Relationship of flow rate, uric acid, peroxidase, and superoxide dismutase activity levels with complications in diabetic patients: can saliva be used to diagnose diabetes?

Label-Free Metal-Oxide Transistor Biosensors for Metabolite Detection in Human Saliva

Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non-invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ-TFT) sensor is developed for the label-free, rapid detection of uric acid (UA) and 25(OH)Vitamin-D3 (Vit-D3) in human saliva. The HJ-TFTs utilize a solution-processed In2O3/ZnO channel functionalized with uricase enzyme and Vit-D3 antibody for the selective detection of UA and Vit-D3, respectively. The ultra-thin tri-channel architecture facilitates strong coupling between the electrons transported along the buried In2O3/ZnO heterointerface and the electrostatic perturbations caused by the interactions between the surface-immobilized bioreceptors and target analytes. The biosensors can detect a wide range of concentrations of UA (from 500 nm to 1000 µM) and Vit-D3 (from 100 pM to 120 nm) in human saliva within 60 s. Moreover, the biosensors exhibit good linearity with the physiological concentration of metabolites and limit of detections of ≈152 nm for UA and ≈7 pM for Vit-D3 in real saliva. The specificity is demonstrated against various interfering species, including other metabolites and proteins found in saliva, further showcasing its capabilities.

Infrared spectroscopy for fast screening of diabetes and periodontitis

SIGNIFICANCE

FT-IR is an important and emerging tool, providing information related to the biochemical composition of biofluids. It is important to demonstrate that there is an efficacy in separating healthy and diseased groups, helping to establish FT-IR uses as fast screening tool.

AIM

Via saliva diagnosis evaluate the accuracy of FT-IR associate with machine learning model for classification among healthy (control group), diabetic (D) and periodontitis (P) patients and the association of both diseases (DP).

APPROACH

Eighty patients diagnosed with diabetes and periodontitis through conventional methods were recruited and allocated in one of the four groups. Saliva samples were collected from participants of each group (n = 20) and were processed using Bruker Alpha II spectrometer in a FT-IR spectral fingerprint region between 600 and-1800 cm-1, followed by data preprocessing and analysis using machine learning tools.

RESULTS

Various FTI-R peaks were detectable and attributed to specific vibrational modes, which were classified based on confusion matrices showed in paired groups. The highest true positive rates (TPR) appeared between groups C vs D (93.5 % ± 2.7 %), groups C vs. DP (89.2 % ± 4.1 %), and groups D and P (90.4 % ± 3.2 %). However, P vs DP presented higher TPR for DP (84.1 % ±3.1 %) while D vs. DP the highest rate for DP was 81.7 % ± 4.3 %. Analyzing all groups together, the TPR decreased.

CONCLUSION

The system used is portable and robust and can be widely used in clinical environments and hospitals as a new diagnostic technique. Studies in our groups are being conducted to solidify and expand data analysis methods with friendly language for healthcare professionals. It was possible to classify healthy patients in a range of 78-93 % of accuracy. Range over 80 % of accuracy between periodontitis and diabetes were observed. A general classification model with lower TPR instead of a pairwise classification would only have advantages in scenarios where no prior patient information is available regarding diabetes and periodontitis status.

Unlocking the Diagnostic Potential of Saliva: A Comprehensive Review of Infrared Spectroscopy and Its Applications in Salivary Analysis

Infrared (IR) spectroscopy is a noninvasive and rapid analytical technique that provides information on the chemical composition, structure, and conformation of biomolecules in saliva. This technique has been widely used to analyze salivary biomolecules, owing to its label-free advantages. Saliva contains a complex mixture of biomolecules including water, electrolytes, lipids, carbohydrates, proteins, and nucleic acids which are potential biomarkers for several diseases. IR spectroscopy has shown great promise for the diagnosis and monitoring of diseases such as dental caries, periodontitis, infectious diseases, cancer, diabetes mellitus, and chronic kidney disease, as well as for drug monitoring. Recent advancements in IR spectroscopy, such as Fourier-transform infrared (FTIR) spectroscopy and attenuated total reflectance (ATR) spectroscopy, have further enhanced its utility in salivary analysis. FTIR spectroscopy enables the collection of a complete IR spectrum of the sample, whereas ATR spectroscopy enables the analysis of samples in their native form, without the need for sample preparation. With the development of standardized protocols for sample collection and analysis and further advancements in IR spectroscopy, the potential for salivary diagnostics using IR spectroscopy is vast.

Novel Portable Sensing System with Integrated Multifunctionality for Accurate Detection of Salivary Uric Acid

Uric acid, as the terminal product of purine metabolism in the body, is an important marker of many diseases. Uric acid is abundant in saliva, offering the possibility of its non-invasive detection. However, it is sensitive to interference in saliva by a variety of factors. A reliable method of processing saliva is centrifugation (CF), but the cost and size of equipment limit its use in everyday life. In this study, a novel portable salivary-sensing system (PSSS) with integrated suction filtration (SF) and temperature insulation was proposed to obtain more accurate salivary uric acid levels through a simple procedure. The PSSS includes a saliva container, a high-sensitive uric acid sensor (UAS), an accompanying printed circuit board (PCB), and a mobile application. The responses produced by the UAS presents excellent linearity (4.6 μA/mM with R² = 0.9964), selectivity, reproducibility, and stability for the detection of low levels of uric acid. The difference in detection values between the UAS and the commercial sensor is only ~4%. The primary feature of the saliva container is the processing of saliva by SF instead of CF. Samples from CF and SF showed no significant differences regarding uric acid levels, and both exhibited approximately 50% deviation from the untreated samples, while the difference in uric acid levels between the samples after SF and after applying both treatments was ~10%. Besides, insulation of the saliva container can partially eliminate sources of error induced by the environment during uric acid level testing. The PSSS provides a novel strategy for the immediate detection of specific markers in saliva. We believe that the PSSS has promising potential for future application in the rapid saliva testing.

Salivary molecular spectroscopy: A sustainable, rapid and non-invasive monitoring tool for diabetes mellitus during insulin treatment

Monitoring of blood glucose is an invasive, painful and costly practice in diabetes. Consequently, the search for a more cost-effective (reagent-free), non-invasive and specific diabetes monitoring method is of great interest. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been used in diagnosis of several diseases, however, applications in the monitoring of diabetic treatment are just beginning to emerge. Here, we used ATR-FTIR spectroscopy to evaluate saliva of non-diabetic (ND), diabetic (D) and insulin-treated diabetic (D+I) rats to identify potential salivary biomarkers related to glucose monitoring. The spectrum of saliva of ND, D and D+I rats displayed several unique vibrational modes and from these, two vibrational modes were pre-validated as potential diagnostic biomarkers by ROC curve analysis with significant correlation with glycemia. Compared to the ND and D+I rats, classification of D rats was achieved with a sensitivity of 100%, and an average specificity of 93.33% and 100% using bands 1452 cm^-1 and 836 cm^-1, respectively. Moreover, 1452 cm^-1 and 836 cm^-1 spectral bands proved to be robust spectral biomarkers and highly correlated with glycemia (R² of 0.801 and 0.788, P < 0.01, respectively). Both PCA-LDA and HCA classifications achieved an accuracy of 95.2%. Spectral salivary biomarkers discovered using univariate and multivariate analysis may provide a novel robust alternative for diabetes monitoring using a non-invasive and green technology.

The validity, stability, and utility of measuring uric acid in saliva

AIM

Serum uric acid (UA) is associated with many health conditions, including kidney, cardiovascular, and metabolic disorders. We examined the validity and stability of salivary UA as a noninvasive measure of serum UA.

MATERIALS & METHODS

Using serum and salivary UA data from healthy adults (n = 99), we examined the UA serum-saliva correlation, and UA associations with adiponectin and C-reactive protein. Using longitudinal data from young adults (n = 182), we examined salivary UA stability.

RESULTS

We found robust positive serum-saliva correlations for UA. UA and adiponectin were inversely related in serum and saliva. Salivary UA was relatively stable; 62-66% of variance could be attributed to a latent trait-like component.

CONCLUSION

Salivary UA may be an important biomarker indexing health and disease risk.

Chemical analysis in saliva and the search for salivary biomarkers – a tutorial review

A review of the uses of saliva biomarkers, detection methods and requirements for new biomarkers.

Saliva Liquid Biopsy for Point-of-Care Applications

Saliva is a non-invasive biofluid, which is easy to collect, transport, and store. Because of its accessibility and connection to systemic diseases, saliva is one of the best candidates for the advancement of point-of-care medicine, where individuals are able to easily monitor their health status by using portable convenient tools such as smartphones. There are a variety of scenarios with which saliva can be used: studies have been conducted on using saliva to measure stress hormones, enzyme levels, developmental disease biomarkers, and even cancer mutations. If validated biomarkers were combined with high-quality detection tools, saliva would open up a new frontier in high-quality healthcare, allowing physicians and patients to work together for real-time health monitoring and high-impact personalized preventative medicine. One of the most exciting emerging frontiers of saliva is liquid biopsy, which is a non-invasive means to assess the presence and characteristics of cancer in a patient. This article will review current basic knowledge of biomarkers, review their relation to different diseases and conditions, and explore liquid biopsy for point-of-care applications.

Antioxidant capacity of human saliva and periodontal screening assessment in healthy adults

OBJECTIVE

Saliva plays a pivotal role as an antioxidant system, and saliva antioxidant levels are reduced in patients with periodontal disease. Recently, a biochemical test able to determine saliva antioxidant levels was proposed as predictive for oral cavity diseases, but it was not clinically tested. In this preliminary study, we evaluated the relationships between Periodontal Screening and Recordings characteristics of patients and saliva antioxidant levels measures.

DESIGN

Thirty-nine patients (12 men, 27 women; mean age, 46 years, SD 17) attending the dental hygiene unit of a Private Clinic underwent a Periodontal Screening and Recordings examination and a saliva antioxidant levels measurement using a biochemical commercial test. The results of the clinical periodontal examination were compared to those obtained by the saliva test.

RESULTS

Approximately 70% of patients showed a low saliva antioxidant levels value, while the other patients had Optimal/Normal values. Thirteen patients (33%) resulted positive to Periodontal Screening and Recordings test. Using Periodontal Screening and Recordings values as gold standard, the saliva antioxidant levels test correctly classified 52.6% of patients; sensitivity was 84.6%, specificity was 36%.

CONCLUSIONS

The saliva antioxidant levels test had a good sensitivity when compared to the gold standard; this finding corroborates the hypothesis that alterations of the oral antioxidant levels are related to periodontal disease. The reduced specificity shows that saliva antioxidant levels test could detect alterations predisposing to periodontal disease before clinically evident aspects.

Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics

This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications.

Is human saliva an indicator of the adverse health effects of using mobile phones?

Increasing use of mobile phones creates growing concerns regarding harmful effects of radiofrequency nonionizing electromagnetic radiation on human tissues located close to the ear, where phones are commonly held for long periods of time. We studied 20 subjects in the mobile-phone group who had a mean duration of mobile phone use of 12.5 years (range 8-15) and a mean time use of 29.6 h per month (range 8-100). Deaf individuals served as controls. We compared salivary outcomes (secretion, oxidative damage indices, flow rate, and composition) between mobile phone users and nonusers. We report a significant increase in all salivary oxidative stress indices studied in mobile phone users. Salivary flow, total protein, albumin, and amylase activity were decreased in mobile phone users. These observations lead to the hypothesis that the use of mobile phones may cause oxidative stress and modify salivary function.

Diabetes-related molecular signatures in infrared spectra of human saliva

BACKGROUND

There is an ongoing need for improvements in non-invasive, point-of-care tools for the diagnosis and prognosis of diabetes mellitus. Ideally, such technologies would allow for community screening.

METHODS

In this study, we employed infrared spectroscopy as a novel diagnostic tool in the prediction of diabetic status by analyzing the molecular and sub-molecular spectral signatures of saliva collected from subjects with diabetes (n = 39) and healthy controls (n = 22).

RESULTS

Spectral analysis revealed differences in several major metabolic components - lipid, proteins, glucose, thiocyanate and carboxylate - that clearly demarcate healthy and diseased saliva. The overall accuracy for the diagnosis of diabetes based on infrared spectroscopy was 100% on the training set and 88.2% on the validation set. Therefore, we have established that infrared spectroscopy can be used to generate complex biochemical profiles in saliva and identify several potential diabetes-associated spectral features.

CONCLUSIONS

Infrared spectroscopy may represent an appropriate tool with which to identify novel diseases mechanisms, risk factors for diabetic complications and markers of therapeutic efficacy. Further study into the potential utility of infrared spectroscopy as diagnostic and prognostic tool for diabetes is warranted.

Salivary antioxidants in patients with type 1 or 2 diabetes and inflammatory periodontal disease: a case-control study

BACKGROUND

The purpose of this study was to evaluate and compare salivary concentrations of reduced, oxidized glutathione, uric acid, ascorbic acid, and total antioxidant capacity in subjects with diabetes and systemically healthy subjects with inflammatory periodontal disease.

METHODS

Sixteen patients with type 1 diabetes mellitus (DM), 25 patients with type 2 DM, and 24 systemically healthy patients, all with inflammatory periodontal disease, were recruited. Whole-saliva samples were obtained, and full-mouth clinical periodontal measurements, including plaque index, probing depth, gingival recession, clinical attachment level, and bleeding on probing, were recorded at six sites per tooth. Saliva flow rate and salivary levels of reduced and oxidized glutathione, vitamin C, uric acid, and total antioxidant capacity were determined. Data were analyzed statistically by non-parametric tests.

RESULTS

The subjects with type 2 DM had fewer teeth and more sites with probing depths >4 mm than the patients with type 1 DM (both P <0.01). The mean salivary reduced-glutathione concentration was lower in patients with type 1 DM than in the other two groups (both P <0.05). No significant differences in the salivary concentrations of the other antioxidants measured were found among the groups (P >0.05). Oxidized glutathione levels in the patients with type 1 DM were significantly lower than in the systemically healthy group (P = 0.007). In both groups with diabetes, salivary reduced-glutathione levels correlated positively with probing depth, and total antioxidant capacity correlated with salivary flow rate (P <0.01).

CONCLUSION

The decrease in salivary reduced-glutathione levels in patients with type 1 DM may have a role in periodontal tissue destruction by predisposing tissues to oxidative stress.

Serum and salivary oxidative analysis in Complex Regional Pain Syndrome

Although both inflammatory and neural mechanisms have been suggested as potential contributors to Complex Regional Pain Syndrome type I (CRPS-I), the pathogenesis of the syndrome is still unclear. Clinical trials have shown that free radical scavengers can reduce signs and symptoms of CRPS-I, indirectly suggesting that free radicals and increased oxidative stress are involved in the pathogenesis of CRPS-I. This study investigated this premise by determining the levels of antioxidants in the serum and saliva of 31 patients with CRPS-I and in a control group of 21 healthy volunteers. Serum lipid peroxidation products (MDA) and all antioxidative parameters analyzed were significantly elevated in CRPS-I patients: median salivary peroxidase and superoxide dismutase (SOD) activity values, uric acid (UA) concentration and total antioxidant status (TAS) values were higher in CRPS-I patients by 150% (p=0.01), 280% (p=0.04), 60% (p=0.0001), and 200% (p=0.0003), respectively, as compared with controls. Similar although not as extensive pattern of oxidative changes were found in the serum: mean serum UA and MDA concentrations and TAS value in the CRPS-I patients were higher by 16% (p=0.04), 25% (p=0.02), and 22% (p=0.05), respectively, than in the controls. Additionally, median salivary albumin concentration and median salivary LDH activities in the patients were 2.5 times (p=0.001) and 3.1 (p=0.004) times higher than in the controls. The accumulated data show that free radicals are involved in the pathophysiology of CRPS-I, which is reflected both in serum and salivary analyses. These data could be used for both diagnostic and therapeutic purposes in CRPS-I patients.

Diurnal variations in salivary protein carbonyl levels in normal and cognitively impaired human subjects

Oxidative stress has been documented in tissues and biofluids of subjects with sporadic Alzheimer disease (AD) and mild cognitive impairment (MCI). The aim of this study was to determine whether (a) salivary protein carbonyls are elevated in AD and MCI subjects, (b) salivary protein carbonyl contents in these groups exhibit diurnal variation, and (c) apolipoprotein E epsilon 4 (apoE epsilon 4) carrier status impacts salivary carbonyl concentrations or rhythmicity in the AD and MCI cohorts. Unstimulated saliva was collected at fixed intervals between 8 AM: and 10 PM: from 15 AD subject , 21 MCI subjects, and 30 cognitively-intact controls. Salivary protein carbonyl concentrations were measured by ELISA. ApoE genotyping was performed on the AD and MCI individuals. For all groups, mean protein carbonyl contents were significantly elevated at 2 PM: relative to other time points surveyed. Mean salivary protein carbonyl concentrations did not differ among the diagnostic groups. ApoE epsilon 4 carriers exhibited less temporal variation in salivary protein carbonyls relative to noncarriers. Thus, protein carbonyl content exhibits diurnal variation in adult human saliva. ApoE epsilon 4 carrier status may impact oropharyngeal disease expression by attenuating the inherent diurnal variability in salivary redox homeostasis. Salivary protein carbonyls do not differentiate AD and MCI from normal individuals. In conclusion, oxidative stress has been documented in tissues and biofluids of subjects with sporadic AD and MCI. This article demonstrates that levels of protein carbonyls, a marker of oxidative stress, exhibit robust diurnal variation in the saliva of normal elderly, MCI, and AD subjects. Apolipoprotein E epsilon 4 allele carrier status may attenuate this temporal variability in salivary redox homeostasis and thereby impact the natural history of oropharyngeal diseases.

Evidence-based roads to the promotion of health in old age

The increase in life expectancy, along with the accompanying ongoing increase in the proportion and absolute numbers of nonagenarians and centenarians have set forth the curiosity regarding the question of the quality of health in very old age. Studies on that issue have pointed to the fact that the very old people are actually healthier than originally predicted on the basis of the earlier studies on aging. Current efforts are thus invested in elucidating the possible basis of health in the very old people, as well as better understanding of potential causes of frailty and common diseases in old age. This review recounts on the various aspects underlying evidence-based recommendations for healthy life in old age. We focus on the genetic and non-genetic bases of aging and longevity, and the various directions towards the promotion of health, both via avoiding, or eliminating risk factors and deleterious effects, as well as conducting healthy lifestyle - in terms of proper nutrition and physical exercise. Next, we touch upon preventive medicine, particularly as related to vaccination, with a note also on the need for a reasonable use of medications. In addition, we report about the developing area of regenerative medicine and its potential in relation to the prevention of damage and possible strategies towards tissue repair in cases of age-related degenerative processes.

Salivary analysis and antioxidants in cleft lip and palate children

OBJECTIVE

To investigate the sialometry, sialochemistry and antioxidants in cleft patients prior to alveolar closure procedures.

DESIGN

Saliva was collected from 21 children with unilateral and bilateral cleft lip and palate (UCLP and BCLP) with overt oronasal alveolar communication and with recurrent licking of fluids and soft diet complaints (the study group) and in 22 normal individuals (the control group). Salivary flow rate was measured, and calcium (Ca), phosphate (P), magnesium (Mg), total protein, albumin, amylase, lactate dehydrogenase (LDH), and secretory IgA were analysed. Salivary total antioxidant status (TAS), peroxidase activity, superoxide dismutase (SOD) activity, uric acid (UA), was also determined.

RESULTS

The sialometry and sialochemistry analyses did not reveal significant difference between the two groups. Salivary median uric acid concentration was 6-fold lower in the cleft group (p<0.05). The median total antioxidant status (TAS) of the cleft group however, was significantly higher by 58% (p<0.005) than that of the control group. Median SOD activity was also higher in the cleft group, by 42%, though these differences did not reach statistical significance.

CONCLUSIONS

Our findings suggest that the oral biology system of cleft patients in their prealveolar closure stage does not differ significantly from normal controls. Low UA found in the saliva of cleft patients may suggest that some genetic alteration of the UA transport occurs simultaneously when cleft lip and palate occur. TAS reduction may also reveal an increased oxidative stress burden in the oral cavities of cleft children which has never been shown before.