Mok, A. T. | Search bioRxiv

bioRxiv2019

Enhancing generating and collecting efficiency of single particle upconverting luminescence at low-level power excitation

Upconverting luminescent nanoparticles are photostable, non-blinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probe at single-molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) is achieved with highly doped rare-earth ions co-doped (20% Yb3+) using high excitation power (>2.5 MW/cm2). However, such particles are inadequate for in-vitro live-cell imaging and single-particle tracking since high excitation power can cause photodamage. Here, we compared UCNPs luminescence intensities with different dopants concentrations and presented a more efficient ([~]7x) UCNPs at low excitation power by increasing the concentrations of Yb3+ and Tm3+ dopants (NaYF4: 60% Yb3+, 8% Tm3+) and adding a core-shell structure.

biophysics↗

bioRxiv2019

Non-invasive multiphoton imaging of neural structure and activity in Drosophila

We developed a multiphoton imaging method to capture neural structure and activity in behaving flies through the intact cuticles. Our measurements show that the fly head cuticle has surprisingly high transmission at wavelengths > 900 nm, and the difficulty of through-cuticle imaging is due to the air sacs and/or fat tissue underneath the head cuticle. By compressing the air sacs, we performed deep multiphoton imaging of fly brains through the intact cuticle. Our anatomical and functional imaging results show that 2- and 3-photon imaging are comparable in superficial regions such as the mushroom body, but 3-photon imaging is superior in deeper regions such as the central complex and beyond. We further demonstrated 2-photon through-cuticle functional imaging of odor-evoked calcium responses from the mushroom body {gamma}-lobes in behaving flies short-term and long-term (12 consecutive hours). The through-cuticle imaging method developed here extends the time limits of in vivo imaging in flies, and opens up new ways to capture neural structure and activity from the intact fly brain.

neuroscience↗