Fig. 1. A hydrogel microparticle system to interrogate cargo mechanosensing.

a Schematic diagram for DAAM particle synthesis (see “Methods” section). Particle rigidity depends on the ratio of cross-linker to monomer. AIBN azobisisobutyronitrile. b Representative images of DAAM particles, prepared using the indicated bis-acrylamide contents and conjugated to LRB and FITC. Scale bars = 10 µm. c Atomic force microscopy measurements of stiffness (Young’s modulus) for particles prepared using the indicated bis-acrylamide contents. n = 36 (for 0.234% and 0.04%) or 34 (for 0.065% and 0.032%) DAAM particles. Error bars denote standard deviation (SD). d, e BMDMs were challenged with DAAM particles coated with different phagocytic ligands and particle uptake quantified by flow cytometry. d Top, schematic diagram for LRB/FITC dependent tracking of phagocytosis. Bottom, representative gating for flow cytometry-based quantification. e Uptake efficiency of DAAM particles coated with the indicated phagocytic ligands is graphed against particle stiffness. Columns and error bars denote mean and standard deviation (SD), respectively. n = 3 biological replicates. f–h BMDMs were imaged together with IgG-coated DAAM particles. f Representative brightfield and epifluorescence images of BMDMs phagocytosing DAAM particles of the indicated stiffness. Phagocytosed particles turn red, while unengulfed particles are yellow. Scale bars = 50 µm. g Phagocytosis quantified as the fraction of particles acidified per field of view after 2 h. Each point represents the mean of four fields of view in one technical replicate. Horizontal lines in each column denote the overall mean. P value determined by two-tailed Student’s t-test. h Histogram showing the number of 18 and 0.6 kPa particles phagocytosed per cell after 2 h. Schematics in (a), (d), and (e) created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license https://creativecommons.org/licenses/by-nc-nd/4.0/deed.en.