Optical assay of trypsin using a one-dimensional plasmonic grating of gelatin-modified poly(methacrylic acid)
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ORIGINAL PAPER
Optical assay of trypsin using a one-dimensional plasmonic grating of gelatin-modified poly(methacrylic acid) Ai-Wei Lee 1,2 & Chih-Chia Cheng 3 & Chi-Jung Chang 4 & Chien-Hsing Lu 5,6 & Jem-Kun Chen 2 Received: 4 September 2019 / Accepted: 30 March 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The geometry of resonant absorbers (RA) is varied by tryptic digestion to design a probe platform. The process includes fabrication of a line array of poly(methacrylic acid) (PMAA) brush as an RA, tailed by the immobilization of gelatin. The gelatin-modified PMAA RA is a kind of one-dimensional plasmonic grating, possessing an optical feature with a characteristic absorption peak. The growth of gelatin on PMAA RA resulted in a blue shift of the absorption peak from 465 to 263 nm. Trypsin catalyzes the hydrolysis of peptide bonds, breaking down gelatin into smaller peptides causing the change in geometry of RA. The gelatin of RA was digested in a wide linear range of activity of trypsin from 34 to 1088 U mL−1 resulting in a red shift of the absorption peak of RA from 263 to 474 nm within 10 min. The limit of detection achieved is 11 U mL−1 with ca. 1.9% standard deviation and 101.4% recovery of spiked serum samples. The chemical selectivity of the trypsin assay is evidenced by motoring the changes in a shift of the absorption peak of gelatin-modified PMAA RA using chymotrypsin and horseradish peroxidase. Keywords Polymer brush . Diffuse reflection spectroscopy . Stripe pattern . Gastrointestinal diseases . Atom transfer radical polymerization
Introduction Plasmonic sensors structured by the channels of optical sensing have been considered as a reliable technique for the applications of plethora due to their combined advantages of high throughput detections [1, 2]. Technique of surface-relief gratings on the plasmonic sensors attained
significant importance in the fields of integrated optics and spectral analysis [3]. One-dimensional (1D) gratings for microelectronic applications have been fabricated by varying the key parameters of the period, phase, and orientation [4]. The general procedure for gratings fabricating is the exposing of photoresist film in the I-line exposure followed by polymerization process for transferring the
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04251-5) contains supplementary material, which is available to authorized users. * Chien-Hsing Lu [email protected]
3
Advanced Membrane Materials Research Centre, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei 10607, Taiwan, Republic of China
4
Department of Chemical Engineering, Feng Chia University, 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, Republic of China
5
Department of Obstetrics and Gynecology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China
6
Department of Obstetrics and Gynecology, National Yang-Min
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