A Route to Triggered Delivery via Photocontrol of Lipid Bilayer Properties Using Lanthanide Upconversion Nanoparticles

Soft matter shells for nanoparticles provide an alternative approach to the more traditional inorganic core–shell nanoconstructs. In the latter, functionality and biocompatibility often require the addition of a hydrophilic organic coating. Herein, a supported lipid bilayer serves as a soft matter shell that has the physicochemical properties that enable a dynamic system capable of providing biocompatibility, encapsulation, and release of small molecule active agents. Direct coupling of the conformal, supported lipid bilayer containing an azobenzene-derivatized lipid with an upconversion nanoparticle provides the means to photocontrol the bilayer properties, generating a multifunctional coating. The close contact of the bilayer with the nanoparticle surface eliminates problems associated with Brownian motion for the energy transfer; the mechanism of energy transfer was determined to be dominated by radiative reabsorption using time-resolved photoluminescence. Release of an encapsulated dye, as a hydrophobic drug model, was achieved with significantly lower proportions of azobenzene-derivatized lipid than has been reported for UV-triggered release from liposomes. This work highlights the potential of the described nanoconstruct for light controlled delivery applications, especially in a biological context and in vivo applications, for which NIR excitation is of paramount importance for low toxicity and deeper tissue penetration.