Polymeric Signal Amplifiers in Biosensing

Early detection of ultra-low concentrations of biomarkers or environmental toxins in bodyfluids, food or water samples is vital for disease diagnosis, food safety and environmental monitoring. However, traditional technologies are tedious, time-consuming and require expensive instruments and well-trained personnel. Thus, there is an increasing demand to develop a facile and rapid sensing strategy to overcome these limitations. Signal amplification is important in early detection. Among these emerging signal amplification methods, polymer based signal amplification is promising due to the structure of polymer and easy chemical modification. In this topic, we developed four types of bioseners for ultrasensitive detection of biomarker and toxin, as well as monitoring of cell growth. (1) We fabricated a novel signal cascade strategy via an ultrasensitive polymeric sensing system (UPSS) composed of gold nanoparticle (gNP)-decorated polymers, which enables gNP aggregation in polymeric network and electrical conductance change upon specific aptamer-based biomolecular recognition. The biomolecular recognition induced polymeric network shrinkage responses as well as dose-dependent responses of the UPSS are validated using in situ real-time atomic-force microscopy, representing the first instance of real-time detection of biomolecular binding-induced polymer shrinkage in soft matter. (2) We constructed an ultrasensitive biosensor where a C-reactive protein (CRP) aptamers based molecular recognition core, and an in situ synthesized conductive polypyrrole nanofiber mesh based signal amplifier were integrated. Serum CRP levels were quantitatively analyzed through monitoring the conductance change caused by polymeric network shrinkage upon the aptamer-CRP binding. A commercial CRP ELISA kit was used to perform side-by-side measurement of serum CRP in melanoma patients. (3) We prepared a dual-function polymer scaffold containing thermosensitive polymers, silver flakes-decorated polymers and gNP-decorated polymers to monitor cancer cells growth. This biocompatible polymer scaffold allows cancer cells to grow on it and can detect cancer cells via silver flakes and gNP aggregation in polymeric network and electrical conductance change upon the cancer cells growth. (4) We fabricated a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) based, highly-responsive flexible composite nanofiber signal amplifier for ultrasensitive detection of thrombin and IL-17 A. The serum IL-17 A in melanoma patients were quantified by this sensor.