Lecithin in mixed micelles attenuates the cytotoxicity of bile salts in Caco-2 cells

PEG vs. zwitterions: How these surface decorations determine cellular uptake of lipid-based nanocarriers

AIM

To evaluate the impact of polyethylene glycol (PEG) and zwitterionic surface decoration of lipid-based nanocarriers (NC) on cellular uptake.

METHODS

Anionic, neutral and cationic zwitterionic lipid-based NCs based on lecithin were compared with conventional PEGylated lipid-based NCs regarding stability in biorelevant fluids, interaction with endosome mimicking membranes, cytocompatibility, cellular uptake and permeation across intestinal mucosa.

RESULTS

PEGylated and zwitterionic lipid-based NCs exhibited a droplet size between 100 and 125 nm with a narrow size distribution. For the PEGylated and zwitterionic lipid-based NCs only minor alterations in size and PDI in fasted state intestinal fluid and mucus containing buffer were observed, demonstrating similar bioinert properties. Erythrocytes interaction studies revealed enhanced endosomal escape properties for zwitterionic lipid-based NCs compared to PEGylated lipid-based NCs. For the zwitterionic lipid-based NCs negligible cytotoxicity on Caco-2 and HEK cells, even in the highest tested concentration of 1 % (v/v) was recorded. The PEGylated lipid-based NCs showed a cell survival of ≥75 % for concentrations ≤0.05 % on Caco-2 and HEK cells, which was considered as non-toxic. For the zwitterionic lipid-based NCs up to 60-fold higher cellular uptake on Caco-2 cells was determined compared to PEGylated lipid-based NCs. For the cationic zwitterionic lipid-based NCs the highest cellular uptake with 58.5 % and 40.0 % in Caco-2 and HEK cells, respectively, was determined. The results were confirmed visually by life cell imaging. Ex-vivo permeation experiments using rat intestinal mucosa demonstrated up to 8.6-fold enhanced permeation of the lipophilic marker coumarin-6 in zwitterionic lipid-based NCs compared to the control. Up to 6.9-fold enhanced permeation of coumarin-6 in neutral zwitterionic lipid-based NCs compared to the PEGylated counterpart was recorded.

CONCLUSION

The replacement of PEG surfactants with zwitterionic surfactants is a promising approach to overcome the drawbacks of conventional PEGylated lipid-based NCs regarding intracellular drug delivery.

Enhancement of ocular anti-glaucomic activity of agomelatine through fabrication of hyaluronic acid modified-elastosomes: formulation, statistical optimisation, in vitro characterisation, histopathological study, and in vivo assessment

AIM

The aim of this manuscript was to fabricate agomelatine (AGM) loaded elastosomes to improve its corneal permeation and ocular bioavailability. AGM is a biopharmaceutical classification system (BCS) class II with low water solubility and high membrane permeability. It has a potent agonistic action on melatonin receptors, so it is used for glaucoma treatment.

METHODS

Elastosomes were made using modified ethanol injection technique according to a 22 × 41 full factorial design. The chosen factors were: edge activators (EAs) type, surfactant percent (SAA %w/w), and cholesterol:surfactant ratio (CH:SAA ratio). The studied responses were encapsulation efficiency percent (EE%), mean diameter, polydispersity index (PDI), zeta potential (ZP), percentage of drug released after two hours (Q2h%), and 24 hours (Q24h%).

RESULTS

The optimum formula with the desirability of 0.752 was composed of Brij98 as EA type, 15%w/w SAA%, and 1:1 CH:SAA ratio. It revealed EE% of 73.22%w/v and mean diameter, PDI, ZP, Q2h%, and Q24h% values of 484.25 nm, 0.31, -30.75 mV, 32.7%w/v, and 75.6%w/v, respectively. It demonstrated acceptable stability for three months and superior elasticity than its conventional liposome. The histopathological study ensured the tolerability of its ophthalmic application. Also, it was proven to be safe from the results of the pH and refractive index tests. The in vivo pharmacodynamic parameters of the optimum formula revealed dominance in a maximum % decrease in intraocular pressure (IOP), the area under the IOP response curve, and mean residence time with the value of 82.73%w/v, 820.69%h, and 13.98 h compared to that of the AGM solution (35.92%w/v, 181.30%h, and 7.52 h).

CONCLUSIONS

Elastosomes can be a promising option to improve AGM ocular bioavailability.

Self-assembly of bile salts and their mixed aggregates as building blocks for smart aggregates

The present communication offers a comprehensive overview of the self-assembly of bile salts emphasizing their mixed smart aggregates with a variety of amphiphiles. Using an updated literature survey, we have explored the dissimilar interactions of bile salts with different types of surfactants, phospholipids, ionic liquids, drugs, and a variety of natural and synthetic polymers. While assembling this review, special attention was also provided to the potency of bile salts to alter the size/shape of aggregates formed by several amphiphiles to use these aggregates for solubility improvement of medicinally important compounds, active pharmaceutical ingredients, and also to develop their smart delivery vehicles. A fundamental understanding of bile salt mixed aggregates will enable the development of new strategies for improving the bioavailability of drugs solubilized in newly developed potential hosts and to formulate smart aggregates of desired morphology for specific targeted applications. It enriches our existing knowledge of the distinct interactions exerted in mixed systems of bile salts with variety of amphiphiles. By virtue of this, researchers can get innovative ideas to construct novel nanoaggregates from bile salts by incorporating various amphiphiles that serve as a building block for smart aggregates for their numerous industrial applications.

Effect of oxidation and in vitro intestinal hydrolysis on phospholipid toxicity towards HT29 cell line serving as a model of human intestinal epithelium

Oxidation of food-derived phospholipids (PLs) can influence nutrient digestion and induce oxidative stress in gastrointestinal epithelium. In this study, hen egg yolk PL fraction was used to evaluate the effect of lipoxygenase (LOX)-induced PL oxidation on the rate of PL hydrolysis catalyzed by pancreatic phospholipase A₂ (PLA₂) in the presence of bile salts (BSs). Then, PL/BS solutions containing native or oxidized PLs were used in in vitro intestinal digestion to assess the effect of PL oxidation and hydrolysis on the toxicity towards HT29 cell line. Based on the obtained results, we suggest that hexanal and (E)-2-nonenal, formed by the decomposition of PL hydroperoxides, inhibited PLA₂ activity. The cell exposure to simulated intestinal fluid (SIF) containing BSs decreased HT29 cell viability and significantly damaged cellular DNA. However, the genotoxic effect was reversed in the presence of all tested PL samples, while the protective effect against the BS-induced cytotoxicity was observed for native non-hydrolyzed PLs, but was not clearly visible for other samples. This can result from an overlap of other toxic effects such as lipotoxicity or disturbance of cellular redox homeostasis. Taking into account the data obtained, it was proposed that the PLA₂ activity decline in the presence of PL oxidation products may be a kind of protective mechanism against rapid release of oxidized FAs characterized by high cytotoxic effect towards intestinal epithelium cells.

Hyaluronic acid-enriched bilosomes: an approach to enhance ocular delivery of agomelatine via D-optimal design: formulation, in vitro characterization, and in vivo pharmacodynamic evaluation in rabbits

Agomelatine (AGO) is a dual-functional drug. It uses as an antidepressant when orally administrated and antiglaucomic when topically applied to the eye. This study aimed to formulate AGO into bilosomal vesicles for glaucoma treatment, as modern studies pointed out the effect of topical AGO on intraocular pressure for the treatment of glaucoma. A modified ethanol injection technique was used for the fabrication of AGO bilosomes according to a D-optimal design. Phosphatidylcholine (PC) to edge activator (EA) ratio, Hyaluronic acid percentage (HA%), and EA type were utilized as independent variables. The measured responses were percent entrapment efficiency (EE%), particle size (PS), polydispersity index, zeta potential, percentage of drug released after 2 h (Q_2h%), and 24 h (Q_24h%). The optimal bilosomal formula (OB), with the desirability of 0.814 and the composition of 2:1 PC: EA ratio, 0.26% w/v HA and sodium cholate as EA, was subjected to further in vitro characterizations and in vivo evaluation studies. The OB formula had EE% of 81.81 ± 0.23%, PS of 432.45 ± 0.85 nm, Q_2h% of 42.65 ± 0.52%, and Q_24h% of 75.14 ± 0.39%. It demonstrated a higher elasticity than their corresponding niosomes with a typical spherical shape of niosomes by using transmission electron microscope. It exhibited acceptable stability over three months. pH and Refractive index measurements together with the histopathological study ensured that the OB formula is safe for the eye and causes no ocular irritation or blurred vision. The OB formula showed superiority in the in vivo pharmacodynamics parameters over the AGO solution, so AGO-loaded bilosome could improve ocular delivery and the bioavailability of agomelatine.

Impact of excipient emulsions made from different types of oils on the bioavailability and metabolism of curcumin in gastrointestinal tract

Low bioavailability currently limits the potential of curcumin as a health-promoting dietary compound. This study therefore explored the potential of excipient emulsions to improve curcumin bioavailability. Oil-in-water excipient emulsions were prepared using different types of oils: corn oil, olive oil, and medium chain triglycerides (MCT). The excipient emulsions increased the transportation rate of curcumin across the Caco-2 cell monolayer and showed ability to protect curcumin from metabolism in the enterocytes, with the olive oil-based systems exhibiting the highest efficacy. In addition, most of curcumin metabolites were present as hexahydro-curcumin (HHC) and its conjugates. Our results show that excipient emulsions can improve curcumin bioavailability by increasing its trans-enterocyte absorption and reducing cellular metabolism. Moreover, they show that these effects depend on the type of oil used to produce them. These findings have important implications for the rational design of lipid-based delivery systems to enhance the bioavailability of hydrophobic nutraceuticals like curcumin.

Bile acid transporter-mediated oral absorption of insulin via hydrophobic ion-pairing approach

Despite many ongoing and innovative approaches, there are still formidable challenges in the clinical translation of oral peptide drugs into marketable products due to their low absorption and poor bioavailability. Herein, a novel nanocarrier platform was developed that employs a hydrophobic ion-pairing (HIP) of model peptide (insulin) and the anionic bile salt (sodium glycodeoxycholate, SGDC), and markedly improves intestinal absorption via the bile acid pathway. The developed HIP-nanocomplexes (C1 and C2) were optimized, characterized, and in vitro and in vivo evaluation were performed to assess oral efficacy of these system. The optimal molar ratios of C1 and C2-nanocomplexes were 30:1 and 6:1 (SGDC:insulin), respectively. Compared to the insulin solution, the C1 and C2 nanocomplexes significantly enhanced the permeation of insulin across the Caco-2 cell monolayers, with 6.36- and 4.05-fold increases in apparent permeability, respectively. Uptake mechanism studies were conducted using different endocytosis inhibitors and apical sodium-dependent bile acid transporter (ASBT)-transfected MDCK cells, which demonstrated the involvement of the energy-dependent ASBT-mediated active transport. Furthermore, the intrajejunal administration of C1 and C2 resulted in their pharmacological availabilities (PA) being 6.44% and 0.10%, respectively, indicating increased potential for C1, when compared to C2. Similarly, the PA and the relative bioavailability with intrajejunal administration of the C1 were 17.89-fold and 16.82-fold greater than those with intracolonic administration, respectively, confirming better jejunal absorption of C1. Overall, these findings indicate that the HIP-nanocomplexes could be a prominent platform for the effective delivery of peptides with improved intestinal absorption.

Combined evaluation of proliferation and apoptosis to calculate IC50 of VPA-induced PANC-1 cells and assessing its effect on the Wnt signaling pathway

Pancreatic ductal adenocarcinoma (PDAC) is among the most deadly cancers. Since most patients develop resistance to conventional treatments, new approaches are in urgency. Valproic acid (VPA) was shown to induce apoptosis and reduce proliferation in PANC-1 cells. Wnt signaling pathway is known to be involved in apoptosis and PDAC onset. However, VPA-induced apoptosis and its impact on Wnt signaling in PDACs are not linked, yet. We aimed to calculate IC₅₀ of VPA-induced PANC-1 cells by combined analyses of proliferation and apoptosis, while assessing its effect on Wnt signaling pathway. PANC-1 was induced with increased VPA doses and time points. Three independent proliferation and apoptosis assays were performed utilizing carboxyfluorescein succinimidyl ester and Annexin V/PI staining, respectively. Flow cytometry measurements were analyzed by CellQuest and NovoExpress. Taqman hydrolysis probes and SYBR Green PCR Mastermix were assessed in expression analyses of Wnt components utilizing 2^-ΔΔCt method. Cell proliferation was inhibited by 50% at 2.5 mM VPA that evoked a significant apoptotic response. Among the screened Wnt components and target genes, only LEF1 exhibited significant four-fold upregulation at this concentration. In conclusion, cancer studies mostly utilize MTT or BrdU assays in estimating cell proliferation and calculating IC₅₀ of drugs, which provided conflicting VPA dosages utilizing PANC-1 cells. Our novel combined approach enabled specific, accurate and reproducible IC₅₀ calculation at single cell basis with no apparent effect on Wnt signaling components. Future studies are needed to clarify the role of LEF1 in this model.

Bilosomes as Promising Nanovesicular Carriers for Improved Transdermal Delivery: Construction, in vitro Optimization, ex vivo Permeation and in vivo Evaluation

Purpose

The goal of this research was to enhance the transdermal delivery of lornoxicam (LX), using nanovesicular carriers composed of the bile salt sodium deoxycholate (SDC), soybean phosphatidyl choline (SPC) and a permeation enhancer limonene.

Methods

Thin-film hydration was the technique employed for the fabrication using a Box–Behnken design with three central points. The investigated factors were SPC molar concentration, SDC amount in mg and limonene percentage (%). The studied responses were percent entrapment efficiency (%EE), particle size (PS), polydispersity index (PDI), zeta potential (ZP), and in vitro drug release (after 2, 10 h). In order to obtain the optimum formula, numerical optimization by Design-Expert® software was used. Electing the optimized bilosomal formula was based on boosting %EE, ZP (as absolute value) and in vitro drug release, taking in consideration diminishing PS and PDI. Further assessment of the selected formula was achieved by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), stability testing, ex vivo skin permeation and deposition. The in vivo pharmacodynamics activities of the optimized formula were examined on male rats and mice and compared to that of the oral market product.

Results

The optimized bilosomal formula demonstrated to be nonirritant, with noticeably enhanced anti-inflammatory and antinociceptive activities. Superior in vivo permeation was proved by confocal laser scanning microscopy (CLSM).

Conclusion

The outcomes demonstrated that bilosomes could improve transdermal delivery of lornoxicam.

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GYY4137 Attenuates Sodium Deoxycholate-Induced Intestinal Barrier Injury Both In Vitro and In Vivo

Objectives

Substantial studies have demonstrated that an elevated concentration of deoxycholic acid (DCA) in the colonic lumen may play a critical role in the pathogenesis of intestinal barrier dysfunction and inflammatory bowel disease (IBD). The purpose of this study was to investigate the protective effects of GYY4137, as a novel and synthetic H₂S donor, on the injury of intestinal barrier induced by sodium deoxycholate (SDC) both in vivo and in vitro.

Methods

In this study, Caco-2 monolayers and mouse models with high SDC concentration in the lumen were used to study the effect of GYY4137 on intestinal barrier dysfunction induced by SDC and its underlying mechanisms.

Results

In Caco-2 monolayers, a short period of addition of SDC increased the permeability of monolayers obviously, changed distribution of tight junctions (TJs), and improved the phosphorylation level of myosin light chain kinase (MLCK) and myosin light chain (MLC). However, pretreatment with GYY4137 markedly ameliorated the SDC-induced barrier dysfunction. Being injected with GYY4137 could enable mice to resist the SDC-induced injury of the intestinal barrier. Besides, GYY4137 promoted the recovery of the body weight and intestinal barrier histological score of mice with the gavage of SDC. GYY4137 also attenuated the decreased expression level of TJs in mice treated with SDC.

Conclusion

Taken together, this research suggests that GYY4137 preserves the intestinal barrier from SDC-induced injury via suppressing the activation of P-MLCK-P-MLC2 signaling pathway and increasing the expression level of tight junctions.

Anionic versus cationic bilosomes as oral nanocarriers for enhanced delivery of the hydrophilic drug risedronate

Albeit its well known potency as a postmenopausal osteoporosis treatment, Risedronate suffers from poor oral bioavailability and high oral toxicity. This is the first work to assess the potential of bilosomes to address challenges of RS oral delivery. Furthermore, impact of integrating cationic moiety into bilosomes on intestinal digestability and toxicity of RS nanovesicles was first investigated in this article. Prepared formulations were optimized based on physicochemical properties, digestibility, intestinal permeation and local toxicity studies. Optimized preparations were prepared by reversed phase evaporation technique with three extrusion cycles and loaded by 10 mg/ml RS. Molar lipid to bile salt to cholesterol ratio was adjusted to 4:1:1 at pH 5. Addition of cholesterol had significantly improved bilosomes stability to digestive media. Results also revealed that permeation of anionic vesicles increased permeation by 1.5 times more than RS solution and reduced drug toxicity by 2 folds. On the other hand, Cationic bilosomes showed good stability in GIT fluids but their induced oral toxicity could limit their use. In conclusion, bilosomes are superior over liposomes regarding protection of delivery system from the damaging effect of external in digestive bile salts. In addition, it decreases toxicity issues of orally administered drugs.

Bile Acids and Their Derivatives as Potential Modifiers of Drug Release and Pharmacokinetic Profiles

Bile acids have received considerable interest in the drug delivery research due to their peculiar physicochemical properties and biocompatibility. The main advantage of bile acids as drug absorption enhancers is their ability to act as both drug solubilizing and permeation-modifying agents. Therefore, bile acids may improve bioavailability of drugs whose absorption-limiting factors include either poor aqueous solubility or low membrane permeability. Besides, bile acids may withstand the gastrointestinal impediments and aid in the transporter-mediated absorption of physically complexed or chemically conjugated drug molecules. These biomolecules may increase the drug bioavailability also at submicellar levels by increasing the solubility and dissolution rate of non-polar drugs or through the partition into the membrane and increase of membrane fluidity and permeability. Most bile acid-induced effects are mediated by the nuclear receptors that activate transcriptional networks, which then affect the expression of a number of target genes, including those for membrane transport proteins, affecting the bioavailability of a number of drugs. Besides micellar solubilization, there are many other types of interactions between bile acids and drug molecules, which can influence the drug transport across the biological membranes. Most common drug-bile salt interaction is ion-pairing and the formed complexes may have either higher or lower polarity compared to the drug molecule itself. Furthermore, the hydroxyl and carboxyl groups of bile acids can be utilized for the covalent conjugation of drugs, which changes their physicochemical and pharmacokinetic properties. Bile acids can be utilized in the formulation of conventional dosage forms, but also of novel micellar, vesicular and polymer-based therapeutic systems. The availability of bile acids, along with their simple derivatization procedures, turn them into attractive building blocks for the design of novel pharmaceutical formulations and systems for the delivery of drugs, biomolecules and vaccines. Although toxic properties of hydrophobic bile acids have been described, their side effects are mostly produced when present in supraphysiological concentrations. Besides, minor structural modifications of natural bile acids may lead to the creation of bile acid derivatives with the reduced toxicity and preserved absorption-enhancing activity.

Bile Acids and Their Derivatives as Potential Modifiers of Drug Release and Pharmacokinetic Profiles

Bile acids have received considerable interest in the drug delivery research due to their peculiar physicochemical properties and biocompatibility. The main advantage of bile acids as drug absorption enhancers is their ability to act as both drug solubilizing and permeation-modifying agents. Therefore, bile acids may improve bioavailability of drugs whose absorption-limiting factors include either poor aqueous solubility or low membrane permeability. Besides, bile acids may withstand the gastrointestinal impediments and aid in the transporter-mediated absorption of physically complexed or chemically conjugated drug molecules. These biomolecules may increase the drug bioavailability also at submicellar levels by increasing the solubility and dissolution rate of non-polar drugs or through the partition into the membrane and increase of membrane fluidity and permeability. Most bile acid-induced effects are mediated by the nuclear receptors that activate transcriptional networks, which then affect the expression of a number of target genes, including those for membrane transport proteins, affecting the bioavailability of a number of drugs. Besides micellar solubilization, there are many other types of interactions between bile acids and drug molecules, which can influence the drug transport across the biological membranes. Most common drug-bile salt interaction is ion-pairing and the formed complexes may have either higher or lower polarity compared to the drug molecule itself. Furthermore, the hydroxyl and carboxyl groups of bile acids can be utilized for the covalent conjugation of drugs, which changes their physicochemical and pharmacokinetic properties. Bile acids can be utilized in the formulation of conventional dosage forms, but also of novel micellar, vesicular and polymer-based therapeutic systems. The availability of bile acids, along with their simple derivatization procedures, turn them into attractive building blocks for the design of novel pharmaceutical formulations and systems for the delivery of drugs, biomolecules and vaccines. Although toxic properties of hydrophobic bile acids have been described, their side effects are mostly produced when present in supraphysiological concentrations. Besides, minor structural modifications of natural bile acids may lead to the creation of bile acid derivatives with the reduced toxicity and preserved absorption-enhancing activity.

Mixed micellar system stabilized with saponins for oral delivery of vitamin K

Poorly soluble vitamin K cannot be absorbed by patients suffering from cholestasis due to extremely low level of bile salts in the intestine. A formulation of vitamin K including glycocholic acid (i.e. Konakion® MM), does not increase bioavailability because it is unstable due to protonation of glycocholic acid at gastric pH. To develop a stable formulation, saponins were introduced as neutral surfactants to (partly) replace glycocholic acid. Experimental design was made to investigate the effect of the composition on particle size at neutral pH and upon acidification at pH 1.5. Two formulations that were within the optimized composition window were loaded with vitamin K and those showed superior stability at low pH as compared to Konakion® MM: sizes were between 43 and 46 nm at pH 7.3 and between 46 and 58 nm after 1 h incubation at pH 1.5, respectively, but large aggregates were formed at pH 1.5 in presence of Konakion® MM. Micelles were cytocompatible with Caco-2 cells at concentration of surfactants (saponins and glycocholic acid) up to 0.15 mg/ml. Uptake of vitamin K by Caco-2 cells was 4.2-4.9 nmol/mg protein for saponins-containing formulations and 7.1 nmol/mg protein for Konakion® MM. This, together with the superior stability at low pH, makes saponins-containing mixed micelles promising oral formulations for vitamin K.

Assessment of Beneficial and Possible Toxic Effects of Two New Alfalfa-Derived Shelf Products

Aerial parts of Medicago sativa L. have been used as food and its consumption has been associated with health benefits, one among the most important being menopausal symptoms control. This work was aimed to explore possible pharmacological effects of two new alfalfa-derived products that have recently emerged as daily beverage preparations. In exploring their potential estrogenic effects, they produced no relevant alteration in the uterus. However, lowering glucose levels until normal values without causing further hypoglycemic effect were observed, when rats were treated with 1.5 g/kg/day samples. In vivo acute toxicity was not found when the alfalfa products were tested up to 3 g/kg rat weight. Furthermore, in vitro studies were conducted to assess their possible toxic effects. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase tests were carried out on the Caco-2 cell model to determine cell viability and membrane integrity. A concentration-dependent effect was observed, with a significant decrease in cell viability after exposure to concentrations of alfalfa product up to 100 mg/mL (after 3 h of incubation) and 50 mg/mL (after 24 h of treatment). Although in vitro level, the decrease in cell viability at these still low doses may underlie some toxicity, making necessary additional studies before any recommendation of a sustained consumption of these products by humans.

A Mixed Micelle Formulation for Oral Delivery of Vitamin K

PURPOSE

To develop a stable micellar formulation of vitamin K for oral delivery, because the commercial and clinically used formulation of vitamin K (Konakion® MM) destabilizes at gastric pH resulting in low bioavailability of this vitamin in neonates with cholestasis.

METHODS

Mixed micelles composed of EPC, DSPE-PEG 2000 and glycocholic acid, with and without vitamin K, were prepared by a film hydration method. The influence of pH on the stability of the micelles was analyzed by dynamic light scattering (DLS). The critical micelle concentration (CMC) was determined by fluorescence spectroscopy using pyrene and the morphology was evaluated by transmission electron microscopy . Caco-2 cells were used to study the cytocompatibilty.

RESULTS

Mixed micelles with mean diameters from 7.1 to 11.0 nm and a narrow size distribution (PDI < 0.2) were obtained after 3 membrane extrusion cycles. Konakion® MM formed aggregated particles at gastric pH, which was avoided through steric stabilization by introducing PEG. TEM showed that mixed micelles had a spherical size (diameter of around 10 nm) with a narrow size distribution in agreement with the DLS results. The loading capacities for vitamin K of mixed micelles with varying molar fractions of DSPE-PEG and EPC (from 0/100 to 50/50 (mol/mol)) were 10.8-5.0 w%, respectively. The mixed micelles showed good cytocompatibility at concentrations of glycocholic acid between 0.12 and 1.20 mM.

CONCLUSIONS

Mixed micelles with superior stability to Konakion® MM at low pH were obtained by introducing DSPE-PEG 2000. These are therefore attractive oral formulations for vitamin K.

Ginsenoside Rg3 bile salt-phosphatidylcholine-based mixed micelles: design, characterization, and evaluation

20(R)-Ginsenoside Rg3 (G-Rg3) has good inhibition of tumor angiogenesis and anti-tumor effect. However, its poor aqueous solubility and liposolubility are not ideal for clinical applications. In this study, a G-Rg3 bile salt-phosphatidylcholine-based mixed micelle system (BS-PC-MMS) was prepared. The optimization of G-Rg3 BS-PC-MMS was carried out using response surface methodology based on a central composite design. The encapsulation efficiency (EE) and light transmission (LT) of the optimized formulation were 90.69±2.54% and 99.10±3.12%, respectively. The average particle size of micelles was 20 nm. To increase the stability of G-Rg3 BS-PC-MMS, the lyophilized formulation of micelles was prepared. The G-Rg3 BS-PC-MMS did not produce hemolysis of erythrocytes within a certain concentration range and exhibited a good inhibition of tumor cells. The chick embryo chorioallantoic membrane assay results showed that the G-Rg3 BS-PC-MMS significantly inhibited angiogenesis. The G-Rg3 BS-PC-MMS is thus shown to be a safe, stable, and promising drug delivery system.

Denatured globular protein and bile salt-coated nanoparticles for poorly water-soluble drugs: Penetration across the intestinal epithelial barrier into the circulation system and enhanced oral bioavailability

Oral drug delivery is the most preferred route for patients; however, the low solubility of drugs and the resultant poor absorption compromise the benefits of oral administration. On the other hand, for years, the overwhelmingly accepted mechanism for enhanced oral absorption using lipid nanocarriers was based on the process of lipid digestion and drug solubilization in the small intestine. Few reports indicated that other bypass pathways are involved in drug absorption in the gastrointestinal tract (GIT) for oral delivery of nanocarriers. Herein, we report a new nanoemulsion system with a denatured globular protein with a diameter of 30 nm, soybean protein isolates (SPI), and bile salt as emulsifiers, aiming to enhance the absorption of insoluble drugs and explore other pathways for absorption. A BCS class II drug, fenofibrate (FB), was used as the model drug. The SPI and bile salt-coated Ns with a diameter of approximately 150 nm were prepared via a high-pressure homogenizing procedure. Interestingly, the present Ns could be converted to solid dosage form using fluid-bed coating technology, maintaining a nanoscale size. Most importantly, in a model of in situ rat intestinal perfusion, Ns could penetrate across the intestinal epithelial barrier into the systemic circulation and then obtain biodistribution into other tissues. In addition, Ns significantly improved FB oral absorption, exhibited as a greater than 2- and 2.5-fold increase in Cmax and AUC0-t, respectively, compared to the suspension formulation. Overall, the present Ns are promising nanocarriers for the oral delivery of insoluble drugs, and the penetration of intact Ns across the GIT barrier into systemic circulation may be a new strategy for improved drug absorption with the use of nanocarriers.

Absorption-Enhancing Effects of Bile Salts

Bile salts are ionic amphiphilic compounds with a steroid skeleton. Among the most important physiological properties of bile salts are lipid transport by solubilization and transport of some drugs through hydrophobic barriers. Bile salts have been extensively studied to enhance transepithelial permeability for different marker molecules and drugs. They readily agglomerate at concentrations above their critical micelle concentration (CMC). The mechanism of absorption enhancement by bile salts appears to be complex. The aim of the present article was to review bile salt structure and their application as absorption enhancers and the probable mechanism for increasing permeation based on previous studies.

Multifaceted applications of bile salts in pharmacy: an emphasis on nanomedicine

The human body has long provided pharmaceutical science with biomaterials of interesting applications. Bile salts (BSs) are biomaterials reminiscent of traditional surfactants with peculiar structure and self-assembled topologies. In the pharmaceutical field, BSs were employed on the basis of two different concepts. The first concept exploited BSs' metabolic and homeostatic functions in disease modulation, whereas the second one utilized BSs' potential to modify drug-delivery characteristics, which recently involved nanotechnology. This review is the first to gather major pharmaceutical applications of BSs from endogenous organotropism up to integration into nanomedicine, with a greater focus on the latter domain. Endogenous applications highlighted the role of BS in modulating hypercholesterolemia and cancer therapy in view of enterohepatic circulation. In addition, recent BS-integrated nanomedicines have been surveyed, chiefly size-tunable cholate nanoparticles, BS-lecithin mixed micelles, bilosomes, probilosomes, and surface-engineered bilosomes. A greater emphasis has been laid on nanosystems for vaccine and cancer therapy. The comparative advantages of BS-integrated nanomedicines over conventional nanocarriers have been noted. Paradoxical effects, current pitfalls, future perspectives, and opinions have also been outlined.

Clonorchis sinensis acetoacetyl-CoA thiolase: identification and characterization of its potential role in surviving in the bile duct

BACKGROUND

Clonorchis sinensis (C. sinensis) inhabits in bile duct of the host. However, the mechanisms involved in why C. sinensis can survive in the bile environment containing lipids have not yet been explored. In this study, C. sinensis acetoacetyl-CoA thiolase (CsACAT), a member of the thiolase family which has a key role in the beta oxidation pathway of fatty acid production, was identified and characterized to understand its potential role in adapting to the bile environment.

METHODS

The encoding sequence, conserved domains and spatial structure of CsACAT were identified and analyzed by bioinformatic tools. Recombinant CsACAT (rCsACAT) was obtained using a procaryotic expression system. The expression pattern of CsACAT was confirmed by quantitative real-time PCR, western blotting, and immunofluorescence. Gradients of lecithin were then set to culture C. sinensis adults in vitro and the survival rate of C. sinensis was analyzed, as well as the expression level and enzymatic activity of CsACAT in different lipid environments. Hypercholesteremia rabbit models were established by feeding with a hyperlipidemic diet and then infected intragastrically with C. sinensis. One and a half months later, the worm burdens and the expression level of CsACAT was detected.

RESULTS

CsACAT was confirmed to be a member of the thiolase family and present in the excretory/secretory proteins of C. sinensis. CsACAT was specifically localized at the vitellarium and sub-tegumental muscle layer in adult worms. The mRNA level of CsACAT in eggs was higher than those in adult worms and metacercariae. When adult worms were cultured with higher concentration of lecithin, the expression level and enzyme activity of CsACAT were up-regulated. The survival rate of adult worms was higher than control group. More adult worms were recovered from hypercholesteremia rabbit models. The expression level of CsACAT in these worms was higher than control group.

CONCLUSIONS

Our results implied that C. sinensis might sense lipid levels and survive better in the bile environment with higher lipid levels. C. sinensis might modulate the expression and enzymatic activity of CsACAT, an enzyme involved in fatty acid metabolism, for energy or physical requirements to adapt to the host.

Minimal intestinal epithelial cell toxicity in response to short- and long-term food-relevant inorganic nanoparticle exposure

Toxicity of commercial nanoparticles of titania, silica, and zinc oxides is being investigated in this in vitro study. Particles of these compositions are found in many food items, and thus this study is directed toward particle behavior in simulated digestion media and their interaction with intestinal epithelial cell line C2BBe1, a clone of Caco-2 cells, originally isolated from a human colon cancer. Even though the primary particle size of all three particles was below 50 nm, the particles appeared as aggregates in culture media with a negatively charged surface. In the presence of pepsin (pH 2), the charge on the titania became positive, and silica was almost neutral and aggregated extensively, whereas ZnO dissolved. For silica and titania, treatment with simulated intestinal digestive solution led to a strongly negatively charged surface and particle sizes approaching values similar to those in media. On the basis of infrared spectroscopy, we concluded that the surface of silica and titania was covered with bile salts/proteins after this treatment. Transmission electron microscopy indicated that the C2BBe1 cells internalized all three particles. Toxicity assays included investigation of necrosis, apoptosis, membrane damage, and mitochondrial activity. Titania and SiO₂ particles suspended in media at loading levels of 10 μg/cm² exhibited no toxicity. With ZnO at the same loading level, mild toxicity was observed based only on the LDH assay and decrease of mitochondrial activity and not necrosis or apoptosis. Titania particles exposed to the simulated digestion media exhibited mild toxicity based on decrease of mitochondrial activity, likely due to transport of toxic bile salts via adsorption on the particle surface.

Photophysical behavior of 8-anilino-1-naphthalenesulfonate in vesicles of pulmonary surfactant dipalmitoylphosphatidylcholine (DPPC) and its sensitivity toward the bile salt-vesicle interaction

The photophysical behavior of 8-anilino-1-naphthalenesulphonate (ANS) in vesicles of dipalmitoylphosphatidylcholine (DPPC), a pulmonary surfactant, has been carried out in a detailed manner. ANS shows notable variations in fluorescence intensity, lifetime, and anisotropy parameters as it gets into the vesicle. It was found that ANS partitions well into the DPPC bilayer membrane with an estimated partition coefficient of ~2.0 × 10(5). Among the various fluorescence parameters of ANS, fluorescence anisotropy was found to be most responsive to the temperature induced phase change of the bilayer membrane. These interesting fluorescence parameters of ANS were then used to study the hydration of lipid bilayer membrane by submicellar concentration of bile salts. From the steady-state fluorescence intensity and dynamic fluorescence lifetime analyses it is clear that ANS is able to probe the submicellar concentration (≤1 mM) of bile salt induced hydration of lipid bilayer membrane that accompanies expulsion of ANS from the bilayer to the aqueous bulk phase. Lower-temperature shift in the phase transition of DPPC bilayer indicates that fluorescence anisotropy of ANS is sensitive enough to the bile salt induced perturbation in the packed acyl chains of DPPC bilayer and modification in the membrane fluidity. In presence of sodium deoxycholate (NaDC) and sodium cholate (NaC) in DPPC vesicles, ANS experiences restriction in rotational mobility which is evident from the variation in steady-state fluorescence anisotropy and fluorescence anisotropy decay parameters.

Liposomes containing bile salts as novel ocular delivery systems for tacrolimus (FK506): in vitro characterization and improved corneal permeation

The objective of this study was to investigate the potential of liposomes containing bile salts as an ophthalmic delivery system for tacrolimus to improve corneal permeability. Liposomes containing bile salts, including sodium taurocholate, sodium deoxycholate, and sodium glycocholate, were produced by the thin-film dispersion method with a particle size of approximately 100 nm and an entrapment efficiency of more than 90%. Less than 5% tacrolimus was released from conventional liposomes and from liposomes containing sodium taurocholate, sodium deoxycholate, or sodium glycocholate over 12 hours. The cellular uptake of conventional liposomes was significantly higher than that of liposomes containing bile salts. However, liposomes containing bile salts exerted a 3–4-fold increase of tacrolimus in ex vivo corneal transport of tacrolimus compared with conventional liposomes. When rabbit eyes were treated with a DiI perchlorate-loaded liposome suspension, liposomes containing bile salts showed fast and sustained penetration across the cornea. Unfortunately, liposomes containing sodium deoxycholate caused toxicity or irritation to both spontaneously derived human corneal epithelial cells and the rabbit cornea. Therefore, liposomes containing sodium taurocholate and sodium glycocholate are potential carriers in ocular drug delivery systems, given their low toxicity and vastly improved permeability.