(6cn) Effect of Physical and Chemical Properties of Nanoparticles on Small Molecule Release from Liposomes

Drug nanocariers such as liposomes are often limited by slow and non-specific release. A novel strategy is to initiate drug release by an external agent such as near infra-red (NIR) pulsed laser light absorbed by encapsulated or tethered nanoparticles (NP). The absorbance of NIR light is desirable because it causes minimal thermal injury to normal tissues and light penetration of several centimeters. We can synthesize Hollow Gold Nanoparticles (HGN) and Sulfide Cupper Nanoparticles (CSN) to absorb NIR light over the range from 700-900 nm. NIR picosecond pulsed laser light absorbed by NP is rapidly converted into thermal energy; the photothermal heating of the NP results in large temperature gradients that leads to the formation of transient vapor nanobubbles in aqueous solution. The collapse of the nanobubbles induces the rupture of the liposome membrane and the subsequent drug release with minimal damage to the contents and/or surroundings. We find HGN show higher specific absorbance of the NIR light than CSN which leads to more efficiently delivery of liposome contents. We have systematically synthesized various sizes of monodsiperse HGN and CSN, and determined the relative efficacy of laser power and duration on the rate of contents release from 200 nm liposomes. A fluorescent dye was encapsulated within a liposome as a model agent to study dye release kinetics triggered by a picosecond pulsed NIR laser irradiation. Subsequently, an anticancer drug was encapsulated within the liposomes to deliver the drug to prostate cancer cell in vitro; near-complete cell killing was observed. The study leads to a better understanding of the capabilities of multi-functional nanomaterials for NIR laser-controlled drug release in order to facilitate the development of optimized more complex therapeutic systems.