SUMMARY
Airways are exposed to myriad environmental and damaging agents such as reactive oxygen species (ROS), which also have physiological roles as signaling molecules that regulate stem cell function. However, the functional significance of both steady and dynamically changing ROS levels in different stem cell populations, as well as downstream mechanisms that integrate ROS sensing into decisions regarding stem cell homeostasis, are unclear. Here, we show in mouse and human airway basal stem cells (ABSCs) that intracellular flux from low to moderate ROS levels is required for stem cell self-renewal and proliferation. Changing ROS levels activate Nrf2, which activates the Notch pathway to stimulate ABSC self-renewal as well an antioxidant program that scavenges intracellular ROS, returning overall ROS levels to a low state to maintain homeostatic balance. This redox-mediated regulation of lung stem cell function has significant implications for stem cell biology, repair of lung injuries, and diseases such as cancer.
Three-dimensional printer (3DP) (Z-Corp) is a solid freeform fabrication system capable of generating sub-millimeter physical features required for tissue engineering scaffolds. By using plaster composite materials, 3DP can fabricate a universal porogen which can be injected with a wide range of high melting temperature biomaterials. Here we report results toward the manufacture of either pure polycaprolactone (PCL) or homogeneous composites of 90/10 or 80/20 (w/w) PCL/beta-tricalcium phosphate (β-TCP) by injection molding into plaster composite porogens fabricated by 3DP. The resolution of printed plaster porogens and produced scaffolds was studied by scanning electron microscopy. Cytotoxicity test on scaffold extracts and biocompatibility test on the scaffolds as a matrix supporting murine osteoblast (7F2) and endothelial hybridoma (EAhy 926) cells growth for up to 4 days showed that the porogens removal process had only negligible effects on cell proliferation. The biodegradation tests of pure PCL and PCL/β-TCP composites were performed in DMEM with 10 % (v/v) FBS for up to 6 weeks. The PCL/β-TCP composites show faster degradation rate than that of pure PCL due to the addition of β-TCP, and the strength of 80/20 PCL/β-TCP composite is still suitable for human cancellous bone healing support after 6 weeks degradation. Combining precisely controlled porogen fabrication structure, good biocompatibility, and suitable mechanical properties after biodegradation, PCL/β-TCP scaffolds fabricated by 3DP porogen method provide essential capability for bone tissue engineering.
Combining compression and tensile test results, our study may guide the possible application of these biomaterials in bone tissue engineering and support further development of microstructure-based models of scaffold mechanical properties.
Normal human bone density is 1.85 (g/cm(3)), and this densitometer is useful for determination of material densities from 1.304 (g/cm(3)) to 1.882 (g/cm(3)). The device may be useful for precise bone density assessment.
This paper discusses a joint educational effort that incorporates sustainability in engineering and technology curricula at Drexel University (DU) and University of Texas at El Paso (UTEP). A critical component of a national “green industries/green jobs” effort is to motivate our citizenry to become proficient in STEM and associated manufacturing fields and societies, thus ensuring we have a 21st century workforce. Sustainable engineering is about design that recognizes the constraints applied by natural resources and the environmental system. The needs for engineering students and practicing engineers to understand sustainability concepts and concerns have been noted by many educators, scientists or engineers, and it is the philosophy of the authors that all engineering students need to become versed in sustainability ideas. This paper describes key factors in enhancing the ability of future engineering graduates to better contribute to a more sustainable future, preserving natural resources and advancing technological and societal development. Two approaches are used to incorporate sustainability into the undergraduate engineering and technology curricula that can be adopted or adapted by science and engineering faculty for this purpose. The two approaches described in the paper include: (1) redesigning existing courses through development of new materials that meet the objectives of the original courses and (2) developing upper division elective courses that address specific topics related to sustainability, such as green manufacturing, clean energy, and life-cycle assessment. The efforts presented in the paper also include an increase in social responsibility, development of innovative thinking skills, better understanding of sustainability issues, and increasing students’ interests in the engineering and technology programs. Projects, included in the senior courses or in the senior design project course sequence have been also part of them.
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