From 2D to 3D Cancer Cell Models—The Enigmas of Drug Delivery Research

Abstract

Over the past decades, research has made impressive breakthroughs towards drug delivery systems, resulting in a wide range of multifunctional engineered nanoparticles with biomedical applications such as cancer therapy. Despite these significant advances, well-designed nanoparticles rarely reach the clinical stage. Promising results obtained in standard 2D cell culture systems often turn into disappointing outcomes in in vivo models. Although the overall majority of in vitro nanoparticle research is still performed on 2D monolayer cultures, more and more researchers started acknowledging the importance of using 3D cell culture systems, as better models for mimicking the in vivo tumor physiology. In this review, we provide a comprehensive overview of the 3D cancer cell models currently available. We highlight their potential as a platform for drug delivery studies and pinpoint the challenges associated with their use. We discuss in which way each 3D model mimics the in vivo tumor physiology, how they can or have been used in nanomedicine research and to what extent the results obtained so far affect the progress of nanomedicine development. It is of note that the global scientific output associated with 3D models is limited, showing that the use of these systems in nanomedicine investigation is still highly challenging.

Effect of stroma on the behavior of temoporfin-loaded lipid nanovesicles inside the stroma-rich head and neck carcinoma spheroids

“…These data are consistent with the recent report, where the authors demonstrated the concentration-depended penetration of doxorubicin in spheroids [ 21 ]. Visually, there was no difference in penetration depth in stroma-rich spheroids, despite the general consideration of ECM as a physical barrier for NPs [ 5 , 22 , 23 ]. However, it is rather difficult to distinguish the differences between mono-and co-culture spheroids without the quantification analysis.…”

“…Concerning the mTHPC NPs, to date, only a limited number of NPs [ 10 ], preferably cyclodextrin-based [ 15 , 16 , 24 , 25 ], demonstrated the deep penetration in 3D cancer models. There is increasing evidence indicating that the physicochemical properties of NPs, such as size, charge, and surface chemistry, play a crucial role in their ability to penetrate ECM [ 5 , 6 , 26 ]. NPs tested in this study possess close physicochemical characteristics, ca.…”

“…100–200 nm, negative charge up to – 38 mV [ 15 , 18 ], allowing comparison of their behavior in 3D tumor spheroids. Based on theoretical models, the size and surface properties (e.g., charge and morphology) of NPs are considered to be crucial for penetration into solid tumors [ 5 , 27 – 29 ]. For instance, small (< 60 nm) and neutral (± 10 mV) NPs are preferred for deep penetration into the dense positively charged collagen matrix [ 22 , 23 ].…”

“…Much of the justification for the use of NPs is based on the enhanced permeability and retention effect, which proposes NPs preferable accumulation in tumors due to a leaky vasculature and suppresses lymphatic drainage [ 4 ]. Commonly, cellular interactions of the developed nanomaterials are assessed in 2D culture monolayers in vitro , which lack critical stroma components of the tumor microenvironment (TME) [ 5 ]. Thus, there is a need to develop a better understanding of how stroma components affect the delivery of NPs into the tumors.…”

“…3D in vitro tumor models (i.e., multilayers, spheroids, microtissues) recapitulate several aspects of TME, providing better predictive results, and facilitating clinical translation [ 6 ]. Most of 3D in vitro tumor models are focusing only on tumor cells, missing stroma components, e.g., extracellular matrix (ECM) [ 6 ], which are considered as a physical barrier for NPs penetration into the tumors [ 5 , 7 ]. Recently, we reported the optimization of sophisticated 3D co-culture tumor spheroids consisting of head and neck squamous carcinoma cells (HNSCC) and cancer-associated fibroblasts (CAFs), capable of recapitulating various levels of ECM expression in the HNSCC [ 8 ].…”