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DNA nanofilm thickness measurement on microarray in air and in liquid using an atomic force microscope
Guillaume Legay1, Eric Finot, Rita Meunier-Prest
1Laboratoire de Physique, UMR CNRS 5027, Université de Bourgogne, BP 47870, 9 Rue A. Savary, 21078 Dijon Cedex, France.
Biosensors & Bioelectronics
|October 6, 2005
Summary
DNA film thickness on biosensors varies with environment. Atomic force microscopy (AFM) reveals DNA strand height changes in air versus liquid, impacting signal response.
Area of Science:
- Nanotechnology
- Biophysics
- Surface Science
Background:
- Understanding DNA film thickness is crucial for biosensor signal response.
- Thiol-modified DNA strands are immobilized on gold micropads for biosensing applications.
Purpose of the Study:
- To measure DNA film thickness on microarrays in different media (liquid, air).
- To investigate the influence of DNA strand length and environment on film thickness and morphology.
- To explore adhesion force as a metric for biolayer surface coverage.
Main Methods:
- Atomic Force Microscopy (AFM) in height and force modes was utilized.
- AFM height mode measured changes in pad thickness.
- AFM force mode measured nanofilm indentation depth and adhesion forces.
Main Results:
- Coherence between AFM height and force modes was observed for film thickness in air.
- Adhesion force provides a method for nanoscopic surface coverage measurement.
- DNA strand height is dependent on strand length (15-35 base pairs) and medium.
- In air, longer DNA strands lie flat; in liquid, they stand up due to charge repulsion.
Conclusions:
- AFM height and force modes offer complementary data for characterizing DNA films.
- Environmental factors significantly alter DNA film conformation and thickness.
- Force analysis is essential for interpreting AFM height images in liquid environments.