Synthesis of CBA-DSP-PEI

CBA-PEI

Add 0.625 g PEI 1.8K and 52 mg CBA to a flask
Add 5 ml MeOH
Stire at 40 oC for 72 hrs
Dialyse vs 7000 Da membrane
Freeze-dry

Synthesis of SS-PEI using DTPA/EDC/NHS and PEI (800 Da)

SS-PEI (MM ww = 8.5 kDa, PDI = 1.8)

NHS: N-Hydroxysuccinimide

EDC: 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide

DTPA: 3,3'-dithiobispropanoic acid

Add DTPA (2 mmol, 0.42 g), LWPEI (2 mmol, 1.60 g), EDC (5 mmol, 0.96 g), and NHS (5 mmol, 0.57 g) to a flask

Add 5ml of 2-(N-morpholino)ethanesulfonic acid (MES) buffer (pH 6.5)

Reaction at room temperature under nitrogen atmosphere for 2 days, Yielding a viscous solution.
Purify the resulting solution by exhaustive dialysis (3500 g/mol cut-off) with 50 mM NaCl solution in water (3 × 5 L) for 3 days
Freeze dry to get dry powder
Yield is 25%

Cy5.5-labeled SS-PEI can be prepared by coupling NHS-activated Cy5.5 with SS-PEI.

Add SS-PEI (50 mg) and NHS-Cy5.5 (200 nmol in DMSO)  into a reaction flask and stir in MES buffer (pH 6.5, 5 mL).

Let reaction proceed for 2 days at room temperature.

Purify the resulting solution by exhaustive dialysis (3500 g/mol cut-off) for 3 days.

Freeze drying to get Cy5.5-labeled SS-PEI solid powder

yield is 78%.

The content of Cy5.5 in SS-PEI (65.5 pmol/μμg) is calculated using a calibration curve derived from a series of Cy5.5 solutions at different concentrations.