DNA Sequence Mediates Apparent Length Distribution in Single-Walled Carbon Nanotubes

Area of Science:

• Biomaterials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Single-walled carbon nanotubes (SWCNTs) functionalized with DNA are promising for biomedical applications.
• Accurate characterization of SWCNT physical properties, like length, is crucial for their use as research tools and diagnostic agents.
• Conventional atomic force microscopy (AFM) length measurements of DNA-SWCNTs can be inaccurate due to deposition biases.

Purpose of the Study:

• To investigate the impact of DNA sequence and deposition methods on the measured length distribution of DNA-SWCNTs.
• To develop a more accurate method for quantifying SWCNT length distributions.
• To understand the relationship between DNA density and SWCNT length.

Main Methods:

• Utilized a solution-based surfactant exchange technique to uniformly wrap DNA-SWCNTs.
• Employed spin-coating to deposit surfactant-wrapped SWCNTs, minimizing electrostatic interactions.
• Quantified DNA coverage on SWCNTs using absorbance spectroscopy and direct observation.

Main Results:

• Differential deposition of DNA-SWCNTs with varying DNA sequences on AFM substrates led to inaccurate length distributions.
• The surfactant exchange and spin-coating method yielded identical SWCNT length distributions, independent of DNA sequence.
• Surface deposition methods exhibited inherent bias, reporting significantly shorter lengths compared to the spin-coating method.
• DNA density per SWCNT varied with SWCNT length for short DNA sequences ((GT)6), but not for longer sequences ((GT)30).

Conclusions:

• Electrostatic interactions during surface deposition significantly bias the measured length distributions of DNA-SWCNTs.
• A surfactant-based solution method followed by spin-coating provides a more accurate determination of intrinsic SWCNT length distributions.
• Sequence-dependent DNA density influences electrostatic repulsion and affects measurement accuracy.