X-ray microfocus computed tomography: a powerful tool for structural and functional characterisation of 3D printed dosage forms.

One of the most promising advances in modern pharmaceutical technology is the introduction of three-dimensional (3D) printing technology for the fabrication of drug products. 3D printed dosage forms have the potential to revolutionise pharmacotherapy as streamlined production of structurally complex formulations with optimal drug releasing properties is now made possible. 3D printed formulations are derived as part of a process where a 'print-head' deposits, or sinters material under computer control to produce a drug carrier. However, this manufacturing route inherently generates objects that deviate from the ideal designed template for reasons specific to the 3D printing method used. This short opinion article discusses the potential of high-resolution nondestructive 3D (volume) imaging by means of X-ray microfocus Computed Tomography (µCT) as a Process Analytical Technology for the structural and functional characterisation of 3D printed dosage forms.

Stability and physicochemical characterization of novel milk-based oral formulations.

PURPOSE: The purpose of this work was to assess the colloidal stability of novel milk-based formulations. METHODS: Milk-based formulations were prepared in situ by adding into milk alkaline- or ethanolic-drug solutions containing an array of drugs namely; ketoprofen, tolfenamic acid, meloxicam, tenoxicam and nimesulide, mefenamic acid, cyclosporine A, danazol and clopidogrel besylate. The produced formulations were characterized by means of dynamic lightscattering, ζ-potential studies, atomic force microscopy, fluorescence spectroscopy, Raman spectroscopy complemented with ab initio calculations and stability studies. RESULTS: The presence of the drugs did not induce significant changes in most cases to the particle size and ζ-potential values of the emulsions pointing to the colloidal stability of these formulations. Raman spectroscopy studies revealed interactions of the drugs and the milk at the intermolecular level. Complementary analysis with ab initio calculations confirmed the experimental observations obtained by Raman spectroscopy. Finally the produced drug containing alkaline/ethanolic solutions exhibited stability over a period of up to 12 months. CONCLUSIONS: The current data demonstrate that milk is a promising drug carrier.

A once-a-day dosage form for the delivery of insulin through the nasal route: in vitro assessment and in vivo evaluation.

An in situ thermogelling, mucoadhesive formulation based on N-trimethyl chitosan chloride has been evaluated for its potential to affect the transmucosal delivery of insulin via the nasal route. In vitro studies at a physiologically relevant temperature (ca. 35 °C) have shown that the formulation releases most of its insulin load (ca. 70%) in a non-Fickian manner during the timescale over which the sol-to-gel transition (ca. 8 min) takes place, and also that, once gelation is complete, the release of the remainder of the therapeutic content follows first order kinetics over at least sixty minutes. Investigations on the effects of the application of the same formulation to a modelled nasal mucosa (Calu-3 cell monolayer) have indicated the capability of the formulation to induce the transient opening of tight junctions. Cytotoxic investigations have shown that the formulation exhibits negligible detrimental effects to the integrity of these monolayers. The in vivo potential of the nasal formulation to act as a once-a-day dosage form for the intranasal delivery of insulin has been demonstrated in a diabetic-rat model.

Thermosensitive hydrogels for nasal drug delivery: the formulation and characterisation of systems based on N-trimethyl chitosan chloride.

Towards the development of a thermosensitive drug-delivery vehicle for nasal delivery, a systematic series of N-trimethyl chitosan chloride polymers, synthesised from chitosans of three different average molecular weights, have been co-formulated into a hydrogel with poly(ethylene glycol) and glycerophosphate. Rheological evaluations have shown that hydrogels derived from N-trimethyl chitosan with a low degree of quaternisation and high or medium average molecular weight exhibit relatively short sol-gel transition times at physiologically relevant temperatures. Also, the same hydrogels display good water-holding capacity and strong mucoadhesive potential, and their mixtures with mucus exhibit rheological synergy. An aqueous hydrogel formulation, derived from N-trimethyl chitosan of medium average molecular weight and low degree of quaternisation, appears particularly promising in that it exhibits most favourable rheological and mucoadhesive behaviour and a sol-gel transition that occurs at 32.5°C within 7 min.

Physisorbed o-carborane onto lyso-phosphatidylcholine-functionalized, single-walled carbon nanotubes: a potential carrier system for the therapeutic delivery of boron.

A combination of data from ICP-MS, Raman spectroscopy, UV-vis spectrometry, atomic force microscopy, zeta-potential measurements and gel electorphoresis studies has shown that o-carborane may be immobilized on stable aqueous dispersions of lyso-phosphatidylcholine-functionalized single-walled carbon nanotubes, which in turn indicates the potential of such structures for deployment as carrier vehicles in boron neutron capture therapy.

Chitosan derivatives alter release profiles of model compounds from calcium phosphate implants.

The aim of the current study was to evaluate the impact of chitosan derivatives, namely N-octyl-chitosan and N-octyl-O-sulfate chitosan, incorporated in calcium phosphate implants to the release profiles of model drugs. The rate and extent of calcein (on M.W. 650 Da) ED, and FITC-dextran (M.W. 40 kDa) on in vitro release were monitored by fluorescence spectroscopy. Results show that calcein release is affected by the type of chitosan derivative used. A higher percentage of model drug was released when the hydrophilic polymer N-octyl-sulfated chitosan was present in the tablets compared with the tablets containing the hydrophobic polymer N-octyl-chitosan. The release profiles of calcein or FD from tablets containing N-octyl-O-sulfate revealed a complete release for FD after 120 h compared with calcein where 20% of the drug was released over the same time period. These results suggest that the difference in the release profiles observed from the implants is dependent on the molecular weight of the model drugs. These data indicate the potential of chitosan derivatives in controlling the release profile of active compounds from calcium phosphate implants.

Visualization studies of human skin in vitro/in vivo under the influence of an electrical field.

The aim of this study was to investigate the local changes in the ultrastructure of human skin after iontophoresis, using cryo-scanning, transmission and freeze fracture electron microscopy in human skin in vitro and in vivo. Human dermatomed skin was subjected to passive diffusion for 6 hours followed by nine hours of iontophoresis at 0.5 mA/cm2. The skin was processed and examined using both cryo-scanning electron microscopy (Cryo-SEM) and transmission electron microscopy (TEM). In addition, iontophoresis patches were applied to healthy volunteers for 3.5h with 0.5h of passive delivery followed by 3h of iontophoresis at a current density of 0.25 mA/cm2. Subsequently, a series of tape stripping were performed, which were visualized by freeze fracture transmission electron microscopy (FFTEM). In vitro, the cryo-scanning electron microscopy study revealed that electric current induced changes in the water distribution in the stratum corneum. Transmission electron microscopy showed no local changes in the ultrastructure of the stratum corneum; however, layers of detached corneocytes were frequently observed especially at the anodal site. In vivo, there was no evidence of perturbation of the stratum corneum lipid organization; however, changes in the fracture were noticed deeper in the stratum corneum at the anodal side, indicating a weakening of the desmosomal structure. The in vitro/in vivo studies suggest that iontophoresis results in the formation of intercellular water pools (in vitro observation) and a weakening of the desmosomal structure (in vivo observation) only in the upper part of the stratum corneum. However, no changes in the lipid organization were observed in vitro and in vivo at the current densities of 0.5 and 0.25 mA/cm2, respectively. Therefore, even at relatively high current densities, no drastic changes in the ultrastructure of the stratum corneum are observed. As far as structural changes in stratum corneum are concerned iontophoresis is therefore a safe method at the experimental conditions we used.

Physical stability of sonicated arsonoliposomes: effect of calcium ions.

The physical stability of sonicated arsonoliposomes in the absence and presence of Ca(2+) ions is evaluated. Cholesterol-containing arsonoliposomes composed of arsonolipids [having different acyl chains (C(12)-C(18))], or mixtures of arsonolipids with phospholipids (phosphatidylcholine or distearoyl-phosphatidylcholine) were prepared, and physical stability was evaluated in the absence and presence of CaCl(2), by vesicle dispersions turbidity measurements and cryo-electron microscopy morphological assessment. In some cases, vesicle zeta-potential was measured, under identical conditions. Results demonstrate that self-aggregation of the vesicles studied is low and influenced by the acyl chain length of the arsonolipid used, whereas calcium-induced aggregation is higher, correlating well with the decreased values of vesicle zeta-potential in the presence of Ca(2+) ions (weaker electrostatic repulsion). Acyl chain length of arsonolipids used has a significant quantitative effect on Ca(2+)-induced vesicle aggregation mainly for arsonoliposomes that contain phospholipids (mixed), compared with the vesicles that consist of plain arsonolipids (significant effect only for initial aggregation at time 0). Another difference between plain and mixed arsonoliposomes is that for mixed arsonoliposomes Ca(2+)-induced increases in turbidity are irreversible by ethylenediaminotetraacetic acid, suggesting that vesicle fusion is taking place. This was confirmed by cryo-electron microscopy observations. Finally, when phosphatidylcholine is replaced by distearoyl-phosphatidylcholine, arsonoliposomes are more stable in terms of self-aggregation, but in the presence of calcium, the turbidity and morphology results are similar.

The effect of pH on the electrophoretic behaviour of a new class of liposomes: arsonoliposomes.

Herein we report the effect of pH on the surface charge of a new class of liposomes: arsonoliposomes. Plain or mixed arsonoliposomes with cholesterol (Chol) and distearoyl-phosphatidylcholine (DSPC) in 1:1 molar ratio were prepared with lauryl-(C12), myristoyl-(C14) and palmitoyl-(C16) acyl side chain arsonolipids. The one step hydration method was used for vesicle preparation and zeta potential measurements were performed in the pH range from 3 to 9. The results revealed that these lipids hold a negative surface charge at all pH values investigated. The presence of cholesterol in 1:1 molar ratio results in higher zeta potential compared with plain arsonoliposomes with the exception of palmitoyl-(C16) acyl chain arsonolipids in neutral and slightly basic pH values. Oppositely, the DSPC (1:1 molar ratio) containing arsonoliposomes had lower values of zeta potential compared with plain arsonoliposomes. Concluding, the experimental results reveal that zeta potential of arsonoliposomes is indeed modified when the vesicles are incubated in environments with different acidity. In most cases these changes are in accordance with the ionization pattern of the arsonolipid headgroup, while some peculiar deviations may be connected with the known difference in the structure between some of the vesicle types studied.

Liposomes encapsulating prednisolone and prednisolone-cyclodextrin complexes: comparison of membrane integrity and drug release.

Inclusion complexes of prednisolone (PR) with beta-cyclodextrin (beta-CD) and hydropropyl-beta-cyclodextrin (HPbeta-CD) were formed by the solvation method, and were characterized by DSC, X-ray diffractometry and FT-IR spectroscopy. PC liposomes incorporating PR as plain drug or inclusion complex were prepared using the dehydration-rehydration method and drug entrapment as well as drug release were estimated for all liposome types prepared. The highest PR entrapment value (80% of the starting material) was achieved for PC/Chol liposomes when the HPbeta-CD-PR (2:1, mol/mol) complex was entrapped. The leakage of vesicle encapsulated 5,6-carboxyfluorescein (CF) was used as a measure of the vesicle membrane integrity. As judged from our experimental results liposomes which encapsulate beta-CD-PR complexes are significantly less stable (when their membrane integrity is considered) compared to liposomes of identical lipid compositions which incorporate plain drug or even (in some cases) non-drug incorporating liposomes, which were prepared and studied for comparison. Interestingly, liposomes which encapsulate HPbeta-CD-PR complexes, have very low initial CF latency values, indicating that the leakage of CF is a process of very high initial velocity. Interactions between lipid and cyclodextrin molecules may be possibly resulting in rapid reorganization of the lipid membrane with simultaneous fast release of CF molecules. The release of PR from liposomes was highest when the drug was entrapped in the form of a complex with beta-CD. Nevertheless, the very high entrapment ability of PR in the form of HPbeta-CD-PR complexes in comparison to plain drug is a indubitable advantage of this approach.

Physicochemical properties of liposomes incorporating hydrochlorothiazide and chlorothiazide.

In an attempt to study the effect of hydrophobic drugs on liposome properties, multilamellar liposomes (MLV) consisting of phosphatidylcholine (PC) and incorporating chlorothiazide (CT) or hydrochlorothiazide (HCT), were prepared and characterized. Liposome size, surface charge, stability (in buffer, plasma and sodium cholate) and calcium-induced aggregation were studied for drug-incorporating liposomes and empty liposomes for comparison. Results show that drug incorporation affects liposome size, z-potential and stability in presence of buffer and plasma proteins. Indeed, drug-incorporating liposomes are slightly larger and have a negative surface charge, which increases with the amount of drug incorporated in the lipid membrane. The membrane integrity of drug incorporating liposomes (in absence and presence of plasma proteins) is significantly higher when compared with that of empty liposomes (for both drugs studied). On the contrary, vesicle membrane integrity in presence of sodium cholate and calcium induced vesicle aggregation, are not affected by drug incorporation. Leakage of thiazides from liposomes was demonstrated to be induced by dilution. Low amounts of thiazides (around 10-15%) are released when lipid concentration is over 0.1 mM, while further dilution increased drug leakage exponentially. Concluding, results demonstrate that the presence of HCT or CT in liposome membranes has a significant effect on main vesicle properties, which are known to influence vesicle targeting ability. Thereby, it is very interesting to continue studies in this respect, especially with more lipophilic drugs.

Liposome-coated metal stents: an in vitro evaluation of controlled-release modality in the ureter.

PURPOSE: In vitro preparation of liposome-covered metal stents and loading of liposomal drug formulations that will slowly release the drug in the vicinity of the stent. MATERIALS AND METHODS: Polytetrafluoroethylene-coated stents were used. Large multilamellar (MLV) liposomes (phosphatidylcholine:cholesterol 1:1 mol/mol), empty or entrapping the corticosteroid anti-inflammatory drug, dexamethasone, were prepared by the thin-film hydration method and applied to pieces of stent using a simple and mild evaporation technique. Initially, a freeze-drying method for applying liposomes to stents was also evaluated, but it failed to produce stents that efficiently retain liposomal lipid when incubated in an aqueous environment. The presence of liposomes on the stent surface was confirmed by scanning electron microscopy. RESULTS: After analyzing the release of liposomal lipid (using a phospholipid assay) and liposomal drug (by a modified dexamethasone high-pressure liquid chromatography method) in an in vitro system developed to simulate in vivo conditions, it was found that 39.11+/-6.8% of the lipid and 50.84+/-5.48% of the drug was released from the stent pieces during 48 hours of incubation in the presence of artificial urine. The amount of dexamethasone released from stents during their application procedure was found to be negligible in an in vitro dry run. CONCLUSION: The use of stent-associated liposomal drug formulations as slow-release depots could be an efficient method of treating the untoward event of ureteral stent obstruction.