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Using Acoustic Differential Extraction to enhance analysis of sexual assualt evidence on a valveless glass microdevice

Evander, Mikael LU ; Horsman, Katie M.; Easley, Christopher J.; Landers, James P.; Nilsson, Johan LU and Laurell, Thomas LU (2006) Micro Total Analysis Systems 2006 In Proceedings of µTAS 2006 Conference 2. p.1055-1057
Abstract
The isolation of male and female DNA is an important step in the analysis of sexual assault

evidence. A vaginal swab with female epithelial cells and male sperm cells is obtained from the

female, and it is vital to separate the male and female fractions in order to obtain a single-source

DNA profile of the suspect. In the case of a low abundance of sperm cells, it is very important that

no cells are lost in the isolation step.

The conventional isolation method used in the forensic DNA laboratories, differential

extraction, is a time-consuming step, requiring up to 24 hours. It is neither highly amenable to

automation, nor can it be easily integrated with other steps of the... (More)
The isolation of male and female DNA is an important step in the analysis of sexual assault

evidence. A vaginal swab with female epithelial cells and male sperm cells is obtained from the

female, and it is vital to separate the male and female fractions in order to obtain a single-source

DNA profile of the suspect. In the case of a low abundance of sperm cells, it is very important that

no cells are lost in the isolation step.

The conventional isolation method used in the forensic DNA laboratories, differential

extraction, is a time-consuming step, requiring up to 24 hours. It is neither highly amenable to

automation, nor can it be easily integrated with other steps of the analysis. Therefore, a novel

method of performing the isolation of male and female fractions of biological material from sexual

assault evidence has been developed, termed acoustic differential extraction (ADE).

After selectively lysing the female epithelial cells while keeping the sperm cells intact, the

sample, now containing sperm cells and female cell lysate, is infused in a 900 μm wide and 70 μm

deep microfabricated glass channel with miniature piezoelectric transducers mounted at the bottom

of the channel, as shown in Figure 1. Upon activation of the ultrasound, the sperm cells will be

trapped in a standing wave1 while free DNA will not be retained. The sperm cells, levitated in the

3D fluidic space above the transducer, can be washed with buffer and the unretained biological

material directed to an output reservoir. Using laminar flow valving2, the sperm cells can be

released and directed into a separate output reservoir in anticipation of DNA analysis, see Figure 2.

With the purpose of evaluating the ADE microdevice for the collection of the two output

fractions (male and female), preliminary work used a mock sexual assault sample created with

polystyrene microparticles as sperm cells and Evan's Blue dye as female cell lysate. The particles

were trapped over the transducer and the dye was directed to the female outlet reservoir as shown

in Figure 3. After washing the particles, the ultrasound was deactivated and the flow redirected in

order to collect the particles in the male outlet reservoir.

A biological sample consisting of sperm cells and lysed female epithelial cells was

subsequently tested by infusion into the device for five minutes while trapping the sperm cells over

the transducer (Figure 4). The trapped sperm cells were washed with PBS for five minutes, then

released and collected for analysis off-chip. DNA from the isolated cells was extracted with a

commercial DNA extraction kit and analyzed with a duplex quantitative PCR assay3 to show the

sample purity. An example of the qPCR data obtained is provided in Table 1.

The results show that a highly-enriched sperm cell fraction can be obtained with the ADE

technique. It is reasonable to expect that this technique can be integrated with on-chip downstream

sample processing, e.g. DNA extraction and amplification. This would greatly diminish the analysis

time from 24 hours to approximately 60 minutes. The time savings, in combination with the

possibility to create a fully automated system, gives the ADE technique the potential to significantly

alter the means by which sexual assault evidence is processed in crime laboratories today. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
differential extraction, forensic science, Acoustic trapping
in
Proceedings of µTAS 2006 Conference
editor
Kitamori, Takehiko; Fujita, Hiroyuki and Hasabe, Shinji
volume
2
pages
3 pages
publisher
Society for Chemistry and Micro-Nano Systems
conference name
Micro Total Analysis Systems 2006
ISBN
4-9903269-0-3-C3043
language
English
LU publication?
yes
id
2da45b3e-5600-45fb-bf5e-27d510cf05c1 (old id 789816)
date added to LUP
2007-12-21 10:54:54
date last changed
2016-04-16 10:03:43
@misc{2da45b3e-5600-45fb-bf5e-27d510cf05c1,
  abstract     = {The isolation of male and female DNA is an important step in the analysis of sexual assault<br/><br>
evidence. A vaginal swab with female epithelial cells and male sperm cells is obtained from the<br/><br>
female, and it is vital to separate the male and female fractions in order to obtain a single-source<br/><br>
DNA profile of the suspect. In the case of a low abundance of sperm cells, it is very important that<br/><br>
no cells are lost in the isolation step.<br/><br>
The conventional isolation method used in the forensic DNA laboratories, differential<br/><br>
extraction, is a time-consuming step, requiring up to 24 hours. It is neither highly amenable to<br/><br>
automation, nor can it be easily integrated with other steps of the analysis. Therefore, a novel<br/><br>
method of performing the isolation of male and female fractions of biological material from sexual<br/><br>
assault evidence has been developed, termed acoustic differential extraction (ADE).<br/><br>
After selectively lysing the female epithelial cells while keeping the sperm cells intact, the<br/><br>
sample, now containing sperm cells and female cell lysate, is infused in a 900 μm wide and 70 μm<br/><br>
deep microfabricated glass channel with miniature piezoelectric transducers mounted at the bottom<br/><br>
of the channel, as shown in Figure 1. Upon activation of the ultrasound, the sperm cells will be<br/><br>
trapped in a standing wave1 while free DNA will not be retained. The sperm cells, levitated in the<br/><br>
3D fluidic space above the transducer, can be washed with buffer and the unretained biological<br/><br>
material directed to an output reservoir. Using laminar flow valving2, the sperm cells can be<br/><br>
released and directed into a separate output reservoir in anticipation of DNA analysis, see Figure 2.<br/><br>
With the purpose of evaluating the ADE microdevice for the collection of the two output<br/><br>
fractions (male and female), preliminary work used a mock sexual assault sample created with<br/><br>
polystyrene microparticles as sperm cells and Evan's Blue dye as female cell lysate. The particles<br/><br>
were trapped over the transducer and the dye was directed to the female outlet reservoir as shown<br/><br>
in Figure 3. After washing the particles, the ultrasound was deactivated and the flow redirected in<br/><br>
order to collect the particles in the male outlet reservoir.<br/><br>
A biological sample consisting of sperm cells and lysed female epithelial cells was<br/><br>
subsequently tested by infusion into the device for five minutes while trapping the sperm cells over<br/><br>
the transducer (Figure 4). The trapped sperm cells were washed with PBS for five minutes, then<br/><br>
released and collected for analysis off-chip. DNA from the isolated cells was extracted with a<br/><br>
commercial DNA extraction kit and analyzed with a duplex quantitative PCR assay3 to show the<br/><br>
sample purity. An example of the qPCR data obtained is provided in Table 1.<br/><br>
The results show that a highly-enriched sperm cell fraction can be obtained with the ADE<br/><br>
technique. It is reasonable to expect that this technique can be integrated with on-chip downstream<br/><br>
sample processing, e.g. DNA extraction and amplification. This would greatly diminish the analysis<br/><br>
time from 24 hours to approximately 60 minutes. The time savings, in combination with the<br/><br>
possibility to create a fully automated system, gives the ADE technique the potential to significantly<br/><br>
alter the means by which sexual assault evidence is processed in crime laboratories today.},
  author       = {Evander, Mikael and Horsman, Katie M. and Easley, Christopher J. and Landers, James P. and Nilsson, Johan and Laurell, Thomas},
  editor       = {Kitamori, Takehiko and Fujita, Hiroyuki and Hasabe, Shinji},
  isbn         = {4-9903269-0-3-C3043},
  keyword      = {differential extraction,forensic science,Acoustic trapping},
  language     = {eng},
  pages        = {1055--1057},
  publisher    = {ARRAY(0x9358e60)},
  series       = {Proceedings of µTAS 2006 Conference},
  title        = {Using Acoustic Differential Extraction to enhance analysis of sexual assualt evidence on a valveless glass microdevice},
  volume       = {2},
  year         = {2006},
}