Photoacoustic and Magnetic Resonance Imaging Bimodal Contrast Agent Displaying Amplified Photoacoustic Signal

Abstract

Progress in photoacoustic (PA) and magnetic resonance imaging (MRI) bimodal contrast agents has been achieved mainly by utilizing the imaging capability of single or multiple components and consequently realizing the desired application for both imaging modalities. However, the mechanism of the mutual influence between components within a single nanoformulation, which is the key to developing high‐performance multimodal contrast agents, has yet to be fully understood. Herein, by integrating conjugated polymers (CPs) with iron oxide (IO) nanoparticles using an amphiphilic polymer, a bimodal contrast agent named CP‐IO is developed, displaying 45% amplified PA signal intensity as compared to bare CP nanoparticle, while the performance of MRI is not affected. Further experimental and theoretical simulation results reveal that the addition of IO nanoparticles in CP‐IO nanocomposites contributes to this PA signal amplification through a synergistic effect of additional heat generation and faster heat dissipation. Besides, the feasibility of CP‐IO nanocomposites acting as PA‐MRI bimodal contrast agents is validated through in vivo tumor imaging using mice models. From this study, it is demonstrated that a delicately designed structural arrangement of various components in a contrast agent could potentially lead to a superior performance in the imaging capability.

Organic nanoparticle-doped microdroplets as dual-modality contrast agents for ultrasound microvascular flow and photoacoustic imaging

“…Figure 3 B shows the PA images of the microdroplets in tubes. The PA effects were activated by the laser pulse at 750 nm, which is the absorption peak of CP NPs 24 . The irradiation energy is 4.7 mJ/pulse for subfigure a) and 14 mJ/pulse for subfigure (b).…”

“…S3 ), the microdroplets were further tested in vivo in healthy animals by injecting via tail vein and keeping the animals under consistent monitoring for over 15 min to ensure the safety of the three layer structures. The cell toxicity and animal experiments of the CP NPs have been conducted by the previous researches 24 , 25 , and thus were not repeated.…”

“…This dual-modality contrast agents can be further investigated in several ways. If multifunction NPs were used, such as NPs that could provide contrast effects not only for PA, but also for MRI 24 , the additional functions of NPs could also be utilized and thus the microdroplets would provide triple (e.g. US flow, PA and MRI), quadruple or even more functions in the same structures.…”

Nanoparticles as contrast agents for photoacoustic brain imaging

“…Besides nanostructures, that is, the physical arrangement of different components within a single nanoagent, could also lead to distinct or superior PA performance due to synergy or enhancement in the photothermal generation capability. For instance, it has been reported that the increased iron oxide ratio of the conjugated polymers PDPP3T/iron oxide coencapsulated NPs could amplify the PA signal by generating additional heat and dissipating the heat produced in a faster manner 75 . Furthermore, the distribution of iron oxide NPs and organic molecules in the formed nanostructure was also reported to affect the PA signal (Figure 9).…”

Microwave-Driven Synthesis of Iron-Oxide Nanoparticles for Molecular Imaging

“…These properties explain the use of IONPs in all major imaging techniques, with examples in OI [37], PAI [38], SPECT [39], PET [30] and MRI [36], and magnetic resonance imaging [35,40,41]. MRI deserves special mention since it is the most commonly used imaging technique with IONPs due to their magnetic properties.…”