Tracking Gold Nanorods’ Interaction with Large 3D Pancreatic-Stromal Tumor Spheroids by Multimodal Imaging: Fluorescence, Photoacoustic, and Photothermal Microscopies

Abstract

pancreatic cancer is one of the most complex types of cancers to detect, diagnose, and treat. However, the field of nanomedicine has strong potential to address such challenges. When evaluating the diffusion and penetration of theranostic nanoparticles, the extracellular matrix (ECM) is of crucial importance because it acts as a barrier to the tumor microenvironment. in the present study, the penetration of functionalized, fluorescent gold nanorods into large (>500 μm) multicellular 3D tissue spheroids was studied using a multimodal imaging approach. the spheroids were generated by coculturing pancreatic cancer cells and pancreatic stellate cells in multiple ratios to mimic variable tumor-stromal compositions and to investigate nanoparticle penetration. fluorescence live imaging, photothermal, and photoacoustic analysis were utilized to examine nanoparticle behavior in the spheroids. Uniquely, the nanorods are intrinsically photoacoustic and photothermal, enabling multiimaging detection even when fluorescence tracking is not possible or ideal. Nanomedicine for cancer treatments-the use of nanosized structures in cancer therapeutics and/or imaginghas been heavily investigated over the last two decades 1. Nano-sized delivery systems are useful theragnostic agents for enhanced tumor penetration, accumulation, and targeting potency. Studies of nanoparticle (NP)-based therapies have mainly focused on targeted cancer cell treatment but also include cancer stem cells 2 , stromal cancer microenvironment 3-5 , and/or cellular immune system 6,7. As a physical barrier that limits NP penetration and distribution, the extracellular matrix (ECM) is a crucial concern when evaluating the effects of nanoscale cancer therapies. Recent work showed that the ECM can be regulated by using gold NPs to interrupt the crosstalk between cancer cells and stellate cells, which reeducates the stellate cells 8,9. However, the development of nanosystems for cancer treatment has been hampered by the limitations of current in vitro models, which are generally based on two-dimensional (2D) cell cultures. These 2D models struggle to provide an accurate representation of the in vivo environment and its components, which include the dynamic tumor microenvironment (TME), cell heterogeneity, and nutrient and pH gradient interaction between cells and the ECM 10. The real TME is composed not only of cancer cells but also of others cells such as fibroblasts, cancer-associated fibroblasts (CAFs), stromal cells, myofibroblasts, endothelial cells, adipocytes, various immune cells, and extra-abundant compromised ECM. These heterocellular components can induce adaptive survival mechanisms of cancer such as treatment resistance, a leading cause of cancer-related mortality and one of the greatest challenges in cancer treatment 11. The cellular responses and cell signaling that take place in the TME often cannot be mimicked in a 2D in vitro model.

Three-Dimensional Spheroids as In Vitro Preclinical Models for Cancer Research

“…↓ For larger spheroids, processing for histological sectioning is required-spheroid fixation used in the histological procedure precludes the study of dynamic alterations in the spheroids over time. [144,145,158,[163][164][165][166][167] Fibronectin, laminin, and collagen IV staining. ECM deposition.…”

An On-Demand pH-Sensitive Nanocluster for Cancer Treatment by Combining Photothermal Therapy and Chemotherapy

“…Compared with DOX or AuNR with or without light, NC 2 with 808 nm laser irradiation obviously showed superior tumor growth inhibition ( Figure S3). With the laser ablation by PTT, NC 2 could overcome the barrier and penetrate into tumor tissue with a three-dimensional (3D) structure [67][68][69]. It would enable significant tumor growth inhibition by pH-dependent drug release at the intracellular compartment.…”

Diattenuation and Retardance Signature of Plasmonic Gold Nanorods in Turbid Media Revealed by Mueller Matrix Polarimetry

“…Gold nanoparticles (GNPs) exhibit strong localized SPR effect and have thus been actively explored in biology and medicine [5][6][7]. Their strong confinement of EM waves and biocompatibility has spurred their use as multifunctional probes for molecular rulers [13], single molecule detection [14], photoactive drug delivery [15], photodynamic therapy [16], photothermal treatments [17], stem cells targeting [18], tumour and stromal microenvironment imaging [19], and optical contrast enhancement [20]. In this context, plasmonic gold nanospheres have not proven particularly useful because their plasmon resonance effects occur at shorter wavelengths, which owing to basic tissue optics limits their biomedical use.…”

“…However, plasmonic gold nanorods (GNRs) have been found to be more useful due to their geometry and aspect ratio dependent tunable plasmon mode which falls within the visible and near infrared spectral regime suitable for biomedical imaging [5][6][7]. Several studies have therefore focused on GNR delivery mechanism, their interaction with biological media, and their photoactivity [14][15][16][17][18][19][20].…”