Early detection of fungal pathogens in patients with immunodeficiency involving a novel biosensor technology

Oportunistic fungi such as Candida spp. and Aspergillus spp. are responsible for development of invasive fungal diseases (IFDs) in cancer patients and patients undergoing stem cell or solid organ transplantation, and are one of the most often causes of mortality in immunodeficient patients. Early fungal pathogen detection is prerequisite for fast intervention and adequate therapy administration. Fast pathogen differentiation between fungi, bacteria or even viral infections is highly required. During our study we developed biosensor chip based on the polymer poly lactic-co-glycolic acid (PLGA), as a novel diagnostic tool for rapid and quantitative detection of fungal infections from plasma sample of the immunodeficient patients. This double-layer, biomimetic, biosensor chip detects fungal enzyme aspartyl proteinase with ability of parallel elimination of eventual bacterial co-infection, achieved due to modulation of the biosensor's matrix. The biosensor setup is consisting of a thin-metal layer called inconnel, which is covered by polymer layer that can be degraded by lytic enzymes such as enzyme aspartyl proteinase. Enzymatic activity of aspartyl proteinase that can be produced by low number of fungal cells is sufficient to cause reduction in thickness of the polymer layer of the biosensor that can be visible even with the naked eye, as change in surface color of the biosensor. Biosensor prototypes were produced in a limited number under lab conditions and revealed clear signal in patient's sample with fungal infection which strength correlated with amount of excreeted asparty proteinase. Modification and optimization of the biosensor matrix due to addition of specific stimulative agents, increased metabolic activity of present fungal pathogens and positively affected release of enzyme aspartyl proteinase. This simple in use and relatively cheep biosensor-based fungal detection test provides first and rapid screen for presence of IFDs from very small amount of a test sample, in this case serum or plasma. Presented biosensor tehnology detects presence of fungal cells within few hours only and is not time consuming as most of the available conventional microbiological methods, and enables a good and fast diagnostic basis in making decision about the treatment therapy.