UC San Diego

Light is an ideal stimulus to externally control the properties of materials for many applications. Light is able to initiate chemical reactions largely independent of a material’s local environment making it particularly useful as a bio-orthogonal and on-demand trigger in living systems. The benefits of light as a trigger are diminished by various drawbacks of its use. Light of relatively short wavelengths, in the UV range, is most commonly used to initiate chemistries. This is because UV light has high energy, enough to affect bonds in molecules. But this high energy causes problems in off target effects. Many biological molecules are able to absorb and be modified detrimentally by UV light, limiting the use of UV light in biological systems. The problems of UV light for release in biological systems can be potentially overcome in various ways and this dissertation will describe two main strategies. In the first chapter the use of long wavelength responsive polymers will be described. These materials are intended for the encapsulation of a payload in a polymeric nanoparticle which can degrade and release in response to two-photon absorption of near-infrared light. This long wavelength light is absorbed by far fewer biological molecules and so can penetrate deeper through tissue than UV light while also causing less damage. Another method to mitigate the damaging effects of UV light is by using a material that requires less of a stimulus to release. These materials use UV light to trigger release but are designed to need minimal amounts of light. The polymers described with these properties, a poly(α-hydroxyl acid) in chapter 2 and a polyketal in chapter 3, are intriguing novel polymer backbones on their own and could be applied with appropriate triggering groups to respond to different stimuli.