LAUSR

In this work, a simple on-line preconcentration method for quantitative detection of pepsin was realized by using the binary mixed polymer brushes coated capillary with switchable properties towards protein adsorption. Firstly, the binary mixed polymer brushes were prepared by grafting poly(2-methyl-2-oxazoline) and poly(4-vinylpyridine) onto the inner wall of the capillary through polydopamine anchor. Then the coatings were characterized by X-ray photoelectron spectrometer and electroosmotic flow measurement. The results indicated that the composition of coating could be controlled by varying the feed ratio of poly(2-methyl-2-oxazoline) to poly(4-vinylpyridine) and the inner surface charge could be tuned toward the change of pH and ionic strength. The results showed when poly(2-methyl-2-oxazoline)/poly(4-vinylpyridine) mass ratio was 80/20, the highest on-line preconcentration effect was obtained and the sensitivity enhancement factor was 6.3. Moreover, satisfactory sensitivity (limit of detection: 7.5 ng/mL) and good repeatability were obtained with on-line preconcentration method. The polymer coated capillary was still stable for on-line preconcentration and detection of pepsin after 50 consecutive runs. Lastly, the proposed method was used successfully to on-line preconcentrate pepsin in saliva matrix. This article is protected by copyright. All rights reserved.