Determination of Aspergillus niger fungus by amperometric tyrosinase biosensors modified with nanomaterials in biomedical objects and agricultural products

For determination of mold fungus antigen (Ag) Aspergillus niger, amperometric biosensors based on a printed graphite electrode modified with multi-walled carbon nanotubes (MWCNT), reduced graphene oxide (RGO), and gold nanoparticles (Au NP) were developed. Tyrosinase enzyme was used as a biosensitive component. It was found that Aspergillus niger Ag is an activator of tyrosinase in the concentration range of 1 × 10–8 – 1 × 10–5 μg/mg with LOD = 7 × 10–9 μg/mg. Modification of the electrode surface with carbon nanomaterials and the MWCNT/Au NPs nanocomposite allowed us to improve a number of analytical characteristics: expand the range of detectable concentrations to 1 × 10–10 – 1 × 10–3 μg/mg in the case of MWCNTs and MWCNTs/Au NPs, 5 × 10–10 – 1 × 10–3 μg/mg in the case of RGO, reduce the LOD to 7 × 10–11 μg/mg (MWCNT modifier), 1 × 10–10 μg/mg (RGO), 5 × 10–11 μg/mg (MWCNTs/Au NPs). Kinetic parameters of the reaction of enzymatic transformation of phenol in the presence of Ag Aspergillus niger were studied: regardless of the presence or absence of the modifier two-parameter coordinated activation of the enzyme-substrate tyrasinase – phenol system was observed. The developed biosensors were tested for the quantitative assessment of Aspergillus niger Ag content in a sample of agricultural crop (onion) and in a sample of bronchoalveolar lavage (BAL). The accuracy of the obtained results was confirmed by reference methods — microbiological (sample of onion) and using amperometric enzyme immunoassay sensor (BAL).