Three-dimensional (3D) bioprinting is a novel technology utilizing biocompatible materials, cells, drugs, etc. as basic microcomponents to form 3D artificial structures and is believed as a promising method for regenerative medicine. Droplet-based bioprinting can precisely generate microspheres and manipulate them into organized structures with high fidelity. Biocompatible hydrogels are usually used as bioinks in 3D bioprinting, however, the viscosity of the bioink could be increased due to the additives such as cells, drugs, nutrient factors and other functional polymers in some particular applications, making it difficult to form monodispersed microspheres from high-viscosity bioink at the orifice of the nozzle. In this work, we reported a novel microfluidic-based printing nozzle to prepare monodispersed microspheres from high-viscosity bioink using the phase-inversion method. Different flowing conditions can be achieved by changing the flow rates of the fluids to form monodispersed solid and hollow microspheres using the same nozzle. The diameter of the microspheres can be tuned by changing the flow rate ratio and the size distribution of the microspheres is narrow. The prepared calcium alginate microspheres could also act as micro-carriers in drug delivery.

Novel starch/fiber composites with open cell structures were proposed through thermo-cavity molding.

Acute kidney injury (AKI) is a common and severe problem associated with high morbidity, mortality, and healthcare costs. There are no reliable therapeutic interventions except dialysis that could improve survival, limit injury, or speed up recovery. Thus, it is essential to develop new therapies to treat AKI. Previous studies revealed that histone deacetylase inhibitor (HDACi) could attenuate renal injury and enhance kidney recovery in AKI. However, the hydrophobic nature of HDACi, such as vorinostat (SAHA), requires organic solvents to promote its dissolution, leading to inevitable detrimental effects. Herein, calcium alginate microspheres (CAM) were prepared by the microfluidic method as HDACi carriers to treat AKI by intravenous injection. First, we designed the structure of the microfluidic channel for the fabrication of the PDMS microfluidic chip in which the emulsion state of droplets was analyzed. As the flow rate increases, the continuous phase changed from laminar flow to the dripping pattern in the microfluidic device. Then, the CAM was fabricated by a W/O microfluidic emulsion template and the size of the microspheres was adjusted from 3 to 7 μm by the concentration of alginate and the flow rate of the continuous phase and dispersal phase. The higher degree of cross-linking of sodium alginate with calcium ions would lead to longer drug release time but lower swelling rates. Furthermore, we selected CAM with suitable sizes as the HDACi carrier and delivered the HDACi-loaded CAM to the AKI mice by intravenous tail injection. The in vivo results showed that the HDACi-loaded CAM could effectively reduce the renal regional inflammatory response and attenuate renal injury.