Low-Cost and Rapid-Production Microfluidic Electrochemical Double-Layer Capacitors for Fast and Sensitive Breast Cancer Diagnosis.

This technical note describes a new microfluidic sensor that combines low-cost (USD $0.97) with rapid fabrication and user-friendly, fast, sensitive, and accurate quantification of a breast cancer biomarker. The electrodes consisted of cost-effective bare stainless-steel capillaries, whose mass production is already well-established. These capillaries were used as received, without any surface modification. Microfluidic chips containing electrical double-layer capillary capacitors (µEDLC) were obtained by a cleanroom-free prototyping that allows the fabrication of dozens to hundreds of chips in 1 h. This sensor provided the successful quantification of CA 15-3, a biomarker protein for breast cancer, in serum samples from cancer patients. Antibody-anchored magnetic beads were utilized for immunocapture of the marker, and then, water was added to dilute the protein. Next, the CA 15-3 detection (<2 min) was made without using redox probes, antibody on electrode (sandwich immunoassay), or signal amplification strategies. In addition, the capacitance tests eliminated external pumping systems and precise volumetric sampling steps, as well as presented low sample volume (5 µL) and high sensitivity using bare capillaries in a new design for double-layer capacitors. The achieved limit-of-detection (92.0 µU mL-1) is lower than that of most methods reported in the literature for CA 15-3, which are based on nanostructured electrodes. The data shown in this technical note support the potential of the µEDLC toward breast cancer diagnosis even at early stages. We believe that accurate analyses using a simple sample pretreatment such as magnetic field-assisted immunocapture and cost-effective bare electrodes can be extended to quantify other cancer biomarkers and even biomolecules by changing the biorecognition element.

Biocompatible Wearable Electrodes on Leaves toward the On-Site Monitoring of Water Loss from Plants.

Impedimetric wearable sensors are a promising strategy for determining the loss of water content (LWC) from leaves because they can afford on-site and nondestructive quantification of cellular water from a single measurement. Because the water content is a key marker of leaf health, monitoring of the LWC can lend key insights into daily practice in precision agriculture, toxicity studies, and the development of agricultural inputs. Ongoing challenges with this monitoring are the on-leaf adhesion, compatibility, scalability, and reproducibility of the electrodes, especially when subjected to long-term measurements. This paper introduces a set of sensing material, technological, and data processing solutions that overwhelm such obstacles. Mass-production-suitable electrodes consisting of stand-alone Ni films obtained by well-established microfabrication methods or ecofriendly pyrolyzed paper enabled reproducible determination of the LWC from soy leaves with optimized sensibilities of 27.0 (Ni) and 17.5 kΩ %-1 (paper). The freestanding design of the Ni electrodes was further key to delivering high on-leaf adhesion and long-term compatibility. Their impedances remained unchanged under the action of wind at velocities of up to 2.00 m s-1, whereas X-ray nanoprobe fluorescence assays allowed us to confirm the Ni sensor compatibility by the monitoring of the soy leaf health in an electrode-exposed area. Both electrodes operated through direct transfer of the conductive materials on hairy soy leaves using an ordinary adhesive tape. We used a hand-held and low-power potentiostat with wireless connection to a smartphone to determine the LWC over 24 h. Impressively, a machine-learning model was able to convert the sensing responses into a simple mathematical equation that gauged the impairments on the water content at two temperatures (30 and 20 °C) with reduced root-mean-square errors (0.1% up to 0.3%). These data suggest broad applicability of the platform by enabling direct determination of the LWC from leaves even at variable temperatures. Overall, our findings may help to pave the way for translating "sense-act" technologies into practice toward the on-site and remote investigation of plant drought stress. These platforms can provide key information for aiding efficient data-driven management and guiding decision-making steps.

Development of a sticker sealed microfluidic device for in situ analytical measurements using synchrotron radiation.

Shedding synchrotron light on microfluidic systems, exploring several contrasts in situ/operando at the nanoscale, like X-ray fluorescence, diffraction, luminescence, and absorption, has the potential to reveal new properties and functionalities of materials across diverse areas, such as green energy, photonics, and nanomedicine. In this work, we present the micro-fabrication and characterization of a multifunctional polyester/glass sealed microfluidic device well-suited to combine with analytical X-ray techniques. The device consists of smooth microchannels patterned on glass, where three gold electrodes are deposited into the channels to serve in situ electrochemistry analysis or standard electrical measurements. It has been efficiently sealed through an ultraviolet-sensitive sticker-like layer based on a polyester film, and The burst pressure determined by pumping water through the microchannel(up to 0.22 MPa). Overall, the device has demonstrated exquisite chemical resistance to organic solvents, and its efficiency in the presence of biological samples (proteins) is remarkable. The device potentialities, and its high transparency to X-rays, have been demonstrated by taking advantage of the X-ray nanoprobe Carnaúba/Sirius/LNLS, by obtaining 2D X-ray nanofluorescence maps on the microchannel filled with water and after an electrochemical nucleation reaction. To wrap up, the microfluidic device characterized here has the potential to be employed in standard laboratory experiments as well as in in situ and in vivo analytical experiments using a wide electromagnetic window, from infrared to X-rays, which could serve experiments in many branches of science.

Converging Multidimensional Sensor and Machine Learning Toward High-Throughput and Biorecognition Element-Free Multidetermination of Extracellular Vesicle Biomarkers.

Extracellular vesicles (EVs) are a frontier class of circulating biomarkers for the diagnosis and prognosis of different diseases. These lipid structures afford various biomarkers such as the concentrations of the EVs (CV) themselves and carried proteins (CP). However, simple, high-throughput, and accurate determination of these targets remains a key challenge. Herein, we address the simultaneous monitoring of CV and CP from a single impedance spectrum without using recognizing elements by combining a multidimensional sensor and machine learning models. This multidetermination is essential for diagnostic accuracy because of the heterogeneous composition of EVs and their molecular cargoes both within the tumor itself and among patients. Pencil HB cores acting as electric double-layer capacitors were integrated into a scalable microfluidic device, whereas supervised models provided accurate predictions, even from a small number of training samples. User-friendly measurements were performed with sample-to-answer data processing on a smartphone. This new platform further showed the highest throughput when compared with the techniques described in the literature to quantify EVs biomarkers. Our results shed light on a method with the ability to determine multiple EVs biomarkers in a simple and fast way, providing a promising platform to translate biofluid-based diagnostics into clinical workflows.

Disposable Microfluidic Immunoarray Device for Sensitive Breast Cancer Biomarker Detection.

Breast cancer is the most common cancer in women worldwide. The detection of biomarkers has played a significant role in the early diagnosis and prognosis of breast cancer. Herein, we describe the construction of a disposable microfluidic immunoarray device (DµID) for the rapid and low-cost detection of CA15-3 (carbohydrate antigen 15-3), a protein biomarker for breast cancer. The DµID was constructed using a simple and rapid prototyping technique and was applied to detect CA15-3 in cancer patients. The DµID construction was based on the use of a double-sided adhesive card with a microfluidic channel and a screen-printed array with 8 electrodes. Both the immunoarray and microfluidic channel were designed using an inexpensive home cutter printer and using low-cost materials. The immunoarray was modified using the layer-by-layer technique aiming at immobilizing the primary antibody. For the biomarker detection, magnetic particles (MPs) modified with polyclonal antibodies and peroxidase enzymes were used as a strategy for capture, separation, and preconcentration of the biomarker, in addition to amplification of the electroanalytical signal. The preconcentration and amplification strategies integrated with the nanostructured immunosensors of the DµID meaningfully contributed toward the detection of CA15-3 with a limit of detection (LoD) of 6 µU mL-1, requiring as low as 2 µL of serum samples for 8 simultaneous detections. The obtained LoD was 1200 times lower compared to those of other immunosensors previously reported in the literature. The DµID was applied for the detection of CA15-3 in real samples of breast cancer patients and was found to present an excellent correlation with the well-established commercial electrochemiluminescence immunoassay. The association of the DµID with nanostructured surfaces and analyte capturing with bioconjugated paramagnetic particles is essentially a promising breakthrough for the low-cost and accurate detection of cancer biomarkers.

A simple method to produce 2D and 3D microfluidic paper-based analytical devices for clinical analysis.

This paper describes the fabrication of 2D and 3D microfluidic paper-based analytical devices (µPADs) for monitoring glucose, total protein, and nitrite in blood serum and artificial urine. A new method of cutting and sealing filter paper to construct µPADs was demonstrated. Using an inexpensive home cutter printer soft cellulose-based filter paper was easily and precisely cut to produce pattern hydrophilic microchannels. 2D and 3D µPADs were designed with three detection zones each for the colorimetric detection of the analytes. A small volume of samples was added to the µPADs, which was photographed after 15 min using a digital camera. Both µPADs presented an excellent analytical performance for all analytes. The 2D device was applied in artificial urine samples and reached limits of detection (LODs) of 0.54 mM, 5.19 µM, and 2.34 µM for glucose, protein, and nitrite, respectively. The corresponding LODs of the 3D device applied for detecting the same analytes in artificial blood serum were 0.44 mM, 1.26 µM, and 4.35 µM.