Handheld Microfluidic Bioprinter for In Situ Delivery of Skin Tissue Constructs

Full-thickness burns where both the epidermal and dermal layer of the skin are destroyed lead to high patient mortality due to complications like dehydration, infection, and shock. The current standard of care involves isolating healthy skin from uninjured regions, followed by meshing and grafting onto the debrided wound site. However, this approach is not appropriate for patients with large area burns covering over 40% of the total burn surface area as insufficient quantities of healthy skin remain. Although many bioprinting approaches have been developed to meet this demand by converting biopolymer solutions, or “bioinks”, into three-dimensional tissue structures, current bioprinters are primarily designed for laboratory use and allow only small, centimeter-sized tissues to be prepared. Here, a novel handheld bioprinting system for in situ delivery of cell-containing biomaterial constructs was designed to deliver a variety of cell types embedded in alginates, collagens, or fibrins, accounting for unique physical properties and gelation mechanisms of each biomaterial. This technology was shown to be compatible with primary keratinocytes, dermal fibroblasts, and mesenchymal stem cells, allowing cell organization into distinct patterns such as stripes, spots, and bilayers using a microfluidic printhead. To enable conformal and consistent biomaterial construct delivery onto physiological substrates, a two degree-of-freedom rotational printhead and a compliant silicone wheel was integrated into the printhead setup. A fibrin-hyaluronic acid bioink composition was optimized to promote the formation of tissue constructs on tilted surfaces, balancing appropriate enzymatic gelation times with resistance to material drainage. In a case study to determine the utility of this approach, mesenchymal stromal cells delivered using the handheld bioprinter were shown to improve wound healing outcomes on four porcine models of full-thickness burn. Lastly, the capabilities of the instrument were further developed by implementing active and passive temperature control to allow consistent deposition of collagen-based bioinks, and by integrating disposable thermoplastic printheads fabricated using silicon wafer-based thermal embossing to enable sterile operation in a clinical setting. Taken together, this handheld bioprinter enables the conformal delivery of cell-containing extracellular matrix bioinks in situ and lays the foundation for future human clinical trials for the treatment of large-area, full-thickness burns.Ph.D