Influence of Hofmeister anions on structural and thermal properties of a starch-protein-lipid nanoparticle.

A self-assembled soluble nanoparticle, composed of common food biopolymers (carbohydrate, protein) and lipid, was previously reported by our laboratory. Although carrying capacity of valuable small molecules was demonstrated, physical functional properties are also important. Given the stabilization or destabilization characteristics of Hofmeister anion on macromolecular structures, mainly on proteins, here, we investigated the effects of different sodium salts composed of different Hofmeister anions on the structural and thermal properties of these self-assembled nanoparticles for improved functionalities. The salts were added into the mixture that was prepared in a diluted system during nanoparticle formation. Increased concentration of kosmotropic anions, in contrast to the chaotropic anion tested, resulted in nanoparticles with higher molar mass, hydrodynamic radius, and molecular density with more compact arrangement. The nanoparticles produced in presence of kosmotropic anions dissociated at higher temperatures and required higher enthalpies compared to the control sample. Spherical nanoparticles were formed for the kosmotropes with shear thinning behavior, contrary to rod-like nanoparticles for the chaotrope with near-Newtonian behavior. These findings help to gain an understanding of the effect of altering environmental conditions on the nanoparticles with an aim of producing desired structures for applications.

Ultrasound-stimulated Brownian ratchet enhances diffusion of molecules retained in hydrogels.

We demonstrate that low-frequency ultrasonic stimulation applied directly to a hydrogel, at energy levels below the cavitation threshold, can control the release of a therapeutic molecule. The hydrogel that contained the molecules was enclosed within a hollow acoustic horn. The harmonic modes in the acoustic horn combined with the physical gel structure to induce a flashing ratchet that released all of the retained molecules in less than 90 s at an intensity of 1.5 W cm-2 (applied energy of 135 J cm-2, ultrasound center frequency of 27.9 ±â€¯1.5 kHz). In contrast, ultrasound is used currently as a remote stimulus for drug-delivery systems, at energy levels above the cavitation threshold. The low-energy flashing ratchet approach that we describe is applicable to drive the diffusion of molecules in a range of gels that are ubiquitous in biomedical systems, including for example in drug delivery, molecule identification and separation systems.

Solubility enhancement of hydrophobic compounds by cosolvents: role of solute hydrophobicity on the solubilization effect.

Drug solubilization is an important aspect of drug development. We investigate the relationship between solute hydrophobicity on the solubilization properties of water-cosolvent mixtures. The solubilization in water-cosolvent mixtures of seven chemically unrelated drugs was determined. The set of solutes included hydrocortisone, sulfanilamide, acetophenetidine, benzocaine, indomethacin, thymol and ibuprofen. Two sets of water-cosolvent mixtures were used in the study. A group of polar cosolvents consisting of three aliphatic alcohols, and a group of the less polar cosolvents NMP, tetraglycol and labrasol. The hydrophobicity of the drug has a direct impact on the solubilization obtained in the water-cosolvent mixtures. However, the role of hydrophobicity is different in the case of the polar cosolvents compared with the less polar ones. In polar cosolvents, the solubilization behavior is typical of polarity match, where the collective trend of solubility enhancement decreases as the activity coefficient of the solute in the solvent mixture increases. The result is a linear profile comprising the combined data of all solutes and all solvents. On the other hand, while the less polar cosolvents exhibit greater positive deviations from the log-linear cosolvency model, the collective solubility enhancement in these systems exhibits no readily discernible pattern. However, by taking into account the hydrophobicity of the solutes, a systematic effect becomes clearly apparent. In this case, the hydrophobicity of the solute demarcates its region in the solubilization profile.

The effect of dehydration conditions on the functionality of anhydrous amorphous raffinose.

The purpose of this investigation is to study the effect of dehydration conditions of raffinose pentahydrate (RF.5H2O) on the physical properties and functionality of the resulting material. Crystalline RF.5H2O was dehydrated at two temperatures, 80 degrees C and 110 degrees C, producing the amorphous anhydrous form (RF.am). The dehydration temperature had no effect on a number of physical properties of the obtained RF.am, including X-ray powder diffraction, surface energy and water uptake. However, despite resulting on the same dynamics and extent of water sorption, different dehydration temperatures produced amorphous samples with drastically different recrystallization tendencies. Thermodynamic parameters show that despite the similarities on certain physical attributes, different dehydration temperature results in samples with significantly different free energy, hence stability. The difference in free energy produced by the dehydration temperature is attributed to differences in supramolecular structure that persist even in the liquid domain (above T(g)) of the amorphous samples. Evidence of such effects is observed as fluctuations in heat capacity present in RF.am but absent in the freshly prepared glass and also supported by the presence of molecular mobility modes observed using thermal polarization measurements.

Limitations of amorphous content quantification by isothermal calorimetry using saturated salt solutions to control relative humidity: alternative methods.

Despite the high sensitivity of isothermal calorimetry (IC), reported measurements of amorphous content by this technique show significant variability even for the same compound. An investigation into the reasons behind such variability is presented using amorphous lactose and salbutamol sulfate as model compounds. An analysis was carried out on the heat evolved as a result of the exchange of water vapor between the solid sample during crystallization and the saline solution reservoir. The use of saturated salt solutions as means of control of the vapor pressure of water within sealed ampoules bears inherent limitations that lead in turn to the variability associated with the IC technique. We present an alternative IC method, based on an open cell configuration that effectively addresses the limitations encountered with the sealed ampoule system. The proposed approach yields an integral whose value is proportional to the amorphous content in the sample, thus enabling reliable and consistent quantifications.