To summarize, at the completion of the 117PD/2020 project, two 3D in vitro culture models of HT-29 colorectal adenocarcinoma tumor cells were developed: 3D multicellular tumor spheroids (MCTS) and organ-on-a-chip systems, both models presenting advantages compared to 2D cell cultures through which these models mimic the characteristics of tumors in vivo much better and thus represent much more realistic platforms for the screening of drug-delivery systems. Furthermore, the optimized protocol for culturing HT-29 cells in organ-on-a-chip systems was optimized to transition the platform to accommodate 2 cell types to simulate the presence of the endothelial barrier. All these models served to test the cytotoxicity of polymeric drug-delivery systems loaded with 5-FU, and the results obtained showed that the dose required to obtain the same cytotoxic effect is higher in the organ-on-a-chip systems, the cells being more resistant to therapy when grown in this system. Regarding the intimate molecular mechanism of action of the drug-delivery systems loaded with 5-FU, it is based on the induction of apoptosis in both culture models, a much stronger pronounced effect being observed in the organ-on-a-chip systems. Furthermore, in the presence of the endothelial barrier, the cytotoxic effect of the same treatment concentration is much weaker, and a higher concentration of treatment is required to achieve a similar cytotoxic effect.
The obtained results present significant progress in the field of oncology research, presenting the development and validation of a dynamic platform based on organ-on-a-chip microfluidic technology with applicability as a screening tool for drug-delivery systems. Thus, the implementation of these platforms in the screening of drug-delivery systems can lead to obtaining much more realistic in vitro results and thus reduce the risk of failure of new treatments developed during in vivo studies or clinical trials. Moreover, the implementation of the in vitro model with endothelial barrier allows the precise adjustment of the nanosystems administration dose to achieve an effective antitumor effect and also allows the optimization of the physicochemical parameters of the synthesized nanosystems (e.g. size) to improve their performance in it penetrates the endothelial barrier, minimizing the risk of administration of treatments that do not have an antitumor effect.