Detection of Light Images by Simple Tissues as Visualized by Photosensitized Magnetic Resonance Imaging

In this study, we show how light can be absorbed by the body of a living rat due to an injected pigment circulating in the blood stream. This process is then physiologically translated in the tissue into a chemical signature that can be perceived as an image by magnetic resonance imaging (MRI). We previously reported that illumination of an injected photosynthetic bacteriochlorophyll-derived pigment leads to a generation of reactive oxygen species, upon oxygen consumption in the blood stream. Consequently, paramagnetic deoxyhemoglobin accumulating in the illuminated area induces changes in image contrast, detectable by a Blood Oxygen Level Dependent (BOLD)-MRI protocol, termed photosensitized (ps)MRI. Here, we show that laser beam pulses synchronously trigger BOLD-contrast transients in the tissue, allowing representation of the luminous spatiotemporal profile, as a contrast map, on the MR monitor. Regions with enhanced BOLD-contrast (7-61 fold) were deduced as illuminated, and were found to overlap with the anatomical location of the incident light. Thus, we conclude that luminous information can be captured and translated by typical oxygen exchange processes in the blood of ordinary tissues, and made visible by psMRI (Fig. 1). This process represents a new channel for communicating environmental light into the body in certain analogy to light absorption by visual pigments in the retina where image perception takes place in the central nervous system. Potential applications of this finding may include: non-invasive intra-operative light guidance and follow-up of photodynamic interventions, determination of light diffusion in opaque tissues for optical imaging and possible assistance to the blind

Light-induced reactive-oxygen-species-(ros-) mediated activation of self-assembled nanoplatforms for on-demand drug delivery

Significant research efforts have been devoted to the development of multifunctional nanoplatforms that can efficiently target and deliver therapeutic/diagnostic agents to diseased sites. In recent years, the use of internal or external stimuli to trigger drug release in a controlled or programmed fashion is emerging as a promising approach to the design and fabrication of smart drug carriers. Among various stimuli, light as an external source of energy has become a powerful tool for realizing precise drug delivery because it not only allows remote and accurate control of drug release but can also be easily focused into specific pathological areas such as tumor. Recently, the photosensitized cascade generation of reactive oxygen species (ROS) and cleavage of an ROS-sensitive linker have been utilized as a trigger to facilitate drug release at desired target sites. This book chapter highlights recent progress in the light-induced ROS-mediated activation of various self-assembled nanoassemblies for on-demand drug delivery. © 2019 American Chemical Society. All rights reserved.11Nscopu