Abstracts

Advanced nanomaterials for drug delivery systems are the main focus of numerous research groups and, its application on drug resistance problem is probably the biggest challenged faced by scientists in the field. Indeed, in 2018, WHO declared the antimicrobial resistance as ‘(…) one of the top 10 global public health threats facing humanity’, along with a similar problem in cancer treatment: the chemotherapeutic drug resistant cells. In both cases, photoinactivation systems and photodynamic therapy (PDT) can overcome the problem of drug resistance when compared to the traditional approaches. For PDT, which has been shown to be efficient against some Gram (-) and (+) bacteria, more robust and efficient molecules that can act as photosensitizers (PS) are still needed for the improvement of the technique. In this work, the second-generation PS derived from chlorophyll, photodithazine (PDZ), was submitted to a set of physiochemical variations (pH 2, 5, 7 and 10, and concentrations of 2.5, 6, 12, 16, 22, and 25 µg/mL) to promote new aggregation states with the aim of improving its antimicrobial activity. The aggregated states of PDZ were characterized by photoluminescence and photoluminescence excitation spectroscopies, showing different conformations at basic and at acidic pH, but not changing significantly with the increase in concentration. The acidic forms, which showed higher activity against both bacterial strains, were used to build composites with halloysite nanoclays, which showed a significant improvement in antimicrobial activity against S. aureus and decreased the growing rate of E. coli cells. The effect of the composites will be discussed in light of the photophysical behavior of PDZ and the near field effect.