| Objective:Attenuated Total Reflection-Fourier Transform Infrared(ATR-FTIR)spectroscopy technology was used to initially explore the chemical changes of rat corneal tissues with the postmortem interval(PMI)extension and to construct regression equation,then analyze the influence of different factors,such as gender,ocular category,and tissues in vitro or in vivo on PMI,to provide a new approach and method for the estimation of postmortem interval.Method:(1)A total of 125 adult SD rats without eye disease were divided into female group and male group,left eye group and right eye group,in vivo group and in vitro group,and use ATR-FTIR spectrometer to collect infrared spectrum data of rat corneal tissues at 0,6,12,24,36,and 48h postmortem.Labsolution IR software was use to preprocess the spectral data and recorded the peaks position and absorbance,calculated the absorbance ratios of the main absorption peak at different time points,and observed the changes in the peak position,peak shape,absorbance and ratio of the main absorption peak of the rat cornea within 48h.The SPSS 20.0 software was used to perform statistical analysis on the spectral data,and the t test was used to compare differences in main absorbance ratio of the effects of different genders,ocular categories,and tissues in vivo and vitro in rats within 48h.(2)A total of 75 adult male SD rats without ophthalmopathy were taken,after the corneal tissues were extracted at 0,2,4,6,8,10,12,14,16,18,20,22,24,36,and 48h postmortem,and spectral data were collected and spectral preprocessing was performed.Result:As PMI was prolonged,the peak position and shape of the main absorption peaks of the corneal ATR-FTIR spectrum within 48h postmortem of the rats did not change significantly,and the main absorption peaks of ATR-FTIR speatrun were 1632,1575,1550,1453,1397,1339,1239,1081,1029cm-1,respectively,There was no significant difference in the ratios of the main absorption peak absorbance of the corneal tissues between female and male groups,left-ocular and right-ocular groups,in vivo and vitro groups at 0,6,12,24,36,and 48h postmortem(P>0.05).Within 48h postmortem of the rats(0,2,4,6,8,10,12,14,16,18,20,22,24,36,48h),the absorbance ratios at A1339/A1239(r=0.862)and A1453/A1239(r=0.861)have a significant positive correlation with PMI,the best fitting curve is a cubic curve(P<0.05),with the regression equations:y=0.591+0.07x-0.0000253x2-0.00000009797 x3(R2=0.750);y=0.678+0.04x+0.00009988x2-0.0000005768x3(R2=0.753).Conclusion:(1)Using ATR-FTIR spectroscopy,different chemical groups in corneal tissue showed regular changes with the prolongation of PMI,indicating that the degradation of the chemical components of corneal tissue after death is highly correlated with PMI,it is feasible to detect the spectral changes of postmortem corneal tissue by ATR-FTIR spectroscopy;(2)The ratio of corneal tissue absorbance was higher in A1339/A1239 and A1453/A1239 within 48h postmortem in rats,it shows that the degradation of nucleic acids and proteins has some value for PMI inference and is not affected by individual factors such as gender,ocular category,tissue in vitro.(3)ATR-FTIR spectroscopy can be one of the effective methods for PMI inference;(4)corneal is expected to be ideal material for PMI inference. |
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