Saliva - a new opportunity for fluid biopsy.

Saliva is a complex biological fluid with a variety of biomolecules, such as DNA, RNA, proteins, metabolites and microbiota, which can be used for the screening and diagnosis of many diseases. In addition, saliva has the characteristics of simple collection, non-invasive and convenient storage, which gives it the potential to replace blood as a new main body of fluid biopsy, and it is an excellent biological diagnostic fluid. This review integrates recent studies and summarizes the research contents of salivaomics and the research progress of saliva in early diagnosis of oral and systemic diseases. This review aims to explore the value and prospect of saliva diagnosis in clinical application.

Diagnostic Accuracy of Liquid Biopsy for Oral Potentially Malignant Disorders and Head and Neck Cancer: an Overview of Systematic Reviews.

PURPOSE OF REVIEW: The aim of this overview is to appraise the evidence on salivary biomarkers for H&N cancer diagnosis. The acronym PICOS was used to develop the eligibility criteria and the focused review question: are liquid biopsies (saliva biomarkers) reliable for cancer detection in H&N cancer patients? Electronic database search encompassed PubMed, EMBASE, Scopus, Cochrane Library, Web of Science, and LILACS. Risk of Bias (RoB) was assessed through AMSTAR 2. RECENT FINDINGS: A total of 20 SRs were included. Only seven SRs were able to reach more solid conclusions around the retrieved findings by calculating the pooled sensitivity, specificity, and the overall area under the curve (AUC). Despite the limitations, significant RoB, and lack of test metrics in primary studies, all SRs recognize and encourage the potential role of saliva in the early diagnosis of oral cancer.

«Salivaomics¼ of Different Molecular Biological Subtypes of Breast Cancer.

The aim of the study was to determine the metabolic characteristics of saliva depending on the molecular biological subtype of breast cancer, as well as depending on the expression levels of HER2, estrogen receptors (ER), and progesterone receptors (PR). The study included 487 patients with morphologically verified breast cancer and 298 volunteers without breast pathologies. Saliva samples were obtained from all patients strictly before the start of treatment and the values of 42 biochemical indicators were determined. It has been established that the saliva of healthy volunteers and patients with various molecular biological subtypes of breast cancer differs in 12 biochemical indicators: concentrations of protein, urea, nitric oxide, malondialdehyde, total amino acid content, and activity of lactate dehydrogenase, alkaline phosphatase, gamma-glutamyltransferase, catalase, amylase, superoxide dismutase, and peroxidases. The saliva composition of patients with basal-like breast cancer differs from other subtypes in terms of the maximum number of indicators. Changes in biochemical indicators indicated an increase in the processes of lipid peroxidation and endogenous intoxication and a weakening of antioxidant protection, which correlates with the severity of the disease and the least favorable prognosis for this subtype of breast cancer. An analysis was made of the individual contribution of the expression level of HER2, estrogen, and progesterone receptors to changes in the biochemical composition of saliva. The HER2 (-)/HER2 (+) group, which should be considered as a single group, as well as ER-positive breast cancer, differ statistically significantly from the control group. For ER/PR-positive breast cancer, a more favorable ratio of saliva biochemical indicators was also noted compared to ER/PR-negative breast cancer.

Human Saliva Collection Devices for Proteomics: An Update.

There has been a rapid growth in the interest and adaptation of saliva as a diagnostic specimen over the last decade, and in the last few years in particular, there have been major developments involving the application of saliva as a clinically relevant specimen. Saliva provides a "window" into the oral and systemic health of an individual, and like other bodily fluids, saliva can be analyzed and studied to diagnose diseases. With the advent of new, more sensitive technologies to detect smaller concentrations of analytes in saliva relative to blood levels, there have been a number of critical developments in the field that we will describe. In particular, recent advances in standardized saliva collection devices that were not available three to four years ago, have made it easy for safe, simple, and non-invasive collection of samples to be carried out from patients. With the availability of these new technologies, we believe that in the next decade salivary proteomics will make it possible to predict and diagnose oral as well as systemic diseases, cancer, and infectious diseases, among others. The aim of this article is to review recent developments and advances in the area of saliva specimen collection devices and applications that will advance the field of proteomics.

Salivary Biomarkers in Breast Cancer: From Salivaomics to Salivaoncoomics.

Saliva is a promising biological fluid for the diagnosis and monitoring of diseases, including breast cancer. To study the composition of saliva, a complex of "omics" technologies is used: genomics, transcriptomics, proteomics, metabolomics and microbiomics. In this review, we systematized all known "omics" in their application to saliva analysis in breast cancer in order to understand how complete the picture is provided by the combination of different areas of research and to identify missing links. It has been shown that studies of saliva in breast cancer are chaotic and unsystematic. Inconsistency of sample sizes and high heterogeneity of breast cancer were identified. The main tasks that need to be solved for the complete and harmonious development of salivaomics in a new direction-"salivaonkoomics" are formulated. Thus, it is necessary to systematize and unify the study of biomarkers within each area of "omics", including sample size and its homogeneity, a list of methods and approaches, a list of biomarkers, reproducibility of results, and the ability to transfer results to other samples. It is important to expand the number of components of "omics" by adding new methods (for example, spectralomics, etc.), as well as studying the relationships between different "omics" technologies (interactomics). All this together will allow the study of saliva not only in breast cancer but also in many other pathologies to a qualitatively new level.

Salivaomics in head and neck cancer.

Salivaomics is a promising method for the early detection and monitoring of head and neck cancer (HNC). By analyzing salivary proteomics, RNA, and DNA, it identifies biomarkers that distinguish HNC patients from healthy individuals. Saliva's non-invasive, easily collectible nature and affordability make it an advantageous screening tool. Multiomics approaches, which explore genetic mutations, gene expression patterns, protein profiles, and metabolite levels, provide a comprehensive molecular perspective that enhances clinical applicability. The approaches enhance the precision of diagnoses, enable the development and application of targeted therapies, and contribute to the overall advancement of personalized medicine. Despite its potential, larger-scale studies are essential for validating biomarkers, and assessing sensitivity, accuracy, and specificity in detecting HNC. This review highlights salivaomics' potential as a non-invasive, accessible biological sample for early disease detection in HNC and underscores the value of multiomics in advancing this research. Salivaomics offers significant insights into the underlying mechanisms of HNC, enabling the discovery of robust, non-invasive biomarkers for improved disease management.

Saliva diagnostics: Salivaomics, saliva exosomics, and saliva liquid biopsy.

BACKGROUND: Each day, humans produce approximately 0.5 through 1.5 liters of saliva, a biofluid that is rich in biological omic constituents. Our lack of understanding how omic biomarkers migrate from diseased tissue to the saliva has impeded the clinical translation of saliva testing. Although such biomarkers must be conveyed via the vascular and lymphatic systems to the salivary glands, the molecular mechanisms that underlie this transport remain unclear. Although COVID-19 highlighted the need for rapid and reliable testing for infectious diseases, it represents only one of the many health conditions that potentially can be diagnosed using a saliva sample. TYPES OF STUDIES REVIEWED: The authors discuss salivaomics, saliva exosomics, and the mechanisms on which saliva diagnostics are based and introduce a novel electrochemical sensing technology that may be exploited for saliva liquid biopsy. RESULTS: The utility of saliva for screening for lung cancer is under investigation. Saliva testing may be used to stratify patients, monitor treatment response, and detect disease recurrence. The authors also highlight the landscapes of saliva-based SARS-CoV-2 testing and ultrashort cell-free DNA and outline how these fields are likely to evolve in the near future. PRACTICAL IMPLICATIONS: Breakthroughs in the study of saliva research, therefore, will facilitate clinical deployment of saliva-based testing.

Applications of Mass Spectrometry in Dentistry.

Mass Spectrometry (MS) is one of the fastest-developing methods in analytical instrumentation. As a highly sensitive, universal detector, it can identify known and unknown compounds, which can indeed be found in a minimal concentration. This review aims to highlight the significant milestones in MS applications in dentistry during recent decades. MS can be applied in three different fields of dentistry: (1) in research of dental materials and chemical agents, (2) in laboratory analysis of biospecimens, and (3) as a real-time diagnostic tool in service of oral surgery and pathology. MS applications on materials and agents may focus on numerous aspects, such as their clinical behavior, possible toxicity, or antimicrobial properties. MS is also a valuable, non-invasive tool for biomarkers' detection in saliva and has found great application in -omics technologies as it achieves efficient structure-finding in metabolites. As metabolites are located beyond the central dogma, this technique can provide a complete understanding of cellular functions. Thus, it is possible to determine the biological profile in normal and pathological conditions, detect various oral or systematic diseases and conditions, and predict their course. Lastly, some promising advances concerning the surgical approach to potentially oral malignant or malignant disorders exist. This breakthrough method provides a comprehensive approach to dental materials research and biomarker discovery in dental and craniofacial tissues. The current availability of various 'OMIC' approaches paves the way for individualized dentistry and provides suggestions for clinical applications in the point-of-care hubs.

Evaluation of Salivary Alkaline Phosphatase Levels in Passive Smokers of Different Age Groups.

Background The smoke inhaled by a nonsmoker from the smoldering end of a cigarette is referred to as passive smoke. The nicotine present in smoke is known to cause tissue damage and alter the enzymatic composition of the body. Alkaline phosphatase (ALP) is a group of intracellular hydrolytic enzymes known to partake in cellular metabolism. ALP levels are affected by smoking as well as passive smoking (PS) with a change in the pH of the oral cavity. The association of salivary alkaline phosphatase (S-ALP) levels in different age groups, gender, and times of exposure is not thoroughly explored yet, which was the primary aim of this study. Material and methods A total of 64 samples were collected from passive smokers and non-smokers. Unstimulated saliva (2-2.5 mL) was collected from each subject after obtaining their consent, followed by centrifuging and mixing with ALP reagent in a semi-autoanalyzer to obtain the S-ALP levels. Results Higher S-ALP levels were seen in passive smokers (34.70 IU/L) compared to healthy individuals (12 IU/L), which came to be statistically significant (p<0.01). S-ALP levels, when compared to different age groups and gender, were statistically insignificant (p>0.05). However, higher levels were seen in association with time of exposure in passive smokers where the data was statistically significant (p<0.01), suggesting tissue damage possibly due to oxidative stresses and tissue inflammation on continuous exposure for a minimum of 30-60 minutes daily as per our study. Conclusion Significantly high levels of S-ALP were found in passive smokers in comparison to non-smokers. This suggests that passive smoking has negative effects on the body tissues. Age, gender, and time of exposure of a non-smoker to tobacco smoke can lead to alterations in S-ALP levels. High levels of S-ALP were seen in individuals with prolonged exposure to tobacco smoke on a daily basis. Salivaomics can thus be used as a non-invasive, economical, and accurate alternative in tissue damage diagnosis.

Molecular screening of head neck cancer.

Liquid biopsy has become a significant tool in personalized medicine, enabling real-time monitoring of cancer evolution and patient follow-up. This minimally invasive procedure analyzes circulating tumor cells (CTCs) and circulating tumor-derived materials, such as ctDNA, miRNAs, and EVs. CTC analysis significantly impacts prognosis, detection of minimal residual disease (MRD), treatment selection, and monitoring of cancer patients. Liquid biopsy is an attractive option for mouth cancer detection and treatment progress monitoring in many countries. It is not invasive and requires no surgical expertise, making it an attractive option for mouth cancer detection. Liquid biopsy is a diagnostic repeatable test that can profile cancer genomes in real-time with minimal invasiveness and tailor oncological decision-making. It analyzes different blood-circulating biomarkers, with ctDNA being the preferred one. While tissue biopsy remains the gold standard for molecular evaluation of solid tumors, liquid biopsy is a complementary tool in various clinical settings, including treatment selection, monitoring response, cancer clonal evolution, prognostic evaluation, early disease detection, and minimal residual disease (MRD).

Saliva Diagnosis Using Small Extracellular Vesicles and Salivaomics.

Saliva is a complex oral biofluid composed of various biological molecules secreted by major and minor salivary glands, as well as by-products of host oral cells, oral bacteria, small extracellular vesicles (sEVs), and gingival crevicular fluid. Recently, salivary small extracellular vesicles and salivary multi-omics (microbiome, transcriptome, DNA methylome and proteome) are emerging as potential diagnostic tools for oral diseases, including the highly prevalent periodontitis. Here, we describe the methodologies for how to isolate salivary sEVs using the size exclusion chromatography method, and how to perform salivaomics, which may guide future dental research.

Saliva diagnostics: emerging techniques and biomarkers for salivaomics in cancer detection.

INTRODUCTION: The pursuit of easy-to-use, non-invasive and inexpensive diagnostics is an urgent task for clinicians and scientists. Saliva is an important component of body fluid with regular changes of contents under various pathophysiological conditions, and the biomarkers identified from saliva shows high application potentials and values in disease diagnostics. This review introduces the latest developments in saliva research, with an emphasis on the detection and application of salivary biomarkers in cancer detection. AREAS COVERED: Detection of disease-specific biomarkers in saliva samples by existing salivaomic methods can be used to diagnose various human pathological conditions and was introduced in details. This review also covers the saliva collection methods, the analytical techniques as well as the corresponding commercial products, with an aim to describe an holistic process for saliva-based diagnostics. EXPERT OPINION: Saliva, as a non-invasive and collectable body fluid, can reflect the pathophysiological changes of the human body to a certain extent. Identification of reliable saliva biomarkers can provide a convenient way for cancer detection in clinical applications.

The New Era of Salivaomics in Dentistry: Frontiers and Facts in the Early Diagnosis and Prevention of Oral Diseases and Cancer.

Nowadays, with the development of new and highly sensitive, blood is not the only medium of choice for the diagnosis of several diseases and pathological conditions. Saliva is now considered a safe and non-invasive sample to study oral and systemic diseases, showing great diagnostic potential. According to several recent studies, saliva has emerged as an emerging biofluid for the early diagnosis of several diseases, indicated as a mirror of oral and systemic health and a valuable source of clinically relevant information. Indeed, several studies have observed that saliva is useful for detecting and diagnosing malignant tumours, human immunodeficiency virus, heart disease, and autoimmune diseases. The growing realisation that saliva is an inexhaustible source of information has led to the coining of the term 'Salivaomics', which includes five "omics" in connection with the main constituents of saliva: genome and epigenome, transcriptomics, metabolomics, lipidomics, proteomics and microbiota. All those may be changed by disease state, so they offer significant advantages in the early diagnosis and prognosis of oral diseases. The aim of the present review isto update and highlight the new frontiers of salivaomics in diagnosing and managing oral disorders, such as periodontitis, premalignant disorders, and oral squamous cell carcinoma (OSCC).

Salivary biomarkers in cancer.

In recent years, the comprehensive analysis of saliva, i.e., salivaomics, has played an increasing role in biomarker discovery for disease detection in general and cancer specifically. Saliva is a readily accessible, non-invasive and low-cost specimen that can be used to detect biomarkers of clinical relevance. Saliva-based "omics" technologies, which include proteomics, transcriptomics, metabolomics and microbiomics, have rapidly evolved and may be applicable in point-of-care detection, liquid biopsy and nanoscience. Advances in analytical methods has increased the scope and application of salivaomics from solely the oral cavity to the entire physiologic system, and accordingly to personalized medicine. In this chapter, we highlight recent advances in analytical approaches to identify and detect biomarkers in saliva and their potential use as diagnostic, prognostic and therapeutic markers with a focus on cancer.

Saliva Diagnostics.

Cancer remains one of the leading causes of death, and early detection of this disease is crucial for increasing survival rates. Although cancer can be diagnosed following tissue biopsy, the biopsy procedure is invasive; liquid biopsy provides an alternative that is more comfortable for the patient. While blood, urine, and cerebral spinal fluid can all be used as a source of liquid biopsy, saliva is an ideal source of body fluid that is readily available and easily collected in the most noninvasive manner. Characterization of salivary constituents in the disease setting provides critical data for understanding pathophysiology and the evaluation of diagnostic potential. The aim of saliva diagnostics is therefore to develop a rapid and noninvasive detection of oral and systemic diseases that could be used together with compact analysis systems in the clinic to facilitate point-of-care diagnostics.

Salivaomics for Oral Cancer Detection: An Insight.

Early detection is very crucial for successful management of oral cancer or any disease as such. Oral squamous cell carcinoma (OSCC) accounts for nearly 90% of malignancy of oral cavity. In the field of cancer research, there is always an ongoing quest for newer methods to lower the morbidity and mortality associated with OSCC. Saliva, a readily available noninvasive biofluid with constant contact with oral cancer lesion, offers an appealing alternative to serum and tissue testing. This review throws light on incorporation of newer technologies for harnessing the saliva to its fullest potential with increased specificity and sensitivity toward identification of cancer-specific molecular signatures for the development of point-of-care applications that could be used at the clinical setting.

The Use of Saliva as a Biosample in the Light of COVID-19.

Saliva is easy to collect and a biofluid that is readily available without the need for special equipment for its collection. The collection process, which is non-invasive and inexpensive, leads to obtaining a biomaterial that can serve as a source of information for molecular diagnostics of diseases in general medicine, genetics and dentistry. Unfortunately, many of the salivary methodologies are lacking important parameters to provide for not only the safety of the operator, but also the quality and reproducibility of the research. Since the COVID-19 pandemic, salivary diagnostics demonstrate a great potential for research of SARS-CoV 2. In this review, good practice for unstimulated saliva collection and patient preparation was provided, based on the latest literature and available guidelines. Schemes for saliva collection procedures were presented following an extended literature search. Descriptions of salivary probes/cups, techniques of saliva collection, and the use of specific buffering solutions for the stability of collected samples for SARS-CoV-2 detection were also evaluated.

Salivary biomarkers for cancer diagnosis: a meta-analysis.

Background: Saliva represents a promising non-invasive source of novel biomarkers for diagnosis and prognosis cancer. This meta-analysis evaluates the diagnostic value of salivary biomarkers for detection of malignant non-oral tumours to better define the value of saliva as an alternative liquid biopsy.Materials and methods: We performed a systematic review and meta-analysis. PubMed, Embase, LILACS and the Cochrane Library were searched to identify articles that examined the potential of salivary biomarkers for the diagnosis of malignant non-oral tumours. To assess the overall accuracy, we calculated the diagnostic odds ratio (DOR), area under hierarchical summary receiver operating characteristic (AUC) curve, sensitivity, specificity, positive likelihood ratio (PLR) and negative likelihood ratio (NLR) using a random- or fixed-effects model. Heterogeneity and publication bias were assessed. Statistical tests were two-sided.Results: One hundred fifty-five study units from 29 articles with 11,153 subjects were included. The pooled sensitivity, specificity, PLR, NLR, DOR and AUC were 0.76 (95% confidence intervals (CI), 0.74-0.77), 0.76 (95% CI, 0.75-0.77), 3.22 (95% CI, 2.92-3.55), 0.31 (95% CI, 0.28-0.34), 13.42 (95% CI, 12.28-15.96) and 0.85 (95% CI, 0.84-0.87), respectively.Conclusion: Salivary biomarkers may be potentially used for non-invasive diagnosis of malignant non-oral tumours.Key messagesThis meta-analysis evaluates the diagnostic value of salivary biomarkers for detection of malignant non-oral tumours to better define the role of saliva as an alternative liquid biopsy.Salivary biomarkers showed 85% accuracy for cancer distant to the oral cavity.Saliva represents a promising non-invasive source of novel biomarkers in cancer.

Role of Saliva and Salivary Diagnostics in the Advancement of Oral Health.

The objective of this article was to provide an account of some of the developments related to saliva over the first 100 years of the Journal of Dental Research and to outline some of the many biomarkers identified in saliva in the last few years. The first section covers findings in salivary physiology, biochemistry, calcium phosphate chemistry related to saliva, microbiology, and the role of saliva in maintaining oral health. The second section highlights salivary diagnostics, salivaomics, and saliva exosomics in the context of the emerging theme of personalized and precision medicine.

Salivary Exosomes as Nanocarriers for Cancer Biomarker Delivery.

Human saliva is an ideal body fluid for developing non-invasive diagnostics. Saliva contains naturally-occurring nanoparticles with unique structural and biochemical characteristics. The salivary exosome, a nanoscale extracellular vesicle, has been identified as a highly informative nanovesicle with clinically-relevant information. Salivary exosomes have brought forth a pathway and mechanism by which cancer-derived biomarkers can be shuttled through the systemic circulation into the oral cavity. Despite such clinical potential, routine and reliable analyses of exosomes remain challenging due to their small sizes. Characterization of individual exosome nanostructures provides critical data for understanding their pathophysiological condition and diagnostic potential. In this review, we summarize a current array of discovered salivary biomarkers and nanostructural properties of salivary exosomes associated with specific cancers. In addition, we describe a novel electrochemical sensing technology, EFIRM (electric field-induced release and measurement), that advances saliva liquid biopsy, covering the current landscape of point-of-care saliva testing.