Mixed-Generation PAMAM G3-G0 Megamer as a Drug Delivery System for Nimesulide: Antitumor Activity of the Conjugate Against Human Squamous Carcinoma and Glioblastoma Cells

Abstract

Polyhydroxylated dendrimer was synthesized from poly(amidoamine) (PAMAM) dendrimer generation 3 by addition of glycidol ( G3 ^gl ). G3 ^gl megamer was further modified by binding PAMAM G0 dendrimers by activation of G3 ^gl with p-nitrophenylchloroformate, followed by the addition of excess PAMAM G0 and purification using dialysis. The maximum G0 binding capacity of G3 ^gl was 12 in the case when G0 was equipped with two covalently attached nimesulide equivalents. Nimesulide ( N) was converted into N-( p-nitrophenyl) carbonate derivative and fully characterized using X-ray crystallography and spectral methods. Nimesulide was then attached to G0 via a urea bond to yield G0 ^2N . The mixed generation G3 ^gl–G0 ^2N megamer was characterized using ¹H NMR spectroscopy, and its molecular weight was estimated to be 22.4 kDa. The AFM image of G3 ^gl–G0 ^2N deposited on mica demonstrated aggregation of nimesulide-covered megamer. The height of the deposited megamer was 8.5 nm. The megameric conjugate with nimesulide was tested in vitro on three human cell lines: squamous cell carcinoma (SCC-15) and glioblastoma (U-118 MG) overexpressing cyclooxygenase-2 (COX-2), and normal skin fibroblasts (BJ). The conjugate efficiently penetrated into all cells and was more cytotoxic against SCC-15 than against BJ. Moreover, the conjugate produced a strong and selective antiproliferative effect on both cancer cell lines (IC ₅₀ < 7.5 µM).