Junior researchers at LMU Munich are also actively involved in the Lasers4Life project. One of them is Maša Bozič. As part of her Master’s project, she is using visible light to analyse blood samples, before they are examined with the newly developed near-infrared laser.
Both of these approaches use spectroscopy to characterize blood serum and blood plasma. The term ‘serum’ refers to the liquid phase obtained after whole blood has been allowed to coagulate, which therefore contains no clotting factors. Plasma retains all the normal clotting factors, but activation of the cascade of enzyme reactions that leads to blood clotting is prevented by the addition of an anticoagulant. Coagulation is normally triggered by damage to blood vessels. This in turn causes blood platelets to adhere the damaged vessel wall and ultimately leads to conversion of the protein fibrinogen into the fibrin network, which forms the mature clot and seals the wound.
Both serum and plasma are obtained from whole blood by centrifugation in the presence (plasma) or absence (serum) of an anticoagulant. The centrifugation step serves to remove the red and white blood cells (together with the clot, in the case of serum). Maša then subjects both samples to optical spectroscopy with visible light. As the beam passes through the sample, certain wavelengths of the incident light are absorbed by the substances present in the solution. The changes observed in the transmitted spectrum therefore provide information on the composition of the non-cellular fraction of the blood.
In this way, one can determine the concentration of certain proteins and lipids based on the characteristic pattern of absorption of the incident light. The method therefore allows Maša to establish the extent of day-to-day variation between samples taken from the same individual, or the range of variation between different individuals. This provides a baseline that allows one to assess whether differences in the absorption spectra lie within the normal limits of variation, or are indicative of pathological changes that reflect the presence of disease. The results also provide initial insights into the scale of the differences between the spectra obtained from cancer patients and control subjects.
Maša Bozic’s work therefore yields an essential reference for subsequent spectroscopic analyses with infrared laser light in the L4L project, as both spectroscopic methods rely on the same principle of selective absorption. However, infrared spectroscopy is far more sensitive than conventional spectroscopy with visible light. It therefore provides far more comprehensive and detailed information on the diversity of substances present in the samples, and should allow one to identify those that may be linked to the presence of malignant cells in the blood donor.