Plasmonic Nanoplatforms for Sensing, Diagnostics, and Therapy

Recent advances in nanotechnology have led to the application of nanoparticles in a wide variety of fields. In particular, anisotropic nanoparticles have shown great potential for surface-enhanced Raman scattering (SERS) detection due to their unique optical properties. Gold nanostars are a type of anisotropic nanoparticle with one of the highest SERS enhancement factors in a non-aggregated state. By utilizing the distinct characteristics of gold nanostars, new plasmonic materials for sensing, diagnostics, and therapy can be synthesized. The work described herein is divided into two main themes. The first half demonstrates the development and application of a novel label-free inverse molecular sentinel (iMS) nanoprobe for detection of microRNA biomarkers related to cancer progression as well as those related to gene expression in plants. This work also describes the initial proof-of-concept for a SERS-based electrowetting-on-dielectric (EWD) digital microfluidic platform as a diagnostic platform requiring samples of nanoliter volume. The second half demonstrates the utility of plasmonic nanoparticles for SERS imaging as well as photothermal therapy (PTT) and photodynamic therapy (PDT).

Development of accessible strategies for efficient detection of nucleic acid biomarkers is a major unmet need for applications ranging from cancer screening to agricultural biotechnology and biofuel development. MicroRNAs (miRNAs) have great promise as a new important class of biomarkers for early detection of various cancers; however, these small molecules have not been adopted into early diagnostics for clinical practice because of challenges adapting complex laboratory techniques into accessible clinical tests. In a blinded study, the surface-enhanced Raman scattering (SERS)-based plasmonics-active nanoprobes described herein, referred to as inverse molecular sentinels (iMS), demonstrated diagnostic accuracy for in vitro identification of endoscopic biopsy samples as tumor, Barrett’s esophagus or normal tissue via miRNA detection. The iMS nanoprobe technology can be designed to detect a wide range of nucleic acids for a variety of applications. In addition to medical applications, the knowledge over gene expression dynamics and location in plants is crucial for applications ranging from basic biological research to agricultural biotechnology. However, current methods are unable to provide in vivo dynamic detection of genomic targets in plants, due to the complex sample preparation needed by current methods for nucleic acids detection, which disrupt spatial and temporal resolution. We have developed a multimodal technique utilizing iMS nanoprobes for in vivo imaging and biosensing of microRNA biotargets within whole plants. This work lays the foundations for in vivo functional imaging of RNA biotargets in plants with previously unmet spatial and temporal resolution.

The prevalence of cancer has increasingly become a significant threat to human health and as such, there exists a strong need for developing novel methods for early detection and effective therapy. Gold nanostars (AuNS) with tip-enhanced plasmonics have become one of the most promising platforms in photothermal therapy (PTT) as they exhibit superior photon-to-heat conversion efficiency and can be delivered specifically to tumors. We have demonstrated that AuNS are endocytosed into multiple cancer cell lines irrespective of receptor status or drug resistance and allow for the effective photothermal ablation of tumor cells. Additionally, we demonstrate a unique in vitro preclinical model that mimics the tumor structures assumed by inflammatory breast cancer (IBC) in vivo. IBC has a unique presentation of diffuse tumor cell clusters called tumor emboli. AuNS are able to penetrate the tumor embolic core in 3D culture, allowing effective photothermal ablation of the IBC tumor emboli.

Additionally, we have furthered the development of the gold nanostar treatment platform by developing a theranostic nanoconstruct that consist of Raman-labeled gold nanostars coated with a silica shell that is loaded with photosensitizer molecules for PDT. The outer surface of the nanoconstruct was functionalized for targeting to allow for specific treatment of folate positive breast cancer. SERS detection and PDT are performed at different wavelengths, so there is no interference between the diagnostic and therapeutic modalities. Singlet oxygen generation (a measure of PDT effectiveness) was demonstrated from the drug-loaded nanocomposites. In vitro testing demonstrated the effectiveness of the nanoconstruct for targeted PDT.