Formulation and stabilization of norfloxacin in liposomal preparations

Properties and cellular uptake of photo-triggered mixed metallosurfactant vesicles intended for controlled CO delivery in gas therapy

The scientific relevance of carbon monoxide has increased since it was discovered that it is a gasotransmitter involved in several biological processes. This fact stimulated research to find a secure and targeted delivery and lead to the synthesis of CO-releasing molecules. In this paper we present a vesicular CO delivery system triggered by light composed of a synthetized metallosurfactant (TCOL10) with two long carbon chains and a molybdenum-carbonyl complex. We studied the characteristics of mixed TCOL10/phosphatidylcholine metallosomes of different sizes. Vesicles from 80 to 800 nm in diameter are mainly unilamellar, do not disaggregate upon dilution, in the dark are physically and chemically stable at 4 °C for at least one month, and exhibit a lag phase of about 4 days before they show a spontaneous CO release at 37 °C. Internalization of metallosomes by cells was studied as function of the incubation time, and vesicle concentration and size. Results show that large vesicles are more efficiently internalized than the smaller ones in terms of the percentage of cells that show TCOL10 and the amount of drug that they take up. On balance, TCOL10 metallosomes constitute a promising and viable approach for efficient delivery of CO to biological systems.

Molecular recognition and photoprotection of riboflavin in water by a biomimetic host

A water-soluble tetralactam macrocycle with 2,6-diethoxynaphthalene groups as side walls is able to strongly bind riboflavin (K_a >10⁷ M^-1) in water through hydrogen bonding and the hydrophobic effect. The encapsulated riboflavin can be stabilized by the host against photo-degradation under UV-vis irradiation, which may be harnessed to extend the shelf life of riboflavin.

Mixed Pluronic-Cremophor Polymeric Micelles as Nanocarriers for Poorly Soluble Antibiotics-The Influence on the Antibacterial Activity

In this work, novel polymeric mixed micelles from Pluronic F127 and Cremophor EL were investigated as drug delivery systems for Norfloxacin as model antibiotic drug. The optimal molar ratio of surfactants was determined, in order to decrease critical micellar concentration (CMC) and prepare carriers with minimal surfactant concentrations. The particle size, zeta potential, and encapsulation efficiency were determined for both pure and mixed micelles with selected composition. In vitro release kinetics of Norfloxacin from micelles show that the composition of surfactant mixture generates tunable extended release. The mixed micelles exhibit good biocompatibility against normal fibroblasts MRC-5 cells, while some cytotoxicity was found in all micellar systems at high concentrations. The influence of the surfactant components in the carrier on the antibacterial properties of Norfloxacin was investigated. The drug loaded mixed micellar formulation exhibit good activity against clinical isolated strains, compared with the CLSI recommended standard strains (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922). P. aeruginosa 5399 clinical strain shows low sensitivity to Norfloxacin in all tested micelle systems. The results suggest that Cremophor EL-Pluronic F127 mixed micelles can be considered as novel controlled release delivery systems for hydrophobic antimicrobial drugs.

Hybrid Pectin-Liposome Formulation against Multi-Resistant Bacterial Strains

This work describes the development of a gastroresistant antimicrobial formulation composed of two carriers, pectin and liposomes, intended to improve the efficiency of norfloxacin (NOR) against multi-resistant bacterial strains. The formulations showed physicochemical stability for 180 days (4 °C) in terms of size, polydispersity, and zeta potential of the vesicles, prolonging the in vitro release of NOR for 11 h. The hybrid nanocarriers improved the in vitro antimicrobial activity against different multidrug-resistant bacterial strains, such as Salmonella sp., Pseudomonasaeruginosa, E. coli and Campylobacterjejuni, in comparison to commercial NOR and liposomal suspensions. The in vivo toxicity assay in chicken embryos revealed that the hybrid systems were not toxic in any of the different parameters analyzed, a result also corroborated by the analyses of biochemical biomarkers of the chicken-embryos liver function.

Development of Novel Silica-based Formulation of α-Lipoic Acid: Evaluation of Photo and Thermal Stability of the Encapsulated Drug

Powerful antioxidant α-lipoic acid (LA) is easily degraded under light and heating. This creates difficulties in its manufacture, storage and reduces efficiency and safety of the drug. The purpose of this work was to synthesize novel silica-based composites of LA and evaluate their ability to increase photo and thermal stability of the drug. It was assumed that the drug stabilization can be achieved due to LA-silica interactions. Therefore, the composites of LA with unmodified and organomodified silica matrixes were synthesized by sol-gel method at the synthesis pH below or above the pKa of the drug. The effects of silica matrix modification and the synthesis pH on the LA-silica interactions and kinetics of photo and thermal degradation of LA in the composites were studied. The nature of the interactions was revealed by FTIR spectroscopy. It was found that the rate of thermal degradation of the drug in the composites was significantly lower compared to free LA and mainly determined by the LA-silica interactions. However, photodegradation of LA in the composites under UV irradiation was either close to that for free drug or significantly more rapid. It was shown that kinetics of photodegradation was independent of the interactions and likely determined by physical properties of surface of the composite particles (porosity and reflectivity). The most promising composites for further development of novel silica-based formulations were identified.

A calix[4]arene-based ternary supramolecular nanoassembly with improved fluoroquinolone photostability and enhanced NO photorelease

Micellar-like nanoassemblies of a sulfonate amphiphilic calix[4]arene (1) are able to effectively co-entrap the fluoroquinolone antibacterial norfloxacin (2) and a hydrophobic nitric oxide (NO) photodonor (3), leading to a ternary supramolecular complex having a diameter of ca. 150 nm and a zeta potential of -48 mV. Outstanding photochemical stabilization of the otherwise photolabile fluoroquinolone 2 is observed under UVA excitation. Besides, visible light excitation leads to a remarkable enhancement of the NO photorelease efficiency of 3. Both the results can be explained on the basis of a "cage effect" of the micellar host that, in the case of 2, hinders the formation of the precursor complex responsible for the photodegradation, whereas in the case of 3 it provides a low polarity environment and easily abstractable hydrogens, which facilitate the radical-mediated mechanism involved in NO photorelease. Therefore, this supramolecular ternary nanoassembly simultaneously overcomes the main limitations of the free individual guests such as photolability and low photoreactivity. In view of the well-known antibacterial properties of the NO radical and the biocompatibility of the calixarene host, this nanoassembly represents a suitable bimodal system to be tested in antibacterial research.

Metal ion mediated photolysis reactions of riboflavin: A kinetic study

The effect of metal ion complexation on the photolysis of riboflavin (RF) using various metal ions (Ag⁺, Ni²⁺, Co²⁺, Fe²⁺, Ca²⁺, Cd²⁺, Cu²⁺, Mn²⁺, Pb²⁺, Mg²⁺, Zn²⁺, Fe³⁺) has been studied. Ultraviolet and visible spectral and fluorimetric evidence has been obtained to confirm the formation of metal-RF complexes. The kinetics of photolysis of RF in metal-RF complexes at pH7.0 has been evaluated. The apparent first-order rate constant (k_obs) for the photolysis of RF and the formation of lumichrome (LC) and lumiflavin (LF) (0.001M phosphate buffer) and LC, LF and cyclodehydroriboflavin (CDRF) (0.2-0.4M phosphate buffer) have been determined. The values of k_obs indicate that the rate of photolysis of RF is promoted by divalent and trivalent metal ions. The second-order rate constants (k' ) for the interaction of metal ions with RF are in the order: Zn²⁺>Mg²⁺>Pb²⁺>Mn²⁺>Cu²⁺>Cd²⁺>Fe²⁺>Ca²⁺>Fe³⁺>Co²⁺>Ni²⁺>Ag⁺. In phosphate buffer (0.2-0.4M), an increase in the metal ion concentration leads to a decrease in the formation of LC compared to that of CDRF by different pathways. The photoproducts of RF have been identified and RF and the photoproducts have simultaneously been assayed by a multicomponent spectrometric method. The mode of photolysis of RF in metal-RF complexes has been discussed.