{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T02:41:42Z","timestamp":1768704102713,"version":"3.49.0"},"reference-count":15,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2017,3,16]],"date-time":"2017-03-16T00:00:00Z","timestamp":1489622400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NSFC grants","award":["51673012"],"award-info":[{"award-number":["51673012"]}]},{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2016YFF0203703"],"award-info":[{"award-number":["2016YFF0203703"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Key Program of Beijing Municipal Science and Technology Commission","award":["D161100002116002"],"award-info":[{"award-number":["D161100002116002"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Ractopamine (RCT) is banned for use in animals in many countries, and it is urgent to develop efficient methods for specific and sensitive RCT detection. A label-free indirect competitive surface plasmon resonance (SPR) immunosensor was first developed with a primary antibody herein and then improved by a secondary antibody for the detection of RCT residue in swine urine. Meanwhile, a pre-incubation process of RCT and the primary antibody was performed to further improve the sensitivity. With all the key parameters optimized, the improved immunosenor can attain a linear range of 0.3\u201332 ng\/mL and a limit of detection (LOD) of 0.09 ng\/mL for RCT detection with high specificity. Furthermore, the improved label-free SPR immunosenor was compared thoroughly with a conventional enzyme-linked immunosorbent assay (ELISA). The SPR immunosensor showed advantages over the ELISA in terms of LOD, reagent consumption, analysis time, experiment automation, and so on. The SPR immunosensor can be used as potential method for real-time monitoring and screening of RCT residue in swine urine or other samples. In addition, the design using antibody pairs for biosensor development can be further referred to for other small molecule detection.<\/jats:p>","DOI":"10.3390\/s17030604","type":"journal-article","created":{"date-parts":[[2017,3,16]],"date-time":"2017-03-16T11:24:28Z","timestamp":1489663468000},"page":"604","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["An Improved Label-Free Indirect Competitive SPR Immunosensor and Its Comparison with Conventional ELISA for Ractopamine Detection in Swine Urine"],"prefix":"10.3390","volume":"17","author":[{"given":"Sai","family":"Wang","sequence":"first","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]},{"given":"Shuai","family":"Zhao","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]},{"given":"Xiao","family":"Wei","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]},{"given":"Shan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]},{"given":"Jiahui","family":"Liu","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]},{"given":"Yiyang","family":"Dong","sequence":"additional","affiliation":[{"name":"Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China"}]}],"member":"1968","published-online":{"date-parts":[[2017,3,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1016\/0306-9877(91)90212-H","article-title":"Cortisol and immunity","volume":"34","author":"Jefferies","year":"1991","journal-title":"Med. 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