A recent study published in the journal Biosensors and bioelectronics examines the advancement of gold-doped molecularly imprinted electrochemical nanosensors for rapid and sensitive detection of cortisol, a steroid hormone.

Study: Gold-doped nano-molecular-fingerprint electrochemical sensor for rapid and ultra-sensitive detection of cortisol. Image Credit: Kateryna Kon/Shutterstock.com

In the sensor, target cortisol binds to dots imprinted in the polymer, altering the current of redox-active probes.

With this approach, high-density gold nanoparticles are distributed around the binding cavities of these gold-doped MIP sensors.

Reducing gold in situ promoted polymerization, increasing the effective area of ​​the sensor. When subjected to redox reagents, it also facilitated charge transfer.

Sensing responsiveness and sensitivity improved by effectively preventing charge transfer when cortisol occupied the cavities. Additionally, this sensor demonstrated significant adhesion for cortisol uptake, linear detection range of 1-500 nM, and selectivity among other steroid hormones that bear a close resemblance.

The sensor determined normal and increased cortisol levels in peak saliva. The simple non-antibody cortisol detection approach is extremely sensitive and selective and ideal for point-of-care testing.

Cortisol: a steroid hormone

The adrenal gland produces cortisol in response to stress or anxiety. It modulates blood pressure, blood sugar and metabolism. Cortisol deficiency or excess is linked to PTSD, Cushing’s disease and CFS and high cortisol levels can be used to diagnose SARS-CoV-2 disease. Non-plasma bound cortisol is measured in saliva and measurement of salivary cortisol is reliable and non-invasive.

Existing cortisol measurement methods

Existing clinical cortisol measurement protocols are time-consuming and expensive, requiring patients to submit urine or saliva samples for testing.

To achieve detection limits below ng/mL, standard approaches rely on time-consuming column chromatography techniques. However, it is time consuming and, based on cross-reactivity with other comparable steroid hormones, it has relatively low detection selectivity.

Besides ELISA, lateral flow tests and other immunosensors are under development. These immunosensors detect cortisol using antibodies or aptamers, tend to have high costs, and have a short lifespan due to environmental instability.

To replace antibodies, another option is to use a synthetic polymer with biorecognition sites for specific binding to the target. Point-of-care applications are achievable when MIP is combined with electrochemical sensing technologies.

MIP-based electrochemical cortisol sensors have been demonstrated in a few publications. Wearable MIP cortisol transistors fabricated by UV polymerization of a methyl methacrylate-based copolymer have been shown to be able to detect sweat cortisol in the range of 0.01 M to 5 M. However, the limitations detection of these cortisol MIP sensors are not satisfactory, and the manufacturing procedure is difficult

A new MIP cortisol sensor doped with gold nanoparticles

According to the researchers, this gold-doped sensor can accurately detect cortisol. It has many amine groups that form hydrogen bonds with cortisol molecules during polymerization.

Poly-o-PD is also non-toxic and structurally stable, allowing for a tight, tight polymer matrix for fast sensor response times. AuNP doping improves the transit of electrons between the redox probes and the electrodes.

The attachment of the target molecules to the imprinted cavities modifies the reactivity of the current. These targets can also reduce electron transit through AuNPs, thereby increasing detection sensitivity. The use of prefabricated AuNPs to polymerize MIPs has been described in a few studies.

Instead of reducing the effective area of ​​the MIP, the co-polymerization actually improved it. For non-invasive monitoring of steroid hormones in clinical settings, the sensor correctly recognized normal and elevated cortisol concentrations in artificial saliva.

Conclusion

In this study, electrochemical cortisol sensors centered on cortisol-imprinted polymers embedded in gold nanoparticles were presented by the research team. The sensor was produced by electropolymerization with reduction of gold in situ.

Adding gold nanoparticles to the MIP layer improved sensing ability by increasing active surface area, enhancing electron transport through the MIP, and effectively modulating current in response to targeted cortisol capture. the [email protected] The cortisol sensor has a linear range from 1 pM to 500 nM and a detection limit of 200 fM, which was much better than previous sensors.

The sensor also detected cortisol in fake saliva samples with good recovery rates. On a discrete GCE, an effective cortisol sensor has currently been shown. For point-of-care applications, the gold-doped sensing technique can be used to screen print the electrodes (SPE).

The gold doped approach can also be simply adjusted to capture many targets for multiplexed detection. The sensing capabilities and manufacturing process of the sensor demonstrate the [email protected]the promise of inexpensive, non-invasive stress detection in body fluids.

Reference

Yeasmin, S. et al. (2022). Gold-doped nano-molecular-fingerprint electrochemical sensor for fast and ultra-sensitive detection of cortisol. Biosensors and bioelectronics. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0956566322001828?via%3Dihub

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