Systematic investigation on the interaction of bovine serum albumin with ZnO nanoparticles using fluorescence spectroscopy.

Zinc oxide (ZnO) nanoparticles with average size of ~7.5nm were synthesized to investigate their interaction with bovine serum albumin (BSA) at different temperatures. Fluorescence quenching, synchronous and polarization spectroscopy along with UV-vis absorption, circular dichroism and resonance light scattering spectroscopy techniques were used to establish the interaction mechanism between ZnO and BSA. The obtained results confirmed that the ZnO nanoparticles (NPs) quench the fluorophore of BSA by forming ground state complex in the solution. The fluorescence quenching data was also used to determine binding sites and binding constants at different temperatures. The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) suggest that the binding process occurs spontaneously by involving hydrogen bond and van der Waals interactions. The synchronous fluorescence spectra reveal that the microenvironment close to both the tyrosine and tryptophan residues of BSA is perturbed and that the hydrophobicity of both the residues is increased in the presence of ZnO NPs. Resonance light scattering, circular dichroism, and fluorescence polarization spectra suggest the formation of BSA-ZnO complex and conformational changes in BSA. The calculated distance between the BSA and ZnO NPs suggests that the energy transfer from excited state of BSA to ZnO NPs occurs with high efficiency.

Formulation and antitumor activity evaluation of nanocrystalline suspensions of poorly soluble anticancer drugs.

PURPOSE: Determine if wet milling technology could be used to formulate water insoluble antitumor agents as stabilized nanocrystalline drug suspensions that retain biological effectiveness following intravenous injection. METHODS: The versatility of the approach is demonstrated by evaluation of four poorly water soluble chemotherapeutic agents that exhibit diverse chemistries and mechanisms of action. The compounds selected were: piposulfan (alkylating agent), etoposide (topoisomerase II inhibitor), camptothecin (topoisomerase I inhibitor) and paclitaxel (antimitotic agent). The agents were wet milled as a 2% w/v solids suspension containing 1% w/v surfactant stabilizer using a low energy ball mill. The size, physical stability and efficacy of the nanocrystalline suspensions were evaluated. RESULTS: The data show the feasibility of formulating poorly water soluble anticancer agents as physically stable aqueous nanocrystalline suspensions. The suspensions are physically stable and efficacious following intravenous injection. CONCLUSIONS: Wet milling technology is a feasible approach for formulating poorly water soluble chemotherapeutic agents that may offer a number of advantages over a more classical approach.

Evaluation of penetration enhancement of lidocaine by nonionic surfactants through hairless mouse skin in vitro.

The effect of two nonionic surfactants (polyoxyethylene sorbitan monoesters) on percutaneous absorption of lidocaine in the presence of various concentrations of propylene glycol is reported. Comparisons were made in vitro using excised hairless mouse skin as the barrier membrane. Under infinite dose conditions, steady-state flux was enhanced by surfactants at high propylene glycol concentrations. The same trend was observed following application of a thin layer of formulation to the skin (finite-dose conditions). However, penetration behavior was complex due to: (a) changes in vehicle composition following application, (b) temperature changes resulting from evaporation or moisture uptake, and (c) depletion of lidocaine as a result of penetration with compositions that lost water by evaporation. Two peaks in the flux versus time curve were observed. Surfactant monomer concentration in the vehicles was increased in the presence of propylene glycol.

Effect of polyethylene glycol 400 on the penetration of drugs through human cadaver skin in vitro.

The effect of polyethylene glycol 400 on the penetration of drugs through human cadaver skin is reported. Polyethylene glycol 400 was used in various concentrations in the donor and the receptor compartments. It was observed that polyethylene glycol 400 had significant effects on the penetration rates of compounds, both when used in the donor as well as in the receptor solutions. These effects were barrier specific and are related to the alteration of the skin structure and the mass flow of water.

Flocculation of sulfamerazine suspensions by a cationic polymer.

Flocculation by a cationic polymer of sulfamerazine suspensions containing a wetting agent was evaluated. Suspensions with sufficient surfactant concentrations to ensure complete wetting were deflocculated. When the anionic surfactant, dioctyl sodium sulfosuccinate, was used as a wetting agent, the suspensions were flocculated over a limited polymer concentration range. Flocculation was attributed to simultaneous interaction of a polymer molecule with more than one particle. At higher polymer concentrations, the particles were covered completely with polymer, leading to repulsion between the particles and deflocculation of the suspensions. The polymer concentration required for flocculation provided evidence for interaction between the anionic surfactant and the cationic polymer. Suspensions containing a nonionic surfactant also were flocculated using various polymer concentrations. When a surfactant mixture was employed in the suspensions, the peak sedimentation volume of flocculated systems and the concentration of polymer at the peak depended on the surfactant mixture composition.