Bactericidal Activity of Lipid-Shelled Nitric Oxide-Loaded Microbubbles

Maxime Lafond; Himanshu Shekhar; Warunya Panmanee; Sydney D Collins; Arunkumar Palaniappan; Cameron T McDaniel; Daniel J Hassett; Christy K Holland

doi:10.3389/fphar.2019.01540

Bactericidal Activity of Lipid-Shelled Nitric Oxide-Loaded Microbubbles

Front Pharmacol. 2020 Jan 30:10:1540. doi: 10.3389/fphar.2019.01540. eCollection 2019.

Authors

Maxime Lafond¹, Himanshu Shekhar¹, Warunya Panmanee², Sydney D Collins¹, Arunkumar Palaniappan¹, Cameron T McDaniel², Daniel J Hassett², Christy K Holland^{1

3}

Affiliations

¹ Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH, United States.
² Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States.
³ Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, United States.

Abstract

The global pandemic of antibiotic resistance is an ever-burgeoning public health challenge, motivating the development of adjunct bactericidal therapies. Nitric oxide (NO) is a potent bioactive gas that induces a variety of therapeutic effects, including bactericidal and biofilm dispersion properties. The short half-life, high reactivity, and rapid diffusivity of NO make therapeutic delivery challenging. The goal of this work was to characterize NO-loaded microbubbles (MB) stabilized with a lipid shell and to assess the feasibility of antibacterial therapy in vitro. MB were loaded with either NO alone (NO-MB) or with NO and octafluoropropane (NO-OFP-MB) (9:1 v/v and 1:1 v/v). The size distribution and acoustic attenuation coefficient of NO-MB and NO-OFP-MB were measured. Ultrasound-triggered release of the encapsulated gas payload was demonstrated with 3-MHz pulsed Doppler ultrasound. An amperometric microelectrode sensor was used to measure NO concentration released from the MB and compared to an NO-OFP-saturated solution. The effect of NO delivery on the viability of planktonic (free living) Staphylococcus aureus (SA) USA 300, a methicillin-resistant strain, was evaluated in a 96 well-plate format. The co-encapsulation of NO with OFP increased the total volume and attenuation coefficient of MB. The NO-OFP-MB were destroyed with a clinical ultrasound scanner with an output of 2.48 MPa peak negative pressure (in situ MI of 1.34) but maintained their echogenicity when exposed to 0.02 MPa peak negative pressure (in situ MI of 0.01. The NO dose in NO-MB and NO-OFP-MB was more than 2-fold higher than the NO-OFP-saturated solution. Delivery of NO-OFP-MB increased bactericidal efficacy compared to the NO-OFP-saturated solution or air and OFP-loaded MB. These results suggest that encapsulation of NO with OFP in lipid-shelled MB enhances payload delivery. Furthermore, these studies demonstrate the feasibility and limitations of NO-OFP-MB for antibacterial applications.

Keywords: USA 300 Staphylococcus aureus; bactericide; bioactive gas delivery; echocontrast agent; lipid-shelled microbubbles; nitric oxide delivery; ultrasound.

Grants and funding

R01 NS047603/NS/NINDS NIH HHS/United States