Silver nanoparticles doped antimicrobial biocomposite for hydrogen peroxide biosensor

Abstract

Hydrogen peroxide is a molecule causes oxidative stress due to the imbalance between the production of reactive oxygen species and an elimination capacity of human. Hydrogen peroxide is produced as a result of cellular metabolic activity and above a certain concentration in a body causes destruction. While oxidative stress is sometimes equated with destruction, it sometimes has a positive effect by providing apoptosis of cancer cells. The body develops a natural defense mechanism with antioxidants such as superoxide dismutase and glutathione peroxidase, which help convert hydrogen peroxide into water or less harmful molecules. However, when exposed to negativities such as cellular stress and chronic inflammation, the production of reactive oxygen species in the body exceeds antioxidant production capacity and oxidative stress is triggered. Oxidative stress plays a role in the formation and progression of many diseases such as cardiovascular diseases, neurodegenerative disorders, cancer, aging, depression and sleep disorders. Measuring the level of hydrogen peroxide in biological samples, detecting oxidative stress markers and determining the extent of oxidative damage allow early diagnosis of diseases and provide important information about metabolism. For this purpose, it is important for clinicians and scientists to determine hydrogen peroxide. It is also effective in managing oxidative stress, protecting cell and tissue health, and reducing the risk of various diseases. Hydrogen peroxide biosensors are instruments designed to determine the presence and concentration of hydrogen peroxide. Enzymes or different biomarkers can be used to perform hydrogen peroxide determination. When determining hydrogen peroxide, a chemical reaction usually takes place between hydrogen peroxide and a reagent, resulting in a significant signal that varies with hydrogen peroxide concentration. Non-enzymatic hydrogen peroxide biosensors, one of the most preferred types in the biosensor classification, have been used to determine hydrogen peroxide concentration in clinical diagnostics and applications. With silver nanoparticles with high catalytic activity that can directly oxidize hydrogen peroxide molecules, the oxidation and reduction event generates an electrical signal that can be correlated with hydrogen peroxide concentration. The non-enzymatic hydrogen peroxide biosensor is more stable, more sensitive and with high catalytic content compared to other sensor systems. A hydrogen peroxide sensor consists of an electrode and a material coated on the electrode, designed to be specific to a species. To develop a sensitive and highly stable hydrogen peroxide biosensor, it is important to modify the surface of the working electrode with uniformly sized particles. Nanoparticles with high surface area and electrocatalytic activity are usually used for modification. In this study, the electrode surface was doped with silver nanoparticles by forming a polymer bed. Due to their nano size, silver nanoparticles increase the sensor surface area and trigger the redox reaction of hydrogen peroxide. The silver nanoparticles were produced using a green synthesis route, which enables the reduction of biomolecules in extracts from different plants with silver nitrate. The green synthesis method adopted in the study also touched upon biomedical applications. The use of the product is important for clinical applications thanks to the design and modification of the sensor system, which does not cause toxicity in the body. The uniqueness of this project is the ability of 2-Aminoethyl Methacrylate (AEMA) and 2-Hydroxyethyl Methacrylate (HEMA) monomers in polymer synthesis, AEMA's ability to form complexes with silver nanoparticles and HEMA's superior properties such as its hyprophilic structure and its response to stimuli such as temperature, by using green synthesis, a sensor coating system was developed from silver nanoparticles obtained from green/red pistachio hull and hibiscus leaf. In order to develop a sensitive and highly stable hydrogen peroxide biosensor, it is important to modify the working electrode surface with equidimensional particles. For this purpose, nanoparticles that increase the surface area and improve the electrocatalytic activity are used. For this purpose, the electrode surface was doped with silver nanoparticles by forming a polymer bed on the working electrode surface. Moreover, due to their nanosize, silver nanoparticles increase the sensor surface area and trigger the redox reaction of hydrogen peroxide. Since the silver nanoparticles selected for sensor modification were formed by reducing biomolecules in extracts from different parts of plants with silver nitrate, the green synthesis method used was useful for biomedical applications. Within the scope of this project, a specific biosensor was created and its performance was measured by electrochemical analysis. Silver nanoparticles were synthesized from hibiscus leaf and green/red pistachio hull using green synthesis. Silver nanoparticles were doped into the polymer by dropping method during polymerization and following the cryogel process. Silver nanoparticles and polymer/silver nanoparticle complexes were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, particle size analyzer, Fourier Transform Infrared Spectroscopy, Inductively Coupled Plasma and UV-Vis spectrophotometer. The electrochemical behavior of the modified electrodes was investigated by various electrochemical analyses such as CV, DPV and EIS. In addition, the antibacterial activity of silver nanoparticles was tested by disk diffusion method on gram-positive, gram-negative bacteria, yeasts and fungi and the inhibitory sites were recorded. Two novel biocomposite sensor designs with silver nanoparticles synthesized using AEMA and HEMA polymer complexes with hibiscus leaf and green/red pistachio hull were successfully fabricated. Size analysis and TEM images showed that the silver nanoparticles have coherent, spherical morphology and demonstrated the successful dispersion of nanoparticle spherules on the polymer surface. FTIR and SEM results show that the polymer and silver nanoparticles adhere to each other and form a compact composite structure. The antimicrobial activity of the produced silver nanoparticles was also investigated by disk diffusion method. Electrochemical analysis of each composite modified electrode made with different types of silver was performed. In CV analysis, the increase in current was observed linearly with increasing hydrogen peroxide concentration. In addition, the oxidation peak potential Epa 0.131V - 0.098V and reduction peak potential Epc - 0.042V - (-0.021) were found for different electrode designs, respectively. The linearity of current responses to increasing hydrogen peroxide concentration was supported by DPV results. In impedance analysis, the resistance of different composite structures was examined and proved to be low. Substances that can interact with a sensor system such as glucose, dopamine, ascorbic acid, lactic acid were examined and no interference was observed. As a result of the study, two different modified electrodes were formed from silver nanoparticles obtained from pistachio body and hibiscus leaf doped with p(AEMA-co- HEMA) polymer. The dynamic interference range of the p(AEMA-co- HEMA)PistachioHullAgNP electrode was (10pM-10mM), while the p(AEMA-co- HEMA)HibiscusLeafAgNP electrode was (80pM-10mM). The detection limit of the electrode modified with silver nanoparticles from pistachio hull was 1.4μM and 3.9μM for the other modified electrode, which proved to be a very sensitive sensor capable of responding to low hydrogen peroxide concentrations. The reproducibility of the sensor systems was very high and the response time was found to be less than 5 seconds by chronoamperometric measurements. Thanks to the non-enzymatic hydrogen peroxide biosensor design, a different sensor system has been produced with its antimicrobial effective design and production with high stability, sensitivity, selectivity, fast response time and easy production. In addition, these biocomposite sensors have great potential to be adapted to industrial applications.