Solid-phase extraction and purification of membrane proteins using a UV-modified PMMA microfluidic bioaffinity μSPE device

Assessing Breast Cancer Molecular Subtypes Using Extracellular Vesicles' mRNA

Extracellular vesicles (EVs) carry RNA cargo that is believed to be associated with the cell-of-origin and thus have the potential to serve as a minimally invasive liquid biopsy marker for supplying molecular information to guide treatment decisions (i.e., precision medicine). We report the affinity isolation of EV subpopulations with monoclonal antibodies attached to the surface of a microfluidic chip that is made from a plastic to allow for high-scale production. The EV microfluidic affinity purification (EV-MAP) chip was used for the isolation of EVs sourced from two-orthogonal cell types and was demonstrated for its utility in a proof-of-concept application to provide molecular subtyping information for breast cancer patients. The orthogonal selection process better recapitulated the epithelial tumor microenvironment by isolating two subpopulations of EVs: EVEpCAM (epithelial cell adhesion molecule, epithelial origin) and EVFAPα (fibroblast activation protein α, mesenchymal origin). The EV-MAP provided recovery >80% with a specificity of 99 ± 1% based on exosomal mRNA (exo-mRNA) and real time-droplet digital polymerase chain reaction results. When selected from the plasma of healthy donors and breast cancer patients, EVs did not differ in size or total RNA mass for both markers. On average, 0.5 mL of plasma from breast cancer patients yielded ∼2.25 ng of total RNA for both EVEpCAM and EVFAPα, while in the case of cancer-free individuals, it yielded 0.8 and 1.25 ng of total RNA from EVEpCAM and EVFAPα, respectively. To assess the potential of these two EV subpopulations to provide molecular information for prognostication, we performed the PAM50 test (Prosigna) on exo-mRNA harvested from each EV subpopulation. Results suggested that EVEpCAM and EVFAPα exo-mRNA profiling using subsets of the PAM50 genes and a novel algorithm (i.e., exo-PAM50) generated 100% concordance with the tumor tissue.

Direct 3D printed biocompatible microfluidics: assessment of human mesenchymal stem cell differentiation and cytotoxic drug screening in a dynamic culture system

BACKGROUND

In vivo-mimicking conditions are critical in in vitro cell analysis to obtain clinically relevant results. The required conditions, comparable to those prevalent in nature, can be provided by microfluidic dynamic cell cultures. Microfluidics can be used to fabricate and test the functionality and biocompatibility of newly developed nanosystems or to apply micro- and nanoelectromechanical systems embedded in a microfluidic system. However, the use of microfluidic systems is often hampered by their accessibility, acquisition cost, or customization, especially for scientists whose primary research focus is not microfluidics.

RESULTS

Here we present a method for 3D printing that can be applied without special prior knowledge and sophisticated equipment to produce various ready-to-use microfluidic components with a size of 100 µm. Compared to other available methods, 3D printing using fused deposition modeling (FDM) offers several advantages, such as time-reduction and avoidance of sophisticated equipment (e.g., photolithography), as well as excellent biocompatibility and avoidance of toxic, leaching chemicals or post-processing (e.g., stereolithography). We further demonstrate the ease of use of the method for two relevant applications: a cytotoxicity screening system and an osteoblastic differentiation assay. To our knowledge, this is the first time an application including treatment, long-term cell culture and analysis on one chip has been demonstrated in a directly 3D-printed microfluidic chip.

CONCLUSION

The direct 3D printing method is tested and validated for various microfluidic components that can be combined on a chip depending on the specific requirements of the experiment. The ease of use and production opens up the potential of microfluidics to a wide range of users, especially in biomedical research. Our demonstration of its use as a cytotoxicity screening system and as an assay for osteoblastic differentiation shows the methods potential in the development of novel biomedical applications. With the presented method, we aim to disseminate microfluidics as a standard method in biomedical research, thus improving the reproducibility and transferability of results to clinical applications.

Immobilization of synthesized phenyl-enriched magnetic nanoparticles in a fabricated Y-Y shaped micro-channel containing microscaled hedges as a microextraction platform

In this survey, a reliable and applicable Y-Y shaped micro-channel in a microfluidic device was designed and manufactured. A number of micro-scaled hedges were precisely fabricated inside the micro-channel to facilitate the immobilization of synthesized core-shell Fe₃O₄@SiO₂ magnetic nanoparticles (MNPs), functionalized by triethoxyphenylsilane (TEPS) by sol-gel technique. Both sample and reagents were introduced into the microfluidic device by a syringe pump to perform the extraction and desorption steps. The functionalized MNPs were characterized by transmission electron microscopy, X-ray diffraction spectroscopy and Fourier transform infrared spectroscopy. By adopting the strategy of extraction-on-chip using this microfluidic device, we were benefited from implementing the entire analyses with the minimum amount of desorbing solvent, MNPs, and aqueous/fruit juice samples. In contrast to dispersive solid phase extraction, dispersion of MNPs during experiment is prevented by fabrication of micro-scaled hedges in the micro-channel. Consequently the stabilized MNPs are reused for the entire runs. The microfluidic device was successfully exploited as an efficient extracting plateau to evaluate the extraction/desorption capability in analysis of some organophosphorus pesticides (OPPs) as model compounds. Our results indicate that the functionalization of Fe₃O₄@SiO₂ with TEPS, improved their extraction capability due to the existence of phenyl and hydroxyl groups for more efficient π-π and hydrogen bonding interactions. Eventually, μL-scale of the organic solvent was injected into a gas chromatography-mass spectrometry system. The limits of detection (3S_b) and quantification (10S_b) for the OPPs were 0.03-0.1 and 0.1-0.35 ng mL^-1, respectively. In addition, the interday and intraday precisions were lower than 5.3% (n = 3). The obtained recovery was 95-99% for water samples and 88-96% for fruit juice samples while satisfactory regression coefficients of 0.9949-0.9991, could be achieved.

Solid phase microextraction techniques used for gas chromatography: a review

In the last decade, the development and adoption of greener and sustainable microextraction techniques have been proved to be an effective alternative to classical sample preparation procedures. In this review, 10 commercially available solid-phase microextraction systems are presented, with special attention to the appraisal of their analytical, bioanalytical, and environmental engineering. This review provides an overview of the challenges and achievements in the application of fully automated miniaturized sample preparation methods in analytical laboratories. Both theoretical and practical aspects of these environment-friendly preparation approaches are discussed. The application of chemometrics in method development is also discussed. We are convinced that green analytical chemistry will be really useful in the years ahead. The application of cheap, fast, automated, “clever”, and environmentally safe procedures to environmental, clinical, and food analysis will improve significantly the quality of the analytical data.

Binding-induced nicking site reconstruction strategy for quantitative detection of membrane protein on living cell

Here, a binding-induced nicking site reconstruction strategy has been fabricated for quantitative detection of membrane protein on living cell. Taking protein tyrosine kinase-7 (PTK7) as model analyst, first, an aptamer probe was designed with an aptamer sequence, a trigger sequence and a nicking site. In the absence of PTK7, the aptamer sequence could partially hybridize with the trigger sequence, forming a stem-loop structure. And the two complementary sequences of the nicking site were separated, which could not be recognized by nicking enzyme. In the presence of PTK7, the aptamer probe and PTK7 binding caused the reconstruction of the probe, leading to the hybridization of the two separated nicking site sequences. Then, the nicking site could be identified and nicked, yielding the release of the trigger sequence. Next, the trigger sequence could initiate the homogeneous cascade amplification, producing multiple G-quadruplex structures. By inserting the N-Methyl Mesoporphyrin IX (NMM), enhanced fluorescence signal could be acquired. Through the binding-induced nicking site reconstruction, the trigger sequence could be released on the surface of living cell and became more accessible. By combining the cascade rolling circle amplification (RCA) and hybridization chain reaction (HCR), high sensitivity was achieved with a detection limit of 0.3 fM. Moreover, Quantitative assay of PTK7 on living cancer cells and normal cells were performed, suggesting that the proposed method was sensitive enough to detect changes in PTK7 expression. Thus, this strategy provided a novel and reliable method for membrane protein expression assay on living cell.

Characterization of activated cyclic olefin copolymer: effects of ethylene/norbornene content on the physiochemical properties

The ethylene/norbornene content within cyclic olefin copolymer (COC) is well known to affect the chemical and physical properties of the copolymer, such as the glass transition temperature (Tg) and transparency. However, no work has been reported evaluating the effects of the ethylene/norbornene content on the surface properties of COC following UV/O3 or O2 plasma activation. Activation with either O2 plasma or UV/O3 is often used to assist in thermal assembly of fluidic devices, increasing the wettability of the surfaces, or generating functional scaffolds for the attachment of biological elements. Thus, we investigated differences in the physiochemical surface properties of various ethylene/norbornene compositions of COC following activation using analytical techniques such as water contact angle (WCA), ATR-FTIR, XPS, TOF-SIMS, UV-VIS, AFM and a colorimetric assay utilizing Toluidine Blue O (TBO). Results showed that increased norbornene content led to the generation of more oxygen containing functionalities such as alcohols, ketones, aldehydes and carboxyl groups when activated with either UV/O3 or O2 plasma. Specifically, COC with ∼60% norbornene content showed a significantly higher -COOH functional group density when compared to COC with a 50% norbornene content and COC with a 35% norbornene content following UV/O3 or O2 plasma activation. Furthermore, COC with large norbornene contents showed a smaller average RMS roughness (0.65 nm) when compared to COC containing low norbornene contents (0.95 nm) following activation making this substrate especially suited for nanofluidic applications, which require smooth surfaces to minimize effects arising from dielectrophoretic trapping or non-specific adsorption. Although all COC substrates showed >90% transparency at wavelengths >475 nm, COC possessing high norbornene contents showed significantly less transparency at wavelengths below 475 nm following activation, making optical detection in this region difficult. Our data showed distinct physiochemical differences in activated COC that was dependent upon the ethylene/norbornene content of the thermoplastic and thus, careful selection of the particular COC grade must be considered for micro- and nanofluidics.

Interrogating Surface Functional Group Heterogeneity of Activated Thermoplastics Using Super-Resolution Fluorescence Microscopy

We present a novel approach for characterizing surfaces utilizing super-resolution fluorescence microscopy with subdiffraction limit spatial resolution. Thermoplastic surfaces were activated by UV/O3 or O2 plasma treatment under various conditions to generate pendant surface-confined carboxylic acids (-COOH). These surface functional groups were then labeled with a photoswitchable dye and interrogated using single-molecule, localization-based, super-resolution fluorescence microscopy to elucidate the surface heterogeneity of these functional groups across the activated surface. Data indicated nonuniform distributions of these functional groups for both COC and PMMA thermoplastics with the degree of heterogeneity being dose dependent. In addition, COC demonstrated relative higher surface density of functional groups compared to PMMA for both UV/O3 and O2 plasma treatment. The spatial distribution of -COOH groups secured from super-resolution imaging were used to simulate nonuniform patterns of electroosmotic flow in thermoplastic nanochannels. Simulations were compared to single-particle tracking of fluorescent nanoparticles within thermoplastic nanoslits to demonstrate the effects of surface functional group heterogeneity on the electrokinetic transport process.

Microfluidics for the detection of minimal residual disease in acute myeloid leukemia patients using circulating leukemic cells selected from blood

We report a highly sensitive microfluidic assay to detect minimal residual disease (MRD) in patients with acute myeloid leukemia (AML) that samples peripheral blood to search for circulating leukemic cells (CLCs). Antibodies immobilized within three separate microfluidic devices affinity-selected CLC subpopulations directly from peripheral blood without requiring pre-processing. The microfluidic devices targeted CD33, CD34, and CD117 cell surface antigens commonly expressed by AML leukemic cells so that each subpopulation's CLC numbers could be tracked to determine the onset of relapse. Staining against aberrant markers (e.g. CD7, CD56) identified low levels (11-2684 mL(-1)) of CLCs. The commonly used platforms for the detection of MRD for AML patients are multi-parameter flow cytometry (MFC), typically from highly invasive bone marrow biopsies, or PCR from blood samples, which is limited to <50% of AML patients. In contrast, the microfluidic assay is a highly sensitive blood test that permits frequent sampling for >90% of all AML patients using the markers selected for this study (selection markers CD33, CD34, CD117 and aberrant markers such as CD7 and CD56). We present data from AML patients after stem cell transplant (SCT) therapy using our assay. We observed high agreement of the microfluidic assay with therapeutic treatment and overall outcome. We could detect MRD at an earlier stage compared to both MFC and PCR directly from peripheral blood, obviating the need for a painful bone marrow biopsy. Using the microfluidic assay, we detected MRD 28 days following one patient's SCT and the onset of relapse at day 57, while PCR from a bone marrow biopsy did not detect MRD until day 85 for the same patient. Earlier detection of MRD in AML post-SCT enabled by peripheral blood sampling using the microfluidic assay we report herein can influence curative clinical decisions for AML patients.

Development of a field sampling method based on magnetic nanoparticles for the enrichment of pesticides in aqueous samples

A field sampling method based on magnetic core–shell silica nanoparticles was developed for field sampling and the enrichment of low concentrations of pesticides in aqueous samples.