Simultaneous quantification of Gemcitabine and Irinotecan hydrochloride in rat plasma by using high performance liquid chromatography-diode array detector

In this manuscript we aimed at the simultaneous separation and quantification of Gemcitabine and Irinotecan hydrochloride (injected both as single components and in combination) from Sprague Dawley rat plasma by using a validated method obtained through the use of a High Performance Liquid Chromatography (HPLC)-diode array detector (DAD). Gemcitabine and Irinotecan hydrochloride were detected and quantified using a Zorbax Extend C-18 column (250 mm × 4.6 mm; 5 μm particle size) in gradient elution mode. The chromatographic analyses were carried out in 15 min. The analytical mode was calibrated and validated in the concentration range from 0.1 to 18 μg/mL both for Gemcitabine and Irinotecan hydrochloride. Sprague Dawley rat plasma was used to perform the analysis. 3-methylxanthine was the internal standard. The weighted-matrix matched standard curves of Gemcitabine and Irinotecan hydrochloride showed a good linearity up to 18 μg/mL. Parallelism tests were also performed to evaluate whether the over-range samples could be analyzed after dilution without affecting the analytical performance. The intra- and inter-day precision (RSD%) values of Gemcitabine and Irinotecan hydrochloride were ≤7.14% and ≤11.5%, respectively. The intra- and inter-day trueness (Bias%) values were in the range from -11.5% to 1.70% for both drugs. The analytical mode performance was further tested after collecting Sprague Dawley rat plasma following a single-dose administration of chemotherapeutics or their association. The validated HPLC-DAD method allowed the simultaneous quantification of Gemcitabine and Irinotecan hydrochloride in the rat plasma, besides the evaluation of the pharmacokinetic parameters and drug delivery.

Bisphosphonate–polyaspartamide conjugates as bone targeted drug delivery systems

Poly-hydroxy-aspartamide was used as a backbone to synthesize bisphosphonate derivatives thus achieving macromolecular carriers to be potentially used as targeting agents for bone drug delivery.

Gemcitabine and tamoxifen-loaded liposomes as multidrug carriers for the treatment of breast cancer diseases

The effects of a lipid composition on the physico-chemical and technological properties of a multidrug carrier (MDC) containing both gemcitabine (GEM) and tamoxifen (TMX), as well as its in vitro antitumoral activity on different breast cancer cell lines, were investigated. In particular, the following three different liposomal formulations were prepared: DPPC/Chol/DSPE-mPEG2000 (6:3:1 molar ratio, formulation A), DPPC/Chol/DOTAP (6:3:1 molar ratio, formulation B) and DPPC/Chol/DPPG (6:3:1 molar ratio, formulation C). The colloidal systems were obtained by the TLE technique and the extrusion process allowed us to obtain vesicles having mean sizes of 150-200 nm, while the surface charges varied between 50 mV and -30 mV. Formulation A showed the best encapsulation efficiency between the two compounds and the presence of TMX influenced the release profile of GEM (hydrophilic compound) as a consequence of its effect on the fluidity of the bilayer. An MDC of formulation A was used to effectuate the in vitro cytotoxicity experiments (MTT-test) on MCF-7 and T47D cells. The liposomal MDC provided the best results with respect to the single drug tested in the free form or entrapped in the same liposomal formulation. The CLSM experiments showed a great degree of cell interaction of liposomal MDC after just 6h.

Drug delivery applications with ethosomes

Ethosomes are specially tailored vesicular carriers able to efficiently deliver various molecules with different physicochemical properties into deep skin layers and across the skin. This paper reviews the unique characteristics of the ethosomal carriers, focusing on work carried out with drug containing ethosomal systems in animal models and in clinical studies. The paper concludes with a discussion on the safety of the ethosomal system applications.

Retinoids: new use by innovative drug-delivery systems

BACKGROUND

Retinoids represent an old class of bioactives used in the treatment of different skin pathologies (such as acne and psoriasis) and in the treatment of many tumors. Unfortunately, they present several side effects, i.e., burning of skin and general malaise after systemic administration and they are very unstable after exposition to light.

METHODS

One of the most promising new approaches for reducing the side effects of retinoids while improving their pharmacological effect is the use of drug-delivery devices. This review explains the current status of retinoid drug transport, which has been developing over the last few years, explaining the modification of their biopharmaceutical properties in detail after encapsulation/inclusion in vesicular and polymeric systems.

RESULTS/CONCLUSION

Different colloidal and micellar systems containing retinoid drugs have been realized furnishing important potential advancements in traditional therapy.

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(R), 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.

Cytotoxic effects of a novel pyrazolopyrimidine derivative entrapped in liposomes in anaplastic thyroid cancer cells in vitro and in xenograft tumors in vivo

In this study, we evaluated the activity of two novel pyrazolopyrimidine derivatives (Si 34 and Si 35) against ARO cells, a human anaplastic thyroid cancer cell line. ARO cells exposed to different concentrations of the drugs showed a reduced growth rate and an increase of mortality. After 72 h incubation, doses of 5 and 10 microM Si 34 determined a decrease of cell counts by approximately 25% and approximately 75% compared with those of control cells respectively. Similar findings were observed using Si 35. Treatment with both Si 34 and Si 35 at 10 microM increased cell mortality also ( approximately 29% and approximately 18% respectively). At these concentrations, a decrease in cyclin D1 levels was observed. To improve the biopharmaceutical properties, a liposome formulation was prepared. When entrapped in unilamellar liposomes, Si 34 exerted its cytotoxic effects even at lower doses (maximal inhibition at 5 microM) and after shorter incubation time (48 h) either in ARO or other thyroid cancer cell lines. The effects were associated with weak apoptotic death. Inhibition of epidermal growth factor-stimulated src and ERK phosphorylation, as well as reduction of migration properties of ARO cells was also observed. Moreover, the growth of tumor xenografts induced in severe combined immunodeficiency (SCID) mice was inhibited by i.v. administration of 25-50 mg/kg of the drug liposomal formulation. In conclusion, the liposomal preparation of this novel pyrazolopyrimidine derivative appears to be a promising tool for the treatment of anaplasic thyroid cancer.

Biomembrane model interaction and percutaneous absorption of papaverine through rat skin: effects of cyclodextrins as penetration enhancers

The effects of different concentrations of beta-cyclodextrin (beta-CyD), hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) on percutaneous absorption of papaverine hydrochloride (PAP) were investigated. Abdominal rat skin mounted in Franz cells was used for in vitro experiments. To evaluate CyD interaction with a bilayer structure model, dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and DPPC-Chol (8:2 mole ratio) vesicles were used. CyD vesicle interaction was evaluated by differential scanning calorimetry. Permeation through rat skin and calorimetric experiments demonstrated that at low concentrations DM-beta-CyD shows higher enhancer activity as a possible result of a perturbing action on the skin by a complexation of its lipid components, but at higher concentrations HP-beta-CyD is the most effective. By considering that HP-beta-CyD presents a very moderate destabilizing action on the skin, we conclude that a 10% aqueous solution of this macrocycle appears to be the most suitable transdermal absorption enhancer for PAP.

Ocular tolerability and in vivo bioavailability of poly(ethylene glycol) (PEG)-coated polyethyl-2-cyanoacrylate nanosphere-encapsulated acyclovir

Acyclovir-loaded polyethyl-2-cyanoacrylate (PECA) nanospheres were prepared by an emulsion polymerization process in the micellar phase and characterized. The influence of the presence of nonionic surfactant as well as other substances [i.e., 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) and poly(ethylene glycol) (PEG)], on formulation parameters and loading capacity was investigated. In particular, the presence of PEG resulted in an increase of mean size and size distribution. To obtain PEG-coated PECA nanospheres with a mean size of < 200 nm, Pluronic F68 at concentrations > 1.5% (w/v) should be used during preparation. The presence of PEG also resulted in a change in zeta potential, from -25.9 mV for uncoated nanospheres to -12.2 mV for PEG-coated PECA nanospheres. The presence of HP-beta-CyD elicited an increase of nanosphere size and size distribution, but zeta potential was not influenced. In vitro drug release from nanospheres was determined in both phosphate buffer (pH 7.4) and plasma. The presence of HP-beta-CyD and PEG did not influence the acyclovir release rate in plasma. In the case of release in phosphate buffer, PEG-coated nanospheres showed a slower release. Ocular tolerability of PEG-coated PECA nanospheres was evaluated by the in vivo Draize test. This colloidal carrier was well tolerated, eliciting no particular inflammation at the level of the various ocular structures. In vivo ocular bioavailability was evaluated by instilling 50 microL of the acyclovir-loaded nanospheres only once in the conjunctival sac of rabbit eyes. At various time intervals, aqueous humour acyclovir content was determined by high-performance liquid chromatography. Acyclovir-loaded PEG-coated PECA nanospheres were compared with an aqueous solution of the drug and a physical mixture of acyclovir nanospheres. The acyclovir-loaded PEG-coated PECA nanospheres showed a significant (p < 0.001) increase of drug levels (25-fold) in aqueous humor compared with the free drug or the physical mixture. This finding is probably due to an improved ocular mucoadhesion of PEG-coated PECA nanospheres.

Ofloxacin-loaded liposomes: in vitro activity and drug accumulation in bacteria

Different ofloxacin-loaded unilamellar vesicles were prepared by the extrusion technique, and their antimicrobial activities were determined in comparison to those of the free drug by means of MIC determinations with both American Type Culture Collection standards and wild-type bacterial strains (six strains of Enterococcus faecalis, seven strains of Escherichia coli, six strains of Staphylococcus aureus, and six strains of Pseudomonas aeruginosa). The accumulation of ofloxacin and liposome-ofloxacin was measured by determining the amount of the drug inside the bacteria as a function of time. Encapsulated fluoroquinolone yielded MICs which were at least twofold lower than those obtained with the free drug. In particular, liposomes made up of dimyristoylphosphatidylcholine-cholesterol-dipalmitoylphosphatidylser ine and dimyristoylphosphatidylcholine-cholesterol-dihexadecylphosphate (4:3:4 molar ratio) provided the best improvement in antimicrobial activity against the various bacterial strains investigated. The liposome formulation produced higher intracellular fluoroquinolone concentrations than those achieved simultaneously with the free drug in both E. coli and P. aeruginosa.

Reduction of maturation phenomenon in cerebral ischemia with CDP-choline-loaded liposomes

PURPOSE

Cerebral ischemia represents a serious therapeutic challenge. We investigated the therapeutic efficacy of CDP-choline-loaded liposomes against cerebral ischemia. The determination of post-ischemic brain recovery by EEG analysis was carried out to evaluate the effect of CDP-choline-loaded liposomes with respect to the free drug on the maturation of ischemic injury.

METHODS

Long-circulating unilamellar liposomes were prepared by a freeze and thaw procedure followed by an extrusion through polycarbonate membranes. Wistar rats were ischemized by bilateral clamping of the common carotid arteries. Free or liposomally entrapped drug was administered (20 mg/kg) just after ischemia and thereafter once a day for six days. Post-ischemic survival, neuronal membrane peroxidation and brain recovery (EEG analysis) were evaluated.

RESULTS

The post-ischemic reperfused rats treated with CDP-choline-loaded liposomes showed a higher survival rate than animals treated with the free drug. The delayed cerebral neurodegenerative injury due to an ischemic event, referred to as maturation phenomenon, was substantially reduced with the administration of the liposomal formulation. The liposomal carrier showed a marked protection against lipoperoxidative damage.

CONCLUSIONS

Liposomes ensured a rapid recovery of the damaged membranous structure of the neuronal cells, allowing a significant improvement of brain functionality. The reduction of the maturation phenomenon may probably be of particular importance in humans, where a fundamental problem is the quality of life after an ischemic event.

Characterization and in-vivo ocular absorption of liposome-encapsulated acyclovir

The potential of liposomes as an in-vivo ophthalmic drug delivery system for acyclovir was investigated. The drug-membrane interaction was evaluated by means of differential scanning calorimetry analysis. These experiments showed that acyclovir is able to interact with both positively and negatively charged membranes via electrostatic or hydrogen bonds. No interaction was observed with neutral membranes made up of dipalmitoylphosphatidylcholine. Different liposome preparation procedures were carried out to encapsulate acyclovir. The drug encapsulation mainly depends on the amount of water which the liposome system is able to entrap. In the case of multilamellar vesicles, charged systems showed the highest encapsulation efficiency. No particular difference in the encapsulation efficiency was observed for oligolamellar vesicles prepared with the reverse-phase evaporation technique. Oligolamellar liposomes showed the highest acyclovir encapsulation parameters and had release profiles similar to those of multilamellar liposomes. In-vivo experiments using male New Zealand albino rabbits were carried out to evaluate the aqueous humour concentration of acyclovir bioavailability. The most suitable ophthalmic drug delivery system was oligolamellar systems made up of dipalmitoylphosphatidylcholine-cholesterol-dimethyldioctadecyl glycerole bromide (7:4:1 molar ratio), which presented the highest encapsulation capacity and were able to deliver greater amounts of the drug into the aqueous humour than a saline acyclovir solution or a physical liposome/drug blend.

Liposomal delivery of a 30-mer antisense oligodeoxynucleotide to inhibit proopiomelanocortin expression

An oligodeoxynucleic sequence of 30 bases (30-mer ODN), complementary to a region of beta-endorphin mRNA, was synthesized to have an antisense effect with regard to the expression of this oligopeptide. Following the solid-phase synthesis of the oligodeoxynucleotide, the 30-mer ODN was encapsulated within liposomes to provide a higher resistance against DNases and an improved entrance into cells. The most suitable liposome formulation as a 30-mer ODN carrier consisted of small unilamellar vesicles (50 nm) with an encapsulation capacity of 4.76 microL/micromol. The liposomal formulations containing dipalmitoyl-DL-alpha-phosphatidyl-L-serine presented fusogenic properties, which are of great importance for the delivery of antisense compounds. The antisense activity of 30-mer ODN-loaded liposomes was evaluated by the determination of beta-endorphin levels in AtT-20 cells. The free 30-mer ODN did not provide any lowering of the beta-endorphin production, whereas the liposomally entrapped compound elicited a concentration-dependent inhibition. The inhibition was determined by a sequence-specific binding of the 30-mer ODN with the target mRNA.

Survival rate improvement in a rat ischemia model by long circulating liposomes containing cytidine-5I-diphosphate choline

Unilamellar liposomes made up of DPPC-DPPS-Chol (7:4:7 molar ratio) and ganglioside GM1 8% mol were used to deliver cytidine-5I-diphosphate choline (CDP-choline) to the brain. The liposomal suspension consisted of unilamellar vesicles with a mean size of 50 nm and a very narrow size distribution. The therapeutic effectiveness of CDP-choline-loaded liposomes was investigated by an in vivo model of cerebral ischemia on Wistar rats (320-350 g). The animals were made ischemic to different extents (5, 15 and 30 min) by bilateral clamping of the common carotid arteries. The effect of free and liposomally encapsulated CDP-choline on the survival rate of post-ischemic reperfused rats was evaluated. The liposome formulation was much more active against ischemic injury than the free CDP-choline, ensuring a noticeable improvement of the survival rate with regards to the free drug ranging from 45% to 100% as a function of the duration of the ischemic event.

Correlation of trimethoprim and brodimoprim physicochemical and lipid membrane interaction properties with their accumulation in human neutrophils

Dipalmitoylphosphatidylcholine vesicles were used as a biological membrane model to investigate the interaction and the permeation properties of trimethoprim and brodimoprim as a function of drug protonation. The drug-membrane interaction was studied by differential scanning calorimetry. Both drugs interacted with the hydrophilic phospholipid head groups when in a protonated form. An experiment on the permeation of the two drugs through dipalmitoylphosphatidylcholine biomembranes showed higher diffusion rate constants when the two drugs were in the uncharged form; lowering of the pH (formation of protonated species) caused a reduction of permeation. Drug uptake by human neutrophil cells was also investigated. Both drugs may accumulate within neutrophils; however, brodimoprim does so to a greater extent. This accumulation is probably due to a pH gradient driving force, which allows the two drugs to move easily from the extracellular medium (pH approximately 7.3) into the internal cell compartments (acid pH). Once protonated, both drugs are less able to permeate and can be trapped by the neutrophils. This investigation showed the importance of the physicochemical properties of brodimoprim and trimethoprim in determining drug accumulation and membrane permeation pathways.

Preparation and characterization of polyethyl-2-cyanoacrylate nanocapsules containing antiepileptic drugs

Biocompatible and biodegradable colloidal drug delivery systems can be obtained by means of in situ polymerization of alkylcyanoacrylate. In particular, nanocapsules of polyethylcyanoacrylate (PECA) were prepared by adding the monomer to an organic phase, consisting of Miglyol 812 and an organic solvent (ethanol, acetone or acetonitrile), and subsequently mixing the organic phase with an aqueous phase containing Pluronic F68 at different concentrations. The possible mechanism of formation and the influence of preparation conditions on the quality of nanocapsule formulations were investigated by freeze-fracture electron microscopy and laser light scattering using both the inverse Laplace transform and the standard cumulant analysis for data fitting. High-quality nanocapsule systems were obtained using an aprotic fully water-miscible organic solvent such as acetone. The presence of ethanol led to the formation of both nanospheres and nanocapsules. The concentrations of nonionic surfactant in the aqueous phase of monomer in the organic phase did not influence the kind of colloidal suspension obtained. The oil simply plays the role of monomer support. The diameter of PECA nanoparticles (nanospheres and nanocapsules) ranged from 100 to 400 nm. Three antiepileptic drugs (Ethosuximide, 5,5-diphenyl hydantoin and carbamazepine) were entrapped in PECA nanocapsules. The loading capacity of PECA nanocapsules, prepared using acetone as organic solvent, varied from 1% to 11% (drug/dried material) as a function of the solubility (affinity) of the different drugs with the oil core. This parameter also influenced the release from PECA nanocapsules, which was slower for drugs with a higher affinity for Miglyol 812. By encapsulating the three antiepileptic drugs in the PECA nanocapsules, it was possible to achieve controlled drug release. The mechanism of drug release from PECA nanocapsules was mainly diffusion from the oil core through the intact polymer barrier.

Synthesis and preliminary in vitro screening of lipophilic alpha, gamma-bis(amides) as potential prodrugs of methotrexate

As part of a program aimed at studying the feasibility of amide derivatives of methotrexate (MTX) as lipophilic prodrugs, with the aims of increasing passive cellular uptake and obtaining prolonged-release agents, we describe the synthesis of five long-chain alkyl bis(amides) of MTX, from decyl- to octadecylamide, by direct transamidation to the MTX diethyl ester. Compounds were subjected to a preliminary biological screening, to assess their inhibitory activity against bovine liver dihydrofolate reductase (DHFR) and in vitro antitumor activity against human leukemia CCRF-CEM cells. As a general trend, an increase in lipophilicity led to a linear reduction of enzyme inhibition; however, the bis(decyl)amide derivative showed a good intrinsic affinity for DHFR (IC50 6.41 nM), comparable to that of MTX diethyl ester and close to that of MTX (IC50 2.90 nM). In the antitumor assay, lower homologues (C10-C14) displayed an interesting activity profile, suggesting the desirability of additional studies with these and similar compounds.

Application of liposomes as potential cutaneous drug delivery systems. In vitro and in vivo investigation with radioactively labelled vesicles

The potential application of liposomes as dermal delivery systems was investigated, with regard to vesicle composition and size. Liposomes were made up of phospholipids or skin lipids, referred to as phospholipid-based liposomes and stratum corneum lipid-based liposomes, respectively. A stripping procedure from stratum corneum to dermis by means of adhesive tape was carried out to evaluate the extent of accumulation in the superficial layers of the skin. The various liposomes were radiolabelled both in the bilayer structures with [3H]cholesterol, [14C]dipalmitoylphosphatidylcholine and [14C]palmitic acid, depending on vesicle type, and in the aqueous compartments with [14C]inulin. Inulin absorption and elimination was also evaluated. Stratum corneum lipid-based liposomes could permeate the stratum corneum to a greater extent than phospholipid-based liposomes. Stratum corneum lipid-based liposomes could deliver a greater amount of aqueous radiolabelled marker ([14C]inulin) to the deeper skin strata (epidermis and dermis), while avoiding systemic absorption and, hence, organ distribution and renal elimination of [14C]inulin. Another important parameter in determining the extent of absorption is the vesicle size: the greater the mean size of liposomes, the poorer the permeation through stratum corneum layers. When fluid liposomes made up of unsaturated lecithins were used, a percutaneous absorption was obtained instead of dermal delivery. Stratum corneum lipid-based unilamellar liposomes may be suitable devices for dermal delivery.

Enhanced therapeutic effect of cytidine-5'-diphosphate choline when associated with GM1 containing small liposomes as demonstrated in a rat ischemia model

PURPOSE

Cytidine-5'-diphosphate choline (CDPc) was encapsulated in long-circulating unilamellar vesicles (SUVs) to improve the drug's biological effectiveness.

METHODS

SUVs made up of diaplmitoylphosphatidylcholine/diaplmitoylphosphatidylserine /cholesterol (7:4:7 molar ratio) and 8 mol % of ganglioside GM1 were prepared by extrusion through polycarbonate filters (mean diameter 50 nm). The formulation effectiveness was evaluated by an in vivo model of cerebral ischemia on Wistar rats.

RESULTS

The enhanced delivery of CDPc into the brain improved the therapeutic effectiveness of the drug. CDPc-loaded SUVs improved the survival rate of ischemized and reperfused Wistar rats (320-350 g) by approximately 66% compared with the free drug. Liposome formulation was also able to effectively protect the brain against peroxidative damage caused by post-ischemic reperfusion. SUVs lowered the conjugated diene levels of the cerebral cortex. The liposomal delivery system did not alter the distribution patterns in the various cerebral lipid fractions of the drug, radiolabeled with 14C-CDPc.

CONCLUSIONS

CDPc-loaded SUVs were able to protect the brain against damage induced by ischemia. A possible clinical application is envisaged.

Pefloxacine mesilate- and ofloxacin-loaded polyethylcyanoacrylate nanoparticles: characterization of the colloidal drug carrier formulation

The entrapment of fluoroquinolones, perfloxacine mesilate (PFX) and ofloxacin (OFX), in polyalkylcyanoacrylate (PECA) nanoparticles could offer some advantages for their biological application; for examples, increasing their bioavailability, controlling the drug time-release in blood, and reducing the formation of bacterial resistance. To load these two drugs in PECA polymeric bulk, the incorporation or adsorption method was performed. These two methods were capable of influencing nanoparticle size, molecular weight, release profile, and drug-polymer association. The incorporation method, particularly for the OFX system, achieved PECA nanoparticle suspensions with a mean size value three times higher than that obtained in the absence of the drug. In contrast, negligible changes were observed for PFX systems. This preparation process also influenced the nanoparticle storage stability. The molecular weight values of the various nanoparticle preparations were also influenced; that is, the PFX-loaded systems showed an enhancement in the average molecular weight values, whereas a reduction was observed for OFX-loaded systems. The adsorption method showed no particular difference in particle size, molecular weight, and storage stability compared with nanoparticles prepared without the drugs. The nanoparticle loading capacity was higher for the colloidal systems obtained following the incorporation preparation procedure. The release of drug from the nanoparticles was biphasic for both preparation processes. The fluoro-quinolone-loaded nanoparticles showed an enhancement of the antimicrobial activity against standard bacteria strains from 2- to 50-fold compared with the free drugs.

Intracellular accumulation of ofloxacin-loaded liposomes in human synovial fibroblasts

In order to incorporate ofloxacin within liposomes, the reverse-phase evaporation technique was carried out. The liposome lipid matrix consisted of dipalmitoylphosphatidylcholine-cholesterol-dihexadecylphosphate (4: 3:4 molar ratio). The liposome formulation presented a mean size of 185 +/- 31 nm and had an encapsulation capacity of 5.3 microliters/mumol. The liposome formulation was able to deliver ofloxacin into McCoy cells in a greater amount (2.6-fold) than the free drug, improving antibiotic accumulation.

Liposomes as in-vivo carriers for citicoline: effects on rat cerebral post-ischaemic reperfusion

Citicoline is a therapeutic agent widely used in the treatment of brain injury, for example in cerebrovascular disease or traumatic accidents. Unfortunately, the strong polar nature of this drug prevents it crossing the blood-brain barrier. In this paper, the possibility of efficiently trapping citicoline in liposomes to improve its therapeutic effects is reported. The citicoline-encapsulation efficiency, drug leakage and size analysis of various liposome systems were studied. The real therapeutic effectiveness of these citicoline liposome formulations was evaluated by biological assay. The effects of free and liposome encapsulated citicoline on survival rate of ischaemic reperfused male Wistar rats (80-100 g) were investigated. Of the phospholipid mixtures used in citicoline liposome formulation the best in terms of delivery and therapeutic effects was 1,2-dipalmitoyl-sn-glycero-phosphocholine: dipalmitoyl-DL-alpha-phosphatidyl-L-serine:cholesterol (7:4:7 molar ratio). This phospholipid mixture was also assayed for brain conjugated diene levels in rats, since this parameter is an index of lipid peroxidation in rat cerebral cortex during post-ischaemic reperfusion. A citicoline-loaded phospholipid mixture has produced an increase in rat survival rate of about 24% and a reduction in diene levels of 60%, compared to the free drug.

An interpretative analysis of the effect of the surfactants used for the preparation of polyalkylcyanoacrylate nanoparticles on the release process

The release of fluorescein from polyethylcyanoacrylate (PECA) or polyisobutylcyanoacrylate (PICA) nanoparticles was affected by the surfactants used for the preparation. The different surfactants also modified the molecular weight, size and loading of the nanoparticles. However, these factors were not be responsible for the different release. According to the release profiles and the Baker-Lonsdale model, a portion of fluorescein was concentrated near the nanoparticle surface. Thus, a non-homogeneous distribution of the fluorescent probe inside the nanoparticles was hypothesized. This distribution could reflect the fluorescein position inside the micella during the polymerization stage, or could be reached during the washing stage as the consequence of a different effect of the surfactants on the porosity of the nanoparticle structure.

Spectrofluorimetry at zero angle: determination of salicylic acid in an acetylsalicylic acid pharmaceutical formulation

In this work, a solid-state spectrofluorimetric method for drug assays was developed. In particular, we report the determination of salicylic acid (SA), as a hydrolysis product, in solid pharmaceutical formulations containing acetylsalicylic acid (ASA). Recently, we described a sensitive and accurate fluorescence method that provided, through a mathematical application, the simultaneous determination of ASA and SA. By means of the spectrofluorimetric method reported herein it was possible to carry out the SA determination, without any mathematical calculation and with a sensitivity 100 times that of our previous method. The intra- and inter-day reproducibility of the spectrofluorimetric method, expressed as the relative standard deviation, ranged from 0.1 to 0.3%. The present method requires a fluorescence apparatus with the excitation and detection systems in-line (zero angle). The detection system was not sensitive to the excitation wavelength, but was highly sensitive to emission wavelengths from 350 to 800 nm. The results obtained were compared with those of our previous spectrofluorimetric method, together with those of a high-performance liquid chromatography method and a US Pharmacopeia method. The sensitivity of the method was of the order of 10(-8) g.

Evaluation of polyalkylcyanoacrylate nanoparticles as a potential drug carrier: preparation, morphological characterization and loading capacity

Some physicochemical behaviours were investigated of polyethyl- (PECA) and polyisobutylcyanoacrylate (PICA), which, in recent years, have been proposed as nanoparticle colloidal systems for drug carrying. We observed the influence of preparation conditions, such as pH value and surfactant concentration, on parameters such as particle size and polymer molecular weight. Lower operating pH values (0-2) resulted in smaller nanoparticles than those prepared at pH 5.5. The polymer molecular weight was also a function of pH: low molecular weight at low pH and vice-versa. The surfactant concentration positively influenced main particle size and polymer molecular weight. These trends were independent of type of monomer; in fact, both ethyl- (ECA) and isobutyl-2-cyanoacrylate (ICA) showed the same behaviour. Loading capacity, as well as release profile, of the two polymers were evaluated using fluorescein as a model drug. Whereas both polymers showed almost the same release profile, there was a difference in the amount of encapsulated probe: higher aliquots for PICA than for PECA. Storage effects on such physicochemical parameters were also tested.

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.

[Primary effect of carotid body stimulation on left ventricular inotropism in swine]

The cardiovascular response to carotid body stimulation has been a interesting and simultaneously controversial subject. In fact, several authors described different responses depending on the animal species used (cat, dog, rabbit, monkey), time of stimulation (short-term v. long-term) and experimental conditions and procedures. According to our experience, the response to carotid body stimulation with cyanide, in normal breathing dogs, consists in hyperpnoea, bradycardia with arterial blood pressure fall (by means of longer diastolic periods), followed by a marked rise in arterial blood pressure and heart rate, after curarization. Concerning the inotropic response to carotid chemoreceptors stimulation, there exists some controversial and even antagonic opinions. In fact, some authors describe a positive inotropic effect, others a negative inotropic effect, and others still defend no inotropic response at all. In the present work, the authors try to contribute to the solution of this problem, studying a group of animals (pig) anaesthetised with chloralose, in which the major modulators of the inotropic response to carotid body stimulation (ventilation; heart rate; and ventricular load conditions) were controlled. To the evaluation of cardiac contractile state, indexes derived from the systolic isovolumic phase were used (maximum left ventricular pressure, dP/dtmax; dP/dtmin) in all the animals. In some animals, other indexes were also used (Vmax, Vpm, (dP/dt)/DP40, Tau and PB). The authors concluded that, in the present experimental conditions, the primary response to carotid body stimulation, in the pig, includes a positive inotropic effect.

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).