Fabrication of scalable poly(N-isopropylacrylamide)/gold nanoparticles composite ring array as LSPR sensor for label-free biosensor application

Abstract

Self-organization facilitates the formation of specific structures as a result of constituent interaction. In this study, the bottom of a 500-nm hole array photoresist template, which was deposited with a hydrophobic atom transfer radical polymerization (ATRP) initiator, was wetted by treatment with oxygen plasma. After the removal of the photoresist template, ring patterns of the ATRP initiator were formed at the interface between the hydrophobic and wetting regions. Poly(N-isopropylacrylamide) (PNIPAAm) was grafted from the ring array of the initiator to immobilize gold nanoparticles (AuNPs) as a uniform ring array on the silicon substrate via repeated swelling/shrinking cycles. The localized surface plasmon resonance (LSPR) peaks of the biotin-anchored AuNP–PNIPAAm composite ring (APCR) were employed to detect streptavidin as biosensors. The coupling of biotin and streptavidin led to asymptotical convergence from rings to disks as well as blue-shifts of the LSPR peaks. Linear correlation between the blue-shift and streptavidin concentration showed a limit of detection of ∼10 nM and a linear range of 10–150 nM for the detection of streptavidin within 30 min. The simple method of combining lithography and plasma technology provides a versatile platform for developing the scalable ring structure of AuNP for highly sensitive and sensitive biosensing.