells in vitro and in vitro is important for advancing cancer research, elucidating drug effects upon cancer cells, and studying cellular processes. We showed that fluorescent carbon dots (C‐dots) synthesized from folic acid can serve as an effective vehicle for imaging cancer cells expressing the folate receptor on their surface. The C‐dots, synthesized through a simple one‐step process from folic acid as the carbon source, exhibited selectivity towards cancer cells displaying the folate receptor, making such cells easily distinguishable in fluorescence microscopy imaging. Biophysical measurements and competition experiments both confirmed the specific targeting and enhanced uptake of C‐dots by the folate receptor‐expressing cells. The folic acid‐derived C‐dots were not cytotoxic, and their use in bioimaging applications could aid biological studies of cancer cells, identification of agonists/antagonists, and cancer diagnostics.     

Antibody microarray detection of Escherichia coli O157:H7: Quantification, assay limitations, and capture efficiency

A sandwich fluorescent immunoassay in a microarray format was used to capture and detect E. coli O157:H7. Here, we explored quantitative aspects, limitations, and capture efficiency of the assay. When biotinylated capture antibodies were used, the signal generated was higher (over 5-fold higher with some cell concentrations) compared to biotinylated protein G-bound capture antibodies. By adjusting the concentration of reporter antibody, a linear fluorescent response was observed from approximately 3.0 x 10(6) to approximately 9.0 x 10(7) cells/mL, and this was in agreement with the number of captured bacteria as determined by fluorescence microscopy. Capture efficiency calculations revealed that, as the number of bacteria presented for capture decreased, capture efficiency increased to near 35%. Optimization experiments, with several combinations of capture and reporter antibodies, demonstrated that the amount of bacteria available for capture (10(6) versus 10(8) cells/mL) affected the optimal combination. The findings presented here indicate that antibody microarrays, when used in sandwich assay format, may be effectively used to capture and detect E. coli O157:H7.     

Predicting the effective thermal conductivity of carbon nanotube based nanofluids

Adding a small volume fraction of carbon nanotubes (CNTs) to a liquid enhances the thermal conductivity significantly. Recent experimental findings report an anomalously wide range of enhancement values that continue to perplex the research community and remain unexplained. In this paper we present a theoretical model based on three-dimensional CNT chain formation (percolation) in the base liquid and the corresponding thermal resistance network. The model considers random CNT orientation and CNT-CNT interaction forming the percolating chain. Predictions are in good agreement with almost all available experimental data. Results show that the enhancement critically depends on the CNT geometry (length), volume fraction, thermal conductivity of the base liquid and the nanofluid (CNT-liquid suspension) preparation technique. Based on the physical mechanism of heat conduction in the nanofluid, we introduce a new dimensionless parameter that alone characterizes the nanofluid thermal conductivity with reasonable accuracy (～ ± 5%).     

Microstructure and dielectric functions of Ge nanocrystals embedded between amorphous Al2O3 films: study of confinement and disorder

Ge nanocrystals (6–9?nm) embedded between amorphous Al₂O₃ films were produced in a cluster beam deposition system. The microstructural evaluation and compressive stress experienced by the Ge nanocrystals due to the presence of an oxide layer, nanoparticle size distribution and their changes due to thermal annealing were studied by X-ray diffraction, HRTEM and Raman spectroscopy. Spectroscopic ellipsometry was used to measure the dielectric functions of the deposited films. A multilayer model based on the effective medium approximation was used to analyze the variation of percentage of defects and the extent of disorder with particle size of the nanocrystals. The correlation between the microstructural characteristics and optical properties was established by evaluating standard sum rules. Germanium nanocrystals show visible photo luminescence at room temperature around 3.0 and 2.8?eV. However, a peak shift towards lower energies with increasing particle size due to thermal annealing was not detected. The experimentally observed luminescence is presumably originated due to the presence of oxide-related defect centers at the interface between the germanium nanocrystals and the embedded oxide layers.     

Enantioselective N‐Heterocyclic Carbene‐Catalyzed Annulations of 2‐Bromoenals with 1,3‐Dicarbonyl Compounds and Enamines via Chiral α,β‐Unsaturated Acylazoliums

The N‐heterocyclic carbene (NHC)‐catalyzed generation of chiral α,β‐unsaturated acylazoliums from 2‐bromoenals followed by their interception with 1,3‐dicarbonyl compounds or enamines, the formal [3+3] annulation reaction, is reported. The reaction results in the enantioselective synthesis of synthetically and medicinally important dihydropyranones and dihydropyridinones, and tolerates a wide range of functional groups. It is noteworthy that the reaction takes place under mild reaction conditions utilizing relatively low catalyst loadings. In addition, based on DFT calculations, a mechanistic scenario involving the attack of the nucleophile from below the plane of the α,β‐unsaturated acylazoliums, and the mode of enantioinduction is presented.     

Emulsion Stabilized with Starch Octenyl Succinate Prolongs Nisin Activity Against Listeria Monocytogenes in a Cantaloupe Juice Model

Food safety related to fresh and fresh‐cut produce, such as cantaloupe, is a great challenge in the food industry. Various processing technologies, including the use of antimicrobial materials, have been applied to reduce pathogens. Nisin, an antimicrobial peptide, shows strong inhibitory activity against Listeria monocytogenes (LM); however, it suffers from quick depletion in foods. In this study, the protective effect of starch octenyl succinate (starch‐OS) stabilized emulsion on nisin was evaluated in a cantaloupe juice model. Results showed that the proteolytic enzyme in cantaloupe juice caused nisin depletion, and the adsorption of nisin in emulsion led to considerable protection of antimicrobial activity. After 1, 3, and 6 d of incorporation with cantaloupe juice, the size of LM inhibitory ring were 7.64, 7.60, and 2.97 mm, respectively for emulsion formulations, whereas it reduced from 3.60 mm to a negligible level for nisin‐alone. This study showed the potential of using carbohydrate colloidal systems to prolong the efficacy of antimicrobial materials.