© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.5.5.3.2 Leukocyte Surface Fluctuations and Elasticity

As with erythrocytes (Section 15.5.5.1.2), low frequency submicron cell membrane fluctuations (CMF) have also been observed in lymphocytes, monocytes, and even nonleukocytes such as fibroblasts at frequencies between 0.2-30 Hz [4079-4082], although the vertical amplitude of these fluctuations is typically only 20-30 nm over 0.25-micron² areas, far smaller than the RBC membrane fluctuations of 160-400 nm. However, murine B lymphocytes showed transverse displacements of 131 nm in 0.2-micron² microdomains at 0.3-15 Hz [4079]. Colchicine at 1 µM concentration reduced these membrane fluctuations down to 88 nm, whereas dihydrocytochalasin B at 2 µM increased the membrane displacement amplitude up to 184 nm [4079]. Medical nanorobots using leukocytes as cytovehicles (Section 9.4.7) – whether by external attachment or from a cytosolic residence – must take care to avoid impairing leukocytic plasma membrane fluctuations, whose biological function appears to be, at least in part, to assist the cell in achieving efficient diapedesis.

Leukocytes are also much less deformable than erythrocytes [5411-5414], especially when activated, hence WBCs may better resist cell deformation by passing nanorobots (Section 15.5.5.3.1). Venous blood from patients with ischemic “vibration white finger” caused by occupational exposure to ~120 Hz mechanical vibrations contains a subpopulation of hard and poorly deformable granulocytes [5410]. However, acute hand-transmitted vibration has no in vitro effect on leukocyte rheology [5410].

Last updated on 30 April 2004