Plasmonic gap-enhanced Raman tag nanorods for imaging 3D pancreatic spheroids using surface-enhanced Raman spectroscopy and darkfield microscopy

Abstract

Plasmonic gap-enhanced Raman tags (GERTs) are new emerging nanoprobes that, based on their unique surface-enhanced Raman spectroscopy (SERS) signal, can play a major role in complex imaging and detection of biological systems. GERTs are generated from a metal core nanostructure and layered with one or more metal nanosized layers, encasing a Raman active molecule. The advantages of GERTs are enhanced surface plasmon and electromagnetic resonance, as well as inherent protection of the Raman active molecule from environmental deterioration that could reduce their spectroscopic signatures over time. In this study, we used in vitro three-dimensional (3D) spheroid cultures to demonstrate these advantages. 3D spheroids mimic the in vivo tumor microenvironment better than 2D culture, with abundant extracellular matrix and hypoxia inducing variability of pH and enzymatic reactions. Here, we report the use of GERTs in large pancreatic 3D spheroids (>500 μm in apparent diameter) for complex penetration visualization. Our combined imaging technique of enhanced darkfield microscopy and SERS was able to identify the presence and distribution of the GERTs within the 3D spheroid structure. The distribution of GERTs 2 hours after the nanorods’ incubation indicated accumulation, generally in the outermost layer of the spheroids but also, more randomly, in non-uniform patterns in deep layers of the 3D spheroids. These observations bring into question the mechanism of uptake and flow of the nanoparticles in function of their incubation time while demonstrating the promising potential of our approach. Additionally, the SERS signal was still detectable after 24 hours of incubation of GERTs with the 3D culture, indicating the stability of the Raman signal.

Biobanked Glioblastoma Patient-Derived Organoids as a Precision Medicine Model to Study Inhibition of Invasion

“…Advancements in cell culture techniques have seen the rapid evolution of more complex in vitro cell culture models that include three-dimensional (3D) multicellular spheroids, organoids, bio-printing, and organ-on-a-chip models. These models have been shown to have improved characteristics in comparison to 2D models which include abundant extracellular matrix (ECM), cell heterogeneity and signaling variation; hypoxic, nutrition, and pH gradients; and higher therapeutic resistance and mutations similar to the parent tumor, which thus make them more suitable for cancer therapy research [ 10 , 11 , 12 , 13 , 14 ].…”

Tumor Phantom with Incorporated SERS Tags: Detectability in a Turbid Medium

“…To overcome these difficulties, the rational design of plasmonic nanoparticles for higher SERS response is an active area of research. Many types of plasmonic nanoparticles have already been reported as labels for in vivo tumor bioimaging including colloidal gold [10,11], nanorods [12], nanostars [13], gap-enhanced Raman tags [14][15][16] and others [8,17]. Recently, a novel type of nanoparticle called petal-like gap-enhanced Raman tags [18] have been suggested as ultrabright labels that can overcome the current bottleneck in the field of SERS-based bioimaging.…”