Comparative effects of six intraocular vital dyes on retinal pigment epithelial cells

MACULAR ATROPHY AFTER MACULAR HOLE SURGERY ASSISTED BY MEMBRANE BLUE DUAL: A CASE SERIES

PURPOSE

The aim of this study is to describe the clinical and multimodal imaging findings in patients with macular atrophy after macular hole surgery assisted by Membrane Blue Dual.

METHOD

This study is a monocenter, retrospective, observational case series that included patients who presented with macular atrophy following macular hole surgery.

RESULTS

Among the patients included in this study, four were operated for idiopathic macular hole and one for total retinal detachment associated with macular hole. In all patients, the internal limiting membrane was brittle and adherent, and multiple stains were required. One month postoperatively, all patients showed a reduced visual acuity except the patient with total retinal detachment. At fundus examination all patients showed patchy atrophy with a mottled hypopigmented and hyperpigmented appearance in the macular region. Optical coherence tomography scans demonstrated a closed macular hole with retinal thinning, disruption of the external retinal layers, and irregular retinal pigment epithelium thickening. Fundus autofluorescence showed a well-defined area of both hypoautofluorescence and hyperautofluorescence involving the macular area.

CONCLUSION

Macular atrophy after Membrane Blue Dual-assisted internal limiting membrane peeling represents a severe complication that vitreoretinal surgeons should be aware of and that should be taken into account in preoperative evaluation and surgical procedure planning. To reduce the risk of this complication, we recommend to ensure the best conditions of visibility, to reduce as much as possible the intensity and the distance of the endoillumination from the retina, and to use as little dye as possible.

Membrane Blue Dual Protects Retinal Pigment Epithelium Cells/Ganglion Cells-Like through Modulation of Mitochondria Function

Although recent data highlight the greater protective effects exerted by Membrane Blue Dual (MBD), a precise analysis of the mechanisms of action is missing. We examined the effects of MBD with/without polyethylene glycol (PEG) on both human retinal pigment epithelial cells (ARPE-19) and retinal ganglion cells-like (RGC-5) cultured in the presence/absence of ultraviolet B (UVB) treatment on mitochondria function, oxidants, and apoptosis. In ARPE-19/RGC-5 cells either treated or not with UVB, the effects of MBD with/without PEG were evaluated by specific assays for viability, mitochondrial membrane potential and mitochondrial reactive oxygen species (mitoROS) release. Annexin V was used to detect apoptosis, whereas trypan blue and the scratch assay were used for proliferation/migration. In both physiologic conditions and in the presence of UVB, MBD with/without PEG increased cell viability, mitochondrial membrane potential, proliferation and migration in both ARPE-19 and RGC-5 cells. In general, the effects of MBD with PEG were greater than those caused by MBD without PEG. Our results suggest that, in particular, MBD with PEG is a safe and effective dye for vitreoretinal surgery through the modulation of mitochondrial function.

Ex-Vivo Method to Quantifiably Evaluate the Staining Effectiveness of Anterior Lens Capsule Dyes

Purpose

High frequency of cataracts and the requirements of new European Union regulations for medical devices require the availability of preclinical models to adequately evaluate anterior lens capsule dyes before their use in patients. Herein, we describe an ex vivo method to quantifiably evaluate the macroscopic and microscopic staining effectiveness of anterior lens capsule dyes using porcine eyes.

Methods

Commercially available trypan blue–based products or physiological saline solution (negative control) was injected into porcine eyes. Anterior pole and lens (after extraction) were macroscopically photographed, and the images were quantitatively analyzed. Lenses were histologically processed, and the staining intensity microscopically was semiquantified.

Results

Macroscopic evaluation of the anterior pole revealed bluish staining of the anterior capsule; however, this coloring cannot be macroscopically discerned after lens extraction. Quantitative image analyses showed significant (P < 0.01) staining of the lens capsule compared to the negative control, but not significant (P > 0.05) between the products tested. Quantitative analysis of dying on lens images could not be performed. Microscopic semiquantification of the capsule staining intensity allows us to appreciate differences between products.

Conclusions

The described method is a quick and useful tool for macroscopic evaluation by surgeons to choose an anterior capsule staining for use during everyday surgeries, and a more specific microscopic evaluation also allows us to determine the effectiveness and usefulness of these products.

Translational Relevance

This method satisfies preclinical effectiveness evaluations required by European Union regulations and complements the safety and toxicity evaluations that new products must guarantee before they enter the market and are used in clinical practice.

Diffuse retinal pigment epithelium atrophy following pars plana vitrectomy for high myopic macular hole assisted by Brilliant Blue G: A case report

Purpose

To describe a case of diffuse retinal pigment epithelium (RPE) disturbance following 23-gauge pars plana vitrectomy (PPV) with the inverted internal limiting membrane (ILM) technique and Brilliant Blue staining for a high myopic macular hole (MH).

Observations

A 53-year-old pseudophakic high myopic female was referred to the Vitreoretinal Department with a diagnosis of a full thickness myopic MH of her right eye. Her initial visual acuity was 20/40 of her right eye and 20/20 in the left eye. She underwent routine PPV with inverted ILM flap assisted by repeated brilliant blue staining. Surgery was uneventful without any intraoperative complications. MH closure was obtained within the first days. Three weeks postoperatively, the patient reported a decline in visual acuity of her right eye. Upon examination, her visual acuity decreased to 20/400. Fundus examination showed diffuse pigmentary changes with mottling at the level of the RPE, which later progressed to severe diffuse atrophy, as confirmed by fundus autofluorescence (FAF). After 12 months, visual acuity remained 20/400 with widespread areas of atrophy.

Conclusions

Uncomplicated routinary PPV assisted with Brilliant Blue, can lead to unexplained atrophy of the RPE. Possible causes include light phototoxicity, dye toxicity or both.

A Review on Functionalized Graphene Sensors for Detection of Ammonia

Since the first graphene gas sensor has been reported, functionalized graphene gas sensors have already attracted a lot of research interest due to their potential for high sensitivity, great selectivity, and fast detection of various gases. In this paper, we summarize the recent development and progression of functionalized graphene sensors for ammonia (NH3) detection at room temperature. We review graphene gas sensors functionalized by different materials, including metallic nanoparticles, metal oxides, organic molecules, and conducting polymers. The various sensing mechanism of functionalized graphene gas sensors are explained and compared. Meanwhile, some existing challenges that may hinder the sensor mass production are discussed and several related solutions are proposed. Possible opportunities and perspective applications of the graphene NH3 sensors are also presented.

Intraoperative efficacy and clinical outcomes of two commercial staining solutions used in idiopathic epiretinal membrane surgery

PURPOSE

To compare two commercially available staining solutions (MembraneBlue Dual® by D.O.R.C., Netherlands, and TWIN by AL.CHI.MI.A. S.R.L., Italy), in terms of intraoperative handling, staining efficacy and safety, in eyes undergoing surgery for idiopathic epiretinal membrane (ERM).

METHODS

In this observational cross-sectional study, the performance of the dyes used during the procedure (cohesion, ERM and internal limiting membrane [ILM] staining efficacy) was scored by the surgeon using a customized questionnaire after 10 procedures with each of the two dyes. Best-corrected visual acuity (BCVA), central foveal thickness (CFT), blue-light fundus autofluorescence (BAF), and microperimetry-determined retinal sensitivity were reviewed preoperatively and then at 1 and 3 months after surgery.

RESULTS

ILM staining efficacy with TWIN was scored 2.89 ± 0.33 by the surgeons, which turned out to be higher than with MembraneBlue Dual® (1.90 ± 0.31, P = 0.0002). The cohesion score was 2.70 ± 0.48 for TWIN and resulted significantly higher than with MembraneBlue Dual® (1.60 ± 0.51, P = 0.0010). BCVA, CFT and retinal sensitivity were similar in the two groups, 1 and 3 months postoperatively (P nonsignificant for all).

CONCLUSIONS

Both TWIN and MembraneBlue Dual® dyes showed suitable staining properties and equivalent safety and efficacy profiles, both intra- and postoperatively. The TWIN dye might offer a solution for surgeons who prefer a more cohesive and stable dye.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Infracyanine Green vs. Brilliant Blue G in Inverted Flap Surgery for Large Macular Holes: A Long-Term Swept-Source OCT Analysis

Background and Objectives: To compare the long-term toxicity of infracyanine green (IFCG) to brilliant blue G (BBG) in inverted internal limiting membrane flap surgery (I-ILMFS) for large, full-thickness macular holes (FTMHs). Materials and Methods: Prospective randomized study including 39 eyes with ≥ 400 µm idiopathic FTMH who underwent I-ILMFS with either IFCG or BBG. Postoperative 6- and 12-month corrected distance visual acuity (CDVA), closure rate, and swept-source optical coherence tomography parameters, including ellipsoid zone (EZ) and external limiting membrane (ELM) mean defect length, central foveal thicknesses (CFT), parafoveal macular thickness (MT), ganglion cells and inner plexiform layer (GCL++) thickness, and peripapillary nerve fiber layer (pRNFL) thickness, were compared. Results: Nineteen eyes were included in the IFCG group and 20 eyes in the BBG group. In all cases a FTMH closure was found. CDVA improved at 6 and 12 months in both groups (p < 0.0005); the increase at 12 months was greater in the BBG group (p = 0.036). EZ and ELM defects did not differ between groups at either follow-up time. CFT at 12 months was greater in the BBG group (p = 0.041). A 12-months compared to 6-months MT decrease was present in both groups (p < 0.01). The GCL++ superior inner sector was thicker in the BBG group at 12 months (p = 0.036), as were the superior outer sector (p = 0.039 and p = 0.027 at 6 and 12 months, respectively) and inferior outer sector (p = 0.011 and p = 0.009 at 6 and 12 months, respectively). Conclusion: In our study BBG in I-ILMFS exhibits better long-term CDVA and retinal thickness than does IFCG, suggesting a lesser toxicity from BBG. These findings support the use of BBG over IFCG in I-ILMFS.

Effects of four food dyes on development of three model species, Cucumis sativus, Artemia salina and Danio rerio: Assessment of potential risk for the environment

Food dyes, or color additives, are chemicals added to industrial food products and in domestic cooking to improve the perceived flavor and attractiveness. Of natural and synthetic origin, their safety has been long discussed, and concern for human safety is now clearly manifested by warnings added on products labels. Limited attention, however, has been dedicated to the effects of these compounds on aquatic flora and fauna. For this reason, the toxicity of four different commercially available food dyes (cochineal red E120, Ponceau red E124, tartrazine yellow E102 and blue Patent E131) was assessed on three different model organisms, namely Cucumis sativus, Artemia salina and Danio rerio that occupy diverse positions in the trophic pyramid. The evidence collected indicates that food dyes may target several organs and functions, depending on the species. C. sativus rate of germination was increased by E102, while root/shoot ratio was ∼20% reduced by E102, E120 and E124, seed total chlorophylls and carotenoids were 15-20% increased by E120 and 131, and total antioxidant activity was ∼25% reduced by all dyes. Mortality and low mobility of A. salina nauplii were increased by up to 50% in presence of E124, E102 and E131, while the nauplii phototactic response was significantly altered by E102, E120 and E124. Two to four-fold increases in the hatching percentages at 48 h were induced by E124, E102 and E131 on D. rerio, associated with the occurrence of 20% of embryos showing developmental defects. These results demonstrated that the food dyes examined are far from being safe for the aquatic organisms as well as land organisms exposed during watering with contaminated water. The overall information obtained gives a realistic snapshot of the potential pollution risk exerted by food dyes and of the different organism' ability to overcome the stress induced by contamination.

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.

New Vital Dye Injection Technique With Vitrectomy Probe

BACKGROUND AND OBJECTIVE

To evaluate a new, safer way to inject vital dye during chromovitrectomy for dye-assisted macular peeling.

PATIENTS AND METHODS

Prospective consecutive case series. Enrolled patients underwent macular surgery with a new technique of staining the epiretinal membrane and the internal limiting membrane with vital dyes. Twenty eyes of 20 patients (eight men, 12 women) were affected by idiopathic epiretinal membrane and underwent 25-gauge via pars plana vitrectomy for epiretinal membrane removal. Ten eyes were stained with Membrane Blue-Dual (Brilliant Blue G + trypan blue; DORC, Zuidland, The Netherlands) and 10 eyes were stained with Brilliant Peel (Brillant Blue G; Fluoron GmbH, Ulm, Germany). Preoperatively and postoperatively (1, 3, and 6 months) all patients received a complete ophthalmologic examination with best-corrected visual acuity (BCVA) assessment, swept-source optical coherence tomography, and multifocal electroretinography (mfERG).

RESULTS

The mean age of the patients was 67.0 years ± 8.6 years (range: 55 years to 78 years). No statistically significant difference in BCVA improvement or central foveal thickness decrease was observed in either group (P > .05). The mfERG showed an increase in electrical response densities 3 months after surgery.

CONCLUSION

The authors describe a new technique to inject vital dye during chromovitrectomy for dye-assisted macular peeling that may help to improve the overall safety of macular surgery. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:528-533.].

Photodynamic Therapy Using Indocyanine Green Loaded on Super Carbonate Apatite as Minimally Invasive Cancer Treatment

Minimally invasive treatment is getting more and more important in an aging society. The purpose of this study was to explore the possibility of ICG loaded on super carbonate apatite (sCA) nanoparticles as a novel photodynamic therapy (PDT) against cancers. Using colon cancer cells, ICG uptake and anti-tumor effects were examined between the treatments of ICG and sCA-ICG. Reactive oxygen species (ROS) production and temperature rise were also evaluated to explore the underlying mechanism. Atomic force microscopy revealed that the size of sCA-ICG ranged from 10 to 20 nm. In aqueous solution with 0.5% albumin, the temperature increase after laser irradiation was 27.1°C and 23.1°C in sCA-ICG and ICG, respectively (control DW: 5.7°C). A significant increase in ROS generation was noted in cell cultures treated with sCA-ICG plus irradiation compared with those treated with ICG plus irradiation (P < 0.01). Uptake of ICG in the tumor cells significantly increased in sCA-ICG compared with ICG in vitro and in vivo The fluorescence signals of ICG in the tumor, liver, and kidney faded away in both treatments by 24 hours. Finally, the HT29 tumors treated with sCA-ICG followed by irradiation exhibited drastic tumor growth retardation (P < 0.01), whereas irradiation of tumors after injection of ICG did not inhibit tumor growth. This study shows that sCA is a useful vehicle for ICG-based PDT. Quick withdrawal of ICG from normal organs is unique to sCA-ICG and contrasts with the other nanoparticles remaining in normal organs for a long time. Mol Cancer Ther; 17(7); 1613-22. ©2018 AACR.

Photochemical degradation of trypan blue

Purpose

To investigate the photochemical degradation of trypan blue (TB) and to identify decomposition products.

Methods

Defined solution samples of TB and a mixture with lutein/zeaxanthin were exposed to blue light. Thermal degradation processes were ruled out using controls not subjected to irradiation. All samples were analyzed using optical microscopy, UV/Vis spectroscopy, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and nuclear magnetic resonance (NMR) spectrometry. Degradation kinetics were determined based on changes in absorbance; intermediates were identified by analyzing mass differences of characteristic fragment ion peaks within the fragmentation patterns, and assignments were verified by NMR.

Results

TB demonstrated a photochemical degradation, which can be triggered by lutein/zeaxanthin. Intermediates vary depending on the presence of lutein/zeaxanthin. The self-sensitized photodegradation of TB occurs under generation of dimethyl sulfate and presumed formation of phenol. In contrast, within the presence of lutein/zeaxanthin the decomposition of TB indicates the formation of methoxyamine and sulfonyl arin. Thermal degradation processes were not observed.

Conclusions

TB demonstrated a photodegradation that may be triggered by lutein/zeaxanthin and results in the formation of cytotoxic decomposition products. Our findings contribute to understand degradation mechanisms of TB and may elucidate previous clinical and experimental observations of cellular toxicity after TB application.

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

PURPOSE

To compare, for the first time, systematically the toxicity and phototoxicity of dyes and dye combinations used in vitreoretinal surgery. The dyes were trypan blue, brilliant blue G, trypan blue + brilliant blue G, indocyanine green, bromophenol blue, bromophenol blue + brilliant blue G, and acid violet 17, in clinically used concentrations.

METHODS

Human ARPE retinal pigment epithelium cells were exposed to the dyes for 30 min. For phototoxicity, the cells were exposed for 15 min to high-intensity light from a light emitting diode source with an intensity similar to surgical conditions. Toxicity was assayed either directly after exposure to either dye alone or dye and light, or with a delay of 24 h.

RESULTS

None of the dyes or their combinations was toxic when cells were exposed to them at ambient light. Acid violet led to a reduction viability by 90% already immediately after light exposure. Bromophenol blue and its combination with brilliant blue G showed strong phototoxicity (reduction of viability by 83%) when assayed with delay. Indocyanine green with different agents to adjust osmolarity (balanced salt solution, glucose, and mannitol) was not found to be toxic.

CONCLUSION

The strong immediate phototoxicity of acid violet reflects its clinical toxicity. Bromophenol blue might also be disadvantageous for patient outcome because of its delayed phototoxicity. The other dyes (trypan blue, brilliant blue g, and indocyanine green) were not found to be toxic neither with exposure to ambient light nor after exposure to light of intensities used in surgery.

Impact of Vital Dyes on Cell Viability and Transduction Efficiency of AAV Vectors Used in Retinal Gene Therapy Surgery: An In Vitro and In Vivo Analysis

Purpose

Treatment of inherited retinal degenerations using adeno-associated viral (AAV) vectors involves delivery by subretinal injection. In the latter stages, alteration of normal anatomy may cause difficulty in visualizing the retinotomy, retinal detachment extension, and vector diffusion. Vital dyes may be useful surgical adjuncts, but their safety and impact on AAV transduction are largely unknown.

Methods

The effects of Sodium Fluorescein (SF), Membrane Blue (MB), and Membrane Blue Dual (DB) at a range of dilutions were assessed on human embryonic kidney cells in vitro using an AAV2-green fluorescent protein (GFP) reporter at different multiplicities of infection. Flow cytometry analysis was performed to assess both cell viability and transduction efficiency. The effect on quantitative (q)PCR titer was determined. Balanced salt solution (BSS) or dilute DB (1:5 in BSS) were delivered subretinally into left/right eyes of C57BL/6J mice (n = 12). Retinal structure and function were analyzed by optical coherence tomography, autofluorescence, dark-and light-adapted full-field electroretinography.

Results

DB and MB were not toxic at any concentration tested, SF only when undiluted. The presence of dyes did not adversely affect the genomic titer. DB even increased the values, due to presence of surfactant in the formulation. AAV2-GFP transduction efficiency was not reduced by the dyes. No structural and functional toxic effects were observed following subretinal delivery of DB.

Conclusions

Only undiluted SF affected cell viability. No effects on qPCR titer and transduction efficiency were observed. DB does not appear toxic when delivered subretinally and improves titer accuracy. DB may therefore be a safe and helpful adjunct during gene therapy surgery.

Translational Relevance

This paper might be of interest to the retinal gene therapy community: it is a “bench to bedside” research paper about the potential use of dyes as a surgical adjunct during the gene therapy surgery. We have tested the potential toxicity and impact on transduction efficiency in an in vitro and in vivo model.

Differential autophagic effects of vital dyes in retinal pigment epithelial ARPE-19 and photoreceptor 661W cells

Indocyanine green (ICG) and brilliant blue G (BBG) are commonly used vital dyes to remove internal limiting membrane (ILM) in vitreoretinal surgery. The vital dyes have shown cytotoxic effects in ocular cells. Autophagy is a stress responsive pathway for either protecting cells or promoting cell death. However, the role of autophagy in ocular cells in response to the vital dyes remains unknown. In this study, we found that ICG and BBG reduced cell viability in both human retinal pigment epithelial ARPE-19 and mouse photoreceptor 661W cells. ICG and BBG induced lipidated GFP-LC3-II and LC3-II in ARPE-19 and 661W cells. Combination treatment with the autophagy inhibitor chloroquine indicated that ICG and BBG reduced autophagic flux in ARPE-19 cells, whereas the vital dyes induced autophagic flux in 661W cells. Moreover, genetic and pharmacological ablation of autophagy enhanced vital dyes-induced cytotoxicity in ocular cells. Dietary supplements, including resveratrol, lutein, and CoQ10, induced autophagy and diminished the cytotoxic effects of ICG and BBG in ocular cells. These results suggest that autophagy may protect ARPE-19 and 661W cells from vital dyes-induced damage.

Ophthalmic use of blood-derived products

There is a wide spectrum of blood-derived products that have been used in many different medical and surgical specialties with success. Blood-derived products for clinical use can be extracted from autologous or allogeneic specimens of blood, but recombinant products are also commonly used. A number of blood derivatives have been used for a wide range of ocular conditions, from the ocular surface to the retina. With stringent preparation guidelines, the potential risk of transmission of blood-borne diseases is minimized. We review blood-derived products and how they are improving the management of ocular disease.

A near-IR uncaging strategy based on cyanine photochemistry

The development of photocaging groups activated by near-IR light would enable new approaches for basic research and allow for spatial and temporal control of drug delivery. Here we report a near-IR light-initiated uncaging reaction sequence based on readily synthesized C4′-dialkylamine-substituted heptamethine cyanines. Phenol-containing small molecules are uncaged through sequential release of the C4′-amine and intramolecular cyclization. The release sequence is initiated by a previously unexploited photochemical reaction of the cyanine fluorophore scaffold. The uncaging process is compatible with biological milieu and is initiated with low intensity 690 nm light. We show that cell viability can be inhibited through light-dependent release of the estrogen receptor antagonist, 4-hydroxycyclofen. In addition, through uncaging of the same compound, gene expression is controlled with near-IR light in a ligand-dependent CreER^T/LoxP-reporter cell line derived from transgenic mice. These studies provide a chemical foundation that we expect will enable specific delivery of small molecules using cytocompatible, tissue penetrant near-IR light.

Evaluation of macular retinal ganglion cell-inner plexiform layer thickness after vitrectomy with internal limiting membrane peeling for idiopathic macular holes

PURPOSE

To evaluate macular retinal ganglion cell-inner plexiform layer (GCIPL) thickness changes after Brilliant Blue G-assisted internal limiting membrane peeling for idiopathic macular hole repair using a high-resolution spectral-domain optical coherence tomography (SD-OCT).

METHODS

32 eyes from 32 patients with idiopathic macular holes who underwent vitrectomy with internal limiting membrane peeling between January 2011 and July 2012 were retrospectively analyzed. GCIPL thickness was measured before surgery, and at one month and at six months after surgery. Values obtained from automated and semimanual SD-OCT segmentation analysis were compared (Cirrus HD-OCT, Carl Zeiss Meditec, Dublin, CA).

RESULTS

No significant differences were found between average GCIPL thickness values between preoperative and postoperative analysis. However, statistical significant differences were found in GCIPL thickness at the temporal macular quadrants at six months after surgery. Quality measurement analysis performed by automated segmentation revealed a significant number of segmentation errors. Semimanual segmentation slightly improved the quality of the results.

CONCLUSION

SD-OCT analysis of GCIPL thickness found a significant reduction at the temporal macular quadrants at 6 months after Brilliant Blue G-assisted internal limiting membrane peeling for idiopathic macular hole.

A preliminary study of Heavy Brilliant Blue G for internal limiting membrane staining in macular hole surgery

Context:

Surgical outcomes of vitrectomy for idiopathic macular hole using a “heavy” Brilliant Blue G (HBBG) solution for staining and removal of the internal limiting membrane (ILM).

Settings and Design:

Prospective interventional case series conducted in a tertiary eye care hospital.

Materials and Methods:

Nineteen patients (20 eyes) with idiopathic macular hole were enrolled to undergo vitrectomy with ILM peeling using HBBG. BBG dye was made heavy by mixing with 10% dextrose normal saline (DNS) solution in 2:1 ratio. The adequacy of ILM staining was noted intraoperatively. The closure rates of macular hole and visual improvement were recorded. Patients were followed up postoperatively on day 1, week 1, and subsequently at 1, 3, and 6 months, and every 6th month thereafter.

Statistical Analysis:

Wilcoxon signed-rank test was used; P < 0.05 was considered significant.

Results:

Preoperative best-corrected visual acuity (BCVA) ranged from 20/1000 to 20/63 (median: 20/100). Intraoperatively, the ILM stained very well in all eyes, and was easily removed. All macular holes closed postoperatively. The mean follow-up was 6.15 ± 2 months (range: 4-10; median: 6 months). Final BCVA ranged from 20/20 to 20/80 (median: 20/40), amounting to a significant visual improvement (P = 0.0001). BCVA improved by 1-8 Snellen lines in 19 eyes (95%); 16 eyes (80%) improved by ≥2 lines; 13 eyes (65%) achieved a final BCVA of 20/40 or better.

Conclusions:

Addition of 10% DNS to BBG dye allowed good ILM staining with less dye during macular hole surgery, and provided excellent anatomic and visual outcomes.

Chromovitrectomy: update

The basic concept for the application of vital dyes during vitreoretinal surgery is to assist in highlighting preretinal membranes and tissues which are very thin and semitransparent and thus difficult to detect. The vital dyes may be classified according to different criteria, where the most commonly applied includes chemical classification. In ophthalmic surgery, vital dyes are widely used in cataract and vitreoretinal surgery. The vital dyes, indocyanine green, infracyanine green, and brilliant blue stain the internal limiting membrane, and trypan blue and triamcinolone acetonide help to visualize epiretinal membranes and vitreous, respectively. This review exhibits the current literature regarding the properties of vital dyes, techniques of application, indications, and toxicities during vitreoretinal surgery and, also suggests that the field of chromovitrectomy represents an expanding area of research.

The retinal biocompatibility of dyes in the ex vivo model of the isolated superfused vertebrate retina

BACKGROUND

Peeling of the internal limiting membrane or epiretinal membranes is a successful principle in macular surgery to achieve a functional benefit. Different dyes are used to facilitate the identification of intraocular tissues. The aim of our work was to investigate the retinal tolerance to the different dyes and their solvent carriers to provide valuable data for surgeons in handling for an optimal intraoperative use.

METHODS

Using the ex vivo model of the isolated superfused vertebrate retina technique, the effects of the dyes were tested on human and bovine retinal function. The retinas were perfused with an oxygen preequilibrated standard solution. The electroretinogram (ERG) was recorded using Ag/AgCl electrodes. After recording stable ERG amplitudes, the dyes brilliant blue G, indocyanine green, trypan blue, patent blue, triamcinolone and their solvent carriers were investigated.

RESULTS

Reductions of the ERG amplitudes were found for each tested dye. The effects after application of the dyes were dependent on time and concentration of the applied dyes, which were different for each dye.

CONCLUSION

In part, the ERG has shown strong effects already after a short period of dye application. Surgeons who rely on the intraocular use of the dyes should keep in mind our findings, and the use of some dyes should be limited to selected cases. The well-considered use of the dyes by the surgeons could lead to a better functional outcome and avoid a possible harmful outcome of the surgery after mishandling.

Dyes for Eyes™: hydrodynamics, biocompatibility and efficacy of 'heavy' (dual) dyes for chromovitrectomy

As epiretinal membranes (ERMs), the internal limiting membrane (ILM) and the vitreous cortex are essentially transparent tissues, or translucent structures, nontraumatic removal may be challenging in various types of macular surgery. Vital dyes stain these thin tissues, thus allowing for better visualization of these structures during vitrectomy and selective 'membrane peeling' from the underlying retina. To avoid swirling of the dye within the fluid-filled vitreous cavity, and to better target the dye onto the macula, a fluid-air exchange is commonly performed. However, this may jeopardize visualization of the macula during peeling due to clouding of the posterior lens capsule, and may lead to postoperative visual field defects. Recently, a new dye solution for staining the ERM and ILM simultaneously has been developed that circumvents the need for fluid-air exchange, i.e. MembraneBlue-Dual™. This paper will focus on the hydrodynamics and biocompatibility of this 'heavy' dual dye and its efficacy for staining of the ILM and/or ERMs during posterior segment surgery in a multicenter clinical setting.

Staining properties of brilliant blue depending on different incubation times and solvents in humans

PURPOSE

Intravitreous injection of vital dyes, e.g. brilliant blue (BBG), promotes better visualization of the internal limiting membrane (ILM). This paper investigates the staining properties of BBG depending on different incubation times and 2 types of solvents--5% glucose (GL) or saline solution--in a prospective study in patients.

METHODS

This paper investigates various aspects of BBG in various methods. An interventional prospective study was conducted in patients to examine the binding properties of the blue dye diluted in either saline or 5% GL to epiretinal membranes (ERMs) and ILMs. Forty-nine consecutive patients older than 18 years scheduled for macular ERM, vitreomacular traction and macular hole surgeries were prospectively recruited. The primary outcomes of this study were the degree of ILM and ERM staining. The secondary outcomes of the study were the need of reinjection of BBG or any other dye, the ability of BBG to stain the vitreous, and frequency of complications. The staining of the ILM and ERM were graded as no staining, little, moderate or strong staining.

RESULTS

There was no correlation between age (p = 0.32) or gender (p = 0.33) in the staining affinity of BBG to either the ILM or ERM. BBG may be an appropriate staining agent for the ILM in the majority (82%) of surgeries; however, in approximately half of the cases (45%) surgeons considered BBG not enough for ERM coloring and visualization. There is a tendency of BBG to stain the ILM better when saline solution is used compared to GL 5%; however, this was not statistically significant (p = 0.64). There was no difference in the staining efficacy of BBG to the ERMs by either solution (p = 0.70), despite the low staining affinity.

CONCLUSION

BBG became the state-of-the-art dye for ILM identification. Differences in staining properties may imply that BBG should not be considered as first-line stain for ERM surgery. BBG is effective in ILM staining in over 80% of macular hole surgeries.

Brilliant Blue G as protective agent against trypan blue toxicity in human retinal pigment epithelial cells in vitro

BACKGROUND

Combinations of trypan blue (TB), Brilliant Blue G (BBG) and polyethyleneglycol had been shown before to be less toxic to ARPE retinal pigment epithelial cells than TB alone. We studied systematically the influence of combinations of dyes on cell damage.

METHODS

ARPE cells were exposed to TB (concentration range 0.025 to 1 %), BBG (0.0025 to 0.5 %), and combinations of the two dyes, dissolved in phosphate buffered saline (PBS), for periods between 5 and 60 min. Cell damage was monitored with the WST-1 assay. The effect of different salt concentration was measured in the same way.

RESULTS

TB in concentrations of 0.075 % and higher was toxic to the cells already after 30 min incubation. BBG was toxic after 30 min in concentration of 0.1 % and higher, but had a protective effect on cells with incubation time of 5 min and concentrations up to 0.1 %. BBG at concentrations of 0.025 % protected against TB-induced damage at 5 min and 30 min incubation. Salt concentrations between 113 and 225 mM did not influence cell survival even after 30 min. In the presence of TB, propidium iodide bound strongly to the cells.

CONCLUSIONS

BBG acts as a protecting agent against TB toxicity.

Contrast recognizability during brilliant blue G - and heavier-than-water brilliant blue G-assisted chromovitrectomy: a quantitative analysis

PURPOSE

To evaluate the potential of heavier-than-water brilliant blue G (BBG-D(2) 0) to stain the internal limiting membrane (ILM) during chromovitrectomy.

METHODS

In a nonrandomized, prospective, clinical multicentre study, 71 consecutive chromovitrectomy interventions in 71 patients were analysed. During routine 23-gauge vitrectomy, conventional 0.25 mg/ml BBG was employed in 21 and 0.25 mg/ml BBG-D(2) 0 in 50 patients. All interventions were videotaped. Post-operatively, video frames were viewed and dye performance assessed subjectively and objectively. Main outcome measure was the chromaticity difference between the stained ILM and the unstained underlying retina, measured by means of an objective and quantitative analysis method to describe colour contrast strengths as they are perceived by the human eye.

RESULTS

Removal of the ILM was possible in all interventions without additional vital dyes. BBG-D(2) 0 readily sank to the retinal surface, while conventional BBG tended to swirl up throughout the vitreous cavity. Conventional BBG was removed either with active suction or with a flute needle. Brilliant blue G-D(2) 0 needed to be whirled up from the retinal surface with a flute needle before aspiration. Objective chromaticity measurements yielded a mean chromaticity score of 7.98 for BBG-D(2) 0 and 6.51 for BBG (p = 0.09).

CONCLUSIONS

Brilliant blue G-D(2) 0 readily sinks to the retinal surface after injection and can be conveniently removed with a flute needle or active suction during chromovitrectomy. Based on the premises of the chromaticity measurements in this study, BBG's ILM staining capacity was not significantly improved through the recent revision its preparation, although a tendency towards slightly improved contrasts between the ILM and the underlying retina was observed.

The structural effect of intravitreal Brilliant blue G and Indocyanine green in rats eyes

PURPOSE

To compare the potential retinal toxicity of two commercially Brilliant blue G dyes (Brilliant Peel and Ocublue Plus) and Indocyanine green (ICG) at usual clinical concentration.

METHODS

Brilliant Peel 0.025% (n=9), Ocublue Plus 0.025% (n=9), and ICG 0.05% (n=9) were injected intravitreally into Sprague-Dawley rat left eyes with balanced salt solution injected in the contralateral eyes as control. Evaluation of the effect of the dyes on retinal architecture was done by histological analysis of neurosensory retinal thickness and retinal ganglion cell (RGC) counts 7 days after intravitreal injection. Paired t-test was done to detect the presence of biologically significant thinning in neurosensory retina and five retinal layers for each dye (paired t-tests). One-way ANOVA and Tukey's Honestly Significant Difference test were used to assess whether different dyes caused significant thinning in mean neurosensory retinal thickness and reduction of mean RGC density.

RESULTS

Eyes treated with ICG had significantly thinner mean total neurosensory retinal thickness compared with the control eyes (P-value=0.01), followed by those treated with Ocublue Plus (P-value=0.03). Brilliant Peel did not cause significant thinning in any of the five retinal layers (all P-values>0.05). No significant difference in mean thinning of the total retinal thickness was detected between dyes (P-value=0.11). The mean thickness of the photoreceptor outer segment and outer plexiform layers were significantly reduced in ICG-injected eyes when compared with the control eyes (P-value=0.02). No significant difference in mean thinning between the three dyes was detected at all five retinal layers using one-way ANOVA (all P-values>0.35). RGC density was significantly reduced for ICG (P-value=0.01) but only marginally for Ocublue Plus (P-value=0.05). No significant reduction in RGC density was observed for Brilliant Peel (P-value=0.2).

CONCLUSION

Intravitreal Brilliant Peel is safe to rats retina. The retinal thinning and reduction in RGC density induced by Ocublue Plus requires further studies to determine the safety profile of this product. Potential retinal toxicity is seen with ICG 0.05%.

Unanticipated vision loss after pars plana vitrectomy

Although advances in vitreoretinal surgical techniques and technology have helped to minimize the risks associated with surgical manipulation of the retina, retinal pigment epithelium, and optic nerve, unanticipated or unexplained visual loss still occurs. We review causes of vision loss encountered after pars plana vitrectomy, including retinal toxicities, vascular events, and optic neuropathies, and we suggest strategies to limit or prevent them.

Development and preclinical evaluation of a new viewing filter system to control reflection and enhance dye staining during vitrectomy

PURPOSE

We developed a new artificial image enhancement system and evaluated its usefulness in controlling intraoperative reflection and enhancing of Brilliant Blue G (BBG) staining.

METHODS

The system was composed of three kinds of filters (a polarizing filter, a blue-enhancing filter, and a sharp-cut filter Y) and attached to the inferior surface of the operating microscope. Twenty-seven post-mortem extracted porcine eyes were used for a series of examinations. We performed surgery using the 23G-vitrectomy system with a halogen light and xenon lights and compared the reduction of intraoperative reflection under air condition and visibility and BBG contrast with and without this system. The evaluation of images was calculated in CIE 1976 (L*, a*, b*) color space (CIELAB) carried out by ImageJ software. The transmission of each filter and absorbance of BBG was measured by a spectrophotometer. We measured spectral irradiance at each wavelength about each filter from each light source with a spectroradiometer.

RESULTS

Under both light sources, intraoperative reflection was controlled using a polarizing (PL) filter or combination of filters under air condition. Evaluation of the value of L* within the cutter surface was changed by 37.8 % under the halogen light, and 61.6 % (averaged) under the xenon light with inserted filters versus no filter. The BBG intensity difference was obtained with sharp-cut Y filter under both light source and PL with blue enhancing filter under the halogen light using each L*, a*, b* parameter with statistically significant (p < 0.01, 0.05). However, there was a relative decrease in the observation illuminance when the filter inserted according to the attenuation total spectral irradiance.

CONCLUSIONS

This system can reduce intraoperative reflections under the air condition and obtain an excellent BBG staining intensity induced by various light sources.

Ultrastructure of the membrana limitans interna after dye-assisted membrane peeling

The purpose of this study was to investigate the ultrastructure of the membrana limitans interna (internal limiting membrane, ILM) and to evaluate alterations to the retinal cell layers after membrane peeling with vital dyes. Twenty-five patients (25 eyes) who underwent macular hole surgery were included, whereby 12 indocyanine green (ICG)- and 13 brilliant blue G (BBG)-stained ILM were analyzed using light, transmission electron and scanning electron microscopy. Retinal cell fragments on the ILM were identified in both groups using immunohistochemistry. Comparing ICG- and BBG-stained membranes, larger cellular fragments were observed at a higher frequency in the BBG group. Thereby, the findings indicate that ICG permits an enhanced separation of the ILM from the underlying retina with less mechanical destruction. A possible explanation might be seen in the known photosensitivity of ICG, which induces a stiffening and shrinkage of the ILM but also generates retinal toxic metabolites.