Instantaneous Attachment
of an Ultrahigh Density of
Nonthiolated DNA to Gold Nanoparticles and Its Applications
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Abstract
The last 16 years have witnessed the landmark development
of polyvalent
thiolated DNA-functionalized gold nanoparticles (AuNP's) possessing
striking properties within the emerging field of nanobiotechnology.
Many novel properties of this hybrid nanomaterial are attributed to
the dense DNA shell. However, the question of whether nonthiolated
polyvalent DNA–AuNP could be fabricated with a high DNA density
and properties similar to those of its thiolated counterpart has not
been explored in detail. Herein, we report that by simply tuning the
pH of the DNA–AuNP mixture an ultrahigh capacity of nonthiolated
DNA can be conjugated to AuNP's in a few minutes, resulting in polyvalent
DNA–AuNP conjugates with cooperative melting behavior, a typical
property of polyvalent thiolated DNA-functionalized AuNP's. With this
method, large AuNP's (e.g., 50 nm) can be functionalized to achieve
the colorimetric detection of sub-nanometer DNA. Furthermore, this
fast, stable DNA loading was employed to separate AuNP's of different
sizes. We propose that a large fraction of the attached DNAs are adsorbed
via one or a few terminal bases to afford the high loading capacity
and the ability to hybridize with the complementary DNA. This discovery
not only offers a time- and cost-effective way to functionalize AuNP's
with a high density of nonthiolated DNA but also provides new insights
into the fundamental understanding of how DNA strands with different
sequences interact with AuNP's