Background

The advancement of the nanotechnology field has enabled the exploitation of nanoparticle (NP)-based cancer therapies (Jain and Stylianopoulos, 2010; Shi et al., 2017). Compared to the standard chemotherapeutic approach, NPs confer several advantages as they improve drug solubility and stability, prolong drug half-lives in plasma, minimize off-target effects, and concentrate drugs at the target site (Mudshinge et al., 2011). Combining all these characteristics, some NPs have been successfully approved by the FDA or are currently in clinical trials (Dinndorf et al., 2007; Ediriwickrema and Saltzman, 2015). Despite these achievements, several details have to be considered in novel nanoparticle formulations, as most NP-based drugs have failed to improve patient outcomes. One of the most important is the relation of NPs with the tumor microenvironment (TME), which includes tumor cells, immune cells, and blood vessels (Blank et al., 2017).

Traditionally, the characterization of the cellular uptake and interaction of NPs in the TME has been evaluated by 2D tissue sections. Despite the nanoscale resolution, immunohistochemistry and histology fail to demonstrate the complex organization of biological specimens and only provide static snapshots of events. With the development of new volumetric microscopy techniques, the understanding of cell-cell interactions in intact samples has become clearer. Furthermore, in comparison with other live-cell or in vivo technologies, confocal microscopy enables real-time imaging from general tissue architecture at nanoscale resolution (Ramos-Gomes et al., 2020).

Recently, we published a protocol for live high-resolution imaging of the interaction between monocytes and tumor cells with nanoparticles in the mouse lung (Ramos-Gomes et al., 2020). Here, we were able to demonstrate the dynamics between tumor and immune cells, the reaction of the macrophages/monocytes towards NPs, and characterize the NP deposition in the tumor. This approach opens new avenues to dynamically understand how nanotherapies are going to affect the TME and reach target sites.