Synthesis of Non-Toxic Silica Particles Stabilized by Molecular Complex Oleic-Acid/Sodium Oleate.

Catalin Spataru,Violeta Purcar,Bogdan Trica,Raluca Ianchis,Elvira Alexandrescu,Cristina Nistor,Raluca Somoghi,Florin Oancea,Dan Donescu,Sabina Nitu,Cristian Petcu

doi:10.3390/ijms17111936

Abstract

The present work is focused on the preparation of biocompatible silica particles from sodium silicate, stabilized by a vesicular system containing oleic acid (OLA) and its alkaline salt (OLANa). Silica nanoparticles were generated by the partial neutralization of oleic acid (OLA), with the sodium cation present in the aqueous solutions of sodium silicate. At the molar ratio OLA/Na+ = 2:1, the molar ratio (OLA/OLANa = 1:1) required to form vesicles, in which the carboxyl and carboxylate groups have equal concentrations, was achieved. In order to obtain hydrophobically modified silica particles, octadecyltriethoxysilane (ODTES) was added in a sodium silicate sol–gel mixture at different molar ratios. The interactions between the octadecyl groups from the modified silica and the oleyl chains from the OLA/OLANa stabilizing system were investigated via simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) (TG-DSC) analyses.A significant decrease in vaporization enthalpy and an increase in amount of ODTES were observed. Additionally, that the hydrophobic interaction between OLA and ODTES has a strong impact on the hybrids’ final morphology and on their textural characteristics was revealed. The highest hydrodynamic average diameter and the most negative ζ potential were recorded for the hybrid in which the ODTES/sodium silicate molar ratio was 1:5. The obtained mesoporous silica particles, stabilized by the OLA/OLANa vesicular system, may find application as carriers for hydrophobic bioactive molecules.

Highlights

Recent concerns regarding Earth depollution have generated studies on aqueous dispersions of the vesicular systems consisting of fatty acids from plant renewable resources [1,2]
The present paper describes an original method of obtaining non-toxic mesoporous silica, based on sodium silicate and oleic acid
Due to the interactions between the octadecyl groups from the modified silica and the oleyl chains from the oleic acid (OLA)/OLANa stabilizing system, the reaction mixtures were converted to stable semi-opaque gels

Summary

Introduction

Recent concerns regarding Earth depollution have generated studies on aqueous dispersions of the vesicular systems consisting of fatty acids from plant renewable resources [1,2]. These vesicular systems (RCOO−HOOCR) are formed from the unionized fatty acid (RCOOH) and its corresponding alkaline salt (RCOO−) [1,2]. Due to their origin, these associated dispersed systems, in the form of bilayered vesicles, are biocompatible, biodegradable, and non-toxic and can be classified in the green chemistry field [3]. The dispersion’s pH [4,5,6,7,8], the 13C Nuclear Magnetic Resonance (NMR) signals [7], and the X-ray diffraction peaks [8] are modified due to vesicle formation

Methods

Results

Conclusion