In vivo implantation and perfusion of a gel containing 3D printed internal microvascular networks

Abstract

Event Abstract Back to Event In vivo implantation and perfusion of a gel containing 3D printed internal microvascular networks Renganaden Sooppan1, Samantha J. Paulsen2, Jason Han1, Anderson H. Ta2, Patrick Dinh1, Ann C. Gaffey1, Chantel Venkataraman1, Alen Trubelja1, George Hung1, Jordan S. Miller2 and Pavan Atluri1 1 University of Pennsylvania, Department of Surgery, United States 2 Rice University, Bioengineering, United States Introduction: Recent advances in 3D bioprinting have enabled the development of tissues containing micro-channel networks for rapid perfusion of engineered tissues. However, little focus has been placed on developing new surgical implantation techniques that allow for immediate perfusion of the engineered channels, which is essential for maintaining the viability of cells within the engineered tissue. To address these concerns, we have developed a proof-of-concept technique for the in vivo implantation of vascularized constructs in-line with a rat femoral artery. Methods: We first produced polydimethylsiloxane (PDMS) gels containing micro-channel networks using sacrificial carbohydrate glass-extrusion printing. Micro-channel networks consisted of a single inlet and outlet channel that branched into four discrete channels. Then, to assess channel patency and flow rates, we first scanned sample gels using micro-computed tomography then used the reconstructed channel architecture to generate a computational fluid dynamics model for the scanned gels. Flow rates through the channels were predicted using an inlet flow rate of 0.12 mL/min (Figure 1). Gels were implanted in-line with the femoral arteries of ten male Wistar rats. First, a 3 cm incision was made to expose the femoral sheath. The femoral artery was then isolated, and a silk suture was used to obtain control of the artery. The proximal and distal arteries were then cannulated using separate angiocatheters, which were secured by the silk sutures. The proximal and distal ends of the artery were then temporarily clamped before transecting the artery and trimming the angiocatheters to fit the inlet and outlet channels of the PDMS gel. Next, the catheters were mounted in the inlet and outlet of the gel before removing the clamp and allowing blood to flow. Flow through the channels was then monitored through the gel using laser Doppler imaging technology over 3 hours. Results and Discussion: Using computational modeling of flow through the reconstructed geometry of sample gels, we determined that each channel of the gel was patent, but we noticed that the flow rates were highest through the first and last branches of the channel network, highlighting the non-obvious nature of fluid flow and the need to rigorously quantify fluid flow regimes through printed channels (Figure 1). After implantation of the gels, laser Doppler imaging results showed that there was noticeably more flow through the PDMS gel and paw at 1 and 3 hours post implantation compared with the negative control group, which had ligated femoral arteries without an implanted gel. However, after 3 hours little flow was observed through the gel due to clotting (Figure 2). Conclusion: Our study provides a method for in vivo implantation of vascularized gels allowing for immediate perfusion of the channel network. When implanting hydrogels containing high cell concentrations, rapid perfusion is necessary for maintaining cell viability and function. Furthermore, by using computational modeling to assess flow prior to implantation we can better understand the mass transport within an implanted gels to predict cell viability and function. In future work we will focus on improving the hemocompatibility of the implanted gels to prevent clotting and improve patency of the implanted channel networks over time. Tegy Vadakkan