Nanocompósitos de κ-carragenana extraída de Hypnea musciformis para sensoriamento químico e avaliação da capacidade antitumoral

Abstract

Gold nanoparticles (AuNPs) are nanomaterials with unique properties, such as surface plasmon resonance (SPR), exhibiting a plasmonic absorption band between 520 and 540 nm when spherical, resulting in red emission in the visible spectrum. This property is widely used in biological applications, such as drug delivery, but it can also be employed in the chemical sensing of emerging contaminants, such as hexavalent chromium [Cr(VI)]. However, AuNPs produced with sodium borohydride (BH-AuNPs) exhibit low stability, which compromises the specificity of interaction with Cr(VI), in addition to being toxic. The overall objective of this work is to propose a green synthetic route for AuNPs using semi-refined κ-carrageenan extracted from Hypnea musciformis, a red macroalga abundant on the coast of Northeast Brazil, with the aim of also improving the stability of the nanomaterial.Two syntheses of AuNPs were performed: the first using a strong chemical reducing agent, which was carried out using chloroauric acid and sodium borohydride at room temperature; and the second using only κ-carrageenan in two steps under heating, maintaining the gold concentration at 250 μmol L-1. Furthermore, the characterization of these nanoparticles was performed using spectroscopic and structural techniques, also seeking to evaluate their interaction with the target ion. The morphology of both AuNPs was elucidated by atomic force microscopy (AFM), while size and charge were determined by dynamic light scattering (DLS) and zeta potential (ZP) techniques, respectively.. Kinetic tests showed that the interaction between BH-AuNPs and potassium dichromate (K2Cr2O7) is best observed after a reaction time of 20 minutes; however, this indicates more of a system collapse than a specific interaction. Furthermore, even after 90 minutes, there were no relevant changes in the plasmonic band of κ-AuNP when subjected to the same concentration of K2Cr2O7. Despite this, the κ-AuNPs showed potential cytotoxicity in human osteosarcoma cells (MG-63 cell line) from a concentration of 250 μg mL-1 after 48h, reducing cell viability in a statistically significant way.