PTO-41

PTO-41 (4 mg/kg; intravenous injection; single bolus) can cross the blood-brain barrier and specifically label β-amyloid oligomers in 4-month-old APP/PS1 mice; at 30 min post-injection, the NIRF signal in transgenic mice is 1.30-fold higher than that in wild-type controls^[1].
PTO-41 (intravenous injection) exhibits efficient blood-brain barrier penetration and rapid brain clearance in healthy ICR mice, with an initial brain uptake of 9.04 % ID/g at 2 min post-injection and a clearance rate of 5.0^[1].

Guide (The following is our recommended experimental protocol. This protocol serves only as a reference guide, and specific operations should be adjusted according to your actual needs).
1. Preparation of PTO-41 Stock Solution
Weigh PTO-41 and dissolve it in DMSO to prepare a 25.0 μM stock solution. Store the solution at -20℃ away from light.
2. Fluorescence Binding Assay for Aβ Species
2.1 Dilute PTO-41 with PBS (pH 7.4) to a final concentration of 500 nM in a quartz cuvette.
2.2 Add pre-prepared Aβ42 monomers/oligomers/aggregates (final concentration 1.5 μM, i.e., probe:Aβ ≈ 1:3).
2.3 Mix well and incubate at room temperature for an appropriate period of time (usually several minutes until equilibrium is reached).
2.4 Measure fluorescence: Ex = 570 nm, Em scan = 600-800 nm (record the intensity at 680 nm).
2.5 Use PTO-41/PBS without Aβ as the blank for calibration.
3. In Vivo NIR Fluorescence Imaging in Mice
3.1 Reagent Preparation (Injection Solution):
Solvent system: 15% DMSO + 15% Cremophor EL + 70% PBS
The final concentration of PTO-41 is calculated based on 4 mg/kg body weight (100 μL is typically used for mice)
Prepare immediately before use, shake well and let stand for 20 min to ensure stable dissolution
3.2 Animal Imaging
3.2.1 Use 4-month-old female APP/PS1 transgenic mice and age-matched WT control mice (n=3-4).
3.2.2 Shave the head hair before the operation to reduce background interference.
3.2.3 Inject 100 μL of PTO-41 solution via tail vein.
3.2.4 Image acquisition using the IVIS Spectrum system:
Ex = 570 nm / Em = 680 nm
Time points for acquisition: before injection, 30, 60, 120, 240, 360 min
Draw ROIs on the brain in the software (Living Image 4.2.1) for quantitative analysis.