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Biomechanical Characterization of Human Red Blood Cells
The cell mechanics of RBCs has been extensively investigated. It has
been reported that several factors may regulate the cell properties of RBCs,
such as chemical or drug treatment by thyroxine (Baskurt et al. 1990), nitric
oxide (Bor-Kucukatay et al. 2003), and lanthanum (Alexy et al. 2007) and
the effect of pH (Kuzman et al. 2000), temperature (Mills et al. 2007), and
cell age (Sutera et al. 1985). An important physiological condition, osmotic
stress has been found to have great influence on the biomechanical properties of some other types of cells; for example, articular chondrocytes (Guilak,
Erickson, and Ting-Beall 2002), human neutrophils (Ting-Beall, Needham,
and Hochmuth 1993), and Madin-Darby canine kidney cells (Steltenkamp et
al. 2006). However, little attention has been paid to its effect on human RBCs.
To investigate the influence of osmotic stress on the mechanical properties of RBCs, robotic manipulation technology with optical tweezers is utilized to study the cell mechanics of human RBCs in hypotonic solutions.
Increasing demands for both high precision and high throughput in cell
manipulation highlights the need for automated processing with robotics technology. Benefiting from great advances such as visual servoing
(Feddema and Simon 1998; Huang et al. 2009a, 2009b), microforce sensing
and control (Wejinya, Shen, and Xi 2008; Xie et al. 2009), motion control (Sun
and Mills 2002), microfabrication techniques (Zhang et al. 2004), and image
processing (Li, Zong, and Bi 2001), robotic manipulation of biological objects
has been achieved (Huang et al. 2009a, 2009b; Xie et al. 2009). In parallel,
optical tweezer technology is known for its ability to impose force and deformation on a microscaled object on the order of piconewtons (pN, 10 −12 N)
and nanometers (nm, 10 −9 m), respectively, in noncontact and noninvasive
manners. Combining these two advanced techniques, biological cells can be
manipulated with high precision and good controllability.
In this chapter, a cell mechanical model is developed from our previous
work (Tan, Sun, and Huang 2010; Tan et al. 2008, 2009, 2010a, 2010b) to model
the deformation behavior of human RBCs in optically induced cell stretching. Equilibrium equations are adopted to represent the force balance of the
biomembrane; a hyperelastic constitutive material, namely, Evans–Skalak
material, is utilized to describe the material characteristics of RBC membranes. According to the mechanical model, the relationship between the
stretching force and the induced deformation can be established. To investigate the osmotic effect on the mechanical properties of human RBCs, robotic
manipulation technology with optical tweezers is used to stretch human
RBCs in hypotonic conditions. RBCs are stretched to different levels of
deformation at various trapping forces. By fitting the modeling results to the
experimental data, the area compressibility modulus and the shear elastic
modulus of RBCs are obtained, which are less than the reported results of
the natural RBCs in isotonic conditions. This indicates the significant effect
of osmotic stress on the mechanical properties of human RBCs but also can
be used to shed light on the therapy and pathology of some human diseases.
Biomechanical Characterization of Human Red Blood Cells
The cell mechanics of RBCs has been extensively investigated. It has
been reported that several factors may regulate the cell properties of RBCs,
such as chemical or drug treatment by thyroxine (Baskurt et al. 1990), nitric
oxide (Bor-Kucukatay et al. 2003), and lanthanum (Alexy et al. 2007) and
the effect of pH (Kuzman et al. 2000), temperature (Mills et al. 2007), and
cell age (Sutera et al. 1985). An important physiological condition, osmotic
stress has been found to have great influence on the biomechanical properties of some other types of cells; for example, articular chondrocytes (Guilak,
Erickson, and Ting-Beall 2002), human neutrophils (Ting-Beall, Needham,
and Hochmuth 1993), and Madin-Darby canine kidney cells (Steltenkamp et
al. 2006). However, little attention has been paid to its effect on human RBCs.
To investigate the influence of osmotic stress on the mechanical properties of RBCs, robotic manipulation technology with optical tweezers is utilized to study the cell mechanics of human RBCs in hypotonic solutions.
Increasing demands for both high precision and high throughput in cell
manipulation highlights the need for automated processing with robotics technology. Benefiting from great advances such as visual servoing
(Feddema and Simon 1998; Huang et al. 2009a, 2009b), microforce sensing
and control (Wejinya, Shen, and Xi 2008; Xie et al. 2009), motion control (Sun
and Mills 2002), microfabrication techniques (Zhang et al. 2004), and image
processing (Li, Zong, and Bi 2001), robotic manipulation of biological objects
has been achieved (Huang et al. 2009a, 2009b; Xie et al. 2009). In parallel,
optical tweezer technology is known for its ability to impose force and deformation on a microscaled object on the order of piconewtons (pN, 10 −12 N)
and nanometers (nm, 10 −9 m), respectively, in noncontact and noninvasive
manners. Combining these two advanced techniques, biological cells can be
manipulated with high precision and good controllability.
In this chapter, a cell mechanical model is developed from our previous
work (Tan, Sun, and Huang 2010; Tan et al. 2008, 2009, 2010a, 2010b) to model
the deformation behavior of human RBCs in optically induced cell stretching. Equilibrium equations are adopted to represent the force balance of the
biomembrane; a hyperelastic constitutive material, namely, Evans–Skalak
material, is utilized to describe the material characteristics of RBC membranes. According to the mechanical model, the relationship between the
stretching force and the induced deformation can be established. To investigate the osmotic effect on the mechanical properties of human RBCs, robotic
manipulation technology with optical tweezers is used to stretch human
RBCs in hypotonic conditions. RBCs are stretched to different levels of
deformation at various trapping forces. By fitting the modeling results to the
experimental data, the area compressibility modulus and the shear elastic
modulus of RBCs are obtained, which are less than the reported results of
the natural RBCs in isotonic conditions. This indicates the significant effect
of osmotic stress on the mechanical properties of human RBCs but also can
be used to shed light on the therapy and pathology of some human diseases.