Property modelling of lysozyme‐crosslinker‐alginate complexes using latent variable methods

Dependence of the Electroosmotic Flow in Bare Fused-Silica Capillaries from pH, Ionic Strength and Composition of Electrolyte Solutions Tailored for Protein Capillary Zone Electrophoresis

Differential scanning calorimetric studies on bovine serum albumin: II. Effects of neutral salts and urea

Summary Traditionally, the Poisson-Boltzmann equation is solved to describe the electrical potential in the diffuse layer of an electrolyte adjacent to a charged interface and the electrostatic contribution to the total interaction potential between the interface and the ionic species. A major assumption of the Poisson-Boltzmann equation is that ions act as point charges, which allows for an infinite ion and charge density near to the charged interface, and thus predicts that the zeta potential falls to zero at high ionic strength (typically >0.1M). However, experimental measurements have reported small but measurable zeta potential values at high ionic strength, showing the zeta potential does not tend to zero as predicted. Electrostatic forces acting between electrically charged mineral-brine and oil-brine interfaces in the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory have been used to explain observed increases in oil recovery during low salinity waterflooding. Injection of a low salinity brine is expected to create a more negative zeta potential at the mineral-brine interface. If the oil-brine interface is negatively charged, this increases the electrostatic repulsive force per unit area which, if larger than the disjoining pressure, should lead to improved oil recovery. However, the calculation of the electrostatic forces are normally based on the traditional Poisson-Boltzmann model which underestimates the electrostatic contribution at high salinity. Here, a modified Poisson-Boltzmann equation ( Borukhov et al., (1997) , Physical Review Letters, 79(3), 435), which accounts for steric effects in the diffuse layer at high salinity but recovers the original Poisson-Boltzmann equation at low salinity, has been combined with a triple layer model which accounts for charge in the Stern layer ( Revil et al., (1999) , Journal of Geophysical Research, 104). This combined model has been used to match experimental zeta potential measurements made on natural, intact sandstones across the ionic strength range 10–5 – 5M, including small and constant zeta potentials observed at ionic strength >0.4M. The effect of this modified Poisson-Boltzmann model on the total interaction potential and DLVO theory has further been investigated. Our relatively simple modification shows that the electrostatic forces at high salinity are larger than previously thought and should not be neglected when calculating total interaction forces. Previous models using classic DLVO theory for understanding low salinity waterflooding may be inaccurate as they incorrectly estimate the changes in the electrostatic forces that occur during injection of low salinity brines.

Stability of colloidal silica, sikron and polystyrene latex influenced by the adsorption of polycations of different charge density

Morphological analysis on the desiccation pattern from plasma drops has received increasing research attention due to its wide engineering applications in medical diagnostic screening. However, most previous studies focused on the internal drop flow rather than the actual distribution of nonvolatile materials in plasma drops, thus limiting their diagnostic relevance. To address this research gap, we developed a simulation model to explore the distribution of bovine serum albumin (BSA) particles and NaCl during drop desiccation. Different from previous simulation work, a nonuniform evaporation rate is implemented at the drop-air interface; also, aggregation between BSA particles and BSA adsorption onto substrate surfaces are both considered, subject to varying ionic strength in a moving medium. This comprehensive framework aims to overcome key oversimplifications in traditional models, such as the assumed uniform evaporation flux and the neglect of interparticle aggregation under varying ionic strength. Consequently, this approach provides new findings beyond prior observations, such as millisecond-scale BSA adsorption kinetics and the formation of a quantifiable and heterogeneous protein band near the drop periphery. Specifically, our model provides numerical forecasts to key BSA adsorption metrics under physiological conditions, including adsorption layer thickness and surface coverage, which are challenging to quantify experimentally. Also, rapid millisecond-scale adsorption kinetics is predicted, which is sensitive to the initial ionic strength. Concentration curves of BSA particles result from the interplay between inward sol-gel interface movement and interparticle aggregation, leading to a heterogeneous area with a highly nonuniform BSA distribution at the drop periphery, while a more homogeneous distribution is observed near the center. The extent of heterogeneity can be tuned by relative humidity, aggregation number between BSA particles, and the initial ionic strength. Simulations also provide the precise position of NaCl crystallization initiated near the drop center, and a conservative threshold concentration of 10 mM, below which crystallization is suppressed in a BSA saline drop.

Comprehensive study on the structure of the BSA from extended-to aged form in wide (2–12) pH range

Size and mobility of sodium dodecyl sulfate—bovine serum albumin complex as studied by dynamic light scattering and electrophoretic light scattering

Predicting equilibrium constants for ion exchange of proteins — a colloid science approach

The separation and purification of proteins is often carried out by chromatography. Mixed-mode adsorbents are interesting as they may combine favorable features of different chromatographic methods, such as ion-exchange chromatography (IEC) and hydrophobic interaction chromatography (HIC). Systematic experimental studies and models of adsorption isotherms of proteins on mixed-mode resins covering a wide range of parameters are still rare, which hampers both the scientific analysis of the complex processes that occur upon the adsorption of proteins on these resins as well as the practical separation design. Therefore, such studies were carried out in the present work for a model system: the adsorption of bovine serum albumin (BSA) on the mixed-mode resin Toyopearl MX-Trp-650M, which combines features of IEC and HIC resins. Adsorption isotherms were measured using sodium chloride, sodium sulfate, ammonium chloride, and ammonium sulfate at ionic strengths up to 3000 mM and for pH 4.0, 4.7, and 7.0 at 25 ^circC. In the studied pH ranges, BSA exhibits strongly varying net charges and undergoes a conformational change. At pH 4.0 and 4.7, an exponential decay of the BSA adsorption with increasing ionic strength was found at ionic strengths up to approximately 1000 mM, while a rather linear increase was observed at higher ionic strengths for all studied salts; for all salts and ionic strengths, decreasing adsorption with increasing pH value was found. Moreover, a mathematical model was developed, which enables the prediction of equilibrium adsorption isotherms of BSA on Toyopearl MX-Trp-650M for any ionic strength of the studied salts.

High-throughput single-molecule total internal reflection fluorescence microscopy was used to investigate the effects of pH and ionic strength on bovine serum albumin (BSA) adsorption, desorption, and interfacial diffusion at the aqueous-fused silica interface. At high pH and low ionic strength, negatively charged BSA adsorbed slowly to the negatively charged fused silica surface. At low pH and low ionic strength, where BSA was positively charged, or in solutions at higher ionic strength, adsorption was approximately 1000 times faster. Interestingly, neither surface residence times nor the interfacial diffusion coefficients of BSA were influenced by pH or ionic strength. These findings suggested that adsorption kinetics were dominated by energy barriers associated with electrostatic interactions, but once adsorbed, protein-surface interactions were dominated by short-range nonelectrostatic interactions. These results highlight the ability of single-molecule techniques to isolate elementary processes (e.g., adsorption and desorption) under steady-state conditions, which would be impossible to measure using ensemble-averaging methods.

Properties of protein adsorption onto pore surface during microfiltration: Effects of solution environment and membrane hydrophobicity

Controlled dual drug release by coaxial electrospun fibers – Impact of the core fluid on drug encapsulation and release

The selective separation of whey proteins was studied using colloidal gas aphrons generated from the cationic surfactant cetyl trimethyl ammonium bromide (CTAB). From the titration curves obtained by zeta potential measurements of individual whey proteins, it was expected to selectively adsorb the major whey proteins, i.e., bovine serum albumin, alpha-lactalbumin, and beta-lactoglobulin to the aphrons and elute the remaining proteins (lactoferrin and lactoperoxidase) in the liquid phase. A number of process parameters including pH, ionic strength, and mass ratio of surfactant to protein (M(CTAB)/M(TP)) were varied in order to evaluate their effect on protein separation. Under optimum conditions (2 mmol/l CTAB, M(CTAB)/M(TP) = 0.26-0.35, pH 8, and ionic strength = 0.018 mol/l), 80-90% beta-lactoglobulin was removed from the liquid phase as a precipitate, while about 75% lactoferrin and lactoperoxidase, 80% bovine serum albumin, 95% immunoglobulin, and 65% alpha-lactalbumin were recovered in the liquid fraction. Mechanistic studies using zeta potential measurements and fluorescence spectroscopy proved that electrostatic interactions modulate only partially the selectivity of protein separation, as proteins with similar surface charges do not separate to the same extent between the two phases. The selectivity of recovery of beta-lactoglobulin probably occurs in two steps: the first being the selective interaction of the protein with opposite-charged surfactant molecules by means of electrostatic interactions, which leads to denaturation of the protein and subsequent formation and precipitation of the CTAB-beta-lactoglobulin complex. This is followed by the separation of CTAB-beta-lactoglobulin aggregates from the bulk liquid by flotation in the aphron phase. In this way, CGAs act as carriers which facilitate the removal of protein precipitate.

Electrical charge of hyaline articular cartilage: Its role in the retention of anionic and cationic proteins

Onconase (ONC) is a member of a ribonuclease superfamily that has cytostatic activity against malignant mesothelioma (MM). The objective of this investigation was to develop bovine serum albumin (BSA)-chitosan based hybrid nanoformulations for the efficient delivery of ONC to MM while minimizing the exposure to normal tissues. Taguchi orthogonal array L9 type design was used to formulate ONC loaded BSA nanocarriers (ONC-ANC) with a mean particle size of 15.78 ± 0.24 nm (ζ = -21.89 ± 0.11 mV). The ONC-ANC surface was hybridized using varying chitosan concentrations ranging between 0.100 and 0.175% w/v to form various ONC loaded hybrid nanocarriers (ONC-HNC). The obtained data set was analyzed by principal component analysis (PCA) and principal component regressions (PCR) to decode the effects of investigated design variables. PCA showed positive correlations between investigated design variables like BSA, ethanol dilution, and total ethanol with particle size and entrapment efficiency (EE) of formulated nanocarriers. PCR showed that the particle size depends on BSA, ethanol dilution, and total ethanol content, while EE was only influenced by BSA content. Further analysis of chitosan and TPP effects used for coating of ONC-ANC by PCR confirmed their positive impacts on the particle size, zeta potential, and prolongation of ONC release compared to uncoated ONC-ANC. PCR analysis of preliminary stability studies showed increase in the particle size and zeta potential at lower pH. However, particle size, zeta potential, and EE of developed HNC were below 63 nm, 31 mV, and 96%, respectively, indicating their stability under subjected buffer conditions. Out of the developed formulations, HNC showed enhanced inhibition of cell viability with lower IC50 against human MM-REN cells compared to ONC and ONC-ANC. This might be attributed to the better cell uptake of HNC, which was confirmed in the cell uptake fluorescence studies. These studies indicated that a developed nanotherapeutic approach might aid in reducing the therapeutic dose of ONC, minimizing adverse effects by limiting the exposure of ONC to normal tissues, and help in the development of new therapeutic forms and routes of administration.