Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide

• A sensitive and versatile SPR biosensor was constructed for detection of pig IgG.
• Biofunctional gold nanostars were used to amplify the response signals.
• The strategy employed carboxyl-functionalized graphene oxide as biosensing substrate.
• The detection limit of the proposed biosensor is 32 times lower than that of graphene oxide-based biosensor.

A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL−1, which is 32 times lower than that of graphene oxide-based biosensor.

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