title: Strategy for sensor based on fluorescence emission red shift of conjugated polymers: applications in pH response and enzyme activity detection.
abstract: A new strategy was developed and applied in monitoring pH response and enzyme activity based on fluorescence emission red shift (FERS) of the conjugated polymer PPP-OR10 induced by the inner filter effect (IFE) of nitrobenzene derivatives. Neutral poly(p-phenylenes) functionalized with oligo(oxyethylene) side chains (PPP-OR10) was designed and synthesized by the Suzuki cross-coupling reaction. Nitrobenzene derivatives display different light absorption activities in the acidic or basic form due to adopting different electron-transition types. When environmental pH is higher than their pK(a) values, nitrobenzene derivatives exhibit strong absorbance around 400 nm, which is close to the maximal emission of polymer PPP-OR10. As a result, the maximal emission wavelength of PPP-OR10/nitrobenzene derivatives red shifts with the pH value increasing. Apparently, the IFE plays a very important role in this case. A new method has been designed that takes advantage of this pH-sensitive platform to sensor α-chymotrypsin (ChT) based on the IFE of p-nitroaniline, since the absorption spectrum of p-nitroaniline, the ChT-hydrolyzed product of N-benzoyl-L-tyrosine-p-nitroaniline (BTNA), overlaps with the emission spectrum of PPP-OR10. In addition, the present approach can detect α-chymotrypsin with a detection limit of 0.1 μM, which is lower than that of the corresponding absorption spectroscopy method. Furthermore, the pH response and enzyme detections can be carried out in 10% serum, which makes this new FERS-based strategy promising in applications in more complex conditions and a broader field.
authors.affiliation: Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi'an 710062, PR China. yltang@snnu.edu.cn
authors.forename: Yanli
authors.initials: Y
authors.lastname: Tang
authors.forename: Yue
authors.initials: Y
authors.lastname: Liu
authors.forename: Ali
authors.initials: A
authors.lastname: Cao
mesh_terms: D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009578:Nitrobenzenes / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D009578:Nitrobenzenes; D011108:Polymers; D002918:Chymotrypsin; C117608:alpha-chymotrypsin