Charge reversal self-emulsifying drug delivery systems: A comparative study among various phosphorylated surfactants.

HYPOTHESIS: Phosphorylated surfactants having ethoxylate spacer arms are promising excipients for charge reversal self-emulsifying drug delivery systems (SEDDS). EXPERIMENTS: 1,2-Dipalmitoyl-sn-glycero-3-phosphatidic acid disodium salt (PA), 2-((2,3-bis(oleoyloxy)propyl)dimethylammonio)ethyl hydrogen phosphate (DOCP), nonylphenol monophosphate ester (PNPP), C12-15 alcohol 3 ethoxylate phosphate ester (PME) and polyoxyethylene (9) dioctanoyl glycerol pyrophosphate (DGPP) loaded SEDDS were developed and characterized. Zeta potential of SEDDS was measured before and after incubation with intestinal alkaline phosphatase (IAP). Phosphate release was monitored by incubation of SEDDS with isolated as well as cell-associated IAP. Primary amine content on the surface of SEDDS was determined in parallel. Cytotoxicity was evaluated on Caco-2 cells and in vitro hemolysis test was performed. Cellular uptake studies were performed by confocal scanning microscopy. FINDINGS: SEDDS formulations exhibited a size in the range of 17 and 193 nm and a polydispersity index (PDI) ≤ 0.5. Charge reversal from negative to positive values could be achieved in case of PNPP and PME loaded SEDDS with a zeta potential changing from -13 mV to +9 mV and from -7 to +2 mV, respectively, within 6 h. Significant amounts of phosphate were released from PNPP and PME loaded SEDDS incubated with isolated IAP and from all formulations incubated with cell-associated IAP in accordance with an increase in primary amines on the surface of oily droplets. SEDDS exhibited a concentration and time-dependent cytotoxicity. PNPP and PME SEDDS displayed an increased cellular uptake.

Lysine-Based Biodegradable Surfactants: Increasing the Lipophilicity of Insulin by Hydrophobic Ion Paring.

AIM: The aim of this study was to evaluate biodegradable cationic surfactants based on lysine. METHODS: Lysine was esterified with cholesterol, oleyl alcohol and 1-decanol resulting in cholesteryl lysinate (CL), oleyl lysinate (OL) and decyl lysinate (DL). Esters were investigated regarding their log Dn-octanol/water, critical micelle concentration (CMC) and biodegradability. Hemolytic potential of CL, OL, DL and the already established hexadecyl lysinate (HL) was determined and complexes with insulin (INS) were formed by hydrophobic ion pairing (HIP). Lipophilic characteristics of ion-pairs were examined by analyzing their log Pn-butanol/water. RESULTS: Successful synthesis of CL, OL and DL was confirmed by IR, NMR and MS. Log D analysis revealed amphiphilic properties for the esters and a CMC of 0.01 mM, 2.0 mM and 6.0 mM was found for CL, OL and DL, respectively. Biodegradability was proven, as over 99% of OL and DL were degraded by isolated enzymes within 30 min and after 3 h 97% of CL was cleaved by membrane bound enzymes. OL as well as DL displayed no hemolytic effect and for CL cytotoxicity was significantly reduced in comparison to HL. INS/CL complex exhibited highest lipophilicity. CONCLUSION: Cholesterol-amino acid based surfactants seem to be promising agents for HIP.

Phosphorylated PEG-emulsifier: Powerful tool for development of zeta potential changing self-emulsifying drug delivery systems (SEDDS).

AIM: It was the aim of this study to synthesize a phosphorylated emulsifier possessing a PEG-linker for establishment of a potent zeta potential changing system in self-emulsifying drug delivery systems (SEDDS). METHODS: N,N'-Bis(polyoxyethylene)oleylamine (POA) was phosphorylated utilizing pyrophosphoric acid. Successful synthesis of POA bisphosphate (POAP) was confirmed by NMR and HR CS MAS. After incorporation of 1% POAP into SEDDS (Kolliphor RH 40, Capmul PG-8, Labrafac Lipophile WL 1349, Labrafac PG; 30/20/20/30, v/v), according emulsions were incubated with intestinal alkaline phosphatase (IAP) and the zeta potential was measured. Additionally, the amount of released phosphate upon incubation with IAP or on Caco-2 cells was quantified by malachite green assay. Finally, cell viability studies on Caco-2 cells were performed and mucus permeation properties with and without IAP preincubation were assessed. RESULTS: POAP was synthesized as brown viscous liquid with a yield of 36% and could be incorporated into SEDDS. By incubation with IAP a zeta potential shift from -15.1 to 6.5 mV was observed. A corresponding phosphate release in presence of isolated IAP as well as on Caco-2 cells was found. Assessment of the cytotoxic potential revealed no significant alteration in the safety profile of SEDDS by incorporation of POAP. Mucus permeation studies exposed a 2-fold higher permeation of fluorescein diacetate (FDA) having been embedded in SEDDS loaded with POAP in comparison to blank formulation and 3-fold higher permeability than for emulsions having been preincubated with phosphatase. CONCLUSION: The novel phosphorylated surfactant exhibiting a PEG-linker facilitated a potent zeta potential change of SEDDS.

Characterization of an amino acid based biodegradable surfactant facilitating the incorporation of DNA into lipophilic delivery systems.

HYPOTHESIS: Lysine based cationic surfactants are well-tolerated tools for hydrophobic ion pairing (HIP) with DNA and its incorporation into lipophilic delivery systems. EXPERIMENTS: Di-Boc-lysine was esterified with 1-hexadecanol and the Boc-residues were cleaved off resulting in hexadecyl lysinate (HL). Subsequently, its Log POctanol/water and the critical micelle concentration (CMC) were determined. Degradability was evaluated utilizing trypsin and pancreas lipase as well as Caco-2 cells. Afterwards, the viability of Caco-2 cells upon incubation with HL was investigated. Finally, HL was ion-paired with plasmid DNA (pDNA, 6159 bp) and the obtained complex was incorporated into self-emulsifying drug delivery systems (SEDDS) for transfection studies on HEK-293 cells. FINDINGS: HL was synthesized with a yield of 53% and subsequent characterization revealed a Log PWater/Octanol of 0.05 and a CMC of 2.7 mM. Enzymatic degradation studies showed rapid degradation of HL by isolated enzymes and Caco-2 cells and cell viability experiments revealed no toxic effect of HL even in a concentration of 250 µg·ml-1 within 24 h. HIP with pDNA was the most efficient in a molar ratio of 6159:1 (HL:pDNA) equalling a charge ratio of 1:1. Formed complexes could be incorporated into SEDDS facilitating successful transfection of HEK-293 cells.

Arginine-based cationic surfactants: Biodegradable auxiliary agents for the formation of hydrophobic ion pairs with hydrophilic macromolecular drugs.

WORKING HYPOTHESIS: It was the hypothesis of this study that esters of arginine (Arg) with medium and long chain aliphatic alcohols are biodegradable and less cytotoxic than well-established cationic surfactants being used for hydrophobic ion pairing (HIP) with hydrophilic macromolecular drugs. EXPERIMENTS: Arg was linked to nonan-1-ol and hexadecan-1-ol (C9 and C16) via an ester linkage. The newly formed Arg-nonyl ester (ANE) and Arg-hexadecanoyl ester (AHE) surfactants were evaluated regarding critical micelle concentration (CMC) using pyrene fluorescent method, cytotoxicity on human colorectal adenocarcinoma-derived cells (Caco-2) and biodegradability at the concentrations of 2.5 and 5 mg/mL using 2500 Nα-benzoyl-l-arginine ethyl ester hydrochloride (BAEE) units/mL of trypsin. Furthermore, in order to evaluate their potential for HIP, heparin and daptomycin were used as model polysaccharide and peptide drugs, respectively. FINDINGS: Chemical structures of ANE and AHE surfactants were confirmed by FTIR, 1H NMR, and LC-MS. CMC of ANE was 7.5 mM and CMC of AHE was 2 mM. Arg-surfactants were not cytotoxic below their CMC. At CMC and above CMC, ANE was significantly (P < 0.05) more cytotoxic than AHE. ANE in both concentrations was degraded ˃98% within 48 h. The degradation of AHE at lower concentration was ˃97% and about 50% at higher concentration. Arg-surfactants were able to efficiently precipitate heparin and daptomycin from corresponding aqueous solutions. CONCLUSION: Arg-surfactants being biodegradable and less toxic seems to be a promising alternative to well-established cationic surfactants for the formation of hydrophobic ion pairs (HIPs) with hydrophilic macromolecular drugs.

In situ gelling and mucoadhesive polymers: why do they need each other?

INTRODUCTION: Mucosal drug delivery is an attractive route of administration, particularly in overcoming deficits of conventional dosage forms including high first-pass metabolism and poor bioavailability. Fast drainage from the target mucosa, however, represents a major limitation as it prevents sufficient drug absorption. In order to address these problems, mucoadhesive in situ gelling drug delivery systems have been investigated as they facilitate easy application in combination with a longer residence time at the administration site resulting in more desirable therapeutic effects. AREAS COVERED: The present review evaluates the importance of the combination of mucoadhesive and in situ gelling polymers along with mechanisms of in situ gelation and mucoadhesion. In addition, an overview about recent applications in mucosal drug delivery is provided. EXPERT OPINION: In situ gelling and mucoadhesive polymers proved to be essential excipients in order to prolong the mucosal residence time of drug delivery systems. Due to this prolonged residence time both local and systemic therapeutic efficacy of numerous drugs can be substantially improved. Depending on the site of administration and the incorporated drug, combinations of different polymers with in situ gelling and mucoadhesive properties are needed to keep the delivery system as long as feasible at the target site.