Laser Photolysis of Dye-Sensitized Nanocapsules Occurs via a Photothermal Pathway

Abstract

Light-addressable nanocapsules offer a powerful method for delivering spatiotemporally precise signals to cells. Thus far, the mechanism involved in the photolysis of nanocapsules has been opaque. This paper presents experimental evidence that rules out a photochemical pathway in favor of a photothermal mechanism in the far-red photolysis of dye-sensitized, lipid-vesicle based nanocapsules. Photolysis efficiency was unaffected by the presence of radical inhibitors, and mass spectrometry measurements confirmed that the photolytic process did not produce dye radicals. Measurements of dye quantum yield in the lipid membrane showed an inverse correlation between quantum yield of the dye and photolysis efficiency of the vesicle. The result is consistent with the notion that a decrease in quantum yield translates into more vibrational relaxation and thermal motion of the dye molecules in the membrane and thus more efficient photothermal disruption of the vesicle. Furthermore, we observed that the decrease in quantum yield and increase in photolysis efficiency was caused by the formation of raft-like domains that clustered the dye molecules into concentrated regions. Based on this information, we were able to design new nanocapsules using ternary mixtures of lipid and cholesterol that promoted the formation of raft domains and dye clustering. These nanocapsules showed improved photolysis efficiency over the best results we obtained previously.

Light-Activated Content Release from Liposomes

“…Both one-photon and two photon photolysis of liposomes have been shown, enabling the use of far red to near infrared laser wavelengths for release. In follow-up studies, mass spectrometry analysis and insensitivity of the process to radical inhibitors confirmed the photophysical nature of release 47. Subsequently, dye-sensitized lipid nanocapsules were used to deliver a cell-impermeable molecule, a ubiquitous second messenger inositol trisphosphate (IP 3 ), into cells following endocytosis.…”

Near‐Infrared‐Triggered Azobenzene‐Liposome/Upconversion Nanoparticle Hybrid Vesicles for Remotely Controlled Drug Delivery to Overcome Cancer Multidrug Resistance

“…There are varied strategies available based on either a one‐time burst or on–off repeat drug‐release event triggered by photosensitivity‐induced structural modifications of the liposome carriers. The release of encapsulated drugs from liposomes typically was stimulated by photolysis with ultraviolet (UV)/visible (vis) light . Despite their usefulness, the UV–vis irradiation, however, may cause photodamage to biological samples, and is quick attenuation in tissue because of severe absorption and scattering of photons, so as to be suitable only for in vitro studies.…”

Intracellular Delivery of Bioactive Molecules using Light-Addressable Nanocapsules

“…The advantages of uncaging bioactive molecules in the far red or near-IR via a photothermal pathway inside cells are significant. The cell is largely transparent to these long wavelengths and is not damaged by radicals, which can be an issue with chemically caged compounds 12. Because lipid nanocapsules physically isolate the bioactive molecules from the cell until they are released, the concentration of bioactive molecules can be controlled and preserved within the nanocapsule even after the nanocapsules have been delivered into the cell.…”