Solid Self-Nanoemulsifying Drug Delivery Systems of Furosemide: In Vivo Proof of Concept for Enhanced Predictable Therapeutic Response.

Liquid self-nano emulsifying drug delivery systems (SNEDDS) of furosemide (FSM) have been explored as a potential solution for enhancing solubility and permeability but are associated with rapid emulsification, spontaneous drug release, and poor in vivo correlation. To overcome the shortcoming, this study aimed to develop liquid and solid self-emulsifying drug delivery systems for FSM, compare formulation dynamics, continue in vivo therapeutic efficacy, and investigate the advantages of solidification. For this purpose, liquid SNEDDS (L-SEDDS-FSM) were formed using oleic acid as an oil, chremophore EL, Tween 80, Tween 20 as a surfactant, and PEG 400 as a co-surfactant containing 53 mg/mL FSM. At the same time, solid SNEDDS (S-SEDDS-FSM) was developed by adsorbing liquid SNEDDS onto microcrystalline cellulose in a 1:1 ratio. Both formulations were evaluated for size, zeta potential, lipase degradation, and drug release. Moreover, in vivo diuretic studies regarding urine volume were carried out in mice to investigate the therapeutic responses of liquid and solid SNEDDS formulations. After dilution, L-SEDDS-FSM showed a mean droplet size of 115 ± 4.5 nm, while S-SEDDS-FSM depicted 116 ± 2.6 nm and zeta potentials of -5.4 ± 0.55 and -6.22 ± 1.2, respectively. S-SEDDS-FSM showed 1.8-fold reduced degradation by lipase enzymes in comparison to L-SEDDS-FSM. S-SEDDS-FSM demonstrated a sustained drug release pattern, releasing 63% of the drug over 180 min, in contrast to L-SEDDS-FSM, exhibiting 90% spontaneous drug release within 30 min. L-SEDDS-FSM exhibited a rapid upsurge in urine output (1550 ± 56 µL) compared to S-SEDDS-FSM, showing gradual urine output (969 ± 29 µL) till the 4th h of the study, providing sustained urine output yet a predictable therapeutic response. The solidification of SNEDDS effectively addresses challenges associated with spontaneous drug release and precipitation observed in liquid SNEDDS, highlighting the potential benefits of solid SNEDDS in improving the therapeutic response of furosemide.

Formulation and characterization of thiolated chitosan/polyvinyl acetate based microneedle patch for transdermal delivery of dydrogesterone.

Microneedle patches are promising transdermal drug delivery platforms with minimal invasiveness in a painless manner. Microneedle patch could be a promising alternate route for delivery of drugs having poor solubility and low bioavailability. This research work therefore, aimed to develop and characterize microneedle patch of thiolated chitosan (TCS) and polyvinyl acetate (PVA) for the systemic delivery of dydrogesterone (DYD). TCS-PVA-based microneedle patch was fabricated with 225 needles having a length of 575 µm with the sharp pointed end. Different ratios of TCS-PVA-based patch were employed to investigate the effects of mechanical tensile strength and percentage elongation. The scanning electron microscopy (SEM) revealed intact sharp-pointed needles. In vitro dissolution studies of microneedle patch (MN-P) were carried out by modified Franz-diffusion cell revealing the sustained release of DYD 81.45 ± 2.768 % at 48 hrs as compared to pure drug that showed 96.7 ± 1.75 % at 12 hrs. The transport of DYD (81%) across skin reaching the systemic circulation was evaluated through ex vivo permeation studies of MN-P. The skin penetration study through the parafilm M method showed good penetration with no deformation and breakage of needles along with no visible signs of skin irritation. Histological study of mice skins clearly showed the deeper penetration of needles into the skin. In summary, as-prepared MN-P show potential in developing an effective transdermal delivery system for DYD.

Formulation of ciprofloxacin-loaded oral self-emulsifying drug delivery system to improve the pharmacokinetics and antibacterial activity.

This study aims to increase the aqueous solubility of ciprofloxacin (CPN) to improve oral bioavailability. This was carried out by formulating a stable formulation of the Self-Emulsifying Drug Delivery System (SEDDS) using various ratios of lipid/oil, surfactant, and co-surfactant. A pseudo-ternary phase diagram was designed to find an area of emulsification. Eight formulations (F1-CPN-F8-CPN) containing oleic acid oil, silicone oil, olive oil, castor oil, sunflower oil, myglol oil, polysorbate-80, polysorbate-20, PEO-200, PEO-400, PEO-600, and PG were formulated. The resultant SEDDS were subjected to thermodynamic study, size, and surface charge studies to improve preparation. Improved composition of SEDDS F5-CPN containing 40% oil, 60% polysorbate-80, and propylene glycol (Smix ratio 6: 1) were thermodynamically stable emulsions having droplet size 202.6 nm, charge surface -13.9 mV, and 0.226 polydispersity index (PDI). Fourier transform infra-red (FT-IR) studies revealed that the optimized formulation and drug showed no interactions. Scanning electron microscope tests showed the droplets have an even surface and spherical shape. It was observed that within 5 h, the concentration of released CPN from optimized formulations F5-CPN was 93%. F5-CPN also showed a higher antibacterial action against S. aurous than free CPN. It shows that F5-CPN is a better formulation with a good release and high antibacterial activity.

Assessment of Antimicrobial Potential of Plagiochasma rupestre Coupled with Healing Clay Bentonite and AGNPS.

The impact of individual component, i.e., plant extract (Plagiochasma rupestre), biosynthesized silver nanoparticles (AgNPs), and healing clay (bentonite) as antimicrobial agent is reported but their combined effect as a ternary system is a new approach. This study is aimed at investigating the impact of the proposed ternary system against selected human pathogens. AgNPs were synthesized by using Plagiochasma rupestre extract (aqueous) as reducing agent and neutral polymer (PVP) as stabilizer. The morphology, size, and structural properties of synthesized AgNPs were determined with XRD and SEM analysis which showed spherical monomodal particles with an average particle size of 25.5 nm. The antibacterial and antifungal activities of the individual and nanoternary system were investigated. The phytochemical screening of plant extract showed the presence of alkaloids, flavonoids, phenol, and glycosides in methanol extract as compare to aqueous and acetone extract. The antimicrobial activities of crude extracts of Plagiochasma rupestre with AgNPs and bentonite clay were studied as an appropriate candidate for treatment of microbial infections, especially bacterial and fungal diseases. The antioxidant activity of Plagiochasma rupestre aqueous extract and nanoparticles was assessed by (DPPH) free radical, and absorbance was checked at 517 nm. Crude extract has inhibitory effect towards bacteria and fungi, and bentonite clay also showed some degree of antimicrobial resistance. Strategy can be efficiently applied for future engineering and medical. The nanoternary systems showed 3 and 3.5 times higher antibacterial and antifungal activity, respectively, in comparison to Plagiochasma rupestre and bentonite clay, individually.

Development of mucus-penetrating iodine loaded self-emulsifying system for local vaginal delivery.

The major goal of this project was to formulate iodine-based self nano-emulsifying drug delivery system to provide improve antimicrobial activity and enhanced mucosal residence time via mucus penetration. Iodine SNEDDS (Self nano-emulsifying drug delivery system) with different concentration were formulated using castor oil as the oil phase, cremophor ethoxylated (CrEL) as a surfactant and after screening a number of vehicles, PEG 400 was employed as co-surfactant. Self-emulsification time, thermodynamic stability tests, robustness to dilution, percent transmittance, droplet size, and drug release were measured. Ternary phase diagrams were plotted to determine the area of emulsification. When compared to the commercial formulation, dissolving experiments revealed that the iodine from the SNEDDS enhanced aqueous solubility. In-vitro iodine release was determined to be around 15% per hour, with muco-adhesive and, muco-penetrating characteristics showing a 38-fold improvement. Furthermore, SNEDDS demonstrated significant antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Similarly, when compared to marketed drugs, in-vitro drug absorption profile from the manufactured SNEDDS shown to be much higher. According to these results iodine containing SNEDDS could be a useful new formulation for iodine mucosal usage.

Polyaminated pullulan, a new biodegradable and cationic pullulan derivative for mucosal drug delivery.

AIM: To prepare new polycationic pullulan derivatives exhibiting highly mucoadhesive and sustained drug release properties. METHODS: Hydroxy groups of pullulan were activated with mesyl chloride followed by conjugation with low-molecular weight polyamines. Pullulan-tris(2-aminoethyl)amine (Pul-TAEA) and pullulan-polyethyleneimine (Pul-PEI) were evaluated regarding swelling behaviour, mucoadhesive properties and potential to control drug release. RESULTS: Pul-TAEA and Pul-PEI exhibited excellent swelling properties at pH 6.8 showing 240- and 370-fold increase in weight. Compared to unmodified pullulan, Pul-TAEA and Pul-PEI displayed 5- and 13.3-fold increased dynamic viscosity in mucus. Mucoadhesion studies of Pul-TAEA and Pul-PEI on intestinal mucosa showed a 6- and 37.8-fold increase in tensile strength, and a 72- and 120-fold increase in mucoadhesion time compared to unmodified pullulan, respectively. Due to additional ionic interactions between cationic groups on polyaminated pullulans and an anionic model drug, a sustained drug release was achieved. CONCLUSIONS: Polyaminated pullulans are promising novel mucoadhesive excipients for mucosal drug delivery.

Thiolated Chitosan Microneedle Patch of Levosulpiride from Fabrication, Characterization to Bioavailability Enhancement Approach.

In this study, a first attempt has been made to deliver levosulpiride transdermally through a thiolated chitosan microneedle patch (TC-MNP). Levosulpiride is slowly and weakly absorbed from the gastrointestinal tract with an oral bioavailability of less than 25% and short half-life of about 6 h. In order to enhance its bioavailability, levosulpiride-loaded thiolated chitosan microneedle patches (LS-TC-MNPs) were fabricated. Firstly, thiolated chitosan was synthesized and characterized by nuclear magnetic resonance (1HNMR) spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Thiolated chitosan has been used in different drug delivery systems; herein, thiolated chitosan has been used for the transdermal delivery of LS. LS-TC-MNPs were fabricated from different concentrations of thiolated chitosan solution. Furthermore, the levosulpiride-loaded thiolated chitosan microneedle patch (LS-TC-MNP) was characterized by FTIR spectroscopic analysis, scanning electron microscopy (SEM) study, penetration ability, tensile strength, moisture content, patch thickness, and elongation test. LS-TC-MNP fabricated with 3% thiolated chitosan solution was found to have the best tensile strength, moisture content, patch thickness, elongation, drug-loading efficiency, and drug content. Thiolated chitosan is biodegradable, nontoxic and has good absorption and swelling in the skin. LS-TC-MNP-3 consists of 100 needles in 10 rows each with 10 needles. The length of each microneedle was 575 µm; they were pyramidal in shape, with sharp pointed ends and a base diameter of 200 µm. The microneedle patch (LS-TC-MNP-3) resulted in-vitro drug release of 65% up to 48 h, ex vivo permeation of 63.6%, with good skin biocompatibility and enhanced in-vivo pharmacokinetics (AUC = 986 µg/mL·h, Cmax = 24.5 µg/mL) as compared to oral LS dispersion (AUC = 3.2 µg/mL·h, Cmax = 0.5 µg/mL). Based on the above results, LS-TC-MNP-3 seems to be a promising strategy for enhancing the bioavailability of levosulpiride.

Is hyaluronic acid the perfect excipient for the pharmaceutical need?

Hyaluronic acid has become an interesting and important polymer as an excipient for pharmaceutical products due to its beneficial properties, like solubility, biocompatibility and biodegradation. To improve the properties of hyaluronic acid, different possibilities for chemical modifications are presented, and the opportunities as novel systems for drug delivery are discussed. This review gives an overview over the production of hyaluronic acid, the possibilities of its chemical modification and the current state of in vitro and in vivo research. Furthermore, market approved and commercially available products are reviewed and derivatives undergoing clinical trials and applying for market approval are shown. In particular, hyaluronic acid has been studied for different administrations in rheumatology, ophthalmology, local anesthetics, cancer treatment and bioengineering of tissues. The present work concludes with perspectives for future administration of pharmaceuticals based on hyaluronic acid.

Thiolated cyclodextrins: Mucoadhesive and permeation enhancing excipients for ocular drug delivery.

Thiolated ß-cyclodextrin (ß-CD) has the potential to enhance mucoadhesive and permeation enhancing properties on ocular mucosa. Thiolated ß-CD was synthesized via replacement of all primary hydroxyl groups on ß-CD backbone by halogen followed by substitution with thiol groups. The structure was confirmed by FT-IR and 1H NMR spectroscopy. Thiolated CD was characterized for hemolytic effect, ocular irritation, solubility enhancement, viscoelastic behavior and mucoadhesive properties. Moreover, the permeation enhancing effect of thiolated oligomer on different ocular tissues including conjunctiva, sclera and cornea was evaluated with sodium fluorescein (Na-Flu) as a marker. Thiolated ß-CD displayed 5360 ± 412 µmol/g thiol groups. The newly synthesized oligomer did not show any hemolytic effect on red blood cells at a concentration of 0.5% (m/v) for an incubation period of 3 h and minimal corneal irritation effects without any inflammation within 72 h. Thiolated ß-CD exhibited a 5.3-fold improved aqueous solubility as compared to the unmodified ß-CD. Thiolated oligomer (0.5% m/v) enhanced the viscosity of mucus up to 6.2-fold within 4 h and provided a 26-fold prolonged ocular residence time due to mucoadhesion. Moreover, 0.5% (m/v) thiolated ß-CD enhanced the permeation of Na-Flu 9.6-, 7.1- and 5.3-fold on conjunctiva, sclera and cornea, respectively. Based on these findings, thiolated ß-CD might be a promising auxiliary agent for ocular drug delivery.

Polyphosphate coatings: A promising strategy to overcome the polycation dilemma.

AIM: It was the aim of this study to develop a zeta potential changing drug delivery system by decorating lipid-based nanocarriers with a polycationic cell penetrating peptide (CPP) and subsequently masking these cationic substructures with polyphosphates. METHODS: In order to anchor the CPP poly-l-lysine (PLL) on the surface of the oily droplets of an o/w nanoemulsion, stearic acid was covalently attached to the peptide. The resulting CPP-decorated oily droplets were coated with phytic acid and tripolyphosphate. The elimination of these polyphosphates due to cleavage by alkaline phosphatase was monitored by the release of monophosphate from the surface of the nanocarriers, by the change in zeta potential and by cellular uptake studies on Caco-2 cells. RESULTS: Polyphosphate coated PLL-decorated nanocarriers exhibited a pronounced conversion of zeta potential from -14.1 mV to +4.2 mV in case of tripolyphosphate coated nanocarriers and from -9.9 mV to -2.6 mV in case of phytic acid coated nanocarriers. The cellular uptake on Caco-2 cells of the polyphosphate coated nanocarriers was 4-fold improved compared to the control nanocarriers. Furthermore, confocal images showed that the majority of nanodroplets distributed in cytoplasm not being internalized into lysosomes. CONCLUSION: Polyphosphate coating of CPP-decorated nanocarriers seems to be a promising and simple strategy to overcome the polycation dilemma.

Thiolated sodium alginate conjugates for mucoadhesive and controlled release behavior of metformin microspheres.

The absorption of BCS III drugs can be improved by inhibiting the P-glycoprotein (P-gp) efflux and by increasing the mucoadhesion of natural polymers. In the present study, an esterification of sodium alginate (SA) with thioglycolic acid (TGA) was applied for the preparation of thiolated sodium alginate (TSA). The Ellman's test was applied to quantify the thiol group and a di-sulphide bond test was performed to confirm any SS linkages. The FTIR, DSC, XRD, 1H NMR and charring point determinations were confirmed the thiol group of TSA. The gel like rheological properties with porcine mucous was confirmed by viscoelasticity properties and the mucoadhesion with the rabbit intestine was carried out after compression of 30 mg tablets of TSA. The content of thiol group was in the range of 320-730 µmoL/g of the polymer. The FTIR spectrum showed a characteristic peak of sulfhydryl group at 2557 cm-1 in TSA and the reduction of the charring point from 220 °C to 178 °C was confirmed the thiolation of TSA. A direct relationship of mucoadhesion and swelling was observed with the concentration of TGA and SA, respectively. The prepared microspheres were 2-7 µm in size, excellent rheological properties and non-fickian drug release behavior was observed.

Thiolated PVP-Amphotericin B Complexes: An Innovative Approach toward Highly Mucoadhesive Gels for Mucosal Leishmaniasis Treatment.

The aim of this study was to synthesize polymeric excipients that can form mucoadhesive hydrogels containing amphotericin B (AmB) for the treatment of mucosal leishmaniasis. 2-(2-Acryloylaminoethyldisulfanyl)-nicotinic acid (ACENA) was copolymerized with N-vinyl pyrrolidone to obtain thiolated polyvinylpyrrolidone (PVP) that was then complexed with AmB to improve its solubility. The resulting structure of thiolated PVP was evaluated by 1H nuclear magnetic resonance to confirm S-protected thiol groups, and the average molecular mass was determined by size exclusion chromatography. Moreover, variants of thiolated PVP-AmB were studied for the thiol content, amount of complexed AmB, cytotoxicity, mucoadhesive properties, and antileishmaniasis activity. The highest achieved degree of thiolation was 772 ± 24.64 µmol/g, and the amount of complexed AmB was 27.05 ± 0.31 µmol per g of polymer. Thiolated PVP and thiolated PVP-AmB variants (0.5% m/v) showed no cytotoxicity, whereas the equivalent concentration of free AmB reduced Caco-2 cell viability to 70% within 24 h. Thiol-functionalized PVP and PVP-AmB complexes displayed 7.66- and 7.20-fold higher adhesion to the mucosal surface in comparison to unmodified PVP and PVP-AmB, respectively. In addition, variants of thiolated PVP-AmB complexes displayed 100% antileishmaniasis activity in comparison to the 80% killing efficiency of Fungizone, which has been applied in the equivalent AmB concentration of 0.2 µg/mL. Thiol-functionalized PVP proved to be a promising novel excipient for the delivery of AmB providing enhanced solubility and improved mucoadhesive properties which are beneficial for the treatment of mucosal leishmaniasis.

Self-Emulsifying Drug Delivery Systems: Hydrophobic Drug Polymer Complexes Provide a Sustained Release in Vitro.

The aim of this study was to develop hydrophobic ionic drug polymer complexes in order to provide sustained drug release from self-emulsifying drug delivery systems (SEDDS). Captopril (CTL) was used as an anionic model drug to form ionic complexes with the cationic polymers Eudragit RS, RL, and E. Complexes of polymer to CTL charge ratio 1:1, 2:1, and 4:1 were incorporated in two SEDDS, namely FA which was 40% Kolliphor RH 40, 20% Kolliphor EL, and 40% castor oil and FB, which was 40% Kolliphor RH 40, 30% glycerol, 15% Kolliphor EL, and 15% castor oil. Blank and complex loaded SEDDS were characterized regarding their droplet size, polydispersity index (PDI), and zeta potential. Resazurin assay was performed on Caco-2 cells to evaluate the biocompatibility of SEDDS. Release of CTL from SEDDS was determined in release medium containing 0.2 mg/mL of 5,5'-dithiobis(2-nitrobenzoic acid) (DNTB) allowing quantification of free drug released into solution via a thiol/disulfide exchange reaction between CTL and DNTB forming a yellow dye. The droplet size of SEDDS FA and SEDDS FB were in the range of 100 ± 20 nm and 40 ± 10 nm, respectively, with a PDI < 0.5. The zeta potential of SEDDS FA and SEDDS FB increased after the incorporation of complexes. Cell viability remained above 80% after incubation with SEDDS FA and SEDDS FB in a concentration of 1% and 3% for 4 h. Without any polymer, CTL was entirely released from both SEDDS within seconds. In contrast, the higher the cationic lipophilic polymer to CTL ratio in SEDDS, the more sustained was the release of CTL. Among the polymers which were evaluated, Eudragit RL provided the most sustained release. SEDDS FA containing Eudragit RL and CTL in a ratio of 1:1 released 64.78 ± 8.28% of CTL, whereas SEDDS FB containing the same complex showed a release of 91.85 ± 1.17% within 1 h. Due to the formation of lipophilic ionic polymer complexes a sustained drug release from oily droplets formed by SEDDS can be achieved. Taking into account that drugs are otherwise instantly released from SEDDS, results of this study might open the door for numerous additional applications of SEDDS for which a sustained drug release is essential.

Thiolated chitosans: Are Cys-Cys ligands key to the next generation?

The potential of Cys-Cys ligands for the development of a novel type of S-protected thiomers was evaluated. S-protected thiomers chitosan-N-acetylcysteine-mercaptonicotinamide (CS-NAC-MNA) and chitosan-N-acetylcysteine-N-acetylcysteine (CS-NAC-NAC) were synthesized and characterized. Viscosity of polymers in presence of various concentrations of S-amino acids was monitored. Mucoadhesive properties were evaluated. FT-IR characterization confirmed the covalent attachment of NAC-MNA and NAC-NAC. Attached sulfhydryl groups were found in the range of 550 µmol/g. In the presence of amino acids bearing a free thiol group viscosity of both polymers increased. This increase in viscosity depended on the amount of added free thiols. Maximum force required to detach CS-NAC-MNA and CS-NAC-NAC from porcine intestinal mucosa was 1.4- and 2.7-fold higher than that required for chitosan, respectively. CS-NAC-MNA adhered up to 3 h, whereas CS-NAC-NAC adhered even for 8 h on this mucosa. Accordingly, the Cys-Cys substructure could be identified as highly potent ligand for the design of mucoadhesive polymers.

Lipophilic Arginine Esters: The Gateway to Preservatives without Side Effects.

This study hypothesized that long carbon chain cationic arginine (Arg) esters can be considered as toxicologically harmless preservatives. Arg-esters with C18 and C24 carbon chains, namely, arginine-oleate (Arg-OL) and arginine-decyltetradecanoate (Arg-DT), were synthesized. Structures were confirmed by FT-IR, 1H NMR, and mass spectroscopy. Both Arg-esters were tested regarding hydrophobicity in terms of log Poctanol/water, critical micelle concentration (CMC), biodegradability, cytotoxicity, hemolysis, and antimicrobial activity against Escherichiacoli (E. coli), Staphylococcusaureus (S. aureus), Bacillussubtilis (B. subtilis), and Enterococcusfaecalis (E. faecalis). Log Poctanol/water of arginine was raised from -1.9 to 0.3 and 0.6 due to the attachment of C18 and C24 carbon chains, respectively. The critical micelle concentration of Arg-OL and Arg-DT was 0.52 and 0.013 mM, respectively. Both Arg-esters were biodegradable by porcine pancreatic lipase. In comparison to the well-established antimicrobials, benzalkonium chloride (BAC) and cetrimide, Arg-esters showed significantly less cytotoxic and hemolytic activity. Both esters exhibited pronounced antimicrobial properties against Gram-positive and Gram-negative bacteria comparable to that of BAC and cetrimide. The minimum inhibitory concentration (MIC) of Arg-esters was <50 µg mL-1 against all tested microbes. Overall, results showed a high potential of Arg-esters with long carbon chains as toxicologically harmless novel preservatives.

S-protected thiolated hyaluronic acid: In-situ crosslinking hydrogels for 3D cell culture scaffold.

The purpose of this study was to synthesize S-protected thiolated hyaluronic acid (HA) and to evaluate its potential for 3D cell culture scaffold. S-protected thiolated HA was synthesized by the covalent attachment of N-acetyl-S-((3-((2,5-dioxopyrrolidin-1-yl)oxy)-3-oxopropyl)thio)cysteine hydrazide ligand to the HA. Hydrogels were characterized for texture, swelling behavior and rheological properties. Furthermore, the potential of S-protected thiolated HA hydrogels as a scaffold for tissue engineering was evaluated by cell proliferation studies with Caco-2 and NIH 3T3 cells. It showed enhanced cohesion upon addition of N-acetyl cysteine (NAC). Dynamic viscosity of S-protected thiolated HA hydrogel was increased up to 19.5-fold by addition of NAC and 10.1-fold after mixing with mucus. Furthermore, Caco-2 and NIH 3T3 cells encapsulated into hydrogels proliferated in-vitro. As this novel S-protected thiolated HA is stable towards oxidation and forms highly cohesive gels when getting into contact with endogenous thiols due to disulfide-crosslinking, it is a promising tool for 3D cell culture scaffold.

Per-6-Thiolated Cyclodextrins: A Novel Type of Permeation Enhancing Excipients for BCS Class IV Drugs.

The purpose of the study was to develop a per-6-thiolated α-cyclodextrin (α-CD) by substituting all primary hydroxyl groups of α-CD with thiol groups and to assess its solubility-improving and permeation-enhancing properties for a BCS Class IV drug in vitro as well as in vivo. The primary hydroxyl groups of α-CD were replaced by iodine, followed by substitution with -SH groups. The structure of per-6-thiolated α-CD was approved by FT-IR and 1H NMR spectroscopy. The per-6-thiolated was characterized for thiol content, -SH stability, cytotoxicity, and solubility-improving properties by using the model BCS Class IV drug furosemide (FUR). The mucoadhesive properties of the thiolated oligomer were investigated via viscoelastic measurements with porcine mucus, whereas permeation-enhancing features were evaluated on the Caco-2 cell monolayer and rat gut mucosa. Furthermore, oral bioavailability studies were performed in rats. The per-6-thiolated α-CD oligomer displayed 4244 ± 402 µmol/g thiol groups. These -SH groups were stable at pH ≤ 4, exhibiting a pKa value of 8.1, but subject to oxidation at higher pH. Per-6-thiolated α-CD was not cytotoxic to Caco-2 cells in 0.5% (m/v) concentration within 24 h. It improved the solubility of FUR in the same manner as unmodified α-CD. The addition of per-6-thiolated α-CD (0.5% m/v) increased the mucus viscosity up to 5.8-fold at 37 °C within 4 h. Because of the incorporation in per-6-thiolated α-CD, the apparent permeability coefficient (Papp) of FUR was 6.87-fold improved on the Caco-2 cell monolayer and 6.55-fold on the intestinal mucosa. Moreover, in vivo studies showed a 4.9-fold improved oral bioavailability of FUR due to the incorporation in per-6-thiolated α-CD. These results indicate that per-6-thiolated α-CD would be a promising auxiliary agent for the mucosal delivery of, in particular, BCS Class IV drugs.

Tetradeca-thiolated cyclodextrins: Highly mucoadhesive and in-situ gelling oligomers with prolonged mucosal adhesion.

The purpose of this study was to synthesize a highly mucoadhesive tetradeca-thiolated ß-cyclodextrin (ß-CD) by replacement of all primary OH groups at C-6 position and all secondary OH groups at C-2 position of ß-CD backbone viaSH groups and to evaluate its rheological and mucoadhesive properties in-vitro. Primary and secondary OH groups of ß-CD were substituted by SH groups using a microwave-assisted method. The structure of tetradeca-thiolated ß-CD was confirmed by FTIR and 1H NMR spectroscopy. The modified ß-CD was evaluated for SH content, thiol stability towards oxidation and cytotoxicity. Moreover, the viscoelastic behavior of the modified oligomer was investigated via rheological studies with porcine intestinal mucus and fibrous structural protein keratin, whereas mucoadhesive properties were evaluated using different porcine mucosae. Tetradeca-thiolated ß-CD oligomer displayed 8144 ± 317 µmol thiol groups per gram. These thiol groups displaying a pKa value of 8.2 were stable at pH 4 but prone to oxidation at higher pH values. The newly synthesized thiolated CD did not show any cytotoxicity to Caco-2 cells at a concentration of 0.5% (m/v) within 24 h. Due to the addition of 0.5 and 2% (m/v) tetradeca-thiolated ß-CD to mucus and keratin, the dynamic viscosity was increased up to 7.6- and 5.9- fold, respectively, within 4 h at 37 °C. Moreover, in-vitro mucoadhesion studies of tetradeca-thiolated CD showed 78.6-, 60.3-, 62.3- and 49.3- fold improved mucoadhesion on intestinal, buccal, bladder and vaginal mucosa as compared to unmodified ß-CD, respectively. According to these results, tetradeca-thiolated ß-CD might be a promising auxiliary agent to provide a prolonged residence time of drug delivery systems on different mucosal surfaces.

Hydrophobic H-bond pairing: A novel approach to improve membrane permeability.

The aim of the present study was to develop hydrophobic H-bond pairs (HHPs) of leuprolide (LEU) with non-ionic surfactants to improve its membrane permeability. LEU was lipidized via hydrophobic H-bond pairing (HHP) with the sucrose esters (SEs) sucrose laurate HLB 15 (SLA-15), sucrose palmitate HLB 16 (SPA-16), sucrose stearate HLB 11 (SST-11) and sucrose stearate HLB 15 (SST-15). HHPs were evaluated regarding precipitation efficiency in water, zeta potential, log Pn-octanol/water and dissociation behavior at various pH over time. Cytotoxic potential of HHPs of LEU with SST-11 was investigated on Caco-2 cells. Subsequently, ex vivo permeation studies were carried out across freshly excised Sprague-Dawley rat intestinal mucosa. At a molar ratio of LEU to SEs of 1:≥1 a precipitation efficiency of above 50% was achieved. Zeta potential of complexes was neither influenced by the type nor the amount of added surfactants. Log Pn-octanol/water of LEU was up to 250-fold increased due to HHP utilizing SST-11. Dissociation studies showed that HHPs of LEU with SST-11 dissociate up to 20% in gastrointestinal (GI) pH conditions within 4 h. Moreover, HHPs of LEU with SST-11 exhibited no cytotoxicity. Ex vivo permeation studies revealed 2-fold improved membrane permeation of HHPs of LEU with SST-11 compared to free LEU. Findings of this study show that HHP can be considered as a promising strategy to improve membrane permeation.

Mucoadhesive micro-composites: Chitosan coated halloysite nanotubes for sustained drug delivery.

It was aim of this study to synthesize micro-composites comprising halloysite nanotubes (HNTs) and the cationic polymer chitosan as mucoadhesive sustained release drug delivery system. Micro-composites were characterized for preparation yield, size, micromeritic properties and swelling behavior. Chemical composition of micro-composites was characterized by FTIR, XRD and TGA. Scanning electron microscopy (SEM) was used to study their surface morphology. Micro-composites were studied for adhesion on intestinal mucosa as well as for release behavior of metoclopramide hydrochloride used as model drug. Preparation yield was found to be in the range of 35.14 ± 1.5-53.97 ± 5.23%. Micro-composites exhibited a mean size range of 0.151 ± 0.49 µm. SEM showed a spherical shape with rough curved porous surface. Micro-composites exhibited excellent flowability and maximum swelling at acidic pH. XRD results showed crystalline nature of micro-composites. HNTs/micro-composites with highest concentration of chitosan displayed maximum adherence of 89 ± 1.79% on intestinal mucosa after 3 h. Drug release recorded was 66.8% at pH 1.2 and 46.7% at pH 5.5 within 25 h. Chitosan coated HNTs showed remarkable mucoadhesion and sustained release of metoclopramide proving their suitability as mucoadhesive drug delivery system.