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Nano and Micro Technologies

Synthesis of Raman-active Core-Shell Nanoparticle Probes for Early Detection of Ovarian Cancer

(J-377) Synthesis of Raman-active Core-Shell Nanoparticle Probes for Early Detection of Ovarian Cancer

Friday, October 13, 2023

9:30 AM – 10:30 AM PDT

Location: Exhibit Hall - Row J - Poster # 377

Presenting Author(s)

Anna V. Kolesov (she/her/hers)

Undergraduate Researcher
University of California, Davis
Pacific Grove, California, United States

Co-Author(s)

QH

Qing He

Postdoctoral Researcher
University of California, Davis, United States
HO

Hannah O'Toole

Graduate Student Researcher
University of California, Davis
Davis, California, United States

Primary Investigator(s)

RC

Randy Carney (he/him/his)

Associate Professor
University of California Davis, United States

Introduction:: The 5-year survival rate for ovarian cancer drastically improves to 94% when diagnosed early-stage, compared to only 31% when diagnosed late-stage. Unfortunately, only about 20% of cases are detected early-stage due to lack of defining symptoms or non-detection with pelvic exams. Therefore, there is a clear clinical need for a sensitive and non-invasive ovarian cancer diagnostic platform to improve early-stage detection. We aim to create a nanomaterial probe that specifically detects cancer-associated-extracellular vesicles (EVs) in patient samples with readout by surface enhanced Raman spectroscopy (SERS). The nanomaterial probe is a core-shell silica and gold nano-matryoshka, with specific labels to tag EVs. The gold nanoparticle (AuNP) core provides plasmonic enhancement enabling SERS, akin to shining a bright light on the cancer biomarkers. A self-assembled monolayer of a Raman-active tag (RT) surrounds the core to act as a unique label for each nanoparticle type. A silica shell encases the Raman-tag to the nanoparticle, providing long term particle stability and an adhesive surface for EV targeting agents. Each nanoparticle formulation has a direct association between a Raman-active tag and an EV targeting agent, therefore linking the peaks of the outputted Raman spectra to cancer associated proteins (Figure 1A). Dozens of unique types of Raman-active nanoparticles can be synthesized and simultaneously used to analyze one sample with only one laser. This superplexing ability is advantageous to fluorescent tags, which are limited to simultaneous analysis of only a handful of tags. In this work, we demonstrate synthesis and characterization of four lead nanoprobe SiO₂@RT@AuNPs.

Materials and Methods:: Monodisperse PVP-coated 50 nm spherical AuNPs were purchased from NanoComposix. The AuNPs were incubated with one of four 10 mM Raman tag solutions to form the Raman-active coating. Tags used were 4-mercaptobenzoic acid (MBA), 2-mercapto-4-methyl-5-thiazoleacetic acid (MMTAA), 7-mercapto-4-methylcoumarin (MMC), and a new alkyne-based tag. Raman spectroscopy (Figure 1A) and transmission electron microscopy (TEM) (Figure 1B) were used to validate Raman-tag adhesion to the AuNP surface. A modified Stöber process was used for silica encapsulation of the Raman-active nanospheres. First, NPs were incubated in an APTMS solution for 10 min. After centrifugation, nanospheres were redispersed in an isopropanol, water, and ammonium hydroxide solution. A 1% TEOS solution was added, followed by ultrasonication for 30 min at 60℃. Two rounds of TEOS addition were performed and the solution was left at room temperature overnight. TEM was used to observe the morphology of the silica shell and Raman spectroscopy was used to spectrally validate the presence of Raman-tag on the nanosphere surface. ImageJ was used to measure the thickness of the silica shell.

Results, Conclusions, and Discussions::

Results and Discussion: Optimized synthetic procedures have been developed for four types of Raman-active tags. It was determined that the thickness of the silica shell can be adjusted by changing the volume of added 1% TEOS solution. For example, a 10, 20, and 30 μL TEOS solution addition produced an average silica shell thickness of 3.5 nm, 8.3 nm, and 12.6 nm, respectively, for 4-MBA. The optimal silica shell thickness is between 5-10 nm as it provides particle stability and does not dampen the Raman-tag signal. The optimal 8.3 nm silica shell thickness is shown in Figure 1B. The Raman spectral peaks of the RTs correspond to those reported in literature. The MBA tagged nanoparticles showed the characteristic wave peaks at 1084 cm-1 and 1586 cm-1 (Figure 1C).

Conclusion: Four types of silica encapsulated Raman-active nanoparticles have been synthesized. Further research is being conducted to expand the number of different types of nanoparticles and produce an antibody conjugation procedure for subsequent testing with ovarian cancer-associated EVs. This proof-of-concept work provides a promising nanomaterial probe for early-stage ovarian cancer detection.

Acknowledgements (Optional): : I would like to acknowledge Qing He, my mentor Hannah O'Toole, my PI Randy Carney, and all of the members of the Carney Lab for the constant guidance and support on this project.

References (Optional): :