Simulating image-guided in situ bioprinting of a skin graft onto a phantom burn wound bed

Abstract

Deep skin thermal wounds require skin excision and engraftment. Clinical treatment for deep skin wounds is the use of autologous split-thickness skin grafts. However, timely coverage of large-area burn wounds remains a significant challenge. Engineered skin tissue constructs aim to overcome the limitations of traditional clinical intervention. In this study, an in situ bioprinting-based methodological workflow is advanced to directly fabricate a custom engineered skin graft onto a skin burn phantom. To illustrate this modular approach, a burn phantom is first created by mold casting gelatin-alginate hydrogel material to simulate a burn wound bed with arbitrary 2D shape and uniform depth. The cast hydrogel phantom is then placed on the printer platform to host the to-be-printed skin graft. Next, a color image-based module is proposed to extract the contour of the burn wound. This is followed by implementing a contour calibration process based on fiducial markers to yield the real dimension and pose of the burn phantom. A new directed toolpath generation algorithm is detailed to generate a burn-specific toolpath for the microextrusion-based bioprinting process. Based on this method, the bioprinted cell-laden gelatin-alginate hydrogel filaments are precisely arranged in a meshed pattern that is bound by the burn phantom contour. Internal geometries defined by the filament and pore dimensional characteristics of the printed construct design can be controlled to promote cell viability, proliferation, and nutrient delivery. Printed cell-laden multi-layered constructs are evaluated for single filament and pore dimensional precision, alignment of filaments between layers, and positional accuracy of the filaments within the extracted contour. Finally, a 24-hour time course incubation study reveals that the printed constructs preserve their structural properties while cells proliferate and maintain their spatial positioning.