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This work describes a novel and cost‐effective method of polydimethylsiloxane (PDMS) microchips fabrication by using a printing plate photopolymer called Flexcel as a master mold (Fmold). This method has demonstrated the ability to generate multiple devices from a single master, reaching a minimum channel size of 25 μm, structures height ranging from 53 to 1500 μm and achieving dimensions of 1270 × 2062 mm2, which are larger than those obtained by the known techniques to date. Scanning electron microscopy, atomic force microscopy, and profilometry techniques have been employed to characterize the Fmold and PDMS replicas. The results showed high replication fidelity of Fmold to the PDMS replica. Furthermore, it was proved the reusability of the Fmold. In our study, up to 50 PDMS replicas have been fabricated without apparent degradation of the mold. The feasibility of the resulting PDMS replica was effectively demonstrated using a microfluidic device for enhanced oil recovery analysis. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1433–1442

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Herein, a microfluidic device with cistern design for cultivation of adherent eukaryotic cells for the production of recombinant proteins is presented. The geometric configuration of the microchannels in the device provided laminar flow with reduced velocity profiles in the cisterns, resulting in an adequate microenvironment for long-term adherent cell growth with passive pumping flow cycles of 24 hours. CHO-ahIFNα2b and HEK-ahIFNα2b adherent cell lines expressing a novel anti-hIFN-α2b recombinant monoclonal antibody (MAb) for the treatment of systemic lupus erythematosus were cultured on the surface of PDMS/glass microchannels coated with poly-d-lysine. A 24 day culture of CHO-ahIFNα2b cells resulted in MAb concentrations up to 166.4 μg mL per day. The productivity of CHO-ahIFNα2b and HEK-ahIFNα2b cell lines was higher in the microdevice compared to that obtained using the adherent cell culture method (T-flask), with a 5.89- and 7.31-fold increase, respectively. Moreover, biological analysis of the MAbs produced in the microdevice showed no significant differences in the neutralizing antiproliferative activity of the hIFN-α2b or the cytokine cell signaling compared to the MAbs produced with cell adherent methods. These results suggest that this microfluidic device is suitable for long-term culture of mammalian cells and can improve the productivity of cells expressing recombinant MAbs with potential for therapeutic use without affecting the quality attributes of the product.

This paper describes a methodology of photopolymer mold fabrication with multi-level microstructures for polydimethylsiloxane (PDMS) microfluidic device manufacture.

Over the past few years, image analysis has emerged as a powerful tool for analyzing various cell biology parameters in an unprecedented and highly specific manner. The amount of data that is generated requires automated methods for the processing and analysis of all the resulting information. The software available so far are suitable for the processing of fluorescence and phase contrast images, but often do not provide good results from transmission light microscopy images, due to the intrinsic variation of the acquisition of images technique itself (adjustment of brightness / contrast, for instance) and the variability between image acquisition introduced by operators / equipment. In this contribution, it has been presented an image processing software, Python based image analysis for cell growth (PIACG), that is able to calculate the total area of the well occupied by cells with fusiform and rounded morphology in response to different concentrations of fetal bovine serum in microfluidic chips, from microscopy images in transmission light, in a highly efficient way.

Lab on a Chip (LOC) farming systems have emerged as a powerful tool for single cell studies combined with a non-adherent cell culture substrate and single cell capture chips for the study of single cell derived tumor spheres. Cancer is characterized by its cellular heterogeneity where only a small population of cancer stem cells (CSCs) are responsible for tumor metastases and recurrences. Thus, the in vitro strategy to the formation of a single cell-derived sphere is an attractive alternative to identify CSCs. In this study, we test the effectiveness of microdevices for analysis of heterogeneity within CSC populations and its interaction with different components of the extracellular matrix. CSC could be identify using specific markers related to its pluripotency and self-renewal characteristics such as the transcription factor Oct-4 or the surface protein CD44. The results confirm the usefulness of LOC as an effective method for quantification of CSC, through the formation of spheres under conditions of low adhesion or growing on components of the extracellular matrix. The device used is also a good alternative for evaluating the individual growth of each sphere and further identification of these CSC markers by immunofluorescence. In conclusion, LOC devices have not only the already known advantages, but they are also a promising tool since they use small amounts of reagents and are under specific culture parameters. LOC devices could be considered as a novel technology to be used as a complement or replacement of traditional studies on culture plates.

Conventional manufacturing methods for polydimethylsiloxane (PDMS)-based microdevices require multiple steps and elements that increase cost and production time. Also, these PDMS microdevices are mostly limited to single use, and it is difficult to recover the contents inside the microchannels or perform advanced microscopy visualization due to their irreversible sealing method. Herein, we developed a novel manufacturing method based on polymethylmethacrylate (PMMA) plates adjusted using a mechanical pressure-based system. One conformation of the PMMA plate assembly system allows the reproducible manufacture of PDMS replicas, reducing the cost since a precise amount of PDMS is used, and the PDMS replicas show uniform dimensions. A second form of assembling the PMMA plates permits pressure-based sealing of the PDMS layer with a glass base. By reversibly sealing the microdevice without using plasma for bonding, we achieve chip on/off configurations, which allow the user to open and close the device and reuse it in an easy-to-use way. No deformation was observed on the structures of the PDMS microchannels when a range of 10 to 18 kPa pressure was applied using the technique. Furthermore, the functionality of the proposed system was successfully validated by the generation of microdroplets with reused microdevices via three repetitions.