Lactoferrin Concentration in Human Tears and Ocular Diseases: A Meta-Analysis

Customizable OpenGUS immunoassay: A homogeneous detection system using β-glucuronidase switch and label-free antibody

We developed a customizable OpenGUS immunoassay that enables rapid and sensitive detection of analytes without requiring antibody modification. This immunoassay employs label-free whole antibodies, an antibody-binding Z domain (ZD) derived from Staphylococcal protein A, and a β-glucuronidase (GUS) switch mutant, allowing for easy replacement of antibodies to tailor the immunoassays for various targeted antigens. The working principle is that the OpenGUS probe, the fusion protein of ZD and a GUS switch, converts the antibody-antigen interaction into GUS activation in a one-pot reaction. To enhance the signal-to-background ratio of the immunoassay, a GUS switch mutant that exhibits reduced background activation was developed by screening several additional mutations at the diagonal interface residue H514. Moreover, we optimized the composition of the reaction buffer, including organic solvents, salt, and surfactant. Under optimal conditions, we customized OpenGUS immunoassays for Cry j 1, human C-reactive protein, and human lactoferrin, achieving around 10-20-fold maximum fluorescence (15 min) or colorimetric (2 h) responses with picomolar to low nanomolar level detection limit, simply by using commercially available IgGs. Additionally, the three analytes were successfully detected in complex matrices similar to those used in practical applications. We believe that this customizable OpenGUS immunoassay will pave the way for the prompt development of rapid and sensitive homogeneous immunoassays for point-of-care diagnostics, high-throughput testing, and onsite environmental assessments.

Lactoferrin as a Versatile Agent in Nanoparticle Applications: From Therapeutics to Agriculture

Nanoparticles (NPs) have emerged as a potent choice for various applications, from drug delivery to agricultural studies, serving as an alternative and promising methodology for future advancements. They have been widely explored in delivery systems, demonstrating immense promise and high efficiency for the delivery of numerous biomolecules such as proteins and anticancer agents, either solely or modified with other compounds to enhance their capabilities. In addition, the utilization of NPs extends to antimicrobial studies, where they are used to develop novel antibacterial, antifungal, and antiviral formulations with advanced characteristics. Lactoferrin (Lf) is a glycoprotein recognized for its significant multifunctional properties, such as antimicrobial, antioxidant, anti-inflammatory, anticancer, and neuroprotective effects. Its activity has a broad distribution in the human body, with Lf receptors present in multiple regions. Current research shows that Lf is utilized in NP technology as a surface material, encapsulated biomolecule, and even as an NP itself. Due to the abundance of Lf receptors in various regions, Lf can be employed as a surface material in NPs for targeted delivery strategies, particularly in crossing the BBB and targeting specific cancers. Furthermore, Lf can be synthesized in an NP structure, positioning it as a strong candidate in future NP-related applications. In this article, we explore the highlighted and underexplored areas of Lf applications in NPs research.

Global research hotspots and trends in anti-inflammatory studies in dry eye: a bibliometric analysis (2004-2024)

Background

Inflammation plays a crucial role in the pathophysiology of dry eye (DE). This study aims to provide a comprehensive overview of the current status, hotspots and trends in DE anti-inflammatory research through bibliometric analysis.

Method

All publications were searched using the Web of Science Core Collection (WoSCC) database from 2004 to 2024. Bibliometric analyses were performed using VOSviewer, R-bibliometrix, and CiteSpace, and data were managed using Microsoft Office Excel 2019.

Results

There were 603 papers published between 2004 and 2024 included in this study, with the number of papers increasing each year. The United States was the major contributor, with the largest number of publications and the greatest impact. Baylor College of Medicine was the most influential research institution. Pflugfelder, Stephen C. and Tsubota, Kazuo were the most prolific authors in this area of research, while Dana, Reza was the most cited author in the field with the highest impact. The Journal with the highest number of publications was Investigative Ophthalmology & Visual Science, while the highest impact journal was Ocular Surface. Research hotspots were focused on the mechanisms of inflammation in DE and interventions for anti-inflammatory therapy. Future studies would favor more inflammation-related targeted therapies and physical therapies.

Conclusion

This study is the first bibliometric analysis to comprehensively summarize research trends and developments in DE anti-inflammatory treatments, pointing out recent research frontiers and hot directions for scholars studying DE anti-inflammatory treatments.

Four-Week GLP Immunotoxicity Assessment of Lactoferrin Alpha Produced by Komagataella phaffii in Sprague-Dawley Rats

Oral toxicity and toxicokinetic properties of human lactoferrin (LF) alpha produced in Komagataella phaffii (effera™) were investigated in adult Sprague-Dawley rats over a 28-day period under good laboratory practice conditions. Main study dosing used groups of 10 rats/sex/dose, and a secondary study evaluating toxicokinetic parameters used 6 rats/sex/dose. The vehicle control group received sodium citrate buffer, test groups received daily doses of 200, 600, and 2000 mg of effera™ per kg body weight, and the comparative control group received 2000 mg bovine LF (bLF)/kg body weight per day. T-cell-dependent antibody response against keyhole limpet hemocyanin and immunophenotyping of the spleen were performed as measures of immunotoxicity. Clinical observations, body weight, hematology, coagulation, clinical chemistry, urinalysis, immunotoxicity, gross necropsy, and histopathology were assessed. Toxicokinetic parameters were analyzed as an indication of LF bioavailability, and anti-LF antibody assays were conducted to detect antibodies produced against LF to measure immunogenicity. No treatment related toxicologically significant changes were observed. Based on the absence of toxicologically relevant changes, effera™ is well tolerated in rats at doses up to 2000 mg rhLF/kg/day, an amount ∼400 times that of the estimated daily intake at the 90th percentile proposed for human adult use.

Tear-Based Ocular Wearable Biosensors for Human Health Monitoring

Wearable tear-based biosensors have garnered substantial interest for real time monitoring with an emphasis on personalized health care. These biosensors utilize major tear biomarkers such as proteins, lipids, metabolites, and electrolytes for the detection and recording of stable biological signals in a non-invasive manner. The present comprehensive review delves deep into the tear composition along with potential biomarkers that can identify, monitor, and predict certain ocular diseases such as dry eye disease, conjunctivitis, eye-related infections, as well as diabetes mellitus. Recent technologies in tear-based wearable point-of-care medical devices, specifically the state-of-the-art and prospects of glucose, pH, lactate, protein, lipid, and electrolyte sensing from tear are discussed. Finally, the review addresses the existing challenges associated with the widespread application of tear-based sensors, which will pave the way for advanced scientific research and development of such non-invasive health monitoring devices.

A Review of the Tear Film Biomarkers Used to Diagnose Sjogren's Syndrome

This literature review looks at Sjogren's Syndrome (SS), a chronic autoimmune disorder affecting exocrine glands, particularly the lacrimal and salivary glands. SS manifests as ocular and oral dryness, with severe complications like visual dysfunction and corneal perforation, as well as systemic implications, such as interstitial lung disease and lymphoma. This review explores the use of tear film biomarkers to diagnose SS, emphasizing the significance of their identification in aiding clinical diagnosis and differentiation from other diseases. This study identified and analyzed 15 papers, encompassing 1142 patients and employing various tear sample collection methods. Tear biomarkers were categorized by function and explored in-depth. Categories include (1) antimicrobials, antivirals, and antifungals; (2) components of immune regulation; (3) components that regulate metabolic processes; and (4) inflammatory markers. Noteworthy findings include the potential diagnostic values of tear lysozyme, lactoferrin, dinucleoside polyphosphates, cathepsin, defensin, antibodies, epidermal fatty acid-binding protein, HLA-DR, ADAM10, aquaporin 5, and various miRNAs and mRNAs. Overall, our understanding of SS tear film composition is enhanced, providing valuable insights into the pathogenesis of SS and offering a foundation for future diagnostic and therapeutic advancements in autoimmune conditions affecting the ocular surface.

TACSTD2 in gelatinous drop-like corneal dystrophy: variant functional analysis and expression in the cornea after limbal stem cell transplantation

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive eye disease. GDLD is characterized by the loss of barrier function in corneal epithelial cells (CECs) and amyloid deposition due to pathogenic variants in the TACSTD2 gene. Limbal stem cell transplantation (LSCT) has been suggested as an effective therapeutic alternative for patients with GDLD. However, despite LSCT, amyloid deposition recurs in some patients. The pathogenesis of recurrence is poorly studied. We present the case of a patient with GDLD. Genetic analysis revealed a homozygous deletion, NM_002353.3:c.653del, in the TACSTD2 gene. Functional analysis in a cell model system revealed the loss of the transmembrane domain and subcellular protein mislocalization. The patient with GDLD underwent direct allogeneic LSCT with epithelial debridement followed by deep anterior lamellar keratoplasty 10 months later due to amyloid deposition and deterioration of vision. Taken together, the results of transcriptome analysis and immunofluorescence staining of post-LSCT corneal sample with amyloid deposits obtained during keratoplasty demonstrated complete restoration of wild-type TACSTD2 expression, indicating that donor CECs replaced host CECs. Our study provides experimental evidence that amyloid deposition can recur after LSCT despite complete restoration of wild-type TACSTD2 expression.

Dose Range-Finding Toxicity Study in Rats With Recombinant Human Lactoferrin Produced in Komagataella phaffii

The oral toxicity of recombinant human lactoferrin (rhLF, Helaina rhLF, Effera™) produced in Komagataella phaffii was investigated in adult Sprague Dawley rats by once daily oral gavage for 14 consecutive days. The study used groups of 3-6 rats/sex/dose. The vehicle control group received sodium citrate buffer, and the test groups received daily doses of 200, 1000, and 2000 mg of rhLF in sodium citrate buffer per kg body weight. Bovine LF at 2000 mg/kg body weight per day was used as a comparative control. Clinical observations, body weight, hematology, clinical chemistry, iron parameters, immunophenotyping, and gross examination at necropsy were used as criteria for detecting the effects of treatment in all groups and to help select dose levels for future toxicology studies. Quantitative LF levels were also analyzed as an indication of bioavailability. Overall, administration of Helaina rhLF by once daily oral gavage for 14 days was well tolerated in rats at levels up to 2000 mg/kg/day, or 57 × Helaina's intended commercial use in adults, and indicating that a high dose of 2000 mg/kg/day is appropriate for future definitive toxicology studies.

Development, Optimization, and Clinical Relevance of Lactoferrin Delivery Systems: A Focus on Ocular Delivery

Lactoferrin (Lf), a multifunctional protein found abundantly in secretions, including tears, plays a crucial role in ocular health through its antimicrobial, immunoregulatory, anti-inflammatory, and antioxidant activities. Advanced delivery systems are desirable to fully leverage its therapeutic potential in treating ocular diseases. The process of Lf quantification for diagnostic purposes underscores the importance of developing reliable, cost-effective detection methods, ranging from conventional techniques to advanced nano-based sensors. Despite the ease and non-invasiveness of topical administration for ocular surface diseases, challenges such as rapid drug elimination necessitate innovations, such as Lf-loaded contact lenses and biodegradable polymeric nanocapsules, to enhance drug stability and bioavailability. Furthermore, overcoming ocular barriers for the treatment of posterior segment disease calls for nano-formulations. The scope of this review is to underline the advancements in nanotechnology-based Lf delivery methods, emphasizing the pivotal role of multidisciplinary approaches and cross-field strategies in improving ocular drug delivery and achieving better therapeutic outcomes for a wide spectrum of eye conditions.

Recommendations for nutritional supplements for dry eye disease: current advances

Dry eye disease (DED) represents a prevalent ocular surface disease. The development of effective nutritional management strategies for DED is crucial due to its association with various factors such as inflammation, oxidative stress, deficiencies in polyunsaturated fatty acids (PUFAs), imbalanced PUFA ratios, and vitamin insufficiencies. Extensive research has explored the impact of oral nutritional supplements, varying in composition and dosage, on the symptoms of DED. The main components of these supplements include fish oils (Omega-3 fatty acids), vitamins, trace elements, and phytochemical extracts. Beyond these well-known nutrients, it is necessary to explore whether novel nutrients might contribute to more effective DED management. This review provides a comprehensive update on the therapeutic potential of nutrients and presents new perspectives for combination supplements in DED treatment.

Tear biomarkers

An extensive exploration of lacrimal fluid molecular biomarkers in understanding and diagnosing a spectrum of ocular and systemic diseases is presented. The chapter provides an overview of lacrimal fluid composition, elucidating the roles of proteins, lipids, metabolites, and nucleic acids within the tear film. Pooled versus single-tear analysis is discussed to underline the benefits and challenges associated with both approaches, offering insights into optimal strategies for tear sample analysis. Subsequently, an in-depth analysis of tear collection methods is presented, with a focus on Schirmer's test strips and microcapillary tubes methods. Alternative tear collection techniques are also explored, shedding light on their applicability and advantages. Variability factors, including age, sex, and diurnal fluctuations, are examined in the context of their impact on tear biomarker analysis. The main body of the chapter is dedicated to discussing specific biomarkers associated with ocular discomfort and a wide array of ocular diseases. From dry eye disease and thyroid-associated ophthalmopathy to keratoconus, age-related macular degeneration, diabetic retinopathy, and glaucoma, the intricate relationship between molecular biomarkers and these conditions is thoroughly dissected. Expanding beyond ocular pathologies, the chapter explores the applicability of tear biomarkers in diagnosing systemic diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, and cancer. This broader perspective underscores the potential of lacrimal fluid analysis in offering non-invasive diagnostic tools for conditions with far-reaching implications.

New advances in medical management of dry eye: optimizing treatment strategies for enhanced relief

PURPOSE

Dry eye disease (DED) is a prevalent ocular surface disease that is conventionally characterized by tear film hyperosmolarity and instability. This review presents a summarized classification of DED, followed by a comprehensive discussion of the most recent topical and systemic medications and clinical recommendations for selecting the most appropriate option for each patient.

METHODS

An extensive literature search was conducted on electronic databases, such as PubMed, Scopus, and Web of Science, using keywords including "dry eye syndrome," "ocular surface disease," "medical management," "artificial tears," "topical immunomodulators," and "meibomian gland dysfunction."

RESULTS

The underlying reasons for DED can range from insufficient aqueous tear production to increased tear evaporation. Recent literature has provided a more in-depth understanding of the pathophysiology of DED by examining the tear film's lipid, aqueous, and mucin layers. However, despite these advancements, medical management of patients with symptomatic DED has not fully reflected this modernized knowledge of its pathophysiology.

CONCLUSION

To develop a rationalized strategy for treating DED, it is crucial to have updated knowledge of therapeutic options, their mechanisms of actions, and indications based on the DED type and underlying causes.

Developing an improved optical biosensing system based on gold nanoparticles acting as interferometric enhancers in Lactoferrin detection

We report for the first time the whole development of a biosensing system based on the Interferometric Optical Detection Method (IODM) enriched with gold nanoparticles (AuNPs), acting as interferometric enhancers for improving the performance of immunoassays. For this purpose, the Lactoferrin sandwich immunoassay model was employed. We describe in detail the entire value chain from the AuNPs production, its functionalization, and characterization with anti-Lactoferrin (anti-LF), the biosensing response of these conjugates as well as their corresponding calculation of the kinetic constants, performance comparison of the readout interferometric signals versus Scanning Electron Microscopy (SEM) and the percentage of the sensing surface covered. Finally, a Lactoferrin sandwich immunoassay was carried out and correlated with Enzyme-Linked ImmunoSorbent Assay (ELISA), and the Limit of Detection and sensitivity figures were obtained. As a result, we demonstrate how the AuNPs act as interferometric amplifiers of the IODM for improving the biosensing response, opening the possibility of being applied in multiple biological detection applications.

Rapid detection of tear lactoferrin for diagnosis of dry eyes by using fluorescence polarization-based aptasensor

Differentiating dry eye disease (DED) from allergic or viral conjunctivitis rapidly and accurately is important to ensure prompt diagnosis and treatment. Tear lactoferrin (LF), a multi-functional glycoprotein found in tears, decreases significantly in patients with DED, and has been considered as a DED diagnostic biomarker. Measuring tear LF level, however, takes time and requires the use of bulky instruments. Herein, a homogeneous carbon nanostructure-based aptasensor with high sensitivity and selectivity has been developed by applying fluorescence polarization (FP) technology. The FP of carbon dots (CDs) bioconjugated with LF aptamers (CDs-aptamer) is 21.2% higher than that of CDs, which can be further amplified (1.81 times) once interacting with graphene oxide nanosheets (GONS). In the presence of LF, GONS separates from CDs-aptamer because of the stronger binding affinity between CDs-aptamer to LF, resulting in the decrease of FP value. A linear relationship is observed between FP value and LF concentration in spiked tear samples from 0.66 to 3.32 mg/mL. The selectivity of the aptasensor has been investigated by measuring other proteins. The results indicate that the FP-based aptasensor is a cost-effective method with high sensitivity and selectivity in detection of tear LF.

How Can We Best Diagnose Severity Levels of Dry Eye Disease: Current Perspectives

Dry eye disease (DED) is a common ocular condition, but the diagnosis relative to other ocular conditions and the evaluation of severity of the condition has often been difficult. This challenge can be due to clinical signs and symptoms not always correlating with each other. An understanding of the various components which create the condition, as well as the diagnostic measures used to evaluate these components, is useful to the clinician working with DED patients. This review paper will discuss traditional diagnostic options, diagnostic imaging, and Advanced Point of Care testing capabilities to determine the severity level of dry eye disease more adequately.

Role of topical and systemic immunosuppression in aqueous-deficient dry eye disease

Immunosuppression in aqueous-deficient dry eye disease (ADDE) is required not only to improve the symptoms and signs but also to prevent further progression of the disease and its sight-threatening sequelae. This immunomodulation can be achieved through topical and/or systemic medications, and the choice of one drug over the other is determined by the underlying systemic disease. These immunosuppressive agents require a minimum of 6-8 weeks to achieve their beneficial effect, and during this time, the patient is usually placed on topical corticosteroids. Antimetabolites such as methotrexate, azathioprine, and mycophenolate mofetil, along with calcineurin inhibitors, are commonly used as first-line medications. The latter have a pivotal role in immunomodulation since T cells contribute significantly to the pathogenesis of ocular surface inflammation in dry eye disease. Alkylating agents are largely limited to controlling acute exacerbations with pulse doses of cyclophosphamide. Biologic agents, such as rituximab, are particularly useful in patients with refractory disease. Each group of drugs has its own side-effect profiles and requires a stringent monitoring schedule that must be followed to prevent systemic morbidity. A customized combination of topical and systemic medications is usually required to achieve adequate control, and this review aims to help the clinician choose the most appropriate modality and monitoring regimen for a given case of ADDE.

Physical Properties and Interaction With the Ocular Surface of Water-Gradient Contact Lenses

ABSTRACT

Since the introduction of silicone hydrogel contact lenses, many silicone-hydrogel materials have been produced, including water-gradient contact lenses with a silicone hydrogel core and a thin hydrogel outer layer (e.g., delefilcon A, verofilcon A, and lehfilcon A). Their properties have been investigated in various studies assessing both the chemical-physical characteristics and the comfort, but the overall picture is not always consistent. In this study, water-gradient technology is reviewed by looking at basic physical properties both in vitro and in vivo and at the interaction with the human ocular surface. Surface and bulk dehydration, surface wetting and dewetting, shear stress, interaction with tear components and with other environmental compounds, and comfort are discussed.

Biomedical Applications of Lactoferrin on the Ocular Surface

Lactoferrin (LF) is a first-line defense protein with a pleiotropic functional pattern that includes anti-inflammatory, immunomodulatory, antiviral, antibacterial, and antitumoral properties. Remarkably, this iron-binding glycoprotein promotes iron retention, restricting free radical production and avoiding oxidative damage and inflammation. On the ocular surface, LF is released from corneal epithelial cells and lacrimal glands, representing a significant percentage of the total tear fluid proteins. Due to its multifunctionality, the availability of LF may be limited in several ocular disorders. Consequently, to reinforce the action of this highly beneficial glycoprotein on the ocular surface, LF has been proposed for the treatment of different conditions such as dry eye, keratoconus, conjunctivitis, and viral or bacterial ocular infections, among others. In this review, we outline the structure and the biological functions of LF, its relevant role at the ocular surface, its implication in LF-related ocular surface disorders, and its potential for biomedical applications.

Point of care diagnosis of dry eye disease with a sensitive immunoassay for dual biomarker detection

Dry eye disease (DED) is a multifactorial eye disease with few effective methods for clinical diagnosis and treatment. It is the most common eye disease with significant health challenges of the unprecedented aging population. Recent proteomic studies and clinical research have led to the discovery of several biologically relevant biomarkers, with increased levels of Interleukin-6 (IL-6) and decreased levels of lactoferrin being clinically validated in the progression of DED. In this study, a sensitive point of care (POC) DED diagnostic method was developed for targeting dual biomarkers of IL-6 and lactoferrin in the tear samples. A paper-based lateral flow immunoassay (LFIA) was established in a double-antibody sandwich fashion with colloid gold nanoparticles acting as probes. The minimal detection concentrations were 0.1 ng/ml and 10 ng/ml for IL-6 and lactoferrin, respectively. Separated conventional ELISA tests were also performed with data confirming results from the LFIA tests. A trial study was conducted with 20 tear samples from DED patients and healthy controls. All DED tear samples exhibited significantly higher levels of IL-6 and decreased levels of lactoferrin, as compared to the normal controls. A quantitative analysis of LFIA images was carried out using ImageJ software for an accurate data interpretation. This dual biomarker detection method is sensitive and affordable with quick turnaround time. Design of a larger clinical study in the future can further validate this POC assay for early diagnosis as well as patients' self-management of chronic states of DED.

Contact Lens Wear Induces Alterations of Lactoferrin Functionality in Human Tears

The tear film is a complex matrix composed of several molecular classes, from small metal ions to macromolecules. Contact lens (CL) wear can affect the protein homeostasis of the tear film, by accumulating deposits on the CL surface and/or altering their structural and functional properties. This work investigates the effect of CL wear on lactoferrin (Lf), one of the most abundant tear proteins, known as an unspecific biomarker of inflammation. Tears from eight volunteers were collected and analyzed after alternated periods of CL wear and without CL. The experimental approach is to probe Lf into unprocessed human tears by the peculiar fluorescence emission originating from complex formation of Lf with terbium (Tb³⁺) at the iron-binding sites. The experimental data indicate that CL wear does not significantly affect the total amount of Lf. On the other hand, Lf affinity for Tb³⁺ is reduced upon CL wear, suggesting relevant changes in Lf structure and possible alterations of protein functionality. Future studies based on this approach will help define CL features (material, lens-care solution, wearing time, etc.) with minimal effects on tear protein activity, in order to obtain more biocompatible and comfortable devices.

Mass spectrometry-based tear proteomics for noninvasive biomarker discovery

The lacrimal film has attracted increasing interest in the last decades as a potential source of biomarkers of physiopathological states, due to its accessibility, moderate complexity, and responsiveness to ocular and systemic diseases. High-performance liquid chromatography-mass spectrometry (LC-MS) has led to effective approaches to tear proteomics, despite the intrinsic limitations in sample amounts. This review focuses on the recent progress in strategy and technology, with an emphasis on the potential for personalized medicine. After an introduction on lacrimal-film composition, examples of applications to biomarker discovery are discussed, comparing approaches based on pooled-sample and single-tear analysis. Then, the most critical steps of the experimental pipeline, that is, tear collection, sample fractionation, and LC-MS implementation, are discussed with reference to proteome-coverage optimization. Advantages and challenges of the alternative procedures are highlighted. Despite the still limited number of studies, tear quantitative proteomics, including single-tear investigation, could offer unique contributions to the identification of low-invasiveness, sustained-accessibility biomarkers, and to the development of personalized approaches to therapy and diagnosis.

Lactoferrin and its nano-formulations in rare eye diseases

Lactoferrin (LF) is an iron-binding glycoprotein released from mucous secreting cells and neutrophils. LF can be used in a broad range of eye diseases related to the retina, cornea, and optic nerve. The retina is particularly affected by oxidative stress inside the photoreceptor being constantly exposed to light which induces accumulation of reactive oxygen species (ROS) in the retinal pigmented epithelium (RPE) causing damage to photoreceptor recycling. Retinitis pigmentosa (RP) and macular degeneration are inherited retinopathies that consist of different disease-causing genes, that cause mutations with highly varied clinical consequences. Age-related macular degeneration is a chronic disease of the retina and one of the major causes of sight loss. This review provides an application of lactoferrin and LF-based nano-formulations or nanoparticles in the field of retinal diseases or corneal diseases such as retinitis pigmentosa, retinoblastoma, age-related macular degeneration (AMD), keratoconus and uveitis. Several studies have found that lactoferrin's antibacterial activity is not limited to its iron sequestration, but also its ability as a nanoparticle that acts as a carrier to deliver drugs by crossing the blood-retina barrier (BRB) and its involvement in cell cycle control, which is not possible by many transferrin proteins.

Current and Future Perspectives on Microfluidic Tear Analytic Devices

Most current invasive analytic devices for disease diagnosis and monitoring require the collection of blood, which causes great discomfort for patients and may potentially cause infection. This explains the great need for noninvasive devices that utilize other bodily fluids like sweat, saliva, tears, or urine. Among them, eye tears are easily accessible, less complex in composition, and less susceptible to dilution. Tears also contain valuable clinical information for the diagnosis of ocular and systemic diseases as the tear analyte level shows great correlation with the blood analyte level. These unique advantages make tears a promising platform for use in clinical settings. As the volume of tear film and the rate of tear flow are only microliters in size, the use of microfluidic technology in analytic devices allows minimal sample consumption. Hence, more and more microfluidic tear analytic devices have been proposed, and their working mechanisms can be broadly categorized into four main types: (a) electrochemical, (b) photonic crystals, (c) fluorescence, and (d) colorimetry. These devices are being developed toward the application of point-of-care tests with rapid yet accurate results. This review aims to provide a general overview of the recent developmental trend of microfluidic devices for tear analysis. Moreover, the fundamental principle behind each type of device along with their strengths and weaknesses will be discussed, especially in terms of their abilities and potential in being used in point-of-care settings.

Viscoelastic properties of the human tear film

When considering eye blinking from a tribological perspective, tear viscosity is expected to play a fundamental role. The application of rheological techniques to describe the tear film dates back to the late 1980s, but there has been a continuous need of reappraisal due to new findings in tear film biochemistry and to the development of new methods of physico-chemical characterization. This review provides an overview on tear rheological behavior by analyzing the peer-reviewed literature on this topic. Specifically, examples of in-vitro and in-vivo viscosity measurements are detailed, highlighting experimental criticalities and the need of a standard convention for rheological techniques to compare data across different studies, of analyses on tears of single individuals even within the limits of the low volume available, and of a further development of in-vivo techniques. Then, the controversial role of specific tear components on viscosity is discussed, together with the alterations associated to dry eye disease and contact lens wear. Finally, an updated focus is reported on the viscosity of artificial tears formulations.

Strip Meniscometry Tube in the Assessment of Tear Lactoferrin in Non-Obese Diabetic (NOD) Mice

Purpose: To investigate the applicability of strip meniscometry tube (SMT) in the measurement of tear lactoferrin in non-obese diabetic mice (NOD). Methods: SMT (SMTube, Echo Electricity Co., Ltd., Tokyo, Japan) and fluorescein staining tests were performed on 7–14 week NOD- male mice (n = 4) and age and sex matched wild–type (Balbc, WT) mice (n = 5). Tears collected during SMT underwent lactoferrin concentration measurement by ELISA. Results: The mean SMT value was significantly lower in NOD mice compared to wild-type mice (p = 0.01). The mean corneal fluorescein staining score in the NOD mice was significantly lower compared with the wild-type mice (p = 0.03). The mean tear lactoferrin level also showed a significantly lower concentration in NOD mice (p = 0.02). Conclusions: SMT has been shown to be an effective tool in measuring tear volume in humans, cats, dogs, and mice. SMT may also serve as a useful tool for tear lactoferrin assessment in NOD and WT mice in experimental settings.

Targeted Analysis of Tears Revealed Specific Altered Metal Homeostasis in Age-Related Macular Degeneration

Purpose

Specific altered metal homeostasis has been investigated in the tear film of age-related macular degeneration (AMD) patients considering that metal dyshomeostasis contributes to the production of free radicals, inflammation, and apoptosis and results in conformational changes of proteins.

Methods

A multitargeted approach based on spectrophotometry and mass spectrometry techniques has been implemented to the multiplexed quantitation of lactoferrin (LF), S100 calcium binding protein A6 (S100A6), metallothionein 1A (MT1A), complement factor H (CFH), clusterin (CLU), amyloid precursor protein (APP), Mg, P, Na, Fe, Cu, Zn, and Ca, in the tear film from 60 subjects, 31 patients diagnosed with the dry form of AMD, and 29 healthy individuals

Results

Significant up-regulations of MT1A (1.9-fold) and S100A6 (1.4-fold) and down-regulations of LF (0.7-fold), Fe (0.6-fold), Mg (0.7-fold), and Cu (0.7-fold) were observed in AMD patients, when compared to control subjects. Of all the studied variables, only APP showed negative correlation with age in the AMD group. Also, positive correlations were observed for the variables Mg and Na, Cu and Mg, and P and Mg in both the AMD and control groups, whereas positive correlations were exclusively determined in the AMD group for Cu and LF, Na and Ca, and Mg and Ca. The panel constituted of MT1A, Na, and Mg predicts AMD disease in 73% of cases.

Conclusions

The different levels of target metals and (metallo-)proteins in the tear film suggest altered metal homeostasis in AMD patients. These observed pathophysiological changes may be related with the anomalous protein aggregation in the macula.

Current Advances in Mechanisms and Treatment of Dry Eye Disease: Toward Anti-inflammatory and Immunomodulatory Therapy and Traditional Chinese Medicine

Dry eye is currently one of the most common ocular surface disease. It can lead to ocular discomfort and even cause visual impairment, which greatly affects the work and quality of life of patients. With the increasing incidence of dry eye disease (DED) in recent years, the disease is receiving more and more attention, and has become one of the hot research fields in ophthalmology research. Recently, with the in-depth research on the etiology, pathogenesis and treatment of DED, it has been shown that defects in immune regulation is one of the main pathological mechanisms of DED. Since the non-specific and specific immune response of the ocular surface are jointly regulated, a variety of immune cells and inflammatory factors are involved in the development of DED. The conventional treatment of DED is the application of artificial tears for lubricating the ocular surface. However, for moderate-to-severe DED, treatment with anti-inflammatory drugs is necessary. In this review, the immunomodulatory mechanisms of DED and the latest research progress of its related treatments including Chinese medicine will be discussed.

Development of Lactoferrin-Loaded Liposomes for the Management of Dry Eye Disease and Ocular Inflammation

Dry eye disease (DED) is a high prevalent multifactorial disease characterized by a lack of homeostasis of the tear film which causes ocular surface inflammation, soreness, and visual disturbance. Conventional ophthalmic treatments present limitations such as low bioavailability and side effects. Lactoferrin (LF) constitutes a promising therapeutic tool, but its poor aqueous stability and high nasolacrimal duct drainage hinder its potential efficacy. In this study, we incorporate lactoferrin into hyaluronic acid coated liposomes by the lipid film method, followed by high pressure homogenization. Pharmacokinetic and pharmacodynamic profiles were evaluated in vitro and ex vivo. Cytotoxicity and ocular tolerance were assayed both in vitro and in vivo using New Zealand rabbits, as well as dry eye and anti-inflammatory treatments. LF loaded liposomes showed an average size of 90 nm, monomodal population, positive surface charge and a high molecular weight protein encapsulation of 53%. Biopharmaceutical behaviour was enhanced by the nanocarrier, and any cytotoxic effect was studied in human corneal epithelial cells. Developed liposomes revealed the ability to reverse dry eye symptoms and possess anti-inflammatory efficacy, without inducing ocular irritation. Hence, lactoferrin loaded liposomes could offer an innovative nanotechnological tool as suitable approach in the treatment of DED.

Single-Tear Proteomics: A Feasible Approach to Precision Medicine

Lacrimal fluid is an attractive source of noninvasive biomarkers, the main limitation being the small sample amounts typically collected. Advanced analytical methods to allow for proteomics profiling from a few microliters are needed to develop innovative biomarkers, with attractive perspectives of applications to precision medicine. This work describes an effective, analytical pipeline for single-tear analysis by ultrahigh-resolution, shotgun proteomics from 23 healthy human volunteers, leading to high-confidence identification of a total of 890 proteins. Highly reproducible quantification was achieved by either peak intensity, peak area, or spectral counting. Hierarchical clustering revealed a stratification of females vs. males that did not emerge from previous studies on pooled samples. Two subjects were monitored weekly over 3 weeks. The samples clustered by withdrawal time of day (morning vs. afternoon) but not by follow-up week, with elevated levels of components of the immune system in the morning samples. This study demonstrates feasibility of single-tear quantitative proteomics, envisaging contributions of this unconventional body fluid to individualized approaches in biomedicine.

Longitudinal Tear Protein Changes Correlate with Ocular Chronic GVHD Development in Allogeneic Hematopoietic Stem Cell Transplant Patients

Ocular graft-versus-host disease (oGVHD) is a manifestation of chronic GVHD, frequently occurring in patients after allogeneic hematopoietic stem cell transplant (HSCT). We analyzed tear protein changes before and after allogeneic HSCT, and correlated their levels with the oGVHD development. This retrospective study included 102 patients, and data were recorded before the conditioning treatment, and after 3 to 6 months postoperatively. Tear protein analysis was performed with the Agilent-2100 Bioanalyzer on individual tears sampled by aspiration. Total protein (TP), Lysozyme-C (LYS-C), Lactoferrin (LACTO), Lipocalin-1 (LIPOC-1), Transferrin (TRANSF), Albumin (ALB), and Zinc-alpha-2-glycoprotein (ZAG-2) levels were retrieved and statistically analyzed. Following HSCT forty-three patients developed oGVHD. TP, LACTO, LYS-C, and ZAG-2 levels significantly decreased post-HSCT as compared to pre HSCT levels. In univariate analysis, TP, LACTO, and ZAG-2 decrease was associated with an increased development of oGVHD (OR = 4.49; 95% CI, 1.9 to 10.5; p < 0.001; OR = 3.08; 95% CI 1.3 to 7.6; p = 0.01; OR = 11.1; 95% CI 2.7 to 46.6; p < 0.001, respectively). TRANSF post-HSCT levels significantly increased (OR 15.7; 95% CI, 4.1 to 52.2; p = 0.0001). No pre-post-HSCT changes were shown in ALB and LIPOC-1 levels. Data suggest that TP content, LACTO, TRANSF, and ZAG-2 pre-post changes might be significant predictors of oGVHD development.