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Volumn 89, Issue 2, 2002, Pages

Dynamic Force Spectroscopy to Probe Adhesion Strength of Living Cells

Author keywords

[No Author keywords available]

Indexed keywords

BIOLOGICAL MEMBRANES; CELLS; CHEMICAL BONDS; FORCE MEASUREMENT; LOADS (FORCES); MOLECULAR DYNAMICS; PROTEINS; SPECTROSCOPIC ANALYSIS; STRENGTH OF MATERIALS; SURFACE TENSION;

EID: 4244178117     PISSN: 00319007     EISSN: 10797114     Source Type: Journal    
DOI: 10.1103/PhysRevLett.89.028101     Document Type: Article
Times cited : (65)

References (37)
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    • for a recent review, see R. Merkel, Phys. Rep. 346, 343 (2001).
    • (2001) Phys. Rep. , vol.346 , pp. 343
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    • The affinity of cyclic RGD peptides for different integrins was tested by measuring the peptide concentration necessary to reduce the amount of the respective integrins bound to vitronectin, their natural ligand, to (Formula presented). For the cyclic peptide used here this concentration was (Formula presented) for the integrin (Formula presented) and (Formula presented) for (Formula presented)
    • M. Pfaff, K. Tangemann, B. Müller, M. Gurrath, G. Müller, H. Kessler, R. Timpl, and J. Engel, J. Biol. Chem. 269, 20233 (1994). The affinity of cyclic RGD peptides for different integrins was tested by measuring the peptide concentration necessary to reduce the amount of the respective integrins bound to vitronectin, their natural ligand, to (Formula presented). For the cyclic peptide used here this concentration was (Formula presented) for the integrin (Formula presented) and (Formula presented) for (Formula presented).
    • (1994) J. Biol. Chem. , vol.269 , pp. 20233
    • Pfaff, M.1    Tangemann, K.2    Müller, B.3    Gurrath, M.4    Müller, G.5    Kessler, H.6    Timpl, R.7    Engel, J.8
  • 21
    • 85038330900 scopus 로고    scopus 로고
    • The vesicles were composed of di-elaidoyl-phosphatidyl-choline, cholesterol, di-oleoyl-phosphatidyl-ethanolamine-poly (Formula presented) (a PEG lipid), and the lipopeptide in a ratio of 50:50:1:4. Using a 1:1 mixture of cholesterol and phospholipid as matrix ensures membrane fluidity and mechanical toughness. The polymer moiety of the PEG lipid forms a dense layer covering the membrane that efficiently suppresses nonspecific interactions between cell and vesicle. The concentration of the PEG lipid was selected because at much lower density its passivation potency is impaired and at much higher concentration it forms micellar phases. Identical results were obtained at a 100 times lower lipopeptide concentration; therefore we did not further vary its concentration
    • The vesicles were composed of di-elaidoyl-phosphatidyl-choline, cholesterol, di-oleoyl-phosphatidyl-ethanolamine-poly (Formula presented) (a PEG lipid), and the lipopeptide in a ratio of 50:50:1:4. Using a 1:1 mixture of cholesterol and phospholipid as matrix ensures membrane fluidity and mechanical toughness. The polymer moiety of the PEG lipid forms a dense layer covering the membrane that efficiently suppresses nonspecific interactions between cell and vesicle. The concentration of the PEG lipid was selected because at much lower density its passivation potency is impaired and at much higher concentration it forms micellar phases. Identical results were obtained at a 100 times lower lipopeptide concentration; therefore we did not further vary its concentration.
  • 22
    • 85038271835 scopus 로고    scopus 로고
    • Cell viability was frequently checked after the experiments by the trypan blue test. In addition, no abnormal cell shapes (e.g., blebbing or rounding up) were observed. To ensure normal cell physiology the experiments were limited to durations of less than one hour
    • Cell viability was frequently checked after the experiments by the trypan blue test. In addition, no abnormal cell shapes (e.g., blebbing or rounding up) were observed. To ensure normal cell physiology the experiments were limited to durations of less than one hour.
  • 27
    • 85038304419 scopus 로고    scopus 로고
    • The specificity of this interaction was proven by three different tests: (i) experiments on cells that do not possess the integrin (Formula presented) (fibroblasts), (ii) experiments with vesicles that did not contain the lipopeptide, and (iii) experiments in a buffer containing (Formula presented) of the cyclic RGD peptide which saturated all binding sites. No adhesion was observed in any of these tests
    • The specificity of this interaction was proven by three different tests: (i) experiments on cells that do not possess the integrin (Formula presented) (fibroblasts), (ii) experiments with vesicles that did not contain the lipopeptide, and (iii) experiments in a buffer containing (Formula presented) of the cyclic RGD peptide which saturated all binding sites. No adhesion was observed in any of these tests.
  • 30
    • 85038313597 scopus 로고    scopus 로고
    • The total experimental error was calculated from the uncertainties of the individual input parameters for the calculation of the acting force, cf
    • The total experimental error was calculated from the uncertainties of the individual input parameters for the calculation of the acting force, cf.
  • 31
    • 85038277346 scopus 로고    scopus 로고
    • From the density of receptors (Formula presented) and the width of the bending zone ( (Formula presented); cf. Fig. 2) we estimate that the line density of loaded bonds is (Formula presented). In our experiments the total number of loaded bonds ranged from 40 to 400
    • From the density of receptors (Formula presented) and the width of the bending zone ( (Formula presented); cf. Fig. 2) we estimate that the line density of loaded bonds is (Formula presented). In our experiments the total number of loaded bonds ranged from 40 to 400.
  • 32
    • 0018101150 scopus 로고
    • G. I. Bell, Science 200, 618 (1978);
    • (1978) Science , vol.200 , pp. 618
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  • 36
    • 85038316942 scopus 로고    scopus 로고
    • Seifert’s model the bonds withstand a finite force at vanishing loading rates. This cannot be seen in our data, most likely because the corresponding ultralow loading rates could not be reached
    • In Seifert’s model the bonds withstand a finite force at vanishing loading rates. This cannot be seen in our data, most likely because the corresponding ultralow loading rates could not be reached.


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