Estudo das interações do fármaco antineoplásico doxorrubicina com nanopartículas de ouro por técnicas espectroscópicas

Abstract

Raman spectroscopy combined with signal-enhancement techniques constitutes a set of powerful tools for the characterization of substrates intended for use as drug delivery systems in biological environments. Along with the possibility of developing more efficient delivery platforms, there also emerges the opportunity to minimize many of the adverse effects associated with drugs employed in the treatment of diseases such as cancer. Doxorubicin is a widely used antineoplastic and antibiotic agent in cancer therapies worldwide. However, the high costs of treatment — in terms of health and finances — are compounded by the drug’s systemic absorption, as it readily permeates throughout the human body, causing damage that may even lead to patient death. Thus, ensuring the efficiency of controlled drug delivery also entails reducing the impact on non-neoplastic tissues. This challenge requires the design of more effective delivery devices, such as those based on metallic nanostructures, making it crucial to understand the interaction between the drug and the nanostructured surface. In this study, gold nanostructures were synthesized via the chemical reduction method using borohydride, and the SERS efficiency of the resulting colloids were evaluated through absorption spectroscopy in the UV-VIS-NIR region, Raman and SERS spectroscopy at 632.8, 785, and 1064 nm excitation lines. To investigate the drug–nanostructure system, well-known surface modifiers such as potassium chloride, mercaptoethanol, and hydrochloric acid were employed. Spectroscopic analyses indicated that doxorubicin adsorbs in a plane perpendicular to the nanostructured surface in the presence of mercaptoethanol, which acts as a spacer and induces dipole–dipole interactions and hydrogen bonding. In contrast, adsorption occurs in a diagonal orientation relative to the surface plane when KCl and HCl are used, as these modifiers promote ion–ion and ion–dipole interactions. In parallel, computational structures were generated and optimized to characterize, by means of this powerful assignment tool, both cluster-model adsorption and the experimental spectroscopic data. These findings indicate that adsorption may occur under different regimes and provide evidence that the type of interaction force can be tuned, a key aspect for the design of controlled drug delivery devices.