This paper presents a disposable microfluidic device for on-chip lysing, PCR, and analysis in one continuous-flow process. Male-female sex determination was performed with human saliva in less than 20 min from spit to finish, and requiring only seconds of manual sample handling. This genetic analysis was based on the amplification and detection of the DYZ1 repeat region unique to the Y-chromosome. The flow-through microfluidic chip consisted of a single serpentine channel designed to guide samples through 42 heating and cooling cycles. Cycling was performed by matching the local channel geometry to a steady-state temperature gradient established across the microfluidic chip. 38 channel segments were designed for rapid low volume PCR, and four were optimized for spatial DNA melting analysis. Fluorescence detection was used to monitor the amplification and to capture the melting signature of the amplicon was performed with a basic 8-bit CCD camera. The microfluidic device itself was fabricated from microscope slides and a double-sided tape. The simplicity of the system and its robust performance combine in an elegant solution for lab-on-a-chip genetic analysis.

In this article, low cost microfluidic devices have been used for simultaneous amplification and analysis of DNA. Temperature gradient flow PCR was performed, during which the unique fluorescence signature of the amplifying product was determined. The devices were fabricated using xurography, a fast and highly flexible prototype manufacturing method. Each complete iterative design cycle, from concept to prototype, was completed in less than 1 h. The resulting devices were of a 96% glass composition, thereby possessing a high thermal stability during continuous-flow PCR. Volumetric flow rates up to 4 microl/min induced no measurable change in the temperature distribution within the microchannel. By incorporating a preliminary channel passivation protocol, even the first microliters through the system exhibited a high amplification efficiency, thereby demonstrating the biocompatibility of this fabrication technique for DNA amplification microfluidics. The serpentine microchannel induced 23 temperature gradient cycles in 15 min at a 2 microl/min flow rate. Fluorescent images of the device were acquired while and/or after the PCR mixture filled the microchannel. Because of the relatively high initial concentration of the phage DNA template (PhiX174), images taken after 10 min (less than 15 PCR cycles) could be used to positively identify the PCR product. A single fluorescent image of a full device provided the amplification curve for the entire reaction as well as multiple high resolution melting curves of the amplifying sample. In addition, the signal-to-noise ratio associated with the spatial fluorescence was characterized as a function of spatial redundancy and acquisition time.

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This article presents a microfluidic technique for the real-time analysis of DNA damage due to radiation exposure. A continuous-flow spatial melting analysis was performed every three seconds on a sample of isolated DNA while it was being irradiated. The formation of photoproducts being caused by the UV-C radiation was monitored during the process. Cumulative damage produced distinct changes in the DNA melting curves, characterized by a shifting and broadening of the melting peaks. The design of the microfluidic device, the experimental procedure, and the analysis algorithm and interactive GUI are discussed herein. In addition, the advantages of this system are correlated to specific needs of related scientific studies, such as the investigation of sequence-specific damage susceptibility and the characterization of exposure-damage nonlinearities.