Synthesis of Stable Peptide Nucleic Acid-Modified Gold Nanoparticles and their Assembly onto Gold Surfaces

摘要

DNA-based gold-nanoparticle (AuNP) systems are currently employed in a growing range of applications, which include gene regulation, nanofabrication, sensing, and plasmonic rulers. However, a disadvantage of the assembly of DNA-modified NPs is the need for salt to keep their assemblies stable. Halogens are known to damage silver nanoparticles (AgNPs), while the addition of salt in general destabilizes colloidal particles. Additionally, the presence of substantial amounts of ions is problematic for the study and use of physical phenomena that rely on electrostatics. Thus, the functionalization of nanoparticles with the non-natural DNA analogue peptide nucleic acid (PNA), instead of DNA, is extremely attractive. PNA has many advantages over DNA including a higher stability against biodegradation, greater mismatch sensitivity, and higher binding efficiency to PNA, DNA, and RNA. Hence, shorter oligonucleotide strands could potentially be used for the assembly of PNA-function-alized AuNPs compared to those required for stable DNA-based assembly. An increase in the resolution control of close-packed gold nanoparticles could therefore be observed. Additionally, the stability of PNA-DNA and PNA-PNA hybrids is independent of the ionic strength of the medium.1'1 In comparison, DNA alone is not able to form assemblies under ion-free conditions as the electrostatic repulsion between the negatively charged strands is too high. Therefore, AuNP assemblies relying on PNA hybridization could be formed without the addition of salt, unlike DNA-AuNP hybrids. Despite the huge potential of PNA-based AuNPs, there are only a few articles reporting the direct attachment of PNA onto AuNPs.