Fiber optic biosensors comprising nanocomposite multilayered polymer and nanoparticle ultrathin films

Fiber optic probes are attractive for chemical and biosensing applications, but there is a need to improve the precision, reliability, and efficiency of methods used to immobilize the sensing chemistry at the fiber tip. Electrostatic layer-by-layer self-assembly (LBL) is an attractive method for depositing ultrathin film of charged molecules on a wide variety of charged substrates, including optical fibers, and this report describes the application of this nanofabrication technique for building spectroscopic fiber probes employing biomolecular recognition via fluorescent indicators and antibodies. Specifically, fluorescent sensors based on polymer/polymer-dye multilayers, and plasmonic sensors based on polymer/nanoparticle/antibody nanocomposites have been produced and characterized. Multilayer fluorescent films containing bis(2,2´-bipyridine) ´´-methyl-4-carboxybipyridine-ruthenium-N-succinimidyl-ester bis(hexafluoro-phosphate) (Ru(bpy)2(mcbpy)) conjugated to poly(allylamine hydrochloride) (PAH) and Alexa 488^™ conjugated to PAH were combined for an oxygen sensor. In a separate demonstration, gold nanoparticle multilayers were combined with an anti-IgG outer coating to realize a novel surface plasmon resonance (SPR)-based detector. Characterization of sensor performance toward target analytes showed specific and sensitive response over a limited range for both systems. This work provides a basis for rapid, cost-effective, precise, and versatile production of fiber optic sensors using self-assembly, and may be useful for numerous biosensing applications, including probes designed for research and clinical measurements, biodefense, and environmental detection.