title: Rheological properties of cells measured by optical tweezers.
abstract: BACKGROUND
  The viscoelastic properties of cells have been investigated by a variety of techniques. However, the experimental data reported in literature for viscoelastic moduli differ by up to three orders of magnitude. This has been attributed to differences in techniques and models for cell response as well as to the natural variability of cells.
  
  
  RESULTS
  In this work we develop and apply a new methodology based on optical tweezers to investigate the rheological behavior of fibroblasts, neurons and astrocytes in the frequency range from 1Hz to 35Hz, determining the storage and loss moduli of their membrane-cortex complex. To avoid distortions associated with cell probing techniques, we use a previously developed method that takes into account the influence of under bead cell thickness and bead immersion. These two parameters were carefully measured for the three cell types used. Employing the soft glass rheology model, we obtain the scaling exponent and the Young's modulus for each cell type. The obtained viscoelastic moduli are in the order of Pa. Among the three cell types, astrocytes have the lowest elastic modulus, while neurons and fibroblasts exhibit a more solid-like behavior.
  
  
  CONCLUSIONS
  Although some discrepancies with previous results remain and may be inevitable in view of natural variability, the methodology developed in this work allows us to explore the viscoelastic behavior of the membrane-cortex complex of different cell types as well as to compare their viscous and elastic moduli, obtained under identical and well-defined experimental conditions, relating them to the cell functions.
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.|Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-972 Brazil.
authors.forename: Yareni A
authors.initials: YA
authors.lastname: Ayala
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.
authors.forename: Bruno
authors.initials: B
authors.lastname: Pontes
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.|Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-972 Brazil.
authors.forename: Diney S
authors.initials: DS
authors.lastname: Ether
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.|Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-972 Brazil.
authors.forename: Luis B
authors.initials: LB
authors.lastname: Pires
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.
authors.forename: Glauber R
authors.initials: GR
authors.lastname: Araujo
authors.affiliation: Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.
authors.forename: Susana
authors.initials: S
authors.lastname: Frases
authors.affiliation: Universidade Federal do Rio de Janeiro - Pólo de Xerém, Duque de Caxias, Rio de Janeiro 25245-390 Brazil.
authors.forename: Luciana F
authors.initials: LF
authors.lastname: Romão
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
authors.affiliation: Instituto Estadual do Cérebro Paulo Niemeyer, Rio de Janeiro, Rio de Janeiro 20231-092 Brazil.
authors.forename: Vivaldo
authors.initials: V
authors.lastname: Moura-Neto
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.|Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-972 Brazil.
authors.forename: Nathan B
authors.initials: NB
authors.lastname: Viana
authors.affiliation: LPO-COPEA, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-902 Brazil.|Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro 21941-972 Brazil.
authors.forename: H Moysés
authors.initials: HM
authors.lastname: Nussenzveig
keywords: Astrocytes; Cell viscoelasticity; Fibroblasts; Membrane-cortex complex; Neurons; Optical tweezers; Rheology