Introduction
The emergence of new technologies in the food industry has led to the production of a variety of nutritious foods containing allergenic proteins. Therefore, the accurate identification and measurement of allergens and the implementation of appropriate labeling rules on the product have become greatly important. Lysozyme is used in the beverage industry as a stabilizer and fermentation inhibitor instead of sulfites. It is also used in the production of cheese or beer as an inhibitor of butyric acid-producing bacteria. We also use lysozyme to prevent the loss of the beverage's desired color and to reduce the flora of lactic acid-producing bacteria in the product after malolactic fermentation is complete. Lysozyme may cause allergic reactions in sensitive individuals, even in small amounts.
Methods
This study presents the development of an electrochemical biosensor for detecting lysozyme in food samples. The biosensor utilizes a nanocomposite consisting of polyaniline nanowires, multi-walled carbon nanotubes, and gold nanoparticles (PANI NWs/MWCNTs-Au), combined with aptamer strands. To achieve this, Au nanoparticles were first synthesized by reducing gold (III) chloride salt with trisodium citrate dihydrate. The synthesized nanoparticles were then characterized using a UV-Vis spectrophotometer, FESEM, DLS, and FT-IR graphs. After that, a nanocomposite of multi-walled carbon nanotubes and gold nanoparticles (MWCNTs-Au) was synthesized and dropped onto the surface of a platinum (Pt) electrode. Then, polyaniline nanowires (PANI NWs) were synthesized on the MWCNTs-Au/Pt surface by the electrochemical method and chronoamperometry.
Results
The three-component PANI NWs/MWCNTs-Au nanocomposite enables easier and more stable immobilization of aptamer strands, thereby improving the biosensor's electrochemical signal. The electrochemical DPV technique was used to examine the output signals received from the biosensor after its incubation with lysozyme solution and the specific binding of aptamer sequences and lysozyme enzyme. The results showed that the developed electrochemical biosensor can measure lysozyme enzymes in a linear concentration range of 0.1 picomolar to 100 nanomolar, with a low limit of detection (LoD) of 3.5 femtomolar. The biosensor also provided acceptable results under selectivity, stability, and practical application tests in diluted egg white samples.
Conclusions
Under optimized experimental conditions, the developed PANI NWs/MWCNTs-Au/Pt-based biosensor can be used for quantitative determination based on the linear relationship between ΔIp and the logarithm of lysozyme concentration in the range of 0.1 picomolar to 100 nanomolar with a detection limit of 3.5 femtomolar. The obtained PANI NWs/MWCNTs-Au nanocomposite can be a potential compound in biosensing applications for the detection of allergenic agents.
