Glass-based Chip Research Articles

Enhanced fluorescence signal using stray light shutter in a quantitative PCR chip

Quantitative polymerase chain reaction (qPCR) is the most important quantitative sensing technique for pathogens, especially for emerging pandemics such as the coronavirus outbreak this year. The qPCR chip and device were investigated to meet the unmet needs of ultrafast inspection time, high accuracy, and small system volume. Therein, the fluorescence intensity was the most important signal in qPCR quantification of DNA amplifications, which is essential not only in the confirmative diagnosis of positive or negative infection, but also in the assessment of viral load for therapeutic and quarantine decision making. As the target DNAs got amplified, the interaction of fluorescence dye and double strand DNA will generate fluorescence signal proportional to amplified DNA in the intensity when excited by certain wavelength. A miniature spectro-detector was employed to receive the fluorescence scattering for digital output of the intensity in the qPCR chip in this study, and the optical simulation and actual experimental design and results according to the optical simulation results were performed to study the effect of the stray light shutter (SLS) in the improvement of the signal in fluorescence detection. The analysis results showed that the signal-to-noise ratio (SNR) of the fluorescence can be enhanced significantly for five times of the control using the SLS with a shape of extended component aperture, where the protruding structure was positioned away from the center. The experimental results showed that fluorescence intensity can be enhanced by 15.50% and 9.86% when adding the above shape of SLS in resin- and in glass-based chip, respectively. The results also demonstrated that the optical setup had good stability and repeatability in fluorescence detection, and variation was less than 1.00%. Our results can provide important reference to the development of qPCR chip to obtain the high SNR fluorescence signal in DNA quantification process.

Microarray-Based Allergy Diagnosis: Quo Vadis?

More than 30% of the world population suffers from allergy. Allergic individuals are characterized by the production of immunoglobulin E (IgE) antibodies against innocuous environmental allergens. Upon allergen recognition IgE mediates allergen-specific immediate and late-phase allergic inflammation in different organs. The identification of the disease-causing allergens by demonstrating the presence of allergen-specific IgE is the key to precision medicine in allergy because it allows tailoring different forms of prevention and treatment according to the sensitization profiles of individual allergic patients. More than 30 years ago molecular cloning started to accelerate the identification of the disease-causing allergen molecules and enabled their production as recombinant molecules. Based on recombinant allergen molecules, molecular allergy diagnosis was introduced into clinical practice and allowed dissecting the molecular sensitization profiles of allergic patients. In 2002 it was demonstrated that microarray technology allows assembling large numbers of allergen molecules on chips for the rapid serological testing of IgE sensitizations with small volumes of serum. Since then microarrayed allergens have revolutionized research and diagnosis in allergy, but several unmet needs remain. Here we show that detection of IgE- and IgG-reactivity to a panel of respiratory allergens microarrayed onto silicon elements is more sensitive than glass-based chips. We discuss the advantages of silicon-based allergen microarrays and how this technology will allow addressing hitherto unmet needs in microarray-based allergy diagnosis. Importantly, it described how the assembly of silicon microarray elements may create different microarray formats for suiting different diagnostic applications such as quick testing of single patients, medium scale testing and fully automated large scale testing.

Fast packaging of glass-based microfluidic chip using adhesive polyurethane material

A fast packaging method is proposed to fabricate the packaging of glass-based chips using polyurethane (PU). The performance properties of this material can be justified by the A-glue/B-glue weight ratio. To choose an appropriate proportion of glues, water contact angle, 90° peel strength, and shore hardness are employed to measure the PU material. By increasing the A-glue/B-glue weight ratio, the hardness of the PU board decreases, the peel strength increases, and the contact angle increases first and then decreases. Based on the performance of PU material, an A-glue/B-glue weight ratio of 3.6:1 is adapted to package the glass chip. However, the softness of PU led to the design and implementation of a stable plate to protect the chip. Mixing application experiment results verified the validity of the PU packing method. After comparing three packaging method, the glass-PU chip packing method was the most efficient and economical. Test results indicate that the PU Packing method can be widely used in the fabrication of microfluidic chips.

Label-Free Biochips for Accurate Detection of Prostate Cancer in the Clinic: Dual Biomarkers and Circulating Tumor Cells

Purpose: Early diagnosis of prostate cancer (PCa) is essential for the prevention of metastasis and for early treatment; therefore, we aimed to develop a simple, accurate, and multi-analyte assay system for early PCa diagnosis in this study. Experimental design: We fabricated three kinds of biochips then integrated into microfluidic device for simultaneous detection of vascularendothelial growth factor (VEGF), prostate-specific antigen (PSA), and PCa circulating tumor cells (CTC) in human serum for accurate diagnosis of PCa. Then the integrated device can be put in the ELISA reader for signal analysis after sample incubation, no necessary of further fluorescence staining or microscopy counting. Result: The integrated device has wide liner detection ranges (0.05-25 ng/mL for both PSA and VEGF, and 5-300 cells/mL for PCa CTC), as well as high levels of sensitivity and selectivity, and demonstrated a high correlation with an enzyme-linked immunosorbent assay for sample detection in patients. Also, the presented biochips could maintain their stability when stored at 37°C for 49 days without significant differences in the red-shift (<5%). Conclusions: We have successfully developed a multi-analyte sensing system for rapid and easy detection of PSA, VEGF, and PC3 cells in PCa samples using label-free glass-based chips. This method presents the advantages of a broad working range, high specificity, label-free, high-speed, stability, and low cost detection method for point-of-care testing of PCa.

Versatile programmable eight-path-electrode power supply for automatic manipulating microfluids of a microfluidic chip

A versatile programmable eight-path-electrode power supply (PEPS) system for manipulating microfluids of a complex microfluidic chip has been developed. The PEPS system consisted of a single chip microprocessor as a central control unit and a personal computer (PC) as an upper computer, and the program could be operated under Windows98/2000/XP. The voltage output of each electrode was in the range of 0 to +8000 V (0.1% precision) while the current output was in the range of 0 to +999 μA. The voltage of eight electrodes could be operated either independently or synchronously by random combination of any electrodes through switching. The voltage output modes were “switch-off/floating”, “switch-on” and “grounded” and fast switched at ms-level between these modes, and run time (0.1 s precision) of these modes could be controlled as desired. The PEPS system was conveniently for controlling flow rate and direction of electroosmotic flow (EOF) in a chip network. Six electrodes were chosen to control the repeated ‘injection and separation’ of 1.0 × 10 −5 M fluorescein isothiocyanate (FITC) in a six-reservoir glass-based chip. The relative standard deviation (R.S.D., n = 4, S/N = 10) of the repeated operation was 0.9% for the reservation time ( t R) and 2.3% for the peak height, respectively.

Bonding of glass-based microfluidic chips at low- or room-temperature in routine laboratory

A low- or room-temperature bonding method was developed for fabrication of glass-based microfluidic chips without the requirement of clean environment and programmed high-temperature furnaces. After fundamental pretreatments, the glass substrates and cover plates to be bonded were sequentially soaked in concentrated sulfuric acid, washed with high-flow-rate tap water, de-ionized water and treated using HF steam as a necessary step. Finally, the plates were bonded by bringing the cleaned surfaces into close contact either under a continuous flow of de-ionized water or directly when treated with HF steam, and annealing at low-temperature (<100 °C) or room-temperature. With the key improvements such as fabrication process optimization, gridding channel design and HF steam treatment, the glass-based chips could be obtained with fast, easy and high bonding yields (>90%). The bonding quality of the chips was evaluated by employing SEM, shear strength testing procedure and electric current measurement at different applied voltages. The mechanism for the strong bonding strength was presumably related to the formation of a hydrolyzed layer on the glass plate surfaces after soaking them in acid or water for extended periods. Microfluidic chips bonded by the above method were evaluated in the CE separation of monofuctional reactive dye Cy5-labeled bioamines.

Development of Hybrid Microreactor for Protein Synthesis

We have developed an inexpensive temperature controlled microreactor(HMR: Hybrid Microreactor) for protein synthesis. The structure of the microreactor is a sandwich of glass-based chip and PDMS(polydimethylsiloxane) chip. The thermo control system, which is composed of a heater and a temperature sensor, is fabricated with an ITO (Indium Tin Oxide) resistive material on a glass substrate by ordinary microfabrication method based on photolithography and etching techniques. The reactor chamber and flow channels are fabricated by micromolding of PDMS. Since one can use thermo control system repeatedly by replacing only the easily-fabricated and low-cost PDMS reactor chamber, this microreactor is quite cost effective. As a demonstration of the microreactor, a DNA template of a GFP (Green Fluorescent Protein) is transcribed and translated using cell-free extract prepared from Escherichia coli. As a result, protein synthesis in this device was performed successfully.