Superhydrophobic Soot Coated Quartz Crystal Microbalances: A Novel Platform for Human Spermatozoa Quality Assessment

The functionality of human spermatozoa is a key factor for the success rate of natural human reproduction, but unfortunately the infertility progressively increases due to multifarious environmental factors. Such disquieting statistics requires the employment of sophisticated computer-assisted methods for semen quality analysis, whose precision, however, is unreliable in cases of patients with low sperm concentrations. In this study, we report a novel quartz crystal microbalance (QCM) based biosensor for in-situ quality assessment of male gametes, comprising a superhydrophobic soot coating as an interface sensing material. The soot deposition on the surface of a 5 MHz QCM eliminates the noise that normally arises upon immersion of the uncoated sensor in the test liquid environment, allowing the detection of human spermatozoa down to 1000-100,000 units/mL (1-100 ppb). Furthermore, the soot coated QCM delimitates in a highly repeatable way the immotile and motile sperm cells by inducing fundamentally distinct responses in respect to sensor sensitivity and signal trends. The obtained results reveal the strong potential of the superhydrophobic QCM for future inclusion in diverse laboratory analyses closely related to the in vitro fertilization procedures, with a final aim of gaining practical approaches for diagnoses and selection of male gametes.