Surface-enhanced Raman scattering (SERS) provides a non-destructive sensing method with high sensitivity and multiplex detection capability since SERS takes advantage of high enhancement from surface plasmon resonance and unique “fingerprint” spectral signature using Raman spectroscopy. Our group has developed a unique plasmonics-active nanoparticle, gold nanostars, with tunable plasmonics in near-infrared (NIR) “tissue optical window” without using toxic surfactant. We present their applications for chemical and biological sensing with SERS method as well as theoretical studies to investigate and confirm experimentally measured SERS results.
Cancer has become one of most significant death reasons and causes approximately 7.9 million human deaths worldwide each year. The challenge to detect cancer at an early stage makes cancer-related biomarkers sensing attract more and more research interest and efforts. Surface-enhanced Raman scattering (SERS) provides a promising method for various biomarkers (DNA, RNA, protein, et al.) detection due to its high sensitivity, specificity and capability for multiple analytes detection. Raman spectroscopy is a non-destructive photon-scattering technique, which provides molecule-specific information on molecular vibrational energy levels. SERS takes advantage of plasmonic effects and can enhance Raman signal up to 1015 at “hot spots”. Due to its excellent sensitivity, SERS has been capable of achieving single-molecule detection limit. Local pH environment has been identified to be a potential biomarker for cancer diagnosis since solid cancer contains highly acidic environments. A near-infrared (NIR) SERS nanoprobe based on gold nanostars for pH sensing is developed for future cancer detection. Near-infrared (NIR) light is more suitable for in vivo applications because of its low attenuation rate and tissue auto fluorescence. SERS spectrum of pH reporter under various pH environments is monitored and used for pH sensing. Furthermore, density functional theory (DFT) calculation is performed to investigate Raman spectra changes with pH at the molecular level. The study demonstrates that SERS is a sensitive tool to monitor minor molecular structural changes due to local pH environment for cancer detection.
Nanotechnology provides tremendous biomedical opportunities for cancer diagnosis, imaging, and therapy. In contrast to
conventional chemotherapeutic agents where their actual target delivery cannot be easily imaged, integrating imaging
and therapeutic properties into one platform facilitates the understanding of pharmacokinetic profiles, and enables
monitoring of the therapeutic process in each individual. Such a concept dubbed “theranostics” potentiates translational
research and improves precision medicine. One particular challenging application of theranostics involves imaging and
controlled delivery of nanoplatforms across blood-brain-barrier (BBB) into brain tissues. Typically, the BBB hinders
paracellular flux of drug molecules into brain parenchyma. BBB disrupting agents (e.g. mannitol, focused ultrasound),
however, suffer from poor spatial confinement. It has been a challenge to design a nanoplatform not only acts as a
contrast agent but also improves the BBB permeation. In this study, we demonstrated the feasibility of plasmonic gold
nanoparticles as both high-resolution optical contrast agent and focalized tumor BBB permeation-inducing agent. We
specifically examined the microscopic distribution of nanoparticles in tumor brain animal models. We observed that
most nanoparticles accumulated at the tumor periphery or perivascular spaces. Nanoparticles were present in both
endothelial cells and interstitial matrices. This study also demonstrated a novel photothermal-induced BBB permeation.
Fine-tuning the irradiating energy induced gentle disruption of the vascular integrity, causing short-term extravasation of
nanomaterials but without hemorrhage. We conclude that our gold nanoparticles are a powerful biocompatible contrast
agent capable of inducing focal BBB permeation, and therefore envision a strong potential of plasmonic gold
nanoparticle in future brain tumor imaging and therapy.
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