Viscosity Estimation of a Suspension with Rigid Spheres in Circular Microchannels Using Particle Tracking Velocimetry

Development of Gelatin-Coated Hydrogel Microspheres for Novel Bioink Design: A Crosslinker Study

The development of vascularized tissue is a substantial challenge within the field of tissue engineering and regenerative medicine. Studies have shown that positively-charged microspheres exhibit dual-functions: (1) facilitation of vascularization and (2) controlled release of bioactive compounds. In this study, gelatin-coated microspheres were produced and processed with either EDC or transglutaminase, two crosslinkers. The results indicated that the processing stages did not significantly impact the size of the microspheres. EDC and transglutaminase had different effects on surface morphology and microsphere stability in a simulated colonic environment. Incorporation of EGM and TGM into bioink did not negatively impact bioprintability (as indicated by density and kinematic viscosity), and the microspheres had a uniform distribution within the scaffold. These microspheres show great potential for tissue engineering applications.

OCT particle tracking velocimetry of biofluids in a microparallel plate strain induction chamber

SIGNIFICANCE

Imaging biofluid flow under physiologic conditions aids in understanding disease processes and health complications. We present a method employing a microparallel plate strain induction chamber (MPPSIC) amenable to optical coherence tomography to track depth-resolved lateral displacement in fluids in real time while under constant and sinusoidal shear.

AIM

Our objective is to track biofluid motion under shearing conditions found in the respiratory epithelium, first validating methods in Newtonian fluids and subsequently assessing the capability of motion-tracking in bronchial mucus.

APPROACH

The motion of polystyrene microspheres in aqueous glycerol is tracked under constant and sinusoidal applied shear rates in the MPPSIC and is compared with theory. Then 1.5 wt. % bronchial mucus samples considered to be in a normal hydrated state are studied under sinusoidal shear rates of amplitudes 0.7 to 3.2  s  -  1.

RESULTS

Newtonian fluids under low Reynolds conditions (Re  ∼  10  -  4) exhibit velocity decreases directly proportional to the distance from the plate driven at both constant and oscillating velocities, consistent with Navier-Stokes's first and second problems at finite depths. A 1.5 wt. % mucus sample also exhibits a uniform shear strain profile.

CONCLUSIONS

The MPPSIC provides a new capability for studying biofluids, such as mucus, to assess potentially non-linear or strain-rate-dependent properties in a regime that is relevant to the mucus layer in the lung epithelium.