Living cells sense and respond to their extracellular environment. Their contact guidance is affected by the underlying substrate morphology. Previous studies of the effect of substrate pattern on the mechanical behavior of living cells were only limited to the quantification of the cellular elasticity. However, how the length and time scales of the cellular mechanical properties are affected by the patterned substrates have yet to be studied. In this study, the effect of the substrate morphology on the biomechanical behavior of living cells was thoroughly investigated using indentation-based atomic force microscopy. The results showed that the cellular biomechanical behavior was affected by the substrate morphology significantly. The elasticity and viscosity of the cells on the patterned PDMS substrates were much lower compared to those cultured on flat PDMS. The poroelastic diffusion coefficient of the cells was higher on the patterned PDMS substrates, specifically on the substrate with 2D pitches. In addition, fluorescence images showed that the substrate topography directly affects the cell cytoskeleton morphology. Together, the results suggested that cell mechanical behavior and morphology can be controlled using substrates with properly designed topography.
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Rheological characterization of poly-dimethyl siloxane formulations with tunable viscoelastic properties
Studies from the past two decades have demonstrated convincingly that cells are able to sense the mechanical properties of their surroundings. Cells make major decisions in response to this mechanosensation, including decisions regarding cell migration, proliferation, survival, and differentiation. The vast majority of these studies have focused on the cellular mechanoresponse to changing substrate stiffness (or elastic modulus) and have been conducted on purely elastic substrates. In contrast, most soft tissues in the human body exhibit viscoelastic behavior; that is, they generate responsive force proportional to both the magnitude and rate of strain. While several recent studies have demonstrated that viscous effects of an underlying substrate affect cellular mechanoresponse, there is not a straightforward experimental method to probe this, particularly for investigators with little background in biomaterial fabrication. In the current work, we demonstrate that polymers comprised of differing polydimethylsiloxane (PDMS) formulations can be generated that allow for control over both the strain-dependent storage modulus and the strain rate-dependent loss modulus. These substrates requires no background in biomaterial fabrication to fabricate, are shelf-stable, and exhibit repeatable mechanical properties. Here we demonstrate that these substrates are biocompatible and exhibit similar protein adsorption characteristics regardless of mechanical properties. Finally, we develop a set of empirical equations that predicts the storage and loss modulus for a given blend of PDMS formulations, allowing users to tailor substrate mechanical properties to their specific needs.
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- Award ID(s):
- 2009748
- PAR ID:
- 10341919
- Date Published:
- Journal Name:
- RSC Advances
- Volume:
- 11
- Issue:
- 57
- ISSN:
- 2046-2069
- Page Range / eLocation ID:
- 35910 to 35917
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Cell–substrate interaction plays an important role in intracellular behavior and function. Adherent cell mechanics is directly regulated by the substrate mechanics. However, previous studies on the effect of substrate mechanics only focused on the stiffness relation between the substrate and the cells, and how the substrate stiffness affects the time-scale and length-scale of the cell mechanics has not yet been studied. The absence of this information directly limits the in-depth understanding of the cellular mechanotransduction process. In this study, the effect of substrate mechanics on the nonlinear biomechanical behavior of living cells was investigated using indentation-based atomic force microscopy. The mechanical properties and their nonlinearities of the cells cultured on four substrates with distinct mechanical properties were thoroughly investigated. Furthermore, the actin filament (F-actin) cytoskeleton of the cells was fluorescently stained to investigate the adaptation of F-actin cytoskeleton structure to the substrate mechanics. It was found that living cells sense and adapt to substrate mechanics: the cellular Young’s modulus, shear modulus, apparent viscosity, and their nonlinearities (mechanical property vs. measurement depth relation) were adapted to the substrates’ nonlinear mechanics. Moreover, the positive correlation between the cellular poroelasticity and the indentation remained the same regardless of the substrate stiffness nonlinearity, but was indeed more pronounced for the cells seeded on the softer substrates. Comparison of the F-actin cytoskeleton morphology confirmed that the substrate affects the cell mechanics by regulating the intracellular structure.more » « less
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Abstract Energy harvesting (EH) technologies have been rapidly developed to replace the batteries of biomechanical electronics, but efforts are still needed to close the technology gaps in achieving flexible and biocompatible energy harvesters. Current flexible energy harvesters based on ZnO nanoarrays require complex fabrication processes, and they are non‐stretchable as they are usually fabricated on hard substrates. In this work, a facile approach is reported for fabricating a substrate‐free energy harvester with ZnO nanoarrays directly and fully embedded in a skin‐like polydimethylsiloxane (PDMS) elastomeric matrix that shares a similar mechanical property with that of human skin. The flexible device, with an elastic modulus of 3.3 MPa, can be stretched to 250% of its original length, generates an open‐circuit voltage up to 9.2 Vppand power LEDs from finger‐hand motions. Further, the device collects energy from hand‐finger motions and heartbeats through ex and in vivo tests. A ≈0.3 Vppopen circuit voltage is generated from the device installed on a leadless pacemaker in a porcine model. This work suggests a generic design strategy that overcomes the mechanical mismatch between the energy materials and soft tissues for a wide range of biomechanical EH applications from wearables to implantable ones.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1ra03548g
