Bimodal Porous Silica Prepared by Pore-filling of Silica Sol

The enzyme chloroperoxidase (CPO) was immobilized in silica sol-gel beads prepared from tetramethoxysilane. The average pore diameter of the silica host structure (~3 nm) was smaller than the globular CPO diameter (~6 nm) and the enzyme remained entrapped after sol-gel maturation. The catalytic performance of the entrapped enzyme was assessed via the pyrogallol peroxidation reaction. Sol-gel beads loaded with 4 μg CPO per mL sol solution reached 9–12% relative activity compared to free CPO in solution. Enzyme kinetic analysis revealed a decrease inkcatbut no changes inKMorKI. Product release or enzyme damage might thus limit catalytic performance. Yet circular dichroism and visible absorption spectra of transparent CPO sol-gel sheets did not indicate enzyme damage. Activity decline due to methanol exposure was shown to be reversible in solution. To improve catalytic performance the sol-gel protocol was modified. The incorporation of 5, 20, or 40% methyltrimethoxysilane resulted in more brittle sol-gel beads but the catalytic performance increased to 14% relative to free CPO in solution. The use of more acidic casting buffers (pH 4.5 or 5.5 instead of 6.5) resulted in a more porous silica host reaching up to 18% relative activity.

Download Full-text

Porous Silica Sol-Gel Coatings for Nd: Glass High-Power Pulsed Laser Uses

The Physics and Technology of Amorphous SiO2 ◽

10.1007/978-1-4613-1031-0_68 ◽

1988 ◽

pp. 561-567 ◽

Cited By ~ 3

Author(s):

Hervé Floch ◽

Jean-Jacques Priotton ◽

Ian Malvil Thomas

Keyword(s):

High Power ◽

Sol Gel ◽

Porous Silica ◽

Pulsed Laser ◽

Silica Sol

Download Full-text

Positronium Decay in Silica Sol-Gels

MRS Proceedings ◽

10.1557/proc-180-325 ◽

1990 ◽

Vol 180 ◽

Cited By ~ 1

Author(s):

B. Hopkins ◽

C. A. Quarles ◽

T. W. Zerda

Keyword(s):

Distribution Function ◽

Porous Silica ◽

Surface Interactions ◽

Silica Sol ◽

Silica Gels ◽

Liquid Oxygen ◽

Rapid Decay ◽

Methoxy Groups ◽

Quenching Mechanisms ◽

Positronium Decay

ABSTRACTPositronium lifetimes inside porous silica are measured and discussed in terms of surface interactions, oxygen and nitrogen induced quenching and pore sizes. Surface interactions are studied for silica gels having surfaces covered solely with hydroxyl or methoxy groups. A rapid decay of positronium inside the pores filled with gaseous or liquid oxygen is reported and explained in terms of quenching mechanisms. An increase in the measured lifetimes for pores filled with nitrogen is attributed to the change in the pore distribution function.

Download Full-text

Gas sensing properties of nanocrystalline NiO and Co3O4 in porous silica sol–gel films

Sensors and Actuators B Chemical ◽

10.1016/j.snb.2004.11.073 ◽

2005 ◽

Vol 108 (1-2) ◽

pp. 184-192 ◽

Cited By ~ 90

Author(s):

C. Cantalini ◽

M. Post ◽

D. Buso ◽

M. Guglielmi ◽

A. Martucci

Keyword(s):

Gas Sensing ◽

Sol Gel ◽

Porous Silica ◽

Silica Sol ◽

Sensing Properties ◽

Gas Sensing Properties ◽

Sol Gel Films

Download Full-text

Environmental microscopy of capillary stress-induced strain behavior in ambient-pressure aerogels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166713 ◽

1996 ◽

Vol 54 ◽

pp. 850-851

Author(s):

Sudeep M. Rao ◽

Joshua Samuel ◽

Sai S. Prakash ◽

C. Jeffrey Brinker

Keyword(s):

Silica Aerogel ◽

Ambient Pressure ◽

Drying Shrinkage ◽

Pore Filling ◽

Silica Network ◽

Strain Behavior ◽

Partially Saturated ◽

Capillary Stress ◽

Wetting Liquid ◽

Aerogel Films

Ambient pressure silica aerogel thin films have recently been prepared by exploiting reversible drying shrinkage caused by derivatization of the internal gel surface. Aerogels have porosities of upto 99.9% and due to the small size of the pores (few nanometers), large capillary stresses are produced in gels that are partially saturated with a wetting liquid. As a result of these capillary stresses, the flexible silica network undergoes strain which has been observed using environmental microscopy. This technique allows variation of the equilibrium vapor pressure and temperature, and a simultaneous monitoring of the deformation of the unconstrained film thickness. We have observed >600% deformation during the pore-filling and pore-emptying cycles. In this presentation, we discuss the unique stress-strain behavior of these films.Ref.: Sai S. Prakash, C. Jeffrey Brinker, Alan J. Hurd & Sudeep M. Rao, "Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage", Nature. Vol. 374, 30 March, 1995, 439-443.

Download Full-text

A study of the mechanism of micropore fillingII. Pore filling of a microporous silica

Journal of Colloid and Interface Science ◽

10.1016/s0021-9797(84)80061-2 ◽

1984 ◽

Vol 98 (1) ◽

pp. 439-446 ◽

Cited By ~ 2

Author(s):

P PENDLETON ◽

A ZETTLEMOYER

Keyword(s):

Pore Filling ◽

Microporous Silica

Download Full-text

SiO2 Entrapment of Animal Cells for Hybrid Bioartificial Organs

MRS Proceedings ◽

10.1557/proc-628-cc10.1 ◽

2000 ◽

Vol 628 ◽

Cited By ~ 6

Author(s):

Giovanni Carturan ◽

Renzo Dal Monte ◽

Maurizio Muraca

Keyword(s):

Gas Phase ◽

Mechanical Stability ◽

Porous Silica ◽

Collagen Matrix ◽

Homogeneous Layer ◽

Animal Cells ◽

Bioartificial Organs ◽

Liver And Pancreas ◽

Encapsulation Method ◽

Metabolic Activities

ABSTRACTSi-alkoxides in gas phase are reactive towards the surface of animal cells, depositing a homogeneous layer of porous silica. This encapsulation method preserves cell viability and does not alter the hindrance of the biological load.In the prospective use for the design of a hybrid bioartificial liver, hepatocytes in a collagen matrix can be entrapped by the siliceous deposit which provides definite mechanical stability to the collagen matrix and molecular cutoff vs. high molecular weight proteins, including immunoglobulins. The functionality of the encapsulated cell load is maintained for the expressions of typical liver and pancreas metabolic activities.

Download Full-text