Our major objective in this study was to create complex, three-dimensional, and fully transparent polydimethylsiloxane (PDMS) fluidic device by revising the previously reported fabrication process and to systematically study the influence of each fabrication step to the final PDMS fluidic device. The current fabrication process adopted fused deposition modeling (FDM) 3D printers to create molds of acrylonitrile butadiene styrene (ABS) for use in PDMS casting, then solvent solution was used to dissolve the ABS mold embedded inside the PDMS device and a transparent PDMS device was created for experiments. However, it is quite challenging to ensure the complete removal of ABS molds inside the long, curly, and narrow channels. Ultrasonication was added into our fabrication process to improve the efficacy of dissolving ABS molds inside the channels and conclusions can be derived from these experiments: (1) ultrasonication-assisted dissolution is an effective approach to the complete removal of ABS molds embedded inside these long, curly, and narrow channels (for example, the mixer demonstrated herein had a diameter of 2 mm and length of 162 mm); (2) the application of solvent vapor polishing to 3D-printed molds is highly effective in reducing the surface roughness of the molds (8 ~ 10 μm before polishing to 038 ~ 0.5 μm after polishing) and important to preserve the transparency of the resulting PDMS devices; (3) ensuring the circulation of fresh solvent solution is critical to shorten the dissolution process.

The aptamer, known as a chemical antibody, has proven to be of high diagnostic and therapeutic value with the FDA’s first aptamer drug in 2004 and many aptamers under clinical validation. However, the clinical translation of aptamer for therapeutics has been delayed because of the limitation of using the target model during selection and a lack of information on several crucial factors, including their inherent physicochemical characterization and safety, and the function. Three-dimensional (3D) structure tissue provides proof of in-depth functionality due to their maturity and 3D complexity, enabling them to get information on the natural structure of the target for human treatment. The organ-on-a-chip integrates microfluidic technology with 3D cell culture that possesses in vivo-like tissue-based models that have been engineered for validation to transform the commercial drug discovery. Thus, the organ-on-a-chip may offer a promising solution for the addressed problems, enhancing the clinical translation procedure for aptamer-based therapeutics. Motivated by the advantageous function of the aptamer-based organ-on-a-chip system, we update the current technology to generate aptamers using SELEX (Systematic Evolution of Ligands by EXponential Enrichment) and confirm the application of aptamers to various long-term treatments. We can also accurately analyze the advantages of organ-on-a-chips and present the necessity of developing aptamer-based organ-on-a-chip systems. In this regard, the aptamer-based organ-on-a-chip is expected to increase the possibility of creating an aptamer as a therapeutic agent by more accurately selecting and verifying the aptamer that affects specific organ treatment.

The number of people at risk for dengue viral infection is about 50% of the worlds population. Dengue viral infection is classified as dengue fever and severe dengue depending on the severity. Severe dengue may be associated with infection by the different serotype from the primary infected serotype. The circulating epidemic serotypes have changed continuously and periodically. It is very important to diagnose dengue viral infection as early as possible to be treated adequately. The purpose of this study was the development of a simultaneous detection method for all the serotypes of dengue virus in a single sample. The consensus primers and four different fluorescein-tagged probes that specifically binds to each serotype of dengue virus were designed from the multiple alignment data of full-length dengue viral sequences, which were retrieved from GenBank. They were located between the 5’ untranslated region and the capsid gene of the dengue viruses. Each serotype of dengue viruses isolated in Korea was detected correctly with the established multiplex real time RT-PCR at the level of 5-10 copies/reaction. Other RNA viruses such as the Japanese encephalitis virus, Zika virus, yellow fever virus, and Chikungunya virus were not amplified with this method. The results of the inter-assays and intra-assays were within the acceptable variation ranges. Conclusively, the developed method can detect each serotype of dengue virus specifically and quantitatively even when different serotypes of dengue virus are present in a sample.

3D bioprinting is one of the rapidly evolving fields of tissue engineering where microengineering meets cells biology within an unprecedented precision to construct tissue structures of various forms with complexity. However, enabling simultaneous printing of heterogeneous biomaterial along with scaffold components through the currently available printers is still considered as a major challenge due to the lack of instrumentation. Flow control is one of the major issues associated with the process. In this aspect, a microfluidic nozzle head equipped with two shape-memory alloy (SMA) actuators was proposed and integrated with a commercially available 3D printer to assist the biomaterial printing in a more systematic manner. The SMA actuator restrains the amount of flows for fabricating the desired scaffold components. Experimental results illustrated that the use of SMA actuator ensued a rapid and precise flow control of biomaterial and can further facilitate to maintain the width of any printed structures. As a proof of concept for the profound biomedical applications with the present manufacturing configuration, a 3D printed hydrogel platform was fabricated with demonstrated characters for later cell seeding after the printing further opens a new chapter in terms of biomaterial printing.

Warfarin is a drug associated with blood clotting. As the side effects of this drug are fatal, it is important to adjust its dosage for each individual. In particular, DNA analysis of patients is necessary because the effect of the drug varies greatly depending on the genotype of the individual. Real-time PCR technology is usually used for DNA analysis. This technology requires expensive equipment, large space, and long experimental time. To solve these problems, we used a PCR module based on a CMOS photosensor. There are a heater circuit for thermal control on the its back side, and well-like structure on the surface, enabling location based multiplex PCR. We developed primers and probes to detect warfarin-related SNPs, and integrated with the PCR module. We tested the commercial Real-time PCR systems and our PCR modules. Based on the results, we confirmed that the level of performance of our system was similar to that of the commercial systems.

There are many factors that affect the increase or decrease of viscosity of the whole blood. Because of this, measuring the viscosity of whole blood is difficult to correlate with specific etiologies, so it tends to disregard the information on blood viscosity. This study is to find out the characteristics of the method of measuring the viscosity of whole blood using the parallel plate method, which is officially registered as a medical device with the approval of the Korea Food and Drug Administration (KFDA), and to apply it to the measurement of whole blood viscosity. The accuracy of the parallel plate measurement is verified by comparing with the measurement results using the commercially available scanning capillary method. In addition, statistically meaningful results are obtained between the viscosity and some components of the whole blood. It is expected that the research will be carried out to understand the correlation between the viscosity of whole blood and specific components of blood and to identify the prognostic signs of etiology in certain diseases, especially in cardiovascular and cerebral vessels diseases.

The early detection of mercury ions in water sources should be emphasized to prevent human exposure to mercury through drinking water or food consumption. Here, we used a three-dimensional (3D)-printed multiarray chip to achieve colorimetric detection of inorganic mercury ions in environmental matrices such as lake water. The chip designed for the multidetection of inorganic mercury did not require an electrical syringe pump or a complex analytical system, thereby making it suitable for on-site detection. The chip could detect inorganic mercury ions via rolling circle amplification, by selectively harnessing thymine-Hg2+-thymine coordination chemistry. Additionally, the activities of rolling circle amplification in simple and environmental matrices were compared. The limits of detection for inorganic mercury ions were 3.4 and 4.1 ??g/L in the simple and environmental matrices, respectively. Further, the chip was successfully applied for the detection of mercury in actual lake water samples collected from locations nearby inland fish farms. The results were quantitatively comparable to those obtained using a conventional mercury analyzer.

Economic development has raised concerns about human healthcare and disease prevention from its early stages. In that regard, the detection of biomarkers is crucial for early diagnosis of diseases, and it is an essential tool for managing various health conditions. The clinical diagnostics industry is worth hundreds of billions of dollars and has been expanding. However, the traditional methods for biomarkers detection are high-cost and time-consuming. Also, they usually require highly trained personnel and complex instrumental processes, only providing a centralized medical diagnosis system in large hospitals or specialized facilities. In contrast, a chemosensor is a smart molecular analytical device designed to sense an analyte to generate a detectable signal and to offer direct diagnosis without complex instruments or systems. Moreover, electrochemiluminescence (ECL) possesses distinct advantages such as low-costs, simplicity, and portability. ECL has become a useful technique and has been widely applied in many fields, from basic research to practical applications. Chemosensors coupled with ECL can provide compelling advantages over conventional approaches, such as rapid response time, higher sensitivity, and selectivity. This minireview aims to highlight recent representative studies on ECL-based chemosensors for clinical applications. It provides a general overview of the design and structure of ECL-based chemosensors, and also covers the general problems and challenges. The presented content may prove to be useful for discovering new sensor concepts or extension of existing biomarker detection strategies.

Fully automated system for sample preparation in molecular diagnostics was developed. The small cartridge with multiple chambers and a rotating valve was designed for automated processes such as extraction, separation and purifications during the DNA sample preparation. The automated processes such as injection, mixing, capturing and valve on/off motions were controlled by an affordable, motorized control system. We demonstrated the automated DNA extraction of pathogenic bacteria using this system. The deviations in the purity and real-time polymerase chain reaction (PCR) detection of the automated DNA extraction samples were clearly decreased. The device provided rapid, reliable, and reproducible sample preparation in comparison with manual DNA extraction. This automated platform can be utilized in emergent point-of-care testing of infectious disease and foodborne bacteria.

Digital polymerase chain reaction (dPCR) enables the accurate determination of deoxyribonucleic acid (DNA) copy numbers. In contrast to real-time PCR (qPCR), dPCR can perform quantification without requiring previous standard curve experiments. Furthermore, dPCR is more sensitive for rare targets in genetic samples. Despite the significant advantages of dPCR over qPCR, dPCR is not widely applied yet due to the complicated requirements of instrumentations regarding creating sample subvolumes and the equipment cost associated with this. In this paper, we present a microwell array that can be used for dPCR. The microwell array can be operated with little micro-fluidic expertise, while it can be manufactured at a unit cost of less than 1$. The amplification results of the microwell array can be analyzed with a custom-written Python script. With this method, we have been able to amplify and quantify complementary deoxyribonucleic acid (cDNA) samples for the H7N9 influenza virus in a concentration range spanning three orders of magnitude (1,000-100,000 copies/μL).