Differex TM System
Reduce your backlog of sexual assault samples. Simplify the extraction process.
The new Differex System from Promega separates male and female fractions from sexual assault samples with ease and accuracy.

Separate samples in a single spin

With the Differex System(a), fraction separation occurs in as little as 90 minutes for most samples with just one centrifugation.


The method starts with a standard proteinase K digestion of the sample. The swab and DNA-containing solution are centrifuged through a spin basket into a tube containing the Separation Solution. This solution effectively separates the sperm from any soluble DNA and cell debris in the sample. After the soluble DNA is removed, the sperm pellet is washed without centrifugation to remove any residual DNA.

The DNA IQ™ Lysis Buffer containing DTT is added to the epithelial and sperm fractions. This buffer effectively lyses the sperm without the need for further proteinase K digestion. DNA can then be purified from each fraction using the DNA IQ System.

All components of the Differex System are nonhazardous, This means you can use Differex in an open environment without disposal concerns.


Remove fractions cleanly with a defining dye.


The Differex System contains a yellow dye that partitions with the aqueous solution containing the epithelial DNA. This dye is effectively removed during DNA purification and will not interfere in amplification reactions.

The yellow dye acts as a visual aid to help remove the epithelial DNA from the Separation Solution and sperm pellet (Figure 1). After the differential centrifugation, the yellow dye aids in determining the efficiency of the wash steps.

The distinct separation of phases combined with the yellow color of the aqueous phase takes the guess-work out of the extraction process and reduces the training time and validation needed to implement this technology in your laboratory.


Get robust results on even the toughest samples


The Differex™ System works on challenging new and old samples typical of those from sexual assaults. In an internal study, samples were extracted from a four-year-old vaginal swab that contained added sperm and had been stored at room temperature. DNA was purified from 100µl (1/5th) of the epithelial fraction using the DNA IQ™ System. This DNA (0.5µl) was amplified using the PowerPlex® 16 System, and only minor epithelial DNA carryover into the sperm fraction was noted (Figure 2). Sensitivity was determined by placing decreasing amounts of semen on vaginal swabs, processing the samples, amplifying the purified DNA with PowerPlex® 16 and then analyzing the resulting peaks generated on an ABI PRISM® 3100 Genetic Analyzer (Figure 3). Under these conditions, DNA was purified and amplified from as little as 0.05µl of semen.

Figure 2. Analysis of old vaginal swabs with added semen. Vaginal swabs with added semen were prepared and stored at room temperature for approximately 4 years. Swabs were cut in half, and half of each swab was processed with the Differex™ System. DNA from the resulting two fractions was purified using the DNA IQ™ System. The DNA was then amplified with Power Plex® 16 and analyzed on an ABI PRISM® 310 Genetic Analyzer . The TMR channel is displayed for the sperm and epithelial fractions for both samples.
Figure 3. Sensitivity of the Differex™ System. Vaginal swabs with various amounts of added semen were cut in half, and half of each swab was processed with the Differex™ System. DNA was purified using the DNA IQ™ System. The purified DNA was amplified with Power Plex® 16 and analyzed on an ABI PRISM® 3100 Genetic Analyzer. The patterns in the TMR channel are displayed for the sperm fractions containing 1.0, 0.25, 0.1, 0.05 and 0.01µl of semen, while the bottom panel displays an epithelial fraction.

Work in a high-throughput format


To increase sample throughput, a consumable 96-well plate is being designed for the Differex System and the DNA IQ System. This plate will allow both proteinase K digestion and centrifugation of samples, eliminating transfer steps.

Following centrifugation, the samples can be placed on a robotic workstation for hands-free processing of differential extractions followed by DNA purification using the DNA IQ System. Reference samples can be processed using the same chemistry in the same or different plate.


Technical support when you need it


Highly trained Promega Forensic Regional Account Managers and Technical Services Scientists who support all genetic identity products are available to address any question you have. In addition, Promega offers you technical training, a global distribution network, workshops in human DNA typing and an annual symposium on human identification.


ISO standards for manufacturing and testing


Genetic identity products from Promega are manufactured following ISO 9001 standards. Our products are qualified using a functional assay for genetic identity testing. A certificate of analysis, including the performance testing procedure and specifications, is included with each product. Every system is supplied with a technical manual that contains specific and detailed protocols.

Cat. No.
Differex System™
50 samples
200 samples
DNA IQ™ System
100 samples
400 samples
Microtubes, 1.5ml
DNA IQ™ Spin Baskets
Proteinase K

Municipio Libre No. 366 Col. Santa Cruz Atoyac C.P. 03310 Ciudad de México
Tels: 5601-3004 / 2856 / 2063
E-mail: jzogbi@dczogbi.com