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Photopolymer flexographic printing plate is a new photopolymeric material used for microdevices fabrication. This work demonstrates that a photopolymer flexographic master mold can be used for the fabrication of PDMS (polydimethylsiloxane) microdevices by a multi-step manufacturing process. The methodology entails three main fabrication steps: (1) a photopolymer flexographic printing plate mold (FMold) is generated by UV exposure through a transparent film, (2) an epoxy resin mold (ERmold) is fabricated by transferring the features of the photopolymer mold and (3) a PDMS microdevice is manufactured from the epoxy resin mold. The characterization of the manufactured PDMS microdevices was performed using scanning electron microscopy (SEM) and profilometry. Results showed high accuracy in the replication of the profiles. To show the feasibility of the fabrication process a microdevice for microdroplet generation was designed, manufactured and tested. Hence, the manufacturing process described in this work provides an easy, robust, and low-cost strategy that facilitates the scaling-up of microfluidic devices without requiring any sophisticated equipment. Fil: Olmos Carreno, Carol Maritza. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Vaca Mora, Andrea Vanessa. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rosero, Gustavo. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina Fil: Peñaherrera Pazmiño, Ana Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina Fil: Pérez Sosa, Camilo José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina Fil: de Sá Carneiro, Igor. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina Fil: Vizuete, Karla. Universidad de Las Fuerzas Armadas Espe; Ecuador Fil: Arroyo, Carlos R.. Universidad de Las Fuerzas Armadas; Ecuador Fil: Debut, Alexis. Universidad de Las Fuerzas Armadas; Ecuador Fil: Perez, Maximiliano Sebastian. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina Fil: Cumbal, Luis. Universidad de Las Fuerzas Armadas; Ecuador Fil: Lerner, Betiana. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Haedo; Argentina

Polydimethylsiloxane (PDMS) is a well-known biocompatible polymer employed for many applications in the biomedical field. In this study, the biocompatibility and versatility of PDMS was tested setting up a microdevice devoted to the purification and analysis of nucleic acids. The PDMS microdevice was demonstrated to successfully fulfill all requirements of genetic analyses such as genotyping and pathogen DNA identification both in multiplex and real-time PCR, suggesting the possibility to carry out a molecular test directly on-chip. Moreover, the PDMS microdevice was successfully applied to the purification and detection of disease biomarkers, such as microRNAs related to cancer or heart disease. On-chip microRNA purification was demonstrated starting from clinically relevant samples, i.e. plasma, serum, tissue biopsies. Significantly, the purification and the transcription of microRNA into cDNA occur in the same PDMS chamber, saving time and labor for the overall analysis. Again, the PDMS microdevice was confirmed as a notable candidate for compact, rapid, easy-to-use molecular tests.

The isolation and analysis of circulating biomarkers, the main concern of liquid biopsy, could greatly benefit from microfluidics. Microfluidics has indeed the huge potentiality to bring liquid biopsy into the clinical practice. Here, two polydimethylsiloxane (PDMS)-based microdevices are presented as valid tools for capturing microRNAs biomarkers from clinically-relevant samples. After an extensive study of functionalized polydimethylsiloxane (PDMS) properties in adsorbing/eluting microRNAs, the best conditions were transferred to the microdevices, which were thoroughly characterized. The channels morphology and chemical composition were measured, and parameters for the automation of measures were setup. The best working conditions were then used with microdevices, which were proven to capture microRNAs on all channel surfaces. Finally, microfluidic devices were successfully validated via real-time PCR for the detection of a pool of microRNAs related to non-small cell lung cancer, selected as proof-of-principle. The microfluidic approach described here will allow a step forward towards the realization of an efficient microdevice, possibly automated and integrated into a microfluidic lab-on-a-chip with high analytical potentialities.

A reliable clinical assay based on circulating microRNAs (miRNAs) as biomarkers is highly required. Microdevices offer an attractive solution as a fast and inexpensive way of concentrating these biomarkers from a low sample volume. A previously developed polydimethylsiloxane (PDMS) microdevice able to purify and detect circulating miRNAs was here optimized. The optimization of the morphological and chemical surface properties by nanopatterning and functionalization is presented. Surfaces were firstly characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), fluorescamine assay and s-SDTB (sulphosuccinimidyl-4-o-(4,4-dimethoxytrityl) butyrate) assay and subsequently tested for their capacity to adsorb a fluorescent miRNA. From our analysis, modification of surface charge with 0.1% APTMS ((3-Aminopropyl)trimethoxysilane) and 0.9% PEG-s (2-[Methoxy-(polyethyleneoxy)propyl]trimethoxysilane) performed at 60 °C for 10 min was identified as the best purification condition. Our optimized microdevice integrated with real-time PCR detection, was demonstrated to selectively purify both synthetic and natural circulating miRNAs with a sensitivity of 0.01 pM.