This paper reports on the development, features, and testing of a portable forensic genetic analysis system that consists of a microfluidic device for amplification and separation of short tandem repeat (STR) fragments as well as an instrument for chip operation and four-color fluorescence detection.
The micro device performs polymerase chain reaction (PCR) in a 160-nL chamber and capillary electrophoresis (CE) in a 7-cm-long separation channel. The instrumental design integrates PCR thermal cycling, electrophoretic separation, pneumatic valve fluidic control, and four-color laser excited fluorescence detection. A quadruplex Y-chromosome STR typing system that consists of amelogenin and three YSTR loci (DYS390, DYS393, DYS439) was developed and used for validation studies. Quadruplex amplification and detection was conducted by mixing male and female standard genomic DNA together during the sample preparation. Resulting data indicate that the system is capable of analyzing male DNA in the presence of a high female DNA background. Although the ratio could be further lowered in amplifications without the amelogenin marker, additional valuable information, such as the male-to-female DNA ratio, is obtained with this quadruplex system from the peak area ratio of the two peaks in amelogenin. The entire assay was finished in 1.5 h due to the rapid low-volume (160 nL) thermal cycling and integrated high-speed electrophoretic separation. The detection limit of this system for multiplex amplification of genomic DNA is as low as 20 copies in the PCR chamber. This microdevice presents a first and significant step toward a fully integrated and portable system that allows highly sensitive, rapid STR analyses in a setting outside a forensic laboratory. For practical forensic applications in the future, a co-injection structure can be included in the microdevice to facilitate running sizing and allelic ladders. Other research recommendations are also offered. 7 figures and 1 table