Sheet-based extrusion bioprinting: a new multi-material paradigm providing mid-extrusion micropatterning control for microvascular applications.

As bioprinting advances into clinical relevance with patient-specific tissue and organ constructs, it must be capable of multi-material fabrication at high resolutions to accurately mimick the complex tissue structures found in the body. One of the most fundamental structures to regenerative medicine is microvasculature. Its continuous hierarchical branching vessel networks bridge surgically manipulatable arteries (∼1-6 mm) to capillary beds (∼10µm). Microvascular perfusion must be established quickly for autologous, allogeneic, or tissue engineered grafts to survive implantation and heal in place. However, traditional syringe-based bioprinting techniques have struggled to produce perfusable constructs with hierarchical branching at the resolution of the arterioles (∼100-10µm) found in microvascular tissues. This study introduces the novel CEVIC bioprinting device (i.e.ContinuouslyExtrudedVariableInternalChanneling), a multi-material technology that breaks the current extrusion-based bioprinting paradigm of pushing cell-laden hydrogels through a nozzle as filaments, instead, in the version explored here, extruding thin, wide cell-laden hydrogel sheets. The CEVIC device adapts the chaotic printing approach to control the width and number of microchannels within the construct as it is extruded (i.e. on-the-fly). Utilizing novel flow valve designs, this strategy can produce continuous gradients varying geometry and materials across the construct and hierarchical branching channels with average widths ranging from 621.5 ± 42.92%µm to 11.67 ± 14.99%µm, respectively, encompassing the resolution range of microvascular vessels. These constructs can also include fugitive/sacrificial ink that vacates to leave demonstrably perfusable channels. In a proof-of-concept experiment, a co-culture of two microvascular cell types, endothelial cells and pericytes, sustained over 90% viability throughout 1 week in microchannels within CEVIC-produced gelatin methacryloyl-sodium alginate hydrogel constructs. These results justify further exploration of generating CEVIC-bioprinted microvasculature, such as pre-culturing and implantation studies.

A Randomized Comparison of Clothing Removal Techniques in a Simulated Trauma Patient Exposure.

Introduction Trauma shears are commonly used by emergency medical services (EMS) providers to remove clothing from patients and expose underlying traumatic injuries. Other tools exist that may be more effective, but they are largely untested. This study compared the use of trauma shears versus two cutting hooks in removing clothing from a simulated trauma patient. Methods We recruited 18 paramedic students to participate in a cross-over study designed to remove clothing from a wholly dressed full-body training mannequin using trauma shears (with the cut-and-rip (CAR) technique) and two cutting hooks (S-Cut QE (ES Equipment AB, Nol, Sweden) and the Talon Rescue Emergency Clothing Knife (TRECK+, Talon Rescue, Farmington, CT, USA)). We determined the order of the tools using a three-by-three Latin square and randomized participants equally between possible orders to minimize carryover effects. We recorded times for total clothing removal and the removal of clothing from the upper and lower body, respectively. We employed a mixed-effects analysis of variance (ANOVA) to determine any differences between tools. Results Removal time was significantly faster with the S-Cut QE compared to the CAR technique and TRECK+ (mean 78 seconds, 95% confidence interval (CI) 52-103 vs. 142 seconds, 95% CI 117-167, vs. 209 seconds, 95% CI 184-235, p<0.001). The S-Cut QE was significantly faster than the CAR technique and TRECK+ for upper body clothing removal (mean 47 seconds, 95% CI 30-64 vs. 92 seconds, 95% CI 75-109, vs. 131 seconds, 95% CI 115-148, p<0.001) and the S-Cut QE and CAR were significantly faster than TRECK+ for lower body clothing removal (mean 25 seconds, 95% CI 11-38 and 44 seconds, 95% CI 31-58 vs. 71 seconds, 95% CI 58-85, p<0.001). Most (78%) participants preferred the S-Cut QE over other tools. Conclusion The S-Cut QE removed clothing from a simulated trauma patient faster than both the CAR and TRECK+. Emergency medical services (EMS) agencies should consider adding a cutting hook to their standard trauma kit.