Biosensor-based detection of fungal enzyme activity for quantitative evaluation of invasive fungal diseases in immunocompromised patients

N. Ibrisimovic Mehmedinovic, M. Ibrisimovic, J. Dedic, A. Kesic, Z. Hodzic, N. Hadzigrahic
University of Tuzla, Faculty of Natural Sciences and Mathematics,
Bosnia and Herzegovina

Keywords: invasive fungal disease, biosensor, PLGA, aspartyl proteinase


Fungal infections are one of the most often couses of morbidity and mortality in immunocompromised patients due to negative impairment of the basic mechanisms of the host cell defence. Oportunistic fungi such as Candida and Aspergillus are responsible for development of invasive fungal diseases (IFD) in cancer patients and patient undergoing stem cell or solid organ transplantation. Timely pathogen detection is prerequisite for fast intervention and adequate therapy administration, as well as pathogen differentiation (infection with fungi or bacteria). In our study we present 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 immunocompromised patients. This thin-layer, biomimetic, biosensor chip detects enzyme aspartyl proteinase which is excreted by fungal species with ability of parallel exclusion 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 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 polymer layer of the biosensor that can be visible even with an unaided 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 invaders 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 IFD from very small amount of a test sample. This could be stable and pretty reliable diagnostic basis in helping making of decision about therapy choice, which is timely dependet and often false due to lack of information about type of infection which often cannot be provided fast enough. This biosensor chip detects presence of fungal cells within few hours only and is not time consuming as most of the available conventional microbiological methods. Presented polmer-based biosensor technology has potential to improve menagment of patients with fungal infections and to help to reduce enormous diagnostic health care costs for detection and treatment of IFDs, or prevent unnecessary antibiotic therapy before bacterial presence was confirmed. This technology provides relatively fast, quantitative method for detection of fungal infections in a real time.