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Sponge Enzyme's Role in Biomineralization and Human Applications
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Moin Merchant, Maushmi S. Kumar
Silicateins, which are only present in sponges, catalyze the production of silica from monomeric silicic acid esters in vivo. Recombinant silicatein converts alkoxy silanes to silicones (siloxanes) in a phase transfer reaction at neutral pH under physiological circumstances in vitro. Mass spectrometry, ultraviolet/visible light (UV/Vis), and nuclear magnetic resonance (NMR) methods revealed a significant increase in the production rate of oligomers and the chain length of silicones. The first enzymatically driven organometallic condensation step is the production of silicones in the presence of silicatein. The enzymatic activity of Silicatein was determined using UV/VIS measurements and 29Si DEPT NMR as an analytical probe, which demonstrated the hydrolytic activity of silicatein (Wolf et al., 2010). Silicatein has a remarkable ability to synthesize silica bio-catalytically under physiological conditions of neutral pH, ambient temperature, and pressure and can be used for the production of silicones. This bio-catalytical process could have an impact on the long-term production of silicones (Bains ànd Tacke, 2003).
Organo-Modified Siloxane Polymers for Conditioning Skin and Hair
Published in Randy Schueller, Perry Romanowski, Conditioning Agents for Hair and Skin, 2020
In general, organo-silicon nomenclature is applied to any structure containing at least one silicon atom. Silanes (R4Si) are silicon-containing compounds with one silicon atom and four directly bonded groups. Silicones, containing alternating silicon and oxygen atoms, are cyclic, linear, branched, caged, or three-dimensional polymers of the monomeric siloxy group. The prefix to these siloxane polymers designates the number of silicon atoms in the polymer—that is, disiloxane has two silicon atoms, while trisiloxane has three silicon atoms, etc. Siloxanes and silanes are named similarly; the root describes whether it is a siloxane (Si-O-Si backbone) or silane (only one Si atom), and the organofunctional portion describes the type and amount of substitution: hexamethyldisiloxane, decamethylpentacyclosiloxane, Tris(trimethylsiloxy)silane, and (poly)dimethylsiloxane.
Molecular Targets and Optical Probes
Published in George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos, Handbook of Small Animal Imaging, 2018
Eleni K. Efthimiadou, George Kordas
Surface coatings of IONPs not only provide colloidal suspendability and subsequent protection against the formation of aggregates either into a magnetic field or into the blood stream but also contribute to the binding of various ligands (fluorescent dyes for optical imaging, chelators for MRI/nuclear imaging, targeting moieties, or even drugs) to the NP surface (Titirici et al. 2006; Wang et al. 2007). The applied surface functionalization strategies include either inorganic or organic materials (Wu et al. 2008). In the case of inorganic coating, IONPs are modified at their outer shell by a layer such as silica, gold, gadolinium(III), or carbon. For instance, a surface enriched in silica enhances the presence of silanol groups, which can easily react with various coupling agents to covalently attach specific ligands to these magnetic particles. More specifically, the agents 3-aminopropyl-triethoxysilane (APTES), p-aminophenyl trimethoxysilane (APTS), and mercaptopropyltriethoxysilane (MPTES) are mainly employed for introducing the amino and sulfhydryl groups (Shen et al. 2004). The mechanism of silane coating is depicted in Figure 17.4.
Carbon Black Tinted Contact Lenses for Reduction of Photophobia in Cystinosis Patients
Published in Current Eye Research, 2019
The (4-carboxyphenyl)-surface modified carbon black, referred to as CB, suspension in water (14.87% solids, filtered to 0.5 µm particle size) was provided by Cabot Corporation. The CB in the suspension are aggregates of primary particles of 10–20 nm with a fractal morphology, a nominal aggregate size of ̴120 nm, and a nitrogen adsorption BET specific surface area of ~200 mm2/g.26 3-(METHACRYLOYLOXY)-PROPYLTRIS-(TRIMETHYLSILOXY)-SILANE, referred to as TRIS, was purchased from Silar. ACRYLOXY TERMINATED ETHYLENEOXIDE DIMETHYLSILOXANE-ETHYLENEOXIDE ABA BLOCK COPOLYMER (Product Code: DBE-U12) was purchased from Gelest. Ethylene glycol dimethylacrylate, referred to as EGDMA, and 1-Vinyl-2-pyrrolidinone, referred to as NVP, were purchased from Sigma-Aldrich. Darocur® TPO was purchased from Ciba. Cysteamine and timolol were purchased from Fisher Scientific. Phosphate buffered saline (PBS), 1x, without calcium and magnesium, was purchased from Mediatech, Inc. Cysteamine (98%) was purchased from Fischer Scientific. Ethanol (200 proof) and Vitamin E (DL-alpha tocopherol, >96%) were purchased from Sigma-Aldrich. Rabbit cadaver eyes were purchased from Pel-Freeze.
Formation of organosilica nanoparticles with dual functional groups and simultaneous payload entrapment
Published in Journal of Microencapsulation, 2018
Ya-Ling Su, Chien-Yu Lin, Shih-Jiuan Chiu, Teh-Min Hu
To further optimise and understand the particle-formation system, an additional experiment was performed to investigate whether EE% would be boosted if the total amount of the two silane precursors were increased, while keeping M/A constant. In this experiment, the M/A ratio was fixed at 5:1, because of the observed low EE% (for R6G) and the room for further increment (Figure 1(B), EE% (R6G) < 50% at M/A = 5). The results show that less turbid solutions were formed at higher silane concentrations, suggesting that particle formation was inhibited (Figure 1(C)). Besides, the EE% data for the three fluorescent compounds show either no change (DOX and FLU) or diminished in encapsulation (R6G) at higher silane feed concentrations (Figure 1(D)). The apparent inhibition of particle formation at high silane concentrations is consistent with our previous finding in the drug-free system (Chiu et al. 2014). In the two-silane system, the condensation reaction could occur between the same MPTMS molecules, the same APTMS molecules and between MPTMS and APTMS. The reaction products, therefore, are a mixture of various heterogeneous species. It is postulated that more water-soluble oligomeric species (perhaps containing more APTMS) was formed at high silane concentrations, thereby inhibiting the formation of particles upon solvent shifting (Chiu et al. 2014). Since R6G is a more hydrophobic molecule than DOX and FLU, its entrapment is sensitive to hydrophobicity/hydrophilicity of the species formed in the precipitation system (Figure 1(B,D)).
PDMS networks meet barnacles: a complex and often toxic relationship
Published in Biofouling, 2022
Daniel Rittschof, Beatriz Orihuela, Jan Genzer, Kirill Efimenko
Toluene (ACS grade), methanol (ACS grade), cis-dichlorobis(diethyl sulfide)platinum(II) (99.0%) (Pt catalyst), HPLC grade water, Nα-benzoyl-DL-arginine 4-nitroanilide hydrochloride (BAPNA) and trypsin were purchased from Sigma Aldrich (Burlington, MA, USA). The model cyclic siloxanes: hexamethylcyclosiloxane (D3), octamethylcyclosiloxane (D4), decamethylcyclosiloxane (D5), α,ω-vinyl-terminated poly(dimethylsiloxane) (v-PDMS) (with base molecular weights of 17.2, 28.0, 49.5 and 62.5 kDa) and tetrakis dimethyl (siloxy)silane (crosslinker) (TDSS) were supplied by Gelest Inc. (Morrisville, PA, USA). Silastic T2 silicone kit was provided by Dow Corporation (Plymouth, MI, USA). Aged filtered seawater (AFSW) was produced in-house.