Dendritic upconverting nanoparticles enable in vivo multiphoton microscopy with low-power continuous wave sources

Area of Science:

• Nanotechnology
• Biomedical Optics
• Materials Science

Background:

• Upconverting lanthanide nanoparticles (UCNPs) offer unique optical properties but often suffer from poor solubility and biocompatibility.
• Dendrimers are highly branched polymers with tunable properties, making them promising candidates for nanoparticle surface modification.

Purpose of the Study:

• To develop stable, water-soluble, and biocompatible optical imaging probes by conjugating polyanionic dendrimers to UCNPs.
• To demonstrate the utility of these dendritic UCNPs for in vivo imaging and sensing applications.

Main Methods:

• UCNPs were pretreated and then coated with polyanionic dendrimers, forming stable nanomaterials.
• The resulting dendritic UCNPs were functionalized with porphyrin for pH sensing via excitation energy transfer (EET).
• In vivo imaging was performed in mice using polyglutamic dendritic UCNPs to visualize cortical vasculature.

Main Results:

• Stable, water-soluble, and biocompatible UCNP-dendrimer nanomaterials were successfully synthesized.
• Porphyrin-dendrimer modified UCNPs functioned as upconverting ratiometric pH nanosensors.
• In vivo imaging demonstrated high-resolution visualization of mouse cortical vasculature up to 400 μm deep using continuous wave excitation.

Conclusions:

• Dendrimerization is an effective strategy for solubilizing and enhancing the biocompatibility of UCNPs.
• These dendritic UCNPs are suitable for in vivo biological imaging and sensing, particularly for high-resolution microscopy.
• The developed UCNP-dendrimer probes open new avenues for advanced biomedical applications.