Long target droplet polymerase chain reaction with a microfluidic device for high-throughput detection of pathogenic bacteria at clinical sensitivity

Microfluidic rapid isolation and electrochemical detection of S. pneumonia via aptamer-decorated surfaces

BACKGROUND

S. pneumoniae is widely recognized as a leading cause of respiratory infections worldwide, often resulting in high mortality rates. However, the advent of microfluidic technologies has brought significant advancements, including the simplified, sensitive, cost-effective, and rapid approach to pneumococcal bacteremia detection. In this study, a microfluidic magnetic platform is presented for rapid isolation, and an electrode array is utilized for the electrochemical detection of S. pneumoniae. Aptamer-decorated surfaces were employed for both isolation and detection. For isolation, silica magnetic microparticles were synthesized and decorated with aptamer.

RESULTS

Isolation performance was assessed for phosphate-buffered saline (PBS) and blood samples for different concentrations of S. pneumoniae. Electrical impedance spectroscopy (EIS) with fabricated gold interdigitated electrodes (IDEs) decorated with aptamer was implemented for the detection of S. pneumoniae at different bacteria concentrations. The microfluidic platform performed bacteria isolation at comparable isolation efficiency with batch systems but at a much faster rate (isolation took about a minute, and the aptamer-decorated electrode array exhibited a limit of detection (LOD) at 962 CFU/mL and linear range between 104 and 107 CFU/mL.

SIGNIFICANCE

Our method represents a significant advancement compared to previous reports. Our microfluidic platform can efficiently isolate 60 μL of the bacteria sample within about one minute. The entire process takes about two minutes including the detection step. Furthermore, our method achieves a notable improvement in the detection limit for S. pneumoniae compared to conventional ELISA and magnetic microfluidics ELISA.

A Portable Continuous-Flow Polymerase Chain Reaction Chip Device Integrated with Arduino Boards for Detecting Colla corii asini

Food security is a significant issue in modern society. Because morphological characters are not reliable enough to distinguish authentic traditional Chinese medicines, it is essential to establish an effective and applicable method to identify them to protect people's health. Due to the expensive cost of the manufacturing process and the large volume of the analytical system, the need to build a portable and cheap device is urgent. This work describes the development of a portable nucleic acid amplification device integrated with thermal control and liquid pumping connecting to Arduino boards. We present a novel microfluidic polymerase chain reaction (PCR) chip with symmetric isothermal zones. The total chip volume is small, and only one Arduino board is needed for thermal control. We assemble a miniaturized liquid pump and program an Arduino file to push the sample mixture into the chip to implement the PCR process. In the proposed operation, the Nusselt number of the sample flow is less than one, and the heat transfer is conduction only. Then we can ensure temperature uniformity in specific reaction regions. A Colla corii asini DNA segment of 200 bp is amplified to evaluate the PCR performance under the various operational parameters. The initial concentration for accomplishing the PCR process is at least 20 ng/μL at the flow rate of 0.4 μL/min in the portable continuous flow PCR (CFPCR) device. To our knowledge, our group is the first to introduce Arduino boards into the heat control and sample pumping modules for a CFPCR device.

Microfluidic devices for multiplexed detection of foodborne pathogens

The global burden of foodborne diseases is substantial and foodborne pathogens are the major cause for human illnesses. In order to prevent the spread of foodborne pathogens, detection methods are constantly being updated towards rapid, portable, inexpensive, and multiplexed on-site detection. Due to the nature of the small size and low volume, microfluidics has been applied to rapid, time-saving, sensitive, and portable devices to meet the requirements of on-site detection. Simultaneous detection of multiple pathogens is another key parameter to ensure food safety. Multiplexed detection technology, including microfluidic chip design, offers a new opportunity to achieve this goal. In this review, we introduced several sample preparation and corresponding detection methods on microfluidic devices for multiplexed detection of foodborne pathogens. In the sample preparation section, methods of cell capture and enrichment, as well as nucleic acid sample preparation, were described in detail, and in the section of detection methods, amplification, immunoassay, surface plasmon resonance and impedance spectroscopy were exhaustively illustrated. The limitations and advantages of all available experimental options were also summarized and discussed in order to form a comprehensive understanding of cutting-edge technologies and provide a comparative assessment for future investigation and in-field application.

Multichannel oscillatory-flow multiplex PCR microfluidics for high-throughput and fast detection of foodborne bacterial pathogens

In the field of continuous-flow PCR, the amplification throughput in a single reaction solution is low and the single-plex PCR is often used. In this work, we reported a flow-based multiplex PCR microfluidic system capable of performing high-throughput and fast DNA amplification for detection of foodborne bacterial pathogens. As a demonstration, the mixture of DNA targets associated with three different foodborne pathogens was included in a single PCR solution. Then, the solution flowed through microchannels incorporated onto three temperature zones in an oscillatory manner. The effect factors of this oscillatory-flow multiplex PCR thermocycling have been demonstrated, including effects of polymerase concentration, cycling times, number of cycles, and DNA template concentration. The experimental results have shown that the oscillatory-flow multiplex PCR, with a volume of only 5 μl, could be completed in about 13 min after 35 cycles (25 cycles) at 100 μl/min (70 μl/min), which is about one-sixth of the time required on the conventional machine (70 min). By using the presently designed DNA sample model, the minimum target concentration that could be detected at 30 μl/min was 9.8 × 10(-2) ng/μl (278-bp, S. enterica), 11.2 × 10(-2) ng/μl (168-bp, E. coli O157: H7), and 2.88 × 10(-2) ng/μl (106-bp, L. monocytogenes), which corresponds to approximately 3.72 × 10(4) copies/μl, 3.58 × 10(4) copies/μl, and 1.79 × 10(4) copies/μl, respectively. This level of speed and sensitivity is comparable to that achievable in most other continuous-flow PCR systems. In addition, the four individual channels were used to achieve multi-target PCR analysis of three different DNA samples from different food sources in parallel, thereby achieving another level of multiplexing.