Evaluation of different polyhydroxy surfaces in SEDDS to overcome the limitations associated with conventional polyethylene glycol (PEG)-based SEDDS surfaces for intracellular drug delivery.

This study aimed to develop phosphatase-responsive ζ potential converting nanocarriers utilizing polyphosphate-coated cell-penetrating peptide (CPP)-decorated nanoemulsions (NEs) as a novel gene delivery system to retinal cells.

As less reactive s-protected thiomers can likely interpenetrate the mucus gel layer to a higher extent before getting immobilized via disulfide bond formation with mucins, it was the aim of this study to develop a novel type of s-protected thiomer based on the less reactive substructure cysteine-N-acetyl cysteine (Cys-NAC) in order to obtain improved mucoadhesive properties. For this purpose, two types of s-protected thiomers, polyacrylic acid-cysteine-mercaptonicotinic acid (PAA-Cys-MNA) and polyacrylic acid-cysteine-N-acetyl cysteine (PAA-Cys-NAC), were synthesized and characterized by Fourier-transform infrared spectroscopy (FT-IR) and the quantification of attached disulfide ligands. The viscosity of both products was measured in the presence of NAC and mucus. Both thiomers were also evaluated regarding swelling behavior, tensile studies and retention time on the porcine intestinal mucosa. The FT-IR spectra confirmed the successful attachment of Cys-MNA and Cys-NAC ligands to PAA. The number of attached sulfhydryl groups was in the range of 660-683 µmol/g. The viscosity of both s-protected thiomers increased due to the addition of increasing amounts of NAC. The viscosity of the mucus increased in the presence of 1% PAA-Cys-MNA and PAA-Cys-NAC 5.6- and 10.9-fold, respectively, in comparison to only 1% PAA. Both s-protected thiomers showed higher water uptake than unmodified PAA. The maximum detachment force (MDF) and the total work of adhesion (TWA) increased in the case of PAA-Cys-MNA up to 1.4- and 1.6-fold and up to 2.4- and 2.8-fold in the case of PAA-Cys-NAC. The retention of PAA, PAA-Cys-MNA, and PAA-Cys-NAC on porcine intestinal mucosa was 25%, 49%, and 76% within 3 h, respectively. The results of this study provide evidence that less reactive s-protected thiomers exhibit higher mucoadhesive properties than highly reactive s-protected thiomers.

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.

The use of chemotherapeutic agents such as docetaxel (DTX) in anticancer therapy is often correlated to side effects and the occurrence of drug resistance, which substantially impair the efficacy of the drug. Here, we demonstrate that self-emulsifying drug delivery systems (SEDDS) coated with enoxaparin (Enox) are a promising strategy to deliver DTX in resistant tumors. DTX partition studies between the SEDDS pre-concentrate and the release medium (water) suggest that the drug is well retained within the SEDDS upon dilution in the release medium. All SEDDS formulations show droplets with a mean diameter between 110 and 145 nm following dilution in saline and negligible hemolytic activity; the droplet size remains unchanged upon sterilization. Enox-coated SEDDS containing DTX exhibit an enhanced inhibition of cell growth compared to the control on cells of different solid tumors characterized by high levels of FGFR, which is due to an increased DTX internalization mediated by Enox. Moreover, only Enox-coated SEDDS are able to restore the sensitivity to DTX in resistant cells expressing MRP1 and BCRP by inhibiting the activity of these two main efflux transporters for DTX. The efficacy and safety of these formulations is also confirmed in vivo in resistant non-small cell lung cancer xenografts.

Development of zeta potential changing SEDDS containing newly synthesized derivative stearic acid phosphotyrosine amide.

This study was aimed to synthesize polymeric excipients with improved mucoadhesive, cohesive and in situ-gelling properties to assure a prolonged retention time of dosage forms at a given target site, thereby achieving an increased uptake and improved oral bioavailability of certain challenging therapeutic agents such as peptides and proteins. Accordingly, poly(acrylic acid)-cysteine-2-mercaptonicotinic acid (PAA-cys-2MNA) conjugates were synthesized by the oxidative S-S coupling of PAA-cys (100-, 250- and 450 kDa) with 2-mercaptonicotinic acid (2MNA). Unmodified PAAs, PAAs-cys (thiomers) and PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates were compressed into tablets to perform disintegration tests, mucoadhesion studies and rheological measurements. Moreover, cytotoxicty of the polymers was determined using Caco-2 cells. The resulting PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates displayed 113.5 ± 12.7, 122.7 ± 12.2 and 117.3 ± 4.6 μmol/g of 2-mercaptonicotinic acid, respectively. Due to the immobilization of 2MNA, the PAA-cys-2MNA (pre-activated thiomers) conjugates exhibit comparatively higher swelling properties and disintegration time to the corresponding unmodified and thiolated polymers. On the rotating cylinder, tablets based on PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates displayed 5.0-, 5.4- and 960-fold improved mucoadhesion time in comparison to the corresponding unmodified PAAs. Results achieved from tensile studies were found in good agreement with the results obtained by rotating cylinder method. The apparent viscosity of PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates was improved 1.6-, 2.5- and 206.2-fold, respectively, in comparison to the corresponding unmodified PAAs. Moreover, pre-activated thiomers/mucin mixtures showed a time dependent increase in viscosity up to 24 h, leading to 7.0-, 18.9- and 2678-fold increased viscosity in comparison to unmodified PAAs (100-, 250- and 450 kDa), respectively. All polymers were found non-toxic over Caco-2 cells. Thus, on the basis of achieved results the pre-activated thiomers seem to represent a promising generation of mucoadhesive polymers which are safe to use for prolonged residence time of drug delivery systems to target various mucosa.

This study aims to design a novel thiolated κ-carrageenan (κ-CA-SH) and evaluate its potential as an excipient for the design of mucoadhesive drug delivery systems.

To date, buccal administration of lipophilic drugs is still a major challenge due to their poor solubility in saliva and limited penetration into mucosal tissues. To overcome these limitations, we developed electrospun patches combining the benefits of mucoadhesive fibers and self-emulsifying drug delivery systems (SEDDS). The fiber system comprises a combination of mucoadhesive thiolated polyacrylic acid fibers and SEDDS-loaded fibers fabricated by parallel electrospinning. The resulting mucoadhesive electrospun SEDDS patches were systemically investigated for fiber characteristics, self-emulsification, mucoadhesion, drug penetration into porcine buccal tissue and biocompatibility. The patches showed high encapsulation efficiency for SEDDS without causing fiber defects or leakage. SEDDS incorporation enhanced the spinning process and reduced the fiber diameter and fiber size distribution. Hydration-dependent self-emulsification provided a controlled release of curcumin being encapsulated in nano-scaled o/w emulsion for over 3 h. Due to the thiolated polyacrylic acid fibers, the buccal residence time of patches was 200-fold prolonged. Further, they promoted a significantly increased drug penetration into buccal tissue compared to fiber patches without SEDDS. Finally, biocompatibility and improved therapeutic effects of curcumin-loaded patches on human keratinocytes and fibroblasts were confirmed. Mucoadhesive electrospun SEDDS patches represent a promising approach to overcome current challenges in the oromucosal delivery of lipophilic drugs to unlock their full therapeutic potential.

The aim of this study was to develop nanoparticles (NPs) providing a targeted drug release directly on the epithelium of the intestinal mucosa. NPs were prepared via ionic gelation between cationic chitosan (Cs) and anionic polyphosphate (PP). The resulting NPs were characterized by their size, polydispersity index (PDI) and zeta potential. Isolated and cell-associated intestinal alkaline phosphatase (IAP) was employed to trigger polyphosphate cleavage in Cs-PP NPs which was quantified via malachite green assay. In parallel, the shift in zeta potential was determined. In-vitro drug release studies were performed in Franz diffusion cells with Cs-PP NPs containing rhodamine 123 as model active ingredient. Furthermore, cytotoxicity of Cs-PP NPs was assessed via resazurin assay on Caco-2 cells as well as via hemolysis assay on red blood cells. Cs-PP NPs exhibited an average size of 144.17 ± 10.95 nm and zeta potential of -12.6 ± 0.50 mV. The encapsulation efficiency of rhodamine 123 by Cs-PP NPs was 86.8%. After incubation with isolated IAP for 3 h the polyphosphate of Cs-PP NPs was cleaved to monophosphate and zeta potential raised up to -2.3 ± 0.30 mV. Cs-PP NPs showed a non-toxic profile. Within 3 h, 62.0 ± 10.8% and 14.1 ± 2.2% of total rhodamine 123 was released from Cs-PP NPs upon incubation with isolated as well as porcine intestine derived intestinal alkaline phosphatase (IAP), respectively. According to these results, Cs-PP NPs are promising drug delivery systems to enable a drug targeted release at the absorption membrane.

Purpose of the present study was the generation and evaluation of novel thiolated chitosans, so-named S-protected thiolated chitosans as mucosal drug delivery systems. Stability of all conjugates concerning swelling and disintegration behavior as well as drug release was examined. Mucoadhesive properties were evaluated in vitro on intestinal mucosa. Different thiolated chitosans were generated displaying increasing amounts of attached free thiol groups on the polymer, whereby more than 50% of these thiol groups were linked with 6-mercaptonicotinamide. Based on the implementation of this hydrophobic residue, the swelling behavior was 2-fold decreased, whereas stability was essentially improved. Their mucoadhesive properties were 2- and 14-fold increased compared to corresponding thiolated and unmodified chitosans, respectively. Release studies out of matrix tablets comprising the novel conjugates revealed a controlled release of a model peptide. Accordingly, S-protected thiomers represent a promising type of mucoadhesive polymers for the development of various mucosal drug delivery systems.

The aim of this study was to develop peptide antibiotic-polyphosphate nanoparticles that are able to overcome the enzymatic and mucus barriers providing a targeted drug release directly on the intestinal epithelium. Polymyxin B-polyphosphate nanoparticles (PMB-PP NPs) were formed via ionic gelation between the cationic peptide and the anionic polyphosphate (PP). The resulting NPs were characterized by particle size, polydispersity index (PDI), zeta potential, and cytotoxicity on Caco-2 cells. The protective effect of these NPs for incorporated PMB was evaluated via enzymatic degradation studies with lipase. Moreover, mucus diffusion of NPs was investigated with porcine intestinal mucus. Isolated intestinal alkaline phosphatase (IAP) was employed to trigger the degradation of NPs and consequent drug release. PMB-PP NPs exhibited an average size of 197.13 ± 14.13 nm, a PDI of 0.36, a zeta potential of -11.1 ± 3.4 mV and a concentration and time-dependent toxicity. They provided entire protection toward enzymatic degradation and exhibited significantly (p < 0.05) higher mucus permeating properties than PMB. When incubated with isolated IAP for 4 h, monophosphate and PMB were constantly released from PMB-PP NPs and zeta potential raised up to -1.9 ± 0.61 mV. According to these findings, PMB-PP NPs are promising delivery systems to protect cationic peptide antibiotics against enzymatic degradation, to overcome the mucus barrier and to provide drug release directly at the epithelium.

The purpose of this study was to synthesize a highly mucoadhesive tetradeca-thiolated β-cyclodextrin (β-CD) by replacement of all primary OH groups at C-6 position and all secondary OH groups at C-2 position of β-CD backbone viaSH groups and to evaluate its rheological and mucoadhesive properties in-vitro. Primary and secondary OH groups of β-CD were substituted by SH groups using a microwave-assisted method. The structure of tetradeca-thiolated β-CD was confirmed by FTIR and 1H NMR spectroscopy. The modified β-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 β-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 β-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 β-CD, respectively. According to these results, tetradeca-thiolated β-CD might be a promising auxiliary agent to provide a prolonged residence time of drug delivery systems on different mucosal surfaces.