Functionalization of eumelanin nanoparticles with electro-responsive polymers

Eumelanin is a subtype of melanin pigment, it is a dark brownish heteropolymer spontaneously self-assembling in round shaped micelles of nanometric size. This pigment is biocompatible and can be interestingly exploited in the field of drug delivery, provided surface nanoparticle (NP) functionalization in order to improve hydrophilicity, hematocompatability and colloidal stability¹.

NPs surface functionalization is crucial to modulate its interaction with the cells and most common strategies uses ligands and/or polymeric layers to control it. These agents can improve the stability of the particles, enhancing the cellular uptake and simultaneously control the delivery of a certain drug to a specific target². Smart materials have the ability to modulate the release profile of a substance under specific internal or external stimuli. Among these materials, inherently conductive polymers (ICPs) present electrical, magnetic and optical properties. Polypyrrole (PPY) is the most common used ICP, due to its biocompability and conductivity properties. However, its drug-loading efficiency is limited and presents lack of cell affinity and adhesion. Polydopamine (PDA) affords many functional groups for reaction with biomolecules and proteins, displaying an excellent biocompatibility and low toxicity³. Hence, incorporating PDA into PPY is a great solution to improve the lack of cell affinity of PPY.  Thus, chemical polymerization of polypyrrole and polydopamine and functionalization of eumelanin NPs were performed with different ratios of PDA/PPY, in order to evaluate the influence of polymers concentrations in the final behavior of NPS. The physical-chemical behavior of eumelanin NPS coated with different ratios of PDA/PPY were characterized by: Scanning Electron Microscope, Atomic Force Microscopy, ZetaSizer and Fourier-transform infrared spectroscopy.   The final goal of this study will be to modify the surface of eumelanin NPs using these ICPs in order to use them for a controlled and local focused drug delivery in cancer treatment.