Silica nanoparticles coated by poly(acrylic acid) brushes via host-guest interactions for detecting DNA sequence of Hepatitis B virus

Poly(acrylic acid) (PAA) brushes coated onto silica nanoparticles have been widely utilized in bioassays due to their abilities of providing favorable microenvironments and ensuring good biological activities for biomolecules. However, traditional PAA brushes are synthesized by reversible addition fragmentation chain transfer polymerization. Hence, it is generally difficult to control and characterize the molecular weight of the PAA brushes, which may depress the reproducibility and bring more uncertain results. Herein, atom transfer radical polymerization method is employed to synthesize beta-cyclodextrin-cored PAA with uniform and controllable molecular weight. After loading on the surfaces of adamantane-functionalized silica nanoparticles via host-guest interactions, glucose oxidase and probe single strand DNA (ssDNA) are further immobilized on the as-prepared nanoparticles. Meanwhile, capture ssDNA is functionalized on amino modified magnetic beads. In the presence of ssDNA sequence of Hepatitis B Virus (HBV) containing completely matched sequence of both probe and capture ssDNA, a bioconjugate is formed and can be separated by an external magnet. The isolated glucose oxidase can further catalyze glucose into gluconic acid and H2O2, and then reduce HAuCl4 on Au seeds. By monitoring the absorption intensity change of the Au NPs at 530 nm, the proposed biosensor with novel signal amplification probes can be used to detect DNA sequence of HBV with high sensitivity and selectivity in both buffer and serum samples. This developed strategy has presented a new way to construct silica nanoparticles coated by PAA brushes for the fields of clinical diagnosis and other life sciences.