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    Gelation kinetics of thiol-methylsulfone (MS) hydrogel formulations for 3D cell culture
    (Washington, D.C. : American Chemical Society, 2022) de Miguel-Jiménez, Adrián; Ebeling, Bastian; Paez, Julieta I.; Fink-Straube, Claudia; Pearson, Samuel; del Campo, Aranzazu
    Crosslinking chemistries that allow hydrogel formation within minutes are essential to achieve homogeneous networks and cell distributions in 3D cell culture. Thiol-methylsulfone (MS) crosslinking chemistry offers minutes-scale gelation under near-physiological conditions showing many desirable attributes for 3D cell encapsulation. Here we investigate the gelation kinetics and mechanical properties of PEG-based hydrogels formed by thiol-tetrazole methylsulfone (TzMS) crosslinking as a function of buffer, crosslinker structure, and degree of TzMS functionalization. Appropriate buffer selection ensured constant pH throughout crosslinking. The formulation containing cell adhesive ligand RGD and enzymatically-degradable peptide VPM gelled in ca. 4 min at pH 7.5, and stiffness could be increased from hundreds of Pascals to > 1 kPa by using excess VPM. The gelation times and stiffnesses for these hydrogels are highly suitable for 3D cell encapsulations, and pave the way for reliable 3D cell culture workflows in pipetting robots.
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    Melt Electrowriting of Scaffolds with a Porosity Gradient to Mimic the Matrix Structure of the Human Trabecular Meshwork
    (New York : Cold Spring Harbor Laboratory, 2022) Włodarczyk-Biegun, Małgorzata K.; Villiou, Maria; Koch, Marcus; Muth, Christina; Wang, Peixi; Ott, Jenna; del Campo, Aranzazu
    The permeability of the Human Trabecular Meshwork (HTM) regulates eye pressure via a porosity gradient across its thickness modulated by stacked layers of matrix fibrils and cells. Changes in HTM porosity are associated with increases in intraocular pressure and the progress of diseases like glaucoma. Engineered HTMs could help to understand the structure-function relation in natural tissues, and lead to new regenerative solutions. Here, melt electrowriting (MEW) is explored as a biofabrication technique to produce fibrillar, porous scaffolds that mimic the multilayer, gradient structure of native HTM. Poly(caprolactone) constructs with a height of 125-500 μm and fiber diameters of 10-12 μm are printed. Scaffolds with a tensile modulus between 5.6 and 13 MPa, and a static compression modulus in the range of 6-360 kPa are obtained by varying the scaffolds design, i.e., density and orientation of the fibers and number of stacked layers. Primary HTM cells attach to the scaffolds, proliferate, and form a confluent layer within 8-14 days, depending on the scaffold design. High cell viability and cell morphology close to that in the native tissue are observed. The present work demonstrates the utility of MEW to reconstruct complex morphological features of natural tissues.