UKICRS Summer Studentship - Thermogelling emulsions for topical drug delivery

The proposed project will develop temperature-responsive branched copolymer surfactants (BCSs) to produce emulsions which dramatically increase in viscosity upon warming from room to body temperature. These “thermogelling” systems have several topical applications, for instance in vaginal drug delivery, where the material can flow through an applicator, then increase in viscosity upon entry to the vagina, improving retention of the dosage form whilst reducing messiness. The FACTS 001 trial studying HIV prophylaxis found that messiness and leakage of a vaginal gel containing tenofovir reduced patient compliance, which ultimately led to the failure of the trial (Mehendale et al., Int. Health, 2012, 4, 63-9). The commercially-available thermogelling excipient, pluronic F127, has significant drawbacks, such as rapid dissolution and weak gel strength, thus there is a need for novel materials with improved properties. MC has developed BCSs based on poly(N-isopropylacrylamide), which are able to form emulsions which increase in viscosity from 1 to 2000 Pa.s upon warming from 25 to 37°C at 5% concentration, exceeding the viscosity reached by 15% pluronic F127 tenfold. However, poly(N-isopropylacrylamide) is known to give toxic hydrolysis products.

The aim of this project is to develop BCSs based on poly(N-vinylcaprolactam), which has temperature-responsive behaviour, but improved biocompatibility – it is a component of the excipient Soluplus. Specifically, the researcher will synthesise a range of BCSs of varying composition, characterise their molecular weight and composition, and undertake a rigorous rheological evaluation of their ability to form temperature-responsive emulsions. These materials would offer exiting new platforms for mucosal drug delivery.