Bioencapsulation of apomyoglobin in nanoporous organosilica sol–gel glasses: Influence of the siloxane network on the conformation and stability of a model protein

Abstract

Nanoporous sol-gel glasses were used as host materials for the encapsulation of apomyoglobin, a model protein employed to probe in a rational manner the important factors that influence the protein conformation and stability in silica-based materials. The transparent glasses were prepared from tetramethoxysilane (TMOS) and modified with a series of mono-, di- and tri-substituted alkoxysilanes, R(n)Si(OCH(3))(4-n) (R = methyl-, n = 1; 2; 3) of different molar content (5, 10, 15%) to obtain the decrease of the siloxane linkage (-Si-O-Si-). The conformation and thermal stability of apomyoglobin characterized by circular dichroism spectroscopy (CD) was related to the structure of the silica host matrix characterized by (29)Si MAS NMR and N(2) adsorption. We observed that the protein transits from an unfolded state in unmodified glass (TMOS) to a native-like helical state in the organically modified glasses, but also that the secondary structure of the protein was enhanced by the decrease of the siloxane network with the methyl modification (n = 0 < n = 1 < n = 2 < n = 3; 0 < 5 < 10 < 15 mol %). In 15% trimethyl-modified glass, the protein even reached a maximum molar helicity (-24,000 deg. cm(2) mol(-1)) comparable to the stable folded heme-bound holoprotein in solution. The protein conformation and stability induced by the change of its microlocal environment (surface hydration, crowding effects, microstructure of the host matrix) were discussed owing to this trend dependency. These results can have an important impact for the design of new efficient biomaterials (sensors or implanted devices) in which properly folded protein is necessary.

A new route to aerogels: Monolithic silica cryogels

“…One way to quantify the extent of Si\O\Si three-dimensional linkages in the structure of silica aerogels, cryogels or xerogels is the degree of condensation, defined [35] as: Table 4 shows the results for the 10 measured samples ordered by the degree of condensation, with values ranging from 86.2 to 94.2% (where 100% would correspond to pure silica). Values around 91-92% have been reported previously for silica aerogels and xerogels [36][37][38]. It is also instructive to express the degree of condensation in terms of the average number of silicon atoms linked to a given silicon atom through Si\O\Si bonds.…”

Activity enhancement and stabilization of lipase from Pseudomonas cepacia in polyallylamine-mediated biomimetic silica

“…Similar results were also observed at 4°C. Activity enhancement by various silane precursors Encapsulated protein may exhibit entirely different conformation owing to changes in the local microenvironment, thus giving rise to different biological activity and stability (Menaa et al 2009). We prepared encapsulated lipase by doping different levels of methyltrimethoxysilane (MTMS), dimethyldimethoxysilane (DMDMS), or trimethylmethoxysilane (TMMS) to the TMOS precursor; the cross-linking density was expected to be lower, but the hydrophobicity was expected to be greater accompanying an increase in the degree of substitution.…”

Provitamin D Doped Silica and Polymeric Films: New Materials for UV Biosensor

“…As an example, protein bioencapsulation has been carried out in nanoporous silica-based materials to study the biocompatibility and biological activity of proteins [5,6].…”