Liquid flooded flow-focusing microfluidic device for in situ generation of monodisperse microbubbles

Current microbubble-based ultrasound contrast agents are administered intravenously resulting in large losses of contrast agent, systemic distribution, and strict requirements for microbubble longevity and diameter size. Instead we propose in situ production of microbubbles directly within the vasculature to avoid these limitations. Flow-focusing microfluidic devices (FFMDs) are a promising technology for enabling in situ production as they can produce microbubbles with precisely controlled diameters in real-time. While the microfluidic chips are small, the addition of inlets and interconnects to supply the gas and liquid phase greatly increases the footprint of these devices preventing the miniaturization of FFMDs to sizes compatible with medium and small vessels. To overcome this challenge, we introduce a new method for supplying the liquid (shell) phase to a FFMD that eliminates bulky interconnects. A pressurized liquid-filled chamber is coupled to the liquid inlets of an FFMD, which we term a flooded FFMD. The microbubble diameter and production rate of flooded FFMDs were measured optically over a range of gas pressures and liquid flow rates. The smallest FFMD manufactured measured 14.5 × 2.8 × 2.3 mm. A minimum microbubble diameter of 8.1 ± 0.3 μm was achieved at a production rate of 450,000 microbubbles/s (MB/s). This represents a significant improvement with respect to any previously reported result. The flooded design also simplifies parallelization and production rates of up to 670,000 MB/s were achieved using a parallelized version of the flooded FFMD. In addition, an intravascular ultrasound (IVUS) catheter was coupled to the flooded FFMD to produce an integrated ultrasound contrast imaging device. B-mode and IVUS images of microbubbles produced from a flooded FFMD in a gelatin phantom vessel were acquired to demonstrate the potential of in situ microbubble production and real-time imaging. Microbubble production rates of 222,000 MB/s from a flooded FFMD within the vessel lumen provided a 23 dB increase in B-mode contrast. Overall, the flooded design is a critical contribution towards the long-term goal of utilizing in situ produced microbubbles for contrast enhanced ultrasound imaging of, and drug delivery to, the vasculature.

[1]  T. Livraghi,et al.  Radiofrequency Ablation of Liver Tumors: The Role of Microbubble Ultrasound Contrast Agents , 2006, Ultrasound quarterly.

[2]  A. Kabalnov,et al.  Dissolution of multicomponent microbubbles in the bloodstream: 1. Theory. , 1998, Ultrasound in medicine & biology.

[3]  George M. Whitesides,et al.  Formation of monodisperse bubbles in a microfluidic flow-focusing device , 2004 .

[4]  Mahidhar Tatineni,et al.  Bubble dispenser in microfluidic devices. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[5]  Jameel A Feshitan,et al.  Microbubble size isolation by differential centrifugation. , 2009, Journal of colloid and interface science.

[6]  H H. Kung,et al.  Microchannel Technologies for Artificial Lungs: (3) Open Rectangular Channels , 2008, ASAIO journal.

[7]  Paul A Dayton,et al.  On-chip generation of microbubbles as a practical technology for manufacturing contrast agents for ultrasonic imaging. , 2007, Lab on a chip.

[8]  Alexander L. Klibanov,et al.  Ultrasound Contrast Agents: Development of the Field and Current Status , 2002 .

[9]  O. A. Asbjornsen,et al.  Size fractionation of gas-filled microspheres by flotation , 1996 .

[10]  Paul A Dayton,et al.  Tailoring the Size Distribution of Ultrasound Contrast Agents: Possible Method for Improving Sensitivity in Molecular Imaging , 2007, Molecular imaging.

[11]  D. Sahn,et al.  Phase I clinical trials of MRX-115. A new ultrasound contrast agent. , 1997, Investigative radiology.

[12]  S. Takayama,et al.  Gravity-driven microfluidic particle sorting device with hydrodynamic separation amplification. , 2007, Analytical chemistry.

[13]  Shangfu Li,et al.  Controllable gas-liquid phase flow patterns and monodisperse microbubbles in a microfluidic T-junction device , 2006 .

[14]  O. Pereira-smith,et al.  Microfluidics device for single cell gene expression analysis in Saccharomyces cerevisiae , 2006, Yeast.

[15]  G. Whitesides,et al.  Fabrication of microfluidic systems in poly(dimethylsiloxane) , 2000, Electrophoresis.

[16]  E. Meng,et al.  Integrated and reusable in-plane microfluidic interconnects , 2008 .

[17]  G. Whitesides,et al.  Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up. , 2006, Lab on a chip.

[18]  P. Phillips,et al.  Contrast pulse sequences (CPS): imaging nonlinear microbubbles , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[19]  S. Feinstein,et al.  Successful left ventricular opacification following peripheral venous injection of sonicated contrast agent: an experimental evaluation. , 1987, American heart journal.

[20]  Paul A Dayton,et al.  Long-term stability by lipid coating monodisperse microbubbles formed by a flow-focusing device. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[21]  F. Moriyasu,et al.  Ultrasound contrast agent, Levovist microbubbles are phagocytosed by Kupffer cells-In vitro and in vivo studies. , 2006, Hepatology research : the official journal of the Japan Society of Hepatology.

[22]  R. Nishi.  Ultrasonic detection of bubbles with doppler flow transducers. , 1972, Ultrasonics.

[23]  D. Weitz,et al.  Monodisperse gas-filled microparticles from reactions in double emulsions. , 2012, Langmuir : the ACS journal of surfaces and colloids.

[24]  R. Senior,et al.  Clinical applications of left ventricular opacification. , 2010, JACC. Cardiovascular imaging.

[25]  John A Hossack,et al.  Dual frequency method for simultaneous translation and real-time imaging of ultrasound contrast agents within large blood vessels. , 2009, Ultrasound in medicine & biology.

[26]  M. Edirisinghe,et al.  Bioinspired bubble design for particle generation , 2012, Journal of The Royal Society Interface.

[27]  Jonathan P. Rothstein,et al.  Scale-up and control of droplet production in coupled microfluidic flow-focusing geometries , 2012 .

[28]  Paul A Dayton,et al.  Molecular ultrasound imaging using microbubble contrast agents. , 2007, Frontiers in bioscience : a journal and virtual library.

[29]  G. Whitesides,et al.  Fabrication of Three-Dimensional Microfluidic Systems by Soft Lithography , 2001 .

[30]  E. G. Tickner,et al.  Why do the lungs clear ultrasonic contrast? , 1980, Ultrasound in medicine & biology.

[31]  M. Edirisinghe,et al.  A device for the fabrication of multifunctional particles from microbubble suspensions , 2012 .

[32]  David A. Weitz,et al.  A new device for the generation of microbubbles , 2004 .

[33]  Piotr Garstecki,et al.  Formation of bubbles and droplets in parallel, coupled flow-focusing geometries. , 2008, Small.

[34]  Annie Colin,et al.  Stability of parallel flows in a microchannel after a T junction. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[35]  Xin Liu,et al.  Microfluidic-assisted formation of multifunctional monodisperse microbubbles for diagnostics and therapeutics , 2011 .

[36]  Mark Borden,et al.  Ultrasound microbubble contrast agents: fundamentals and application to gene and drug delivery. , 2007, Annual review of biomedical engineering.

[37]  A. Gañán-Calvo,et al.  Perfectly monodisperse microbubbling by capillary flow focusing. , 2001, Physical review letters.

[38]  F Forsberg,et al.  Ultrasound contrast agents: a review. , 1994, Ultrasound in medicine & biology.

[39]  A. Klibanov,et al.  Ultrasound triggered image-guided drug delivery. , 2009, European journal of radiology.

[40]  Paul A Dayton,et al.  Advances in Molecular Imaging with Ultrasound , 2010, Molecular imaging.

[41]  Vittorio Cristini,et al.  Monodispersed microfluidic droplet generation by shear focusing microfluidic device , 2006 .

[42]  Detlef Lohse,et al.  Microbubble generation in a co-flow device operated in a new regime. , 2011, Lab on a chip.

[43]  R. Powell,et al.  Needle size and injection rate impact microbubble contrast agent population. , 2008, Ultrasound in medicine & biology.

[44]  E Stride,et al.  Preparation of microbubble suspensions by co-axial electrohydrodynamic atomization. , 2007, Medical engineering & physics.

[45]  Victor Steinberg,et al.  Continuous particle size separation and size sorting using ultrasound in a microchannel , 2006 .

[46]  A R Jayaweera,et al.  Quantification of myocardial blood flow with ultrasound-induced destruction of microbubbles administered as a constant venous infusion. , 1998, Circulation.

[47]  B D Butler,et al.  The lung as a filter for microbubbles. , 1979, Journal of applied physiology: respiratory, environmental and exercise physiology.

[48]  Craig A. Simmons,et al.  Simultaneous generation of droplets with different dimensions in parallel integrated microfluidic droplet generators. , 2008, Soft matter.

[49]  Paul A Dayton,et al.  Acoustic responses of monodisperse lipid-encapsulated microbubble contrast agents produced by flow focusing. , 2010, Bubble science engineering and technology.

[50]  Angeliki Tserepi,et al.  A low temperature surface modification assisted method for bonding plastic substrates , 2008 .

[51]  Kanaka Hettiarachchi,et al.  Controllable microfluidic synthesis of multiphase drug‐carrying lipospheres for site‐targeted therapy , 2009, Biotechnology progress.

[52]  J G Miller,et al.  Contrast Echocardiography: Current and Future Applications , 2000 .

[53]  Robert J Eckersley,et al.  Evidence for spleen-specific uptake of a microbubble contrast agent: a quantitative study in healthy volunteers. , 2004, Radiology.

[54]  G. Whitesides,et al.  Rapid Prototyping of Microfluidic Systems in Poly(dimethylsiloxane). , 1998, Analytical chemistry.

[55]  E Stride,et al.  Preparation of suspensions of phospholipid-coated microbubbles by coaxial electrohydrodynamic atomization , 2009, Journal of The Royal Society Interface.

[56]  P. Tabeling,et al.  Producing droplets in parallel microfluidic systems. , 2006, Physical review. E, Statistical, nonlinear, and soft matter physics.

[57]  Eleanor Stride,et al.  Novel preparation techniques for controlling microbubble uniformity: a comparison , 2009, Medical & Biological Engineering & Computing.

[58]  L. Dalla Palma,et al.  Introduction to ultrasound contrast agents: physics overview , 1999, European Radiology.

[59]  J. Hossack,et al.  Ultrasound-microbubble-mediated drug delivery efficacy and cell viability depend on microbubble radius and ultrasound frequency , 2010, 2010 IEEE International Ultrasonics Symposium.

[60]  Harold H. Kung,et al.  MICROCHANNEL TECHNOLOGIES FOR ARTIFICIAL LUNGS , 2006 .