Estimation of cholesterol solubilization by a mixed micelle binding model in aqueous tauroursodeoxycholate:lecithin:cholesterol solutions

Physiology and Physical Chemistry of Bile Acids

Bile acids (BAs) are facial amphiphiles synthesized in the body of all vertebrates. They undergo the enterohepatic circulation: they are produced in the liver, stored in the gallbladder, released in the intestine, taken into the bloodstream and lastly re-absorbed in the liver. During this pathway, BAs are modified in their molecular structure by the action of enzymes and bacteria. Such transformations allow them to acquire the chemical-physical properties needed for fulling several activities including metabolic regulation, antimicrobial functions and solubilization of lipids in digestion. The versatility of BAs in the physiological functions has inspired their use in many bio-applications, making them important tools for active molecule delivery, metabolic disease treatments and emulsification processes in food and drug industries. Moreover, moving over the borders of the biological field, BAs have been largely investigated as building blocks for the construction of supramolecular aggregates having peculiar structural, mechanical, chemical and optical properties. The review starts with a biological analysis of the BAs functions before progressively switching to a general overview of BAs in pharmacology and medicine applications. Lastly the focus moves to the BAs use in material science.

The Solubility-Permeability Trade-Off of Progesterone With Cyclodextrins Under Physiological Conditions: Experimental Observations and Computer Simulations

This study intended to evaluate the effect of cyclodextrins on the apparent solubility and permeability of lipophilic drugs under physiological conditions and establish in silico model to choose the optimal amount of cyclodextrins for cyclodextrin-containing oral formulations. In order to study the effect of cyclodextrins under physiological conditions, bile salts and lecithin were added into the rat intestinal perfusion solution to simulate the fasted intestinal fluid. In addition, the in vivo oral absorption performances of cyclodextrin-containing formulations were simulated by gastrointestinal simulation technology based on the advanced compartmental absorption and transit model. The permeability of progesterone was not significantly different between 0.1 mM and 1 mM of 2-hydroxypropyl-β-cyclodextrins (HP-β-CD) under physiological conditions. When the concentration of HP-β-CD was 1 mM, the permeability of progesterone under physiological conditions was significantly higher than that in vitro. The in silico model established in this study was validated by in vivo studies of 4 formulations containing different dosage of cyclodextrin, proving that it was accurate and reliable. In conclusion, this work that demonstrates the permeability of lipophilic drugs could not decrease quickly among a certain range of dosage of HP-β-CD in vivo. Studying the solubility-permeability interplay under physiological conditions would be more meaningful.

Preparation of a liposomal delivery system and its in vitro release of rapamycin

The aim of this study was to prepare a liposomal delivery system for rapamycin and study its in vitro release characteristics. The results may provide a foundation for the further development of a liposomal delivery system for rapamycin and the establishment of a new active treatment method targeted towards the cellular components of atherosclerotic plaques. The ethanol injection method was used to prepare rapamycin-containing liposomes. The formulation was optimized by orthogonal design, and the degree of rapamycin release by the liposomes was measured by the reverse dialysis method. Orthogonal testing showed that the optimum formulation had a phospholipid concentration of 4%, a phospholipid-cholesterol mass ratio of 8:1, a drug-lipid mass ratio of 1:20 and an aqueous phase pH of 7.4. Rapamycin-containing liposomes with an encapsulation efficiency of 82.11±2.13% were prepared, and the in vitro release of rapamycin from the liposomes complied with a first-order kinetic equation. In conclusion, the formulation was optimized, the prepared liposomes had a high rapamycin encapsulation rate and good reproducibility, and their in vitro release had a certain delayed-release effect.