Raman spectroscopy and digital holography reveal visible light photodamage on human sperm cells

A complete label-free and non-destructive analysis of semen quality (in terms of morphology and biochemical structure integrity) is required before artificial insemination. An optical approach based on digital holography and Raman spectroscopy was proposed and simultaneously applied for the fast characterization of single selected sperm cells. In this work, we have used this approach to simultaneously study biochemical and morphological characteristics of human sperm cells irradiated with different green laser powers. Severe spermatozoa variations associated with a topological redistribution of the sample and a gradual decrease in the Raman signal intensity were detected in a label-free configuration. Importantly, at laser fluences where no morphological alterations were detected (30 MJ/cm2), high specific spectral variations were monitored to evaluate the cell photodegradation.