Escherichia coli BarA-UvrY regulates the pks island and kills Staphylococci via the genotoxin colibactin during interspecies competition.

Wound infections are often polymicrobial in nature, biofilm associated and therefore tolerant to antibiotic therapy, and associated with delayed healing. Escherichia coli and Staphylococcus aureus are among the most frequently cultured pathogens from wound infections. However, little is known about the frequency or consequence of E. coli and S. aureus polymicrobial interactions during wound infections. Here we show that E. coli kills Staphylococci, including S. aureus, both in vitro and in a mouse excisional wound model via the genotoxin, colibactin. Colibactin biosynthesis is encoded by the pks locus, which we identified in nearly 30% of human E. coli wound infection isolates. While it is not clear how colibactin is released from E. coli or how it penetrates target cells, we found that the colibactin intermediate N-myristoyl-D-Asn (NMDA) disrupts the S. aureus membrane. We also show that the BarA-UvrY two component system (TCS) senses the environment created during E. coli and S. aureus mixed species interaction, leading to upregulation of pks island genes. Further, we show that BarA-UvrY acts via the carbon storage global regulatory (Csr) system to control pks expression. Together, our data demonstrate the role of colibactin in interspecies competition and show that it is regulated by BarA-UvrY TCS during interspecies competition.

Effects of Audio Brain Entrainment on Korean People with Mild Insomnia.

Sleep health has become an important healthy lifestyle. Research has shown that almost one-fifth of the Korean adult population does not have sufficient sleep. The lack of sleep is associated with significant medical, psychological, social, and economic issues. People are not only yearning for sufficient sleep but the quality of sleep as well. Usually, the obvious choice will be the use of pharmaceuticals however, these often have various side effects, and the lasting use of these medications could become a concern. Therefore, new non-drug alternatives are sought after. Audio brain entrainment is a procedure that modules neural activities by synchronizing brainwave frequency with pulse tones. By producing frequency tones for the deep sleep stage, it promotes a good night's sleep. In this paper, we developed a pillow integrated with the audio speakers that produce alpha and theta beats that should help improve sleep. Sleep polysomnography was performed on 10 people to compare the effects of the audio stimulus. Initial results showed a positive effect on sleep onset latency, indicating that sleep induction happened. This noninvasive stimulation technique can be a promising candidate for wearable bioelectronics medicine and further neuroscience research.

Development of a Microfluidic Droplet-Based Microbioreactor for Microbial Cultivation.

Droplet microfluidics creates new opportunities for microbial engineering. Most microbial cultivations are carried out in bioreactors, which are usually bulky and consume a large amount of reagents and media. In this paper, we propose a microfluidic droplet-based microbioreactor for microbial cultivation. A microfluidic device was designed and fabricated to produce many droplet-based microbioreactors integrated with an AC electric field for the manipulation of these microbioreactors. Droplets encapsulating fluorescent Escherichia coli cells were generated, sorted, and trapped individually in small chambers. Fluorescence intensity was monitored to determine cell growth. An electric field with varying voltages and frequencies manipulates the droplets, simulating an oscillation effect. Initial results showed that electric field does not affect cell growth. A comparison with shake flask showed that a similar standard growth curve is obtained when cultivating at room temperature. This device has the potential for making droplet-based microbioreactors an alternative for microbial engineering research.

Femtosecond-Laser-Based 3D Printing for Tissue Engineering and Cell Biology Applications.

Fabrication of 3D cell scaffolds has gained tremendous attention in recent years because of its applications in tissue engineering and cell biology applications. The success of tissue engineering or cell interactions mainly depends on the fabrication of well-defined microstructures, which ought to be biocompatible for cell proliferation. Femtosecond-laser-based 3D printing is one of the solution candidates that can be used to manufacture 3D tissue scaffolds through computer-aided design (CAD) which can be efficiently engineered to mimic the microenvironment of tissues. UV-based lithography has also been used for constructing the cellular scaffolds but the toxicity of UV light to the cells has prevented its application to the direct patterning of the cells in the scaffold. Although the mask-based lithography has provided a high resolution, it has only enabled 2D patterning not arbitrary 3D printing with design flexibility. Femtosecond-laser-based 3D printing is trending in the area of tissue engineering and cell biology applications due to the formation of well-defined micro- and submicrometer structures via visible and near-infrared (NIR) femtosecond laser pulses, followed by the fabrication of cell scaffold microstructures with a high precision. Laser direct writing and multiphoton polymerization are being used for fabricating the cell scaffolds, The implication of spatial light modulators in the interference lithography to generate the digital hologram will be the future prospective of mask-based lithography. Polyethylene glycol diacrylate (PEG-DA), ormocomp, pentaerythritol tetraacrylate (PETTA) have been fabricated through TPP to generate the cell scaffolds, whereas SU-8 was used to fabricate the microrobots for targeted drug delivery. Well-designed and precisely fabricated 3D cell scaffolds manufactured by femtosecond-laser-based 3D printing can be potentially used for studying cell migration, matrix invasion and nuclear stiffness to determine stage of cancer and will open broader horizons in the future in tissue engineering and biology applications.

3D Printed Polycaprolactone Carbon Nanotube Composite Scaffolds for Cardiac Tissue Engineering.

Fabrication of tissue engineering scaffolds with the use of novel 3D printing has gained lot of attention, however systematic investigation of biomaterials for 3D printing have not been widely explored. In this report, well-defined structures of polycaprolactone (PCL) and PCL- carbon nanotube (PCL-CNT) composite scaffolds have been designed and fabricated using a 3D printer. Conditions for 3D printing has been optimized while the effects of varying CNT percentages with PCL matrix on the thermal, mechanical and biological properties of the printed scaffolds are studied. Raman spectroscopy is used to characterise the functionalized CNTs and its interactions with PCL matrix. Mechanical properties of the composites are characterised using nanoindentation. Maximum peak load, elastic modulus and hardness increases with increasing CNT content. Differential scanning calorimetry (DSC) studies reveal the thermal and crystalline behaviour of PCL and its CNT composites. Biodegradation studies are performed in Pseudomonas Lipase enzymatic media, showing its specificity and effect on degradation rate. Cell imaging and viability studies of H9c2 cells from rat origin on the scaffolds are performed using fluorescence imaging and MTT assay, respectively. PCL and its CNT composites are able to show cell proliferation and have the potential to be used in cardiac tissue engineering.

3D printed microfluidics for biological applications.

The term "Lab-on-a-Chip," is synonymous with describing microfluidic devices with biomedical applications. Even though microfluidics have been developing rapidly over the past decade, the uptake rate in biological research has been slow. This could be due to the tedious process of fabricating a chip and the absence of a "killer application" that would outperform existing traditional methods. In recent years, three dimensional (3D) printing has been drawing much interest from the research community. It has the ability to make complex structures with high resolution. Moreover, the fast building time and ease of learning has simplified the fabrication process of microfluidic devices to a single step. This could possibly aid the field of microfluidics in finding its "killer application" that will lead to its acceptance by researchers, especially in the biomedical field. In this paper, a review is carried out of how 3D printing helps to improve the fabrication of microfluidic devices, the 3D printing technologies currently used for fabrication and the future of 3D printing in the field of microfluidics.