Published October 18, 2018
UB CBE hosted the 2018 Graduate Research Symposium on October 12, 2018, with over 75 posters presented. Congratulations to the presenters for a successful event. The awards were divided into three research areas; biological research, material research, and computational research. Our winners are listed below:
Collagen type III (Col3) is one of the three major collagens in the body and loss of expression or mutations in the Col3 gene have been associated with the onset of vascular diseases such the Ehlers-Danlos syndrome. Previous work reported significant reduction of Col3 in tissues such as skin and vessels with aging. In agreement, we found that Col3 was significantly reduced in senescent human Mesenchymal Stem Cells (MSC) and myofibroblasts derived from patients with Hutchinson’s Guilford Progeria Syndrome (HGPS), a premature aging syndrome. Most notably, we discovered that ectopic expression of the embryonic transcription factor, NANOG restored Col3 expression in the cells and tissue constructs prepared with these cells. RNA-Seq analysis showed that genes associated with the activation of the TGF-b pathway were upregulated, while negative regulators of the pathway were downregulated upon NANOG expression. ChiP-Seq and immunoprecipitation experiments revealed that NANOG bound to the SMAD2 and SMAD3 promoters, in agreement with increased expression and phosphorylation levels of both proteins. Using chemical inhibition, shRNA knockdown and gain of function approaches, we established that both Smad2 and Smad3 were necessary to mediate the effects of NANOG but only Smad3 was also sufficient for Col3 production. In conclusion, NANOG restored production of Col3, which was impaired by cellular aging, suggesting novel strategies to restore the impaired ECM production and biomechanical function of aged tissues, with potential implications for regenerative medicine and anti-aging treatments.
A fundamental understanding of liver development is important for research areas in liver tissue regeneration, direct tissue replacement and alleviating chronic liver diseases. It is therefore critical to replicate human liver physiology with biological models that mimic its functions. We hypothesize that the structures and cues that initiate 3D liver formation can be mimicked with hepatic microtissues. Thus we aimed to engineer an in vitro organoid model of the liver diverticulum (LD), a key structure that: 1) arises in mouse development (E9.5) and human development (d26) and 2) forms the 3D liver. From inside the gut to outside, the LD is composed of a single layer of hepatic endoderm (HE), encased by a single layer of endothelial cells, and surrounded by the septum transversum mesenchyme (STM). 3D liver formation starts when the hepatic endoderm (HE) delaminates, joins with the endothelial cells, and migrates into the STM. We first determined the appropriate LD dimensions with an online mouse database. To investigate this phenomenon further, we utilized an in-vitro model of the developing liver. Human pluripotent stem cells (hPSCs) were differentiated into definitive endoderm and hepatic endoderm respectively using STEM Diff Kit media (Stem Cell Technologies) under low oxygen for 4 days on a coated matrigel (MG) surface. The definitive endoderm cells (DE) showed high expression of FOXA2 and SOX-17. After definitive endoderm induction, the media was switched to a serum free media (SFD) that contained BMP4 and FGF for hepatic endoderm differentiation. After three days of differentiation cells changed morphology exhibiting a more cuboidal shape suggesting epithelial phenotype. Initially we investigated the formation of hepatic endoderm microtissues. Hepatic endoderm cells were harvested using accutase and seeded at 20,000 cells per well of a 384 well round bottom plate in the presence of SFD, 20% knockout serum (KOSR), 10 (ug/mL) fibroblast growth factor (FGF) and 20 (ug/mL) bone morphogenetic protein-4 (BMP4). The microtissues expressed significantly high levels of AFP and CDX2 consistent with early hepatic fated cells in-vivo. In a subsequent experiment hepatic endoderm cells were co-cultured in a 1:1 ratio with HUVEC endothelial cells to form compact spheroids that were embedded in MG containing 20,000 MSCs. These spheroids displayed finger- like projection into the ECM mirroring a transcriptional upregulation of SNAI2, an EMT marker present in the LD. Altogether these finding suggest the feasibility of utilizing stem cell derived hepatic progenitor cells to model the LD. Further work shall encompass improved characterization of hepatic microtissues regarding rate of formation, and analysis of morphological changes associated with growth in the presence of MSCs. Thus elucidating the mechanisms that govern liver development remains of utmost importance.
Fouling is one of the major challenges for the use of membrane technology for water purification. One effective way to mitigate the fouling is to chemically modify membrane surface to reduce its favorable interactions with foulants, such as grafting with superhydrophilic zwitterions. However, zwitterionic materials are water-soluble, and it is challenging to graft or coat zwitterions for long-term underwater operation. In this work, we demonstrate facile covalent grafting of zwitterionic materials (functionalized by acrylate and thiol) on the surface of ultrafiltration (UF) membranes using dopamine. Specifically, dopamine is deposited with sulfobetaine methacrylate (SBMA) or a thiol-containing zwitterionic polymer (p(MPC160-co-DTMAEL42, or PMD). In the presence of oxygen, dopamine forms polydopamine (PDA) adhering onto the membrane surface and covalently grafts SBMA or PMD via Michael addition to form a robust thin superhydrophilic layer, as confirmed by contact angle measurement and X-ray photoelectron spectroscopy (XPS). Interestingly, the coating does not completely cover the pores (as evidenced by the SEM) and thus, the modified membranes still exhibit reasonably high water permeance. The antifouling properties of the membranes were determined using a crossflow system and bovine serum albumin (BSA) as a model foulant. The modified UF membrane with SBMA and dopamine demonstrates up to 30% higher water flux than the uncoated one when tested with 1 g/L BSA. Moreover, the membrane modified with PMD and dopamine exhibits less flux decline (38% reduction) than the unmodified membrane (53% reduction). The facile approach of membrane modification employing SBMA/dopamine is also adapted for post‑modification of a commercial nanofiltration (NF) membrane module, which demonstrates enhanced antifouling properties when tested with real wastewater at a wastewater treatment plant.
Zwitterionic materials are a family of materials that have moieties possessing both cationic and anionic groups which possess a very unique antifouling property of resisting specific protein adsorption. Because of that, they can be used to solve various application problems. For example, zwitterionic materials can be coated onto polysulfone (PSF) membranes to provide a good fouling resistance ability which is essential in waste water treatment process. In this project, we used molecular simulation as a versatile tool to study the antifouling mechanism in those membranes at molecular level. Three membranes were constructed: pure PSF, poly(ethylene glycol) (PEG)-PSF and zwitterionic Sulfobetaine methacrylate(SBMA)-PSF. We investigated the structure and dynamics of water near the surface of different membranes as well as the dynamics of hydrogen bonds formed in the systems. The results showed a superior hydrophilicity in the SBMA-PSF membrane, which is very likely the main cause for its antifouling property. It was concluded that SBMA tethers disrupted the structure of water molecules near them and hindered their transitional and rotational mobility. These effects are the result of SBMA’s ability to form more and stronger hydrogen bonds with water than other materials.
Sustainable synthesis of Ammonia (NH3) is gaining great attention not only for its application as an alternative renewable energy fuel but also to substitute production of ammonia through the conventional Haber Bosh process. The conventional Haber-Bosh uses fossil fuels in deriving hydrogen from steam reforming of natural gas, is energy intensive and also leads to significant CO2 emission. Alternatively, electrochemical synthesis of ammonia (ESA) using renewable energy through the nitrogen reduction reaction (NRR) in alkaline medium saves the use of hydrogen as a reactant as the aqueous electrolyte forms the source of proton. However, the standard reduction potential of nitrogen and protons in the elctrolyte fall in the same domain. Thus, hydrogen evolution reaction is so dominant at the applied potential that selectivity of nitrogen reduction is a major challenge in the budding field. Recently, we have reported a metal- organic framework-derived nitrogen-doped metal free nanoporous carbon electrocatalyst with a Faradaic efficiency (FE) of 10 % at -0.3 V vs RHE under ambient conditions for the NRR. It exhibits a remarkable production rate of NH 3 up to 3.4×10 -6 mol cm -2 h -1 using aqueous 0.1 M KOH electrolyte. The performance has been compared with other N doped carbon derived from commercial polyaniline and nitrogen free KJ black and N doped CNT. The stability of the nitrogen-doped electrocatalyst was demonstrated during an 18-hour continuous test with constant production rates. This work provides a new insight into the rational design and synthesis of nitrogen-doped and defect-rich carbon NRR catalysts for NH 3 synthesis at ambient conditions.
Graphene has become attractive because of its unique properties such as high specific surface area, good electrical conductivity, flexibility, and high mechanical strength. One of the most common methods of producing graphene is based on graphite oxidation to graphene oxide (GO) followed by thermal or chemical reduction of GO to reduced graphene oxide (rGO). In thermal reduction methods, a small amount of GO is typically placed in a high temperature inert or reducing environment for a specific time. In addition, to improve certain properties or to add new features, rGO can be decorated with other compounds which usually requires additional synthesis steps. Here, we demonstrate the continuous single-step synthesis of three-dimensional crumpled graphene (CG) nanostructures decorated with cobalt-nickel nanoparticles using the High Temperature Reducing Jet (HTRJ) process. In this process, combustion products of a fuel-rich hydrogen flame pass through a converging-diverging nozzle. An aqueous solution or dispersion of precursors injected at the throat section of the nozzle is atomized by the hot high-velocity gas stream. The resulting droplets evaporate in a reducing environment containing excess H2. After the reaction zone, products are cooled immediately and collected on a filter. The key advantage of the HTRJ system over common flame-based aerosol synthesis methods is the separation of flame and product formation zones, which allows synthesis of non-oxide nanomaterials that can be reduced by H2 in the presence of H2O. We have utilized the capabilities of this system to synthesize CG nanostructures using an aqueous dispersion of GO as the precursor. Moreover, by adding nickel and cobalt nitrate salts to the GO precursor solution, we decorated CG nanostructures with nickel-cobalt nanoparticles of less than 10 nm average diameter. The HTRJ process is a potentially scalable, continuous method of producing CG and CG-metal nanostructures. Finally, we grew carbon nanotubes on these metal decorated graphene balls using chemical vapor deposition. Decorating CG balls with carbon nanotubes might increase the active surface area, aggregation resistance and mass and ion transport. The nanostructures can potentially be used in electrocatalysts for fuel cells, electrodes in batteries and supercapacitors, conductive inks for printed electronics, wastewater treatment, and many other applications where a graphitized carbon-metal nanomaterial is needed.