Vapor‐deposited silicone coatings are attractive candidates for providing insulation in neuroprosthetic devices owing to their excellent resistivity, adhesion, chemical inertness and flexibility. A biocompatibility assessment of these coatings is an essential part of the materials design process, but current techniques are limited to rudimentary cell viability assays or animal muscle implantation tests. This article describes how a recently developed in vitro model of glial scar formation can be utilized to assess the biocompatibility of vapor‐deposited silicone coatings on micron‐scale wires. A multi‐cellular monolayer comprising mixed glial cells was obtained by culturing primary rat midbrain cells on poly(D ‐lysine)‐coated well plates. Stainless steel microwires were coated with two novel insulating thin film silicone polymers, namely poly(trivinyltrimethylcyclotrisiloxane) (polyV3D3) and poly(trivinyltrimethylcyclotrisiloxane–hexavinyldisiloxane) (polyV3D3–HVDS) by initiated chemical vapor deposition (iCVD). The monolayer of midbrain cells was disrupted by placing segments of coated microwires into the culture followed by immunocytochemical analysis after 7 d of implantation. Microglial proximity to the microwires was observed to correlate with the amount of fibronectin adsorbed on the coating surface; polyV3D3–HVDS adsorbed the least amount of fibronectin compared to both stainless steel and polyV3D3. Consequently, the relative number of microglia within 100 µm of the microwires was least on polyV3D3–HVDS coatings compared to steel and polyV3D3. In addition, the astrocyte reactivity on polyV3D3–HVDS coatings was lower compared to stainless steel and polyV3D3. The polyV3D3–HVDS coating was therefore deemed to be most biocompatible, least reactive and most preferable insulating coating for neural prosthetic devices.
Publicly-funded hospitals are typically allocated an annual budget by the government based on the number of enrollees in the region. Given tight budget constraints, the capacity of resources is fairly fixed. Such hospitals strive to maximize the utilization of their resources through continuous improvement and optimization techniques. We address a surgical case scheduling problem experienced at a publicly-funded hospital and conceptualize this multi-period, multi-resource, priority-based case scheduling problem as an unequal-sized, multi-bin, multi-dimensional dual bin-packing problem. A mixed integer programming model and a heuristic based on the first fit decreasing algorithm are presented. Resource availability, case priorities, and variation in surgery times are key features included in our model. Our proposed approach led to substantial savings, 20% reduction in number of days and up to 20% increase in operating room utilization, when compared to real schedules obtained from the surgical department at a publicly-funded hospital. 相似文献
Recent evidence implicating leukocytes in angiogenesis raises the question of whether leukocytes and other cells circulating with the blood in microvascular networks can home to capillary sprouts intraluminally. This study describes an investigation of leukocyte trafficking in sprouting capillaries fabricated using soft lithography. The leukocytes passing with whole blood through existing capillaries were able to enter microfabricated capillary sprouts of variable length and sprouting angle due to the mechanical interaction with red blood cells (RBCs) at the sprouting bifurcation, in spite of the complete absence of blood flow through the blind-ended sprouts or any chemoattractants. The RBCs formed "comet tails" (the densely packed cellular trains forming behind leukocytes as they move through narrow capillaries) and effectively pushed leukocytes into the microfabricated sprouts while bypassing them at the sprouting bifurcation. Individual sprouts filled with several leukocytes, as wells as RBCs and platelets, were observed. The results of this study suggest that (i) blood cells are likely present in capillary sprouts throughout their development, (ii) leukocytes and other circulating cells may use this mechanism to home to capillary sprouts intraluminally for direct engraftment, and (iii) tissues may use this phenomenon as another mechanism for local recruitment of leukocytes from the blood stream. 相似文献
The deoxy-myoglobin (deoxy-Mb)/carbonmonoxy-myoglobin (Mb-CO) UV-vis assay is the principal method used for quantifying the rates of CO release from CO-releasing molecules (CO-RMs) that might possess therapeutic benefits. Some issues emerge when the Mb-CO assay is utilized for testing CO-RMs with novel structures, which are comprehensively discussed here for the first time. Two methods for processing raw UV-vis spectroscopic data generated from the assay are presented in this paper. 相似文献
In this article we performed an extensive density functional [BP86/6-311++G(3df,3pd) level] investigation of the hypersurface of the Mitsunobu reaction. Reaction of a phosphine with a dialkyl azodicarboxylate (first step in the Mitsunobu conversion) leads to either a five-membered oxadiazaphosphole ring (more stable) or a betaine. The subsequent formation of two stable intermediates, a dialkoxyphosphorane and an acyloxyalkoxyphosphorane, constitutes the second step in the mechanism. These intermediates are in equilibrium with each other (under exchange of alkoxy and acyloxy ligands), and both can undergo an acid-induced decomposition to yield the alkoxy- and/or acyloxyphosphonium salts. The alkoxyphosphonium salt generates the desired ester via a SN2 mechanism (inversion product). Alternatively, the phosphorus atom in a mixed acyloxyalkoxyphosphorane species can easily undergo Berry pseudorotation. A subsequent intramolecular substitution leads to the final ester via a retention mechanism. The hypersurface is much more complicated than previously assumed, and the Mitsunobu reaction is fundamentally capable of running under either inversion or retention. The possibility of selective stereocontrol is discussed. Side reactions include the formation of a degradation product and an anhydride. 相似文献
Degenerate hydrogen atom exchange reactions have been studied using calculations, based on density functional theory (DFT), for (i) benzyl radical plus toluene, (ii) phenoxyl radical plus phenol, and (iii) methoxyl radical plus methanol. The first and third reactions occur via hydrogen atom transfer (HAT) mechanisms. The transition structure (TS) for benzyl/toluene hydrogen exchange has C(2)(h)() symmetry and corresponds to the approach of the 2p-pi orbital on the benzylic carbon of the radical to a benzylic hydrogen of toluene. In this TS, and in the similar C(2) TS for methoxyl/methanol hydrogen exchange, the SOMO has significant density in atomic orbitals that lie along the C-H vectors in the former reaction and nearly along the O-H vectors in the latter. In contrast, the SOMO at the phenoxyl/phenol TS is a pi symmetry orbital within each of the C(6)H(5)O units, involving 2p atomic orbitals on the oxygen atoms that are essentially orthogonal to the O.H.O vector. The transferring hydrogen in this reaction is a proton that is part of a typical hydrogen bond, involving a sigma lone pair on the oxygen of the phenoxyl radical and the O-H bond of phenol. Because the proton is transferred between oxygen sigma orbitals, and the electron is transferred between oxygen pi orbitals, this reaction should be described as a proton-coupled electron transfer (PCET). The PCET mechanism requires the formation of a hydrogen bond, and so is not available for benzyl/toluene exchange. The preference for phenoxyl/phenol to occur by PCET while methoxyl/methanol exchange occurs by HAT is traced to the greater pi donating ability of phenyl over methyl. This results in greater electron density on the oxygens in the PCET transition structure for phenoxyl/phenol, as compared to the PCET hilltop for methoxyl/methanol, and the greater electron density on the oxygens selectively stabilizes the phenoxyl/phenol TS by providing a larger binding energy of the transferring proton. 相似文献