In-Situ Oxidative Polymerization of Pyrrole Composited with Cellulose Nanocrystal by Reactive Ink-Jet Printing on Fiber Substrates

A simple and novel method for the deposition of polypyrrole (PPy) and cellulose nanocrystal (CNC) composites on different fiber substrates by reactive ink-jet printing was proposed. PPy/CNCs composites were successfully prepared, and the surface resistance of conductive layer deposited on different fiber substrates is the least when the monomer concentration is 0.6 M. PPy/CNCs were deposited on polyethylene terephthalate (PET) to form a conductive layer by adding polyvinyl alcohol (PVA), and the optimum sintering temperature is 100 °C (monomer/PVA ratio 4.0, conductivity 0.769 S cm⁻¹). The PPy/CNCs conductive layer deposited on the paper has the lowest surface resistance and the best adhesion, and the surface resistance of PPy/CNCs conductive layer decreases first and then increases with the increase of sulfonate concentration. Moreover, the volume of anion in sulfonate will affect the arrangement and aggregation of PPy molecular chain in composite materials. Appropriate sulfonate doping can improve the conductivity and stability of conductive paper, and the maximum conductivity is 0.813 S cm⁻¹. Three devices based on PPy/CNCs conductive paper were proposed and fabricated. Therefore, this ink-jet printing provides a new method for the preparation of conductive materials, sensors, energy storage and electromagnetic shielding, etc.

Influence of Substrate Structure and Associated Properties on Endothelial Cell Behavior in the Context of Behaviors Associated with Laminar Flow Conditions

In order to treat most vascular diseases, arterial grafts are commonly employed for replacing small-diameter vessels, yet they often cause thrombosis. The growth of endothelial cells along the interior surfaces of these grafts (substrates) is critical to mitigate thrombosis. Typically, endothelial cells are cultured inside these grafts under laminar flow conditions to emulate the native environment of blood vessels and produce an endothelium. Alternatively, the substrate structure could have a similar influence on endothelial cell behavior as laminar flow conditions. In this study, we investigated whether substrates with aligned fiber structures could induce responses in human umbilical vein endothelial cells (HUVECs) akin to those elicited by laminar flow. Our observations revealed that HUVECs on aligned substrates displayed significant morphological changes, aligning parallel to the fibers, similar to effects reported under laminar flow conditions. Conversely, HUVECs on random substrates maintained their characteristic cobblestone appearance. Notably, cell migration was more significant on aligned substrates. Also, we observed that while vWF expression was similar between both substrates, the HUVECs on aligned substrates showed more expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31), laminin, and collagen IV. Additionally, these cells exhibited increased gene expression related to critical functions such as proliferation, extracellular matrix production, cytoskeletal reorganization, autophagy, and antithrombotic activity. These findings indicated that aligned substrates enhanced endothelial growth and behavior compared to random substrates. These improvements are similar to the beneficial effects of laminar flow on endothelial cells, which are well-documented compared to static or turbulent flow conditions.