One-Step Formation of Protein-Based Tubular Structures for Functional Devices and Tissues.

Tubular biological structures consisting of extracellular matrix (ECM) proteins and cells are basic functional units of all organs in animals and humans. ECM protein solutions at low concentrations (5-10 milligrams per milliliter) are abundantly used in 3D cell culture. However, their poor "printability" and minute-long gelation time have made the direct extrusion of tubular structures in bioprinting applications challenging. Here, this limitation is overcome and the continuous, template-free conversion of low-concentration collagen, elastin, and fibrinogen solutions into tubular structures of tailored size and radial, circumferential and axial organization is demonstrated. The approach is enabled by a microfabricated printhead for the consistent circumferential distribution of ECM protein solutions and lends itself to scalable manufacture. The attached confinement accommodates minute-long residence times for pH, temperature, light, ionic and enzymatic gelation. Chip hosted ECM tubular structures are amenable to perfusion with aqueous solutions and air, and cyclic stretching. Predictive collapse and reopening in a crossed-tube configuration promote all-ECM valves and pumps. Tissue level function is demonstrated by factors secreted from cells embedded within the tube wall, as well as endothelial or epithelial barriers lining the lumen. The described approaches are anticipated to find applications in ECM-based organ-on-chip and biohybrid structures, hydraulic actuators, and soft machines.

Implant-assisted removable partial denture: An approach to switch Kennedy Class I to Kennedy Class III.

The Kennedy Class I and II distal extension situation poses a challenge to the prosthodontist as it inherently possesses a lack of stability, which may be attributed to the difference in compressibility of the mucosa and the periodontal ligament surrounding the distal-most abutment tooth. This results in a rotational tendency of the prosthesis around the line connecting its terminal abutments. Placement of osseointegrated dental implants in the posterior edentulous regions, distal to the terminal abutment provides improved vertical support to the distal extension removable partial denture, effectively converting its intraoral performance from a Kennedy Class I to a Class III situation, thereby resulting in improved stability of the prosthesis and consequently, enhanced patient satisfaction. This case report describes such an approach to the restoration of a Kennedy Class I partially edentulous situation.