Green-synthesized gold nanoparticle-based optical fiber ball resonator biosensor for cancer biomarker detection

Gold nanoparticles (AuNPs) are widely explored for biomedical applications in imaging, theranostic, and diagnostic purposes. The green synthesis of AuNPs is gaining great interest compared to the conventional synthesis methods offering biocompatibility, stability, and large-scale production. On one side, the significant benefit of the green synthesis is in the improved biocompatibility of nanoparticles due to the absence of toxic precursors and unwanted byproducts. This study presented the synthesis of AuNPs using green tea leaves with their further application in biosensing of CD44 cancer biomarker by creating a safe and robust platform on the surface of the ball resonator optical fibers. On the other hand, green-synthesized gold nanoparticles demonstrated dramatic increase in sensitivity of the optical fiber biosensor. The outcome of the investigation presented rapid increase of the sensitivity of the ball resonator optical fiber biosensor up to 13.17 dB in intensity change (1.52 dB for each 10-fold concentration increase over 42.9 aM to 100 nM). The study discussed and quantitatively assessed the detection of CD44 antigen in a wide range of concentrations with the estimated limit of detection (LoD) at 0.111 pM. The fabricated biosensor with incorporated nanoparticles showed marked improvement in sensitivity compared to similar fiber-optic sensing systems, in a label-free real-time miniaturized sensing device.