Local classification of microvascular function based on contrast-enhanced ultrasound data: a feasibility study

National audienceDynamic contrast-enhanced ultrasound can detect microvascular flow changes during tumor development and antiangiogenic therapy. However, the standard method for microvascular flow estimation in tumors is global and can lead to bias in flow estimations in heterogeneous tumors. A new method to segment tumors according to their vascularization was investigated. In addition, parameter normalization with respect to a highly vascularized region of reference was proposed to overcome inter-exam variability in parameters. Results demonstrate the potential to locally classify tumoral tissue using parameters that describes the arrival of an ultrasound contrast agent in the tumor

Caractérisation de l'adhérence cellulaire à l'aide d'un résonateur à quartz

Le résonateur à quartz a été utilisé de façon intensive en tant que capteur sensible à la masse dans les recherches en électrochimie et dan le domaine biomédical. Cette technique utilise des ondes de cisaillement qui permettent au capteur d'analyser de façon non destructive les variations se produisant aux interfaces solide-solide ou solide-liquide. Dans ce travail, nous proposons d'utiliser ce système pour caractériser les propriétés d'inhibition de l'adhésion de cellules humaines (fibroblastes McCoy) développées par des polylères bioactifs. Différents films de ces polymères bioactifs, porteurs de foncions carboxylate et/ou sulfonate, et le poly(méthacrylate de méthyle) (PMMA) en tant que polymère contrôle, sont déposés sur les pastilles de quartz du résonateur. Les effets de modulation de l'adhésion des fibroblastes McCoy induits par ces fims de polymères, de compositions chimiques variables mais définies, sont analysés par le résonateur.The thickness Shear Mode (TSM) quartz crystal resonator has been extensively ued as sensitive sensor in various electrochemical and biological applications. This technique based on the transverse propagation of an acoustic shear wave, enerated by a sinusoïdal electric field through a piezoelectric quartz resonator, provides a non-destructive and powerful mean probing changes at solid-solid or solid-liquid interfaces. In this work, we propose to apply these systems to characterize the inhibition properties developed by active polymers towards human cells (McCoy fibroblast cells) functionalized poly(methylmethacrylate) (PMMA) based copolymers exhibiting either carboxylate and/or sulfonate functional groups and non-functionalized PMMA as control were deposited on quartz samples. The effects of induced inhibition of McCoy fibroblasts cell onto thin functonallized polymeric films of various chemical compositions were analyzed.PARIS13-BU Sciences (930792102) / SudocSudocFranceF

Quantitative Ultrasound and Immunohistochemistry Characterization at Different Stages of Murine Tumor Development

International audienc

An Alternative Quantitative Acoustical and Electrical Method for Detection of Cell Adhesion Process in Real-Time

1 - ArticleSauerbrey [(1956), Z Phys 55:206-222] showed that the shift in resonance frequency of thickness shear mode (TSM) of a quartz crystal sensor is proportional to the mass, which is deposited on it. However, new powerful electrical circuits were developed that are capable of operating TSM quartz crystal sensors in fluids which enabled this method to be introduced into electrochemical and biological applications. These applications include the detection of virus capsids, bacteria, mammalian cells, the interaction of DNA and RNA with complementary strands, specific recognition of protein ligands by immobilized receptors, and last but not least the study of complete immunosensors. Piezoelectric quartz transducers allow a label-free identification of molecules; they are more than mass sensors since the biosensor response is also influenced by the surface charge of adsorbed proteins, interfacial phenomena, surface roughness and viscoelastic properties of the adhered biomaterial. These new characteristics have recently been used to investigate cell, liposome, and protein adhesion onto surfaces, thus permitting the rapid determination of morphological cell changes as a response to pharmacological substances, and changes in the water content of biopolymers avoiding of time-consuming methods. We validated an alternative quantitative acoustical engineering for cell adhesion process monitored by the TSM. Shear acoustical results (motional resistance) are further correlated to cell counting procedures and are sensitive of adhesion processes in real-time

Inhibition of angiogenesis in vitro with soluble copolymers monitored with a quartz crystal resonator

1 - ArticleA quartz crystal resonator was used to monitor specific, integrin-mediated adhesion of human umbilical vein endothelial cells (HUVEC) to distinct water-soluble copolymers on a gold quartz crystal surface. This technique used transverse propagation of an acoustic shear wave generated by a sinusoidal electric field through the quartz crystal and the foreign material provides powerful and non-destructive means for characterizing cell-material interfacial properties. Measurements of the time-variation of the electrical motional resistance near the mechanical sensor resonant frequency were performed to test soluble copolymer plus cell suspensions. Cell adhesion in contact with various soluble copolymers was assessed by the quartz crystal resonator-based technique and compared with cell counting. Inhibition of HUVEC adhesion with different soluble copolymers of various chemical compositions was analyzed and discussed in the perspective of a possible application of these soluble copolymers to anti-angiogenesis. We have shown that bioactive methacrylic acid (MA)/sodium styrene sulfonate (NaSS) based copolymers, bearing both sulfonate and carboxylate groups inhibit adhesion of HUVEC when compared to HUVEC alone. The copolymers tested are excellent candidates for biomedical applications where inhibition of cell adhesion and proliferation is needed: these copolymers can be tested as bioactive molecules or agents against solid tumors, such as anti-angiogenic drugs

Relative Quality of Tumor Growth Equations Describing Volume and Vascular Evolution Assessed with Ultrasound

International audienc

VEGFR2-targeted contrast-enhanced ultrasound to distinguish between two antiangiogenic treatments

International audienceThe aim of this study was to evaluate the capacity of BR55, an ultrasound contrast agent specifically targeting vascular endothelial growth factor receptor 2 (VEGFR2), to distinguish the specific anti-VEGFR2 therapy effect of sunitinib from other anti-angiogenic effects of a therapy (imatinib) that does not directly inhibit VEGFR2. Sunitinib, imatinib and placebo were administered daily for 11 d (264 h) to 45 BalbC mice bearing ectopic CT26 murine colorectal carcinomas. During the course of therapy, B-mode ultrasound, contrast-enhanced ultrasound and VEGFR2-targeted contrast-enhanced ultrasound were performed to assess tumor morphology, vascularization and VEGFR2 expression, respectively. The angiogenic effects on these three aspects were characterized using tumor volume, contrast-enhanced area and differential targeted enhancement. Necrosis, microvasculature and expression of VEGFR2 were also determined by histology and immunostaining. B-Mode imaging revealed that tumor growth was significantly decreased in sunitinib-treated mice at day 11 (p < 0.05), whereas imatinib did not affect growth. Functional evaluation revealed that the contrast-enhanced area decreased significantly (p < 0.02) and by similar amounts under both anti-angiogenic treatments by day 8 (192 h): −23% for imatinib and −21% for sunitinib. No significant decrease was observed in the placebo group. Targeted contrast-enhanced imaging revealed lower differential targeted enhancement, that is, lower levels of VEGFR2 expression, in sunitinib-treated mice relative to placebo-treated mice from 24 h (p < 0.05) and relative to both placebo- and imatinib-treated mice from 48 h (p < 0.05). Histologic assessment of tumors after the final imaging indicated that necrotic area was significantly higher for the sunitinib group (21%) than for the placebo (8%, p < 0.001) and imatinib (11%, p < 0.05) groups. VEGFR2-targeted ultrasound was able to sensitively differentiate the anti-VEGFR2 effect from the reduced area of tumor with functional flow produced by both anti-angiogenic agents. BR55 molecular imaging was, thus, able both to detect early therapeutic response to sunitinib in CT26 tumors as soon as 24 h after the beginning of the treatment and to provide early discrimination (48 h) between tumor response during anti-angiogenic therapy targeting VEGFR2 expression and response during anti-angiogenic therapy not directly acting on this receptor

Ultrasound-triggered delivery of paclitaxel encapsulated in an emulsion at low acoustic pressures

International audienceWe investigated the in vitro ultrasound-triggered delivery of paclitaxel, a well known anti-cancerous drug, encapsulated in an emulsion and in the presence of CT26 tumor cells. The emulsion was made of nanodroplets, which volume comprised 95% of perfluoro-octyl bromide and 5% of tributyl O-acetylcitrate, where paclitaxel was solubilized. These nanodroplets, prepared using a high-pressure microfluidizer, were stabilized by a tailor-made and recently patented biocompatible fluorinated surfactant. The delivery investigations were performed at 37°C using a high intensity focused ultrasound transducer at a frequency of 1.1 MHz. The ultrasonic pulse was made of 275 sinusoidal periods, the pulse repetition frequency was 200 Hz with a duty cycle of 5%. The measured viabilities of CT26 cells showed that paclitaxel delivery was achievable for peak-to-peak pressures of 0.4 and 3.5 MPa, without having to vaporize the perfluorocarbon part of the droplet or to induce inertial cavitation