Determination of effective diffusion coefficient and interfacial mass transfer coefficient of bovine serum albumin (BSA) adsorption into porous polyethylene membrane by microscope FTIR-mapping study

Experimental study of the supercritical CO2 diffusion coefficient in porous media under reservoir conditions

Reliable measurement of the CO2 diffusion coefficient in consolidated oil-saturated porous media is critical for the design and performance of CO2-enhanced oil recovery (EOR) and carbon capture and storage (CCS) projects. A thorough experimental investigation of the supercritical CO2 diffusion in n-decane-saturated Berea cores with permeabilities of 50 and 100 mD was conducted in this study at elevated pressure (10-25 MPa) and temperature (333.15-373.15 K), which simulated actual reservoir conditions. The supercritical CO2 diffusion coefficients in the Berea cores were calculated by a model appropriate for diffusion in porous media based on Fick's Law. The results show that the supercritical CO2 diffusion coefficient increases as the pressure, temperature and permeability increase. The supercritical CO2 diffusion coefficient first increases slowly at 10 MPa and then grows significantly with increasing pressure. The impact of the pressure decreases at elevated temperature. The effect of permeability remains steady despite the temperature change during the experiments. The effect of gas state and porous media on the supercritical CO2 diffusion coefficient was further discussed by comparing the results of this study with previous study. Based on the experimental results, an empirical correlation for supercritical CO2 diffusion coefficient in n-decane-saturated porous media was developed. The experimental results contribute to the study of supercritical CO2 diffusion in compact porous media.

Validation of kinetic modeling of progesterone release from polymeric membranes

Mathematical modeling in drug release systems is fundamental in development and optimization of these systems, since it allows to predict drug release rates and to elucidate the physical transport mechanisms involved. In this paper we validate a novel mathematical model that describes progesterone (Prg) controlled release from poly-3-hydroxybutyric acid (PHB) membranes. A statistical analysis was conducted to compare the fitting of our model with six different models and the Akaike information criterion (AIC) was used to find the equation with best-fit. A simple relation between mass and drug released rate was found, which allows predicting the effect of Prg loads on the release behavior. Our proposed model was the one with minimum AIC value, and therefore it was the one that statistically fitted better the experimental data obtained for all the Prg loads tested. Furthermore, the initial release rate was calculated and therefore, the interface mass transfer coefficient estimated and the equilibrium distribution constant of Prg between the PHB and the release medium was also determined. The results lead us to conclude that our proposed model is the one which best fits the experimental data and can be successfully used to describe Prg drug release in PHB membranes.

Synthesis, swelling and drug-release behaviour of a poly(N,N-diethylacrylamide-co-(2-dimethylamino) ethyl methacrylate) hydrogel

In this study, poly(N,N-diethylacrylamide-co-(2-dimethylamino) ethyl methacrylate) (poly(DEA-co-DMAEMA)) hydrogels were synthesized by changing the initial DEA/DMAEMA mol ratio. The hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). In comparison with the PDEA hydrogel, the equilibrium swelling ratio (ESR) and lower critical solution temperature (LCST) of the hydrogels increase with the increase of DMAEMA content in the feed. The deswelling and reswelling kinetics and cytotoxicity of the different composition ratios of DEA to DMAEMA in the co-polymerized hydrogels were also investigated in detail. The absorption and release behaviour of the model drug, bovine serum albumin, were found to be dependent on hydrogel composition and environment temperature, which suggests that these materials have potential application as intelligent drug carriers.

Effect of ionic environments on the adsorption and diffusion characteristics of serine alkaline protease enzyme in polyethersulfone ultrafiltration membranes

Static adsorption of serine alkaline protease (SAP) enzyme on hydrophobic polyether sulfone (PES) ultrafiltration membranes in different ionic environments was investigated. The amount of SAP adsorbed on membranes was the lowest at its isoelectric point (IEP) where the maximum adsorption was obtained below the IEP of the enzyme. The extent of SAP adsorption in the phosphate buffer solutions including different salts followed the order: (NH4)2HPO4 > KH2PO4 > Na2HPO4-NaH2PO4 (buffer) > CaCl2 > ((NH4)2HPO4 + H2PO4 + CaCl2), which was consistent with the Hofmeister series. The zeta potentials of membranes contacted with the ionic species were calculated by streaming potential measurements and found that the increase in ionic strength decreased the electrical double layer thickness leading to a decrease in adsorption. A model based on mass balance was developed to calculate the diffusion coefficient of SAP in PES membranes. Employing experimental data evaluated in a diffusion cell along with the data of adsorption isotherms, diffusion coefficients of SAP in PES membranes in the presence of different ionic species were calculated. To detect the structural changes occurred, membrane surfaces were analysed by Fourier transform infrared-attenuated total reflectance (FTIR-ATR) measurements.