Johannes Parmentier

Stability of liposomes containing bio-enhancers and tetraether lipids in simulated gastro-intestinal fluids.

The stability of egg phosphatidylcholine (EPC) and cholesterol (Chol) based liposomes and liposomes with the addition of the tetraether lipid glycerylcaldityl tetraether (GCTE) and the bio-enhancers cholylsarcosine, octadecanethiol and TPGS 1000 in Tris buffer pH 2, sodium taurocholate 10mM and pancreatin was compared. At pH 2 all formulations released nearly 100% of the small hydrophilic fluorescent marker carboxyfluorescein (CF) within the first 10min, whereas they were mostly stable in size as confirmed by dynamic light scattering (DLS) measurements. Also leakage of the macromolecule FITC-dextran 70kDa over 60min at pH 2 was at most 23.9%. After 20min in 10mM sodium taurocholate vesicles without GCTE showed a release of CF between 84.0% and 89.5%. In contrast, GCTE-stabilised formulations after 90min in sodium taurocholate exhibited a CF release between 36.6% and 69.0% depending on the addition of bio-enhancers. Pancreatin had a minor influence on liposome stability in all assays. It is possible to form EPC/Chol vesicles containing different types of bio-enhancers and to stabilise them with GCTE against bile salts. This type of liposomes could be a versatile tool for the oral delivery of drug substances with poor stability in the GI tract and low permeability.

Oral peptide delivery by tetraether lipid liposomes

The aim of this study is to improve of oral peptide delivery by a novel type of liposomes containing tetraether lipids (TELs) derived from archaea bacteria. Liposomes were used for the oral delivery of the somatostatin analogue octreotide. TELs were extracted from Sulfolobus acidocaldarius and subsequently purified to single compounds. Liposomes were prepared by the film method followed by extrusion. Vesicles in size between 130 and 207 nm were obtained as confirmed by photon correlation spectroscopy. The pharmacokinetics of radiolabeled TELs in liposomes was investigated after oral administration to rats. 1.6% of the applied radioactivity in fed and 1.5% in fasted rats was recovered in the blood and inner organs after 2h, while most of the radioactivity remained in the gastro-intestinal tract. After 24h the percentage of radioactivity in inner organs was reduced to 0.6% in fed rats, respectively 1.0% in fasted animals. Several liposomal formulations containing dipalmitoyl phosphatidylcholine (DPPC) and TELs in different ratios were loaded with octreotide and orally administered. Liposomes with 25% TEL could improve the oral bioavailability of octreotide 4.1-fold and one formulation with a cationic TEL derivative 4.6-fold. TEL-liposomes probably act by protecting the peptide in the gastro-intestinal tract.

Effect of type and ratio of solubilising polymer on characteristics of hot-melt extruded orodispersible films

In formulating an orodispersible film (ODF), it is important for polymer choice to strike a balance between mechanical properties and release rates. Studies have been done to study polymer combinations. However, there is a lack of a systematic study to determine key factors affecting these properties. We studied the effect of varying the ratios of a solubilising polymer (Kollidon(®) VA 64 or Soluplus(®)) to a film forming polymer, hydroxypropyl cellulose (HPC), on mechanical properties and release rates of hot-melt extruded ODFs using a 2(3) factorial design. The two drugs evaluated were chlorpheniramine and indomethacin. The main effects impacting mechanical properties were the drug and two-way interaction between drug and solubilising polymer. For dissolution, the main effects were the solubilising polymer; the drug; and the two-way interaction between solubilising polymer and ratio of solubilising to film forming polymer. Both drugs exhibited plasticising effects on the polymer matrix and had higher film ductility and lower film stiffness. Kollidon(®) VA 64-containing films performed better in terms of drug release whereas Soluplus(®)-containing films had better mechanical properties. The dissolution rate can be improved by decreasing film thickness. The findings of our study will be crucial to forming a robust ODF formulation.

A Brief Literature and Patent Review of Nanosuspensions to a Final Drug Product

Particle size reduction can be used for enhancing the dissolution of poorly water-soluble drugs in order to enhance bioavailability. In nanosuspensions, the particle size of the drug is reduced to nanometer size. Nanosuspensions after downstream processing into drug products have successfully shown its impact on formulation design, the augmentation of product life cycle, patent life, and therapeutic efficacy. Formulation considerations for the nanosuspension formulation, its processing into a solid form, and aspects of material characterization are discussed. Technology assessments and feasibility of upstream processes for nanoparticle creation, and subsequently transformation into a drug product via the downstream processes have been reviewed. This paper aims to bridge formulation and process considerations along with patent reviews and may provide further insight into understanding the science and the white space. An analysis of current patent outlook and future trends is described to fully understand the limitations and opportunities in intellectual property generation.

In vitro evaluation of liposomes containing bio-enhancers for the oral delivery of macromolecules

The aim of this work was to develop a new type of liposomes containing bio-enhancers for oral delivery of hydrophilic macromolecules. The study focused on EPC/cholesterol-based formulations combined with TPGS 1000 and 400, cholylsarcosine (CS), cetylpyridinium chloride (CpCl) and stearylamine (SA) covering a broad range of different types of enhancers. Most of the tested liposomal formulations and enhancers showed neither influence on cell viability in the Alamar Blue® assay nor an increase in lactate dehydrogenase LDH release. But, at a concentration of 1 mM, CpCl exhibited a strong toxicity after 2 h, TPGS 1000 reduced the cell viability at the same concentration after 8h significantly. Only one liposomal formulation with 25% CpCl led to a decrease in viability to 60.0% after 8h at a total lipid concentration of 5 mM. In the Caco-2 Transwell® model, one formulation with 5% TPGS 400 improved the permeation of FITC-dextran 70 kDa 3.34 ± 0.62-fold, one with 10% CpCl 3.69 ± 0.67 and one with 10% CS and 2.5% SA 3.41 ± 0.51-fold without influencing the TER. Liposomes with 10% SA or 25% CpCl increased the permeation of FITC-dextran 29.02 ± 5.84, respectively 39.28 ± 2.10-fold, but led also to a strong reduction in the TER. Especially, the three formulations which enhanced the permeation of FITC-dextran around 3.5-fold without showing any cell toxicity or decrease in TER should be safe and effective candidates for the development of an oral delivery system for hydrophilic macromolecules.

Improved oral bioavailability of human growth hormone by a combination of liposomes containing bio-enhancers and tetraether lipids and omeprazole.

Liposomes for the oral delivery of human growth hormone (hGH) containing bio-enhancers and tetraether lipids were prepared by dual asymmetric centrifugation. Cetylpyridinium chloride (CpCl), d-α-tocopheryl polyethylene glycol 400 succinate, phenylpiperazine, sodium caprate or octadecanethiol were used as permeation enhancers. In vitro data showed that oligolamellar vesicles with average size in the range of 200-250 nm were formed. Performance of the formulations was investigated both ex vivo by confocal microscopy scans of sections of rat small intestine and in vivo by comparing the area under the plasma curve of hGH after oral or subcutaneous (s.c.) application. The microscopic data reveal an interaction between the liposomal formulation and the intestinal mucus layer. Particularly one formulation, which was designed to be mucus penetrative by addition of a high quantity of TPGS 400 and a ζ-potential close to 0 mV, showed a very strong mucus association in the duodenum and jejunum. Vesicles with CpCl 33% (mol/mol) led to a relative hGH bioavailability of 3.4% compared with s.c. control, whereas free hGH administered orally showed a bioavailability of only 0.01%.

Exploring the fate of liposomes in the intestine by dynamic in vitro lipolysis

Liposomes are generally well tolerated drug delivery systems with a potential use for the oral route. However, little is known about the fate of liposomes during exposure to the conditions in the gastro-intestinal tract (GIT). To gain a better understanding of liposome stability in the intestine, a dynamic in vitro lipolysis model, which so far has only been used for the in vitro characterisation of other lipid-based drug delivery systems, was applied to different liposomal formulations. Liposome size and phospholipid (PL) digestion were determined as two markers for liposome stability. In addition, the effect of PL degradation on the ability to maintain liposomally incorporated danazol in solution during lipolysis was evaluated in order to address the feasibility of liposomes designed for oral administration. Rate and extend of hydrolysis of PLs mediated by pancreatic enzymes was determined by titration and HPLC. Size of liposomes was determined by dynamic light scattering during incubation in lipolysis medium (LM) and during lipolysis. SPC-based (soy phosphatidylcholine) liposomes were stable in LM, whereas for EPC-3-based (hydrated egg phosphatidylcholine) formulations the formation of aggregates of around 1 μm in diameter was observed over time. After 60 min lipolysis more than 80% of PLs of the SPC-liposomes were digested, but dependent on the liposome concentration only a slight change in size and size distribution could be observed. Although EPC-3 formulations did form aggregates during lipolysis, the lipids exhibited a higher stability compared to SPC and only 30% of the PLs were digested. No direct correlation between liposome integrity assessed by vesicle size and PL digestion was observed. Danazol content in the liposomes was around 5% (mol/mol danazol/total lipid) and hardly any precipitation was detected during the lipolysis assay, despite pronounced lipolytic degradation and change in vesicle size. In conclusion, the tested dynamic in vitro lipolysis model is suitable for the assessment of liposome stability in the intestine. Furthermore, liposomes might be a useful alternative to other lipid based delivery systems for the oral delivery of poorly soluble drugs.

Downstream drug product processing of itraconazole nanosuspension: Factors influencing drug particle size and dissolution from nanosuspension-layered beads

There is more research required to broaden the knowledge on the downstream processing of nanosuspensions into solid oral dosage forms, especially for coated nanosuspensions onto beads as carriers. This study focuses on bead layering as one approach to solidify nanosuspensions. The aim was to systematically investigate the influence of type of coating polymer (HPMC VLV vs. copovidone), bead material and bead size (sugar vs. MCC, and small vs. large) and coating thickness (50%-150% layering level) on the properties of a dried itraconazole nanosuspension. A stable itraconazole nanosuspension with a mean particle size below 200nm was prepared and a ratio of itraconazole and coating polymer of around 1:1 was identified. XRD and DSC scans revealed that itraconazole remained mostly crystalline after the bead layering process. The fastest dissolution rate was achieved using the small bead size, sugar beads, HPMC VLV as film-forming polymer and lowest layering level, with the best formulation releasing 94.1% (±3.45% SD) within the first 5min. A deterioration of the release profile with increasing layering level was only observed for MCC beads and was more pronounced when copovidone was used as a coating polymer. It was observed that bead layering is a suitable method to process an itraconazole nanosuspension into a solid form without compromising release.

Oral bioavailability of ketoprofen in suspension and solution formulations in rats: the influence of poloxamer 188.

Objectives  The aim of the current study was to investigate the effect of poloxamer 188 (P‐188) on the bioavailability of the BCS class 2 drug ketoprofen in vivo.

Oral delivery of vancomycin by tetraether lipid liposomes

&NA; Despite the outstanding progress in modern medicine, the oral delivery of peptide drugs is limited until today due to their instability in the gastrointestinal tract and low mucosa penetration. To overcome these hurdles, liposomes containing the specific tetraether lipid GCTE (glycerylcaldityltetraether lipid) were examined. For this purpose, the glycopeptide antibiotic vancomycin was used as model substance and liposomes were prepared by DAC (dual assymetric centrifugation). These liposomes showed a size and polydispersity index comparable to standard liposomes. A high encapsulation efficiency of 58.53 ± 1.76% of the peptide drug vancomycin could be obtained as detected by HPLC. FCS analysis showed that in average each liposome contains 30 molecules of vancomycin. TEM and Cryo‐EM micrographs verified the size and lamellarity of the liposomal formulations. Cytotoxicity tests in Caco‐2 cells showed no significant cytotoxicity for all liposomal concentrations tested, indicating the good tolerability of these formulations. Furthermore, the use of sucrose as lyoprotector enabled the long term storage of the liposomal formulation for at least three months. The potency of this drug delivery system could be proven in an animal model using Wistar rats. One hour after oral application, 4.82 ± 0.56% of the administered dose of vancomycin could be found in the blood as detected by immunoassay measurements. This transport did also not affect the integrity of the peptide as verified by immunoassay measurements. In combination with long term storage stability, this formulation appears to be a promising delivery system for oral application of peptide drugs. Graphical abstract Figure. No caption available.