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The photodynamic activity of Neutral Red and the new monobrominated Neutral Red was studied in suspensions of Staphylococcus aureus. The effect of mannitol and sodium azide in the presence of 25 μm photosensitizer on lethal photosensitization were investigated. The results of the mechanistic evaluation of Neutral Red showed that both mannitol and sodium azide produced a completed protective effect after irradiation without significant differences between them. The evaluation of monobrominated Neutral Red also showed a protective effect of microorganisms with the addition of mannitol. Although sodium azide produced a protective effect of the photoinactivation, it was incomplete and less than that exhibited by mannitol. The results indicate that the starting reagent, Neutral Red, is a producer of radical species, acting through a type I mechanism, whereas the halogenated derivative of Neutral Red produced reactive oxygen species and a contribution of singlet molecular oxygen cannot be discarded in the photoinactivation of Staphylococcus aureus cells. These results, analyzed together with the previously evaluated properties of the dyes, allow us to explain the differences observed in the photoinactivation of Staphylococcus aureus mediated by both azine photosensitizers., (© 2019 Wiley-VHCA AG, Zurich, Switzerland.)

The development and characterization of a novel, gel-type material based on a dendronized polymer (DP) loaded with ciprofloxacin (CIP), and the evaluation of its possible use for controlled drug release, are presented in this work. DP showed biocompatible and non-toxic behaviors in cultured cells, both of which are considered optimal properties for the design of a final material for biomedical applications. These results were encouraging for the use of the polymer loaded with CIP (as a drug model), under gel form, in the development of a new controlled-release system to be evaluated for topical administration. First, DP-CIP ionic complexes were obtained by an acid-base reaction using the high density of carboxylic acid groups of the DP and the amine groups of the CIP. The complexes obtained in the solid state were broadly characterized using FTIR spectroscopy, XRP diffraction, DSC-TG analysis and optical microscopy techniques. Gels based on the DP-CIP complexes were easily prepared and presented excellent mechanical behaviors. In addition, optimal properties for application on mucosal membranes and skin were achieved due to their high biocompatibility and acute skin non-irritation. Slow and sustained release of CIP toward simulated physiological fluids was observed in the assays (in vitro), attributed to ion exchange phenomenon and to the drug reservoir effect. An in vitro bacterial growth inhibition assay showed significant CIP activity, corresponding to 38 and 58% of that exhibited by a CIP hydrochloride solution at similar CIP concentrations, against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. However, CIP delivery was appropriate, both in terms of magnitude and velocity to allow for a bactericidal effect. In conclusion, the final product showed promising behavior, which could be exploited for the treatment of topical and mucosal opportunistic infections in human or veterinary applications., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Hydrogels of carbomer (C) and azithromycin (AZI) were prepared by neutralizing with AZI 50% of the carboxylic groups of 0.25% C(974) and C(934) dispersions. The hydrogels exhibit pH close to 8 and are physically stable. Titration with NaCl revealed a high degree of counterion condensation C-AZI. The release of AZI in a Franz cell was almost negligible when the receptor compartment was filled with water but was increased about 20 times as water is replaced by NaCl solution. Two analytical methods were used to evaluate the effect of the counterionic condensation on the chemical stability of AZI, a microbial assay and an HPLC method. Degradation of AZI in buffered aqueous solution was used as reference. The stability of AZI was significantly improved in the hydrogels retaining more than 75% of the initial concentration along a period of 18-20 months evaluated and the self life (t(90)) of the drug was increased 27 and 20 times over the reference. The improvement of AZI stability could be attributed to the high degree of counterion condensation in which drug molecules remain associated to the macromolecular phase having a high negative electrokinetic potential and higher viscosity and lower kinetic energy than those in the fluid phase.