Browsing by Author "Zhou, Yingge"
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Item Effects of Viscosities and Solution Composition on Core-Sheath Electrospun Polycaprolactone(PCL) Nanoporous Microtubes(2021) Chen, Yan; Tan, George Z. (TTU); Zhou, YinggeVascularization for tissue engineering applications has been challenging over the past decades. Numerous efforts have been made to fabricate artificial arteries and veins, while few focused on capillary vascularization. In this paper, core-sheath electrospinning was adopted to fabricate nanoporous microtubes that mimic the native capillaries. The results showed that both solution viscosity and polyethylene oxide (PEO) ratio in polycaprolactone (PCL) sheath solution had significant effects on microtube diameter. Adding PEO into PCL sheath solution is also beneficial to surface pore formation, although the effects of further increasing PEO showed mixed results in different viscosity groups. Our study showed that the high viscosity group with a PCL/PEO ratio of 3:1 resulted in the highest average microtube diameter (2.14 µm) and pore size (250 nm), which mimics the native human capillary size of 1–10 µm. Therefore, our microtubes show high potential in tissue vascularization of engineered scaffolds.Item Fabrication of biomimetic scaffolds by electrospinning for tissue engineering applications(2020-08) Zhou, Yingge; Tan, George Z.; Zhang, Hong-Chao; Xu, Changxue; Du, DongpingTissue engineering has emerged as an alternative cell-based approach, aiming at replacement of damaged organs with in vitro generated tissue equivalents. Electrospinning has shown great potential in tissue engineering due to its versatile capabilities to create fibrous assemblies with structures mimicking extracellular matrix (ECM). This technique enables engineering scaffolds with multiple unique properties including micro to nanoscale topography, high porosity, and high surface to volume ratio. These properties are critical for enhancing cell attachment, regulating drug release, and promoting mass transfer properties. Fabrication of biomimetic cell microenvironment closely resembling the native tissues has become the latest strategy for regenerative medicine. However, it remains challenging to create scaffolds with tunable biomimetic microstructure close to native fibrous extra-cellular matrix on a clinically relevant scale. This research presented three novel electrospinning strategies to address this challenge. First, a rotation electrospinning system with a cone collector was developed to generate 2D fibrous mat with microtopology gradient. Multivariate analysis of variance (MANOVA) showed that the tip-to-axis distance (TAD) and rotation speed (RS) significantly influenced the gradient features including fiber diameter and fiber alignment. Second, a divergence electrospinning system was developed to create 3D scaffold comprising of aligned nanofibers. Factorial experiment revealed that inclination angle and length-to-width ratio influenced the electric field distribution and fiber gradients. The scaffolds provided topographical cues to promote human fibroblast cell adhesion, proliferation, and morphogenesis in 3D space. Future parametric and mechanism studies on materials properties such as viscosity, conductivity, and ambient parameters such as temperature are needed to establish quantitative relationships between process parameters and attribute gradients. In addition, a statistical model will be developed to predict the fiber distribution and geometry within the divergence electrospun scaffold. Thirdly, a novel electrospinning approach was developed to fabricate nanoporous polycaprolactone microtubes as potential functional capillaries. Our results showed that ambient environment parameters and solution properties affected the pore formation and tube morphology. The optimal tubular structure was obtained with consistent viscosities between the core and the sheath solutions. The biomimetic nanoporous microtubes hold great potential for vascularization in tissue engineering.Item Fabrication of Nanopores Polylactic Acid Microtubes by Core-Sheath Electrospinning for Capillary Vascularization(MDPI, 2021) Zhou, Yingge; Sooriyaarachchi, Dilshan; Tan, George Z.There has been substantial progress in tissue engineering of biological substitutes for medical applications. One of the major challenges in development of complex tissues is the difficulty of creating vascular networks for engineered constructs. The diameter of current artificial vascular channels is usually at millimeter or submillimeter level, while human capillaries are about 5 to 10 µm in diameter. In this paper, a novel core-sheath electrospinning process was adopted to fabricate nanoporous microtubes to mimic the structure of fenestrated capillary vessels. A mixture of polylactic acid (PLA) and polyethylene glycol (PEO) was used as the sheath solution and PEO was used as the core solution. The microtubes were observed under a scanning electron microscope and the images were analyzed by ImageJ. The diameter of the microtubes ranged from 1–8 microns. The diameter of the nanopores ranged from 100 to 800 nm. The statistical analysis showed that the microtube diameter was significantly influenced by the PEO ratio in the sheath solution, pump rate, and the viscosity gradient between the sheath and the core solution. The electrospun microtubes with nanoscale pores highly resemble human fenestrated capillaries. Therefore, the nanoporous microtubes have great potential to support vascularization in engineered tissues.