Poly-L-histidine coated microfluidic devices for bacterial DNA purification without chaotropic solutions Athina S. Kastania 1,2 & Panagiota S. Petrou 3 & Christos-Moritz Loukas 1 & Evangelos Gogolides 1 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract We present a disposable polymeric microfluidic device capable of reversibly binding and purifying Salmonella DNA through solid phase extraction (SPE). The microfluidic channels are first oxygen plasma treated and simultaneously micro-nanotextured, and then functionalized with amine groups via modification with L-histidine or poly-L-histidine. L-Histidine and poly-L- histidine bind on the plasma treated chip surface, and are not detached when rinsing with DNA purification protocol buffers. A pH-dependent protocol is applied on-chip to purify Salmonella DNA, which is first bound on the protonated amines at a pH (5.0) lower than their pKa of surface amine-groups which is 6.0 and then released at a pH higher than the pKa value (10.5). It was found that modification with poly-L-histidine resulted in higher surface density of amine groups onto microfluidic channel. Using the chip modified with poly-L-histidine, high recovery efficiency of at least 550 ng of isolated Salmonella DNA as well as DNA purification from Salmonella cell lysates corresponding to less than 5000 cells or 0.026 ng of Salmonella DNA was achieved. The protocol developed does not require ethanol or chaotropic solutions typically used in DNA purification, which are known inhibitors for downstream operations such as polymerase chain reactions (PCR) and which can also attack some polymeric microfluidic materials. Therefore, the microfluidic device and the related protocol hold promise for facile incorporation in microfluidics and Lab-on-a-chip (LOC) platforms for pathogen detection or in general for DNA purification. Keywords Plasma modification . High surface area . Amine groups . DNA purification . Microfluidics . Poly-L-histidine . L-histidine 1 Introduction Nucleic acid extraction from cells, that includes cell lysis and DNA purification, is indispensable in molecular analysis of several types of samples such as blood, saliva, bacteria cul- tures, food and water. DNA purification is usually combined with DNA pre-concentration prior to analysis of food/water, medical or forensic samples since, if DNA collected from the sample of interest is of high concentration, then the success probability increases for the downstream processes, such as polymerase chain reaction (PCR), DNA sequencing and de- tection (Wilson 1997). DNA purification is currently carried out with methods based on liquid-liquid extraction or solid phase extraction (SPE). Due to the diversity of samples and applications, a variety of protocols and devices (Ali et al. 2017 ; MACHEREY-NAGEL 2018 ; Promega 2018 ; QIAGEN 2018; Thermo Fisher Scientific 2018) is available for extraction including spin columns, beads or magnetic beads (Hatcher et al. 2008; Hawkins 1998; Rittich and Španová 2013), automated robots, microfluidics, Lab-on-a- chip (LOC) (Ali et al. 2017) and Lab on CD (Kinahan et al. 2016; Ye et al. 2018) platforms. The extraction chemistry and the device format selection depends on the source of the DNA sample, the type of DNA, the downstream procedure and the targeted application. Nonetheless, similar procedures and methods are also applied for extraction of cell-free DNA (Conde et al. 2020; Lee et al. 2020; Xu et al. 2019) as well Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10544-020-00497-1) contains supplementary material, which is available to authorized users. * Evangelos Gogolides e.gogolides@inn.demokritos.gr 1 Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, Patriarhou Gregoriou E’ & 27 Neapoleos Str., 153 41 Aghia Paraskevi, Attiki, Greece 2 Department of Chemistry, University of Athens, 157 71 Athens, Greece 3 Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR “Demokritos”, Patriarhou Gregoriou E’ & 27 Neapoleos Str., 153 41 Aghia Paraskevi, Attiki, Greece Biomedical Microdevices (2020) 22:44 https://doi.org/10.1007/s10544-020-00497-1