Influence of residual solvents on the physical properties of transdermal drug delivery systems.

The purpose of this investigation was to systematically assess the effect of residual solvents on the physical properties of a silicone adhesive-based transdermal system (TDS) containing n-heptane and o-xylene as residual solvents. The processing temperature was varied in this study to obtain various contents of residual solvents in the TDS. The adhesion performance was determined by evaluating the tack, shear, and peel of these TDS at week 0 and week 2. The adhesion measurements showed significant changes in tack values with a decrease in the contents of residual solvents, but the changes in peel and shear were insignificant. The rheological characteristics such as linear viscoelastic region, loss modulus and storage modulus were also measured. The outcome of the rheological measurements was found to be more sensitive to the changes in the contents of residual solvents in comparison to adhesion measurements. These results show that the residual solvent content may affect TDS performance and should be controlled from a product quality and performance perspective.

Quality by Design approach for studying the impact of formulation and process variables on product quality of oral disintegrating films.

The present investigation was carried out to understand the impact of formulation and process variables on the quality of oral disintegrating films (ODF) using Quality by Design (QbD) approach. Lamotrigine (LMT) was used as a model drug. Formulation variable was plasticizer to film former ratio and process variables were drying temperature, air flow rate in the drying chamber, drying time and wet coat thickness of the film. A Definitive Screening Design of Experiments (DoE) was used to identify and classify the critical formulation and process variables impacting critical quality attributes (CQA). A total of 14 laboratory-scale DoE formulations were prepared and evaluated for mechanical properties (%elongation at break, yield stress, Young's modulus, folding endurance) and other CQA (dry thickness, disintegration time, dissolution rate, moisture content, moisture uptake, drug assay and drug content uniformity). The main factors affecting mechanical properties were plasticizer to film former ratio and drying temperature. Dissolution rate was found to be sensitive to air flow rate during drying and plasticizer to film former ratio. Data were analyzed for elucidating interactions between different variables, rank ordering the critical materials attributes (CMA) and critical process parameters (CPP), and for providing a predictive model for the process. Results suggested that plasticizer to film former ratio and process controls on drying are critical to manufacture LMT ODF with the desired CQA.

ynthesis and Characterization of Fe3+ and Mn2+ Doped ZnS Quantum Dots for Photocatalytic Applications: Effect of 2-Mercaptoethanol and Chitosan as Capping Agents.

Fe3+ and Mn2+ capped ZnS quantum dots were synthesized using the chemical precipitation method at room temperature in aqueous media. The effect of 2-Mercaptoethanol and Chitosan as capping agents and dopants were investigated using Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), UV-Visible and Field Emission Scanning Electron Microscopy (FESEM) analysis of the nanocrystals. FTIR revealed the presence of respective capping agents and FESEM micrograph identifies the particles as poly-dispersed. TEM images showed agglomerated particles with crystal sized ˜3 nm. Particles were analyzed as cubic structured with peaks indexed at (1 1 1), (2 2 1) and (3 1 1) and an average crystalline size of 2.49±0.06 nm. Blue shift is obtained by both doping agents, and band gap values of ranging from 3.75­4.95 eV were reported. Characterizations suggests 2-mercaptoethanol as better capping agent compared to chitosan and has a greater potential for photocatalytic applications.

Enhanced dissolution of poorly soluble antiviral drugs from nanoparticles of cellulose acetate based solid dispersion matrices.

Polysaccharide-based polymers were used to produce nanoparticles of poorly soluble antiviral drugs using a rapid precipitation process. The structure-property relationships of four novel cellulose acetate-based polymers were studied for their solubility enhancement of poorly soluble drugs. Particles were purified by dialysis, and dried powders were recovered after freeze-drying. The particle diameters were 150-200 nm. The target drug loading in the particles was 25 wt%, and the drug loading efficiencies were 80-96%. The effects of the formulation process and nanoparticle properties on drug solubility were investigated. All nanoparticles afforded increased solubility and faster release compared to pure drugs. Drug release was a function of the relative hydrophobicity (or solubility parameters) of the polymers.

Role of hydrophobicity in bacterial adherence to carbon nanostructures and biofilm formation.

The role of cell and surface hydrophobicity in the adherence of the waterborne bacterium Mycobacterium smegmatis to nanostructures and biofilm formation was investigated. Carbon nanostructures (CNs) were synthesized using a flame reactor and deposited on stainless steel grids and foils, and on silicon wafers that had different initial surface hydrophobicities. Surface hydrophobicity was measured as the contact angle of water droplets. The surfaces were incubated in suspensions of isogenic hydrophobic and hydrophilic strains of M. smegmatis and temporal measurements of the numbers of adherent cells were made. The hydrophobic, rough mutant of M. smegmatis adhered more readily and formed denser biofilms on all surfaces compared to its hydrophilic, smooth parent. Biofilm formation led to alterations in the hydrophobicity of the substratum surfaces, demonstrating that bacterial cells attached to CNs are capable of modifying the surface characteristics.