Speaker
Description
Introduction
Chronic wounds are skin lesions that fail to heal naturally or through basic care. Pressure ulcers, diabetic foot ulcers and some oncologic and burn wounds present an open gateway for infections to attack the body [1]. Contributing to this scenario, often the patients have only one shot at reparative surgery, due to previous complications and/or the requirement of extended anesthesia. Commercial or surgical skin grafts have mixed results regarding compatibility and post-surgical outcomes [2]. To tackle these issues, tissue engineering was born to manufacture constructs using human cells (e.g. autologous) and/or growth factors, aiming at producing full-sized, functional organs. One of the initiatives inside tissue engineering is 3D Bioprinting, where a bioink with cells/growth factors is used to produce scaffolds (often created in vitro) to fabricate biocompatible anatomies. Among its techniques is in situ bioprinting, where the bioink is directly deposited on the patient's body, using the wound environment as the bioreactor to multiply the cells and fill the wound. Some recent advancements in this field have printed implants in vivo on pigs and mice [3][4]. Others have integrated partial patient tracking to perform intraoperative printing without complete anesthesia [5], or experimented with crosslinking using techniques that don’t involve UV light [6]. Still, no published work to date has integrated all these aspects into the same system. To fill this gap, the authors propose a new framework for an in situ bioprinter that integrates active patient tracking and always-perpendicular material deposition on a non-UV crosslinking system, aiming for maximum printability, mechanical properties and cell survival rates for the biofabricated implant.
Methods
The in situ bioprinter will comprise a 6 degrees-of-freedom (DoF) robotic arm and a custom bioink extruder assembled in-house. It will feature: 1) A non-planar slicing algorithm based on previous work from our group [7], capable of generating toolpaths that keep the extruder always perpendicular to the printer surface, while also accounting for tool head collision and compensating for impossible poses for the robot or the end-effector; 2) A tracking system composed of stationary cameras looking at fiducial markers that will recognize all possible 6 DoF of an awake patient, up to natural ranges, velocities and acceleration of motion; 3) a bioink containing liposomes as placeholders for cells, that is formulated to crosslink under visible light.
Results
Expected results are an enhanced implant adhesion and body adaptability due to the multi-DoF material deposition, a live compensation of any possible and feasible patient movement, also reducing the necessity for heavy anesthesia, and the reduction of harm factors due to the use of more natural, visible light during the biofabrication process. Future experimental validation will assess print fidelity, tracking range and cell viability.
Conclusion
The field of in situ bioprinting will be advanced by this work regarding the integration of many factors currently being developed separately, bringing this technology closer to its final, hospital-ready form.
Acknowledgements
This research was supported by the Natural Sciences and Engineering Research Council - Collaborative Research and Training Experience (NSERC - CREATE) (2020-543378).
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