Background. Fluorescence-based techniques are powerful and valuable tools for studying biological materials. Fluorescence spectroscopy is one of these techniques which measures autofluorescence from a sample containing components such as proteins. The aim of this study was to evaluate the influence of deep freezing on spectroscopic properties of human plasma using fluorescence spectroscopy.

Patients, materials and methods. The study group consisted of patients admitted to the Department of Cardiology and Internal Medicine at the University Hospital in Bydgoszcz, due to a preliminary diagnosis of acute coronary syndrome. The overall group comprised 27 patients. From each patient, 4 ml of blood was taken to obtainplasma that was used for further examination. In order to measure plasma spectroscopic properties, a Hitachi F-7000 spectrofluorimeter was used. The received results were analysed and evaluated with Origin 9.0 (OriginLab).

Results. Spectroscopic analysis of human plasma before and after freezing allowed us to divide plasma samples into three different subgroups, depending on their fluorescent properties. The first subgroup consisted of plasma samples, which showed entirely differently in spectroscopic analysis after one week of deep-freezing. The second subgroup of plasma samples showed partial changes in the measurements of autofluorescence, and in the third subgroup freezing-resistant plasma samples were included.

Conclusions. It seems that the process of deep-freezing could affect the autofluorescent properties of human plasma proteins. The explanation of the specific mechanisms responsible for the change of plasma fluorescent properties during the process of deep-freezing requires further elucidation.