Biodegradable and conductive chitosan-graphene quantum dot nanocomposite microneedles for delivery of both small and large molecular weight therapeutics

Biodegradable microneedles for electrically-stimulated and tracked transdermal drug delivery were created from a nanocomposite of biocompatible, biodegradable chitosan and photoluminescent, electrically conductive graphene quantum dots (GQDs). The morphology, photoluminescent properties, cell viability and cell fluorescent imaging capability of GQDs were evaluated, showing that the nanoparticles possess low cytotoxicity and fluoresce blue under UV light, allowing for potential tracking of the drug bound onto GQDs by in vivo fluorescent imaging. The structure, crystallinity, electrical, mechanical and biodegradation properties of chitosan–GQD nanocomposites were characterised. The results show the introduction of 0.25–2 wt% GQDs into chitosan considerably improves electrical conductivity, whilst maintaining similar mechanical properties and biodegradation rate at 1 wt% GQDs. The microneedle arrays prepared from the chitosan–1 wt% GQD nanocomposite are strong enough to withstand the force of insertion into the body. The nanocomposite microneedles containing drug-laden GQDs exhibit enhanced drug release behaviour for a small molecular weight model drug compared to pristine chitosan microneedles. They also enable the release of a large molecular weight model drug through iontophoresis, which is otherwise not possible under passive diffusion conditions. These novel multifunctional nanocomposites provide a universal platform for iontophoretic and tracked delivery of both small and large molecular weight therapeutics.