Efficient modification of PAMAM G1 dendrimer surface with β-cyclodextrin units by CuAAC: impact on the water solubility and cytotoxicity

Abstract

The toxicity of the poly(amidoamine) dendrimers (PAMAM) caused by the peripheral amino groups has been a limitation for their use as drug carriers in clinical applications. In this work, we completely modified the periphery of PAMAM dendrimer generation 1 (PAMAM G1) with β-cyclodextrin (β-CD) units through the Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC) to obtain the PAMAM G1-β-CD dendrimer with high yield. The PAMAM G1-β-CD was characterized by ¹H- and ¹³C-NMR and mass spectrometry studies. Moreover, the PAMAM G1-β-CD dendrimer showed remarkably higher water solubility than native β-CD. Finally, we studied the toxicity of PAMAM G1-β-CD dendrimer in four different cell lines, human breast cancer cells (MCF-7 and MDA-MB-231), human cervical adenocarcinoma cancer cells (HeLa) and pig kidney epithelial cells (LLC-PK1). The PAMAM G1-β-CD dendrimer did not present any cytotoxicity in cell lines tested which shows the potentiality of this new class of dendrimers.

Scheme 1. Synthesis of alkynyl-PAMAM G1. Conditions: (i) propargyl bromide, K₂CO₃, anhydrous acetone, 24 h, reflux; (ii) NaOH/HCl, EtOH : H₂O; (iii) EDC, HOBt, DIPEA, DMF, 35 °C, 5 days.

Scheme 2. Synthesis of m-N₃-β-CD. Conditions: (i) TsO₂/NaOH, H₂O, 2 h, RT; (ii) NaN₃, DMF, 80 °C, 48 h.

Scheme 3. Synthesis of PAMAM G1-β-CD. Conditions: “Click” CuSO₄·5H₂O, H₂Asc, DMSO, 80 °C, 48 h.

Fig. 1. ¹H NMR spectrum of PAMAM G1-β-CD in DMSO-d₆.

Fig. 2. Cell viability in different cell lines of PAMAM G1-β-CD dendrimer. The treated cells were cultured in six wells by concentration, and the experiments were performed three times independently. Data are means ± S.D.