Encapsulation of Biologicals within Silicate, Siloxane, and Hybrid Sol−Gel Polymers:  An Efficient and Generic Approach

Abstract

The sol−gel encapsulation of labile biological materials with catalytic and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Herein, we describe a new class of precursors, based around polyol silicates and polyol siloxanes, especially those derived from glycerol, that addresses problems faced with traditional bioencapsulation protocols. Poly(glyceryl silicate) (PGS) was prepared and employed for sol−gel bioentrapment, in an approach distinguished by a high biocompatibility and mild encapsulation conditions, and which enables the reproducible and efficient confinement of proteins and cells inside silica. The methodology was extended to metallosilicate, alkylsiloxane, functionalized siloxane, and composite sol−gels, thereby allowing the fabrication of a physicochemically diverse range of bio-doped polymers. The hybrid materials display activities approaching those of the free biologicals, together with the high stabilities and robustness that characterize sol−gel bioceramics. Indeed, the bioencapsulates performed better than those fabricated from tetramethoxysilane, poly(methyl silicate) or alcohol-free poly(silicic acid), even when the latter were doped with glycerol. The activity enhancements appear to derive at least in part from the unusual microstructure of PGS sol−gels, in particular their high porosity, although the underlying mechanisms are unclear. Differences in precursor hydrolysis/condensation, development of gel structure, biological-matrix interactions, precursor toxicity, and pore collapse probably all contribute to the observed efficiency of the PGS materials. The performances of the encapsulates are compared with conventional sol−biogels and other immobilizates, in representative biocatalyst, biosensor, and biodiagnostic applications.

Comparação do desempenho da lipase de candida rugosa imobilizada em suporte híbrido de polissiloxano-polivinilálcool empregando diferentes metodologias

“…O processo sol-gel envolve diversas variáveis, como tempo e temperatura da reação, natureza do catalisador, concentração de reagentes, entre outros 10 . Estas variáveis determinam as caracterís-ticas finais dos materiais, incluindo a porcentagem de hidrólise e condensação de grupos reativos, densidade de reticulação e homogeneidade do produto.…”

“…Estas variáveis determinam as caracterís-ticas finais dos materiais, incluindo a porcentagem de hidrólise e condensação de grupos reativos, densidade de reticulação e homogeneidade do produto. Além disso, aditivos químicos podem ser usados para melhorar o processo e obter materiais com melhores propriedades, o que possibilita modificações nas propriedades mecânicas, controle de porosidade e ajuste no balanço hidrofílico/ hidrofóbico 9,10 .…”

“…Essa matriz combina os atributos físico-químicos de materiais inorgânicos e orgânicos, permitindo a manipulação da hidrofilicidade e hidrofobicidade, condutividade elétrica, carga iônica, porosidade e propriedades mecânicas em geral 10,14 , bem como elevada atividade e estabilidade.…”

High Frequency Acoustics in Colloid-Based Meso- and Nanostructures by Spontaneous Brillouin Light Scattering

“…[27] By solving the wave equation for elastic and isotropic media (Eq. 2.37), Lamb found the frequencies of the eigenmodes (n, l) to be (in a very general expression): 106) with x(n, l) being a constant for each individual mode, R(c l , c t ) being the rigidity, and d being the diameter of the sphere. The rigidity is a function of the longitudinal and transverse sound velocities and has the dimension of pressure, thus it is simply a modulus.…”

Porphyrinosilica and metalloporphyrinosilica: hybrid organic-inorganic materials prepared by sol-gel processing

“…The major advantages of encapsulated proteins are close control of the reaction medium and conditions, pre-vention of chemical degradation, cost-effective recycling of the protein, and enhanced biomolecular stability (Dave et al 1994, Gill & Ballesteros 1998, Hüsing et al 1999.…”