Human Tears Research Articles

Non-targeted Metabolomics Analysis Reveals Distinct Metabolic Profiles Between Positive and Negative Emotional Tears of Humans: A Preliminary Study.

Background Basal, reflex, and emotional tears differ in chemical components. It is not yet known whether chemical differences exist in tears of different emotions. We investigated the biochemical basis of emotional tears by performing non-targeted metabolomics analyses of positive and negative emotional tears of humans. Methods Samples of reflex, negative, and positive emotional tears were obtained from 12 healthy college participants (11 females and one male). Untargeted metabolomics was performed to identify metabolites in different types of tears. The differentially altered metabolites were screened and assessed using univariate and multivariate analyses. Results The orthogonal partial least squares discriminant analysis model showed that reflex, negative, and positive emotional tears were clearly separated. A total of 133 significantly differentially expressed metabolites of electrospray ionization source (ESI-) mode were identified between negative and positive emotional tears. The top 50 differentially expressed metabolites between negative and positive emotional tears were highly correlated. Pathway analysis revealed that secretion of negative emotional tears was associated with some synapses in the brain, regulation of a series of endocrine hormones, including the estrogen signaling pathway, and inflammation activities, while secretion of positive emotional tears was correlated with biotin and caffeine metabolism. Conclusions It is indicated that metabolic profiles of reflex, positive, and negative emotional tears of humans are distinct, and secretion of the tears involves distinct biological activities. Therefore, we present a chemical method for detecting human emotions, which may become a powerful tool for the diagnosis of mental diseases and the identification of fake tears.

Effects on the Human Tear Film of Applying Skin Lipids to the Ocular Surface.

The effect of skin lipids on the formation and stability of the human tear film was investigated. Skin swab substances (SSSs) were applied to the eyes of volunteers and studied using fluorescein or with TearView, which records infrared emissivity showing tear film integrity in real time. Results were compared with similar experiments using castor oil, freshly collected meibum, or acetic acid, which simulated the low pH of the skin. Fluorescein and TearView results were comparable. TearView showed the natural unaltered tear film over the whole eye, instant changes to the tear film, and meibomian gland activity. Minimal amounts of SSS destroyed the integrity of the film and caused pain. Corneal epithelial damage could be detected. TearView showed that SSS stimulated meibomian gland secretion if applied directly to the posterior eyelid margin. Excess meibum had no effect on the tear film spread or integrity. Castor oil formed floating lenses on the tear film which were spread by a blink but then condensed back toward themselves. There was no pain or surface damage with these oils. SSS contamination of the ocular surface disrupts the tear film, causes stinging, and fluorescein staining of the corneal epithelial cells after a blink. SSS stimulates meibomian gland activity. It is possible that various ocular conditions associated with dry eye, such as blepharitis and ocular rosacea, may compromise a meibomian lipid barrier of the eye lid margin. Skin lipids would then have access to the ocular surface and cause dry eye symptoms.

Untargeted analysis and tentative identification of unknown substances in human tears by ultra-high performance liquid chromatography-high resolution mass spectrometry: Pilot study

In this work, a new approach for the identification of unknown compounds in human tears has been developed and validated using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) linked to an intelligent data acquisition mode (AcquireX DS-dd-MS2) coupled to an automated data processing software (Compound Discoverer™ 3.2). As a pilot research study, four human tear samples from volunteers were analyzed. Data were acquired in both positive and negative ionization modes and exact mass, isotope pattern, and MS2 spectra match were used for the tentative identification. Following this approach, 58 substances were identified, 47 in positive mode and 11 in negative mode, with an estimated concentration ranging from 0.1 to 9000 ng mL−1. Most of them were amino acids, hormones, metabolites, and pharmaceuticals. In order to validate the proposed method, the system suitability was evaluated and 29 commercial analytical standards of the tentatively identified substances were analyzed, of which 28 were confirmed obtaining a high identification accuracy (96.6 %). These results confirm that the screening tool presented in this work can facilitate the discovery of new metabolites, novel potential biomarkers, and substances to which the person is exposed, such as pollutants.

A Validatable Droplet Digital Polymerase Chain Reaction Assay for the Detection of Adeno-Associated Viral Vectors in Bioshedding Studies of Tears.

The use of viral vectors to treat genetic diseases has increased substantially in recent years, with over 2,000 studies registered to date. Adeno-associated viral (AAV) vectors have found particular success in the treatment of eye related diseases, as exemplified by the approval of voretigene neparvovec-rzyl. To bring new therapies to market, regulatory agencies typically request qualified or validated bioshedding studies to evaluate release of the vector into the environment. However, no official guidelines for the development of molecular based assays to support such shedding studies have been released by the United States Food and Drug Administration, leaving developers to determine best practices for themselves. The purpose of this protocol is to present a validatable protocol for the detection of AAV vectors in human tears by droplet digital polymerase chain reaction (ddPCR) in support of clinical bioshedding studies. This manuscript discusses current industry approaches to molecular assay validation and demonstrates that the method exceeds the target assay acceptance criteria currently proposed in white papers. Finally, steps critical in the performance of any ddPCR assay, regardless of application, are discussed.

Shedding light on the viscoelastic behavior of artificial and human tears: A microrheological approach

This study conducts research on the viscoelastic properties of biological fluids, including both hyaluronic acid-containing lubricating eye drops and human tears, by means of passive microrheology. By tracking the Brownian motion of tracer particles of various sizes in the fluids, we were able to probe their viscoelastic properties. The results showed that the viscoelastic properties of artificial tears, such as Newtonian viscosity and relaxation time, scale to the concentration and macromolecular size of hyaluronic acid, resembling unentangled semidiluted solutions. Moreover, human tears were found to have a viscosity that is 50% greater than that of pure water, comparable to artificial tears containing 0.1% hyaluronic acid, but with a relaxation time one order of magnitude longer than ophthalmic solutions. This behavior was attributed to their intricate composition. The distinctive aspect of this study lies in demonstrating the feasibility of measuring the rheological properties of human tears, a biofluid of great interest, using extremely small sample volumes and microrheology, providing comprehensive information across a wide range of frequencies approaching those corresponding to blinking upon the application of the Cox–Merz rule. These findings are of significant value as they pave the way for future research on small volumes of tears from ophthalmic patients.

Preliminary proteomic analysis of human tears in lacrimal adenoid cystic carcinoma and pleomorphic adenoma.

To detect proteomic differences in tears between adenoid cystic carcinoma (ACC) and pleomorphic adenoma (PA). Tear samples were collected from 4 patients with ACC, 5 with PA, and 4 control cases. Label-free analysis and parallel reaction monitoring (PRM) were used to screen and validate the tear proteome. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) were conducted for bioinformatics analysis. In total, 1059 proteins in tear samples were identified by label-free analysis. Between ACC and PA, 415 differentially expressed proteins were detected. Based on the GO annotation, enzyme regulator activity and serine-type endopeptidase inhibitor activity in the molecular function category, blood microparticle and extracellular matrix in the cellular component category, and response to nutrient levels in the biological process category were most predominant. By KEGG pathway annotation, the different proteins between ACC and PA mainly participated in complement and coagulation cascades, amoebiasis, African trypanosomiasis and cholesterol metabolism. Eight proteins with mostly significant differences were verified by PRM, and five proteins with more than 10-fold increases in ACC compared with PA, including integrin β, α-2-macroglobulin, epididymal secretory sperm binding protein Li 78p, RAB5C, and complement C5, were identified. The combined tools of label-free analysis and PRM are very effective and efficient, especially for samples such as tears. Some proteomic differences in tears between ACC and PA are identified and these protein candidates may be specific biomarkers for future exploration.

Robots with tears can convey enhanced sadness and elicit support intentions.

The behaviour of shedding tears is a unique human expression of emotion. Human tears have an emotional signalling function that conveys sadness and a social signalling function that elicits support intention from others. The present study aimed to clarify whether the tears of robots have the same emotional and social signalling functions as human tears, using methods employed in previous studies conducted on human tears. Tear processing was applied to robot pictures to create pictures with and without tears, which were used as visual stimuli. In Study 1, the participants viewed pictures of robots with and without tears and rated the intensity of the emotion experienced by the robot in the picture. The results showed that adding tears to a robot's picture significantly increased the rated intensity of sadness. Study 2 measured support intentions towards a robot by presenting a robot's picture with a scenario. The results showed that adding tears to the robot's picture also increased the support intentions indicating that robot tears have emotional and social signalling functions similar to those of human tears.

Extensional flow of a free film of nematic liquid crystal with moderate elasticity

The human tear film is a multilayer structure in which the dynamics are often strongly affected by a floating lipid layer. That layer has liquid crystalline characteristics and plays important roles in the health of the tear film. Previous models have treated the lipid layer as a Newtonian fluid in extensional flow. Motivated to develop a more realistic treatment, we present a model for the extensional flow of thin sheets of nematic liquid crystal. The rod-like molecules of these substances impart an elastic contribution to the rheology. We rescale a weakly elastic model due to Cummings et al. [“Extensional flow of nematic liquid crystal with an applied electric field,” Eur. J. Appl. Math. 25, 397–423 (2014).] to describe a lipid layer of moderate elasticity. The resulting system of two nonlinear partial differential equations for sheet thickness and axial velocity is fourth order in space, but still represents a significant reduction of the full system. We analyze solutions arising from several different boundary conditions, motivated by the underlying application, with particular focus on dynamics and underlying mechanisms under stretching. We solve the system numerically, via collocation with either finite difference or Chebyshev spectral discretization in space, together with implicit time stepping. At early times, depending on the initial film shape, pressure either aids or opposes extensional flow, which changes the free surface dynamics of the sheet and can lead to patterns reminiscent of those observed in tear films. We contrast this finding with the cases of weak elasticity and Newtonian flow, where the sheet retains the same qualitative shape throughout time.

Establishing an immunological profile of 96 cytokines, chemokines, and growth factors in human biofluids via MILLIPLEX® multiplex immunoassay

Abstract Multiplex immunoassays are well-established research tools enabling the simultaneous measurement of several proteins in biological samples. In the field of immunology, these immunoassay kits have been critically important for profiling the expression of a wide array of immunomodulatory proteins, including cytokines, chemokines, and growth factors. To this end, we recently developed two MILLIPLEX® multiplex immunoassay kits, each capable of the simultaneous measurement of 48 unique proteins in human samples. In this study, our objective was to profile the relative abundance of 96 cytokines, chemokines, and growth factors in a diverse collection of human biofluids, including serum, plasma, cerebrospinal fluid, saliva, sputum, urine, tears, milk, synovial fluid, and bronchoalveolar lavage (BAL). For each analyte, the fold increase in the average sample measurement relative to the limit of detection was determined. Some biofluids were generally rich in these immunological factors, such as BAL samples, whereas others were sparse, as noted in milk samples. Additionally, the reagent compatibility of the two immunoassay kits used to interrogate the sample cohort was examined to define opportunities for developing novel custom multiplex immunoassays containing analytes from each of the parent kits. The result of this effort was the generation of a set of rules guiding the acceptable combinations amongst the 96 proteins as well as the identification of mutually exclusive protein targets.

A Pilot Study of a Panel of Ocular Inflammation Biomarkers in Patients with Primary Sjögren’s Syndrome

Ocular diseases have a strong impact on individuals, the effects of which extend from milder visual impairment to blindness. Due to this and to their prevalence, these conditions constitute important health, social and economic challenges. Thus, improvements in their early detection and diagnosis will help dampen the impact of these conditions, both on patients and on healthcare systems alike. In this sense, identifying tear biomarkers could establish better non-invasive approaches to diagnose these diseases and to monitor responses to therapy. With this in mind, we developed a solid phase capture assay, based on antibody microarrays, to quantify S100A6, MMP-9 and CST4 in human tear samples, and we used these arrays to study tear samples from healthy controls and patients with Sjögren's Syndrome, at times concomitant with rheumatoid arthritis. Our results point out that the detection of S100A6 in tear samples seems to be positively correlated to rheumatoid arthritis, consistent with the systemic nature of this autoinflammatory pathology. Thus, we provide evidence that antibody microarrays may potentially help diagnose certain pathologies, possibly paving the way for significant improvements in the future care of these patients.

Human tear metabolites associated with nucleoside-signalling pathways in bacterial keratitis

ObjectiveThe study aimed to profile and quantify tear metabolites associated with bacterial keratitis using both untargeted and targeted metabolomic platforms. MethodsUntargeted metabolomic analysis using liquid-chromatography-Q Exactive-HF mass-spectrometry explored tear metabolites significantly associated with bacterial keratitis (n = 6) compared to healthy participants (n = 6). Differential statistics and principal component analysis determined meaningful metabolite differences between cases and controls. Purines and nucleosides were further quantified and compared between 15 cases and 15 controls in the targeted metabolomic platform using TSQ quantum access triple quadrupole mass spectrometry. Compound quantification was done by plotting the calibration curves and the difference in the compound levels was evaluated using the Wilcoxon rank-sum test. ResultsIn the untargeted analysis, 49 tear metabolites (27 upregulated and 22 downregulated) were differentially expressed between cases and controls. The untargeted analysis indicated that the purine metabolism pathway was the most affected by bacterial keratitis. Metabolite quantification in the targeted analysis further confirmed the upregulation of xanthine (P = 0.02) and downregulation of adenine (P < 0.0001), adenosine (P < 0.0001) and cytidine (P < 0.0001) in the tears of participants with bacterial keratitis compared to that of healthy participants. ConclusionsBacterial keratitis significantly changes the tear metabolite profile, including five major compound classes such as indoles, amino acids, nucleosides, carbohydrates, and steroids. This study also indicates that tear fluids can be used to map the metabolic pathways and uncover metabolic markers associated with bacterial keratitis. Conceivably, the inhibition of nucleoside synthesis may contribute to the pathophysiology of bacterial keratitis because nucleosides are required for maintaining cellular energy homeostasis and immune adaptability.

Experimental design considerations for studies of human tear proteins

PurposeHuman tears contain abundant, diverse sets of proteins that may serve as biomarkers of ocular surface health. There is a need for reproducible methods that consider multiple factors influencing the tear proteome, in addition to the variable of interest. Here we examined a workflow for proteomic analysis of tear proteins without the need to pool tear samples from multiple individuals, thus allowing for analyses based on individual factors, and increasing opportunities for protein biomarker discovery. MethodsTears were collected by Schirmer strip following topical ocular anesthetic application then individually stored at −80 °C prior to processing for proteomics. Tear proteins were extracted from Schirmer strips, digested using suspension trapping spin columns (S-Trap), and labeled with high multiplicity tandem mass tags (TMT). Peptide digests were then extensively fractionated by two-dimensional chromatography and analyzed by mass spectrometry to identify and measure changes in protein abundance in each sample. Analysis of select samples was performed to test protocols and to compare the impact of clinically relevant parameters. To facilitate comparison of separate TMT experiments, common pool samples were included in each TMT instrument run and internal reference scaling (IRS) was performed. ResultsDifferences in subsets of tear proteins were noted for: geographic site of tear collection, contact lens use, and differences in tear fluid volume among individuals. ConclusionThese findings demonstrate that proteomic analysis of human tear proteins can be performed without the need to pool samples, and that development of analytic workflows must consider factors that may affect outcomes in studies focused on diverse clinical samples.

Effect of monovalent electrolyte solutions on the human tear ferning pattern.

To investigate the effect of the addition of a low concentration of sodium chloride (NaCl) and potassium chloride (KCl) solutions on the tear ferning (TF) patterns of tears collected from humans. A tear sample (20 μL) was collected from the right eye of 23 males and 7 females (25.4 ± 6.6 years). The tears were collected in one sitting for healthy subjects (N = 13). For dry eye participants (N = 17), the tear samples were collected in two separate settings with five minutes gap in between. A sample (1 μL) from each tear was dried on a glass slide, and the obtained ferns were observed using a microscope and graded using the five-point TF grading scale. Mixtures of tear samples (0.5 μL) and different volumes (0.5-2.5 μL) of each electrolyte (10-30 mg in 100 mL of water) solution were prepared, and their TF patterns were recorded and compared with those of the corresponding pure tears. Significant improvements (Wilcoxon test, P < 0.001) have been seen in the TF grades of the tear samples after the addition of NaCl and KCl solutions. A significant difference (Wilcoxon test, P = 0.016) was found between the TF grades when NaCl and KCl solutions were added to the tear samples. The TF grades of pure tears collected from dry-eye subjects ranged from 2.1 to 3.5, based on the five points grading scale, and decreased to be in the range of 0.4 to 1.6 after the addition of electrolyte solutions. While the TF grades of pure tears collected from normal-eye ranged from 1.2 to 1.9 and improved after the addition of electrolyte solution to be in the range of 0.4 to 1.5. The TF test was used in vitro to assess the impact of the addition of a low concentration of sodium and potassium chloride solutions on tears collected from humans. The TF grades of human tears significantly improved after the addition of either sodium or potassium chloride solution. The mechanism for the improvement in TF grades due to the addition of electrolyte solutions must be investigated.

A combined experimental-computational approach to study interactions of topical ophthalmologic drugs with a tear film model.

Many topical ophthalmologic drug formulations are based on micellar drug delivery. Recently, a state-of-the-art delivery approach was suggested utilizing complex oil-in-water nanoemulsions loaded with active drug molecules. We study drug nanocarriers consisting of nanodroplets of nonpolar lipids with varying chain lengths coated with cationic surfactants. We employ both experimental and computational approaches. In experiments, we use a unique in vitro system that models human tear film. It mimics eye-blinking with tear inflow and evaporation. The device also allows control of the blinking rate and uses fluorescein staining to visualize the tear film model upon administration of topical ophthalmologic drugs. In the computational approach,

Lectin-Based Affinity Enrichment and Characterization of N-Glycoproteins from Human Tear Film by Mass Spectrometry.

The glycosylation of proteins is one of the most common post-translational modifications (PTMs) and plays important regulatory functions in diverse biological processes such as protein stability or cell signaling. Accordingly, glycoproteins are also a consistent part of the human tear film proteome, maintaining the proper function of the ocular surface and forming the first defense barrier of the ocular immune system. Irregularities in the glycoproteomic composition of tear film might promote the development of chronic eye diseases, indicating glycoproteins as a valuable source for biomarker discovery or drug target identification. Therefore, the present study aimed to develop a lectin-based affinity method for the enrichment and concentration of tear glycoproteins/glycopeptides and to characterize their specific N-glycosylation sites by high-resolution mass spectrometry (MS). For method development and evaluation, we first accumulated native glycoproteins from human tear sample pools and assessed the enrichment efficiency of different lectin column systems by 1D gel electrophoresis and specific protein stainings (Coomassie and glycoproteins). The best-performing multi-lectin column system (comprising the four lectins ConA, JAC, WGA, and UEA I, termed 4L) was applied to glycopeptide enrichment from human tear sample digests, followed by MS-based detection and localization of their specific N-glycosylation sites. As the main result, our study identified a total of 26 N glycosylation sites of 11 N-glycoproteins in the tear sample pools of healthy individuals (n = 3 biological sample pools). Amongst others, we identified tear film proteins lactotransferrin (N497 and N642, LTF), Ig heavy chain constant α-1 (N144 and 340, IGHA1), prolactin-inducible protein (N105, PIP), and extracellular lacritin (N105, LACRT) as highly reliable and significant N glycoproteins, already associated with the pathogenesis of various chronic eye diseases such as dry eye syndrome (DES). In conclusion, the results of the present study will serve as an important tear film N-glycoprotein catalog for future studies focusing on human tear film and ocular surface-related inflammatory diseases.

Flexible electrochemical sensor with Fe/Co bimetallic oxides for sensitive analysis of glucose in human tears

The construction of uniformly dispersed structure with abundant active sites is crucial for fast electron transport and advancing electrocatalytic reactions. Herein, FexCoyO4-rGO was prepared by depositing Fe and Co bimetallic oxides in-situ on reduced graphene oxide through a simple process combined hydrothermal reaction and calcination. Fe was elaborately introduced into the synthesis of metal oxides to alleviate the aggregation of cobalt oxides and obtain nanocomposites with homogeneously structured and abundant redox sites, and the bimetallic oxides nanomaterials had enhanced electrocatalysis under the synergistic effect. The flexible electrode prepared from FexCoyO4-rGO exhibited excellent detection performance for glucose with a detection limit down low to 0.07 μM and a sensitivity of 1510 μM cm−2 mA−1. The adoption of flexible substrates improved the wearability of the electrode and broadened its practicality for detecting biomarkers on the skin surface. The constructed sensor was successfully used in the dynamic analysis of glucose content in tears, and the results were highly consistent with the test outcome of a commercial test kit, demonstrating its application prospects in non-invasive epidermal diabetes mellitus diagnosis.

Further optimisation of a macromolecular ocular irritation test (OptiSafeTM)

Purpose OptiSafeTM (OS) is a shelf stable, nonanimal test for ocular irritation. A recent database search found that half of the OS false positive (FP) materials were associated with reactive oxygen chemistries but were not eye irritants in vivo (based on historical rabbit studies by other groups). We hypothesized that naturally occurring tear antioxidants protect the eye from reactive chemistries in vivo and that specific tear chemistries might help explain why some materials are FP for nonanimal tests but are reported as nonirritants in the live animal. To test this hypothesis, a prior study evaluated tear antioxidants and found that the tear antioxidant ascorbic acid, added at human physiological tear levels to the OS test, specifically reduced the measured values for these FPs but did not reduce the true-positive rate. Based on these findings, the OS test method was further optimized. The purpose of the current study was to comprehensively evaluate the performance of the further optimized test method for detection of ocular irritants. Materials and methods The OS test measures chemically induced damage to macromolecules and relates these measured values to ocular irritancy. To improve the performance of OS, we made updates to the material to be tested physiochemical handling procedures, prediction model, and test method to include tear-level concentrations of ascorbic acid. We then retested the 78 chemicals from the prior OS-coded validation study in triplicate and compared the accuracy of the ‘nonirritant versus irritant’ prediction for the further optimized method with the prior results. Results We report that for the detection of ‘nonirritant’ versus ‘irritant’ (GHS NC versus categories 2B/A and 1) test substances, the further optimized OS test with ascorbic acid compared with the original version has a FP rate that is reduced from 40.0 to 22.2%, the false-negative (FN) rate remains at 0.0%, and the accuracy improved from 80.3% to 89.2%. Conclusion A comparison to OECD-adopted tests demonstrates that the further optimized OS test, like the original method, has a higher accuracy and lower FN rate for the detection of ‘nonirritants’ versus ‘irritants’ (GHS Category NC versus 2B/A and 1) than the other eye irritation tests (BCOP, EpiOcularTM Eye Irritation Test, ICE, Ocular Irritection®, and STE).

ITEARS: a novel platform for using tears as potential disease biomarkers.

Dear Editor, Exosomes are double-membrane lipid bilayer nanoparticles secreted into extracellular spaces by various cells of the body1. They can be found in several body fluids such as serum, breast milk, saliva, cerebrospinal fluid, semen, and urine in both physiological and pathological conditions2. They have been indicated to have diagnostic applications in terms of both their morphology and miRNA expression. Exosome extraction and assessment are made efficient by the identification of various transport proteins, CD9, CD81, and heat shock protein, all of which are an integral part of exosome composition3. Around 4400 distinct proteins have been identified in exosomes using mass spectrophotometry4. Much research is being conducted, which focuses on the employment of these vesicles as innovative biomarkers for diagnosis, prognosis, and management of cancer and other diseases2. In comparison with other biofluids, tears, because of their less protein and debris content as compared to blood and its noninvasive collection, are the most appropriate source for exosome isolation. Their easy accessibility for biomarker analysis using the Schirmer test strip greatly boasts its importance5. To gain access to the gateway of a multitude of diseases in a drop of tear, successful approaches have been adopted to isolate tear components such as glucose, lactoferrin, lysozyme, and alcohol, for depicting the pathological states including dry eye symptoms, infections, diabetes, cardiovascular disease, endothelial dysfunction, coagulopathies, and polycystic ovary syndrome6. They have also been applied in testing breast cancer further suggesting the noninvasive diagnostic potential of tear exosomes7. However, due to practical constraints in the isolation and handling of tear exosomes, despite their attractive potential, limited progress has been made in intensely acknowledging the clinical value of tear exosomes. Isolation is usually done on the principles relying on the size and particle density of exosomes. Tear exosomes isolation is commonly achieved by ultracentrifugation and size exclusion chromatography8. Ultracentrifugations’ efficiency is limited by its long processing time, large sample requirement, and low recovery while size exclusion chromatography lacks a proficient enrichment facility thus hampering the use of tear exosomes as diagnostic tools and discouraging further studies. Since the volume of tears samples collected from patients is usually scarce and the extraction procedure is complex, novel procedures are needed to be developed for paving new dimensions of disease deciphering by using tear as a sample. Recently a team of researchers developed an incorporated tear-exosome analysis via a rapid-isolation system (iTEARS) platform to better comprehend exosome study and enhance exosome extraction9. iTEARS is a microstructure-based device containing a dual nanoporous membrane installed in a reservoir with two outlets operating on basis of a negative-pressure-oscillation strategy and on-device immunodetection. To ensure fast exosome isolation, alternate negative pressure switching is applied on both sides, and in this way, large particle exosomes get captured while small fragments (eg, proteins, sugars) are separated. This experiment exhibits that exosome can be enriched positively in under 5 minutes. The separated exosomes can then be utilized for different diagnostic analyses like PCR, sequencing, and proteomics. For practical utility of iTEARS, laboratory analysis of these exosomes was performed to distinguish a healthy control from Diabetes Mellitus and Diabetic Retinopathy. It was also used to identify different dry eye diseases thus emphasizing the important role of iTEARS and a hope for it discovering various other clinical conditions and their molecular diagnosis. In the field of medicine, there is an ever occurring need to explore and identify new techniques for the diagnosis of disease and progression of pathology. Studies around human tear analysis have shown the potential to be a reliable and efficient method to present biomarkers for various pathological conditions of the human body. iTEARS technique not only produces results but is cost-effective and time friendly as well. Mega-scale clinical trials are needed to verify its potential for the diagnosis of disease. Tear sampling via iTEARS is feasible, noninvasive, easy to conduct, and effective. Ethical approval Not applicable. Sources of funding None. Author's contribution All authors equally contributed. Conflicts of interest disclosure The authors declare that they have no financial conflict of interest with regard to the content of this report. Research registration Unique Identifying number (UIN) None. Guarantor Syeda Shahnoor.

Microfluidic contact lenses for ocular diagnostics and drug delivery

AbstractThe human eye and tear provide essential physiological information for the detection of ocular dysfunctions and therapy monitoring. The measurements of biomarkers in tear composition are critical for disease diagnosis and early interventions. Hence, significant efforts are dedicated to the development of functional contact lenses that can quantify tear analytes and ocular physiological condition. The combination of microfluidics and contact lens technologies offer real‐time monitoring of ocular physiology and timely detection of eye disorders through wireless components. This review discusses the fundamentals of microfluidic contact lenses and their diverse applications in ophthalmic diagnostics and drug delivery. It also elucidates the strategies for the commercialization of microfluidic contact lenses to create clinical and point‐of‐care products.

A biophysical study of tear film lipid layer model membranes

The tear film lipid layer (TFLL), the final layer of the human tear film is responsible for surface tension reduction while blinking, water evaporation retardation and maintaining the stability of the tear film. The study of the composition-structure-function relationship of TFLL is paramount, as a compromised structure of TFLL leads to the emergence of dry eye disease (DED) which is one the most prevalent ophthalmic surface diseases of the modern world, associated with chronic pain and reduced visual capability. In this model membrane study, a systematic approach is used to study the biophysical properties of TFLL model membranes as a function of composition. Three mixed-lipid model membranes are studied along with their individual components comprising cholesteryl oleate (CO), glyceryl trioleate (GT), L-α-phosphatidylcholine (egg PC) and a free fatty acid mixture. The models become progressively more complex from binary to quaternary mixtures, allowing the role of each individual lipid to be derived. Langmuir balance, Brewster Angle Microscopy (BAM) and Profile Analysis Tensiometer (PAT) are used to study the surface activity and compression-expansion cycles, morphology, and rheological behaviour of the model membranes, respectively. Evidence of multilayering is observed with inclusion of CO and a reversible collapse is associated with the GT phase transition. An initially more coherent film is observed due to the addition of polar PC. Notably, these individual behaviours are retained in the mixed films and suggest a possible role for each physiological component of TFLL.