Structural Changes in Liposomal Vesicles in Association with Sodium Taurodeoxycholate

Enhancing oral bioavailability of dasatinib via supersaturable SNEDDS: Investigation of precipitation inhibition and IVIVC through in-vitro lipolysis-permeation model

Dasatinib (DASA), a potent second-generation multitarget kinase inhibitor marketed as Sprycel® (Tablet), is limited by poor oral bioavailability (14-24 %) and dose-related gastrointestinal side effects. A supersaturable self-nanoemulsifying drug delivery system (su-SNEDDS) designed to enhance DASA's solubility, sustain supersaturation, and improve oral bioavailability. The su-SNEDDS formulation comprises DASA, an oil, surfactant, co-surfactant, and polyvinylpyrrolidone (PVP) K30 as a precipitation inhibitor (PI). This innovative system demonstrated exceptional stability in gastrointestinal fluids and robustness against dilution, maintaining significantly elevated drug concentrations in the aqueous milieu. su-SNEDDS achieved ∼ 13.5-fold and 2-fold higher aqueous drug concentrations than DASA suspension and SNEDDS without PI, respectively, after 60 min of digestion. This improvement is attributed to the inhibition of crystal growth by PVP K30. In-vitro lipolysis-permeation and Caco-2 cell assays revealed significantly enhanced drug permeation with su-SNEDDS compared to DASA suspension and SNEDDS without PI. In-vivo pharmacokinetic studies further demonstrated ∼ 1.9-fold and 2.7-fold higher AUC compared to SNEDDS without PI and drug suspension, respectively. A linear correlation (R2 = 0.9042) was established between the AUC data obtained from in-vitro vs in-vivo study. These findings underscore the potential of su-SNEDDS to significantly enhance DASA's solubility, permeation and oral bioavailability, presenting a substantial advancement in pharmaceutical drug delivery systems. Moreover, in-vitro lipolysis-permeation could be promising tool to predict the in-vivo fate of the oral SNEDDS formulations.

Comparative Analysis of Bare and Quercetin-Loaded Nonionic Block Copolymer Micelles in an Artificial Gastrointestinal Medium

Block copolymer micelles have been increasingly used for the solubilization and delivery of hydrophobic drugs. There exists a possibility of dissociation of micelles and formation of other association structures in contact with the gastrointestinal fluid. In this study, we demonstrated the effect of the fed-state intestinal fluid (FeSSIF) upon characteristics of bare and quercetin (QCT)-loaded pluronic 123 (P123) micelles. Characterizations were performed using dynamic light scattering (DLS), 1H NMR, heteronuclear single-quantum coherence (HSQC), two-dimensional 1H-1H nuclear Overhauser effect spectroscopy (2D-NOESY), and diffusion-ordered spectroscopy (DOSY). In the case of bare micelles, we found copolymer-bile salt mixed aggregates without any noticeable change in size. DOSY data revealed that lecithin formed a separate aggregate in the FeSSIF. Complete micellar solubilization of QCT could be verified by the disappearance of its proton signals. At higher dose levels, the diffusion coefficient of micelles increased in the FeSSIF. We speculate that QCT-induced hydrophobicity and availability of FeSSIF components would have driven the formation of small-sized mixed assemblies. On the contrary, the diffusion coefficient of micelles decreased with an increase in the QCT load in the medium devoid of FeSSIF components. We deduce that lack of lecithin and bile salts precluded the formation of mixed assemblies in this case, and therefore, micelles turned heavier at higher QCT loads. Such insights on self-assembled formulations can be valuable in improving their biological performance.

Sugar-based Cryoprotectants Stabilize Liposomal Vesicles by Exhibiting a Cholesterol-like Effect

Liposomal vesicles tend to fuse and aggregate during lyophilization. To avoid these events, cryoprotectants are added to the dispersion before lyophilization. Herein, we have compared the effect of three commonly used cryoprotectants (mannitol, MTL; trehalose, THL; and β-cyclodextrin, β-CD) upon structural characteristics of liposomes. The formulation was prepared using ethanol injection method, and cryoprotectants were tested at three dose levels (2, 6, and 10 mM). We have elucidated their effect on soy lecithin (SL) liposomes formulated with and without cholesterol (CHL). Characterizations were performed using scattering, thermal, and spectroscopic techniques. CHL molecules interacted hydrophobically with the SL bilayer. In spite of triggering a noticeable increase in the hydrodynamic diameter (about 30 nm), CHL promoted the stabilization of vesicles. Hydrogen bonding interactions were verified by the shift in -OH stretching over 3300-3500 cm-1. This manifested in an increased phase transition temperature (Tm) of SL liposomes. Tm increased further upon incorporation of cryoprotectants, particularly with β-CD. Enthalpic changes were indicative of an affinity interaction between phospholipids and cryoprotectants, regardless of the presence of CHL. β-CD showed concentration-dependent changes in the energetics of this interaction. The affinity of cryoprotectant-liposome interaction has been ranked as β-CD ≫ THL > MNT.

Localized Delivery of Bioactives using Structured Liposomal Gels

Liposomes have gained a lot of interest for drug delivery applications, and some of these preparations have been commercialized. These are formulated with biocompatible components and can be used for delivering a wide range of payloads differing in aqueous solubility and molecular weight. Liposome-based delivery approaches are limited mainly by two factors: (a) poor dispersion stability, and (b) pre-mature leakage of payloads. In this review, we have discussed the stabilization of liposomal vesicles by their entrapment in hydrogels. Studies reveal that such hydrogels can maintain the structural integrity of liposomes. Release of liposomes from the hydrogel network can be modulated through careful screening of matrix former and degree of its cross-linking. Accordingly, we have reviewed the approaches of stabilizing liposomal vesicles through entrapment in hydrogels. Application of liposome-embedded hydrogels has been reviewed in context of localized drug delivery. Our discussion is focussed on the delivery of bioactives to the skin. Such an approach appears alluring from the standpoint of minimizing the undesirable distribution of payload(s) the systemic circulation and off-target sites.