Abstract
Contrast reagents for ultrasound imaging are widely used in clinical medical diagnosis because ultrasound resolution is limited. Contrast agents must be utilized to enhance the image resolution. At present, microbubbles (MBs) and nanobubbles (NBs) are the main contrast reagent candidates for improving the signal resolution. Fluorescence upconversion nanoparticles provide high sensitivity and also function as nanocarriers. This can label tumor cells in a specific organ under irradiation of near-infrared (NIR) light. However, despite the use of NIR light, the penetration depth of NIR is only approximately 15 mm. Thus, we combine fluorescence with ultrasonic imaging to achieve the effect of multiple imaging and solve the low penetration depth of fluorescence imaging and the poor resolution of ultrasound imaging. The dual imaging modalities achieved higher resolution or signal to noise ratios. In this study, Nd3+-sensitized upconversion nanoparticles (UCNPs) are combined with graphitic carbon nitride quantum dots (CNs) and embedded in NBs (UCNP-CN@NBs). The UCNPs are excited by 808 nm light and emit visible and ultraviolet light. Then, the energy of the ultraviolet light is transferred to the CNs to produce reactive oxygen species (ROS) for photodynamic therapy. Ultrasonic waves are also used to promote NB bursting and the release of ROS molecules in photodynamic therapy, leading to cancer cell apoptosis.
Highlights
By the mid-twentieth century, ultrasound was widely used in the medical eld because it can penetrate the muscles and so tissues
When upconversion nanoparticles (UCNPs)–carbon nitride quantum dots (CNs)@NBs are irradiated with 808 nm NIR light, the UCNPs transfer the excited energy to the CNs which produce reactive oxygen species (ROS) by absorbing the upconverted ultraviolet light.[25]
The DPBF reagent was used as a ROS indicator to detect ROS in UCNP–CN@NBs in the solution
Summary
By the mid-twentieth century, ultrasound was widely used in the medical eld because it can penetrate the muscles and so tissues. It is widely used in biomedical applications such as in uorescent probes, biological imaging, disease diagnosis and treatment.[15] Studies reveal the use of UCNPs as a light source carrier to produce ultraviolet and visible light by NIR light excitation.
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