Plasmonic nanoparticles are increasingly
utilized in biomedical
applications including imaging, diagnostics, drug delivery, and plasmonic
photothermal therapy (PPT). PPT involves the rapid conversion of light
into heat by plasmonic nanoparticles targeted to a tumor, causing
hyperthermia-induced cell death. These nanoparticles can be passively
targeted utilizing the enhanced permeability and retention effect,
or actively targeted using proteins, peptides, or other small molecules.
Here, we report the use of actively targeted spherical gold nanoparticles
(AuNPs), both to induce PPT cell death, and to monitor the associated
molecular changes through time-dependent surface enhanced Raman spectroscopy
within a single cell. We monitored these changes in real-time and
found that heat generated from the aggregated nanoparticles absorbing
near-infrared (NIR) laser light of sufficient powers caused modifications
in the protein and lipid structures within the cell and ultimately
led to cell death. The same molecular changes were observed using
different nanoparticle sizes and laser intensities, indicating the
consistency of the molecular changes throughout PPT-induced cell death
from actively targeted AuNPs. We also confirmed these observations
by comparing them to reference spectra obtained by cell death induced
by oven heating at 100 °C. The ability to monitor PPT-induced
cell death in real-time will help understand the changes on a molecular
level and offers us a basis to understand the molecular mechanisms
involved in photothermal cancer cell death
