Photoswitchable upconversion nanoparticles with excitation-dependent emission for programmed stepwise NIR...

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Phototherapy

Background:

• Photodynamic therapy (PDT) offers therapeutic potential but lacks precise control.
• Upconversion nanoparticles (UCNPs) can convert near-infrared (NIR) light into visible light for activation.
• Tumor hypoxia is a major challenge in PDT, reducing treatment efficacy.

Purpose of the Study:

• To develop a programmable nanoplatform for controlled phototherapy.
• To engineer core-multi-shell UCNPs capable of emitting red, green, and blue light.
• To investigate the therapeutic benefits of sequential nitric oxide (NO) release prior to PDT.

Main Methods:

• Synthesized core-multi-shell UCNPs using an energy segmentation strategy.
• Integrated UCNPs with photosensitizers and nitric oxide (NO) donors.
• Utilized distinct NIR light wavelengths (1550 nm, 808 nm, 980 nm) for independent activation of imaging, NO release, and reactive oxygen species (ROS) generation.

Main Results:

• Demonstrated independent activation of UCNP functions (imaging, NO release, ROS generation) with specific NIR light.
• Showcased sequential NO release prior to PDT, significantly alleviating tumor hypoxia.
• Observed reduced oxygen consumption due to the stepwise NO release strategy.

Conclusions:

• Developed a smart "off-on" PDT nanoplatform with programmable control.
• Sequential NO release before PDT effectively combats tumor hypoxia.
• This approach enables precise NIR light-activated and imaging-guided phototherapy.