Abstract Contact guidance is the phenomena of how cells respond to the topography of their external environment. The morphological and dynamic cell responses are strongly influenced by topographic features such as lateral and vertical dimensions, namely, ridge and groove widths and groove depth (\({\text{R}}_{\text{w}}, {\text{G}}_{\text{w}}, \text{a}\text{n}\text{d} {\text{G}}_{\text{D}}\), respectively). However, experimental studies that independently quantify the effect of the individual dimensions as well as their coupling on cellular function are still limited. In this work, we perform extensive parametric studies in the dimensional space–well beyond the previously studied range in the literature–to explore topographical effects on morphology and migration of Hs27 fibroblasts via static and dynamic analyses of live cell images. Our static analysis reveals that the \({\text{G}}_{\text{D}}\) is most significant, followed by the \({\text{R}}_{\text{w}}\). The fibroblasts appear to be more elongated and aligned in the groove direction as the \({\text{G}}_{\text{D}}\) increases, but their trend changes after 725 nm. Interestingly, the cell shape and alignment show a very strong correlation regardless of \({\text{G}}_{\text{D}}\). Our dynamic analysis confirms that directional cell migration is also strongly influenced by the \({\text{G}}_{\text{D}}\), while the effect of the \({\text{R}}_{\text{w}}\) and \({\text{G}}_{\text{w}}\) is statistically insignificant. Directional cell migration, as observed in the static cell behavior, shows the statistically significant transition when the \({\text{G}}_{\text{D}}\) is 725 nm, showing the intimate links between cell morphology and migration. We propose possible scenarios to offer mechanistic explanations of the observed cell behavior.
Cavitation bubbles form in soft biological systems when subjected to a negative pressure above a critical threshold, and dynamically change their size and shape in a violent manner. The critical threshold and dynamic response of these bubbles are known to be sensitive to the mechanical characteristics of highly compliant biological systems. Several recent studies have demonstrated different biological implications of cavitation events in biological systems, from therapeutic drug delivery and microsurgery to blunt injury mechanisms. Due to the rapidly increasing relevance of cavitation in biological and biomedical communities, it is necessary to review the current state-of-the-art theoretical framework, experimental techniques, and research trends with an emphasis on cavitation behavior in biologically relevant systems (e.g., tissue simulant and organs). In this review, we first introduce several theoretical models that predict bubble response in different types of biological systems and discuss the use of each model with physical interpretations. Then, we review the experimental techniques that allow the characterization of cavitation in biologically relevant systems with in-depth discussions of their unique advantages and disadvantages. Finally, we highlight key biological studies and findings, through the direct use of live cells or organs, for each experimental approach.
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