Evaluation and comparison of in vitro degradation kinetics of DNA in serum, urine and saliva: A qualitative study.
BACKGROUND
Cell-free DNA is naturally degraded in various bodily fluids. The aim of this study was to determine the degradation kinetics of DNA, with and without protein, in serum, urine and saliva.


METHODS
Naked DNA and DNA-protein complex were prepared, added to the samples to be analysed and incubated at 37°C and room temperature for various lengths of time. Alleles of 20 short tandem repeat loci were amplified from the incubated samples, and clearance models were generated from the mean peak areas.


RESULTS
Plotting the natural logarithm of DNA concentration against the incubation time produced a linear relationship. The half-lives of DNA with and without protein in serum were 157.6min and 30.8min at 37°C, 330.5min and 70.5min at room temperature, respectively. The half-lives of DNA with protein in saliva were 175.6min and 251.3min at 37°C and room temperature, respectively. However, the half-lives of DNA in urine (both with and without protein) were too short to detect.


CONCLUSIONS
The kinetics of DNA degradation in serum and saliva followed a first-order clearance model. Urine had the strongest effect on DNA degradation, and the half-lives of DNA with protein were relatively longer than those of naked DNA.
College of Medical Laboratory, Dalian Medical University, Dalian 116044, China; Wuxi Maternal and Child Health Hospital Affiliated Nanjing Medical University, 214002 Wuxi, Jiangsu, China.
Wang
W
Yao
Dalian Blood Centre, Dalian, China.
Chen
C
Mei
Dalian Blood Centre, Dalian, China.
Xiao
X
Nan
College of Medical Laboratory, Dalian Medical University, Dalian 116044, China. Electronic address: liuhui60@sina.com.
Liu
L
Hui
D001798:Blood Proteins / Q000737:chemistry*; D004247:DNA / Q000097:blood / Q000652:urine; D053837:DNA Cleavage; D056426:Genetic Loci; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D018895:Microsatellite Repeats; D012463:Saliva / Q000737:chemistry*; D013535:Suspensions / Q000737:chemistry
D001798:Blood Proteins; D013535:Suspensions; D004247:DNA
Cell-free DNA; Half-life; Saliva; Serum; Urine