A thermostat chip of indium tin oxide glass substrate for static polymerase chain reaction and in situ real time fluorescence monitoring

PVDF Sensor Stimulated by Infrared Radiation for Temperature Monitoring in Microfluidic Devices

This paper presents a ferroelectric polymer-based temperature sensor designed for microfluidic devices. The integration of the sensor into a system-on-a-chip platform facilitates quick monitoring of localized temperature of a biological fluid, avoiding errors in the evaluation of thermal evolution of the fluid during analysis. The contact temperature sensor is fabricated by combining a thin pyroelectric film together with an infrared source, which stimulates the active element located on the top of the microfluidic channel. An experimental setup was assembled to validate the analytical model and to characterize the response rate of the device. The evaluation procedure and the operating range of the temperature also make this device suitable for applications where the localized temperature monitoring of biological samples is necessary. Additionally, ease of integration with standard microfluidic devices makes the proposed sensor an attractive option for in situ analysis of biological fluids.

Nucleic acid sandwich hybridization assay with quantum dot-induced fluorescence resonance energy transfer for pathogen detection

This paper reports a nucleic acid sandwich hybridization assay with a quantum dot (QD)-induced fluorescence resonance energy transfer (FRET) reporter system. Two label-free hemagglutinin H5 sequences (60-mer DNA and 630-nt cDNA fragment) of avian influenza viruses were used as the targets in this work. Two oligonucleotides (16 mers and 18 mers) that specifically recognize two separate but neighboring regions of the H5 sequences were served as the capturing and reporter probes, respectively. The capturing probe was conjugated to QD655 (donor) in a molar ratio of 10:1 (probe-to-QD), and the reporter probe was labeled with Alexa Fluor 660 dye (acceptor) during synthesis. The sandwich hybridization assay was done in a 20 μL transparent, adhesive frame-confined microchamber on a disposable, temperature-adjustable indium tin oxide (ITO) glass slide. The FRET signal in response to the sandwich hybridization was monitored by a homemade optical sensor comprising a single 400 nm UV light-emitting diode (LED), optical fibers, and a miniature 16-bit spectrophotometer. The target with a concentration ranging from 0.5 nM to 1 μM was successfully correlated with both QD emission decrease at 653 nm and dye emission increase at 690 nm. To sum up, this work is beneficial for developing a portable QD-based nucleic acid sensor for on-site pathogen detection.

Strategies for enhancing the speed and integration of microchip genetic amplification

In this work, we explore the use of methods that allow a significant acceleration of genetic analysis within microchips fabricated from low thermal conductivity materials such as glass or polymers. Although these materials are highly suitable for integrating a number of genetic analysis techniques onto lab-on-a-chip devices, their low thermal conductivity limits the rate at which heat can be transferred and hence lowers the speed of thermal cycling. However, short thermal cycling times are the key to bringing PCR to clinical point-of-care applications. Although shrinking the PCR reaction chamber volume can increase the speed of thermal cycling, this strategy is not always suitable, particularly when dealing with clinical samples with low analyte concentrations. In the present work, we combine two alternate strategies for decreasing the time required to perform PCR: implementing a heat sink and optimizing the PCR protocol. First, the heat sink substantially reduces the thermal resistance opposing heat dissipation into the ambient environment, and eliminates the parasitic thermal capacitance of the regions in the microchip that do not require heating. The low thermal conductivity of glass is used to our advantage to design the heat-sink placement to achieve fast thermal transitions while maintaining low power consumption. Second, we explore the application of two-stage PCR to provide a further reduction in the time required to perform genetic amplification by merging the annealing and extension stages of the commonly used three-stage PCR approach. In combination, we reduce the time required to perform thermal cycling by roughly a factor of 3 while improving the temperature control.