Polymeric nanovectors transfer, from blood flow to tumors – Polytransflow

If the scientific challenge PolyTransFlow is interdisciplinar, different ways coming from biology, chemistry, mechanics and physics are used to progress crossing the points of views to contribute to a better understanding. The project is supported by four teams with various skills, IPBS for biology, IRMCP for chemistry, IRPHE and LASS for mechanics and physics. The undertaken methods are the following:
* in vitro studies on model systems based on microfluidic chips.
* in vivo studies of the transport of polymersomes inside the blood network of mice. These polymersomes are selected by the preliminar in vitro results.
* in silico studies by the numerical simulations of polymersomes under flow to determine accurately the forces which play a role.
The works concern the production of polymersomes by several methods and with numerous diblock copolymers, their physico-chemical characterization and their behavior under flow of blood (in vivo and in vitro) or model suspensions (in vitro). These last experiments are performed in microfluidic (the scale of the blood vessels) and nanofluidic (the scale of the distance between endothelial cells) chips.

* Study of the transition between tubular polymersome and pearls: dynamical role of the shear membrane viscosity
* Characterization of polymersomes made with various processes from hundred nanometers to tens of micrometer sizes.
* Study of the dynamics of a drop with interface shear viscosity in a shear flow.

* To establish several criteria to select the kind of polymeromes to use to optimize their stealth and their ability to go from blood to tumors.
* To highlight in vitro, in vivo and in silico the salient parameters which control the phenomenon of margination, the transfer through the endothelium and after the tissues

- 1 article in international scientific journals (ISI) + 1 submitted (ISI)
- 1 oral communication in an international congress
- 2 posters in national meetings

In the domain of anticancer drug delivery, a tremendous discrepancy is observed between the hundreds of scientific papers dealing with polymeric nanovectors and the absence of clear explanation of their transport and fate in blood flow. The influence of margination (migration of objects from vessel center to walls) on their transfer from blood stream to tumor tissue is also another poorly studied step. One of the reasons is that along the journey between injection and delivery sites, many different processes arise, which are related to mechanics and physics (hemodynamics, mechanical properties of the vectors…), chemistry (surface groups, size, charge…) and biology (different cell types, numerous proteins…). This project aims at focusing on the step enabling a certain type of vectors, namely polymersomes, to leave the bloodstream to get to the tumor site.
Polymersomes, a kind of deformable particles, know an increasing enthusiasm from biology, chemistry and pharmacology due to their biocompatibility, their ability to be tuned and their physico-chemical properties preventing their removal from blood by the Mononuclear Phagocytic System.
This project is organized in three different parts, each providing fractional answers to the whole problem, planned in order to get closer from the biological reality at each step.
In a first step, hydrodynamic processes leading to margination will be characterized. This still unexplained phenomenon will be studied using a blood model composed by a binary suspension of polymersomes and red blood cells (RBC) without aggregates. Visualization of this blood model streaming and measurements of concentration profiles will be performed in microfluidic chips for the first time.The aim of this part is to determine whether polymersomes move towards the vessel wall as platelets and to quantify margination as a function of the mechanical properties of the polymersomes (more or less stiff).Recent numerical studies have succeeded to simulate margination in some cases but are limited due to the lack of experimental cornerstones. The design of chips will permit to test the theoretical ideas by allowing a modulation of the frequency of hydrodynamic homogeneous and heterogeneous collisions between RBC,polymersomes and wall which are thought to determine the suspension configuration.
The second part will deal with the nanovector transfer through loose junctions present close to solid tumors. This process is essential for the successful delivery of the vectors to the tumors, thanks to the “Enhanced Permeability and Retention” effect (no specific interaction with endothelial cells). Our project will be the first to mimic the critical size of the loose junctions.This is possible by designing synthetic vessels presenting pores that can be controlled down to 100 nm and tracking of single polymersomes inside. The passage through these junctions will be statistically characterized depending on Brownian motion (the so-called Péclet number), different geometrical parameters and different motion forces due to a pressure difference or salt concentration,both with and without RBC.
Finally, the last part of the project further approaches reality in several steps. In order to better understand the biodistribution of the polymersomes, their penetration in both cancer and endothelial cells will be assessed both in 2D and in 3D by the use of multicellular spheroids composed of cancer and endothelial cells.This work will enable us to assess compared affinities of the vectors to the different cell types. Finally, the possibility of tracking the vectors directly in vivo in mice using dorsal window chambers provides the unique opportunity to compare these living dynamics to margination and transfer in system models.
The aim of this project is thus to provide a multi-scale and multi-disciplinary approach of synthetic vectors hydrodynamical transport in blood vessels and through loose junctions, salient steps before the drug delivery.