Core–Shell Nanostructured Fe3O4–Poly(styrene-co-vinylbenzyl chloride) Grafted PPI Dendrimers Stabilized with AuNPs/PdNPs for Efficient Nuclease Activity

Four different novel magnetic core–shell nanocomposites stabilized with Au/Pd nanoparticles (NPs) were prepared by a simple procedure and demonstrated their catalytic activity for effective cleavage of pBR322 DNA. Initially, the Fe3O4–poly­(styrene-divinylbenzene-vinylbenzyl chloride) (ST-DVB-VBC) matrix functionalized with 3-aminobenzoic acid was prepared and grafted with PPI-G(2) and PPI-G(3) dendrimers. Each core–shell matrix was immobilized with AuNPs and PdNPs separately. The resulting composites were characterized by FT-IR, UV–vis, SEM, TEM, XRD, VSM, XPS, Raman, and TGA. The magnetic core–shell nanocomposites at concentrations from 30 to 50 μM were employed separately to study DNA cleavage by agarose gel electrophoresis. Among the four magnetic core–shell nanocomposites, Fe3O4–poly­(ST-DVB-VBC)–PPI-G­(3)–AuNPs showed higher activity than others for DNA cleavage, and formed Form-II and -III DNA. When the concentration of Fe3O4–poly­(ST-DVB-VBC)–PPI-G­(3)–AuNPs was increased from 40 to 45 and 45 to 50 μM, Form-III (linear) DNA was observed with 10 and 22%, respectively, in addition to Form-II. This observation suggests formation of linear DNA from the supercoiled DNA via nicked DNA-intermediated consecutive cleaving process. The magnetic core–shell nanocomposites were stable and monodispersed, and exhibited rapid magnetic response. These properties are crucial for their application in biomolecular separations and targeted drug-delivery in the future.