Artículos de revistas
Deprotonation And Protonation Of Humic Acids As A Strategy For The Technological Development Of Ph-responsive Nanoparticles With Fungicidal Potential
Registro en:
New Biotechnology. Elsevier Science Bv, v. 33, p. 773 - 780, 2016.
1871-6784
1876-4347
WOS:000386782600003
10.1016/j.nbt.2016.07.003
Autor
Motta
F. L.; Melo
B. A. G.; Santana
M. H. A.
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Humic acids (HAs) are macromolecules of undefined compositions that vary with origin, the process by which they are obtained and functional groups present in their structure, such as quinones, phenols, and carboxylic acids. In addition to agriculture, there is an increased interest in HAs due to their important pharmacological effects. However, HAs are not readily soluble in water at physiological pH, which may limit their bioavailability. Although primary aggregation forms non-uniform pseudo-micelles, the presence of ionisable groups in the HA molecule makes pH an environmental stimulus for controlled aggregation and precipitation. The aim of this work was to induce HA deprotonation and protonation, without compromising their colloidal dispersion, by means of pH changes as a strategy to produce nanoparticles. Deprotonation and protonation were achieved by treating HAs with sodium hydroxide and acetic acid, respectively, at various concentrations. Non pH-treated HAs at the same concentrations were used as control. The evolution of the treatments was monitored by pH changes in bulk solutions as a function of time. At equilibrium, the conformation of the colloidal structures was characterised by the predominant mean diameter, polydispersity index and absorbance of the solutions. The zeta potential was also measured in protonation assays. Moreover, the fungicidal activity of the nanoparticles was evaluated on the mycelial growth of three fungal genera. The results showed the pH decrease or increment as a function of the balance between hydroxyl and carboxyl groups and of the diffusion rate inside the structures. Deprotonation followed by protonation produced nanosized (100-200 nm), electrostatically stable (-30 mV) and pH-responsive particles with a polydispersity index <0.5. The protonated nanoparticles significantly inhibited (P <= 0.05) the mycelial growth of Candida albicans in vitro, when compared with control, and the fungicidal activity was dose-dependent. No activity was observed for the deprotonated HAs nanoparticles. These results show that deprotonation followed by protonation is an easy and useful strategy for the controlled production of HA nanoparticles, which exhibit a tendency to elicit fungicidal effects, with potential to develop new classes of cosmetics and pharmaceuticals. (C) 2016 Elsevier B.V. All rights reserved. 33 6 773 780 Fapesp (Sao Paulo Research Foundation) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)