Comparative Analysis of Viscosity of Complex Liquids and Cytoplasm of Mammalian Cells at the Nanoscale

• Published in: Nano letters 2011-05, Vol.11 (5), p.2157-2163
• Main Authors: Kalwarczyk, Tomasz, Ziȩbacz, Natalia, Bielejewska, Anna, Zaboklicka, Ewa, Koynov, Kaloian, Szymański, Jȩdrzej, Wilk, Agnieszka, Patkowski, Adam, Gapiński, Jacek, Butt, Hans-Jürgen, Hołyst, Robert
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Cell Line; Condensed matter: structure, mechanical and thermal properties; Cytoplasm - metabolism; Diffusion; Exact sciences and technology; HeLa Cells; Humans; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Mice; Micelles; Molecular Weight; Nanoparticles - chemistry; Nanotechnology - methods; Physics; Polymers - chemistry; Polystyrenes - chemistry; Pressure; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Viscosity
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl2008218

We present a scaling formula for size-dependent viscosity coefficients for proteins, polymers, and fluorescent dyes diffusing in complex liquids. The formula was used to analyze the mobilities of probes of different sizes in HeLa and Swiss 3T3 mammalian cells. This analysis unveils in the cytoplasm two length scales: (i) the correlation length ξ (approximately 5 nm in HeLa and 7 nm in Swiss 3T3 cells) and (ii) the limiting length scale that marks the crossover between nano- and macroscale viscosity (approximately 86 nm in HeLa and 30 nm in Swiss 3T3 cells). During motion, probes smaller than ξ experienced matrix viscosity: ηmatrix ≈ 2.0 mPa·s for HeLa and 0.88 mPa·s for Swiss 3T3 cells. Probes much larger than the limiting length scale experienced macroscopic viscosity, ηmacro ≈ 4.4 × 10–2 and 2.4 × 10–2 Pa·s for HeLa and Swiss 3T3 cells, respectively. Our results are persistent for the lengths scales from 0.14 nm to a few hundred nanometers.