Nanotoxicity of poly(n-butylcyano-acrylate) nanoparticles at the blood-brain barrier, in human whole blood and in vivo.

Therapy of diseases of the central nervous system is a major challenge since drugs have to overcome the blood-brain barrier (BBB). A powerful strategy to enhance cerebral drug concentration is administration of drug-loaded poly(n-butylcyano-acrylate) (PBCA) nanoparticles coated with polysorbate 80 (PS80). This study evaluates the toxicity of PBCA-nanoparticles at the BBB, representing the target organ, the inflammatory response in human whole blood, as the site of administration and in a rat model in vivo. PBCA-nanoparticles were prepared by a mini-emulsion method and characterized concerning size, surface charge, shape and PS80-adsorption. The influence on metabolic activity, cell viability and integrity of the BBB was analyzed in an in vitro model of the BBB. In ex vivo experiments in human whole blood the release of 12 inflammatory cytokines was investigated. In addition, the inflammatory response was studied in vivo in rats and complemented with the analysis of different organ toxicity parameters. PBCA-nanoparticles showed time- and concentration-dependent effects on metabolic activity, cell viability and BBB integrity. No cell death or loss of metabolic activity was observed for nanoparticle-concentrations ≤500µg/ml up to 3h of treatment. Within 12 tested inflammatory cytokines, only interleukin-8 displayed a significant release after nanoparticle exposure in human blood. No severe inflammatory processes or organ damages were identified in rats in vivo. Thus, PBCA-nanoparticles are a promising drug delivery system to overcome the BBB since they showed hardly any cytotoxic or inflammatory effect at therapeutic concentrations and incubation times.

Brain delivery of camptothecin by means of solid lipid nanoparticles: formulation design, in vitro and in vivo studies.

For the purpose of brain delivery upon intravenous injection, formulations of camptothecin-loaded solid lipid nanoparticles (SLN), prepared by hot high pressure homogenisation, were designed. Incorporation of camptothecin in the hydrophobic and acidic environment of SLN matrix was chosen to stabilise the lactone ring, which is essential for its antitumour activity, and for avoiding premature loss of drug on the way to target camptothecin to the brain. A multivariate approach was used to assess the influence of the qualitative and quantitative composition on the physicochemical properties of camptothecin-loaded SLN in comparison to plain SLN. Mean particle sizes of ≤200 nm, homogenous size distributions and high encapsulation efficiencies (>90%) were achieved for the most suitable formulations. In vitro release studies in plasma, showed a prolonged release profile of camptothecin from SLN, confirming the physical stability of the particles under physiological pH. A higher affinity of the SLN to the porcine brain capillary endothelial cells (BCEC) was shown in comparison to macrophages. MTT studies in BCEC revealed a moderate decrease in the cell viability of camptothecin, when incorporated in SLN compared to free camptothecin in solution. In vivo studies in rats showed that fluorescently labelled SLN were detected in the brain after i.v. administration. This study indicates that the camptothecin-loaded SLN are a promising drug brain delivery system worth to explore further for brain tumour therapy.

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. METHODS: Aqueous suspension and solution formulations of ketoprofen with and without P-188 were orally administered to fasted male Wistar rats. The intrinsic dissolution rate and solubility of ketoprofen in simulated intestinal fluid, in both the presence and absence of P-188, was measured. KEY FINDINGS: The AUC and C(max) were found to be significantly enhanced when ketoprofen was administered as suspension and P-188 was present in the formulation (Susp P-188) as compared to the surfactant-free formulation (∼4-fold higher AUC, 7-fold higher C(max) ). While drug solubility appeared to be almost unaffected by P-188, a significantly faster dissolution was observed. In addition, the influence of P-188 on the drug absorption process was investigated by comparison of solution formulations with and without P-188. CONCLUSIONS: The in-vivo performance of these solutions, a pure buffer solution and a P-188-containing buffer solution showed no significant difference, suggesting that the increase in bioavailability for Susp P-188 was primarily a consequence of the dissolution rate-enhancing effect.

The ABC of the blood-brain barrier - regulation of drug efflux pumps.

According to the World Health Organization Central nervous system disorders are the major medical challenge of the 21st Century, yet treatments for many CNS disorders are either inadequate or absent. One reason is the existence of the blood-brain barrier, which strictly limits the access of substances to the brain. A key element of the barrier function is the expression of ABC export proteins in the luminal membrane of brain microvessel endothelial cells. Understanding the signaling cascades and the response to endogenous and exogenous stimuli, which lead to altered expression or function of the transporters as well as subsequent modulation of the transporters, may offer novel strategies to overcome the barrier and to improve drug delivery to the brain. This review gives a short overview about structure of the key elements of the blood-brain barrier with emphasis on ABC transporters. An insight into regulation of function and expression of these transport proteins is given and the involvement of these transporters in CNS diseases is discussed.

Delivery of nanoparticles to the brain detected by fluorescence microscopy.

This study aimed to explore and extend the application potential of poly(n-butylcyano-acrylate) (PBCA) nanoparticles to cross the blood-brain barrier (BBB) and to deliver their content into the central nervous system. PBCA particles were prepared by a new and efficient mini-emulsion method with excellent yield and reproducibility. These nanoparticles were loaded with 1.5% (w/v) fluorescein-isothio-cyanate-dextran (FITC-dextran), 1.5% rhodamine-123 or 7.3% doxorubicin. Particles were characterized by dynamic light scattering determining particle size, polydispersity index and zeta-potential. They were coated with 10% w/v polysorbate 80 and administered to rats. Cryosections of the brain were prepared and time-dependent distribution of fluorescence was studied. After the administration of polysorbate 80-coated particles by carotic injection, fluorescence could first be detected in capillary lumina with a progressive shift to capillary endothelial cells at 30min and a rather evenly spread distribution across the brain tissue at 60min after administration. 60min after administration into the tail vein, fluorescent particles could be assigned to endothelial cells, whereas after 2h a rather evenly spread distribution across the brain tissue was seen. These observations indicate that surface-coated PBCA nanoparticles are able to cross the blood-brain barrier and to serve as a drug-delivery system to the central nervous system.