Partner: Ayache Bouakaz |
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Recent publications
1. | Delalande A.♦, Bouakaz A.♦, Renault G.♦, Tabareau F.♦, Kotopoulis S.♦, Midoux P.♦, Arbeille B.♦, Uzbekov R.♦, Chakravarti S.♦, Postema M.♦, Pichon C.♦, Ultrasound and microbubble-assisted gene delivery in Achilles tendons: long lasting gene expression and restoration of fibromodulin KO phenotype, Journal of Controlled Release, ISSN: 0168-3659, DOI: 10.1016/j.jconrel.2011.08.020, Vol.156, pp.223-230, 2011 Abstract: The aim of this study is to deliver genes in Achilles tendons using ultrasound and microbubbles. The rationale is to combine ultrasound-assisted delivery and the stimulation of protein expression induced by US. We found that mice tendons injected with 10 μg of plasmid encoding luciferase gene in the presence of 5 × 10^5 BR14 microbubbles, exposed to US at 1 MHz, 200 kPa, 40% duty cycle for 10 min were efficiently transfected without toxicity. The rate of luciferase expression was 100-fold higher than that obtained when plasmid alone was injected. Remarkably, the luciferase transgene was stably expressed for up to 108 days. DNA extracted from these sonoporated tendons was efficient in transforming competent E. coli bacteria, indicating that persistent intact pDNA was responsible for this long lasting gene expression. We used this approach to restore expression of the fibromodulin gene in fibromodulin KO mice. A significant fibromodulin expression was detected by quantitative PCR one week post-injection. Interestingly, ultrastructural analysis of these tendons revealed that collagen fibrils diameter distribution and circularity were similar to that of wild type mice. Our results suggest that this gene delivery method is promising for clinical applications aimed at modulating healing or restoring a degenerative tendon while offering great promise for gene therapy due its safety compared to viral methods. Keywords:Gene delivery, Sonoporation, Tendon Affiliations:
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2. | Postema M.♦, Bouakaz A.♦, ten Cate F.J.♦, Schmitz G.♦, de Jong N.♦, van Wamel A.♦, Nitric oxide delivery by ultrasonic cracking: Some limitations, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2006.06.003, Vol.44, pp.e109-e113, 2006 Abstract: Nitric oxide (NO) has been implicated in smooth muscle relaxation. Its use has been widespread in cardiology. Due to the effective scavenging of NO by hemoglobin, however, the drug has to be applied locally or in large quantities, to have the effect desired. We propose the use of encapsulated microbubbles that act as a vehicle to carry the gas to a region of interest. By applying a burst of high-amplitude ultrasound, the shell encapsulating the gas can be cracked. Consequently, the gas is released upon which its dissolution and diffusion begins. This process is generally referred to as (ultra)sonic cracking. Nitric oxide, Sonic cracking Affiliations:
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3. | Postema M.♦, Bouakaz A.♦, Versluis M.♦, de Jong N.♦, Ultrasound-Induced Gas Release from Contrast Agent Microbubbles, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, ISSN: 0885-3010, DOI: 10.1109/TUFFC.2005.1504026, Vol.52, No.6, pp.1035-1041, 2005 Abstract: We investigated gas release from two hard- shelled ultrasound contrast agents by subjecting them to high-mechanical index (MI) ultrasound and simultaneously capturing high-speed photographs. At an insonifying frequency of 1.7 MHz, a larger percentage of contrast bubbles is seen to crack than at 0.5 MHz. Most of the released gas bubbles have equilibrium diameters between 1.25 and 1.75 m. Their disappearance was observed optically. Free gas bubbles have equilibrium diameters smaller than the bubbles from which they have been released. Coalescence may account for the long dissolution times acoustically observed and published in previous studies. After sonic cracking, the cracked bubbles stay acoustically active. Keywords:Sonic cracking Affiliations:
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4. | Postema M.♦, Bouakaz A.♦, de Jong N.♦, Noninvasive microbubble-based pressure measurements: a simulation study, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2003.12.007, Vol.42, No.1-9, pp.759-762, 2004 Abstract: This paper describes a noninvasive method to measure local hydrostatic pressures in fluid filled cavities. The method is based on the disappearance time of a gas bubble, as the disappearance time is related to the hydrostatic pressure. When a bubble shrinks, its response to ultrasound changes. From this response, the disappearance time, and with it the hydrostatic pressure, can be determined. Noninvasive pressure measurement, Blood pressure, Microbubble, Sonic cracking Affiliations:
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5. | Postema M.♦, Bouakaz A.♦, Chin C.T.♦, de Jong N.♦, Simulations and Measurements of Optical Images of Insonified Ultrasound Contrast Microbubbles, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, ISSN: 0885-3010, DOI: 10.1109/TUFFC.2003.1201465, Vol.50, No.5, pp.523-536, 2003 Abstract: Ultrasound contrast agents (UCAs) are used in a clinical setting to enhance the backscattered signal from the blood pool to estimate perfusion and blood flow. The UCAs consist of encapsulated microbubbles, measuring 1–10 m in diameter. Acoustic characterization of UCAs is generally carried out from an ensemble of bubbles. The measured signal is a complicated summation of all signals from the individual microbubbles. Hence, characterization of a single bubble from acoustic measurements is complex.
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6. | Postema M.♦, Bouakaz A.♦, Chin C.T.♦, de Jong N.♦, Optical observations of ultrasound contrast agent destruction, ACTA ACUSTICA UNITED WITH ACUSTICA, ISSN: 1610-1928, Vol.89, pp.728, 2003 | ||||||||||||||||||||||||||||||||||
7. | Postema M.♦, Bouakaz A.♦, de Jong N.♦, March 2002, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, ISSN: 0885-3010, Vol.49, No.3, pp.c1-c2, 2002 Abstract: The cover page shows a sequence of microscopic image frames of a freely flowing contrast agent microbubble. The frames were taken during one cycle of ultrasound insonification, with a center frequency of 500 kHz. The peak negative acoustic pressure at the region of interest was 0.85 MPa. Each frame corresponds to a 45 x 27 μm2 area. The exposure time of each frame was 10 ns. Interframe times were 330 ns, except for the time between frames e and f, which was 660 ns. The sequence shows a growing gas encapsulated microbubble of 5.3 μm (a) and 17.6 μm (b), and its maximal growth of 22.9 μm (c). After shrinking to 20.2 μm (d), it ruptured (e). The microbubble had been pushed to the lower left side of the frame, apparently by water that was propelled into the microbubble. A subframe shows the negative of the region of interest. Finally, the deformed mcrobubble re-occurred as an assymetric shape (f). Understanding of microbubble-rupturing behavior is neccessary for developments in medical release burst imaging and ultra- sound-guided drug delivery. This work has been supported by the Technology Foundation STW (RKG.5104) and the Interuniversity Cardiology Institute of The Netherlands. Affiliations:
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Conference papers
1. | Delalande A.♦, Bouakaz A.♦, Midoux P.♦, Postema M.♦, Pichon C.♦, Ultrasound-activated microbubbles for tendon gene transfer: in vivo efficiency and confocal microscopy real time intracellular investigations, ICA 2010, 20th International Congress on Acoustics, 2010-08-23/08-27, Sydney (AU), pp.#524-1-3, 2010 Abstract: Ultrasound that is routinely used for imaging is now exploited for therapeutic applications including drug delivery or gene transfer. Today, ultrasound imaging is an established and confident technique for diagnosis. It is mainly based on the development of contrast imaging methods that aim to identify and display the echo from contrast agent as well as rejecting the echo from surrounding tissue offering thus a more resolutive detection. Ultrasound contrast agents or microbubbles (MB) are small gas bubbles encapsulated by a stabilizing shell, with a typical diameter of micron range. Ultrasound pulses are typically applied with a frequency near the resonance frequency of the gas bubble and the bubbles oscillations produce strong echoes from regions of perfused tissue [1-2]. Activation of microbubbles (MB) under specific ultrasound (US) beams induces a transient cell membrane permeabilization with a process known as sonoporation [3-4]. This work aims at evaluating the use of ultrasound and microbubbles for gene transfer in Achilles tendons. Keywords:Ultrasound, Sonoporation, Gene transfer Affiliations:
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2. | de Jong N.♦, Bouakaz A.♦, van Wamel A.♦, Postema M.♦, Versluis M.♦, Microbubbles for ultrasound imaging and therapy, Workshop on Ultrasound in Biomeasurements, Diagnostics and Therapy, Vol.2, pp.123-126, 2004 | ||||||||||||||||
3. | Postema M.♦, Bouakaz A.♦, Chin C.T.♦, de Jong N.♦, Optically observed microbubble coalescence and collapse, IUS 2002, IEEE Ultrasonics Symposium, 2002-10-08/10-11, Monachium (DE), DOI: 10.1109/ULTSYM.2002.1192681, Vol.2, pp.1900-1903, 2002 Abstract: Understanding the mechanisms of microbubble destruction is needed for the development of ultrasound guided drug and gene delivery methods and for the improvement of diagnostic ultrasonic contrast agent (UCA) detection methods. We performed 482 experiments on the coalescence and collapse mechanisms of a soft- shelled and a hard-shelled contrast agent, by subjecting an experimental lipid-shelled UCA and the hard-shelled UCA QuantisonTM to 500 kHz, high- pressured ultrasound (MI≈1.0), and recording microscopic images of these events with a fast- framing camera. Results showed that bubble fragmentation into smaller bubbles is the primary mechanism for lipid-shelled contrast microbubble destruction during the first cycles after ultrasound arrival. In 28% of our experimental events with a lipid-shelled UCA, we observed bubble coalescence. The coalescence mechanism was observed to be analog to the process desribed for larger gas bubbles. Repetitive coalescence and fragmentation was clearly recorded with a fast-framing camera. We also demonstrated the formation and collapse of large lipid-shelled bubbles and bubble clusters. Furthermore we showed that sonic cracking is feasible for the hard-shelled contrast agent QuantisonTM. Affiliations:
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4. | Postema M.♦, Bouakaz A.♦, Chin C.T.♦, de Jong N.♦, Real-time optical imaging of individual microbubbles in an ultrasound field, IUS 2001, IEEE International Ultrasonics Symposium, 2001-10-07/10-10, Atlanta (US), DOI: 10.1109/ULTSYM.2001.992044, Vol.2, pp.1679-1682, 2001 Abstract: In this study we analyze the behavior of individual experimental ultrasonic contrast bubbles, insonofied by 500 kHz ultrasound, at acoustic pressures between 0.06 and 0.66 MPa. The oscillations were observed under a microscope with a fast framing camera.
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