Photoresponsive self-assembled nanomaterials for on-demand drug delivery

Abstract

On-demand drug delivery systems have the potential to optimise drug delivery by allowing drug administration as required. Lipid-based liquid crystalline matrices (LC) are increasingly explored as a means of controlled release drug delivery due to their biocompatibility and ability to incorporate and control the release drugs of a wide ranging size and polarity. The rate at which drug is released is ultimately determined by the mesophase nanostructure. This inbuilt ‘on-off’ switch for drug release affords the opportunity to manipulate drug delivery by influencing lipid packing by e.g. changing temperature. The utilisation of advanced synchrotron SAXS has allowed for the understanding of mechanisms by which transformations between lipid self-assembled structures take place. Understanding these interactions is essential in the development of self-assembled matrices for many bioapplications. Light-activated drug delivery systems have potential to provide a selective and non-invasive approach to accessing tissues that are not amenable to direct treatment. This thesis presents LC matrices which have been rendered light responsive by incorporation of additives that alter lipid packing upon irradiation and the effect of manipulating nanostructure on the release of drug from these matrices. Two approaches have been taken: 1. Photothermal Gold nanorods were incorporated into LC matrices and irradiation with near infrared laser light induced reversible thermotropic phase transitions via a photothermal effect. 2. Photochromic Photochromic compounds that undergo isomerisation in response to irradiation were incorporated into liquid crystalline systems where UV light induced a steric disturbance in the liquid crystalline nanostructure. The potential of these optically addressable nanostructures as reversible ‘on-demand’ drug delivery systems will translate into novel treatments for diseases such as macular degeneration.