Conductometric Immunosensor for Escherichia coli O157:H7 Detection Based on Polyaniline/Zinc Oxide (PANI/ZnO) Nanocomposite

Antibody functionalized capacitance sensor for label-free and real-time detection of bacteria and antibiotic susceptibility

The effective management of infectious diseases and the growing concern of antibiotic resistance necessitates accurate and targeted therapies, highlighting the importance of antibiotic susceptibility testing. This study aimed to develop a real-time impedimetric biosensor for identifying and monitoring bacterial growth and antibiotic susceptibility. The biosensor employed a gold 8-channel disk-shaped microelectrode array with specific antibodies as bio-recognition elements. This setup was allowed for the analysis of bacterial samples, including Staphylococcus aureus, Bacillus cereus, and Micrococcus luteus. These microorganisms were successfully cultured and detected within 1 h of incubation even with a minimal bacterial concentration of 10 CFU/ml. Overall, the developed biosensor array exhibits promising capabilities for monitoring S. aureus, B. cereus and M. luteus, showcasing an excellent linear response ranging from 10 to 104 CFU/ml with a detection limit of 0.95, 1.22 and 1.04 CFU/mL respectively. Moreover, real-time monitoring of antibiotic susceptibility was facilitated by changes in capacitance, which dropped when bacteria were exposed to antibiotic doses higher than their minimum inhibitory concentration (MIC), indicating suppressed bacterial growth. The capacitance measurements enabled determination of half-maximal cytotoxic concentrations (CC50) values for each bacteria-antibiotic pair. As a proof-of-concept application, the developed sensor array was employed as a sensing platform for the real time detection of bacteria in milk samples, which ensured the reliability of the sensor for in-field detection of foodborne pathogens and rapid antimicrobial susceptibility tests (ASTs).

Conductometric immunosensor for specific Escherichia coli O157:H7 detection on chemically funcationalizaed interdigitated aptasensor

Escherichia coli O157:H7 is a strain of Escherichia coli known for causing foodborne illness through the consumption of contaminated or raw food. To detect this pathogen, a conductometric immunosensor was developed using a conductometric sensing approach. The sensor was constructed on an interdigitated electrode and modified with a monoclonal anti-Escherichia coli O157:H7 aptamer. A total of 200 electrode pairs were fabricated and modified to bind to the target molecule replica. The binding replica, acting as the bio-recognizer, was linked to the electrode surface using 3-Aminopropyl triethoxysilane. The sensor exhibited excellent performance, detecting Escherichia coli O157:H7 in a short time frame and demonstrating a wide detection range of 1 fM to 1 nM. Concentrations of Escherichia coli O157:H7 were detected within this range, with a minimum detection limit of 1 fM. This innovative sensor offers simplicity, speed, high sensitivity, selectivity, and the potential for rapid sample processing. The potential of this proposed biosensor is particularly beneficial in applications such as drug screening, environmental monitoring, and disease diagnosis, where real-time information on biomolecular interactions is crucial for timely decision-making and where cross-reactivity or interference may compromise the accuracy of the analysis.

ZnO nanostructures: A promising frontier in immunosensor development

This review addresses the design of immunosensors, which employ ZnO nanostructures. Various methods of modifying ZnO nanostructures with antibodies or antigens are discussed, including covalent and non-covalent approaches and cross-linking techniques. Immunosensors based on different properties of ZnO nanomaterials are described and compared. This article provides a comprehensive review of electrochemical immunosensors based on ZnO nanostructures and various detection techniques, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), photoelectrochemical (PEC) detection, electrochemical impedance spectroscopy (EIS), and other electrochemical methods. In addition, this review article examines the application of optical detection techniques, including photoluminescence (PL) and electrochemiluminescence (ECL), in the development of immunosensors based on ZnO nanostructures.

Detection of Salmonella Enteritidis in Milk Using Conductometric Immunosensor Coated on Polyaniline/Zinc Oxide Nanocomposite

The demand for rapid and accurate detection methods for Salmonella Enteritidis necessitates the development of highly sensitive and specific biosensors to ensure proper monitoring of food safety and quality requirements in the food sector and to secure human health. This study focused on development of a polyaniline/zinc oxide (PANI/ZnO) nanocomposite film on a gold electrode conductometric immunosensor for detection of Salmonella Enteritidis. The sensor was modified with monoclonal anti-Salmonella Enteritidis antibodies as biorecognition elements. The fabricated sensor was able to detect and quantify the target pathogen within 30 min and showed a good detection range from 10¹ to 10⁵ colony-forming units (CFU)/mL for Salmonella Enteritidis and a minimum detection limit of 6.44 CFU/mL in 0.1% peptone water. Additionally, the fabricated sensor showed good selectivity and detection limit toward the target bacterium and successfully determined Salmonella Enteritidis content in ultrahigh heat-treated skim milk samples without pretreatment of the food sample.