The integration of molecular imprinting and surface-enhanced Raman scattering for highly sensitive detection of lysozyme biomarker aided by density functional theory Xiaohui Ren a , Ling Yang a , Yuanchao Li a , Emily C. Cheshari a,b , Xin Li a, ⁎ a MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering, State Key Lab of Urban Water Resource and Envi- ronment, Harbin Institute of Technology, Harbin 150090, China b Chemistry and Biochemistry Department, School of Science and Applied Technology, Laikipia University, 20300-1100, Nyahururu, Kenya abstract article info Article history: Received 10 June 2019 Received in revised form 4 November 2019 Accepted 4 November 2019 Available online xxxx Keywords: Surface-enhanced Raman scattering Molecular imprinting Lysozyme Protein Density functional theory Surface-enhanced Raman scattering (SERS) is a powerful bioanalytical technique that opens opportunities for early disease diagnosis and treatment by detecting biomarkers. However, the low sensitivity, selectivity, and re- producibility in the bioanalytical SERS are the main obstacles for clinical use. Herein, we demonstrate a high sen- sitive and selective label-free lysozyme biomarker detection platform based on coupling of SERS with molecular imprinting technique. The hierarchical silver microspheres with dendritic structure are controllably fabricated by a wet-chemical self-assembly approach. Based on selection of surface-active regions by density functional theory (DFT) simulations, a thin MIPs film (thickness b 15 nm) is then grafted on Ag microsphere surface through sur- face imprinting. As a result, the final synthesized Ag@MIPs hybrid exhibits as low as 5 ng mL -1 detection limit for target lysozyme, and high selectivity and reproducibility. Intensive “hot spots” in Ag@MIPs confirmed by Raman mapping give rise to the high-performance SERS. Meanwhile, DFT calculations are employed to investigate the SERS spectra and assist the assignment for the characteristic peaks of lysozyme. We believe that the present study provides a reliable and high-sensitive protocol for label-free protein biomarkers detection. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Accurate and sensitive detection of biomarkers plays a key role in clin- ical diagnosis. Lysozyme, as an important clinical biomarker, has been employed for diagnosing breast cancer [1], chronic dry eye [2], and rheu- matoid arthritis [3], etc. Additionally, lysozyme has various pharmacolog- ical effects to prevent and treat viral and bacterial infections [4], and it is also a promising agent for Acquired Immune Deficiency Syndrome (AIDS) treatment [5]. Until now, various analytical techniques have been developed to detect the lysozyme in different conditions, such as mass spectrometry [6], enzyme-linked immune-sorbent assays [7,8], electrophoretic immunoassay [9], colorimetric sensing [11], fluorescence sensing [12], and so on. However, the use of these reported approaches has some limitations, for instance, a tedious sample pre-treatment, higher cost, lower selectivity, and skilled operator. In order to offer early diagno- sis and warning for potential diseases, developing a rapid, reliable and sensitive analytical technique of lysozyme is very necessary. Surface-enhanced Raman scattering (SERS), a powerful analytical tool derived from Raman spectroscopy, has attracted great interest since it was discovered in 1974 [13]. SERS exhibits outstanding effect in the research of endocrine disrupting chemicals [14,15], organic dyes [16], and living cells [17] because of its excellent photostability, high sensitivity, nondestructive rapid detection, and tremendous multiplexing ability. Benefiting from the fingerprint information of ana- lytical template that can be obtained in aqueous media, SERS is ideal for protein detection [18–22]. As the label-free method, Raman signals are obtained directly when molecules are attached onto the roughened metal surfaces. For most proteins, however, the SERS signals may be lost due to the small Raman cross-sections and poor affinity of target molecules. On the other hand, a strong interaction between analyte and SERS substrate can result in distorted molecular signature. Very re- cently, in 2018, Ren and co-workers presented a survey of SERS detec- tion of lysozyme. They found that the SERS spectra reported by three research groups are quite different, which could be due to denaturation, or to different orientations of absorbed molecules [23]. Moreover, it is very difficult to achieve high-sensitivity detection results in the pres- ence of complex untreated biology samples, which associate with high background noise from interferes [24]. These disadvantages will result in unreliable clinical diagnosis and associated improper treatment [25]. Thus, it is clear that the reliability of bioanalytical SERS is a bottle- neck hindering clinical use. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (xxxx) xxx ⁎ Corresponding author. E-mail address: lixin@hit.edu.cn (X. Li). SAA-117764; No of Pages 8 https://doi.org/10.1016/j.saa.2019.117764 1386-1425/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa Please cite this article as: X. Ren, L. Yang, Y. Li, et al., The integration of molecular imprinting and surface-enhanced Raman scattering for highly sensitive d..., Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, https://doi.org/10.1016/j.saa.2019.117764