Broadband infrared spectroscopy for non-contact measurement of neurological disease biomarkers in cerebrospinal fluid

Cerebrospinal fluid (CSF) is a clear and colorless biological fluid which circulates within brain ventricles (cavities), the spinal cord’s central canal, the space between the brain and the spinal cord, as well as their protective coverings, the meninges. Cerebrospinal fluid contains different constituents, such as albumin and lactate, whose levels are used clinically as biomarkers of neurodegenerative disorders. In current clinical practice, analysis of CSF content for the diagnosis of central nervous system disorders requires an invasive procedure known as lumbar puncture or spinal tap. With the aim of developing a noninvasive alternative, we report here the spectral behavior of albumin and lactate over a broad wavelength range of 600-2000 nm, after each was added separately at varying normal and abnormal concentration levels to artificial CSF (aCSF). Spectral measurements were conducted simultaneously by two different spectrometers working at different spectral ranges in transmittance mode. Spectral analysis revealed that albumin and lactate each possesses its own first and second derivative absorbance spectra fingerprint between 1660 and 1810 nm. Distinguishing albumin from lactate by their spectral data enabled the differentiation between aCSF conditions modeling different neurological disorders. Spectral changes of each compound strongly correlated (R²>0.9) with absorbance derivative spectra peaks at specific wavelengths, when analyzed by linear regression with variations in their concentration. These findings suggest the feasibility of CSF biomarker assessment by broadband infrared spectroscopy.