A novel metal-protected plasma treatment for the robust bonding of polydimethylsiloxane

We describe a method for the irreversible bonding of PDMS-based microfluidic components by exploiting the first reported "shelfable" plasma treatment of PDMS. Simultaneous plasma activation and protection of PDMS surfaces are achieved via RF magnetron sputtering of thin aluminium films in the presence of an argon plasma. In this process, Ar plasma exposure generates a hydrophilic, silanol-enriched polymer surface amenable to irreversible bonding to glass, PDMS or silicon substrates, while the aluminium film functions as a capping layer to preserve the surface functionality over several weeks of storage in ambient conditions. Prior to bonding, this protective aluminium layer is removed by immersion in an aqueous etchant, exposing the adhesive surface. Employing this technology, PDMS-glass and PDMS-PDMS microfluidic devices were fabricated and the adhesive strength was quantified by tensile and leakage testing. Bonding success rates in excess of 80% were demonstrated for both PDMS-glass and PDMS-PDMS assemblies sealed 24 h and 7 days following initial polymer surface activation. PDMS-glass microdevices performed optimally, displaying maximum adhesive strengths on the order of 5 MPa and burst flow rates of approximately 1 mL min(-1) (channel dimensions: l = 25 mm; w = 300 microm; h = 20 microm). These data demonstrate a significant improvement in performance over previously reported bonding technologies, resulting in the production of more robust, longer-lasting microfluidic systems that can withstand higher pressures and flow rates.     

Paradoxical vocal fold motion: Presentation and treatment options

Paradoxical vocal fold motion is a rare disorder in which adduction of the folds occurs on inspiration. The disorder presents with signs of airway obstruction and often airway distress, so proper diagnosis by the otorhinolaryngologist is critical to subsequent management. We present a retrospective review of 10 patients with the diagnosis of paradoxical vocal fold motion seen over a 6-year period. Eight patients were females, and 6 required an acute airway intervention at presentation; 3 patients eventually underwent tracheotomy for respiratory decompensation. Six patients had a prior diagnosis of asthma, and this was determined to contribute to their respiratory status. Five patients were treated with botulinum toxin and 2 with flexible nasolaryngoscopic biofeedback, which improved the outcome. A review of the literature confirms a female predominance of patients presenting with paradoxical adduction and airway distress, often with a history of asthma and psychopathology. Our experience with botulinum toxin and biofeedback suggests that these procedures are viable treatment options in the management of patients with this disorder.     

A penalty method for numerically handling dispersive equations with incompatible initial and boundary data

This article is the numerical counterpart of a theoretical work in progress Qin and Teman, Applicable Anal (2011), 1–19, related to the approximation of evolution hyperbolic equations with incompatible data. The Korteweg‐de Vries and Schrödinger equations with incompatible initial and boundary data are considered here. For hyperbolic equations, the lack of regularity (compatibility) is known to produce large numerical errors which propagate throughout the spatial domain, destroying convergence. In this article, we numerically test the effectiveness of the penalty‐based method proposed in Qin and Teman, Applicable Anal (2011), 1–19, which replaces the hyperbolic equations with incompatible data by a system with compatible data. We observe that convergence is increased. As explained in the text, in the case of the Schrödinger equation, the impact of incompatible (nonregular) data is most severe, and the authors are not aware of any other method that can handle such severe incompatible data. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2011     

Catalytic reduction of NO to N2O by a designed heme copper center in myoglobin: implications for the role of metal ions

The effects of metal ions on the reduction of nitric oxide (NO) with a designed heme copper center in myoglobin (F43H/L29H sperm whale Mb, CuBMb) were investigated under reducing anaerobic conditions using UV-vis and EPR spectroscopic techniques as well as GC/MS. In the presence of Cu(I), catalytic reduction of NO to N2O by CuBMb was observed with turnover number of 2 mol NO.mol CuBMb-1.min-1, close to 3 mol NO.mol enzyme-1.min-1 reported for the ba3 oxidases from T. thermophilus. Formation of a His-heme-NO species was detected by UV-vis and EPR spectroscopy. In comparison to the EPR spectra of ferrous-CuBMb-NO in the absence of metal ions, the EPR spectra of ferrous-CuBMb-NO in the presence of Cu(I) showed less-resolved hyperfine splitting from the proximal histidine, probably due to weakening of the proximal His-heme bond. In the presence of Zn(II), formation of a five-coordinate ferrous-CuBMb-NO species, resulting from cleavage of the proximal heme Fe-His bond, was shown by UV-vis and EPR spectroscopic studies. The reduction of NO to N2O was not observed in the presence of Zn(II). Control experiments using wild-type myoglobin indicated no reduction of NO in the presence of either Cu(I) or Zn(II). These results suggest that both the identity and the oxidation state of the metal ion in the CuB center are important for NO reduction. A redox-active metal ion is required to deliver electrons, and a higher oxidation state is preferred to weaken the heme iron-proximal histidine toward a five-coordinate key intermediate in NO reduction.     

Alkynyl and poly-ynyl derivatives of carbon-tricobalt clusters

A series of alkynyl-tricobalt carbonyl clusters, Co₃(μ₃-C_nR)(μ-dppm)(CO)₇ [R = Bu^t, Ph, C₆H₄I, C₆H₄CCPh, SiMe₃, Fc, Au(PPh₃)] containing three, five or seven carbons in the chain, have been prepared by elimination of phosphine-gold(I) halides in reactions between Co₃(μ₃-CBr)(μ-dppm)(CO)₇ and Au(CCR)(PPh₃) or between Co₃{μ₃-CCCAu(PR₃)} (μ-dppm)(CO)₇ (R = Ph, tol) and ICCR′ (R′ = SiMe₃, Fc). The use of poly-substituted arenes or ferrocenes has enabled preparation of the complexes 1,4-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂C₆H₃X-5 (X = H, Br), 1,3,5-{(OC)₇(μ-dppm)Co₃(μ₃-CCC)}₃C₆H₃ and 1,1′-{(OC)₇(μ-dppm)Co₃ (μ₃-CCC)}₂Fc′ [Fc′ = Fe(η-C₅H₄-)₂]. The X-ray determined molecular structures of 12 of the complexes are reported.     

Mutations in mitochondrial-encoded cytochrome c oxidase subunits I, II, and III genes detected in Alzheimer's disease using single-strand conformation polymorphism

A "mitochondrial hypothesis" of late onset Alzheimer's disease (AD) has been proposed. Biochemical studies indicate that there is a significant decrease in cytochrome oxidase (CO) activity as well as perturbed CO I and CO III mRNA levels in platelets and brain tissue from Alzheimer's patients. Using the electrophoretic mutation detection technique SSCP and DNA sequencing, we have identified 20 point mutations in the mitochondrial-encoded CO subunits (CO I, II, and III) in AD and age-matched control brain samples. Eight of the mutations are new variants of the mitochondrial genome. The efficiency of SSCP in detecting mutations in the CO subunits was estimated to be 80% when compared to dideoxy sequencing. One of the mutations (at position 9,861) results in a phenylalanine-->leucine substitution at a highly conserved residue in CO III. CO activity was reduced by an average of 35% in all AD brains compared to age-matched control samples, which agrees with previous reports. CO activity in one of the AD brain samples carrying the 9,861 mutation decreased by 80% relative to control brain samples, suggesting that the phenotypic expression of this mutation may result in reduced CO activity and compromised mitochondrial function.     

A 3D mammalian cell separator biochip

The dissimilar cytoskeletal architecture in diverse cell types induces a difference in their deformability that presents a viable approach to separate cells in a non-invasive manner. We report on the design and fabrication of a robust and scalable device capable of separating a heterogeneous population of cells with variable degree of deformability into enriched populations with deformability above a certain threshold. The three dimensional device was fabricated in fused silica by femtosecond laser direct writing combined with selective chemical etching. The separator device was evaluated using promyelocytic HL60 cells. Using flow rates as large as 167 μL min(-1), throughputs of up to 2800 cells min(-1) were achieved at the device output. A fluorescence-activated cell sorting (FACS) viability analysis on the cells revealed 81% of the population maintain cellular integrity after passage through the device.