Abstract
Surface enhanced Raman scattering (SERS) nanoparticles are an attractive alternative to fluorescent probes for biological labeling because of their photostability and multiplexing capabilities. However, nanoparticle size, shape, and surface properties are known to affect nanoparticle-cell interactions. Other issues such as the formation of a protein corona and antibody multivalency interfere with the labeling properties of nanoparticle-antibody conjugates. Hence, it is important to consider these aspects in order to validate such conjugates for live cell imaging applications. Using SERS nanoparticles that target HER2 and CD44 in breast cancer cells, we demonstrate labeling of fixed cells with high specificity that correlates well with fluorescent labels. However, when labeling live cells to monitor surface biomarker expression and dynamics, the nanoparticles are rapidly uptaken by the cells and become compartmentalized into different cellular regions. This behavior is in stark contrast to that of fluorescent antibody conjugates. This study highlights the impact of nanoparticle internalization and trafficking on the ability to use SERS nanoparticle-antibody conjugates to monitor cell dynamics.
Highlights
Therapy resistance as well as recurrence and metastasis are believed to be caused by a select group of cancer cells called cancer stem cells (CSCs) with significant ability to self-renew
The original goal of this study was to take advantage of the non-photobleaching and multiplexing capabilities of surface enhanced Raman scattering (SERS) NPs to quantify the distribution of specific cell surface biomarkers (i.e., HER2 and CD44) and their dynamic distributions during cell cycle progression inherited from parent to daughter cells, as well as newly expressed proteins, to better characterize biomarker profiles during breast CSC proliferation (Fig. 1)
The TEM results are confirmed with dynamic light scattering (DLS) measurements (Supplementary Fig. S1E) that indicate the NPs have a diameter distribution ranging from 100 to 400 nm
Summary
Therapy resistance as well as recurrence and metastasis are believed to be caused by a select group of cancer cells called cancer stem cells (CSCs) with significant ability to self-renew. Surface enhanced Raman scattering (SERS) NPs have been extensively used to image fixed[4,5,6,7,8,9], and live[10,11,12,13,14,15,16] cells From these studies, it is evident that SERS NPs provide clear advantages over fluorescence labeling in two important aspects: multiplexing and photostability[17]. The study presented here demonstrates that despite their known and appealing advantages, SERS NPs are not optimal for most live-cell imaging applications, such as monitoring dynamics of surface markers, due to NP internalization and trafficking by cells. Challenges and requirements for implementing SERS NPs in cell imaging and sensing applications are discussed
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