Intracellular delivery of etoposide loaded biodegradable nanoparticles: cytotoxicity and cellular uptake studies

The preferred delivery systems for anticancer drugs would be the one which would have selective and effective destruction of cancer cells. In the present study etoposide (ETO) loaded nanoparticles (NP) were prepared using PLGA (ETO-PLGA NP), PLGA-MPEG block copolymer (ETO-PLGA-MPEG NP) and PLGA-Pluronic copolymer (ETO-PLGA-PLU NP) and they were evaluated for cytotoxicity and cellular uptake studies using two cancer cell lines, L1210 and DU145. The IC50 values for L1210 cells were 18.0, 6.2, 4.8 and 5.4 microM and for DU145 cells the IC50 values were 98.4, 75.1, 60.1 and 71.3 microM for ETO, ETO-PLGA NP, ETO-PLGA-MPEG NP and ETO-PLGA-PLU NP respectively. The increased cytotoxicities were attributed to increased uptake of the NPs by the cells. Moreover the ETO loaded PLGA-MPEG NP and PLGA-Pluronic NP showed a sustained cytotoxic effect till 5 days on both the cell lines. Results of the long term cytotoxicity study concluded that the drug loaded PLGA nanoparticulate formulations were efficient in decreasing the viability of the L1210 cells over a period of three days, whereas the pure drug exerted its maximum efficiency on the day one itself. Z-stack confocal images of NPs showed fluorescence activity in each section of DU 145 and L1210 cells indicating that the nanoparticles were internalized by the cells. The study concluded that ETO loaded PLGA NPs had higher cytotoxicity compared with that of the free drug and ETO-PLGA-MPEG NP and ETO-PLGA-PLU NP had higher cell uptake efficiency compared with that of ETO-PLGA NP. The developed PLGA based NPs shows promise to be used for cancer therapy.     

Investigating surface roughness of parts produced by SLS process

Selective laser sintering (SLS) has been recognized as one of the best rapid prototyping (RP) technique for producing solid models, directly from computer-aided design data by fussing together different layers with the help of laser light. Further, RP has traditionally been used for producing a solid model for visualization purpose and assessing kinematic functionality. So, the model is required to have superior mechanical integrity and surface quality for handling and model testing. This study investigates surface roughness (SR) of parts produced by SLS process. The empirical models have been purposed to predict the feasibility of different process parameters viz., laser power, scan spacing, bed temperature, hatch length, and scan count on SR. Further, these parameters have been optimized using face-centered central composite design with response surface methodology. The optimized parameters have been verified by conducting confirmation experiments.     

Sensitive and Reversible Detection of Methanol and Water Vapor by In Situ Electrochemically Grown CuBTC MOFs on Interdigitated Electrodes

The in situ electrochemical growth of Cu benzene‐1,3,5‐tricarboxylate (CuBTC) metal–organic frameworks, as an affinity layer, directly on custom‐fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5–7 µm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 µm and a height of 6–8 µm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion‐controlled kinetics (k = 2.9 mmol s^?0.5 g^?1_CuBTC). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity K _e = 174.8 bar^?1. A volume fraction f _MeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu‐IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100–8000 ppm.     

Protein adsorption characteristics of plasma treated polyurethane surfaces

The effect of various plasma surface treatments on the protein adsorption characteristics of two polyurethane elastomers (Acushnet E417-0 [ACx] and Texin 480 AR [TN]) were studied. Both substrates are based upon diphenylmethane 4,4-diisocyanate (MDI) hard segments and polyester soft segments. Adsorption characteristics of the untreated samples were initially established, followed by plasma treated surfaces. Contact angle and 2 h albumin adsorption were determined. (1) Results of this study indicate that the protein adsorption characteristics of crosslinked substrate ACx is more linear than that of non-crosslinked substrate TN. Further, substrate TN adsorbs seven-fold greater protein at a rate four times higher on its surface than ACx.N,N-Ethylene bis (stearamide), a processing aid used in substrate TN, may encourage greater protein adsorption on substrate TN and variation in the soft segment mobility between the substrates also may affect their adsorption characteristics. (2) Plasma treatments using CH₄ and/or C _x F _y chemistries increased the contact angle for both substrates while those with O₂ and O₂/CF₄ decreased the contact angle for the substrates considered. In general, the contact angle of the substrates exhibiting greater protein adsorption was smaller.     

Corrosion behaviour of Terfenol-D

The corrosion behaviour of pseudo-binary compound Tb_0.3Dy_0.7Fe_1.92 (Terfenol-D) was studied in 3.5% NaCl and 0.01 N Na₂SO₄ solutions using Tafel polarisation, linear polarisation, electrochemical impedance spectroscopy and weight loss techniques. Electrochemical testing revealed the adverse effect of chloride ions, as corrosion rates were higher in 3.5% NaCl solutions than in 0.01 N Na₂SO₄ solutions. The effect of aeration was studied by conducting experiments in freely-aerated, deaerated and fully-aerated conditions. Absence of oxygen accelerated corrosion in chloride environment, due to increased hydrogen interaction in presence of destabilised surface films. The improved corrosion resistance in chloride-free environment was correlated with morphological features of the corroded surfaces. Micro-compositional analysis of the corrosion products revealed that the corrosion products were primarily rich in rare earth elements. A comparison of all experimental techniques showed that Tafel extrapolation and EIS techniques provided reliable estimates of corrosion rate.     

Tungsten Oxide Thin Film Characterizations for Acetone Gas Detection

The gas sensing properties and topology of tungsten oxide thin films deposited by reactive-ion radio frequency magnetron sputtering at room temperature have been investigated. The abnormalities in behaviour of sensing film are observed when acetone gas is flowed over surface. The reduction reaction of surface and oxidation reaction of acetone gas have been studied. As the gas comes in contact with the surface, the molecules tend to reduce the surface, hence decreasing the resistance. The sensing film was annealed to 500 °C for 1 h for the purpose of achieving a suitable grain size for sensing to take place. Operational optimum temperature for sensing has been computed to be 260 °C. A grain size of 7.3 nm has been computed through analysis of AFM image and a film thickness of 100 nm has been calculated through surface profiler. The SEM image of the film demonstrates the grains developed on the surface. The XRD patterns reveal that the oxide showed up as WO₂. It has been observed that the response percentage is approximately 30% for acetone vapour concentration of 20 ppm and approximately 18% for the concentration of 15 ppm. The response time of the sensor is approximately 5 min and the recovery time is 4 min.     

Adsorption of casein onto alkali treated bentonite

The adsorption measurements of casein onto alkali treated bentonite were performed at room temperature and fixed pH (11.8) with an object to study the mode of casein adsorption at the alkali treated bentonite surfaces. The adsorption isotherm was found to have a Langmuir nature. The adsorption was pH dependent and increased with a decrease in temperature. The adsorption was quite sensitive to the presence of Cl⁻, SO, and PO ions and showed many interesting variations with increasing concentrations of the added anions. Various kinetic and adsorption parameters such as the adsorption coefficient, rate constants for adsorption and desorption, diffusion constant, and penetration rate constant were calculated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1656–1663, 2000     

A finite element solution for the two-dimensional elastic contact problems with friction

A numerical procedure developed for solving the two-dimensional elastic contact problems with friction is presented. This is a generalization of a procedure developed by Francavilla and Zienkiewicz to include frictional effects under proportionate loading. The method uses the flexibility matrix obtained by inversion of condensed stiffness matrix formed by eliminating all the nodes except those where contact is likely to take place and those with external forces. Compatibility of displacements for both normal and tangential directions is applied to those nodes which do not slip. However, for the nodes which slip, compatibility of displacements is applied for normal direction only and slip condition is applied in the tangential direction. The technique has been applied to several problems and very good results have been obtained. The number of iterations needed are very small.