Raman spectroscopic signature of semen and its potential application to forensic body fluid identification

Transcription

1 Raman spectroscopic signature of semen and its potential application to forensic body fluid identification Kelly Virkler, Igor K. Lednev Forensic Science International 193 (2009) Sasithorn Promwan

2 Crime Scene Investigation Biological evidences Body fluid : blood, semen, saliva, vaginal Many problem for tests Destruction of the sample False positive result Insufficient amount of sample 2

3 Raman Spectroscopy Use for determining the type of substance and molecular analysis Observe the Laser diffraction The laser with specific intensity and wave length Individual spectrum for any substances The vibration of the chemical bond, detected with this technique, needs to be polarized Substance with symmetric chemical bond(s) gives smooth peak(s) 3

4 Advantages No sample preparation No reagents needed Required vary small amount of sample : pg or fl Non-destructive Very little interference from water 4

5 5

6 6

7 Results Human semen Canine semen Vaginal fluid Saliva Sweat Blood 7

8 Conclusions Obtained different spectra from 5 body fluids. Human and canine semen yield very distinguishable spectra that were remarkably different from one another. Non-destructive 8

9 9

10 Introduction Blood, semen : the most prevalent body fluid found during criminal investigations. Semen : in cases sexual assault Method for confirmatory identification of semen : Microscopic visualization and Porstate-specific Ag (PSA) 10

11 Disadvantages Staining method can not be applied to men with azoospermic PSA test kit is destructive to the sample and occationally gives false positive

12 Objectives To determine the heterogeneity of a dried semen sample from one donor. To determine the amount of spectral variation from one semen donor to another. 12

13 Sample Materials and Methods 50 semen samples from in vitro fertilization clinic 1 sample : random to be a basis sample 10 µl drop on a circular glass slide Scan a sample area of 75x75 µm Measure Raman spectra from 36 random points 13

14 Materials and Methods (cont.) Raman microscope Renishaw invia confocal Raman spectrometer 20x long-range objective WiRE 2.0 software Nanonics AFM MultiView 1000 system Measurements: Quartz II and QuartzSpec software Excitation: 785-nm laser light Laser power: 115 mw Spot size of the excitation beam: 5 µm wide 14

15 Materials and Methods (cont.) Data treatment GRAMS/AI 7.01 software MATLAB Significant factor analysis (SFA) Alternate least squares (ALS) Curve Fitting Toolbox in MATLAB 15

16 Results & Discussions 16

17 Single sample heterogeneity Basis semen sample Spectral Component 1 Spectral Component 2 Spectral Component 3 17

18 Component 1 Component 3 From different spots in the same dried semen sample 18

19 Multiple donors semen blood saliva Basic spectroscopic signature Average Sample spectral 19

20 The semen signature fit for a semen sample The semen signature fit for a saliva sample 20

21 Conclusions The spectrum of a dried semen sample contained three major spectral components: tyrosine, protein (choline), spermine phosphate hexahydrate (SPH) There are no significant qualitative visual changes in the Raman spectra of dried semen acquired from multiple donors. 21

22 Conclusions (cont.) Combination of the three principal components can be used as a unique spectroscopic signature to identify the presence of semen Non-destructive 22

23 Conclusions (cont.) Continuing investigation of semen samples and other body fluid To develop unique spectroscopic signatures for other body fluids using Raman spectroscopy Experiment with a more advanced stastistical method which uses principal component analysis (PCA) to compare multiple spectra of different body fluid 23

24 Special Thanks อาจารย ดร. พ ลลภ ค นธ ยงค 24

25 Questions???? 25