Michael V. Paukshto

The modulation of endothelial cell morphology, function, and survival using anisotropic nanofibrillar collagen scaffolds.

Endothelial cells (ECs) are aligned longitudinally under laminar flow, whereas they are polygonal and poorly aligned in regions of disturbed flow. The unaligned ECs in disturbed flow fields manifest altered function and reduced survival that promote lesion formation. We demonstrate that the alignment of the ECs may directly influence their biology, independent of fluid flow. We developed aligned nanofibrillar collagen scaffolds that mimic the structure of collagen bundles in blood vessels, and examined the effects of these materials on EC alignment, function, and inxa0vivo survival. ECs cultured on 30-nm diameter aligned fibrils re-organized their F-actin along the nanofibril direction, and were 50% less adhesive for monocytes than the ECs grown on randomly oriented fibrils. After EC transplantation into both subcutaneous tissue and the ischemic hindlimb, EC viability was enhanced when ECs were cultured and implanted on aligned nanofibrillar scaffolds, in contrast to non-patterned scaffolds. ECs derived from human induced pluripotent stem cells and cultured on aligned scaffolds also persisted for over 28 days, as assessed by bioluminescence imaging, when implanted in ischemic tissue. By contrast, ECs implanted on scaffolds without nanopatterning generated no detectable bioluminescent signal by day 4 in either normal or ischemic tissues. We demonstrate that 30-nm aligned nanofibrillar collagen scaffolds guide cellular organization, modulate endothelial inflammatory response, and enhance cell survival after implantation in normal and ischemic tissues.

Collagen fibril diameter and alignment promote the quiescent keratocyte phenotype

In this study, we investigated how matrix nanotopography affects corneal fibroblast phenotype and matrix synthesis. To this end, corneal fibroblasts isolated from bovine corneas were grown on collagen nanofiber scaffolds of different diameters and alignment--30 nm aligned fibrils (30A), 300 nm or larger aligned fibrils (300A), and 30 nm nonaligned fibrils (30NA) in comparison with collagen coated flat glass substrates (FC). Cell morphology was visualized using confocal microscopy. Quantitative PCR was used to measure expression levels of six target genes: the corneal crystallin-transketolase (TKT), the myofibroblast marker-α-smooth muscle actin (SMA), and four matrix proteins-collagen 1 (COL1), collagen 3 (COL3), fibronectin (FN), and biglycan. It was found that SMA expression was down-regulated and TKT expression was increased on all three collagen nanofiber substrates, compared with the FC control substrates. However, COL3 and biglycan expression was also significantly increased on 300A, compared with the FC substrates. Thus matrix nanotopography down-regulates the fibrotic phenotype, promotes formation of the quiescent keratocyte phenotype, and influences matrix synthesis. These results have significant implications for the engineering of corneal replacements and for promoting regenerative healing of the cornea after disease and/or injury.

Aligned-Braided Nanofibrillar Scaffold with Endothelial Cells Enhances Arteriogenesis

The objective of this study was to enhance the angiogenic capacity of endothelial cells (ECs) using nanoscale signaling cues from aligned nanofibrillar scaffolds in the setting of tissue ischemia. Thread-like nanofibrillar scaffolds with porous structure were fabricated from aligned-braided membranes generated under shear from liquid crystal collagen solution. Human ECs showed greater outgrowth from aligned scaffolds than from nonpatterned scaffolds. Integrin α1 was in part responsible for the enhanced cellular outgrowth on aligned nanofibrillar scaffolds, as the effect was abrogated by integrin α1 inhibition. To test the efficacy of EC-seeded aligned nanofibrillar scaffolds in improving neovascularization in vivo, the ischemic limbs of mice were treated with EC-seeded aligned nanofibrillar scaffold; EC-seeded nonpatterned scaffold; ECs in saline; aligned nanofibrillar scaffold alone; or no treatment. After 14 days, laser Doppler blood spectroscopy demonstrated significant improvement in blood perfusion recovery when treated with EC-seeded aligned nanofibrillar scaffolds, in comparison to ECs in saline or no treatment. In ischemic hindlimbs treated with scaffolds seeded with human ECs derived from induced pluripotent stem cells (iPSC-ECs), single-walled carbon nanotube (SWNT) fluorophores were systemically delivered to quantify microvascular density after 28 days. Near infrared-II (NIR-II, 1000-1700 nm) imaging of SWNT fluorophores demonstrated that iPSC-EC-seeded aligned scaffolds group showed significantly higher microvascular density than the saline or cells groups. These data suggest that treatment with EC-seeded aligned nanofibrillar scaffolds improved blood perfusion and arteriogenesis, when compared to treatment with cells alone or scaffold alone, and have important implications in the design of therapeutic cell delivery strategies.

Aligned nanofibrillar collagen scaffolds - Guiding lymphangiogenesis for treatment of acquired lymphedema.

Secondary lymphedema is a common disorder associated with acquired functional impairment of the lymphatic system. The goal of this study was to evaluate the therapeutic efficacy of aligned nanofibrillar collagen scaffolds (BioBridge) positioned across the area of lymphatic obstruction in guiding lymphatic regeneration. In a porcine model of acquired lymphedema, animals were treated with BioBridge scaffolds, alone or in conjunction with autologous lymph node transfer as a source of endogenous lymphatic growth factor. They were compared with a surgical control group and a second control group in which the implanted BioBridge was supplemented with exogenous vascular endothelial growth factor-C (VEGF-C). Three months after implantation, immunofluorescence staining of lymphatic vessels demonstrated a significant increase in lymphatic collectors within close proximity to the scaffolds. To quantify the functional impact of scaffold implantation, bioimpedance was used as an early indicator of extracellular fluid accumulation. In comparison to the levels prior to implantation, the bioimpedance ratio was significantly improved only in the experimental BioBridge recipients with or without lymph node transfer, suggesting restoration of functional lymphatic drainage. These results further correlated with quantifiable lymphatic collectors, as visualized by contrast-enhanced computed tomography. They demonstrate the therapeutic potential of BioBridge scaffolds in secondary lymphedema.

Invariance of single diode equation and its application

The electrical power available from a photovoltaic (PV) module can be simulated with the well-known and widely used [1–4] single diode equation. Five parameters must be known in the equation to determine the current-voltage relationship (I–V curve) for the module. These parameters can be obtained by fitting the experimental I–V curve at a fixed temperature and solar radiation for a small but representative sub-cell of the PV module. This is true because the single diode equation is invariant with respect to an arbitrary linear transformation in the I–V plane and there is a simple linear transformation between I–V curve of the module and I–V curve of its representative sub-cell. Of course, the five parameters are the functions of this transformation. Furthermore, the single diode equation for an array of the same PV modules can be represented as a linear transformation from the single module in I–V plane. The inverse problem to derive the coefficients of the matrix of this transformation can be defined from only two measurements: I–V curve measurement for the module and I–V curve measurement for the array of the modules. The information about the matrix leads to the evaluation of the additional arrays series and shunt resistances which are essential for the real array due to the presence of connecting wires, inverter, etc. Other application of the invariance is the simple tool for the PV array power optimization. The key element of the single diode model is the effective fitting algorithm which yields the five parameters from a large number of experimental points at I–V curve.

P‐59: Dielectric Constants of Display Optical Components

The paper introduces novel software code for evaluation of dielectric tensor of biaxial layer incorporated into multilayer stack. The algorithm utilizes the reflectance and transmttance for several polarization states and angles of incidence in the case of Berreman approach or reflective and transmissive Mueller-matrixes in the case of extended Jones method. We analyzed some common methods for characterization of LCD components by use of transmissive measurements.