Mechanical Properties of Hydrated Acoustically Sensitive Alginate-Based Microcapsules Confined in a Microfluidic Device as a Function of Size and Composition

Understanding the mechanical properties of alginate-based microcapsules according to size and chemical composition allows researchers to zero in on the treatment and methods required to engineer optimized implantable alginate-based artificial cells for chemotherapy. Cross-linked medium viscosity alginate capsules ranging from 1.1% (w/v)-1.8% (w/v) in composition and 200 μm-1200 μm in size, encapsulating ultrasound contrast agents and blue dextran were compressed within a 40 μm high polydimethylsiloxane microfluidic device and subsequently examined using 2D microscopy for strain deformation aimed at the calculation of poisson ratios and volume loss postcompression. Results indicate a decrease in Poisson ratio as a function of alginate concentration, with statistically significant increases in Poisson ratios and percent volume loss as a function of size and composition. For an average of 120 s observation time post compression, in light of the volume loss correlated to the number of cross-links as a function of capsule size and alginate concentration, a strong case for the dominance of poroelasticity vs. viscoelasticity can be made. While there was a decrease in mean Poisson ratio as a function of concentration, at 1.8% (w/v) the mean strain value converged to 0.5, the theoretical ideal isotropic value associated with soft biological tissue.