Passive and Active Microrheology for Biomedical Systems

Abstract

Microrheology encompasses a range of methods to measure the mechanical properties of soft materials. By characterizing the motion of embedded microscopic particles, microrheology extends the probing length scale and frequency range of conventional bulk rheology. Microrheology can be characterized into either passive or active methods based on the driving force exerted on probe particles. Tracer particles are driven by thermal energy in passive methods, applying minimal deformation to the assessed medium. In active techniques, particles are manipulated by an external force, most commonly produced through optical and magnetic fields. Small-scale rheology holds significant advantages over conventional bulk rheology, such as eliminating the need for large sample sizes, the ability to probe fragile materials non-destructively, and a wider probing frequency range. More importantly, some microrheological techniques can obtain spatiotemporal information of local microenvironments and accurately describe the heterogeneity of structurally complex fluids. Recently, there has been significant growth in using these minimally invasive techniques to investigate a wide range of biomedical systems both in vitro and in vivo. Here, we review the latest applications and advancements of microrheology in mammalian cells, tissues, and biofluids and discuss the current challenges and potential future advances on the horizon.

Quantitative Detection of Biological Nanovesicles in Drops of Saliva Using Microcantilevers

“…To independently quantify S , we used microrheology with tracers ranging from 70 to 370 nm (see Supporting Information section 3 and Table S1). If the tracers are able to diffuse freely within the mesh (Figure a), their mean square displacement (MSD) is expected to follow standard Brownian diffusion and grow linearly over time. , In contrast, if the tracers’ diffusion is hampered by the mesh (Figure b,c), a subdiffusive behavior is expected whereby the MSD is proportional to the time at a power α < 1. It is therefore convenient to track the anomalous diffusion exponent α for each tracer in order to distinguish “free” (α = 1) from mesh-hindered (α < 1) diffusion.…”

A Comparative Evaluation of the Structural and Biomechanical Properties of Food-Grade Biopolymers as Potential Hydrogel Building Blocks

“…This might explain the similarities in terms of the analyzed parameters between PP, GG, KG, and PS ( Figure 5 ). Moreover, in the case of the solid–liquid balance (SLB), PP, GG, KG, INU, and PS had the lowest values (SLB < 0.5), which confirms the formation of a gel structure (G’ > G”)—the samples exhibited typical solid-like (elastic) behavior [ 64 ]. On the other hand, WP, MD, and TG did not form a gel structure, which was observed based on the MSD profiles ( Figure 2 ).…”

Appetizer on soft matter physics concepts in mechanobiology

“…Meanwhile, its counterpart considering the probing into small objects on the intracellular scale has also been developed (Mason, 2000; Mason & Weitz, 1995). There are passive and active protocols designed for different purposes (Brau et al, 2007; Furst & Squires, 2017; Mao et al, 2022; Wirtz et al, 2009; Zia, 2018). The passive (micro)rheology utilizes the intrinsic fluctuations of particle positions embedded in the material, and one measures the mean square displacement of the particles.…”