Toxicity and phototoxicity in human ARPE-19 retinal pigment epithelium cells of dyes commonly used in retinal surgery

Presumed phototoxicity from macular vital staining with Brilliant Blue G and Trypan Blue: A post-market surveillance study, systematic review, and synthesis of the literature

Vital dyes are used to help visualize the retinal surface during macular surgery; however, they have been associated with phototoxicity. We synthesize and collate post-market surveillance data in two of the most commonly used dyes, Brilliant Blue G and Trypan Blue. We identified 69 cases, 59 of which were from the literature and 10 from manufacturer post-market surveillance. Of 69 vitrectomies, 39 were for macular hole, 24 for epiretinal membrane, 2 for vitreomacular traction, and 4 were not specified. The incidence of dye-mediated phototoxicity is likely rare, but is not possible to quantify, due to potential reporting and publication bias favouring dissemination of unusual safety events, but conversely underreporting is possible. Additionally, phototoxicity was reported prior to the introduction of vital stains, so it can be difficult to establish whether vital staining was contributory. Prolonged surgery and repeat staining were identified as risk factors. Characteristic clinical features were macular pigmentary change with hypo- and hyper-autofluoresence, often sparing the fovea. Final visual acuity tended to be worse than preoperatively, with some cases reduced to counting fingers. A reporting template is provided to encourage complete and standardised toxicity reporting and help build a robust evidence base.

Selective ILM Staining and Safety of Two Vital Dyes During a Human-Like Pars Plana Vitrectomy Ex Vivo in Porcine Eyes

PURPOSE

An ideal dye for intraocular use should effectively stain the target tissue while being easy to apply and remove. Additionally, it should not have any adverse effects resulting from prolonged contact with the retinal tissue. Recently, concerns have been raised about the safety of some vital dyes during surgical procedures as they may cross the internal limiting membrane and deposit on the retina. In this study, we aimed to investigate whether commercially available vital dyes, VIEW-ILM® and TWIN® (AL.CHI.MI.A. S.r.l., Ponte San Nicolò, Padova, Italy), have the potential to cross the internal limiting membrane during vitreoretinal surgery and deposit on the retina. Furthermore, we evaluated their safety in vitro and in vivo.

METHODS

A human-like pars plana vitrectomy was performed on porcine eyes ex vivo, with VIEW-ILM® or TWIN® used to stain the internal limiting membrane either with or without subsequent internal limiting membrane peeling. The two dyes were then extracted from retinal punches with or without internal limiting membrane, and quantified using high performance liquid chromatography. Safety was evaluated through in vitro cytotoxicity tests and in vivo skin sensitization and irritation tests according to ISO standards.

RESULTS

High performance liquid chromatography analyses demonstrated that VIEW-ILM® and TWIN® effectively stained the internal limiting membrane without crossing the membrane. No residual dyes were found in the retinal layers after internal limiting membrane removal. Furthermore, both in vitro and in vivo safety tests confirmed the absence of cytotoxicity, skin sensitization, and irritation.

CONCLUSION

The results of this study support the safety and efficacy of VIEW-ILM® and TWIN® for internal limiting membrane staining. The experimental protocol described in this study could be utilized to gain a comprehensive understanding of the characteristics of vital dyes.

The colorful world of sulfonephthaleins: Current applications in analytical chemistry for "old but gold" molecules

Sulfonephthaleins represent one of the most common and widely employed reactive dyes in analytical chemistry, thanks to their stability, low-cost, well-visible colors, reactivity and possibilities of chemical modification. Despite being first proposed in 1916, nowadays, these molecules play a fundamental role in biological and medical applications, environmental analyses, food quality monitoring and other fields, with a particular focus on low-cost and disposable devices or methods for practical applications. Since up to our knowledge, no reviews or book chapters focused explicitly on sulfonephthaleins have ever been published, in this review, we will briefly describe sulfonephthaleins history, their acid-base properties will be discussed, and the most recent applications in different fields will be presented, focusing on the last ten years literature (2014-2023). Finally, safety and environmental issues will be briefly discussed, despite being quite controversial.

[Exogenously induced retinopathies]

Exogenously induced retinopathies can be caused by consumation of stimulating substances, systemic or ocular medications, vaccinations, light or irradiation. Some of the effects are transient, whereas other effects induce irreversible toxic reactions. Retinal damage may develop either acutely with obvious relation to the damaging cause, but often may take a long duration of repeated use of a substance or medication. External stimulants (e.g. nicotine, alcohol, poppers, methanol) are the most frequent cause of exogenously induced retinal damage. Side effects from systemic drugs (e.g. hydroxychloroquine, ethambutol, MEK-, ERK-, FLT3-, checkpoint inhibitors, didanosin, pentosanpolysulfat sodium) or intravitreally applied drugs (e.g. antibiotics, VEGF-inhibitors) are less frequent. Ocular side effects associated with vaccinations are rare. Ambient light sources induce no damaging effects on the retina. Incorrect use of technical or medical light sources (e.g. laser pointers) without adherence to safety recommendations or unshielded observation of the sun might induce permanent retinal damage. Local or external irradiation might induce retinal vascular damage resulting in radiation retinopathy.

Exogen bedingte Retinopathien

Exogen bedingte Retinopathien werden am häufigsten durch externe Stimulanzien, seltener durch unerwünschte Arzneimittelwirkungen systemisch oder intravitreal eingesetzter Medikamente und noch seltener durch Impfungen oder die Einwirkung von Lichtstrahlung verursacht. Die Kenntnis exogener Ursachen und ihre mögliche Symptomatik ist zur Prophylaxe oder zur Früherkennung schädigender Wirkungen und zur adäquaten Beratung der Patienten wichtig.

New dual dye for vitreoretinal surgery with increased transparency

Objectives

To develop a new dye formulation for vitreoretinal surgery, which shows increased transparency for better intraoperative handling with better parameters important for use.

Methods and analysis

A new blue dye, DDG, was synthesised and tested for toxicity and staining. Diglycerol as new density-increasing additive was identified, and its toxicity and lack of influence of the staining with trypan blue (TB) on a collagen membrane as model for the epiretinal membrane was determined. Transparency of the dye solution was evaluated.

Results

DDG is as alternative to Brilliant Blue G (BBG), with good staining properties for interna limitans models, and a good safety profile. Diglycerol is a new non-toxic additive replacing PEG3350, with reduced viscosity and no reduction in staining, allowing the reduction of TB to achieve the same staining level of the collagen membrane by 40%, with greater transparency of the dye solution and reduced viscosity. Both factors should facilitate a safe removal during surgery.

Conclusion

A new dye preparation with improved performance in comparison to marketed combinations of BBG and TB was developed. Its reduced TB concentration and viscosity with maintained density allow better tolerance and handling.

Triazole-derivatized near-infrared cyanine dyes enable local functional fluorescent imaging of ocular inflammation

Near-infrared (NIR) chemical fluorophores are promising tools for in-vivo imaging in real time but often succumb to rapid photodegradation. Indocyanine green (ICG) is the only NIR dye with regulatory approval for ocular imaging in humans; however, ICG, when employed for applications such as labelling immune cells, has limited sensitivity and does not allow precise detection of specific inflammatory events, for example leukocyte recruitment during uveitic flare-ups. We investigated the potential use of photostable novel triazole NIR cyanine (TNC) dyes for detecting and characterising activated T-cell activity within the eye. Three TNC dyes were evaluated for ocular cytotoxicity in-vitro using a MTT assay and optimised concentrations for intraocular detection within ex-vivo porcine eyes after topical application or intracameral injections of the dyes. TNC labelled T-cell tracking experiments and mechanistic studies were also performed in-vitro. TNC-1 and TNC-2 dyes exhibited greater fluorescence intensity than ICG at 10 μM, whereas TNC-3 was only detectable at 100 μM within the porcine eye. TNC dyes did not demonstrate any ocular cell toxicity at working concentrations of 10 μM. CD4⁺T-cells labelled with TNC-1 or TNC-2 were detected within the porcine eye, with TNC-1 being brighter than TNC-2. Detection of TNC-1 and TNC-2 into CD4⁺T-cells was prevented by prior incubation with dynole 34-2 (50 μM), suggesting active uptake of these dyes via dynamin-dependent processes. The present study provides evidence that TNC dyes are suitable to detect activated CD4⁺T-cells within the eye with potential as a diagnostic marker for ocular inflammatory diseases.

RETINAL PIGMENT EPITHELIAL IRREGULARITY AND ATROPHY AFTER INTERNAL MEMBRANE PEELING: A REPORT OF TWO CASES

PURPOSE

To report two cases of widespread retinal pigment epithelial clumping, irregularity, and atrophy after uncomplicated 25-gauge pars plana vitrectomy with brilliant blue-green-assisted internal limiting membrane peeling.

METHODS

Retrospective analysis of 2 eyes of 2 patients who underwent 25-gauge pars plana vitrectomy for macular diseases (macular hole with retinal detachment and vitreomacular traction) was performed. Surgical notes and video recordings were reviewed to determine the surgical procedures performed and the duration of the surgery. Multimodal imaging analysis, including fundus photography, fundus autofluorescence imaging, and optical coherence tomography were performed to determine the pathological changes in the postoperative period.

RESULTS

The mean age of the patients (all females) was 78 years. In all the patients, brilliant blue-green-assisted internal limiting membrane peeling was performed without any intraoperative complications. Four weeks after an uncomplicated surgery, the patients complained of progressive central visual disturbance and metamorphopsia. Retinal imaging demonstrated retinal pigment epithelial clumps and irregularity, which appeared as hyperautofluorescent on fundus autofluorescence, and widespread retinal pigment epithelial atrophy (hypoautofluorescent on fundus autofluorescence) in the posterior pole and peripapillary region, along with retinal and choroidal thinning.

CONCLUSION

In uncomplicated vitrectomy consisting of brilliant blue-green-assisted internal limiting membrane peeling, a remote risk of widespread retinal pigment epithelial damage exists even with the use of modern endoilluminators and relatively short surgical duration. Retinal phototoxicity seems to be the primary cause; however, dye-related cytotoxicity or a combination of both cannot be ruled out.

A metal-free blue chromophore derived from plant pigments

Blue natural pigments are rare, especially among plants. However, flowering species that evolved to attract Hymenoptera pollinators are colored by blue anthocyanin-metal complexes. Plants lacking anthocyanins are pigmented by betalains but are unable to produce blue hues. By extending the π-system of betalains, we designed a photostable and metal-free blue dye named BeetBlue that did not show toxicity to human hepatic and retinal pigment epithelial cells and does not affect zebrafish embryonal development. This chiral dye can be conveniently synthesized from betalamic acid obtained from hydrolyzed red beetroot juice or by enzymatic oxidation of l-dopa. BeetBlue is blue in the solid form and in solution of acidified polar molecular solvents, including water. Its capacity to dye natural matrices makes BeetBlue the prototype of a new class of low-cost bioinspired chromophores suitable for a myriad of applications requiring a blue hue.

Metformin and rapamycin protect cells from vital dye-induced damage in retinal pigment epithelial cells and in vivo

PURPOSE

To evaluate the effect of autophagy inducers on damage caused by vital dye in adult human RPE (ARPE) cells and in a rat model.

METHODS

ARPE-19 cells were exposed to ICG or BBG (0.05 mg/ml) with rapamycin (200 nM) or metformin (2 mM) for 30 min and treated with or without 20 μM chloroquine (CQ) to identify the protein levels of LC3 and SQSTM1 by immunoblotting. In vivo study was performed by injecting 10 μl 0.05% ICG and 0.25% BBG into the subretinal space of the rat eyes, and/or co-treated them with metformin and rapamycin. The retinas were used to determine autophagy with the LC3-II level and apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assay.

RESULTS

In this study, both ICG and BBG inhibited autophagy flux in adult human retinal pigment epithelium cells (ARPE-19), whereas only ICG consistently reduced autophagy in the retina of rats. Moreover, rapamycin and metformin induced autophagic flux in ARPE-19 cells and increased the LC3-II level in retinal tissues exposed to vital dyes. Both ICG and BBG increased apoptosis in the retina of rats. However, both rapamycin and metformin induced autophagy and reduced the apoptosis caused by vital dyes.

CONCLUSION

Taken together, these results suggest that rapamycin and metformin may diminish vital dye-induced retinal damage in vivo through activation of autophagy.

Vital Dyes in Vitreomacular Surgery

Vital dyes contain complex molecules with chromophores that stain living tissues and have greatly enhanced identification and removal of transparent vitreoretinal tissues during surgery. Several "chromovitrectomy" dyes are frequently used by vitreoretinal specialists, including indocyanine green, trypan blue, brilliant blue G, and triamcinolone acetonide; other dyes are also under investigation. Trypan Blue was approved by the U.S. Food and Drug Administration (FDA) for epiretinal membrane removal, and preservative-free triamcinolone acetonide was approved by the FDA for intraocular use. However, currently available chromovitrectomy dyes have their limitations, and of particular concern for some of them is the possibility for acute and chronic toxicity to the neurosensory retina and retinal pigmented epithelium. The potentially irreversible acute toxicity and other limitations, such as lack of long-term safety profiles, highlight the need for further advancements. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:788-798.].

Effect of brilliant Blue-G on cellular stress response in retinal pigment epithelial cells: In vitro

To assess the cellular stress evoked by exposure of Brilliant Blue-G (BBG), adult retinal pigment epithelial (ARPE-19) cells were treated with various dilutions of BBG in balanced salt solution plus (BSS-PLUS) with and without endoillumination (Alcon Constellation Vision System). The treatments lasted for acute periods of 2 and 5 min. MTT and presto blue assays were performed to assess the changes in cell viability; reactive oxygen species (ROS) production was quantified by DCFDA (dichlorofluorescin diacetate) assay, and the expression of inflammatory stress and endoplasmic reticulum (ER) genes were quantified by qPCR. We observed no reduction in cell viability at 2 min of dye treatment with and without endoillumination while at 5 min exposure, a reduction in cell viability at all concentrations of the dye was observed compared to control. Though there was an increase in ROS with endoillumination, it was insignificant. There was no change in the mRNA expression of TNF-α while that of GRP78, and inflammatory genes viz. IL-8, IL-1β showed a significant increase at 0.5 mg/ml dye with endoillumination. BBG reduced cell viability with increasing concentration and time. The undiluted concentration of the dye results in inflammatory stress compared to the diluted formulations. Interestingly, increased GRP78 at undiluted concentration indicates a protective response in cells exposed to light. However, further studies are needed to evaluate the effect of cellular stress on the visual outcome. We infer that the commercially available formulation of BBG is safe for the RPE, at the recommended dose for a short duration however its toxicity to other cell types need to be addressed.