1,721,027 research outputs found
i-Rheo-optical assay: Measuring the viscoelastic properties of multicellular spheroids
Get PDFThis study introduces a novel mechanobiology assay, named “i-Rheo-optical assay”, that integrates rheology with optical microscopy for analysing the viscoelastic properties of multicellular spheroids. These spheroids serve as three-dimensional models resembling tissue structures. The innovative technique enables real-time observation and quantification of morphological responses to applied stress using a cost-effective microscope coverslip for constant compression force application. By bridging a knowledge gap in biophysical research, which has predominantly focused on the elastic properties while only minimally exploring the viscoelastic nature in multicellular systems, the i-Rheo-optical assay emerges as an effective tool. It facilitates the measurement of broadband viscoelastic compressional moduli in spheroids, here derived from cancer (PANC-1) and non-tumoral (NIH/3T3) cell lines during compression tests.
This approach plays a crucial role in elucidating the mechanical properties of spheroids and holds potential for identifying biomarkers to discriminate between healthy tissues and their pathological counterparts. Offering comprehensive insights into the biomechanical behaviour of biological systems, i-Rheo-optical assay marks a significant advancement in tissue engineering, cancer research, and therapeutic development
The mitotic chromosome periphery modulates chromosome mechanics
Get PDFIn dividing cells, chromosomes are coated in a sheath of proteins and RNA called the mitotic chromosome periphery. This sheath is thought to confer biophysical properties to chromosomes, critical for successful cell division. However, the details of chromosome mechanics, and specifically, if and how the chromosome periphery contributes to them, remain poorly understood. In this study, we present a comprehensive characterisation of single-chromosome mechanics using optical tweezers and an improved broadband microrheology analysis. We extend this analysis to direct measurements of the chromosome periphery by manipulating levels of Ki-67, its chief organiser, and apply a rheological model to isolate its contribution to chromosome mechanics. We report that the chromosome periphery governs dynamic self-reorganisation of chromosomes and acts as a structural constraint, providing force-damping properties. This work provides significant insight into chromosome mechanics and will inform our understanding of the mitotic chromosome periphery’s role in cell division
Comment on "A symmetrical method to obtain shear moduli from microrheology" by Kengo Nishi, Maria L. Kilfoil, Christoph F. Schmidt, and F. C. MacKintosh, Soft Matter, 2018, 14, 3716
Get PDFNishi et al. have presented a new analytical method for transforming the time-dependent materials' compliance into their frequency-dependent complex shear modulus, without the need of a preconceived fitting function nor the use of Kramers–Kronig transformations. They claim that their method significantly improves the accuracy of the outcomes, especially at high frequencies, up to “almost” the Nyquist frequency. Here, I corroborate that their method is actually able to provide a close estimation of the materials' complex shear modulus over the ‘entire’ range of explored frequencies (i.e. beyond the Nyquist frequency), as long as the compliance values are linearly spaced in the time-domain and its value at time zero is included as the first data point in the input file. Moreover, as a means of comparison, I employ the analytical method introduced by Tassieri et al. [New J. Phys., 2012, 14, 115032] for performing the Fourier transform of any generic time-dependent function that vanishes for negative times, is sampled at a finite rate, need not be equally spaced and extends over a finite time window. This existing method does not need preconceived fitting functions nor the use of Kramers–Kronig transformations; yet it shows a higher degree of accuracy compared to the one proposed by Nishi et al
Microrheology with optical tweezers: Peaks and troughs
Get PDFSince their first appearance in the 1970s, optical tweezers have been successfully exploited for a variety of applications throughout the natural sciences, revolutionising the field of microsensing. However, when adopted for microrheology studies, there exist some peaks and troughs on their modus operandi and data analysis that I wish to address and possibly iron out, providing a guide to future rheological studies from a microscopic perspective
Linear microrheology with optical tweezers of living cells 'is not an option'!
Get PDFOptical tweezers have been successfully adopted as exceptionally sensitive transducers for microrheology studies of complex fluids. Despite the general trend, in this article I explain why a similar approach should not be adopted for microrheology studies of living cells. This conclusion is reached on the basis of statistical mechanics principles that indicate the unsuitability of optical tweezers for such purpose
- …
