Non-Invasive Detection of Cytokines in Saliva Towards Asthma Phenotyping Using an Electrochemical Sensor
Authors: Churcher Nathan , Prasad Shalini 
Published: August 2024

Introduction: Asthma is a complicated and heterogeneous condition of the lungs which is usually associated with the chronic inflammation of the airways. Traditionally, classification of asthma has been based on clinical attributes such as the symptoms observed and response to treatment. However, with the growing understanding of the heterogeneity of asthma as a spectrum with varying underlying causes, asthma phenotyping has been on the horizon. Cytokines are the chemical messengers that play a crucial role in the immune system. They mediate communication between the cells in the immune system and as such have a direct effect on the inflammation process. The role of some cytokines has been established in the pathogenesis of asthma. Due to the involvement of cytokines in the modulation of asthma, they can be excellent target for asthma phenotyping. This is also helpful because identification and quantification of these inflammatory mediators can allow for more precise medicine for more targeted treatment. To aid the identification and quantification of cytokines in the phenotyping of asthma, we have created a customizable (currently for IL-8 and IL-10) multi-marker electrochemical platform for the detection of cytokines non-invasively in saliva. The developed electrochemical platform can detect cytokines rapidly and non-invasively within reported physiological ranges of the given cytokines. Evaluating the presence and quantity of the cytokines will be useful in the phenotyping and treatment plans adopted by physicians.
Materials and Methods: The electrochemical sensor consists of 6 multiplexed gold electrodes on a PCB substrate. IL-8 and IL-10 antibodies were immobilized onto the sensor surface using a gold-thiol linker chemistry. Sensor response was evaluated with non- faradaic Electrochemical Impedance Spectroscopy (nf-EIS). Pooled human saliva was spiked with increasing doses of IL-8 and IL-10 in their respective physiological ranges to develop a dose response curve. Spike and recovery experiments were conducted to validate the efficacy of dose response curve.
Results and Discussion: Sensor response to both IL-8 and IL-10 spiked doses in pooled saliva showed a dose-dependent response to increasing concentrations of IL-8 and IL-10 respectively as illustrated by the Nyquist plots in Fig.1. The change in impedance with increasing doses of IL-8 and IL-10 in pooled human saliva lends to credence to the establishment of the presence and quantification of cytokines in saliva that can be used by clinicians and scientists alike in the further development of personalized medicine for severe asthmatics unresponsive to traditional asthmatic treatments.
Conclusion: This study presents a noninvasive electrochemical sensor for rapid and early detection of cytokines in pooled human saliva towards asthma phenotyping. The sensor exhibits a dose dependent response to IL-8 and IL-10, markers implicated in pathogenesis of asthma. Sensor capability was demonstrated with spike and recovery experiments illustrating the ability of the developed electrochemical sensor to detect and quantify cytokines in human saliva.

Figure 1