Comparative genomic analysis of Mycoplasma related to cell culture for infB gene-based loop-mediated isothermal amplification.

Mycoplasma contamination in cell culture affects the properties of cell lines. Gold standard detection by microbiological culture takes days and requires specialists. The polymerase chain reaction and loop-mediated isothermal amplification (LAMP) are fast molecular options, but LAMP only requires one heating block for DNA amplification. This study presents a comparative genomic analysis of Mycoplasma species to identify common target genes different from the rrsA gene, which encodes 16 S rRNA. The aim is to implement a LAMP assay to detect Mycoplasma species, reducing the time and specialized equipment required for detection. We performed a comparative genomic analysis through Mauve software and the GView server and selected infB and clpB genes as target candidates for designing LAMP primers. We evaluated both genes by multiple sequence alignment (MSA). The infB gene presented the best score MSA assessment with lower odd-log values (5,480,281) than other genes. We selected the infB gene to design LAMP primers specific to Mycoplasma spp. We used these primers to implement LAMP at 63 °C for 30 min, which showed 100% positive amplifications for detecting Mycoplasma spp. In conclusion, we present a methodology utilizing the infB gene-based LAMP assay to detect three of the six most prevalent Mycoplasma species in cell culture.

Effect of oils on the transmission properties of a terahertz photonic crystal.

The transmission properties of a photonic crystal immersed in several different oils have been characterized using terahertz time domain spectroscopy in the spectral range of 0.3-1.5 THz. As in previous works, oil samples can be distinguished using terahertz transmission measurements. When the same oils are introduced into a photonic crystal, we find that the effective refractive index of the photonic crystal is sensitive to the properties of the oils and shows differences not seen in bulk measurements. These effects are described in detail and have potential applications in both the sensing of very small volumes of oils and in the fine control of the refractive indices of photonic crystals.

Photolithographically-patterned C-MEMS graphene by carbon diffusion through nickel.

In recent years the most studied carbon allotrope has been graphene, due to the outstanding properties that this two-dimensional material exhibits; however, it turns out to be a difficult material to produce, pattern, and transfer to a device substrate without contamination. Carbon microelectromechanical systems are a versatile technology used to create nano/micro carbon devices by pyrolyzing a patterned photoresist, making them highly attractive for industrial applications. Furthermore, recent works have reported that pyrolytic carbon material can be graphitized by the diffusion of carbon atoms through a transition metal layer. In this work we take advantage of the latter two methods in order to produce multilayer graphene by improving the molecular ordering of photolithographically-defined pyrolytic carbon microstructures, through the diffusion (annealing) of carbon atoms through nickel, and also to eliminate any further transfer process to a device substrate. The allotropic nature of the final carbon microstructures was inspected by Raman spectroscopy (AverageID/IGof 0.2348 ± 0.0314) and TEM clearly shows well-aligned lattice planes of 3.34 Å fringe separation. These results were compared to measurements made on pyrolytic carbon (AverageID/IGof 0.9848 ± 0.0235) to confirm that our method is capable of producing a patterned multilayer graphene material directly on a silicon substrate.

Graphitizing Non-graphitizable Carbons by Stress-induced Routes.

Graphitic carbons' unique attributes have attracted worldwide interest towards their development and application. Carbon pyrolysis is a widespread method for synthesizing carbon materials. However, our understanding of the factors that cause differences in graphitization of various pyrolyzed carbon precursors is inadequate. We demonstrate how electro-mechanical aspects of the synthesis process influence molecular alignment in a polymer precursor to enhance its graphitization. Electrohydrodynamic forces are applied via electrospinning to unwind and orient the molecular chains of a non-graphitizing carbon precursor, polyacrylonitrile. Subsequently, exerting mechanical stresses further enhances the molecular alignment of the polymer chains during the formative crosslinking phase. The stabilized polymer precursor is then pyrolyzed at 1000 °C and characterized to evaluate its graphitization. The final carbon exhibits a uniformly graphitized structure, abundant in edge planes, which translates into its electrochemical kinetics. The results highlight the significance of physical synthesis conditions in defining the structure and properties of pyrolytic carbons.

Effect of velocity on microdroplet fluorescence quantified by laser-induced fluorescence.

Microdroplets generated inside microfluidic devices have been widely used as miniaturized chemical and biological reactors allowing important reductions in experimental fluid volumes and making it possible to carry out high-throughput assays. Laser-induced fluorescence (LIF) is commonly used to detect and quantify the product, marker or cell content inside each individual droplet. In this work, we employed this technique to characterize the response of in-flow microdroplets filled with fluorescein dye at different laser powers and flow velocities. Using two parallel laser beams closely focused inside a microchannel we determined the microdroplet velocities and showed that the droplet fluorescence intensity decreases exponentially with reducing velocities because of the effects of photobleaching. In contrast, the fluorescence intensity increases linearly with laser power in the 4-10 mW range. When LIF is used for microdroplet measurements it is important to consider not just the fluorophore concentration but also the droplet velocity and laser power in the development of quantitative assays.