Laser Microdissection (LMD) is a new technique of separating specific cells or tissue from a mixture. This procedure can isolate cells by cutting away unwanted cells or tissues using a microscopic system equipped with a laser. .LMD technique does not change the morphology/chemistry of the cells.
The major issue in forensics is the less amount of male DNA available in sexual assault or rape cases. Female DNA sample present is abundant and strong while the male DNA might get swamped. The technique enables the detection of semen samples if no sperm cells are present.
The technology uses a Laser-Induced Forward Transfer (LIFT). The cap coated with an adhesive is placed directly on the tissue. The infrared laser heats the adhesive present in the cap thereby fusing the tissue in the underlying thin membrane. The laser cuts the tissue along with the membrane and drops the sample into the collection tube. Sperm cells in mixed cells are labeled with histological stains, labeled antibodies and/or in situ fluorescence hybridization. The collected sample is then amplified for protein, DNA or RNA analysis. The advantage of this procedure is the separation of cells from a mixture even if the amount is very less. It is a costly procedure and consumes time.
Sanders et al, http://www.ncjrs.gov/pdffiles1/nij/grants/217268.pdf
A) Sample is dried on a glass slide,coated with plastic.Laser cuts out plastic and sample drops into the tube.
B) Labeled sperm cells can be identified.
C) Sperm cells are taken out using laser.
D) Sample can be seen inside the collection tube.