Atomic force microscopy and photon correlation spectroscopy: two techniques for rapid characterization of liposomes.

The direct evaluation of the heterogeneity of the particle population of nanometric drug delivery systems as liposomes is difficult to achieve owing to the dimension and the carrier characteristics. The influence of the lipidic ratio and composition on the physical stability of liposomes during their storage was investigated using atomic force microscopy (AFM) and photon correlation spectroscopy (PCS). Liposomes were made by a mixture of different lipids and obtained using distinct methods of preparation. AFM images, acquired immediately after the deposition of the sample on mica surface, clearly showed the spherical shape of the lipidic vesicles. In all the 7 months of the experiment, the average sizes of the different liposomes evaluated using the two techniques were comparable. According to PCS analysis, AFM images confirmed that almost all the diversified vesicular systems tended to form aggregates during their storage; this loss of stability was strengthened by the increase of polydispersity index value. The different behaviours observed were to ascribe to the lipidic composition more than the methods of liposome preparation. In conclusion, AFM technique owing to the relative simplicity cold be useful for the technological control of size distribution profile according to the preparative factors and moreover to the batch-to-batch reproducibility.     

Targeting the thyroid gland with thyroid-stimulating hormone (TSH)-nanoliposomes

Various tissue-specific antibodies have been attached to nanoparticles to obtain targeted delivery. In particular, nanodelivery systems with selectivity for breast, prostate and cancer tissue have been developed. Here, we have developed a nanodelivery system that targets the thyroid gland. Nanoliposomes have been conjugated to the thyroid-stimulating hormone (TSH), which binds to the TSH receptor (TSHr) on the surface of thyrocytes. The results indicate that the intracellular uptake of TSH-nanoliposomes is increased in cells expressing the TSHr. The accumulation of targeted nanoliposomes in the thyroid gland following intravenous injection was 3.5-fold higher in comparison to untargeted nanoliposomes. Furthermore, TSH-nanoliposomes encapsulated with gemcitabine showed improved anticancer efficacy in vitro and in a tumor model of follicular thyroid carcinoma. This drug delivery system could be used for the treatment of a broad spectrum of thyroid diseases to reduce side effects and improve therapeutic efficacy.     

A novel animal model to evaluate the ability of a drug delivery system to promote the passage through the BBB

The purpose of this investigation was to explore the potentiality of a novel animal model to be used for the in vivo evaluation of the ability of a drug delivery system to promote the passage through the blood–brain barrier (BBB) and/or to improve the brain localization of a bioactive compound. A Tween 80^®-coated poly-l-lactid acid nanoparticles was used as a model of colloidal drug delivery system, able to trespass the BBB. Tacrine, administered in LiCl pre-treated rats, induces electrocorticographic seizures and delayed hippocampal damage. The toxic effects of tacrine-loaded poly-l-lactid acid nanoparticles (5 mg/kg), a saline solution of tacrine (5 mg/kg) and an empty colloidal nanoparticle suspension were compared following i.p. administration in LiCl-pre-treated Wistar rats. All the animals treated with tacrine-loaded nanoparticles showed an earlier outcome of CNS adverse symptoms, i.e. epileptic onset, with respect to those animals treated with the free compound (10 min vs. 22 min respectively). In addition, tacrine-loaded nanoparticles administration induced damage of neuronal cells in CA1 field of the hippocampus in all treated animals, while the saline solution of tacrine only in 60% of animals. Empty nanoparticles provided similar results to control (saline-treated) group of animals. In conclusion, the evaluation of time-to-onset of symptoms and the severity of neurodegenerative processes induced by the tacrine–lithium model of epilepsy in the rat, could be used to evaluate preliminarily the capability of a drug delivery system to trespass (or not) the BBB in vivo.     

Novel PEG-coated niosomes based on bola-surfactant as drug carriers for 5-fluorouracil

Innovative niosomes made up of α,ω-hexadecyl-bis-(1-aza-18-crown-6) (bola), Span 80® and cholesterol (2:5:2 molar ratio) are proposed as suitable delivery systems for the administration of 5-fluorouracil (5-FU), an antitumoral compound largely used in the treatment of breast cancer. The bola-niosomes, after sonication procedure, showed mean sizes of ~200 nm and a loading capacity of ~40% with respect to the amount of 5-FU added during the preparation. Similar findings were achieved with PEG-coated bola-niosomes (bola, Span 80®, cholesterol, DSPE-mPEG2000, 2:5:2:0.1 molar ratio respectively). 5-FU-loaded PEG-coated and uncoated bola-niosomes were tested on MCF-7 and T47D cells. Both bola-niosome formulations provided an increase in the cytotoxic effect with respect to the free drug. Confocal laser scanning microscopy studies were carried out to evaluate both the extent and the time-dependent bola-niosome-cell interaction. In vivo experiments on MCF-7 xenograft tumor SCID mice models showed a more effective antitumoral activity of the PEGylated niosomal 5-FU at a concentration ten times lower (8 mg/kg) than that of the free solution of the drug (80 mg/kg) after a treatment of 30 days.     

Lecithin microemulsions for the topical administration of ketoprofen: percutaneous adsorption through human skin and in vivo human skin tolerability

The potential application of highly biocompatible o/w microemulsions as topical drug carrier systems for the percutaneous delivery of anti-inflammatory drugs, i.e. ketoprofen, was investigated. Microemulsions were made up of triglycerides as oil phase, a mixture of lecithin and n-butanol as a surfactant/co-surfactant system and an aqueous solution as the external phase. To evaluate the percutaneous enhancing effect of oleic acid, this compound was used as a component of some o/w microemulsions. The topical carrier potentialities of lecithin-based o/w microemulsions were compared with respect to conventional formulations, i.e. a w/o emulsion, a o/w emulsion and a gel. Physicochemical characterisation of microemulsions was carried out by light scattering and zeta potential analyses. Microemulsions showed mean droplet size < 35 nm and a negative zeta potential, that is -39.5 mV for the oleic acid-lecithin microemulsion and -19.7 mV for the lecithin-based microemulsion. The percutaneous adsorption of the various topical formulations was evaluated through healthy adult human skin, which was obtained from abdominal reduction surgery. Ketoprofen-loaded microemulsions showed an enhanced permeation through human skin with respect to conventional formulations. No significant percutaneous enhancer effect was observed for ketoprofen-loaded oleic acid-lecithin microemulsions. The human skin tolerability of various microemulsion formulations was evaluated on human volunteers. Microemulsions showed a good human skin tolerability.     

Structure-activity relationships in carboxamide derivatives based on the targeted delivery of radionuclides and boron atoms by means of peripheral benzodiazepine receptor ligands

The structure-activity relationship studies on 2-quinolinecarboxamide peripheral benzodiazepine receptor (PBR) ligands have been refined with the aim of using these ligands as carriers of radionuclides and boron atoms. Some new ligands show enhanced affinity and steroidogenic activity with respect to reference compound 1 and are interesting candidates for radiolabeling and PET studies. Moreover, carborane derivative 3q, representing the first example of PBR ligand bearing a carborane cage, can be useful to explore an alternative mechanism in BNCT.     

Liposomes as a potential drug carrier for citicoline (CDP-choline) and the effect of formulation conditions on encapsulation efficiency.

In this paper we report the investigation of the potential of liposomes as drug carrier for citicoline (1; CDP-choline). The aim of our work is to improve the pharmacokinetic and pharmacodynamic parameters of the drug to facilitate the overcoming of the blood-brain barrier. The thermotropic behaviour of hydrated dispersions of various phospholipids and their mixtures containing 1 have been investigated by differential scanning calorimetry (DSC) to have a clear view of the interaction between the drug and the liposome phospholipids. By the values of transition peak temperature (Tm) and transition enthalpy (delta H) we note a strong interaction between 1 and the polar heads of L-alpha-dipalmitoylphosphatidic acid (DPPA) and L-alpha-dipalmitoylphosphatidylserine (DPPS), whereas there is not any considerable interaction between the drug and L-alpha-dipalmitoylphosphatidylcholine (DPPC) or L-alpha-dimyristoylphosphatidylcholine (DMPC); in any case no interaction occurs between 1 and the hydrophobic part of the phospholipid. So we conclude that all the drug is fitted into the aqueous spaces. The results of the encapsulation efficiency experiments demonstrate how the encapsulation capacity increase with using charged phospholipids, reaching the top with DPPA. Moreover, it was noted that the presence of Cholesterol (Chol) enhances the encapsulation capacity (EC) and drug content (DC) values of DPPC, a neutral phospholipid. The size of the liposomes was determined by light scattering (LS).     

Simultaneous spectrophotometric determination in solid phase of aspirin and its impurity salicylic acid in pharmaceutical formulations.

We report the simultaneous determination of aspirin and its hydrolysis product, salicylic acid, in solid phase by fluorescence spectrophotometry. Aspirin is often the most labile component in a combination-type analgesic compound. Therefore, its stability is often the initial concern in any formulation-screening program. Preliminary screening of a large number of potential formulations can be arduous, because most current methods of analysis generally consist of several steps: extractions or column separations followed by UV, colorimetric, or gas-liquid chromatographic assays. The method proposed here is quite suited to large numbers of assays because it is not time consuming, it is straightforward, and it is not subject to interference from the substances present in the pharmaceutical formulations. In addition, the method is nondestructive, not dependent on the sampling procedure, and, above all, quite sensitive.     

Physicochemical and biopharmaceutical characterization of endo-2-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-1H-benz[e]isoindol-1-one (CR3124) a novel potent 5-HT3 receptor antagonist

The physicochemical and biopharmaceutical properties, such as pK(a), crystal habit, water solubility, logD, molecular structure and dynamics, and membrane permeability of CR3124 (endo-2-(8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dihydro-1H-benz[e]isoindol-1-one, a novel potent 5-HT(3) receptor antagonist) have been studied in order to obtain preformulation information. The study showed that CR3124 is a very rigid molecule in which conformational freedom due to the presence of a rotatable bond is restricted by the interaction between an activated hydrogen and the amide oxygen and the conformation of the tropane piperidine ring is regulated by the environment in such a manner as to optimize the intermolecular interactions with the solvent. This chameleon behavior appears to be capable of explaining the biopharmaceutical properties showed by CR3124, such as low wettability, relatively good solubility, and very high membrane permeability.     

Ethosomes? and transfersomes? containing linoleic acid: physicochemical and technological features of topical drug delivery carriers for the potential treatment of melasma disorders

Two vesicular colloidal carriers, ethosomes? and transfersomes? were proposed for the topical delivery of linoleic acid, an active compound used in the therapeutic treatment of hyperpigmentation disorders, i.e. melasma, which is characterized by an increase of the melanin production in the epidermis. Dynamic light scattering was used for the physicochemical characterization of vesicles and mean size, size distribution and zeta potential were evaluated. The stability of formulations was also evaluated using the Turbiscan Lab? Expert based on the analysis of sample transmittance and photon backscattering. Ethosomes? and transfersomes? were prepared using Phospholipon 100 G?, as the lecithin component, and ethanol and sodium cholate, as edge activator agents, respectively. Linoleic acid at 0.05% and 0.1% (w/v) was used as the active ingredient and entrapped in colloidal vesicles. Technological parameters, i.e. entrapment efficacy, drug release and permeation profiles, were also investigated. Experimental findings showed that physicochemical and technological features of ethosomes? and transfersomes? were influenced by the lipid composition of the carriers. The percutaneous permeation experiments of linoleic acid-loaded ethosomes? and transfersomes? through human stratum corneum-epidermidis membranes showed that both carriers are accumulated in the skin membrane model as a function of their lipid compositions. The findings reported in this investigation showed that both vesicular carriers could represent a potential system for the topical treatment of hyperpigmentation disorders.