Acoustic tweezing cytometry for mechanical phenotyping of macrophages and mechanopharmaceutical cytotripsy

Abstract

Macrophages are immune cells responsible for tissue debridement and fighting infection. Clofazimine, an FDA-approved antibiotic, accumulates and precipitates as rod-shaped, crystal-like drug inclusions within macrophage lysosomes. Drug treatment as well as pathophysiological states could induce changes in macrophage mechanical property which in turn impact their phenotype and function. Here we report the use of acoustic tweezing cytometry as a new approach for in situ mechanical phenotyping of macrophages and for targeted macrophage cytotripsy. Acoustic tweezing cytometry applies ultrasound pulses to exert controlled forces to individual cells via integrin-bound microbubbles, enabling a creep test for measuring cellular mechanical property or inducing irreversible changes to the cells. Our results revealed that macrophages with crystal-like drug inclusions became significantly softer with higher cell compliance, and behaved more elastic with faster creep and recovery time constants. On the contrary, phagocytosis of solid polyethylene microbeads or treatment with soluble clofazimine rendered macrophages stiffer. Most notably, application of ultrasound pulses of longer duration and higher amplitude in ATC actuated the integrin-bound microbubbles to mobilize the crystal-like drug inclusions inside macrophages, turning the rod-shaped drug inclusions into intracellular microblender that effectively destructed the cells. This phenomenon of acoustic mechanopharmaceutical cytotripsy may be exploited for ultrasound activated, macrophage-directed drug release and delivery.

Single-cell analysis of innate immune cell mechanics: an application to cancer immunology

“…47 This stiffness hampers the ingestion of additional particles, as phagocytosis requires deformability as a prerequisite. [47][48][49] Consequently, there seems to be a threshold for phagocytosis that can be reached either by engulfing numerous small particles or a few larger ones. 50 In addition, the higher viscosity of M2-like macrophages presumably facilitates their migration in porous interstitial-like environments, 38 supporting the major function of anti-inflammatory macrophages; phagocytosis followed by efflux from the tissue.…”

“…Macrophages with rod-shaped crystal-like drug inclusions were softer than macrophages that engulfed solid polyethylene microbeads 48…”

Cell‐Based Micro/Nano‐Robots for Biomedical Applications: A Review

“…For example, Rosania et al used acoustic tweezing cytometry to target macrophages during cytotripsy. [211] Further examples of biomimetic nanoparticles composed of macrophage membranes and functional nanoparticles can be found in previous reviews. [212,213] Among these examples, biomimetic nanoparticles can be driven by endogenous or exogenous stimuli for target cruises.…”

Engineering physical microenvironments to study innate immune cell biophysics

“…Aside from inherent differences in mechanical properties between the various innate immune cells, phagocytosis of various targets and inflammatory chemical stimulation differentially affect their mechanical properties. Although phagocytosis of crystal-like clofazimine leads to macrophage softening, 79 phagocytosis generally leads to stiffening due to increased ROS generation, which inhibits ingestion of additional particles since deformability is a prerequisite for phagocytosis. 77,79,80 As a result, there appears to be a limit to phagocytosis, which can either be met through the uptake of many small particles or a few large ones.…”