Gas vesicle isolated from microorganisms to act as ultrasound contrast agent
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ORIGINAL ARTICLE
Gas vesicle isolated from microorganisms to act as ultrasound contrast agent Felipe Vianna Garrute 1
&
João Carlos Machado 1,2
Received: 12 March 2020 / Accepted: 2 September 2020 # Sociedade Brasileira de Engenharia Biomedica 2020
Abstract Purpose Ultrasound contrast agent (UCA), used to enhance the contrast in ultrasonography, consists of microbubbles filled with an inert gas and encapsulated with a protein or a lipidic-stabilize membrane. The UCAs are able to resonate when exposed to ultrasound waves and to generate an echo-acoustic signal with increased intensity. Recently, a technique to produce UCA from microorganisms was developed and it consists of lysing microorganism cells to obtain gas vesicle (GV) after cultivation in the laboratory. GVs occur almost exclusively in aquatic microorganisms, as Microcystis aeruginosa (MYC), and provide buoyancy which permit to float towards the water surface. This work implemented a technique to produce GVs from MYC, at the Ultrasound Laboratory, and inspected their properties of acting as UCAs, analyzed through ultrasonic images acquired at 40 MHz, and their structural characteristics such as morphology, diameter, and length. Methods After the cultivation of MYC, the buoyant cells with GVs were separated from the culture medium and submitted to cell lysis with chemical treatment. Thereafter, the solution with lysed cells was centrifuged, at 300g during 8 h at 4–8 °C, to isolate the GVs (absorbance 0.6, λ = 500 nm). Results Transmission electron microscopy inspection revealed the MYC-GVs with elliptical morphology and having a diameter between 100 and 150 nm and length near to 200 nm. B-mode ultrasound images of the solutions proved the GV’s ability to generate an echo signal, thus confirming their performance as UCAs. Keywords Gas vesicle . Microcystis aeruginosa . Ultrasound . Ultrasound contrast agent
Introduction Ultrasound contrast agent (UCA) has been used in diagnostic imaging to improve the image contrast quality, for over 50 years since it was discovered by Gramiak et al. (1969). Nowadays, UCAs are microbubbles (MBs) with inert gas recovered by protein- or lipidic-stabilized membrane. The MB
* Felipe Vianna Garrute [email protected] João Carlos Machado [email protected] 1
Biomedical Engineering Program-COPPE, Federal University of Rio de Janeiro, Horácio Macedo Ave., 2030, Center of Technology, Block H, Room 327, Rio de Janeiro, RJ 21941-914, Brazil
2
Post-graduate Program in Surgical Sciences, Department of Surgery, School of Medicine, Federal University of Rio de Janeiro, Carlos Chagas Filho Ave., 373, Health Sciences Center, Block K, Room 49, Rio de Janeiro, RJ 21941-902, Brazil
diameter varies 1–10 μm and they are capable to resonate when exposed to ultrasound (US) waves and generate an intense acoustic echo signal due to the difference of acoustic impedance between the gas and surrounding tissue (Chomas et al. 2001; Hernot and Klibanov 2008; Hunt and Romero 2017; Wheatley and Cochran 2013). The partial pressure between the mi
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