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Tunable loading of oligonucleotides with secondary structure on gold nanoparticles through a pH-driven method
Duncan Hieu M Dam1, Hyojin Lee, Raymond C Lee
1Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , 2145 Sheridan Road, Evanston Illinois 60208, United States.
Bioconjugate Chemistry
|January 8, 2015
Summary
Controlling pH enables precise covalent attachment of oligonucleotides onto gold nanoparticles (AuNPs). Lower pH maximizes nucleic acid loading, with secondary structure influencing packing density and maintaining aptamer function.
Area of Science:
- Nanotechnology
- Biochemistry
- Materials Science
Background:
- Gold nanoparticles (AuNPs) are widely used in biosensing and drug delivery.
- Controlling the surface chemistry of AuNPs is crucial for their applications.
- Oligonucleotides with secondary structures offer unique functionalities but their attachment can be challenging.
Purpose of the Study:
- To investigate the effect of pH on the covalent attachment of oligonucleotides with secondary structures onto gold nanoparticles.
- To understand how pH influences loading density and oligonucleotide packing.
- To assess the impact of pH-induced structural changes on aptamer functionality.
Main Methods:
- Covalent attachment of thiolated oligonucleotides to gold nanoparticles.
- pH-dependent loading studies.
- Circular dichroism spectroscopy to analyze oligonucleotide secondary structure.
- Assessment of biological activity of aptamer-loaded nanoparticles.
Main Results:
- Highest loading of thiolated nucleic acids on AuNPs achieved at low pH (1.7) due to reduced electrostatic repulsion.
- Oligonucleotide packing density decreased with increasing secondary structure complexity (single-stranded > duplex > quadruplex) at low pH.
- Loading density was dependent on oligonucleotide flexibility and secondary structure organization across all pH conditions.
- G-quadruplex aptamers showed pH-dependent structural transitions but retained biological activity.
Conclusions:
- pH is a critical parameter for controlling the quantitative loading of oligonucleotides onto gold nanoparticles.
- The findings enable tailored surface functionalization of AuNPs with diverse oligonucleotide structures.
- This pH-tuning approach is applicable to various AuNP types and surface modifications for advanced nanomaterial design.
