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Schematic representation of DNA SL/Aptamer biosensor construction for cortisol detection. Initially, a clean gold electrode is modified with a layer of DNA-modified AuNPs, which is later functionalized with a complementary DNA aptamer, which in the presence of cortisol changes conformation modifying the electrochemical response of the system. This modification of electrochemical response is later used to quantify cortisol.
Source publication
Monitoring cortisol is one of the current challenges in medicine, as this hormone plays an essential role in several physiological processes. One of the main interests is the accurate clinical diagnosis of stress and anxiety, as the patients release this hormone in body fluids such as saliva or sweat. An electrochemical biosensor for cortisol detec...
Contexts in source publication
Context 1
... the DNA SL improves the kinetics of electron transfer 8 , which can be easily affected by the recognition event, generating a better analytical response. The general construction concept of the biosensor is shown in Figure 1. ...
Context 2
... an electrochemical aptasensor was built on an Au surface modified with DNA SL containing AuNPs throughout cycles of growth based on the interaction between DNA sequences, followed by the modification with a specific aptamer for cortisol. As a result, the amount of DNA on the electrode surface was 7.8 pmol/cm -2 for one growing cycle, and the amount of DNA was proportional to the number of the growing cycle, as shown in Figure 1S. The cyclic voltammograms were recorded with a different number of the growing cycles, as shown in Figure 2S. ...
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Citations
... Operational parameters are required while applying a DNA-based linker. These parameters are largely influenced by the nature of the buffer, pH, and ionic strength [50]. ...
As a steroid hormone, cortisol has a close relationship with the stress response, and therefore, can be used as a biomarker for early detection of stress. An electrochemical immunosensor is one of the most widely used methods to detect cortisol, with antibodies as its bioreceptor. Apart from conventional laboratory-based methods, the trend for cortisol detection has seemed to be exploiting antibodies and aptamers. Both can provide satisfactory performance with high selectivity and sensitivity, but they still face issues with their short shelf life. Molecularly imprinted polymers (MIPs) have been widely used to detect macro- and micro-molecules by forming artificial antibodies as bioreceptors. MIPs are an alternative to natural antibodies, which despite demonstrating high selectivity and a low degree of cross-reactivity, often also show a high sensitivity to the environment, leading to their denaturation. MIPs can be prepared with convenient and relatively affordable fabrication processes. They also have high durability in ambient conditions, a long shelf life, and the ability to detect cortisol molecules at a concentration as low as 2 ag/mL. By collecting data from the past five years, this review summarizes the antibody and aptamer-based amperometric sensors as well as the latest developments exploiting MIPs rather than antibodies. Lastly, factors that can improve MIPs performance and are expected to be developed in the future are also explained.
The stressful conditions of today-life make it urgent the timely prevention and treatment of many physiological and psychological disorders related to stress. According to the significant progress made in the near future, rapid, accurate, and on-spot measurement of cortisol hormone as a dominant stress biomarker using miniaturized digital devices is not far from expected. With a special potency in the fields of diagnosis and healthcare monitoring, aptamer-mediated biosensors (aptasensors) are promising for the quantitative monitoring of cortisol levels in the different matrices (sweat, saliva, urine, cerebrospinal fluid, blood serum, etc.). Accordingly, this in-depth study reviews the superior achievements in the aptasensing strategies to detect cortisol hormone with the synergism of diverse two/three dimensional nanostructured materials, enzymatic amplification components, and antibody motifs. The represented discussions offer a universal perspective to achieve lab-on-chip aptasensing arrays as future user-friendly skin-patchable electronic gadgets for on-site and real-time quantification of cortisol levels.
Introduction
Cortisol is one of the most prominent biomarkers that can be used for the detection of psychological stress and related disorders. Besides this, it plays an important role in many physiological processes including immunomodulation and fat metabolism. Thus, monitoring of cortisol levels can be used to indicate pathological conditions such as Cushing’s syndrome. Due to the limitations of conventional technologies, there has been a gradual shift toward the development of point-of-care (PoC) biosensors for continuous cortisol monitoring.
Areas Covered
This review aims at discussing recent breakthroughs toward the development of PoC sensors for cortisol monitoring. The clinical significance of cortisol has been summarized along with its various sample sources. Some recent advancements in different formats (wearable and non-wearable) PoC biosensors for cortisol detection have been discussed followed by the challenges associated with the commercialization of these technologies.
Expert Opinion
Electrochemical PoC devices have recently emerged as powerful tools for continuous monitoring of cortisol that can be utilized for stress management and treatment of related disorders. However, there are many challenges that should be addressed before such devices can be deployed at mass level, such as inter-individual variability, changing the device calibration with the circadian rhythm, interference from other endocrine moieties, etc.
