Deoxycholate-hydrogels: novel drug carrier systems for topical use

Biomedical applications of functional hydrogels: Innovative developments, relevant clinical trials and advanced products

Functional hydrogels are used for numerous biomedical applications such as tissue engineering, wound dressings, lubricants, contact lenses and advanced drug delivery systems. Most of them are based on synthetic or natural polymers forming a three-dimensional network that contains aqueous media. Among synthetic polymers, poly(meth)acrylates, polyethyleneglycols, poly(vinylalcohols), poly(vinylpyrrolidones), PLGA and poly(urethanes) are of high relevance, whereas natural polymers are mainly polysaccharides such as hyaluronic acid, alginate or chitosan and proteins such as albumin, collagen or elastin. In contrast to most synthetic polymers, natural polymers are biodegradable. Both synthetic and natural polymers are often chemically modified in order to improve or induce favorable properties and functions like high mechanical strength, stiffness, elasticity, high porosity, adhesive properties, in situ gelling properties, high water binding capacity or drug release controlling properties. Within this review we provide an overview about the broad spectrum of biomedical applications of functional hydrogels, summarize innovative approaches, discuss the concept of relevant functional hydrogels that are in clinical trials and highlight advanced products as examples for successful developments.

Exploring Biofilm-Related Traits and Bile Salt Efficacy as Anti-Biofilm Agents in MDR Acinetobacter baumannii

Acinetobacter baumannii has been designated as a critical priority pathogen by the World Health Organization for the development of novel antimicrobial agents. This study aimed to investigate both the phenotypic and genotypic traits of multidrug-resistant (MDR) A. baumannii strains, along with the effects of natural bile salts on biofilm formation. The research analyzed phenotypic traits, including autoaggregation, hydrophobicity, twitching motility, lectin production, and biofilm formation, as well as genotypic traits such as the presence of bap and blaPER-1 genes in twenty wound and eight environmental MDR A. baumannii isolates. While all strains were identified as good biofilm producers, no statistically significant correlation was detected between the examined traits and biofilm formation. However, differences in biofilm production were observed between environmental and wound isolates. The natural bile salts Na-cholate, Na-deoxycholate, and Na-chenodeoxycholate demonstrated effective anti-A. baumannii activity (MIC = 0.25-10 mg mL-1), with significant anti-biofilm effects. Na-deoxycholate and Na-chenodeoxycholate inhibited 94-100% of biofilm formation at super-MIC concentrations (8-32 mg mL-1). This study underscores the urgent need for innovative strategies to combat antibiotic resistance and biofilm formation in A. baumannii, highlighting the potential of natural bile salts as promising biofilm inhibitors and encouraging further research into their modification and combination with other antimicrobials.

Self-Healing Hydrogel Resulting from the Noncovalent Interaction between Ropivacaine and Low-Molecular-Weight Gelator Sodium Deoxycholate Achieves Stable and Endurable Local Analgesia in Vivo

Regional analgesia based on the local anesthetic ropivacaine plays a crucial role in postoperative pain management and recovery; however, the short duration of analgesia limits its clinical potential. Various drug delivery systems such as microparticles and lipid carriers have been used to prolong the analgesic effect, yet most of them are prone to abrupt release from the site of administration or have poor analgesic effects of less than 48 h, which fail to meet the needs of postoperative analgesia. In this study, a low-molecular-weight gelator sodium deoxycholate-based hydrogel loaded with ropivacaine (DC-ROP gel) was designed for long-acting analgesia. The noncovalent interaction between ropivacaine and sodium deoxycholate helps to improve the stability and sustained release performance of the gel. This internal drug-binding hydrogel also avoids experiencing the burst release effect commonly seen in polymer hydrogels previously reported for the slow release of local anesthetics. DC-ROP gel exhibited the dual advantages of self-healing after compression and long-term controlled release. In mice with inflammatory pain, DC-ROP gel achieved peripheral nerve block for more than 1 week after a single injection. Histological and blood biochemical analyses confirmed that the DC-ROP gel did not produce systemic toxicity, and cytotoxicity experiments demonstrated that the DC-ROP gel resulted in low irritation. These results suggest that DC-ROP gel provides a promising strategy for local anesthetics in long-term postoperative pain management, broadening the potential of bile salt-based low-molecular-weight hydrogels for drug delivery.

Novel Vesicular Bilosomal Delivery Systems for Dermal/Transdermal Applications

The application of therapeutically active molecules through the dermal/transdermal route into the skin has evolved as an attractive formulation strategy in comparison to oral delivery systems for the treatment of various disease conditions. However, the delivery of drugs across the skin is limited due to poor permeability. Dermal/transdermal delivery is associated with ease of accessibility, enhanced safety, better patient compliance, and reduced variability in plasma drug concentrations. It has the ability to bypass the first-pass metabolism, which ultimately results in steady and sustained drug levels in the systemic circulation. Vesicular drug delivery systems, including bilosomes, have gained significant interest due to their colloidal nature, improved drug solubility, absorption, and bioavailability with prolonged circulation time for a large number of new drug molecules. Bilosomes are novel lipid vesicular nanocarriers comprising bile salts, such as deoxycholic acid, sodium cholate, deoxycholate, taurocholate, glycocholate or sorbitan tristearate. These bilosomes are associated with high flexibility, deformability, and elasticity attributed to their bile acid component. These carriers are advantageous in terms of improved skin permeation, increased dermal and epidermal drug concentration, and enhanced local action with reduced systemic absorption of the drug, resulting in reduced side effects. The present article provides a comprehensive overview of the biopharmaceutical aspects of dermal/transdermal bilosome delivery systems, their composition, formulation techniques, characterization methods, and applications.

In vitro synergy between sodium deoxycholate and furazolidone against enterobacteria

Background

Antimicrobial combinations have been proven as a promising approach in the confrontation with multi-drug resistant bacterial pathogens. In the present study, we identify and characterize a synergistic interaction of broad-spectrum nitroreductase-activated prodrugs 5-nitrofurans, with a secondary bile salt, sodium deoxycholate (DOC) in growth inhibition and killing of enterobacteria.

Results

Using checkerboard assay, we show that combination of nitrofuran furazolidone (FZ) and DOC generates a profound synergistic effect on growth inhibition in several enterobacterial species including Escherichia coli, Salmonella enterica, Citrobacter gillenii and Klebsiella pneumoniae. The Fractional Inhibitory Concentration Index (FICI) for DOC-FZ synergy ranges from 0.125 to 0.35 that remains unchanged in an ampicillin-resistant E. coli strain containing a β-lactamase-producing plasmid. Findings from the time-kill assay further highlight the synergy with respect to bacterial killing in E. coli and Salmonella.

We further characterize the mechanism of synergy in E. coli K12, showing that disruption of the tolC or acrA genes that encode components of multidrug efflux pumps causes, respectively, a complete or partial loss, of the DOC-FZ synergy. This finding indicates the key role of TolC-associated efflux pumps in the DOC-FZ synergy. Overexpression of nitric oxide-detoxifying enzyme Hmp results in a three-fold increase in FICI for DOC-FZ interaction, suggesting a role of nitric oxide in the synergy. We further demonstrate that DOC-FZ synergy is largely independent of NfsA and NfsB, the two major activation enzymes of the nitrofuran prodrugs.

Conclusions

This study is to our knowledge the first report of nitrofuran-deoxycholate synergy against Gram-negative bacteria, offering potential applications in antimicrobial therapeutics. The mechanism of DOC-FZ synergy involves FZ-mediated inhibition of TolC-associated efflux pumps that normally remove DOC from bacterial cells. One possible route contributing to that effect is via FZ-mediated nitric oxide production.

Deoxycholic acid and l-Phenylalanine enrich their hydrogel properties when combined in a zwitterionic derivative

HYPOTHESIS

Sodium Deoxycholate (NaDC) and Phenylalanine (Phe) are important biological hydrogelators. NaDC hydrogels form by lowering the pH or by increasing the ionic strength. Phe gels form from saturated solution by thermal induction and slow kinetics. The resulting gels hold great potential in medicine and biology as drug carriers and models for fundamental self-assembly in pathological conditions. Based on this background it was hypothesized that a Phe substituted NaDC could provide a molecule with expanded gelling ability, merging those of the precursors.

EXPERIMENTS

We coupled both building blocks in a zwitterionic derivative bearing a Phe residue at the C3 carbon of NaDC. The specific zwitterionic structure, the concurrent use of Ca²⁺ ions for the carboxyl group coordination and the pH control generate conditions for the formation of hydrogels. The hydrogels were analyzed by combining UV and circular dichroism spectroscopies, rheology, small angle X-ray scattering and atomic force microscopy.

FINDINGS

Hydrogel appearance occurs in conditions that are uncovered in the case of the pure Phe and NaDC: self-standing gels form instantaneously at room temperature, in the 10-12 pH range and down to concentration of 0.17 wt%. Both thixotropic and shake resistant gels can form depending on the derivative concentration. The gels show an uncommon thermal stability in the scanned range of 20-60 °C. The reported system concurrently enriches the hydrogelation properties of two relevant building blocks. We anticipate some potential applications of such gels in materials science where coordination of metal ions can be exploited for templating inorganic nanostructures.

Stepwise Aggregation of Cholate and Deoxycholate Dictates the Formation and Loss of Surface-Available Chirally Selective Binding Sites

Bile salts are facially amphiphilic, naturally occurring chemicals that aggregate to perform numerous biochemical processes. Because of their unique intermolecular properties, bile salts have also been employed as functional materials in medicine and separation science (e.g., drug delivery, chiral solubilization, purification of single-walled carbon nanotubes). Bile micelle formation is structurally complex, and it remains a topic of considerable study. Here, the exposed functionalities on the surface of cholate and deoxycholate micelles are shown to vary from one another and with the micelle aggregation state. Collectively, data from NMR and capillary electrophoresis reveal preliminary, primary, and secondary stepwise aggregation of the salts of cholic (CA) and deoxycholic (DC) acid in basic conditions (pH 12, 298 K), and address how the surface availability of chirally selective binding sites is dependent on these sequential stages of aggregation. Prior work has demonstrated sequential CA aggregation (pH 12, 298 K) including a preliminary CMC at ca. 7 mM (no chiral selection), followed by a primary CMC at ca. 14 mM that allows chiral selection of binaphthyl enantiomers. In this work, DC is also shown to form stepwise preliminary and primary aggregates (ca. 3 mM DC and 9 mM DC, respectively, pH 12, 298 K) but the preliminary 3 mM DC aggregate is capable of chirally selective solubilization of the binaphthyl enantiomers. Higher-order, secondary bile aggregates of each of CA and DC show significantly degraded chiral selectivity. Diffusion NMR reveals that secondary micelles of CA exclude the BNDHP guests, while secondary micelles of DC accommodate guests, but with a loss of chiral selectivity. These data lead to the hypothesis that secondary aggregates of DC have an exposed binding site, possibly the 7α-edge of a bile dimeric unit, while secondary CA micelles do not present binding edges to the solution, potentially instead exposing the three alcohol groups on the hydrophilic α-face to the solution.

Release of small bioactive molecules from physical gels

Pharmaceutical drugs with low water solubility have always received great attention within the scientific community. The reduced bioavailability and the need of frequent administrations have motivated the investigation of new drug delivery systems. Within this context, drug carriers that release their payload in a sustained way and hence reduce the administration rate are highly demanded. One interesting strategy to meet these requirements is the entrapment of the drugs into gels. So far, the most investigated materials for such drug-loaded gels are derived from polymers and based on covalent linkages. However, over the last decade the use of physical (or supramolecular) gels derived from low molecular weight compounds has experienced strong growth in this field, mainly due to important properties such as injectability, stimuli responsiveness and ease of synthesis. This review summarizes the use of supramolecular gels for the encapsulation and controlled release of small therapeutic molecules.

Gels with sense: supramolecular materials that respond to heat, light and sound

Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are "smart" gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal-organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo- and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.

Evaluation of two methods for topical application of contrast medium to the pharyngeal and laryngeal region of horses

OBJECTIVE To determine the pharyngeal and laryngeal distribution of radiopaque contrast medium administered orally or via nasopharyngeal catheter to standing horses. ANIMALS 5 healthy adult horses. PROCEDURES A crossover study was conducted. Radiopaque contrast medium (12 mL) was administered orally and via nasopharyngeal catheter to each horse. Pharyngeal and laryngeal distribution of contrast medium was determined by examination of radiographs obtained immediately after administration of contrast medium, compared with those obtained before administration. Regional distribution of contrast medium was graded. Endoscopic examination of the nasopharynx, laryngopharynx, and larynx was performed to confirm radiographic results. RESULTS Examination of radiographs obtained after nasopharyngeal administration revealed contrast medium in the nasopharynx (n = 5), oropharynx (2), laryngopharynx (3), and larynx (5) of the 5 horses. Examination of radiographs obtained after oral administration revealed contrast medium in the oropharynx (n = 4) and larynx (1) of the 5 horses. Endoscopic examination confirmed radiographic findings and was found to be sensitive for detection of contrast medium in the laryngopharynx, whereby detection rates were higher for both administration methods. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that medication administered by use of a nasopharyngeal catheter will result in topical distribution within the nasopharynx, including the dorsal surface of the soft palate, and larynx, although distribution should be evaluated in horses with clinical airway disease to confirm these findings. Oral administration did not result in consistently detectable topical laryngeal distribution but could be used for selected conditions (eg, palatitis).

In Vivo Assessment of Clobetasol Propionate-Loaded Lecithin-Chitosan Nanoparticles for Skin Delivery

The aim of this work was to assess in vivo the anti-inflammatory efficacy and tolerability of clobetasol propionate (CP) loaded lecithin/chitosan nanoparticles incorporated into chitosan gel for topical application (CP 0.005%). As a comparison, a commercial cream (CP 0.05% w/w), and a sodium deoxycholate gel (CP 0.05% w/w) were also evaluated. Lecithin/chitosan nanoparticles were prepared by self-assembling of the components obtained by direct injection of soybean lecithin alcoholic solution containing CP into chitosan aqueous solution. Nanoparticles obtained had a particle size around 250 nm, narrow distribution (polydispersity index below 0.2) and positive surface charge, provided by a superficial layer of the cationic polymer. The nanoparticle suspension was then loaded into a chitosan gel, to obtain a final CP concentration of 0.005%. The anti-inflammatory activity was evaluated using carrageenan-induced hind paw edema test on Wistar rats, the effect of formulations on the barrier property of the stratum corneum were determined using transepidermal water loss measurements (TEWL) and histological analysis was performed to evaluate the possible presence of morphological changes. The results obtained indicate that nanoparticle-in-gel formulation produced significantly higher edema inhibition compared to other formulations tested, although it contained ten times less CP. TEWL measurements also revealed that all formulations have no significant disturbance on the barrier function of skin. Furthermore, histological analysis of rat abdominal skin did not show morphological tissue changes nor cell infiltration signs after application of the formulations. Taken together, the present data show that the use of lecithin/chitosan nanoparticles in chitosan gel as a drug carrier significantly improves the risk-benefit ratio as compared with sodium-deoxycholate gel and commercial cream formulations of CP.

Biocompatible hydrogelators based on bile acid ethyl amides

Four novel bile acid ethyl amides were synthetized using a well-known method. All the four compounds were characterized by IR, SEM, and X-ray crystal analyses. In addition, the cytotoxicity of the compounds was tested. Two of the prepared compounds formed organogels. Lithocholic acid derivative 1 formed hydrogels as 1% and 2% (w/v) in four different aqueous solutions. This is very intriguing regarding possible uses in biomedicine.

Supramolecular hydrogelation with bile acid derivatives: structures, properties and applications

Bile acid derivatives can form molecular hydrogels that may be useful for drug delivery, tissue engineering and nanotemplating.

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.

Sodium Deoxycholate Hydrogels: Effects of Modifications on Gelation, Drug Release, and Nanotemplating

In the present study, sodium deoxycholate (NaDC) was used to produce gelation of tris(hydroxymethyl)amino-methane (TRIS) solutions above, below, and near the pKa of NaDC, respectively, which yielded a neutral gelator, a charged gelator, and a mixture of each. Impacts of ionic interactions on gel formation were studied in detail and showed that pH can be used to modify many hydrogel properties including sol-gel temperature, crystallinity, and mechanical strength. Several formulations yielded a unique rheological finding of two stable regions of elastic modulus. The release of a small molecule has been investigated under different hydrogel conditions and at variable shear rate, suggesting utility as a drug-delivery vehicle. It was also observed that pH modification of the hydrogels affected nanoparticle formation. Nanoparticles derived from a Group of Uniform Materials Based on Organic Salts (nanoGUMBOS), specifically cyanine-based NIR dyes, were templated within the hydrogel network for potential applications in tissue imaging. These nanoGUMBOS were found to be size-tunable, although material-dependent. Further understanding of NaDC/TRIS gelation has broadened the tunability and multidimensional applications of these tailored hydrogel systems.

Antiinflammatory effects of Viola tricolor gel in a model of sunburn in rats and the gel stability study

ETHNOPHARMACOLOGICAL RELEVANCE

Viola tricolor, popularly known as heartsease has been empirically used in several skin disorders, including burns.

AIM OF THE STUDY

The objective of this study was investigate the antinociceptive and antiinflammatory effect of a gel containing extract of Viola tricolor flowers on thermal burn induced by UVB irradiation and to perform gel stability study.

METHODS

The antinociceptive and antiinflammatory effect were evaluated by static and dynamic mechanical allodynia model, paw edema, and neutrophilic cell infiltration. Metabolites compounds were quantified by HPLC. The gel stability study was performed analyzing organoleptical aspects, besides pH, viscosity, and quantification of rutin by HPLC.

RESULTS

In the results were evidenced changes in threshold in statical and dynamic mechanical allodynia (I(max)=100 ± 10% and 49 ± 10%, respectively), paw edema (I(max)=61 ± 6%), and myeloperoxidase activity (I(max)=89 ± 5%). Such effects may be attributed, in part, to rutin, salicylic and chlorogenic acids, and others compounds found in this species. No important changes were detected in the stability study, in all aspects analyzed in temperature below 25 °C.

CONCLUSION

These findings suggest that Viola tricolor gel has an antinociceptive and antiinflammatory effect in the ultraviolet-B-induced burn, since maintain the temperature below 25 °C.

New polyfluorothiopropanoyloxy derivatives of 5β-cholan-24-oic acid designed as drug absorption modifiers

A series of final six propanoyloxy derivatives of 5β-cholan-24-oic acid (tridecafluoroctylsulfanyl- and tridecafluoroctylsulfinylethoxycarbonylpropanoyloxy derivatives) as potential drug absorption promoters (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (logS), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukaemia cell line and breast adenocarcinoma cell line. One compound showed high selective cytotoxicity against human skin fibroblast cells and another compound possessed high cytotoxicity against breast adenocarcinoma cell line and skin fibroblast cells. Only one compound expressed anti-proliferative effect on leukaemia and breast adenocarcinoma cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37μM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and penetration enhancement effect are discussed in this article.

New propanoyloxy derivatives of 5β-cholan-24-oic acid as drug absorption modifiers

A series of final twelve propanoyloxy derivatives of 5β-cholan-24-oic acid (O-propanoyl derivatives of cholic acid) as potential drug absorption modifiers (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by 1H NMR, 13C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (log S), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukemia cell line and breast adenocarcinoma cell line. One compound showed selective cytotoxicity against human skin fibroblast cells and another compound possessed the highest cytotoxicity against all the tested cell lines. Only one compound expressed anti-proliferative effect on leukemia cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37 μM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effect are discussed in this article.

A novel method for preparing silver nanoparticle-hydrogel nanocomposites via pH-induced self-assembly

We present a novel and facile method to fabricate the silver nanoparticle (AgNP)-sodium deoxycholate (NaDOC) hybrid hydrogel from the NaDOC-stablized AgNP colloidal hydrosol via the pH-induced self-assembly.

A novel method to chemically bind thiazolidine-2,4-dione through cross-linked chitosan nanoparticles using malanodialdehyde as a cross-linker

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications because of its biocompatibility, high charge density, nontoxicity and mucoadhesion. It has been shown that it not only improves the dissolution of poorly soluble drugs but also exerts a significant effect on fat metabolism in the body. Gel formation can be obtained by interactions of chitosans with low molecular counterions such as polyphosphates, sulfates, and cross-linkers. This gelling property of chitosan allows a wide range of applications such as the coating of pharmaceuticals and food products, gel entrapment of biochemicals, plant embryos, whole cells, microorganisms, and algae. This manuscript is an insight into the exploitation of its properties for microencapsulating drugs. Herein, we report a novel method to chemically bind thiazolidine-2,4-dione through cross-linked chitosan nanoparticles using malanodialdehyde as a new cross-linker and well characterized by FT-IR, NMR, TGA, DSC, powder X-ray diffraction, TEM, and cyclic voltametry.

Investigation of new acyloxy derivatives of cholic acid and their esters as drug absorption modifiers

Skin penetration enhancers are used in the formulation of transdermal delivery systems for drugs that are otherwise not sufficiently skin-permeable. Intestinal absorption promoters/enhancers are used as excipients in oral formulations of poorly oral-bioavailable drugs. Series of fourteen acyloxy derivatives of 5β-cholic acid as potential drug absorption modifiers was generated by multistep synthesis. The synthesis of all newly prepared compounds is presented here. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (R(M)) was determined. The hydrophobicity (logP) and solubility (logS) of the studied compounds were also calculated using two commercially available programs. All the target compounds were tested for their in vitro transdermal penetration activity and as potential intestinal absorption enhancers. The anti-proliferative activity of all the final compounds was also assessed against the human cancer cell lines: T-lymphoblastic leukemia cell line and the breast adenocarcinoma cell line. Their cytotoxicity was also evaluated against the normal human skin fibroblast cells. Two compounds showed anti-proliferative effect on cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC(50)>37 μM), indicating they would have low cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effects are discussed in this article.

Microemulsions as vehicles for topical administration of voriconazole: formulation and in vitro evaluation

This work was undertaken to investigate microemulsion (ME) as a topical delivery system for the poorly water-soluble voriconazole. Different ME components were selected for the preparation of plain ME systems with suitable rheological properties for topical use. Two permeation enhancers were incorporated, namely sodium deoxycholate or oleic acid. Drug-loaded MEs were evaluated for their physical appearance, pH, rheological properties and in vitro permeation studies using guinea pig skin. MEs based on polyoxyethylene(10)oleyl ether (Brij 97) as the surfactant showed pseudoplastic flow with thixotropic behavior and were loaded with voriconazole. Jojoba oil-based MEs successfully prolonged voriconazole release up to 4 h. No significant changes in physical or rheological properties were recorded on storage for 12 months at ambient conditions. The presence of permeation enhancers favored transdermal rather than dermal delivery. Sodium deoxycholate was more effective than oleic acid for enhancing the voriconazole permeation. Voriconazole-loaded MEs, with and without enhancers, showed significantly better antifungal activity against Candida albicans than voriconazole supersaturated solution. In conclusion, the studied ME formulae could be promising vehicles for topical delivery of voriconazole.

Deoxycholate hydrogels of betamethasone-17-valerate intended for topical use: In vitro and in vivo evaluation

The aim of this study was to evaluate the suitability of sodium-deoxycholate (Na-DOC) gels containing betamethasone-17-valerate (BMV) for topical application. The gels were characterized for rheological and textural properties. The in vitro flux of BMV from Na-DOC gels across rat skin was 2.5 (0.05% gel) and 8.5 times (0.1% gel) higher compared to the commercial cream (0.1%), respectively. The pharmacodynamic responses after in vivo topical application in rats were also determined. A significant correlation between anti-inflammatory activity and in vitro permeation of BMV was observed. Na-DOC gels produced significantly higher edema inhibition compared to commercial cream at all time intervals. Finally, according to the results of histology studies, Na-DOC gel has no irritant effect on the skin. In conclusion, Na-DOC gel formulation could be suggested as a promising alternative system for the topical application of BMV.

Simple esters of cholic acid as potent organogelators: direct imaging of the collapse of SAFINs

Unusual gelation of a number of organic solvents by allyl cholate and other simple esters of cholic acid is reported. These gels were characterized by SEM, AFM, polarizing optical microscopy (POM), X-ray powder diffraction and other techniques. Electron micrographs of the xerogels revealed the presence of highly entangled 3D fibrillar networks. Direct imaging of the collapse of SAFINs and their thermal stability were performed using variable temperature polarizing optical microscopy (POM).

Total flavonoids quantification from O/W emulsion with extract of Brazilian plants

A new derivative spectrophotometric (DS) method was proposed and validated for quantification of total flavonoids from in O/W emulsion with polyacrylamide (and) C13-14 isoparaffin (and) laureth-7 containing Catuaba (Trichilia catigua Adr. Juss) (and) Marapuama (Ptychopetalum olacoides Bentham) extract. DS method was optimized to perform the assay in most favorable conditions. Linearity, specificity and selectivity, recovery (Rc, %), precision (R.S.D., %), accuracy (E, %), detection (LOD, microg ml(-1)) and quantification limits (LOQ, microg ml(-1)) were established for method validation. First-derivative at 388.0 nm (zero-to-peak; amplitude= +/- 0.12; wavelength range= 300.0-450.0 nm and Deltalambda = 4 nm) offered linearity for rutin concentrations ranging from 10.0 to 60.0 microg ml(-1) in ethanol 99.5%. Second-derivative provided to be unsuitable for interval evaluation obtaining unacceptable accuracy. Analytical method was validated for first-derivative, according to the experimental results: correlation coefficient (r = 0.9999); specificity to total flavonoids quantification, expressed in rutin, at wavelength 388.0 nm and selectivity with elimination of interference from matrix; Rc = 108.78%; intra- and inter-run precision (1.30-3.65% and 3.48-4.68%), and intra- and inter-run accuracy (100.00-112.19% and 101.25-118.44%); LOD = 0.62 microg ml(-1) and LOQ = 1.86 microg ml(-1).

Micellar aggregates and hydrogels from phosphonobile salts

The aggregation properties of novel bile acid analogs-phosphonobile salts (PBS)-have been studied. The critical micellar concentration of 23 and 24-phosphonobile salts were measured using fluorescence and 31P NMR methods. All the ten synthesized phosphonobile salts formed gels at different pH ranges in water. The pH range at which individual PBSs could gelate water was narrow and influenced by the number and conformation of hydroxyl groups. A reversible thermochromic system has been developed (with 23-phosphonodeoxycholate at pH 3.3), which changes color upon gelation. The investigation of the first hydrogels derived from trihydroxy bile acid analogs 1 and 6 was made using fluorescence, 31P NMR, X-ray crystallography, circular dichroism and SEM. The present studies reveal that the gel network consists of a chiral, fibrous structure possessing hydrophobic interiors.

Water Vapor Adsorption Behavior of Sodium Deoxycholate Anhydrous Forms

Pseudopolymorphism of sodium deoxycholate (NaDC) was investigated. Intact NaDC (dihydrate) was dried at 60 degrees C under reduced pressure resulting an anhydrous amorphous phase. On the other hand, intact NaDC was altered to an anhydrous crystalline form by heating at 200 degrees C. The water vapor adsorption and desorption isotherms of dehydrated NaDCs were determined using an automatic gravimetric water vapor adsorption analyzer. In the case of NaDC dehydrated at 60 degrees C, the weight was increased in rising relative humidity and it was transformed into the NaDC tetrahydrate above 60% RH, which was identified by TG/DTA and powder X-ray diffraction. During the water vapor adsorption process of the sample dehydrated at 200 degrees C, the NaDC dihydrate was obtained in the range of 50 to 70% RH and then transformed into the NaDC octahydrate above 85% RH. The NaDC octahydrate was characterized by TG/DTA and powder X-ray diffraction for the first time. During the desorption process, the octahydrate was changed to the tetrahydrate between 80 and 40% RH.