Anthocyanidins but not anthocyanins inhibit P-glycoprotein-mediated calcein extrusion - possible implication for orally administered drugs.

P-glycoprotein (P-gp) inhibition represents a promising therapeutic strategy for oncologic patients. The inhibition by naturally occurring anthocyans would bring certain benefits. Unfortunately, due to the low bioavailability and consequently low blood level, they cannot be used for cancer therapy. However, due to the food supplementation, significant concentration can raise up in the intestine, where P-gp is abundantly expressed. As many drugs are orally taken, simultaneous administration might affect the concentration of these drugs in the blood. Here, we found that anthocyanidins (aglycons) but not anthocyanins (glycosides) can significantly inhibit P-gp up to 60% of positive control, verapamil. This inhibitory activity was observed for 500 µm concentrations of malvidin and pelargonidin. We conclude that these compounds may be the source of food-drug interactions either for orally taken drugs or for intravenously administered drugs eliminated via biliary excretion which are the substrates of P-gp.

Effect of PEGylated lipid and Lecinol S-10 on physico-chemical properties and encapsulation efficiency of palmitoleate-palmitoleic acid vesicles.

A vesicle is a microscopic particle composed of a lipid bilayer membrane that separates the inner aqueous compartment from the outer aqueous environment. Palmitoleate-palmitoleic acid vesicles were prepared and their physico-chemical properties were investigated. Moreover, mixed vesicles composed of palmitoleic acid and PEGylated lipid and/or a mixture of phospholipids were also prepared. The stabilizing effects of these double-chain lipids on the formation of palmitoleate-palmitoleic acid vesicles were studied. Stability of the vesicle suspension was examined using particle size and zeta potential at 30 °C. The magnitude of the zeta potential was relatively lower in the vesicle suspension with the presence of phospholipid. Although some of the mixed vesicles that were formed were not very stable, they displayed potential for encapsulating the active ingredient calcein and the encapsulation efficiencies of calcein were encouraging. The palmitoleate-palmitoleic acid-DPPE-PEG2000 vesicle showed the most promising stability and encapsulation efficiency.

Short-term PTH administration increases dentine apposition and microhardness in mice.

OBJECTIVE: The purpose of this study is to investigate the effects of intermittent parathyroid hormone (PTH) administration on the apposition rate and structural features of dentine from mouse incisors. METHODS: Young male A/J Unib mice were treated daily for 6 and 10 days with 40 µg/kg of hPTH 1-34 or a vehicle. Dentine apposition rates measured by fluorescent labels (tetracycline and calcein) and alkaline phosphatase (ALP) plasma levels were evaluated after 6 days of treatment. Knoop microhardness testing and element content measurements in at.% of calcium (Ca), phosphorus (P), oxygen (O), and magnesium (Mg) in the peritubular and intertubular dentine were performed by Energy Dispersive X-ray (EDX) microanalysis via Scanning Electron Microscopy (SEM) after 10 days of treatment. RESULTS: Histometric analysis revealed an increase of 5% in the apposition rate of dentine and 25% in the ALP plasma levels in the PTH treated group. In addition, knoop microhardness testing revealed that the animals treated with PTH had a greater microhardness (11%). EDX microanalysis showed that PTH treatment led to increases in P (23%) and Ca (53%) at.% content, as well as the Ca/P ratio (24%) in peritubular dentine. The chemical composition of intertubular dentine did not vary between the groups. CONCLUSIONS: These findings indicate that intermittent administration of hPTH (1-34) increases apposition and mineralization of the dentine during young mice incisor formation.

Triggered content release from optimized stealth thermosensitive liposomes using mild hyperthermia.

Liposomes are potent nanocarriers to deliver chemotherapeutic drugs to tumors. However, the inefficient drug release hinders their application. Thermosensitive liposomes (TSL) can release drugs upon heat. This study aims to identify the optimum 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG(2000) (DSPE-PEG(2000)) concentration in stealth TSL to improve content release efficiency under mild hyperthermia (HT). TSL were prepared with DSPE-PEG(2000) from 1 to 10 mol%, around 80 nm in size. Quenched carboxyfluorescein (CF) in aqueous phase represented encapsulated drugs. In vitro temperature/time-dependent CF release and TSL stability in serum were quantified by fluorometry. In vivo CF release in dorsal skin flap window chamber models implanted with human BLM melanoma was captured by confocal microscopy. In vitro heat triggered CF release increased with increasing DSPE-PEG(2000) density. However, 6 mol% and higher DSPE-PEG(2000) caused CF leakage at physiological temperature. TSL with 5 mol% DSPE-PEG(2000) were stable at 37 degrees C, while released 60% CF in 1 min and almost 100% CF in 1h at 42 degrees C. In vivo optical intravital imaging showed immediate massive CF release above 41 degrees C. In conclusion, incorporation of 5 mol% DSPE-PEG(2000) optimized stealth TSL content release triggered by HT.

Long-circulating, pH-sensitive liposomes sterically stabilized by copolymers bearing short blocks of lipid-mimetic units.

A major hurdle towards in vivo utilization of pH-sensitive liposomes is their prompt sequestration by reticuloendothelial system and hence short circulation time. Prolonged circulation of liposomes is usually achieved by incorporation of pegylated lipids, which have been frequently reported to deteriorate the acid-triggered release. In this study we evaluate the ability of four novel nonionic copolymers, bearing short blocks of lipid-mimetic units to provide steric stabilization of DOPE:CHEMs liposomes. The vesicles were prepared using the lipid film hydration method and extrusion, yielding liposomes of 120-160 nm in size. Their pH-sensitivity was monitored via the release of encapsulated calcein. The incorporation of the block copolymers at concentration up to 10 mol% did not deteriorate the pH-sensitivity of the liposomes. A selected formulation was tested for stability in presence of 25% human plasma and proved to significantly outclass the plain DOPE:CHEMs liposomes. The ability of calcein-loaded liposomes to deliver their cargo inside EJ cells was investigated using fluorescent microscopy and the results show that the surface-modified vesicles are as effective to ensure intracellular delivery as plain liposomes. The pharmacokinetics and organ distribution of a selected formulation, containing a copolymer bearing four lipid anchors was investigated in comparison to plain liposomes and PEG (2000)-DSPE stabilized liposomes. The juxtaposition of the blood clearance curves and the calculated pharmacokinetic parameters show that the block copolymer confers superior longevity in vivo. The block copolymers utilized in this study can be consider as promising sterically stabilizing agents for pH-sensitive liposomes.

Chorioretinal temperature monitoring during transpupillary thermotherapy for choroidal neovascularisation.

AIMS: To investigate the difference in temperature rise between normal choroid and choroidal revascularisation (CNV) during transpupillary thermotherapy (TTT) and the relation between laser spot size and power in the rat fundus. METHODS: A modified slit lamp, which was installed with two laser wavelengths (490 nm for illumination and fluorescein excitation and 810 nm for hyperthermia), was developed for TTT and temperature monitoring. Temperature rise during TTT was monitored by observing fluorescence released from thermosensitive liposomes encapsulating carboxyfluorescein. Two types of liposomes were prepared; their phase transition temperatures were 40 degrees C and 46 degrees C, respectively. Laser power settings required to observe fluorescence released from 46 degrees C liposome in normal choroid or CNV were compared. Next, the power settings with 0.5 mm and 0.25 mm spot sizes were compared following administration of 40 degrees C liposome or 46 degrees C liposome. RESULTS: The minimum power values when release from 46 degrees C liposome was observed showed a significant difference in distribution of power values between normal choroid and CNV. CNV required significantly higher power than normal choroid. With 40 degrees C liposome, the power was 9.7 (1.9) mW (mean (SD)) at a spot size of 0.25 mm, and 12.1 (1.6) mW at 0.5 mm, respectively. When using 46 degrees C liposome, the power setting was 10.2 (1.2) mW at a spot size of 0.25 mm, and 14.6 (2.2) mW at 0.5 mm, respectively. CONCLUSIONS: CNV demonstrated varying heat conduction, compared with normal choroid. Laser power required to raise the temperature should not necessarily be doubled, even when the spot size is doubled. Close attention should be given to the selection of power settings when performing TTT for CNV.

Noninvasive technique for monitoring chorioretinal temperature during transpupillary thermotherapy, with a thermosensitive liposome.

PURPOSE: To develop a technique for noninvasive and real-time monitoring of chorioretinal temperature in transpupillary thermotherapy (TTT). METHOD: A modified slit lamp, which was equipped with two laser wavelengths (490 nm for illumination and fluorescein excitation and 810 nm for hyperthermia), was developed for TTT and temperature monitoring. Five types of liposomes were prepared, and their phase-transition temperatures were 40 degrees C, 46 degrees C, 47 degrees C, 48 degrees C, and 52 degrees C, respectively. Carboxyfluorescein was encapsulated in each liposome. After intravenous injection of each liposome, TTT with the modified slit lamp was performed on normal rat choroid or tissue with choroidal neovascularization (CNV). During TTT, chorioretinal temperature was monitored by observing release of fluorescein from circulating liposomes. RESULTS: Fluorescence from liposomes was initially observed around the heated lesion immediately after TTT began and disappeared rapidly when irradiation stopped. Choroidal and retinal temperatures were monitored separately. TTT for normal retina required higher power than that for normal choroid to observe fluorescence from a 40 degrees C, 46 degrees C, and 47 degrees C liposome. Retinal whitening was observed after TTT at a high-power setting. TTT for CNV required higher laser power than that for the normal choroid and retina. CONCLUSIONS: The results demonstrate the potential use of a noninvasive monitoring technique of chorioretinal temperature during TTT. The method should be useful to establish the TTT setting and achieve the optimal temperature increase in CNV.

A non-ionic surfactant vesicle-in-water-in-oil (v/w/o) system: potential uses in drug and vaccine delivery.

An aqueous dispersion of niosomes (non-ionic surfactant vesicles) emulsified in an external oil phase forms the vesicle-in-water-in-oil (v/w/o) system described in this paper. The properties of the surfactant used to form the vesicles, the surfactant or surfactant mixture used to stabilize the emulsion and the nature of the oil phase can be changed to provide systems of different capacities for drug or antigen and different release characteristics. The same nonionic surfactant is used as the principle amphipile to form the niosomes and to stabilize the w/o emulsion, thus promoting stability by decreasing transfer of surfactant between the stabilizing monolayers and the vesicle bilayers. The in vitro release of carboxyfluoroscein and 5-fluorouracil encapsulated within the niosomes of the v/w/o system has been investigated, the nature of the oil phase and surfactant-oil interactions being important in determining the rate of solute release. Initial studies of the system in vivo, as an adjuvant for tetanus toxoid, using cottonseed oil as the external oil phase, showed enhanced immunological activity over the free antigen or vesicles.

The ophthalmic rod: a new ophthalmic drug delivery system I.

The ophthalmic rod (OR) is a new drug delivery system, intended as an alternative to conventional therapy in ophthalmology. The rod is made of a nontoxic plastic. It is dipped into a drug solution which after drying forms a thin homogeneous coating. The OR is then packed and sterilized by gamma radiation. The effects of radiation on the contents of the drugs were studied using IR, UV, and thin-layer chromatography (TLC). Sterility, dose variation, and simulated drug delivery in vitro were tested. Pure drugs were used; no preservatives were included. To deliver the drug, the tip of the rod is introduced into the conjunctival sac and rubbed against the palpebral conjunctiva of the lower lid. ORs with tropicamide, oxybuprocaine HCl, pilocarpine HCl, and fluorescein sodium were used. The behavior of the drugs administered by this system was compared with eyedrops. Results of trials with three drugs, i.e., tropicamide, oxybuprocaine HCl, and fluorescein sodium on ORs applied to the eyes of humans and those of the rabbit are discussed.

Enhancing effect of absorption promoters on percutaneous absorption of a model dye (6-carboxyfluorescein) as poorly absorbable drugs. II. Study on the absorption promoting effect of azone.

The percutaneous absorption of drugs was investigated in rats by measuring plasma levels, using mainly 6-carboxyfluorescein (CF) as a model of poorly absorbable drugs. Azone (AZ), a new useful promoter for the percutaneous absorption of drugs, was used instead of dimethylsulfoxide. We have examined the effects of the solubilized state and concentration of AZ on the percutaneous absorption of CF. AZ was dissolved with the aid of surface-active agents, beta-cyclodextrin (CD) or dimethyl-beta-cyclodextrin (DMCD). When AZ (2 v/v%) was dissolved completely by a surface-active agent (HCO-60: polyoxyethylene hardened castor oil derivative), plasma CF levels showed the highest value. Plasma CF levels following the administration of CF with AZ which formed a complex with CD or DMCD were scarcely increased as compared to that of CF alone. In the case of fluorescin (FL), which has a higher partition coefficient than CF, the percutaneous absorption of FL was more enhanced by the addition of AZ than in the case of CF.