Thermoresponsive nanogels as smart materials for topical drug delivery
Thermo-responsive NIPAM nanogels presenting a Volume Phase Transition Temperature (VPTT) close to body temperature are able to release the loaded drug as a result of changes in the morphology. As a result of temperature increase, a coil-to-globe transition takes place causing volume diminution of the nanogels and a consequent release of the drug.
Cross-linked NIPAM nanogels are prepared by high dilution radical polymerization to give particles with sizes under 50 nm, suitable for skin penetration.
Changes in temperature above and below the critical temperature result in the polymer network undergoing a hydrophilic-to-hydrophobic phase transition, thus inducing, respectively, either its collapse and release of the drug or the formation of large aggregates that enhance endosomal escape. The critical temperature, situated normally around 32ºC, can be fine-tuned by combination with other monomers.
The aim is to contribute to the mechanistic understanding of the phase transition involved with these polymers, to achieve fine control of the structure–property relationship, which would result in novel ‘smart’ materials that are ideal for use in drug delivery. Different preparations will be assessed using small and large drug molecules, and the kinetic profile of release and the response to changes in the environment will be studied.
Figure 1: Scheme of cross-linked nanogels loading a drug
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