Electrochemical Impedance Spectroscopy-Based Biosensors for Label-Free Detection of Pathogens

Abstract

The escalating threat of infectious diseases necessitates the development of diagnostic technologies that are not only rapid and sensitive but also deployable at the point of care. Electrochemical impedance spectroscopy (EIS) has emerged as a leading technique for the label-free detection of pathogens, offering a unique combination of sensitivity, non-invasiveness, and adaptability. This review provides a comprehensive overview of the design and application of EIS-based biosensors tailored for pathogen detection, focusing on critical components such as biorecognition elements, electrode materials, nanomaterial integration, and surface immobilization strategies. Special emphasis is placed on the mechanisms of signal generation under Faradaic and non-Faradaic modes and how these underpin performance characteristics such as the limit of detection, specificity, and response time. The application spectrum spans bacterial, viral, fungal, and parasitic pathogens, with case studies highlighting detection in complex matrices such as blood, saliva, food, and environmental water. Furthermore, integration with microfluidics and point-of-care systems is explored as a pathway toward real-world deployment. Emerging strategies for multiplexed detection and the utilization of novel nanomaterials underscore the dynamic evolution of the field. Key challenges-including non-specific binding, matrix effects, the inherently low ΔR_ct/decade sensitivity of impedance transduction, and long-term stability-are critically evaluated alongside recent breakthroughs. This synthesis aims to support the future development of robust, scalable, and user-friendly EIS-based pathogen biosensors with the potential to transform diagnostics across healthcare, food safety, and environmental monitoring.

Keywords: biorecognition strategies; microfluidic integration; nanomaterial enhancement; non-faradaic detection; point-of-care diagnostics.

Figure 1

Schematic illustration of signal generation mechanisms in label-free EIS biosensors under Faradaic and non-Faradaic modes. In the Faradaic mode (left), pathogen binding hinders the access of the redox probe ([Fe(CN)₆]³⁻/⁴⁻) to the electrode surface, thereby increasing the R_ct. In the non-Faradaic mode (right), pathogen attachment alters the dielectric environment at the electrode–electrolyte interface, reducing the C_dl. Both mechanisms lead to measurable changes in the impedance spectrum.

Figure 2

Visual summary of the major types of BREs employed in EIS-based pathogen biosensors. Each class—antibodies, aptamers, phages, peptides, MIPs/CIPs, whole cells, and lectins/carbohydrates—exhibits distinct physicochemical characteristics, advantages, and limitations that influence biosensor specificity, stability, cost, and viability-based detection capacity.

Figure 3

Schematic representation of the integration between electrode materials and nanomaterials in label-free EIS-based pathogen biosensors. Common electrode substrates, such as gold, carbon-based materials, ITO, and platinum, are shown with their key properties. Nanomaterials including AuNPs, AgNPs, CNTs, graphene derivatives, and MOFs enhance sensor performance through an improved surface area, electron transfer, biocompatibility, and functionalization capacity.

Figure 4

Representative strategies for immobilizing BREs on electrode surfaces in EIS-based biosensors. The illustration compares physical adsorption, covalent attachment via EDC/NHS chemistry, encapsulation in hydrogel or polymer matrices, oriented immobilization (e.g., via Protein A/G or streptavidin-biotin systems), and click chemistry (CuAAC/SPAAC). Each approach differs in stability, orientation control, and compatibility with specific biorecognition elements.

Figure 5

Comparative overview of EIS biosensor design strategies across bacterial, viral, fungal, and parasitic pathogens. Key features include typical biorecognition elements, common electrode materials, enhancement nanomaterials, representative detection limits, and example sample matrices.

Figure 6

Electrode preparation steps, including the drop-cast deposition of AuNP on bare SPEs, followed by the immobilization of FRhk-4 cells and subsequent testing with HAV [148].

Figure 7

Schematic illustration of one-step electrochemical aptasensor preparation [79].

Figure 8

The step-wise process of coating the surface of the microfabricated Au WE with SAM and the immobilization of anti-Cryptosporidium antibodies onto the microfabricated Au WE [141].

Figure 9

The experimental procedure of E. coli DNA detection based on hybrid MoS₂ nanomaterials IDE sensors [124].