System identification of the intrabrain tumoral uptake of multifunctional nanoparticles

International audienceRecent developments on multifunctional nano-systems have opened new perspectives for tumor control by proposing new nano-actuators and nano-sensors in in vivo anti-cancer treatments. But the delivery control of these nano-agents into the cancer cells is one of the major factors that directly affect the efficiency of nanotherapies. In this study, we show that system identification methods (CONTSID Matlab toolbox), generally used in control engineering, can bring efficient solutions to help biologists to estimate crucial parameters of the nanoparticles pharmacokinetics from experimental data. The in vivo results presented herein clearly emphasize the relevance of these data-driven modeling approaches associated with magnetic resonance imaging

A system-engineering model to analyze gap-FRAP in multicellular models.

International audienceIntroduction. Developed in the 70s, the Fluorescence Recovery After Photobleaching (FRAP) technique is based on the progressive increase of fluorescence intensity in a photobleaching area obtained after an illumination with a LASER beam. This enhancement corresponds to the gradual arrival (through gap junctions) of intact fluorescent molecules towards the targeted zone. This widely used method is principally dedicated to study fluorescent constituents mobility in cellular membranes and gap junctional intercellular communication (GJIC) at microscopic scale. Purpose. The final addressed question is to assess the relevance to use GJIC characteristics to discriminate different cancer cell lines. With this aim in view, we have proposed a model-based approach in which some parameters could be potentially used as decision statistics. As proof of concept, we have tested the applicability of a compartmental model to describe differences between gap-FRAP responses of two human head and neck carcinoma cell lines (FaDu and KB). . Methods and Materials. Cx43, a protein of the connexin family responsible for GJIC, distribution and intercellular communication of FaDu and KB cells were performed in monolayer cultured cells and spheroids. Six experiments were performed for each case and data were collected through an imaging system composed of a macroscope combined to a fluorescence excitation source (Hg) and a CCD camera. The pixel intensities were measured in three concentric Regions of Interest (ROI) every 15 seconds for 15 minutes on each images. The measured values were assumed to be proportional to the mean amount of photons emitted in each ROI. After normalization with respect to the fluorescence intensity values before photobleaching, the data were plotted across the time. Modeling method. To study gap-Fluorescence Recovery After Photobleaching (gap-FRAP), the perturbation-relaxation kinetic equation is commonly used but is sometimes unable to describe some parts of the fluorescence response. A new behavioral model is proposed to study fluorescence recovery. The latter is based on a three-compartment representation (one compartment for each ROI) and the rates between each compartment represent the flow coefficients of the different gap junctions. This model provides a set of differential equations for which the associated continuous-time second-order transfer function was identified using the Simplified Refined Instrumental Variable in Continuous-time (SRIVC) algorithm. The algorithm returns three estimated parameters (a static gain and two time constants) and their standard deviations. Results. Two model parameters have allowed us to discriminate gap junctions functionalities. Indeed, parameters of KB cells, which is positive for Cx43 expression, are significantly superior to those of FaDu cells in culture 2-D and 3-D. No significant differences were observed for KB cells data independently of culture type confirming negligible contribution from underlying layers during fluorescence restitution in Z plan by confocal microscopy. Conclusions. Our study exemplifies the contributions brought by dynamic models of biological phenomena to diagnostic applications in biomedicine

Real-time control of photobleaching trajectory during photodynamic therapy

International audienceIntroduction: obstacles and challenges to the clinical use of the photodynamic therapy (PDT) are numerous: large inter-individual variability, heterogeneity of therapeutic predictability, lack of in vivo monitoring concerning the reactive oxygen species (ROS) production, etc. All of these factors affect in their ways the therapeutic response of the treatment and can lead to a wild uncertainty on its efficiency. Objective: to deal with these variability sources, we have designed and developed an innovative technology able to adapt in realtime the width of light impulses during the photodynamic therapy. The first objective is to accurately control the photobleaching trajectory of the photosensitizer during the treatment with a subsequent goal to improve the efficacy and reproducibility of this therapy.Methods: in this approach, the physician a priori defines the expected trajectory to be tracked by the photosensitizer photobleaching during the treatment. The photobleaching state of the PS is regularly measured during the treatment session and is used to change in real-time the illumination signal. This adaptive scheme of the photodynamic therapy has been implemented, tested and validated during in vitro tests.Results: these tests show that controlling the photobleaching trajectory is possible, confirming the technical feasibility of such an approach to deal with inter-individual variabilities in PDT. These results open new perspectives since the illumination signal can be different from a patient to another according to his individual response.Conclusions: this study has proven its interest by showing promising results in an in vitro context, which has to be confirmed by the current in vivo experiments. However, it is fair to say that in a near future, the proposed solution could lead, in fine, to an optimized and personalized PDT

Biological systems identification and control. Application to the photodynamic therapy

Les travaux présentés dans ce manuscrit sont divisés en deux grandes parties, et abordent des applications biologiques relatives au cancer et plus particulièrement à leur traitement. La première partie est consacrée à une recherche technologique, dont l'objectif est le développement d'un dispositif innovant permettant de contrôler plus efficacement la phase cytotoxique de la thérapie photodynamique. Cette thérapie contre le cancer met en jeu trois éléments principaux : un agent photosensibilisant, de l'oxygène et de la lumière. La solution proposée repose sur une stratégie d'asservissement d'un indicateur thérapeutique observable durant le traitement : le photoblanchiment. Le système d'asservissement développé utilise un observateur d'état qui a nécessité de résoudre en pratique des problèmes d'identifiabilité et d'identification d'un processus non-linéaire. Il est implanté dans une plateforme pilote opérationnelle validée par des tests in vitro. Une demande de brevet pour le dispositif développé est en cours. La seconde partie de cette thèse s'inscrit dans le cadre d'une recherche appliquée, sur le thème de l'identification à temps continu de systèmes biologiques, à partir de séquences d'images au travers de trois cas d'études aux échelles cellulaire, tissulaire et animale. Une première étude est dédiée à la proposition d'un modèle à compartiments de la pharmacocinétique intratumorale de nanoparticules multifonctionnelles dans des cerveaux de rats, ainsi qu'à son identification à partir de séquences d'images IRM in vivo. La seconde traite de la modélisation, à partir de données d'imagerie expérimentale de fluorescence, de la fonctionnalité des jonctions communicantes intercellulaires. L'objectif est de discriminer deux types de cellules cancéreuses, grâce à leur dynamique de recouvrement de fluorescence. Enfin, un troisième cas d'étude aborde le problème de l'identification d'une cohorte de systèmes à partir de petits échantillons de données. Le contexte applicatif est l'étude de l'angiogenèse tumoral et de l'effet des traitements anti-cancer sur le développement du réseau vasculaireThe presented works are divided into two main parts and deal with biological applications to cancer, and more specifically to their treatments. The first part is dedicated to a technological research, in which a new device is designed and built to efficiently control the cytotoxic phase of photodynamic therapy. This anti-cancer therapy involves three main compounds: a photosensitizer agent, oxygen and light. The proposed solution relies on the control of an observable therapeutic indicator during the treatment: the photobleaching phenomenon. The developed control system uses a state observer which required to solve practical identifiability issues and the identification of a non-linear process. It has been implemented in a technical platform and validated during in in vitro tests. A patent application for this device is currently under review. The second section of this thesis deals with the applicability of continuous-time identification approaches to three biological systems from image sequences recorded at cellular, tissue and animal scales. A first study examines how continuous-time system identification may be used to determine a pharmacokinetic compartmental model of multifunctional nanoparticles within rat brain from in vivo MRI images. The second study deals with the empirical modeling of the junctional intercellular communication functionalities. The purpose is to discriminate two cancer cells types from their fluorescence recovery dynamics. Finally, a third study case addresses the issue of identifying a systems cohort from small amount of data. The applied context is the study of tumoral angiogenesis and the anti-cancer treatment effects on vascular network developmen

Identification et contrôle de systèmes biologiques. Application à la thérapie photodynamique

The presented works are divided into two main parts and deal with biological applications to cancer, and more specifically to their treatments. The first part is dedicated to a technological research, in which a new device is designed and built to efficiently control the cytotoxic phase of photodynamic therapy. This anti-cancer therapy involves three main compounds : a photosensitizer agent, oxygen and light. The proposed solution relies on the control of an observable therapeutic indicator during the treatment : the photobleaching phenomenon. The developed control system uses a state observer which required to solve practical identifiability issues and the identification of a non-linear process. It has been implemented in a technical platform and validated during in in vitro tests. A patent application for this device is currently under review. The second section of this thesis deals with the applicability of continuous-time identification approaches to three biological systems from image sequences recorded at cellular, tissue and animal scales. A first study examines how continuous-time system identification may be used to determine a pharmacokinetic compartmental model of multifunctional nanoparticles within rat brain from in vivo MRI images. The second study deals with the empirical modeling of the junctional intercellular communication functionalities. The purpose is to discriminate two cancer cells types from their fluorescence recovery dynamics. Finally, a third study case addresses the issue of identifying a systems cohort from small amount of data. The applied context is the study of tumoral angiogenesis and the anti-cancer treatment effects on vascular network development.Les travaux présentés dans ce manuscrit sont divisés en deux grandes parties, et abordent des applications biologiques relatives au cancer et plus particulièrement à leur traitement. La première partie est consacrée à une recherche technologique, dont l’objectif est le développement d’un dispositif innovant permettant de contrôler plus efficacement la phase cytotoxique de la thérapie photodynamique. Cette thérapie contre le cancer met en jeu trois éléments principaux : un agent photosensibilisant, de l’oxygène et de la lumière. La solution proposée repose sur une stratégie d’asservissement d’un indicateur thérapeutique observable durant le traitement : le photoblanchiment. Le système d’asservissement développé utilise un observateur d’état qui a nécessité de résoudre en pratique des problèmes d’identifiabilité et d’identification d’un processus non-linéaire. Il est implanté dans une plateforme pilote opérationnelle validée par des tests in vitro.Une demande de brevet pour le dispositif développé est en cours. La seconde partie de cette thèse s’inscrit dans le cadre d’une recherche appliquée, sur le thème de l’identification à temps continu de systèmes biologiques, à partir de séquences d’images au travers de trois cas d’études aux échelles cellulaire, tissulaire et animale. Une première étude est dédiée à la proposition d’un modèle à compartiments de la pharmacocinétique intratumorale de nanoparticules multifonctionnelles dans des cerveaux de rats, ainsi qu’à son identification à partir de séquences d’images IRM in vivo. La seconde traite de la modélisation, à partir de données d’imagerie expérimentale de fluorescence, de la fonctionnalité des jonctions communicantes intercellulaires. L’objectif est de discriminer deux types de cellules cancéreuses, grâce à leur dynamique de recouvrement de fluorescence. Enfin, un troisième cas d’étude aborde le problème de l’identification d’une cohorte de systèmes à partir de petits échantillons de données. Le contexte applicatif est l’étude de l’angiogenèse tumoral et de l’effet destraitements anti-cancer sur le développement du réseau vasculaire

Global sensitivity analysis and estimation of photophysical parameters from in vivo data in photodynamic therapy

International audiencePhotodynamic therapy (PDT) is an alternative treatment for cancer that involves the administration of a photosensitizing agent, which is activated by light at a specific wavelength. In this project, we aim at developing a model-based approach to compare the in vivo photodynamic efficiencies of different photosentizers. Unfortunately, constraints of in vivo experiments are such that it is impossible to estimate all the photophysical parameters. However in this paper, a feasibility study is performed to (i) select the most relevant model parameters and (ii) estimate their value and their confidence interval. Despite the previously mentioned difficulties, the results obtained in practice from in vivo experiments have shown promising results

An Automatic Method for the Segmentation and Classification of Imminent Labor Contraction from Electrohysterograms

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Pharmacokinetic modeling of nanoparticles-based PS vectors into glioblastoma from MRI imaging in PDT

International audienceRecent developments on multifunctional nano-systems have opened new perspectives for tumor control by proposing new nano-actuators and nano-sensors in in vivo anti-cancer treatments. One of these challenging perspectives is the use of nanoparticles as vector to deliver the right dose of PS (Photosensitizer agent) into the tumor. But the delivery control of these nano-agents into the cancer cells is one of the major factors that directly affect the efficiency of the photodynamic therapy. Several previous works have already shown that the intracellular uptake could not be predicted from the nano-object chemical properties. In 2004, the FDA's Critical Path Report proposed, among other solutions, the increased use of model-based approaches to drug development, including pharmacokinetic and pharmacodynamic (PK/PD) modeling. In this study, we propose a non-supervised estimation method, developed to estimate the pharmacokinetic parameters of two multifunctional nanoparticles involved in photodynamic therapy. We show that continuous-time model identification methods (available in the CONTSID toolbox for Matlab), generally used in control engineering, can bring efficient solutions to help biologists to estimate crucial parameters of the nanoparticles pharmacokinetics from experimental data. The in vivo results presented clearly emphasize the relevance of these data-driven modeling approaches associated with magnetic resonance imaging

Realtime tracking of the photobleaching trajectory during photodynamic therapy

International audiencePhotodynamic therapy (PDT) is an alternative treatment for cancer that involves the administration of a photosensitizing agent, which is activated by light at a specific wavelength. This illumination causes after a sequence of photoreactions, the production of reactive oxygen species responsible for the death of the tumor cells but also the degradation of the photosensitizing agent, which then loose the fluorescence properties. The phenomenon is commonly known as photobleaching process and can be considered as a therapy efficiency indicator. Methods: This paper presents the design and validation of a real time controller able to track a preset photobleaching trajectory by modulating the light impulses width during the treatment sessions. Results:This innovative solution was validated by in vivo experiments that have shown a significantly improvement of reproducibility of the inter-individual photobleaching kinetic. Conclusion: We believe that this approach could lead to personalized photodynamic therapy modalities. Significance: This work may open new perspectives in the control and optimization of photodynamic treatments