Chlorin e6-Conjugated Mesoporous Titania Nanorods as Potential Nanoplatform for Photo-Chemotherapy.

Photodynamic therapy (PDT) has developed as an efficient strategy for cancer treatment. PDT involves the production of reactive oxygen species (ROS) by light irradiation after activating a photosensitizer (PS) in the presence of O2. PS-coupled nanomaterials offer additional advantages, as they can merge the effects of PDT with conventional enabling-combined photo-chemotherapeutics effects. In this work, mesoporous titania nanorods were surface-immobilized with Chlorin e6 (Ce6) conjugated through 3-(aminopropyl)-trimethoxysilane as a coupling agent. The mesoporous nanorods act as nano vehicles for doxorubicin delivery, and the Ce6 provides a visible light-responsive production of ROS to induce PDT. The nanomaterials were characterized by XRD, DRS, FTIR, TGA, N2 adsorption-desorption isotherms at 77 K, and TEM. The obtained materials were tested for their singlet oxygen and hydroxyl radical generation capacity using fluorescence assays. In vitro cell viability experiments with HeLa cells showed that the prepared materials are not cytotoxic in the dark, and that they exhibit photodynamic activity when irradiated with LED light (150 W m-2). Drug-loading experiments with doxorubicin (DOX) as a model chemotherapeutic drug showed that the nanostructures efficiently encapsulated DOX. The DOX-nanomaterial formulations show chemo-cytotoxic effects on Hela cells. Combined photo-chemotoxicity experiments show enhanced effects on HeLa cell viability, indicating that the conjugated nanorods are promising for use in combined therapy driven by LED light irradiation.

Inactivation of carbapenem-resistant Klebsiella pneumoniae by photo-Fenton: Residual effect, gene evolution and modifications with citric acid and persulfate.

The photo-Fenton process application to eliminate carbapenem-resistant Klebsiella pneumoniae, an antibiotic-resistant priority pathogen, was evaluated. Initially, reagents concentration effect was tested and under suitable conditions (5 mg L-1 of Fe2+ and 50 mg L-1 of H2O2) complete bacteria inactivation by action of hydroxyl radical and UVA plus hydrogen peroxide was achieved at 120 min. The process presented a strong residual disinfecting effect when light was turned off at only 20 min. Besides, the cultivability of treated K. pneumoniae in a selective medium containing carbapenem antibiotics was considered. bla-KPC, gene responsible for the resistance, evolution was also assessed. The bacteria response to carbapenem antibiotics was higher as the treatment time increased. In turn, bla-KPC gene remained when K. pneumoniae was completely inactivated (120 min); nevertheless, treatment times longer than 120 min diminished bla-KPC presence. Finally, the photo-Fenton process and its modifications (citric acid addition or persulfate anion instead hydrogen peroxide) were applied to a real hospital wastewater in Colombia. In such complex matrix, the conventional photo-Fenton system reached a moderate disinfection (∼3.5 log-units at 300 min). Meanwhile, in presence of citric acid total inactivation was completed at the same time. Interestingly, the H2O2 substitution by persulfate strongly accelerated the microorganism elimination, achieving the 6-log-units reduction after only 60 min of process action. Thus, the effective elimination of K. pneumoniae from water by the modified photo-Fenton evidenced the potential applicability of this process to limit the proliferation of antibiotic resistant bacteria.