posted on 2022-01-04, 17:36authored byDavid
A. Hastman, Parth Chaturvedi, Eunkeu Oh, Joseph S. Melinger, Igor L. Medintz, Lela Vuković, Sebastián A. Díaz
There
is significant interest in developing photothermal systems
that can precisely control the structure and function of biomolecules
through local temperature modulation. One specific application is
the denaturation of double-stranded (ds) DNA through femtosecond (fs)
laser pulse optical heating of gold nanoparticles (AuNPs); however,
the mechanism of DNA melting in these systems is not fully understood.
Here, we utilize 55 nm AuNPs with surface-tethered dsDNA, which are
locally heated using fs laser pulses to induce DNA melting. By varying
the dsDNA distance from the AuNP surface and the laser pulse energy
fluence, this system is used to study how the nanosecond duration
temperature increase and the steep temperature gradient around the
AuNP affect dsDNA dehybridization. Through modifying the distance
between the dsDNA and AuNP surface by 3.8 nm in total and the pulse
energy fluence from 7.1 to 14.1 J/m2, the dehybridization
rates ranged from 0.002 to 0.05 DNA per pulse, and the total amount
of DNA released into solution was controlled over a range of 26–93%
in only 100 s of irradiation. By shifting the dsDNA position as little
as ∼1.1 nm, the average dsDNA dehybridization rate is altered
up to 30 ± 2%, providing a high level of control over DNA melting
and release. By comparing the theoretical temperature around the dsDNA
to the experimentally derived temperature, we find that maximum or
peak temperatures have a greater influence on the dehybridization
rate when the dsDNA is closer to the AuNP surface and when lower laser
pulse fluences are used. Furthermore, molecular dynamics simulations
mimicking the photothermal heat pulse around a AuNP provide mechanistic
insight into the stochastic nature of dehybridization and demonstrate
increased base pair separation near the AuNP surface during laser
pulse heating when compared to steady-state heating. Understanding
how biological materials respond to the short-lived and non-uniform
temperature increases innate to fs laser pulse optical heating of
AuNPs is critical to improving the functionality and precision of
this technique so that it may be implemented into more complex biological
systems.