DNA extraction and gene amplification from saliva deposited on a plastic cup using double swab technique

Background and Objectives: The positive identification of living or deceased persons using the unique traits and characteristics of the teeth and jaws is a cornerstone of forensics. Establishment of offender’s identity is essential in criminal investigations. Our study aims, to extract DNA from saliva deposited on a solid object (plastic cup), simulating saliva deposited on objects in real situations and to amplify STRs from salivary DNA for purpose of forensic individualization. Methods: Direct buccal swab samples were collected from five unrelated, healthy volunteers with no genetic and blood disorders. The volunteers were asked to drink fruit juice from a plastic cup and it was allowed to dry for sixty minutes. With a swab immersed in sterile distilled water the surface of the plastic cup was wiped for 15 seconds using moderately strong pressure and circular motions followed by a dry swab. The DNA is extracted using PCR technique and the Quality and quantity analysis of the DNA thus obtained will be performed by gel electrophoresis and spectrophotometry respectively. Results: Concentration of DNA isolated from direct buccal swab samples ranged from 8.5 mg/ml to 12.5 mg/ml with mean of 10.8 mg/ml, while those from five double swab samples ranged from 5.5 mg/ml to 10.5 mg/ml, with mean of 8.5 mg/ml. AMG and F13 could be amplified in all five (100%) of saliva samples deposited on the cup. All the amplified samples of double swab matched positively with corresponding direct buccal swab samples, giving 100% matching and overall success of 100%. Conclusion: Saliva is a very useful DNA source due to the fact that it contains leukocytes and exfoliated epithelial cells from the host. PCR allows replication of thousands of copies of a specific DNA sequence in vitro, enabling the study of small amounts of DNA. Our results show high reliability of PCR technique in amplifying gene loci from salivary samples. Based on our findings we concluded that even though amplification of DNA from salivary samples is a technique sensitive procedure, requiring strict control of various factors, it has a potential to be utilized in forensics.