Synthesis of Azido-Functionalized Folate
Preparation of PLA-PEG-FA copolymer was started with the synthesis of
OH-PLA-PEG-COOH according to the method described by Hami et al (Hami,
Amini, Ghazi-Khansari, Rezayat, & Gilani, 2014b). Briefly, definite
amounts of lactide monomers was added to HO-PEG-COOH under dry argon,
then the reaction was continued at 140 °C for 24 h in the presence of
stannous octoate (Sn(Oct)2) as catalyst. The mixture was
dissolved in chloroform and precipitated by a mixture of ether and
methanol (v/v= 1:1). Then, the HO-PLA-PEG-COOH obtained as precipitate
was dried. This obtained polymer was dissolved in DCM with DCC (1.2
mmol) and NHS (0.6 mmol). The product was stirred at 0 °C and 25°C for 1
h and 24 h respectively. Triethylamine (TEA) and propargylamine (0.6
mmol) were added into the above product. Next, the mixture was stirred
at 25°C for another 24 h. The product (HO-PLA-PEG-alkyne copolymer) was
precipitated in cold ether, filtered and dried at 30 °C under vacuum.
Then, the HO-PLA-PEG-alkyne copolymer (0.1 mmol) was conjugated with
acryloyl chloride (C3H3ClO) (0.2 mmol)
in dry toluene containing triethylamine
(C6H15N) (0.2 mmol). The sample was
stirred for 10 h at 80 °C. After that, the product was cooled to 25°C,
filtered and precipitated in n-hexane then dried in vacuum oven to
produce acrylate-PLA-PEG-alkyne copolymer. Acrylate-PLA-PEG-Folic acid
and Acrylate-PLA-PEG-Glucose were synthesized stepwise by the addition
of Acrylate-PLA-PEG-alkyne copolymer (0.1 mmol) and Azido-functionalized
folate and Azido-functionalized glucose in 30 mL aq.
NH4HCO3 (10 mM) separately. Then, sodium
ascorbate and CuSO4 solutions were added to
acrylate-PLA-PEG-alkyne copolymer and stirred with a rotator at 25 °C
for 24 h. Next, the product was filtered with a 0.22 μm membrane filter.
The reaction solutions were diluted with sufficient NaCl aqueous
solution, and then extracted several times by dichloromethane. The
resulting products were concentrated under vacuum and precipitated in
cold ether. Finally, acrylate-PLA-PEG-FA copolymer and
acrylate-PLA-PEG-Glu copolymers were dried under vacuum.