Multifunctional microbubbles and nanobubbles for photoacoustic and ultrasound imaging

Abstract

We develop a novel dual-modal contrast agent-encapsulated-ink poly(lactic-co-glycolic acid) (PLGA) microbubbles and nanobubbles-for photoacoustic and ultrasound imaging. Soft gelatin phantoms with embedded tumor simulators of encapsulated-ink PLGA microbubbles and nanobubbles in various concentrations are clearly shown in both photoacoustic and ultrasound images. In addition, using photoacoustic imaging, we successfully image the samples positioned below 1.8-cm-thick chicken breast tissues. Potentially, simultaneous photoacoustic and ultrasound imaging enhanced by encapsulated-dye PLGA microbubbles or nanobubbles can be a valuable tool for intraoperative assessment of tumor boundaries and therapeutic margins.

Figure 1

(a) Schematic of MBs and NBs encapsulating black India ink. The size distributions of encapsulated-ink (b) MBs and (c) NBs. The x axis is a log scale. VWD: Volume weighted distribution.

Figure 2

(a) Photograph of a phantom containing tumor simulators made of encapsulated-ink MBs and NBs with various concentrations. (b) The corresponding PA image. (c) The corresponding US image. (d) The quantification of the PA signals at various concentrations of MBs and NBs. (e) The quantification of the US signals at various concentrations of MBs and NBs. 1 through 4: MBs at concentrations of 2.5, 5.0, 10, and 15 mg∕mL, respectively. 5 through 8: NBs at concentrations of 2.5, 5.0, 10, and 15 mg∕mL, respectively.

Figure 3

(a) Photograph of a phantom containing tumor simulators made of encapsulated-ink MBs and NBs with various concentrations. (b) The corresponding PA image of the phantom positioned below 8 mm of chicken breast tissues. (c) The corresponding PA image of the phantom positioned below 18 mm of chicken breast tissues. 1 through 4: MBs at concentrations of 2.5, 5.0, 10, and 15 mg∕mL, respectively. 5 through 8: NBs at concentrations of 2.5, 5.0, 10, and 15 mg∕mL, respectively.