Following in Situ the Degradation of Mesoporous Silica in Biorelevant Conditions: At Last, a Good Comprehension of the Structure Influence

Abstract

Mesoporous silica nanoparticles (MSNs) have seen a fast development as drug delivery carriers thanks to their tunable porosity and high loading capacity. The employ of MSNs in biomedical applications requires a good understanding of their degradation behavior both to control drug release and to assess possible toxicity issues on human health. In this work, we study mesoporous silica degradation in biologically relevant conditions through in situ ellipsometry on model mesoporous nanoparticle or continuous thin films, in buffer solution and in media containing proteins. In order to shed light on the structure/dissolution relationship, we performed dissolution experiments far from soluble silicate species saturation. Via a complete decorrelation of dissolution and diffusion contributions, we proved unambiguously that surface area of silica vectors is the main parameter influencing dissolution kinetics, while thermal treatment and open mesoporous network architecture have a minor impact. As a logical consequence of our dissolution model, we proved that the dissolution lag-time can be promoted by selective blocking of the mesopores that limits the access to the mesoporous internal surface. This study was broadened by studying the impact of the organosilanes in the silica structure, of the presence of residual structuring agents, and of the chemical composition of the dissolution medium. The presence of albumin at blood concentration was found affecting drastically the dissolution kinetics of the mesoporous structure, acting as a diffusion barrier. Globally, we could identify the main factors affecting mesoporous silica materials degradation and proved that we can tune their structure and composition for adjusting dissolution kinetics in order to achieve efficient drug delivery.

Functionalized Mesoporous Thin Films for Biotechnology

“…While titania thin films exhibit high chemical stability in biologically relevant conditions, silica thin films in aqueous environment are hydrolyzed and form silicilic acid or silicate species [ 19 ]. This progressive dissolution of the silica matrix promotes the release not only of the carried drug, but also of solubilized silica which might nucleate and accumulate randomly, posing a toxicity risk to the organism [ 81 , 92 ].…”

“…Despite the fact that silica substrates undergo biodegradation in in-vivo conditions due to the solubilization of silica matrix and the consequent formation of silicilic acid [ 19 , 101 ], studies have shown that they can be efficiently sterilized and still be used as bioactive coatings, having the advantage of being a source of ions necessary for cell differentiation if submerged in a solution containing inorganic ions similar to body fluid [ 17 ]. For instance, Chai and coworkers [ 88 ] used SiO 2 mesoporous thin films as support for osteoblast-like cell growth.…”

“…For the present review, we therefore decided to focus our attention on mesoporous silica and titania thin films. In fact, among mesoporous materials, SiO 2 is one of the most used, biocompatible substrates: its well-known and tested synthesis methods, and its predictable dissolution in a fluid with physiological compatible characteristics, [ 17 , 18 , 19 ] make it an attractive substrate in biomedicine. On the other hand, TiO 2 shows remarkable photocatalytic activity, making it a possible choice for sterilizing coatings [ 13 , 20 ].…”

Multifunctional superparamagnetic nanoparticles with a fluorescent silica shell for the in vitro study of bio-nano interactions at the subcellular scale

“…In some cases, the aminosilane will reduce the dissolution rate of the silica thanks to a combination of factors including the inductive donor effect of the alkyl chain reducing the electropositive character of Si centre, and an increase in hydrophobicity. 42,43 In other cases, the presence of aminosilane has been reported to increase the dissolution rate of the silica, possibly due to the presence of amine groups catalysing the hydrolysis as well as the decrease of the condensation of the silica network. 29,39 For these reason and because the fluo-rescence increase remains small (increase of 15% at best), we decided to use only an excess of 10 equivalent of APTMS per dye.…”

In Vivo Tracking of the Degradation of Mesoporous Silica through 89Zr Radio‐Labeled Core–Shell Nanoparticles

“…[ 44,45 ] In fact, one of the main parameters controlling the degradation kinetics of mesoporous silica is its surface area. [ 32,45,46 ] In addition, pH and temperature also greatly affect silica dissolution. [ 47,48 ] The different parameters involved in silica dissolution lead to a huge variety of possible scenarios and to inconsistent results for the kinetics of silica degradation in physiological buffers or biological media.…”