COVID-19 and Cushing’s syndrome: recommendations for a special population with endogenous glucocorticoid excess

Rosario Pivonello,a,b Rosario Ferrigno,a Andrea M Isidori,c Beverly M K Biller,d Ashley B Grossman,e,f and Annamaria Colaoa,b

Over the past few months, COVID-19, the pandemic disease caused by severe acute respiratory syndrome coronavirus 2, has been associated with a high rate of infection and lethality, especially in patients with comorbidities such as obesity, hypertension, diabetes, and immunodeficiency syndromes.

These cardiometabolic and immune impairments are common comorbidities of Cushing’s syndrome, a condition characterised by excessive exposure to endogenous glucocorticoids. In patients with Cushing’s syndrome, the increased cardiovascular risk factors, amplified by the increased thromboembolic risk, and the increased susceptibility to severe infections, are the two leading causes of death.

In healthy individuals in the early phase of infection, at the physiological level, glucocorticoids exert immunoenhancing effects, priming danger sensor and cytokine receptor expression, thereby sensitising the immune system to external agents. However, over time and with sustained high concentrations, the principal effects of glucocorticoids are to produce profound immunosuppression, with depression of innate and adaptive immune responses. Therefore, chronic excessive glucocorticoids might hamper the initial response to external agents and the consequent activation of adaptive responses. Subsequently, a decrease in the number of B-lymphocytes and T-lymphocytes, as well as a reduction in T-helper cell activation might favour opportunistic and intracellular infection. As a result, an increased risk of infection is seen, with an estimated prevalence of 21–51% in patients with Cushing’s syndrome. Therefore, despite the absence of data on the effects of COVID-19 in patients with Cushing’s syndrome, one can make observations related to the compromised immune state in patients with Cushing’s syndrome and provide expert advice for patients with a current or past history of Cushing’s syndrome.

Fever is one of the hallmarks of severe infections and is present in up to around 90% of patients with COVID-19, in addition to cough and dyspnoea. However, in active Cushing’s syndrome, the low-grade chronic inflammation and the poor immune response might limit febrile response in the early phase of infection. Conversely, different symptoms might be enhanced in patients with Cushing’s syndrome; for instance, dyspnoea might occur because of a combination of cardiac insufficiency or weakness of respiratory muscles. Therefore, during active Cushing’s syndrome, physicians should seek different signs and symptoms when suspecting COVID-19, such as cough, together with dysgeusia, anosmia, and diarrhoea, and should be suspicious of any change in health status of their patients with Cushing’s syndrome, rather than relying on fever and dyspnoea as typical features.

The clinical course of COVID-19 might also be difficult to predict in patients with active Cushing’s syndrome. Generally, patients with COVID-19 and a history of obesity, hypertension, or diabetes have a more severe course, leading to increased morbidity and mortality. Because these conditions are observed in most patients with active Cushing’s syndrome, these patients might be at an increased risk of severe course, with progression to acute respiratory distress syndrome (ARDS), when developing COVID-19. However, a key element in the development of ARDS during COVID-19 is the exaggerated cellular response induced by the cytokine increase, leading to massive alveolar–capillary wall damage and a decline in gas exchange. Because patients with Cushing’s syndrome might not mount a normal cytokine response, these patients might parodoxically be less prone to develop severe ARDS with COVID-19. Moreover, Cushing’s syndrome and severe COVID-19 are associated with hypercoagulability, such that patients with active Cushing’s syndrome might present an increased risk of thromboembolism with COVID-19. Consequently, because low molecular weight heparin seems to be associated with lower mortality and disease severity in patients with COVID-19, and because anticoagulation is also recommended in specific conditions in patients with active Cushing’s syndrome, this treatment is strongly advised in hospitalised patients with Cushing’s syndrome who have COVID-19. Furthermore, patients with active Cushing’s syndrome are at increased risk of prolonged duration of viral infections, as well as opportunistic infections, particularly atypical bacterial and invasive fungal infections, leading to sepsis and an increased mortality risk, and COVID-19 patients are also at increased risk of secondary bacterial or fungal infections during hospitalisation. Therefore, in cases of COVID-19 during active Cushing’s syndrome, prolonged antiviral treatment and empirical prophylaxis with broad-spectrum antibiotics should be considered, especially for hospitalised patients (panel ).

Panel

Risk factors and clinical suggestions for patients with Cushing’s syndrome who have COVID-19

Reduction of febrile response and enhancement of dyspnoea

Rely on different symptoms and signs suggestive of COVID-19, such as cough, dysgeusia, anosmia, and diarrhoea.

Prolonged duration of viral infections and susceptibility to superimposed bacterial and fungal infections

Consider prolonged antiviral and broad-spectrum antibiotic treatment.

Impairment of glucose metabolism (negative prognostic factor)

Optimise glycaemic control and select cortisol-lowering drugs that improve glucose metabolism. Hypertension (negative prognostic factor) Optimise blood pressure control and select cortisol-lowering drugs that improve blood pressure.

Thrombosis diathesis (negative prognostic factor)

Start antithrombotic prophylaxis, preferably with low-molecular-weight heparin treatment.

Surgery represents the first-line treatment for all causes of Cushing’s syndrome, but during the pandemic a delay might be appropriate to reduce the hospital-associated risk of COVID-19, any post-surgical immunodepression, and thromboembolic risks. Because immunosuppression and thromboembolic diathesis are common Cushing’s syndrome features, during the COVID-19 pandemic, cortisol-lowering medical therapy, including the oral drugs ketoconazole, metyrapone, and the novel osilodrostat, which are usually effective within hours or days, or the parenteral drug etomidate when immediate cortisol control is required, should be temporarily used. Nevertheless, an expeditious definitive diagnosis and proper surgical resolution of hypercortisolism should be ensured in patients with malignant forms of Cushing’s syndrome, not only to avoid disease progression risk but also for rapidly ameliorating hypercoagulability and immunospuppression; however, if diagnostic procedures cannot be easily secured or surgery cannot be done for limitations of hospital resources due to the pandemic, medical therapy should be preferred. Concomitantly, the optimisation of medical treatment for pre-existing comorbidities as well as the choice of cortisol-lowering drugs with potentially positive effects on obesity, hypertension, or diabates are crucial to improve the eventual clinical course of COVID-19.

Once patients with Cushing’s syndrome are in remission, the risk of infection is substantially decreased, but the comorbidities related to excess glucocorticoids might persist, including obesity, hypertension, and diabetes, together with thromboembolic diathesis. Because these are features associated with an increased death risk in patients with COVID-19, patients with Cushing’s syndrome in remission should be considered a high-risk population and consequently adopt adequate self-protection strategies to minimise contagion risk.

In conclusion, COVID-19 might have specific clinical presentation, clinical course, and clinical complications in patients who also have Cushing’s syndrome during the active hypercortisolaemic phase, and therefore careful monitoring and specific consideration should be given to this special, susceptible population. Moreover, the use of medical therapy as a bridge treatment while waiting for the pandemic to abate should be considered.

Acknowledgments

RP reports grants and personal fees from Novartis, Strongbridge, HRA Pharma, Ipsen, Shire, and Pfizer; grants from Corcept Therapeutics and IBSA Farmaceutici; and personal fees from Ferring and Italfarmaco. AMI reports non-financial support from Takeda and Ipsen; grants and non-financial support from Shire, Pfizer, and Corcept Therapeutics. BMKB reports grants from Novartis, Strongbridge, and Millendo; and personal fees from Novartis and Strongbridge. AC reports grants and personal fees from Novartis, Ipsen, Shire, and Pfizer; personal fees from Italfarmaco; and grants from Lilly, Merck, and Novo Nordisk. All other authors declare no competing interests.

References

1. Kakodkar P, Kaka N, Baig MN. A comprehensive literature review on the clinical presentation, and management of the pandemic coronavirus disease 2019 (COVID-19) Cureus. 2020;12 [PMC free article] [PubMed[]
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3. Cain DW, Cidlowski JA. Immune regulation by glucocorticoids. Nat Rev Immunol. 2017;17:233–247. [PubMed[]
4. Hasenmajer V, Sbardella E, Sciarra F, Minnetti M, Isidori AM, Venneri MA. The immune system in Cushing’s syndrome. Trends Endocrinol Metab. 2020 doi: 10.1016/j.tem.2020.04.004. published online May 6, 2020. [PubMed] [CrossRef[]
5. Ye Q, Wang B, Mao J. The pathogenesis and treatment of the ‘Cytokine Storm’ in COVID-19. J Infect. 2020;80:607–613. [PMC free article] [PubMed[]
6. Tang N, Bai H, Chen X, Gong J, Li D, Sun Z. Anticoagulant treatment is associated with decreased mortality in severe coronavirus disease 2019 patients with coagulopathy. J Thromb Haemost. 2020;18:1094–1099. [PubMed[]
7. Isidori AM, Minnetti M, Sbardella E, Graziadio C, Grossman AB. Mechanisms in endocrinology: the spectrum of haemostatic abnormalities in glucocorticoid excess and defect. Eur J Endocrinol. 2015;173:R101–R113. [PubMed[]
8. Nieman LK, Biller BM, Findling JW. Treatment of Cushing’s syndrome: an endocrine society clinical practice guideline. J Clin Endocrinol Metab. 2015;100:2807–2831. [PMC free article] [PubMed[]
9. Pivonello R, De Leo M, Cozzolino A, Colao A. The treatment of Cushing’s disease. Endocr Rev. 2015;36:385–486. [PMC free article] [PubMed[]
10. Newell-Price J, Nieman L, Reincke M, Tabarin A. Endocrinology in the time of COVID-19: management of Cushing’s syndrome. Eur J Endocrinol. 2020 doi: 10.1530/EJE-20-0352. published online April 1. [PubMed] [CrossRef[]

Successful Cushing’s Surgery Leads to Better Bone Density

Biomarkers in a majority of Cushing’s syndrome patients with surgically induced disease remission showed a high rate of bone turnover and greater bone mineral density one and two years later, a study reports.

Before treatment, these patients were found to have greater bone degradation and poorer bone formation, as can be common to disease-related bone disorders.

Researchers believe their work is the first study of its kind, “and the data obtained will be instrumental for clinicians who care for patients with Cushing’s syndrome.”

The study, “The Effect of Biochemical Remission on Bone Metabolism in Cushing’s Syndrome: A 2‐Year Follow‐Up Study,” was published in the Journal of Bone and Mineral Research.

Two common co-conditions of Cushing’s syndrome are osteopenia, a loss of bone mass, and osteoporosis, in which the body makes too little bone, loses too much bone, or both. Studies suggest up to 80% of people with Cushing’s have evidence of reduced bone mineral density affecting the entire skeleton.

However, few risk factors to predict bone health have been identified so far, and guidelines for osteoporosis management due to Cushing’s are lacking. Uncertainty as to the natural course of osteoporosis once a diagnosis of Cushing’s syndrome has been made is also still evident.

Investigators at the University of Munich, reportedly for a first time, analyzed the natural course of bone mineral density and bone turnover (recycling) in a group of people with endogenous Cushing’s syndrome — which refers to the disease caused by excess cortisol in the bloodstream, often due to a tumor in the adrenal or pituitary glands.

They examined medical records of 89 Cushing syndrome patients with a mean age of 44, of which 74% were women. Of these, 65% had pituitary Cushing’s (Cushing’s disease), 28% had adrenal, and 7% had ectopic Cushing’s, which is caused by tumors outside the adrenal or pituitary glands. A group of 71 age- and sex-matched healthy participants were included as controls.

In all patients, blood samples were collected at the time of diagnosis (baseline) and one and two years after removing one or both adrenal glands or moving tumors affecting the pituitary gland. Blood samples were analyzed for biomarkers related to bone formation and degradation (resorption).

At the study’s beginning, the mean levels of two bone formation markers, osteocalcin and intact PINP, were significantly decreased in patients compared with controls, whereas the bone formation marker alkaline phosphatase was increased.

Both markers for bone degradation — called CTX and TrAcP — were also high, which demonstrated “increased bone resorption and decreased bone formation in [Cushing’s syndrome],” the team wrote.

While bone markers were similar in participants with a reduced bone mass relative to those with a normal bone mass, bone mineral density was lower overall. Bone mineral density was significantly lower in the neck and spine compared with the femur (thigh bone). Normal bone mineral density was reported in 28 (32%) patients, while 46 (52%) had osteopenia, and the remaining 15 (17%) lived with osteoporosis.

A history of low-trauma bone fractures due to osteoporosis occurred in 17 (19%) patients, taking place shortly before diagnosis in more than half of these (58%) people, and more than two years before a Cushing’s diagnosis in the remaining group (42%).

Compared to patients without fractures, those with fractures had a significantly lower T‐score, a bone density measure that represents how close a person is to average peak bone density. While Cushing’s subtype, age, or body mass index (BMI, body fat based on height) did not differ between groups, men had a significantly higher risk of fractures than women (35% of men vs. 14% of women).

Both disease severity and duration did not contribute to fractures rates, but urinary free cortisol (a circulating cortisol measure) was significantly higher in patients with a low T‐score.

At the one year after tumor removal, which led to Cushing’s remission based on blood tests, a significant increase in bone formation markers was reported. These biomarkers decreased slightly at two years post-surgery, but remained elevated.

At the beginning of the study, bone resorption markers were mildly increased, which rose further one year after surgery before returning almost to normal levels by two years. In parallel, bone density measures conducted in 40 patients showed a matching increase in T-score, particularly in the spine.

After two years, bone mineral density improved in 78% of patients, and T-scores improved in 45% of them. No fractures occurred after Cushing’s treatment, and there was no significant correlation between bone turnover markers and better bone mineral density.

“This study analyzes for the first time in a comprehensive way bone turnover markers during the course of [Cushing’s syndrome],” the researchers wrote. “Our data suggest that the phase immediately after remission from [Cushing’s syndrome] is characterized by a high rate of bone turnover, resulting in a spontaneous net increase in bone mineral density in the majority of patients.”

These results “will influence future therapeutic strategies in patients” with Cushing’s syndrome, they added.

 

Steve holds a PhD in Biochemistry from the Faculty of Medicine at the University of Toronto, Canada. He worked as a medical scientist for 18 years, within both industry and academia, where his research focused on the discovery of new medicines to treat inflammatory disorders and infectious diseases. Steve recently stepped away from the lab and into science communications, where he’s helping make medical science information more accessible for everyone.

Hydrocortisone in Granule Form Effectively Treats Childhood Adrenal Insufficiency

The treatment of adrenal insufficiency with hydrocortisone granules in children with congenital adrenal hyperplasia (CAH) was associated with an absence of adrenal crises and normal growth patterns over a 2-year period, according to study findings published in The Journal of Clinical Endocrinology and Metabolism.

The study included a total of 17 children with CAH and 1 child with hypopituitarism. All included participants were <6 years old who were receiving current adrenocortical replacement therapy, including hydrocortisone with or without fludrocortisone. Hydrocortisone medications used in this population were converted from pharmacy compounded capsules to hydrocortisone granules without changing the dose.

These study participants were followed by study investigators for 2 years. Glucocorticoid replacement therapy was given three times a day for a median treatment duration of 795 days. Treatment was adjusted by 3 monthly 17-hydroxyprogesterone (17-OHP) profiles in children with CAH.

There were a 150 follow-up visits throughout the study. At each visit, participants underwent assessments that measured hydrocortisone dose, height, weight, pubertal status, adverse events, and incidence of adrenal crisis.

A total of 40 follow-up visits had changes in hydrocortisone doses based on salivary measurements (n=32) and serum 17-OHP levels (n=8).

At time of study entry, the median daily doses of hydrocortisone were 11.9 mg/m2 for children between the ages of 2 to 8 years, 9.9 mg/m2 for children between 1 month and 2 years, and 12.0 mg/m2 for children <28 days of age. At the end of the study, the respective doses for the 3 age groups were 10.2, 9.8, and 8.6.

The investigators observed no trends in either accelerated growth or reduced growth; however, 1 patient with congenital renal hypoplasia and CAH did show reduced growth. While 193 treatment-emergent adverse events, including pyrexia, gastroenteritis, and viral upper respiratory tract infection, were reported in 14 patients, there were no observed adrenal crises.

Limitations of this study included the small sample size as well as the relatively high drop-out rate of the initial sample.

The researchers concluded that “hydrocortisone granules are an effective treatment for childhood adrenal insufficiency providing the ability to accurately prescribe pediatric appropriate doses.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Neumann U, Braune K, Whitaker MJ, et al. A prospective study of children 0-7 years with CAH and adrenal insufficiency treated with hydrocortisone granules. Published online September 4, 2020. J Clin Endocrinol Metab. doi:10.1210/clinem/dgaa626

Short-Term Oral Corticosteroid Use Tied to Higher Risks of GI Bleeds, Sepsis, Heart Failure

Study Authors: Tsung-Chieh Yao, Ya-Wen Huang, et al.; Beth I. Wallace, Akbar K. Waljee

Target Audience and Goal Statement: Primary care physicians, rheumatologists, pulmonologists, dermatologists, gastroenterologists, cardiologists

The goal of this study was to examine the associations between oral corticosteroid bursts and severe adverse events among adults in Taiwan.

Question Addressed:

  • What were the associations between steroid bursts and severe adverse events, specifically gastrointestinal (GI) bleeding, sepsis, and heart failure?

Study Synopsis and Perspective:

It has long been known that long-term use of corticosteroids can be both effective and toxic. Long-term use is associated with adverse effects such as infections, GI bleeding/ulcers, cardiovascular disease (CVD), Cushing syndrome, diabetes and metabolic syndromes, cataracts, glaucoma, and osteoporosis. Most clinical practice guidelines caution against long-term steroid use unless medically necessary.

Action Points

  • In a retrospective cohort study and self-controlled case series, prescriptions for oral steroid bursts were found to be associated with increased risks for gastrointestinal bleeding, sepsis, and heart failure within the first month after initiation, despite a median exposure of just 3 days.
  • Note that the risks were highest 5 to 30 days after exposure, and attenuated during the subsequent 31 to 90 days.

Instead, clinical practice guidelines recommend steroid bursts for inflammatory ailments such as asthma, inflammatory bowel disease, and rheumatoid arthritis. Waljee and colleagues noted in 2017 that they are most commonly used for upper respiratory infections, suggesting that many people are receiving steroids in the real world.

In a retrospective cohort study and self-controlled case series, prescriptions for oral steroid bursts — defined as short courses of oral corticosteroids for 14 or fewer days — were found to be associated with increased risks for GI bleeding, sepsis, and heart failure within the first month after initiation, despite a median exposure of just 3 days, according to Tsung-Chieh Yao, MD, PhD, of Chang Gung Memorial Hospital in Taoyuan, and colleagues.

The risks were highest 5 to 30 days after exposure, and attenuated during the subsequent 31 to 90 days, they reported in Annals of Internal Medicine.

The self-controlled case series was based on national medical claims records. Included were adults, ages 20-64, covered by Taiwan’s National Health Insurance in 2013-2015.

Out of a population of more than 15.8 million, study authors identified 2,623,327 people who received a steroid burst during the study period. These individuals were age 38 on average, and 55.3% were women. About 85% had no baseline comorbid conditions.

The most common indications for the steroid burst were skin disorders and respiratory tract infections.

The incidence rates among patients prescribed steroid bursts were 27.1 per 1,000 person-years for GI bleeding (incidence rate ratio [IRR] 1.80, 95% CI 1.75-1.84), 1.5 per 1,000 person-years for sepsis (IRR 1.99, 95% CI 1.70-2.32), and 1.3 per 1,000 person-years for heart failure (IRR 2.37, 95% CI 2.13-2.63).

Absolute risk elevations were similar in patients with and without comorbid conditions, meaning that the potential for harm was not limited to those at high risk for these adverse events.

The study authors acknowledged that they could not adjust for disease severity and major lifestyle factors such as alcohol use, smoking, and body mass index; because these factors were static, the effect could be eliminated using the self-controlled case series design. Their reliance on prescription data also meant they could not tell if patients actually complied with oral corticosteroid therapy. Furthermore, the exclusion of the elderly and younger populations also left room for underestimation of the risks of steroid bursts, they said.

Source References: Annals of Internal Medicine 2020; DOI: 10.7326/M20-0432

Editorial: Annals of Internal Medicine 2020; DOI: 10.7326/M20-4234

Study Highlights and Explanation of Findings:

Over the 3-year study period, steroid bursts were commonly prescribed to adults. Such prescriptions were written for common conditions, including skin disorders and upper respiratory tract infections. The highest risks for GI bleeding, sepsis, and heart failure occurred within the first month after receipt of the steroid burst, and this risk was attenuated during the subsequent 31 to 90 days.

“Our findings are important for physicians and guideline developers because short-term use of oral corticosteroids is common and the real-world safety of this approach remains unclear,” the researchers wrote. Notably, one corticosteroid that fits the bill is dexamethasone — a medication that holds promise for the treatment of critically ill COVID-19 patients, although it is not generally prescribed orally for these patients.

Based on preliminary results, the NIH’s COVID-19 treatment guidelines panel recommended the use of “dexamethasone (at a dose of 6 mg per day for up to 10 days) in patients with COVID-19 who are mechanically ventilated and in patients with COVID-19 who require supplemental oxygen but who are not mechanically ventilated.” In addition, they recommend “against using dexamethasone in patients with COVID-19 who do not require supplemental oxygen.”

“We are now learning that bursts as short as 3 days may increase risk for serious AEs [adverse events], even in young and healthy people. As providers, we must reflect on how and why we prescribe corticosteroids to develop strategies that prevent avoidable harms,” wrote Beth Wallace, MD, and Akbar Waljee, MD, both of the VA Ann Arbor Healthcare System and Michigan Medicine.

On the basis of the reported risk differences in the study, Wallace and Waljee calculated that one million patients exposed to corticosteroid bursts experienced 41,200 GI bleeding events, 400 cases of sepsis, and 4,000 cases of new heart failure per year that were directly attributed to this brief treatment.

“Although many providers already avoid corticosteroids in elderly patients and those with comorbid conditions, prescribing short bursts to ‘low-risk’ patients has generally been viewed as innocuous, even in cases where the benefit is unclear. However, Yao and colleagues provide evidence that this practice may risk serious harm, making it difficult to justify in cases where corticosteroid use lacks evidence of meaningful benefit,” they wrote in an accompanying editorial.

“Medication-related risks for AEs can, of course, be outweighed by major treatment benefit. However, this study and prior work show that corticosteroid bursts are frequently prescribed for self-limited conditions, where evidence of benefit is lacking,” Wallace and Waljee noted.

“As we reflect on how to respond to these findings, it is useful to note the many parallels between use of corticosteroid bursts and that of other short-term medications, such as antibiotics and opiates. All of these treatments have well-defined indications but can cause net harm when used — as they frequently are — when evidence of benefit is low,” they emphasized.

Last Updated August 07, 2020
Reviewed by Dori F. Zaleznik, MD Associate Clinical Professor of Medicine (Retired), Harvard Medical School, Boston

From https://www.medpagetoday.org/primarycare/generalprimarycare/87959?xid=nl_mpt_DHE_2020-08-08&eun=g1406328d0r&utm_term=NL_Daily_DHE_dual-gmail-definition&vpass=1

Smart, Soft Contact Lens For Wireless Immunosensing of Cortisol

Abstract

Despite various approaches to immunoassay and chromatography for monitoring cortisol concentrations, conventional methods require bulky external equipment, which limits their use as mobile health care systems. Here, we describe a human pilot trial of a soft, smart contact lens for real-time detection of the cortisol concentration in tears using a smartphone. A cortisol sensor formed using a graphene field-effect transistor can measure cortisol concentration with a detection limit of 10 pg/ml, which is low enough to detect the cortisol concentration in human tears. In addition, this soft contact lens only requires the integration of this cortisol sensor with transparent antennas and wireless communication circuits to make a smartphone the only device needed to operate the lens remotely without obstructing the wearer’s view. Furthermore, in vivo tests using live rabbits and the human pilot experiment confirmed the good biocompatibility and reliability of this lens as a noninvasive, mobile health care solution.

INTRODUCTION

The steroid hormone, cortisol, which is known as a stress hormone, is secreted by the adrenal gland when people are stressed psychologically or physically (1). This secretion occurs when the adrenal gland is stimulated by adrenocorticotropic hormone, which is secreted by the pituitary gland when it is stimulated by the corticotropin-releasing hormone secreted by the hypothalamus. This serial cortisol secretion system is referred to as a hypothalamus–pituitary gland–adrenal gland axis, which is affected by chronic stress, resulting in abnormal secretion of cortisol (23). The accumulation of cortisol caused by the abnormal secretion of cortisol increases the concentrations of fat and amino acid, which can result in diverse severe diseases (e.g., Cushing’s disease, autoimmune disease, cardiovascular complications, and type 2 diabetes) and neurological disorders (such as depression and anxiety disorders) (27). In contrast, abnormally low cortisol levels can lead to Addison’s disease, which results in hypercholesterolemia, weight loss, and chronic fatigue (8). In addition, it was recently reported that plasma cortisol can be correlated to the prognosis of traumatic brain injury (9). Furthermore, the extent of cortisol secretion varies from person to person, and it changes continuously (1011). Thus, developing health care systems for real-time monitoring of the cortisol level has been explored extensively over the past decade as the key to the quantitative analysis of stress levels. Although various efforts have led to the development of cortisol sensors that can measure the concentration of cortisol in blood, saliva, sweat, hair, urine, and interstitial fluid (1217), the accurate measurement of cortisol concentrations has been limited because of the difficulties associated with the transportation and storage of cortisol as well as the instability of the biologically active cortisol in these body fluids at room temperature. In addition, these conventional sensing methods require bulky equipment for the extraction and analysis of these body fluids, which is not suitable for mobile health care systems (1218). Therefore, the development of noninvasive and wearable sensors that can monitor cortisol concentration accurately is highly desirable for a smart health care solution. For example, the immunoassay method, which uses an antigen-antibody binding reaction, has been used extensively for electrochemical cortisol immunosensors using saliva and interstitial fluid, except tears (121419). However, these immunosensors still require the use of bulky impedance analyzers for the analysis of the Nyquist plot from electrochemical impedance spectroscopy. Although the cyclic voltammetry (CV) technique can be used as an alternative approach for sensing cortisol, additional bulky electrochemical instruments still are necessary for analyzing the CV curves (131419). Recently, wearable forms of cortisol sensors that use sweat were developed (15), but they still required bulky measurement equipment (1516). Therefore, portable and smart sensors that can monitor the accurate concentration of cortisol in real time are highly desirable for use in mobile health care.

Among the various body fluids, tears, in particular, contain important biomarkers, including cortisol (2021). Thus, the integration of biosensors with contact lenses is a potentially attractive candidate for the noninvasive and real-time monitoring of these biomarkers from tears (2225). However, an approach for fabricating a smart contact lens for sensing the cortisol in tears has not been demonstrated previously. Thus, here, we present an extraordinary approach for the formation of a smart, soft contact lens that enables remote, real-time monitoring of the cortisol level in the wearer’s tears using mobile phones. This smart, soft contact lens is composed of a cortisol sensor, a wireless antenna, capacitors, resistors, and integrated circuit chips that use stretchable interconnects without obstructing the wearer’s view. The components of this device (except the antenna) were protected from mechanical deformations by locating each of the components on discrete, rigid islands and by embedding these islands inside an elastic layer. A graphene field-effect transistor (FET; with the binding of monoclonal antibody) was used as this cortisol immunosensor, which exhibited a sufficiently low detection limit, i.e., 10 pg/ml, for its sensing of cortisol in human tears in which the cortisol concentration ranges from 1 to 40 ng/ml (26). This sensor was integrated with a near-field communication (NFC) chip and antenna inside the soft contact lens for the real-time wireless transmission of the data to the user’s mobile device (e.g., a smart phone or a smart watch). The antenna occupies a relatively large area of this soft lens, so it requires its high stretchability, good transparency, and low resistance for operating a standard NFC chip at 13.56 MHz. In our approach, the hybrid random networks of ultralong silver nanofibers (AgNFs) and fine silver nanowires (AgNWs) enabled high transparency and good stretchability of this antenna and its low sheet resistance for reliable standard NFCs (at 13.56 MHz) inside this smart contact lens. Thus, the fully integrated system of this smart contact lens provided wireless and battery-free operation for the simultaneous detection and transmission of the cortisol concentration from tears to a mobile phone using standard NFC. In addition, a human pilot trial and in vivo tests conducted using live rabbits demonstrated the biocompatibility of this lens, and its safety against inflammation and thermal/electromagnetic field radiation suggests its substantial usability as a noninvasive, mobile health care solution.

RESULTS

Cortisol immunosensor

A graphene FET sensor was fabricated by binding the cortisol monoclonal antibody (C-Mab) to the surface of graphene for the immunosensing of cortisol. Here, graphene acts as a transducer that converts the interaction between cortisol and C-Mab into electrical signals. Figure 1A shows the immobilization process of C-Mab to graphene. Immobilization proceeds through amide bonding of the C-Mab onto the carboxyl group of the graphene surface via the EDC [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride]/NHS (N-hydroxysulfosuccinimide) coupling reaction. A chemical vapor deposition–synthesized graphene layer was transferred onto a desired substrate and exposed to ultraviolet ozone (UVO) to activate the surface of the graphene with the carboxylate group. Figure S1 shows the contact angle between this surface of the graphene and a droplet of deionized (DI) water. Longer exposure time to UVO can decrease the hydrophobicity of graphene with decreasing the contact angle. Table S1 shows the increase in the electrical resistance of graphene that resulted from this UVO treatment. In our experiment, 2 min of exposure time to UVO decreased the contact angle from 70° to 38° without increasing the resistance of the graphene notably. UVO exposure times longer than this threshold time degraded the resistance of the graphene excessively, so the time of exposure of our samples to UVO was limited to 2 min. Figure S2A illustrates the process of immobilizing C-Mab through the EDC/NHS coupling reaction. This two-step coupling reaction of EDC and NHS can mediate the amide bonding between the carboxylate group of the UVO-exposed graphene and the amine group of the protein (12172728). Here, EDC forms reactive O-acylisourea ester, thereby making the surface unstable. This O-acylisourea ester reacts with the NHS to form amine-reactive NHS ester with the surface still remaining semistable. Then, C-Mab with the amine group reacts with the amine-reactive NHS ester, thereby forming stable amide bonding that can immobilize C-Mab to the NHS on the surface of the graphene. Figure S2B shows the Fourier transform infrared (FTIR) spectroscopy spectra of the DI water after the cortisol sensor had been immersed for 24 hours. The spectra of the DI water in which the sensor was immersed were not significantly different from those of the pristine DI water. However, the C-Mab solution that had a concentration of 1 μg/ml had a significant peak intensity in the range of 3000 to 2800 cm−1, representing the N-H bonding in the C-Mab. These results indicated that C-Mab formed stable bonding on the carboxylated graphene and was negligibly detached by exposure to water.

From https://advances.sciencemag.org/content/6/28/eabb2891

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