PAPER IN FOREFRONT Highly parallel remote SPR detection of DNA hybridization by micropillar optical arrays Karim Vindas 1 & Loic Leroy 1 & Patrick Garrigue 2 & Silvia Voci 2 & Thierry Livache 1,3 & Stéphane Arbault 2 & Neso Sojic 2 & Arnaud Buhot 1 & Elodie Engel 1 Received: 6 December 2018 /Revised: 24 January 2019 /Accepted: 7 February 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Remote detection by surface plasmon resonance (SPR) is demonstrated through microstructured optical arrays of conical nanotips or micropillars. Both geometries were fabricated by controlled wet chemical etching of bundles comprising several thousands of individual optical fibers. Their surface was coated by a thin gold layer in order to confer SPR properties. The sensitivity and resolution of both shapes were evaluated as a function of global optical index changes in remote detection mode performed by imaging through the etched optical fiber bundle itself. With optimized geometry of micropillar arrays, resolution was increased up to 10 -4 refractive index units. The gold-coated micropillar arrays were functionalized with DNA and were able to monitor remotely the kinetics of DNA hybridization with complementary strands. We demonstrate for the first time highly parallel remote SPR detection of DNA via microstructured optical arrays. The obtained SPR sensitivity combined with the remote intrinsic properties of the optical fiber bundles should find promising applications in biosensing, remote SPR imaging, a lab-on- fiber platform dedicated to biomolecular analysis, and in vivo endoscopic diagnosis. Keywords Micropillar arrays . Surface plasmon resonance . Optical fiber bundles . Remote detection . DNA hybridization Introduction In the medical field, for diagnoses’ purpose, a large amount of biochemical parameters are analyzed. Those analyses are per- formed in first intention on accessible samples like feces, urine, saliva, and blood. But for several pathologies, the de- termination of the biochemical disorder is not sufficient and the sites of the diseases or dysfunctions must be investigated. In those cases, several technics can be implemented like X-ray [1], echography [2], magnetic resonance imaging [3], and endoscopy [4]. Unfortunately, the external aspect of the tis- sues is not always satisfactory for relevant diagnoses. In those cases, the physician will perform biopsies. Samples are then analyzed in terms of cytology and biochemical properties. This process is time consuming and particularly invasive. Optical fibers allow developing minimally invasive re- mote optical detection. Devices based on optical fibers are usually flexible and may be inserted into the body. Moreover, thousands of optical fibers may be arranged in coherent bundles [5]. In addition to remote imaging and enabling the collection of dense data simultaneously, this highly organized array leads to easy and reproducible fab- rication of micro/nanostructured surfaces by a wet-etching step [6–9]. Optical fiber bundles may thus be transformed to present arrays of nanotips, micro/nanowells, microwells surrounded by ultrasharp tips, or nanoparticles at their sur- faces [6–11]. These different shapes exhibit remarkable op- tical properties applied for high-density sensing arrays [7, 12], single-molecule detection [13, 14], surface-enhanced raman scattering spectroscopy [10, 15], or fluorescence cor- relation spectroscopy [16]. These properties can be used to perform biomolecular analysis [17]. In particular, the use of surface plasmons is an efficient way to detect local optical index variations induced by biological interactions [18]. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00216-019-01689-2) contains supplementary material, which is available to authorized users. * Elodie Engel elodie.engel@univ-grenoble-alpes.fr 1 CEA, CNRS, INAC-SyMMES, Université Grenoble Alpes, 38000 Grenoble, France 2 INP-Bordeaux, ISM, CNRS UMR5255, Université de Bordeaux, 33607 Pessac, France 3 Present address: Aryballe Technologies, CEA/MINATEC, 38040 Grenoble Cedex 09, France Analytical and Bioanalytical Chemistry https://doi.org/10.1007/s00216-019-01689-2