Phenylboronic acid conjugated PAMAM G4 dendrimers augmented usnic acid delivery to gastric cancer cells

Here we report on the synthesis, characterization, and biological evaluation of Siglec's targeted G4 PAMAM dendrimers loaded with usnic acid (UA). Siglec's targeted G4 dendrimers were obtained by conjugation of 4-carboxy phenylboronic acid (PBA) to the periphery of the G4 PAMAM dendrimer (PBA-PAMAM). UA-loaded PBA-PAMAM dendrimers (UA@PBA-PAMAM) showed average particle size (18 nm) without any sign of aggregation with amorphous nature, stability of the drug, and PBA-mediated anticancer efficacy. The UA@PBA-PAMAM dendrimer formulation showed a site-specific drug release profile. After 12 h, 17.6% and 95.7% of UA was released from UA@PBA-PAMAM dendrimer formulation in pH 7.4 and pH 5.0, respectively. In vitro anticancer results suggested the no cytotoxicity of G4 dendrimers after PBA conjugation. The cell viability of AGS cells was observed as 88.9 ± 0.7% (12 h) and 50.4 ± 1.9% (24 h) after pure UA treatment and 37.3 ± 0.6% (12 h) and 14.4% ± 1.2 (24 h) after treatment with UA@PBA-PAMAM. The pure UA had IC₅₀ values of 44.9 ± 3.1 μg/mL (for 12 h) and 8.2 ± 1.1 μg/mL (for 24 h) while UA@PBA-PAMAM had an IC₅₀ value of 8.4 ± 0.3 μg/mL (for 12 h) and 2.7 ± 0.4 μg/mL (for 24 h) in AGS cells. As a result of cytotoxicity studies, the dendrimer formulation UA@PBA-PAMAM maintained its effectiveness and was able to produce a long-term anticancer effect over time compared to the pure UA dose. The PBA-PAMAM dendrimer also significantly enhanced the cellular internalization in AGS gastric cancer cells. The new PBA-PAMAM design appears to be suitable nanocarriers for the UA to deliver gastric cancer cells.