Coherent control of orbital wavefunctions in the quantum spin liquid Tb2Ti2O7Tb_{2}Ti_{2}O_{7}

Resonant driving of electronic transitions with coherent laser sources creates quantum coherent superpositions of the involved electronic states. Most time-resolved studies have focused on gases or isolated subsystems embedded in insulating solids, aiming for applications in quantum information. Here, we demonstrate coherent control of orbital wavefunctions in pyrochlore $Tb_{2}Ti_{2}O_{7}$, which forms an interacting spin liquid ground state. We show that resonant excitation with a strong THz pulse creates a coherent superposition of the lowest energy Tb 4f states before the magnetic interactions eventually dephase them. The coherence manifests itself as a macroscopic oscillating magnetic dipole, which is detected by ultrafast resonant x-ray diffraction. The induced quantum coherence demonstrates coherent control of orbital wave functions, a new tool for the ultrafast manipulation and investigation of quantum materials

Multiple TORC1-Associated Proteins Regulate Nitrogen Starvation-Dependent Cellular Differentiation in Saccharomyces cerevisiae

The budding yeast Saccharomyces cerevisiae undergoes differentiation into filamentous-like forms and invades the growth medium as a foraging response to nutrient and environmental stresses. These developmental responses are under the downstream control of effectors regulated by the cAMP/PKA and MAPK pathways. However, the upstream sensors and signals that induce filamentous growth through these signaling pathways are not fully understood. Herein, through a biochemical purification of the yeast TORC1 (Target of Rapamycin Complex 1), we identify several proteins implicated in yeast filamentous growth that directly associate with the TORC1 and investigate their roles in nitrogen starvation-dependent or independent differentiation in yeast.We isolated the endogenous TORC1 by purifying tagged, endogenous Kog1p, and identified associated proteins by mass spectrometry. We established invasive and pseudohyphal growth conditions in two S. cerevisiae genetic backgrounds (Σ1278b and CEN.PK). Using wild type and mutant strains from these genetic backgrounds, we investigated the roles of TORC1 and associated proteins in nitrogen starvation-dependent diploid pseudohyphal growth as well as nitrogen starvation-independent haploid invasive growth.We show that several proteins identified as associated with the TORC1 are important for nitrogen starvation-dependent diploid pseudohyphal growth. In contrast, invasive growth due to other nutritional stresses was generally not affected in mutant strains of these TORC1-associated proteins. Our studies suggest a role for TORC1 in yeast differentiation upon nitrogen starvation. Our studies also suggest the CEN.PK strain background of S. cerevisiae may be particularly useful for investigations of nitrogen starvation-induced diploid pseudohyphal growth

Investigation of helium plasma jet-treated serum and cell media on the viability of skin cells

This study compares the differences in the viability of skin cells after culturing in cell medium supplemented with helium (He) plasma jet-treated serum and Dulbecco's Modified Eagle Medium (DMEM). HaCaT and HDFa cells were used as surrogates for the two major cell types of skin, i.e., keratinocytes and fibroblasts, respectively. A reduction in cell viability was observed for cells cultured in cell media supplemented with He plasma jet-treated serum and DMEM; however, cells were more sensitive to the He plasma jet-treated serum. HaCaT cells were more sensitive to He plasma jet-treated serum compared to HDFa cells. The decrease in the viability of HaCaT cells was not directly attributed to excessive oxidative stress (i.e., from reactive oxygen species generated by the He plasma jet). A possible explanation for the decrease in cell viability is that the He plasma jet treatment results in modification of the serum or DMEM, which decreases the bioavailability and/or bioefficacy of their essential components. In response to nutrient-deficiency, the cells may undergo autophagy, which can lead to a different form of cell death compared to apoptosis and necrosis. It will be important in the future to elucidate what essential components in cell media/serum are modified by plasma jets or other plasma sources utilised in biology and medicine research, and how these modifications alter cellular response.Rishabh Bhatia, Xanthe Strudwick, Allison J. Cowin, Endre J. Szil

Collagen Functionalization of Polymeric Electrospun Scaffolds to Improve Integration into Full-Thickness Wounds.

BACKGROUND: Electrospun fibers are widely studied in regenerative medicine for their ability to mimic the extracellular matrix (ECM) and provide mechanical support. In vitro studies indicated that cell adhesion and migration is superior on smooth poly(L-lactic acid) (PLLA) electrospun scaffolds and porous scaffolds once biofunctionalized with collagen. METHODS: The in vivo performance of PLLA scaffolds with modified topology and collagen biofunctionalization in full-thickness mouse wounds was assessed by cellular infiltration, wound closure and re-epithelialization and ECM deposition. RESULTS: Early indications suggested unmodified, smooth PLLA scaffolds perform poorly, with limited cellular infiltration and matrix deposition around the scaffold, the largest wound area, a significantly larger panniculus gape, and lowest re-epithelialization; however, by day 14, no significant differences were observed. Collagen biofunctionalization may improve healing, as collagen-functionalized smooth scaffolds were smallest overall, and collagen-functionalized porous scaffolds were smaller than non-functionalized porous scaffolds; the highest re-epithelialization was observed in wounds treated with collagen-functionalized scaffolds. CONCLUSION: Our results suggest that limited incorporation of smooth PLLA scaffolds into the healing wound occurs, and that altering surface topology, particularly by utilizing collagen biofunctionalization, may improve healing. The differing performance of the unmodified scaffolds in the in vitro versus in vivo studies demonstrates the importance of preclinical testing.Aswathy Ravindran Girija, Xanthe Strudwick, Sivakumar Balasubramanian, Vivekanandan Palaninathan, Sakthikumar Dasappan Nair, and Allison J. Cowi

Collagen-functionalized electrospun smooth and porous polymeric scaffolds for the development of human skin-equivalent

Electrospun polymer fibers have garnered substantial importance in regenerative medicine owing to their intrinsic 3D topography, extracellular matrix microenvironment, biochemical flexibility, and mechanical support. In particular, a material's nano-topography can have a significant effect on cellular responses, including adhesion, proliferation, differentiation, and migration. In this study, poly(L-lactic acid) (PLLA), a biodegradable polymer with excellent biocompatibility was electrospun into fibers with either smooth or porous topologies. The scaffolds were further modified and biofunctionalized with 0.01% and 0.1% collagen to enhance bioactivity and improve cellular interactions. Human keratinocytes (HaCaTs) and fibroblasts (human foreskin fibroblasts-HFF) were cultured on the scaffolds using a modified co-culture technique, where keratinocytes were grown on the dorsal plane for 5 days, followed by flipping, seeding with fibroblasts on the ventral plane and culturing for a further 5 days. Following this, cellular adhesion of the skin cells on both the unmodified and collagen-modified scaffolds (smooth and porous) was performed using scanning electron microscopy (SEM) and immunofluorescence. Distinct outcomes were observed with the unmodified smooth scaffolds showing superior cell adhesion than the porous scaffolds. Modification of the porous and smooth scaffolds with 0.1% collagen enhanced the adhesion and migration of both keratinocytes and fibroblasts to these scaffolds. Further, the collagen-modified scaffolds (both porous and smooth) produced confluent and uniform epidermal sheets of keratinocytes on one plane with healthy fibroblasts populated within the scaffolds. Thus, presenting a vast potential to serve as a self-organized skin substitute this may be a promising biomaterial for development as a dressing for patients suffering from wounds.Aswathy Ravindran Girija, Vivekanandan Palaninathan, Xanthe Strudwick, Sivakumar Balasubramanian, Sakthikumar Dasappan Nair and Allison J. Cowi

In vivo delivery of functional Flightless I siRNA using layer-by-layer polymer surface modification

Gene silencing using small interfering RNA has been proposed as a therapy for cancer, viral infections and other diseases. This study aimed to investigate whether layer-by-layer polymer surface modification could deliver small interfering RNA to decrease fibrotic processes associated with medical device implantation. Anti-green fluorescent protein labelled small interfering RNA was applied to tissue culture plates and polyurethane using a layer-by-layer technique with small interfering RNA and poly-L-lysine. In vitro studies showed that the level of down-regulation of green fluorescent protein was directly related to the number of coatings applied. This layer-by-layer coating technique was then used to generate Rhodamine-Flii small interfering RNA-coated implants for in vivo studies of small interfering RNA delivery via subcutaneous implantation in mice. After two days, Rh-positive cells were observed on the implants' surface indicating cellular uptake of the Rhodamine-Flii small interfering RNA. Decreased Flii gene expression was observed in tissue surrounding the Rhodamine-Flii small interfering RNA coated implants for up to seven days post implantation, returning to baseline by day 21. Genes downstream from Flii, including TGF-β1 and TGF-β3, showed significantly altered expression confirming a functional effect of the Rhodamine-Flii small interfering RNA on gene expression. This research demonstrates proof-of-principle that small interfering RNA can be delivered via layer-by-layer coatings on biomaterials and thereby can alter the fibrotic process.Penny J Martens, Mai Ly, Damian H Adams, Kathryn R Penzkover, Xanthe Strudwick, Allison J Cowin, and Laura A Poole-Warre

Collagen loss and impaired wound healing is associated with c-Myb deficiency

Collagen type I serves as an abundant structural and signalling component of skin. It is also an established target gene of the transcription factor, c-Myb. When c-myb-/- embryos were examined it was observed that their skin was markedly thinner than normal. Importantly, immunohistochemical investigation showed complete absence of collagen type I. Although these homozygous knock-out embryos fail to develop beyond day 15, fibroblasts established from these embryos (mouse embryonic fibroblasts [MEFs]) show defective proliferative responses. Furthermore, in vitro scratch wound assays demonstrated that these c-myb-/- MEFs also exhibit slower closure than their wild-type counterparts. Embryonic lethality has meant that examination of the role of c-Myb in adult mouse skin has not been reported to date. However, in view of the abundance of collagen type I in normal skin, its role in skin integrity and the in vitro data showing proliferative and migration defects in c-myb-/- MEFs, we investigated the consequences of heterozygous c-myb loss in adult mice on the complex process of skin repair in response to injury. Our studies clearly demonstrate that heterozygous c-myb deficiency has a functional effect on wound repair, collagen type I levels and, in response to wounding, transforming growth factor-beta1 (an important collagen stimulating factor) induction expression is aberrantly high. Manipulation of c-Myb may therefore provide new therapeutic opportunities for improving wound repair while uncontrolled expression may underpin some fibrotic disorders.Z Kopecki, MM Luchetti, DH Adams, X Strudwick, T Mantamadiotis, A Stoppacciaro, A Gabrielli, RG Ramsay, AJ Cowi