Translating Biomolecular Recognition into Nanomechanics

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Translating Biomolecular Recognition into
Nanomechanics
Fritz J, Baller MK, Lang HP, Rothuizen H,
Vettiger P, Meyer E, Guntherodt H, Gerber C,
Gimzewski JK. Science 2000 Apr 14 288 (5464)
316-8.
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Introduction

• Adsorption of small molecules induces surface
  stress through electrostatic interactions and
  steric hindrance, which can bend a cantilever
  (Figure 1).
• This study applied the above principle to DNA
  fragments, which should only induce significant
  surface stress if the fragment on the cantilever
  is a precise match.

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Methods

• A single layer of receptor molecules was
  immobilized on one side of a cantilever array.
• One cantilever was functionalized with a 12-mer
  oligonucleotide, the other with a 16-mer (Figure
  2).
• The array was placed in a liquid cell of 800 ?L
  containing saline sodium citrate hybridization
  buffer at 22C.

Figure 2
4

• Two solutions were injected sequentially, one
  complimentary to each cantilevers
  oligonucleotides, resulting in hybridization
  (Figures 3 4).
• One laser illuminated each cantilever and
  reflected light was measured by a
  position-sensitive detector.
• The detector measured both individual cantilever
  deflection from starting position and their
  position relative to each other.

Figure 3
Figure 4
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Results

• Upon injection of the 16-mer, both deflection and
  differential signals increased.
• Differential signal reduced upon injection of
  12-mer.
• The experiment was successfully repeated with two
  12-mers which differed in only one base-pair
  (Figure 5).

Fig. 5. The injection of the first complementary
oligonucleotide increases the differential signal
(interval II) injection of the second
complementary oligonucleotide decreases the
differential signal (interval III).
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• A third experiment bound protein A from
  Staphylococcus aureus on one cantilever and
  bovine serum albumin (BSA) on the other as a
  control. Injection of immunoglobulins (IgG) from
  both rabbit and goat showed only binding of
  rabbit IgG to protein A. This was expected due
  to species-specific susceptibility to the
  protein.
• Increased concentration of oligonucleotides
  increases amplitude of differential signal.
• Arrays can be stored for several days at 4C with
  no loss of performance, and can also be reused at
  least 10 times.
• High reproducibility 1nm for same array 3nm
  for different arrays.

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Conclusions

• Biomolecular recognition sensitivity is as high
  as one base pair with a concentration detection
  limit of 10 nM.
• The technology is suitable for in situ operation.
• This method eliminates the requirement of
  labeling, optical excitation, or external probes.
• The forces exerted on the cantilevers are strong
  enough to manipulate micromechanical devices,
  including delivery devices which could be
  triggered by gene expression, immune responses,
  etc.

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Acknowledgements
Adrienne Tveit - Presenter Andy Krohn -
Manager Allison Kelliher - Reviewer Ryan Purcell
- Creator