Bioreducible Zinc Coordinative PEI

For DDAC synthesis, 2,2’-dipicolylamine (DPA), alpha,alpha'-dichloro-p-xylene (Dx), 5-amino-1-pentanol (AP), chlorpromazine (CPZ) and amiloride hydrochloride (AM) were purchased from Heowns Biochem. Technologies (Tianjin, China). Disufide monomer cystamine bisacylamide (CBA) was prepared according to the literature.1 Methyl-β-cyclodextrin (MβCD) and branched PEI1.8k was purchased from Aladdin (Shanghai, China). The reagents (analytical reagent grade) were used as received. Dichloromethane, anhydrous methanol, ethanol, anhydrous ethyl ether, ethyl acetate (EA), potassium carbonate (K2CO3) and 1,6-diaminohexane were obtained from the Sixth Chemical Reagent Company (Tianjin, China). Fetal bovine serum (FBS), various cell culture media, trypsin-EDTA, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), dimethyl sulphoxide (DMSO), phosphate buffered saline (PBS, 10 mM, pH 7.2~7.4), sodium acetate (pH 5.2 ± 0.1, 50 mM), 4’,6-diamidino-2-phenylindole (DAPI) and fluorescein isothiocyanate (FITC) were purchased from Dingguo Biotech. Co. Ltd (Tianjin, China).

Synthesis of DDAC monomer and Zn-PD polymers

As the routing in Figure 1, to synthesize DDAC, DxDA with one residual benzyl chloride was first prepared. Dx (2.80 g, 16 mmol) and DPA (1.59 g, 8 mmol) were orderly dissolved in 20 mL of dichloromethane, afterwards anhydrous K2CO3 (5.52 g, 40 mmol) was added to the mixture. The reaction was maintained at room temperature for 48 h under N2 atmosphere. Then silica gel column purification was conducted with CH2Cl2:MeOH (20:1, v/v) elution to give DxDA as yellowish oil (1.94 g, 72% yield). For DxDA-AP synthesis, AP (1.04 g, 10 mmol) and K2CO3 (1.66 g, 12 mmol) were mixed with 8 mL of ethanol, followed by dropwise adding DxDA (0.84 g, 2.4 mmol). Then the mixture was stirred at 60 oC for 12 h, and precipitated with deionized water three times. For further purification, product suspension in water was extracted with CH2Cl2 (100 mL), afterwards the organic phase was dried over anhydrous Na2SO4 and concentrated under vacuum to give DxDA-AP (0.68 g, 71% yield). To synthesize DDAC, DxDA-AP (0.3 g, 0.75 mmol) and CBA (0.39 g, 1.5 mmol) were mixed in 5 mL of methanol, and the reaction occurred at 40 oC for 48 h. Then the product was purified using silica gel column with EA:MeOH (4:1, v/v) as the eluent. The final DDAC was obtained as yellowish solid (0.18 g, 36% yield). DDAH was obtained by DxDA-AP and 1,6-diaminohexane reaction. The reaction and purification processes were kept the same as the synthesis of DDAC mentioned above.

For Zn-PD and Zn-PH synthesis, calculated DDAC (or DDAH), Zn(NO3)2·6H2O and PEI1.8k were mixed in methanol, then the reaction continued at 60 oC for 48 h (Table S1). Afterwards, the mixture was concentrated under vacuum to obtain Zn-PDm and Zn-PHm polymers. “m” represents the amount of Zn-DDAC modified on one PEI1.8k molecule. To synthesize FITC-Zn-PD4 and FITC-Zn-PH4, PEI1.8k was modified with FITC first, then DDAC (or DDAH) and Zn(NO3)2·6H2O were added to react as above.

For Zn-PLD synthesis, Zn-DDAC (0.01 mmol), ε-polylysine (PLL, Mw < 5000 Da, 16 mg) and triethylamine (30 µL) were dissolved in 1 mL of methanol, then the reaction continued at 60 oC for 48 h. The product was precipitated in cold diethyl ether three times and dried under vacuum for 24 h.