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Structural formula of corticosteroid derivatives and pyrrole. The A, B, C, and D in cortisol structure represents the four different rings in steroids.
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The binding affinity of molecularly imprinted polymers (MIPs) relies on the mechanisms and the extent of the functional monomer-template interactions present in the prepolymerization mixture. Thus, a clear understanding and optimizing the physiochemical parameters governing these interactions is key in designing and modeling MIPs with good selectiv...
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... of the steroid molecules may also affect the binding energy. From the structures of various corticosteroids analyzed (Figure 2), the implications of vari- ous functionalities for recognition by MIPs can be deduced. Gas phase binding energy calculation of cortisol with pyrrole show binding en- ergy of 10.9 kcal/mol. ...
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... The counterpoise could reduce the influence of basis set superposition error (BSSE). In the chemical structure of cortisol, five representative binding sites at C 3 , C 11 , C 17 , C 20 , and C 21 , atoms [48] could interact with 1,2-diaminobenzene through hydrogen bonds. The increase in the monomer ratio from 1:1-1:5 (= cortisol:1,2-diaminobenzene) induced a drastic decrease in binding energy (− 63.16 kcal/mol). ...
... More importantly, the MIP-OFET succeeded in the discrimination of cortisol from similar structural steroids (i.e., prednisolone). From the perspective of the steroid skeleton, a double bond between the C 1 and C 2 positions in steroidal ring A of prednisolone would change the rigidity of the steroid structural motif [48,50]. Therefore, the significant response changes in the MIP-OFET between cortisol and prednisolone could be explained by the difference in the rigidity of the steroid structural motif. ...
... 15 Computational studies have suggested that pyrrole-based polymers are suitable for fabricating cortisol-specific electrochemical MIP sensors. 16,17 The oxygen-containing electronegative functional groups present on the cortisol can interact with electropositive hydrogen attached to the nitrogen of pyrrole via hydrogen bonding, which helps in encapsulating cortisol in the polypyrrole (PPy) network during electropolymerization. Pyrrole can be electrochemically polymerized under ambient conditions, and the resulting PPy is stable and conductive in neutral pH, making it an excellent candidate for physiological MIPs and other sensing applications. ...
Cortisol is a major stress biomarker involved in the regulation of metabolic and immune responses. Readily accessible assays with sufficient quantitative and temporal resolution can assist in prevention, early diagnosis, and management of chronic diseases. Whereas conventional assays are costly in terms of time, labor, and capital, an electrochemical approach offers the possibility of miniaturization and detection at the point-of-care. Here, we investigate the biosensor application of molecularly imprinted polypyrrole (PPy) doped with hexacyanoferrate (HCF) and coupled to reduced graphene oxide functionalized with β-cyclodextrin (β-CD). β-CD provides an inclusion site for lipophilic cortisol and was electrochemically grafted simultaneous with reduction of GO. Next, PPy was electrochemically deposited in presence of cortisol template with HCF dopant ions serving as intrinsic redox probe. Thus, the sensor response was evaluated via changes of redox peak current in cyclic voltammetry and demonstrated a broad logarithmic detection range (5 pg/mL to 5000 ng/mL, R 2 = 0.995), with a sensitivity of 8.809 μA log-1 (ng/mL) cm-2 and LOD of 19.3 pM. The sensor was shown to be specific toward cortisol in reference to salivary cortisol concentration in saliva over structural analogues. The sensor was exhibited to determine cortisol in artificial saliva at normal and elevated levels. The good performance and facile electrochemical fabrication of this antibody- and external label-free interface are promising for the development of affordable point-of-care biosensors.
... The MIP sensor was further tested for 2,4-D detection in spiked drinking water, and it was found suitable, with satisfactory recovery values, in the range from 92 to 110%. The computational modelling, with the quantum chemical method, was employed for the development of a detection sensor by the theoretical study on the interaction between the cortisol (Fig. 1) steroid and Py, in MI pre-polymerization mixtures [59]. The authors chose steroids of the same ranges, namely, cortisol, progesterone, prednisolone, 21-deoxycortisol and 6-methylprednisolone (Fig. 1), for the investigation. ...
Molecularly imprinted polymers (MIPs) are an important class of compounds with wider sensing applications for the determination of substances ranging from small molecular masses to macro size. The hyphenation of MIP principle with other likewise conducting polymers yields the devices for sensing purposes. MIPs are robust against environmental conditions, more economical than natural receptors, and their preparation is also adequate for substances without natural receptors. Organic mediated MIPs compounds are of current interest, due to their applicability as quantification tools to determine electroactive substances in a variety of real samples. MIPs are highly selective for target molecules, mechanically strong, resistant to temperature and pressure, inert towards acids, bases, metal ions and organic solvents, highly stable for longer periods, and operative at room-temperature. Therefore, during past years, MIPs have been used as electrochemical and optical sensors, sorbents, solid phase media, and so on. Herein, there is a focus on the use of Pyrrole (Py) as a monomeric molecule to fabricate MIPs. Py or poly-Py (p-Py) based MIPs are synthesized and used in various capacities as chemo electrochemical sensors. A detailed discussion on the application of Py-mediated MIPs for the electrochemical determination of some organic compounds of therapeutic and environmental interest is herein presented as a review.
... While cortisol is charge neutral under physiological conditions, 7,26 it binds to its antibody through forming hydrogen bonds with the tryptophan residues located in the binding pocket, with tryptophan being the hydrogen bond donor. 27,28 As a result, the formation of the hydrogen bonds could lead to a charge redistribution, making the binding sites of the antibody more negatively charged, 9 and the whole antibody less positively charged, 29 therefore p-doping the sc-SWCNTs and shifting the FET characteristic curves toward more positive gate voltages. 18 In Fig. 3d, we observed a totally opposite trend in the ab-Au-sc-SWCNTs device. ...
Non-invasive detection and quantification of the stress hormone cortisol not only provides an assessment of stress level but also enables close monitoring of mental and physical health. Here, we report two types of field-effect transistors (FETs) based on semiconducting single-walled carbon nanotubes (sc-SWCNTs) as selective cortisol sensors. In one FET device configuration, cortisol antibody is directly attached to sc-SWCNTs. In the other, gold nanoparticles (Au NPs) are used as linkers between the antibody and the sc-SWCNTs to enhance the device conductance. We fabricated and characterized both device configurations to investigate how the nanomaterial interface to cortisol antibody influences the biosensor performance. We tested the sensors in artificial sweat and compared these two types of sensors in terms of limit of detection and sensitivity, and the results indicate that direct binding between antibody and sc-SWCNTs yields better biosensor characteristics.
... One sensing mechanism for cortisol relies on molecularly imprinted polymers (MIPs), where a polymer film is fabricated to produce recognition sites that are selective for the target molecule of interest [21][22][23][24][25][26][27][28]. Cortisol-selective MIPs can be applied as the sensing mechanism for electrochemical sensors [29][30][31][32][33]. Simulations have shown that pyrrole is a suitable precursor for cortisol MIP fabrication [34]. Pyrrole offers the ability to generate cortisolselective MIP films by controlled electropolymerization process directly onto an electrode transducer surface [35][36][37][38] and perform electrochemical sensing in neutral pH [39,40] as is needed for measuring sweat. ...
Cortisol is involved in regulating many human physiological functions, with cortisol imbalance capable of causing adverse mental and physical health conditions. Existing tools for monitoring of cortisol can assist in alerting the need for mediation strategies, but these typically require time consuming processes such as sample preparation followed by laboratory analysis. This work demonstrates a miniature flexible sensor patch incorporating electrode structures produced by high throughput roll-to-roll rotary screen-printing process, which are subsequently functionalized by electropolymerization of a polypyrrole/Prussian blue molecularly imprinted polymer for measuring cortisol by chronoamperometry. The developed single use sensor patch provides acceptable selectivity for cortisol and operates in artificial eccrine perspiration across a broad concentration range of 0.1-10000 ng/mL ( R ² = 0.916). In the application of measuring thermally induced sweat, the sensor provided results in agreement with the natural circadian rhythm of fluctuating cortisol.
... The mainstay of this framework is a surrogate model, upon which tailored data analytics methods can be further employed to quantify the relationship between synthesis parameters of e-MIPs and resulting sensing performances, thereby providing guidelines for e-MIPs synthesis. As a proof-of-concept, cortisol (template)−pyrrole (monomer) system is selected in this research due to the following reasons: (1) cortisol, popularly called "stress hormone", is a highly valuable biomarker to be measured for stress management and personalized health monitoring, 18 (2) pyrrole is a widely used monomer for electropolymerization, and computational studies show that pyrrole can form more specific and stronger interaction with cortisol than other interfering steroid hormones (e.g., progesterone, prednisolone), 19 (3) overoxidation of imprinted polypyrrole (PPy) can be used to extract cortisol from the polymer matrix, 20,21 which is more controllable and repeatable than other chemical removal methods. While there are various surrogate models available for elucidating the causative relation of input and output in the experimental data set, in this research, we used the Gaussian process (GP) because it is intrinsically probabilistic that it is capable of accounting for the effects of inevitable measurement variations and synthesis uncertainties when performing model training and prediction. ...
Molecularly imprinted polymers (MIPs), often called "synthetic antibodies", are highly attractive as artificial receptors with tailored biomolecular recognition to construct biosensors. Electropolymerization is a fast and facile method to directly synthesize MIP sensing elements in situ on the working electrode, enabling ultra-low-cost and easy-to-manufacture electrochemical biosensors. However, due to the high dimensional design space of electropolymerized MIPs (e-MIPs), the development of e-MIPs is challenging and lengthy based on trial and error without proper guidelines. Leveraging machine learning techniques in building the quantitative relationship between synthesis parameters and corresponding sensing performance, e-MIPs' development and optimization can be facilitated. We herein demonstrate a case study on the synthesis of cortisol-imprinted polypyrrole for cortisol detection, where e-MIPs are fabricated with 72 sets of synthesis parameters with replicates. Their sensing performances are measured using a 12-channel potentiostat to construct the subsequent data-driven framework. The Gaussian process (GP) is employed as the mainstay of the integrated framework, which can account for various uncertainties in the synthesis and measurements. The Sobol index-based global sensitivity is then performed upon the GP surrogate model to elucidate the impact of e-MIPs' synthesis parameters on sensing performance and interrelations among parameters. Based on the prediction of the established GP model and local sensitivity analysis, synthesis parameters are optimized and validated by experiment, which leads to remarkable sensing performance enhancement (1.5-fold increase in sensitivity). The proposed framework is novel in biosensor development, which is expandable and also generally applicable to the development of other sensing materials.
... 22 In addition, MIPs of PDAs can be made thin and continuous, a feature required to afford a short response time of chemical sensors. 22 In the last five years, chemically and mechanically stable ultrathin electrosynthesized MIP films of PDA have been prepared on various substrates and applied for sensitive detection of a number of small molecules including drugs, 12,25-30 herbicides, [31][32][33] hormone 34,35 and animal feed additive. 36 In this work, we analyzed the function of a p-PDA MIP electrochemical sensor in the rapid and sensitive measurement of NLX. ...
A molecularly imprinted polymer (MIP)-based electrochemical sensor featuring an electrochemically grafted para-phenylenediamine functional monomer on a reduced graphene oxide-gold nanoparticles composite modified screen printed electrode is reported. The morphology and properties of the sensing material were characterized with microscopy, spectroscopy and electrochemical techniques. A number of factors affecting the performance of the MIP sensor were examined and optimized. Under an optimized condition, the imprinted electrochemical sensor yielded homogenous naloxone binding sites with a dissociation constant of 8.6 μM, and responded linearly up to 8 μM naloxone, with a limit of detection of 0.16 μM. The sensor showed good run-to-run repeatability and batch-to-batch performance reproducibility with relative standard deviation of 5.7%–9.6% (n = 4) and <9% (n = 3), respectively. The imprinted sensor retained 95% and 85% of its performance when stored at ambient conditions for one and two weeks, respectively, demonstrating the sensor's good stability. Selectivity experiments showed that both the MIP sensor and non-imprinted polymer electrode had minimal response (<25%) to equal concentrations of structurally similar compounds such as morphine, naltrexone and noroxymorphone, indicating good selectivity of the MIP sensor towards naloxone. The MIP sensor was successfully used to quantify naloxone in artificial urine samples, yielding recoveries greater than 92%.
... 22 In addition, MIPs of PDAs can be made thin and continuous, a feature required to afford a short response time of chemical sensors. 22 In the last five years, chemically and mechanically stable ultrathin electrosynthesized MIP films of PDA have been prepared on various substrates and applied for sensitive detection of a number of small molecules including drugs, 12,25-30 herbicides, [31][32][33] hormone 34,35 and animal feed additive. 36 In this work, we analyzed the function of a p-PDA MIP electrochemical sensor in the rapid and sensitive measurement of NLX. ...
A molecularly imprinted polymer (MIP)-based electrochemical sensor featuring an electrochemically grafted para-phenylenediamine functional monomer on a reduced graphene oxide-gold nanoparticles composite modified screen printed electrode is reported. The morphology and properties of the sensing material were characterized with microscopy, spectroscopy and electrochemical techniques. A number of factors affecting the performance of the MIP sensor were examined and optimized. Under an optimized condition, the imprinted electrochemical sensor yielded homogenous naloxone binding sites with a dissociation constant of 8.6 μ M, and responded linearly up to 8 μ M naloxone, with a limit of detection of 0.16 μ M. The sensor showed good run-to-run repeatability and batch-to-batch performance reproducibility with relative standard deviation of 5.7%–9.6% (n = 4) and <9% (n = 3), respectively. The imprinted sensor retained 95% and 85% of its performance when stored at ambient conditions for one and two weeks, respectively, demonstrating the sensor’s good stability. Selectivity experiments showed that both the MIP sensor and non-imprinted polymer electrode had minimal response (<25%) to equal concentrations of structurally similar compounds such as morphine, naltrexone and noroxymorphone, indicating good selectivity of the MIP sensor towards naloxone. The MIP sensor was successfully used to quantify naloxone in artificial urine samples, yielding recoveries greater than 92%.
... The cortisol secretion in the body is also linked to immune, cardiovascular, skeletal, renal, as well as endocrine homeostasis. [22][23][24] The fluctuation of cortisol concentrations throughout the day is known as circadian rhythm. Cortisol levels are higher during the morning and decreases gradually during night. ...
Wearable sensors are becoming an important tool for healthcare monitoring as they can provide continuous monitoring of clinically important biomarkers released in the biofluids such as sweat, saliva, tears, urine and interstitial fluids (ISF). Development of smart sensing technologies for stress detection in daily life is find applications in various field including healthcare, defence and sports industries. Although different modalities for stress detection are performed in the clinical laboratories, the measurement of hormone release from glands of the endocrine system is receiving wide attention. Cortisol is considered as a biomarker of stress as the levels are spike in response to stressors. Although most of the cortisol released from adrenaline glands bound by corticosteroid-binding globulin (CBG), active form of free cortisol is also appearing in the biofluids (sweat, saliva, urine, tear, and ISF). Electrochemical biosensors, due to their relative small farm factors and sensitivity are focused for developing wearable biosensors for non-invasive monitoring of biochemical markers. Recent technological advancements in the field of electrochemical sensors and material engineering have contributed widely to the growth of new generation wearable point of care (POC) systems that can allow for early diagnosis. Receptor molecules including antibodies, enzyme fragments, molecularly imprinted polymers, and other biomimetic materials have been explored for electrochemical sensing of cortisol. Interfacing of theses sensing strategies into fabrics and flexible wearable patches for sweat cortisol analysis are also attempted. This mini review focuses on development made in the area of cortisol sensors using fabrics and flexible substrates potential for wearable sensor applications. An overview of cortisol secretion in the body and its availability in different biological fluids are also discussed. The issues associated with realizing complete wearable sensor devices are also explored. © 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
... The IUPAC name of corticosterone is (11β)-11,21-dihydroxypregn-4-ene-3,20-dione although it is also known as 11β,21-dihydroxyprogesterone or simply as 17-deoxycortisol . The adrenal gland produces this hormone with antiinflammatory and immunosuppressive properties [20,21,23,27,[30][31][32][35][36][37][39][40][41][42][43][44]. So far, there are a lot of articles related to structural, chemical and biological studies on glucocorticoids, from experimental studies by using spectroscopic and electrochemical techniques up to different theoretical studies because these species present dual regulation effects on the immune function which are strongly dependent on the concentration. ...
... Thus, experimental structures of corticosterone .and their derivatives were already reported [19,24,25,29] together with other theoretical studies on structure, descriptors and reactivity [22,26,37]. Additional studies on temperature effects in low-frequency Raman spectra and terahertz adsorption and Raman scattering were also reported for corticosteroid and mineralocorticoid hormones [33,34], respectively but, the complete vibrational assignments of corticosterone in the different media by using SQMFF methodology were no reported yet. ...
... Reasonable correlations were found among the predicted IR, Raman and UV spectra with the corresponding experimental ones [56]. The calculations of gap values [54] and some descriptors were performed, as suggested by Parr and Pearson [59][60][61][62][63][64][65][66][67][68], because the prediction of reactivities and behaviours in the three media are of interest for this hormone with anti-inflammatory and immunosuppressive properties [20,21,23,27,[30][31][32][35][36][37][39][40][41][42][43][44]. ...
In this work, structural, electronic, topological and vibrational properties of corticosterone hormone have been investigated in aqueous, ethanol and methanol solutions by using DFT calculations and experimental available infrared, attenuated total reflectance (ATR), Raman and Ultraviolet spectra. The properties predicted in the different solvents at the B3LYP/6-31G* level of theory were compared with those obtained in gas phase and, with others reported for steroids species at the same level of theory. The universal solvation model has evidenced higher solvation energy for corticosterone in aqueous solution and a higher value in methanol, as compared with the corresponding values to equilenin, equilin and estrone steroids in the same medium. Higher Mulliken charges on O atoms of C=O group of side chain are observed in the three solvents than the corresponding to C=O group of ring A while the MK charges on O atoms of OH group of ring C present higher values than the corresponding to O atoms of OH group of side chain. The natural bond orbital (NBO) studies have revealed a low stability of corticosterone in aqueous solution, as compared with the values in ethanol and methanol solutions, in total agreement with the higher solvation energy and dipole moment in this medium. On the other hand, the atoms in molecules (AIM) analyses support the lower stabilities of corticosterone in the three solutions because only five H bonds interactions different from of gas phase where six interactions are observed. The gap values suggests that corticosterone is most reactive in aqueous solution than the other solutions, as supported by the low stability and higher solvation energy and dipole moment values in this medium. This study shows clearly that the steroid species most reactive, equilenin and corticosterone, are characterized by a high global electrophilicity index value and low nucleophilicity index. Reasonable correlations in the predicted IR, Raman and UV spectra were observed, as compared with the corresponding experimental ones. Additionally, the complete vibrational assignments of all 159vibration modes of corticosterone together with the harmonic force fields and force constants in the different media are for the first time presented.
