Fluorescence and physical characterization of sol–gel-derived nanocomposite films suitable for the entrapment of biomolecules

Abstract

Thin films (100-500 nm thick) of Class I, Class II and Class I/II organic-inorganic hybrid silicates were prepared by casting mixtures of tetraethyl orthosilicate, methyltriethoxysilane and/or dimethyldimethoxysilane that were first hydrolyzed via sonication using acid catalysis, followed by induction of gelation using added buffer solutions containing no polymer or 3% w/v of poly(ethylene glycol). In some cases, the fluorescent probe 6-propionyl-2-dimethylaminonaphthalene (PRODAN) or the protein human serum albumin (HSA) were also added to the buffer solution, which permitted the fluorescence probing of the internal environment and biological activity within the various silicate films, respectively. Parameters such as the type and level of organosilane precursor, polymer level, casting speed, and aging time were varied to determine how such factors affected the thickness, morphology, and internal environment of the resulting films that were formed by this two-step process. The results show that composite films evolve in two stages: (1) rapid drying during the initial 1-2 h after casting of the film, followed by (2) a slower aging process that continues for many months. The aging of these thin films is different to that of bulk materials and the final state of the films can be quite different from that obtained for bulk materials. Preliminary studies of HSA-doped films show that the entrapped protein adopts a partially expanded conformation, but in most cases is still able to bind to ligands.

Synchrotron infrared microspectroscopy reveals localized heterogeneities in an organically modified silicate film

“…Since the rates of hydrolysis and condensation of the individual precursors are often different [7,8,10,11], the organic component may not be homogeneously distributed throughout the film. In fact, recent fluorescence studies suggest that phase separation of the organic and inorganic components occurs in these materials [12][13][14].…”

Common Causes of Glucose Oxidase Instability in In Vivo Biosensing: A Brief Review

“…64 Adding PEG improves resistance to cracking due to greater hydration of the films during aging, which lowers the hydration stress upon immersion in aqueous solutions. 65 The addition of PEG also reduces the surface area the gel without changing the pore size. 64 However, PEG may also compromise mobility and alter the conformation of enzymes entrapped in silica gel.…”

Biodoped Ceramics: Synthesis, Properties, and Applications

“…This method enabled high loading of enzyme within the ceramic matrix. Urease entrapped in this sandwich sol–gel film retained more than 95% activity for 6 weeks when it was stored at 4°C 33 . Ma et al 42 .…”

“…This practice reduces the risk of degradation of encapsulated proteins due to microbial attack 32 . Goring and Brennan 33 prepared sol–gel‐derived nanocomposite films suitable for protein encapsulation. These thin films were prepared using tetraethyl orthosilicate, methyltriethoxysilane and/or dimethyldimethoxysilane, and PEG.…”