Stable reversed vesicles in oil: characterization studies and encapsulation of model compounds

Alternative Excipients for Protein Stabilization in Protein Therapeutics: Overcoming the Limitations of Polysorbates

Given their safety and efficiency in protecting protein integrity, polysorbates (PSs) have been the most widely used excipients for the stabilization of protein therapeutics for years. In recent decades, however, there have been numerous reports about visible or sub-visible particles in PS-containing biotherapeutic products, which is a major quality concern for parenteral drugs. Alternative excipients that are safe for parenteral administration, efficient in protecting different protein drugs against various stress conditions, effective in protein stabilization in high-concentrated liquid formulations, stable under the storage conditions for the duration of the product's shelf-life, and compatible with other formulation components and the primary packaging are highly sought after. The aim of this paper is to review potential alternative excipients from different families, including surfactants, carbohydrate- and amino acid-based excipients, synthetic amphiphilic polymers, and ionic liquids that enable protein stabilization. For each category, important characteristics such as the ability to stabilize proteins against thermal and mechanical stresses, current knowledge related to the safety profile for parenteral administration, potential interactions with other formulation components, and primary packaging are debated. Based on the provided information and the detailed discussion thereof, this paper may pave the way for the identification or development of efficient excipients for biotherapeutic protein stabilization.

Structural transition of reverse cylindrical micelles to reverse vesicles by mixtures of lecithin and inorganic salts

HYPOTHESIS

The transformation from reverse micelles to reverse vesicles is influenced by electrostatic interactions between lecithin headgroups and inorganic salts. The electrostatic interactions are expected to influence molecular geometry of lecithin, resulting in a reduction in critical packing parameter (p). Hence, it should be possible to drive structural transitions of reverse self-assembled structures by addition of inorganic salts to lecithin solutions.

EXPERIMENTS

Structural transitions of reverse micelles and reverse vesicles were formulated including lecithin and inorganic salts as a function of concentration in cyclohexane. A systematic study was performed using inorganic salts with the different valences of the cations such as Li⁺, Ca²⁺, and La³⁺. To probe the nanodomain structures from the lecithin/salt mixtures, small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used.

FINDINGS

Adding salts to lecithin solutions induced the systematic transformation of reverse self-assembled structures from reverse spherical micelles to reverse cylindrical micelles and finally to reverse vesicles. The transformation was also correlated with interactions between lecithin headgroups and salts, that is, Li⁺ < Ca²⁺ < La³⁺. In addition, a water-soluble dye such as rhodamine B (RB) can be readily encapsulated into reverse micelles and vesicles, indicating that they are potentially useful for controlled solute delivery.

A rheological study of reverse vesicles formed by oleic acid and diethylenetriamine in cyclohexane

A reverse aggregate system composed of oleic acid and diethylenetriamine in cyclohexane has been studied.

From reverse worms to reverse vesicles formed by mixed zwitterionic and non-ionic surfactants in cyclohexane

SB-12 with C₁₂E₄ forms reverse wormlike micelles or reverse vesicles in cyclohexane depending on the ratio of C₁₂E₄ to SB-12.

Membrane alternatives in worlds without oxygen: Creation of an azotosome

The lipid bilayer membrane, which is the foundation of life on Earth, is not viable outside of biology based on liquid water. This fact has caused astronomers who seek conditions suitable for life to search for exoplanets within the "habitable zone," the narrow band in which liquid water can exist. However, can cell membranes be created and function at temperatures far below those at which water is a liquid? We take a step toward answering this question by proposing a new type of membrane, composed of small organic nitrogen compounds, that is capable of forming and functioning in liquid methane at cryogenic temperatures. Using molecular simulations, we demonstrate that these membranes in cryogenic solvent have an elasticity equal to that of lipid bilayers in water at room temperature. As a proof of concept, we also demonstrate that stable cryogenic membranes could arise from compounds observed in the atmosphere of Saturn's moon, Titan, known for the existence of seas of liquid methane on its surface.

Sucrose esters as natural surfactants in drug delivery systems--a mini-review

Sucrose esters (SEs) are widely used in the food and cosmetic industries and there has recently been great interest in their applicability in different pharmaceutical fields. They are natural and biodegradable excipients with well-known emulsifying and solubilizing behavior. Currently the most common pharmaceutical applications of SEs are for the enhancement of drug dissolution and drug absorption/permeation, and in controlled-release systems. Although the number of articles on SEs is continuously increasing, they have not yet been widely used in the pharmaceutical industry. The aim of this review is to discuss and summarize some of the findings and applications of SEs in different areas of drug delivery. The article highlights the main properties of SEs and focuses on their use in pharmaceutical technology and on their regulatory and toxicological status.

The influence of the incorporation of cholesterol and water on the particle size, bilayer thickness, melting behavior, and relative sucrose ester composition of reversed vesicles

The influence of the incorporation of cholesterol and water on the particle size, bilayer thickness, melting behavior, and relative sucrose ester composition of reversed vesicles was studied. Reversed vesicles (RVs) were prepared of sucrose ester in silicon oil by sonication. The RVs were characterized by polarized light microscopy, laser diffraction, high-performance liquid chromatography, small angle X-ray scattering (SAXS), and differential scanning calorimetry. The particle size distributions of the studied dispersions were bimodal with peaks at 5 and 0.4 microm. There was no significant difference in the sucrose ester composition of these two size categories of RVs. The incorporation of cholesterol and water had no effect on the size distribution of the RVs. The SAXS results showed that the RVs prepared without cholesterol and water consisted of bilayers with fully interdigitated alkyl chains. The incorporation of high concentrations of cholesterol caused a phase separation within the bilayers. The incorporation of water also resulted in a phase separation within the bilayers but at a lower cholesterol concentration. The presence of two different size classes of RVs in one RVs dispersion and the phase separation within the bilayers of certain compositions can have consequences for the application of RVs.