RESEARCH PAPER Combined negative dielectrophoresis with a flexible SERS platform as a novel strategy for rapid detection and identification of bacteria Ariadna B. Nowicka 1 & Marta Czaplicka 1 & Tomasz Szymborski 1 & Agnieszka Kamińska 1 Received: 10 November 2020 /Revised: 25 December 2020 /Accepted: 7 January 2021 # Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract Surface-enhanced Raman spectroscopy (SERS) is a vibrational method successfully applied in analytical chemistry, molecular biology and medical diagnostics. In this article, we demonstrate the combination of the negative dielectrophoretic (nDEP) phenomenon and a flexible surface-enhanced Raman platform for quick isolation (3 min), concentration and label-free identi- fication of bacteria. The platform ensures a strong enhancement factor, high stability and reproducibility for the SERS response of analyzed samples. By introducing radial dielectrophoretic forces directed at the SERS platform, we can efficiently execute bacterial cell separation, concentration and deposition onto the SERS-active surface, which simultaneously works as a counter electrode and thus enables such hybrid DEP-SERS device vibration-based detection. Additionally, we show the ability of our DEP-SERS system to perform rapid, cultivation-free, direct detection of bacteria in urine and apple juice samples. The device provides new opportunities for the detection of pathogens. Keywords Surface-enhancedRamanspectroscopy . SERS . FlexibleSERS platform . Dielectrophoresis . Escherichia coli . Urine Introduction Surface-enhanced Raman spectroscopy (SERS) combines several advantages of Raman spectroscopy: unique spectral vibrational fingerprints of the analyzed molecules, non- destructive analysis, the acceptability of samples containing water, simplicity of sample preparation, and ultrasensitive de- tection of different analytes at the same time (selectivity) [1–6]. To enhance the Raman signal, even up to a factor of 10 12 [7, 8], a special SERS platform, usually made of silicon, glass or another brittle material with metal nanostructure sur- faces or metallic nanoparticles, is required [9–13]. The Raman signal enhancement is attributed to two main mechanisms: electromagnetic (EM) and charge transfer (CT) enhancement [14, 15]. This vast enhancement of Raman scattering allows SERS technology to be used with analytes in low concentrations [16], for the characterization of biological systems and micro- organisms [17–19] and as a diagnostic tool for environmental and biomedical analysis [10, 20–27]. Rapid detection of these biological compounds is essential for monitoring the quality of food and water, as well as early detection and diagnosis of diseases [24, 28]. Typically, the molecules of interest are dis- solved and then adsorbed on the SERS-active substrate. In the case of bacteria, an essential preliminary step in the process is the isolation and concentration of bacterial cells before their subsequent analysis. To separate and deposit an adequate amount of microorganisms and aggregate them in one place on the SERS platform, the following methods can be used: (i) Mechanical, which involves the use of membranes with appropriate pore sizes, capable of stopping microorgan- isms or cancer cells on their surface [29] (ii) Magnetic separation/trapping: by using magnetic nano- particles, which due to appropriate chemical modifica- tion are capable of attaching to bacterial or cancer cells [30, 31] (iii) Chemical modifications of the surface and the microor- ganisms themselves: using polymer coatings, antibodies or other materials [18] Ariadna B. Nowicka and Marta Czaplicka contributed equally to this work. * Tomasz Szymborski tszymborski@ichf.edu.pl * Agnieszka Kamińska akamin@ichf.edu.pl 1 Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland Analytical and Bioanalytical Chemistry https://doi.org/10.1007/s00216-021-03169-y