Sophisticated and precise: design and implementation of a real-time optical detection system for ultra-fast PCR.

Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) has become indispensable in the realm of disease nucleic acid screening and diagnostics, owing to its remarkable precision and sensitivity, in which the real-time fluorescence detection system plays an extremely critical role. To solve the problems of long time and slow speed of traditional nucleic acid detection, PCR systems are evolving towards ultra-rapid configurations. Nonetheless, most extant ultra-rapid PCR systems either depend on endpoint detection for qualitative assessments due to inherent structural or heating constraints or circumvent the challenge of adapting optical systems to expeditious amplification systems, resulting in potential shortcomings in assay efficacy, volume, or expense. Consequently, this study proposed a design of a real-time fluorescence detection system for ultra-fast PCR, capable of executing six channels of real-time fluorescence detection. Through the meticulous calculation of the optical pathway within the optical detection module, effective regulation of system dimensions and the cost was accomplished. By devising an optical adaptation module, the signal-to-noise ratio was enhanced by approximately 307% without compromising the PCR temperature alteration rate. Ultimately, by employing a fluorescence model that accounted for the spatial attenuation effect of excitation light, as proposed herein, fluorescent dyes were arranged to evaluate the repeatability, channel interference, gradient linearity, and limit of detection of the system, which proved that the system had good optical detection performance. Finally, the real-time fluorescence detection of human cytomegalovirus (CMV) under 9 min ultra-fast amplification was achieved by a complete ultra-fast amplification experiment, which further validated the potential of the system to be applied to rapid clinical nucleic acid detection.

Ultra-fast, sensitive and low-cost real-time PCR system for nucleic acid detection.

Nucleic acid detection directly identifies the presence of pathogenic microorganisms and has various advantages, such as high sensitivity, commendable specificity and a short window period, and has been widely used in many fields, such as early tumor screening, prenatal diagnosis and infectious disease detection. Real-time PCR (polymerase chain reaction) is the most commonly used method for nucleic acid detection in clinical practice, but it always takes about 1-3 hours, severely limiting its application in particular scenarios such as emergency testing, large-scale testing and on-site testing. To solve the time-consuming problem, a real-time PCR system based on multiple temperature zones was proposed, which realized the speed of temperature change of biological reagents from 2-4 °C s-1 to 13.33 °C s-1. The system integrates the advantages of fixed microchamber-type and microchannel-type amplification systems, including a microfluidic chip capable of fast heat transfer and a real-time PCR device with a temperature control strategy based on the temperature difference. The detection of HCMV biological samples using the real-time PCR system in this research took only 15 min, which was 75% shorter compared to the commercial qPCR instrument such as BIO-RAD, and the detection sensitivity remained essentially the same. The system could complete nucleic acid detection within 9 min under extreme conditions, characterized by fast detection speed and high sensitivity, providing a promising solution for ultra-fast nucleic acid detection.

Ultrafast Microfluidic PCR Thermocycler for Nucleic Acid Amplification.

The polymerase chain reaction (PCR) is essential in nucleic acid amplification tests and is widely used in many applications such as infectious disease detection, tumor screening, and food safety testing; however, most PCR devices have inefficient heating and cooling ramp rates for the solution, which significantly limit their application in special scenarios such as hospital emergencies, airports, and customs. Here, we propose a temperature control strategy to significantly increase the ramp rates for the solution temperature by switching microfluidic chips between multiple temperature zones and excessively increasing the temperature difference between temperature zones and the solution; accordingly, we have designed an ultrafast thermocycler. The results showed that the ramp rates of the solution temperature are a linear function of temperature differences within a range, and a larger temperature difference would result in faster ramp rates. The maximum heating and cooling ramp rates of the 25 µL solution reached 24.12 °C/s and 25.28 °C/s, respectively, and the average ramp rate was 13.33 °C/s, 6-8 times higher than that of conventional commercial PCR devices. The thermocycler achieved 9 min (1 min pre-denaturation + 45 PCR cycles) ultrafast nucleic acid amplification, shortening the time by 92% compared to the conventional 120 min nucleic acid amplification, and has the potential to be used for rapid nucleic acid detection.