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Appropriate localization of a drug and its structure/functional integrity in a delivery agent essentially dictates the efficacy of the vehicle and the medicinal activity of the drug. In the case of a phototherapeutic drug, its photoinduced dynamics becomes an added parameter. Here, we have explored the photoinduced dynamical events of a model phototherapeutic drug psoralen (PSO) in a potential delivery vehicle called an ethosome. Dynamic light scattering confirms the structural integrity of the ethosome vehicle after the encapsulation of PSO. Steady state and picosecond resolved polarization gated spectroscopy, including the well-known strategy of solvation and Förster resonance energy transfer, reveal the localization of the drug in the vehicle and the environment in the proximity of PSO. We have also investigated the efficacy of drug delivery to various individual bacteria (Gram-negative: Escherichia coli; Gram-positive: Staphylococcus aureus) and bacterial biofilms. Our optical and electron microscopic studies reveal a significant reduction in bacterial survival (∼70%) and the destruction of bacterial adherence following a change in the morphology of the biofilms after phototherapy. Our studies are expected to find relevance in the formulation of drug delivery agents in several skin diseases and biofilm formation in artificial implants.

Organic-inorganic nanohybrids are becoming popular for their potential biological applications, including diagnosis and treatment of cancerous cells. The motive of this study is to synthesise a nanohybrid for the diagnosis and therapy of colorectal cancer. Here we have developed a facile and cost-effective synthesis of folic acid (FA) templated Fe2O3 nanoparticles with excellent colloidal stability in water using a hydrothermal method for the theranostics applications. The attachment of FA to Fe2O3 was confirmed using various spectroscopic techniques including FTIR and picosecond resolved fluorescence studies. The nanohybrid (FA-Fe2O3) is a combination of two nontoxic ingredients FA and Fe2O3, showing remarkable photodynamic therapeutic (PDT) activity in human colorectal carcinoma cell lines (HCT 116) via generation of intracellular ROS. The light induced enhanced ROS activity of the nanohybrid causes significant nuclear DNA damage, as confirmed from the comet assay. Assessment of p53, Bax, Bcl2, cytochrome c (cyt c) protein expression and caspase 9/3 activity provides vivid evidence for cell death via an apoptotic pathway. In vitro magnetic resonance imaging (MRI) experiments in folate receptor (FR) overexpressed cancer cells (HCT 116) and FR deficient human embryonic kidney cells (HEK 293) reveal the target specificity of the nanohybrid towards cancer cells, and are thus pronounced MRI contrasting agents for the diagnosis of colorectal cancer.

Drug sensitization with various inorganic nanoparticles (NPs) has proved to be a promising and an emergent concept in the field of nanomedicine. Rose bengal (RB), a notable photosensitizer, triggers the formation of reactive oxygen species under green-light irradiation, and consequently, it induces cytotoxicity and cell death. In the present study, the effect of photoinduced dynamics of RB upon complexation with semiconductor zinc oxide NPs is explored. To accomplish this, we successfully synthesized nanohybrids of RB with ZnO NPs with a particle size of 24 nm and optically characterized them. The uniform size and integrity of the particles were confirmed by high-resolution transmission electron microscopy. UV/Vis absorption and steady-state fluorescence studies reveal the formation of the nanohybrids. ultrafast picosecond-resolved fluorescence studies of RB-ZnO nanohybrids demonstrate an efficient electron transfer from the photoexcited drug to the semiconductor NPs. Picosecond-resolved Forster resonance energy transfer from ZnO NPs to RB unravel the proximity of the drug to the semiconductor at the molecular level. The photoinduced ROS formation was monitored using a dichlorofluorescin oxidation assay, which is a conventional oxidative stress indicator. It is observed that the ROS generation under green light illumination is greater at low concentrations of RB-ZnO nanohybrids compared with free RB. Substantial photodynamic activity of the nanohybrids in bacterial and fungal cell lines validated the in vitro toxicity results. Furthermore, the cytotoxic effect of the nanohybrids in HeLa cells, which was monitored by MTT assay, is also noteworthy.