Search

Crown ethers have been shown to have physiological effects ascribed to their ionophoric properties. However, high levels of toxicity precluded interest in their evaluation as therapeutic agents. We prepared new silacrown analogs of crown ethers. These initial studies focused on examples of large ring silacrown ethers having at least fourteen ring atoms with at least one lipophilic or hydrophobic substituent on the ring and/or on the silicon atom. The synthesis of silacrown ethers, ionophoric behavior, toxicity studies, and preliminary pharmacodynamic studies in cardiac myocyte cell lines are presented and compared to their carbon analogs. We report the effects of these compounds in HL-1 cells, an atrial muscle cell line with plasma membrane and sarcoplasmic reticulum Ca 2+ channels that give rise to spontaneous Ca 2+ transients driven by action potentials. Dicyclohexano-18-crown-6 and the silacrown equivalent dimethylsila-17-cyclohexanocrown-6 were both found to rapidly inhibit the Ca 2+ transients after acute treatment, and these effects were reversed when extracellular KCl was increased to cause plasma membrane depolarization. The data suggest that the silacrowns can mimic the effects of crown ethers with similar ring sizes, and this appears to be due to their effects on membrane potential and suppression of action potential firing., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The corresponding author has filed for patents on his own behalf. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Contact lenses are one of the most successful biomaterials in history with a global market estimated to be worth over $17 billion in 2025. Silicone hydrogel contact lenses dominate the market and are complex biphasic biomaterials with several critical material properties needed for clinical use. Careful consideration of composition and chemistry is needed to identify formulations of lenses meeting all commercial standards with the potential for improved manufacturability, cost, and/or next generation use. Four silicone macromers were investigated in this work with varying symmetry of siloxane units and macromer structure, number of siloxane groups, branching, length, and concentration. Novel silicone hydrogel lenses were produced and evaluated for optical transmittance, elastic modulus, oxygen transmissibility, water content, and surface wettability. Several lenses met commercial standards and demonstrated an increase in oxygen permeability (Dk) and inverse relationship with elastic modulus and siloxane concentration, respectively. A hydrophobic/hydrophilic ratio below 1.4 was needed for a co-continuous water phase. Substitution of methoxypropyl groups for butyl groups increased hydrophobic microdomains leading to decreased optical quality and mechanical properties. Generally, fluorine-containing silicone macromers allowed for a wider range of successful compositions, and above a certain hydrophilic composition, the presence of trifluoropropyl groups resulted in improved solubility and optically clear lenses. Data also showed asymmetric siloxane macromers have potential to meet critical lens properties at lower overall siloxane content. New lens materials with wider composition ranges meeting all clinical lens properties is a significant challenge and may significantly expand the field., (© 2022 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Increasingly precise control of polymer architectures generated by "Living" Anionic Ring-Opening Polymerization (Living AROP) is leading to a broad range of commercial advanced material applications, particularly in the area of siloxane macromers. While academic reports on such materials remain sparse, a significant portion of the global population interacts with them on a daily basis-in applications including medical devices, microelectronics, food packaging, synthetic leather, release coatings, and pigment dispersions. The primary driver of this increased utilization of siloxane macromers is their ability to incorporate the properties of silicones into organic structures in a balanced manner. Compared to organic polymers, the differentiating properties of silicones-low T g , hydrophobicity, low surface energy, and high free molal space-logically lend themselves to applications in which low modulus, release, permeability to oxygen and moisture, and tactile interaction are desired. However, their mechanical, structural and processing properties have until recently precluded practical applications. This review presents applications of "Living" AROP derived polymers from the perspective of historical technology development. Applications in which products are produced on a commercial scale-defined as not only offered for sale, but sold on a recurrent basis-are emphasized. Hybrid polymers with intriguing nanoscale morphology and potential applications in photoresist, microcontact printing, biomimetic soft materials, and liquid crystals are also discussed. Previously unreported work by the authors is provided in the context of this review.

Thiasilacyclopentane (TSCP) and azasilacyclopentane (ASCP) heteroatom cyclics have proven capable of rapidly converting hydroxylated surfaces to functionalized surfaces in inorganic click reactions. In this work, we demonstrate that the use of these reagents can be extended to "simultaneous double-clicking" when both inorganic and organic substrates are present at the onset of the reaction. The simultaneous double-click depends on a first ring-opening click with an inorganic substrate that is complete in ∼1 s at 30 °C and results in the reveal of a cryptic mercaptan or secondary amine group, which can then participate in a second click with an organic substrate. TSCPs and ASCPs can take part in tandem double-click reactions in which the organic substrate is added to the reaction mixture after the initial inorganic click reaction is completed. Additionally, ASCPs with exocyclic functionality, specifically N -alkenyl-, N -aminoalkyl, and N -alkynyl-ASCPs, are shown to be options for tandem double-clicking in which functionalization proceeds in two independent steps and the sequence of the double-click reaction can be reversed.

A synthetic method is presented for the production of isotetrasilane, a higher order perhydridosilane, with the purity and volume necessary for use in extensive studies of the chemical vapor deposition (CVD) of epitaxial silicon (e-Si) thin films. The chemical characteristics, thermodynamic properties, and epitaxial film growth of isotetrasilane are compared with those of other perhydridosilanes. A film-growth mechanism distinct from linear perhydridosilanes H(SiH 2 ) n H, where n ≤ 4, is reported. Preliminary findings are summarized for CVD of both unstrained e-Si and strained e-Si doped with germanium (Ge) and carbon (C) employing isotetrasilane as the source precursor at temperatures of 500-550 °C. The results suggest that bis(trihydridosilyl)silylene is the likely deposition intermediate under processing conditions in which gas-phase depletion reactions are not observed.

Cyclic azasilanes have been synthesized for the purpose of developing coupling agents appropriate for a variety of nanotechnologies including surface modification of nanoparticles, nanocrystals, mesoporous materials and substrates. N-Methyl-aza-2,2,4-trimethylsilacyclopentane is representative of this class of compounds. Preliminary data for the treatment of inorganic surfaces, including nanoparticles and oxidized silicon wafers, with cyclic azasilanes suggest high-density monolayer deposition by a ring-opening reaction. Cyclic azasilanes contain a cryptic amine functionality that can perform a subsequent tandem coupling reaction with functional molecules after the surface-triggered ring-opening reaction, allowing for a one-pot self-assembly route on nanostructures. Tandem coupling reactions are demonstrated via addition reactions of the cryptic amine with epoxy and acrylate systems., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Heterocyclic silanes containing Si-N or Si-S bonds in the ring undergo a ring opening reaction with -OH groups at the surface of porous Si nanostructures to generate -SH or -NH functional surfaces, grafted via O-Si bonds. The reaction is substantially faster (0.5-2 h at 25 °C) and more efficient than hydrolytic condensation of trialkoxysilanes on similar hydroxy-terminated surfaces, and the reaction retains the open pore structure and photoluminescence of the quantum-confined silicon nanostructures. The chemistry is sufficiently mild to allow trapping of the test protein lysozyme, which retains its enzymatic activity upon release from the modified porous nanostructure.

Organic trihydridosilanes can be grafted to hydrogen-terminated porous Si nanostructures with no catalyst. The reaction proceeds efficiently at 80 °C, and it shows little sensitivity to air or water impurities. The modified surfaces are stable to corrosive aqueous solutions and common organic solvents. Octadecylsilane H3 Si(CH2 )17 CH3 , and functional silanes H3 Si(CH2 )11 Br, H3 Si(CH2 )9 CH=CH2 , and H3 Si(CH2 )2 (CF2 )5 CF3 are readily grafted. When performed on a mesoporous Si wafer, the perfluoro reagent yields a superhydrophobic surface (contact angle 151°). The bromo-derivative is converted to azide, amine, or alkyne functional surfaces via standard transformations, and the utility of the method is demonstrated by loading of the antibiotic ciprofloxaxin (35 % by mass). When intrinsically photoluminescent porous Si films or nanoparticles are used, photoluminescence is retained in the grafted products, indicating that the chemistry does not introduce substantial nonradiative surface traps., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Elastomeric polysiloxane nanocomposites with elongations of >5000% (more than 3× greater than any previously reported material) with excellent shape recovery are presented. Highly deformable materials are desirable for the fabrication of stretchable implants and microfluidic devices. No crosslinking or domain formation is observed by a variety of analytical techniques, suggesting that their elastomeric behavior is caused by polymer chain entanglements., (© Gelest, Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Dipodal silanes possess two silicon atoms that can covalently bond to a surface. They offer a distinct advantage over conventional silanes commonly used for surface modification in terms of maintaining the integrity of surface coatings, adhesive primers, and composites in aqueous environments. New nonfunctional and functional dipodal silanes with structures containing "pendant" rather than "bridged" organofunctionality are introduced. The stability of surfaces in aqueous environments prepared from dipodal silanes with hydrophobic alkyl functionality is compared to the stability of similar surfaces prepared from the conventional silanes. In strongly acidic and brine environments, surfaces modified with dipodal silanes demonstrate markedly improved resistance to hydrolysis compared to surfaces prepared from conventional silanes. Pendant dipodal silanes exhibit greater stability than bridged dipodal silanes. The apparent equilibrium constant for the formation of silanol species by the hydrolysis of a disiloxane bond was determined as Kc = [SiOH](2)/[Si-O-Si][H2O] = 6±1×10(-5) and is helpful in understanding the enhanced hydrolytic stability of surfaces modified with dipodal silanes., (© 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of Creative Commons Attribution NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.)

Silacrowns, ionophoric materials in which an ethylene bridge of a normal crown ether has been replaced by a R2Si group, facilitate ion transport across liquid membranes. A major aspect of their properties is their nontoxicity when compared to these crown ethers. This is probably due to their ready hydrolysis to the corresponding polyethylene glycols. The glycols also exhibit ion transport properties, even with an efficiency close to the silacrowns but the silacrowns stay intact long enough to partition into the hydrophobic phase of a liquid membrane whereas their hydrolysis products preferentially partition into the aqueous phases. Ready removal from the hydrophobic phase of a membrane will reduce the long term transporting effectiveness of the glycols. Thus, in vivo hydrolysis of the silacrowns will result in the loss of transmembrane carriers. Similar removal will not occur for normal crown ionophores which are both hydrolytically stable and partition into the hydrophobic phase, and remain there for long time periods.

Rat liver mitochondria are shown to adhere to the alkylsilylated glass beads in essentially a monolayer. The amount of mitochondria bound to the beads reaches a maximum where the length of the alkyl groups covalently linked to the beads exceeds eight carbons. Mitochondria immobilized on the beads and placed in a flow system exhibit normal: (a) respiratory control, (b) phosphate to oxygen ratio, (c) uncoupling by 2,4-dinitrophenol and carbonylcyanide p-trifluoromethoxyphenylhydrazone, and (d) inhibition by cyanide, azide, rotenone, oligomycin, and antimycin. Reversibility of the effects of 2,4-dinitrophenol, cyanide, and azide was rapid and complete. Inhibition by rotenone, oligomycin was essentially irreversible. Mitochondria have been maintained in a viable state on the beads at 27 degrees for periods up to 4 hours. The use of immobilized organelles appears to offer a new technique for the study of membrane-bound particles whereby substances can be rapidly added and removed while monitoring the composition of solution flowing over the particles.