Capping agent-free gold nanostars show greatly increased versatility and sensitivity for biosensing

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Materials Science

Background:

• Gold nanostars are promising for plasmonic biosensing.
• Capping agents can interfere with nanostar functionality and sensing capabilities.

Purpose of the Study:

• To evaluate the plasmonic biosensing performance of capping agent-free gold nanostars.
• To investigate the impact of capping agent removal on nanostar sensitivity and detection limits.

Main Methods:

• Gold nanostars were synthesized and their capping agent (polyvinylpyrrolidone, PVP) was removed using sodium borohydride.
• Refractive index sensitivity was measured for both PVP-coated and PVP-free nanostars.
• Functionalization with biotinylated thiol and streptavidin was performed, followed by detection of prostate specific antigen (PSA) using refractive index sensing and a sandwich assay.

Main Results:

• PVP-free gold nanostars exhibited a refractive index sensitivity of 474 nm/RIU, a fourfold increase compared to PVP-coated nanostars (98 nm/RIU).
• Detection of streptavidin achieved a limit of detection as low as 0.1 pM.
• PSA detection in serum yielded a limit of detection of 100 pM, with a sandwich assay achieving 10(-17) M sensitivity.

Conclusions:

• Removal of capping agents significantly enhances the plasmonic biosensing capabilities of gold nanostars.
• Capping agent-free gold nanostars offer superior sensitivity and lower detection limits for biomarker detection.
• These advanced nanostars hold potential for applications in diagnostics, catalysis, and drug delivery.