Qing Li
Qing Li, Ph.D.
Professor,
School of Aerospace, Mechanical and Mechatronic Engineering,
Australian Research Council Future Fellow,
Biomedical Engineering,
University of Sydney.
Email: Qing.Li@Sydney.edu.au

Biography:

Dr Qing Li obtained his PhD degree from the University of Sydney in 2000. He received postdoc training from Cornell University, NY, USA 2000 - 2001. He was a recipient of an Australian Research Council (ARC) Australian Postdoctoral (APD) Research Fellowship in 2001. Dr Qing Li was a senior lecturer in School of Engineering, James Cook University, Townsville, Australia from 2004 to 2006. He returned to Sydney by taking up a Sesqui senior lectureship in 2006, where he was promoted to Associate Professor in 2010 and Professor in 2014. Dr Qing Li is now an ARC Future Fellow (2013-2017) in biomedical engineering at the University of Sydney. His interests are in scaffold tissue engineering, computational modelling, biofabrication, biomechanics and biomaterials.


Abstract:

Design and Biofabrication of Vascular Network for in-vitro Study

Statement of Purpose: Bioprinting allows fabricating tissue constructs in a desirable structure. Nevertheless, cell survival in tissue constructs largely relies on efficient and sustained oxygen and metabolism transport (Radisic et al 2005). In this regard, vascularization plays a critical role to maintain viability of cells and functionalization of neotissue. For this reason, it becomes an important topic drawing considerable attention in biofabrication and regenerative medicine. However, formation of a well-organized 3D sophisticated network with rich tubules, mimicking native blood vessels and capillaries, remains a major challenge to date (Chen et al 2011).  Critically, a proper integration between the bioprinted tissue constructs and the host vasculature is imperative. This study aimed to develop an integrated procedure by combining computational topology optimization of vascular network in silico, with photolithography, bioprinting and experimental test in-vitro. It is expected that the protocol provides a feasible approach to generate optimal vascular networks for improving cell viability.

Methods: In this study we proposed a novel strategy for design of vascular system which enables to improve nutrient's transportation inside tissue constructs as part of scaffolding. We applied computational topology optimization algorithm for design of the vascular network which allows maximizing biotransport (diffusive) capacity of the entire scaffold domain for the given porosity and materials (Steven et al 2001).  For demonstrative purpose, a 2.5D constructing case was considered here for demonstrating the new method. The hydrogel was used as the construct material for cell growth here. A photolithography microfabrication procedure was applied for implementing the microscopic level of network. The optimized vascular topology was first used for generating a PDMS mold as mask through microfabrication technology. The fabricated mold was then used as a mask for UV cross-link of hydrogel. The cross-linked substance was finally washed away using PBS for obtaining a hydrogel scaffold.
The vascularized hydrogel scaffold was used for cellular study and the viability was monitored for comparing with the control group which has no patterned network.

Results: Application of topology optimization enabled us to generate novel pattern of vascular system for maximizing the nutrient diffusion inside the constructs. As shown in Fig. 1, a tree root-like vascular network was obtained in the square domain considered here, in which one inlet (bottom) was loaded in high concentration oxygen and other sides were blocked from transportation.  


Figure. 1 Vascular network obtained from topology optimization.

The in-vitro study showed that compared with the control group, the optimally-patterned vascularized tissue construct has better nutrient delivery, more favorable microenvironment for cells to survive and proliferate, which led to a high viability over the time of interest. The new procedure was thus considered useful for addressing transport problem in scaffold tissue engineering.


Figure 2. Comparison of optimized vascular network with control group in viability

Conclusions:  Application of topology optimization enabled us to generate novel pattern of vascular system for maximizing the nutrient diffusion inside tissue constructs. The in-vitro cellular study showed that the optimally-patterned and fabricated tissue construct has better nutrient delivery, more favorable microenvironment for cells to survive and proliferate, which led to a high viability over time of interest. The new procedure was thus considered useful for addressing transport problem in scaffold tissue engineering.

References:
Radisic et al (2005) Biotech Bioeng 93: 332-343.
Chen et al Biomaterials 32: 5003-5014.
Steven et al (2001) Comput Mech 26:129-139.




 
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Deadline for early registration
  September 15, 2017