The Role of the pH in the Impregnation of Spherical Mesoporous Silica Particles with L-Arginine Aqueous Solutions.

Sara Saber Younes Mohamed,Barbara Onida,Silvia Ronchetti,Sonia Martinez,Luigi Manna,Mauro Banchero

doi:10.3390/ijms222413403

Sara Saber Younes Mohamed, Barbara Onida + Show 4 more

Open Access

https://doi.org/10.3390/ijms222413403

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Abstract

In the context of the development of carriers for amino acids delivery, Spherical Mesoporous Silica Particles (SMSP), characterized by particles size ranging from 0.15 µm to 0.80 µm and average pore diameter of 2.4 nm, were synthesised and loaded with L-arginine (ARG), a basic amino acid involved in several physiological processes. The loading was performed using water as a solvent through the wet impregnation method (with a final arginine content of 9.1% w/w). The material was characterized before and after impregnation by means of X-Ray Diffraction (XRD), nitrogen sorption analysis, Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared (FT-IR) spectroscopy. SMSP are shown to suffer degradation upon impregnation, which dramatically affects their porosity. To elucidate the role of the pH of the ARG impregnating solution (originally set at pH ≈ 11) on SMSP degradation, the loading was performed under different pH conditions (5 and 9) keeping constant the ARG concentration. The impregnation performed with acidic solution did not modify the carrier. All samples displayed ARG in amorphous form: zwitterionic species were present in SMSP impregnated at basic pH whereas positive protonated species in that impregnated at acidic pH.

Highlights

In the last decades, the adsorption of amino acids on the surface of several materials has gained great attention since it is considered of great importance for many applications, including food industry, biodegradable plastic manufacturing, agrochemical, pharmaceutical production, and solid-phase peptide synthesis [1,2,3,4]
In the context of the development of carriers for amino acids delivery, Spherical Mesoporous Silica Particles (SMSP), characterized by particles size ranging from 0.15 μm to 0.80 μm and average pore diameter of 2.4 nm, were synthesised and loaded with L-arginine (ARG), a basic amino acid involved in several physiological processes
The results showed a complete release of ARG in water from the sample within 10 min, so confirming the possibility to use the SMSP carrier for arginine delivery

Summary

Introduction

The adsorption of amino acids on the surface of several materials has gained great attention since it is considered of great importance for many applications, including food industry, biodegradable plastic manufacturing, agrochemical, pharmaceutical production, and solid-phase peptide synthesis [1,2,3,4]. ARG is the basic amino acid with the highest isoelectric point, which is equal to 10.76 [6]. Local application could enhance the treatment efficiency, but this is limited by low cutaneous penetration of arginine due to its hydrophilicity [10]. To overcome all these limitations, researchers suggested the use of nano-systems based on lipids [10], polymers [14], and inorganic materials for the delivery of ARG [13]

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