Acute retinal toxicity associated with a mixture of perfluorooctane and perfluorohexyloctane: failure of another indirect cytotoxicity analysis

A minimum specification dataset for liquid ocular endotamponades: recommendations by a European expert panel

PURPOSE

To propose a minimum specification dataset to characterize liquid ocular endotamponades (OEs), namely silicone oil (SO), heavy SO (HSO), perfluorodecalin (PFD), and perfluoro-octane (PFO), in terms of physicochemical properties, purity and available evidence of safety, in line with ISO16672:2020.

METHODS

An evidence-based consensus using the expert panel technique was conducted. Two facilitators led a committee of 11 European experts. Facilitators prepared a dataset for each compound including the list of specifications relevant for the safety, identified by the group members on the basis of expertise and a comprehensive literature review. Each item was ranked by each member using a 9-point scale from 1 "absolutely to not include" to 9 "absolutely to include" in two rounds followed by discussion. Only items reaching consensus (score ≥ 7 from ≥ 75% of members) were included in the final datasets.

RESULTS

For all OEs, consensus was reached to include manufacturer, density, refractive index, chemical composition, dynamic viscosity, interfacial and surface tension, endotoxins, in vitro cytotoxicity assessment, and any evidence from ex vivo and/or in vivo tests for safety assessment. Additional specifications were added for SO (molecular weight distribution, content of oligosiloxanes with MW ≤ 1000 g/mol, spectral transmittance) and PFD/PFO (% of pure PFD/PFO in the final product, vapor pressure, chemical analyses performed for safety assessment).

CONCLUSION

The proposed evidence-based minimum specification datasets for SO, HSO, PFD, and PFO have the potential to provide surgeons and health service purchasers with an easily available overview of the most relevant information for the safety assessment of OEs.

Ala®sil chemical characterization and toxicity evaluation: an example of the need for the Medical Device Regulation 2017/745

Introduction: Ala®sil infusion was on the market for clinical use under the Medical Devices Directive (MDD) 93/42/EEC as an irrigating solution based on polydimethylsiloxane (PDMS). The product was withdrawn in 2016, and to the best of our knowledge, it did not cause any health damage. Methods: A bibliographic review and experimental analysis were conducted to evaluate whether this CE-marked product could have been used in patients under the current Medical Device Regulation (MDR) 2017/745. Analytical results from gas chromatography-mass spectrometry (GC-MS) and matrixassisted laser desorption ionization (MALDI) were performed. Citotoxicity studies were also carried out. Results: Only one study related to Ala®sil clinical use was found, describing a pilot series of five patients. The authors rated the product as not helpful in three out of the five cases for internal searching of retinal breaks and in four out of the five cases for drainage of subretinal fluid. No other scientific papers or documentation was found regarding Ala®sil's safety. Nevertheless, the product was introduced in the market after achieving the CE marking. GC-MS and MALDI showed that the polymer has a low molecular weight of 1,000 g/mol. Several linear and cyclic low-molecular-weight components (LMWCs) were identified as impurities ranging from L3 to D8, with a molecular weight below 600 g/mol. The Ala®sil sample was found to be cytotoxic after 24 h of cell culture but non-cytotoxic after 72 h, probably due to the cellular regeneration capacity of an immortalized cell line. Tissular cytotoxicity revealed an increased apoptosis rate but without morphological modifications. Discussion: Although Ala®sil cannot be classified as cytotoxic, this substance appears to increase retinal cell death processes. This study supports the notion that the MDDwas not functioning adequately to ensure the safety of medical devices. However, the current MDR 2017/745 imposes stricter standards to prevent the commercialization of medical devices without high-quality preclinical and clinical information, as well as precise clinical verification for their use, information not available for Ala®sil infusion.

Comparison of Perfluorocarbon Liquids Cytotoxicity Tests: Direct Contact Versus the Test on Liquid Extracts

The purpose of this study is to compare the in vitro cytotoxicity tests according to the ISO 10993-5 (2009) standards using direct contact and the test on liquid extracts of compounds previously identified as possible toxic impurities in perfluorocarbon liquids (PFCLs) for use in vitreoretinal surgery. Compounds including perfluorooctanoic acid (PFOA), 1H-perfluorooctane (1H-PFO), 2H-tridecafluoro-2-methylpentane, 1H,2H-octafluorocyclopentane, and 2H,3H-decafluoropentane were analyzed by ¹⁹F NMR before and after extraction using an aqueous solution and tested by both the direct contact and liquid extract tests in L929, BALB 3T3, and ARPE-12 cells. The concentration that reduced in vitro cell viability by 30%, the cytotoxicity concentration threshold (CC₃₀), was determined for each compound. ¹⁹F NMR spectroscopy confirmed the immiscibility of perfluoro-n-octane (PFO) and 1H-PFO and the solubility of PFOA with the extraction vehicle. The other samples reacted with the extraction vehicle, releasing fluoride ions. Using the direct contact test, the CC₃₀ of PFOA, 1H-PFO, 2H-tridecafluoro-2-methylpentane, 1H,2H-octafluorocyclopentane, and 2H,3H-decafluoropentane corresponded to 48 124, 50, 14, 8035, and 46 ppm, respectively. The method on liquid extracts did not detect cytotoxicity in three out of five tested compounds, and CC₃₀ could not be determined. In conclusion, the in vitro cytotoxicity test by direct contact revealed a positive correlation between cell toxicity and the concentration of the tested substance. Conversely, the test on liquid extracts hardly detected the cytotoxicity of toxic impurities in PFCLs. Thus, only the cytotoxicity test by direct contact, according to ISO 10993-5 (2009), is a sensible and reliable method to detect possible cytotoxic impurities in PFCLs to guarantee patient safety.

Acute intraocular toxicity caused by perfluorocarbon liquids: safety control systems of medical devices

BACKGROUND

Acute retinal toxicity has been demonstrated to be associated with the intraoperative use of perfluorocarbon liquids (PFCLs), especially perfluorooctane (PFO). Recently, several cases of PFO-associated blindness have been reported in Spain, Holland, France, Italy, the Middle East, and South America.

METHODS

As a result, a new ISO guideline (ISO 16672:2020) was drafted, discussed, approved, and released in 2019. This recent ISO16672:2020 guideline recommends performing direct cytotoxicity tests as an option along with chemical analysis to measure PFCL quality (purity and safety).

RESULTS

In this review paper, it has been emphasized why an appropriate biological test, specifically direct exposure of PFCL to live cells, for measuring cytotoxicity must be performed with each PFCL batch along with chemical analysis.

CONCLUSIONS

The paper intends to compile all available information to discuss possible approaches for avoiding adverse clinical cases in future.

Ex vivo evaluation of retinal cytotoxicity after the use of multiple medical devices in pars plana vitrectomy in porcine eyes

This study aimed to evaluate viability of retinal cells after the use of multiple intraoperative devices, namely a vitreal dye (triamcinolone acetonide,TA), a ERM/ILM dye (solution of trypan blue 0.15% and brilliant blue 0.025%), and two intraocular tamponades, namely perfluoro-n-octane, (PFO) and silicone oil (SO 1000 cSt), with minimal and maximal removal of their residues, during a simulated pars plana vitrectomy (PPV) in porcine eyes ex-vivo. The in vitro cytotoxicity of each of these compounds was verified on ARPE-19 cells by direct tests according to the ISO 10993-5 (2009). Pars plana vitrectomy was performed on 25 enucleated porcine eyes divided in five groups according to the following conditions: Group A) No surgery control: eye bulbs were kept at room temperature for 40 min; Group B) Sham surgery: PPV with the sole use of BSS for 40 min; Group C) Cytotoxic control: PPV with BSS infusion (20 min) followed by intravitreal injection of 1H-PFO (contact time: 20 min); Group D) Surgery with residues: PPV with BSS infusion and sequential intravitreal injection of TA, ERM/ILM dye, PFO and SO, with minimal removal of each compound after a specified contact-time (overall duration: 40 min); Group E) Surgery with minimal residues: PPV performed as in group D, but with maximal removal of each compound (overall duration: 40 min). All the experimental procedures were performed at room temperature. Immediately after surgery, the retina was extracted from each eye bulb and samples of 3-mm diameter were prepared. Retinal viability was determined for each sample by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide assay. A cell viability <70% was considered the cytotoxicity threshold. Kruskal-Wallis test was used to evaluate the differences in retinal viability between groups. No cytotoxicity was detected in retinal samples in groups A, B and E. Samples from eye bulbs that had undergone surgery with minimal removal of residues (group D) and cytotoxic controls (group C) showed high retinal cytotoxicity. The tested conditions indicated that the combined use of TA, ERM/ILM dye, PFO and SO during PPV does not affect retinal cells viability if all the devices are properly removed, whereas the cytotoxicity detected in group D may suggest that the presence and accumulation of the residues of the compounds used intraoperatively could negatively impact retinal viability due to a cumulative and/or synergistic cytotoxic effect between them, supporting the crucial role of an optimal removal of the intraoperative medical devices to ensure a safe vitrectomy to the patient.

Toxicity Threshold of Perfluorocarbon Liquids for Intraocular Use: Dose-Response Assessment of In Vitro Cytotoxicity of Possible Contaminants

Purpose

This study assessed the cytotoxicity of the impurities detected in the perfluorooctane (PFO) batches for vitreoretinal surgery that were associated with serious adverse incidents of ocular toxicity, namely, the perfluorooctanoic acid (PFOA), 1H,1H,7H-dodecafluoro-1-heptanol (DFH), 1H-perfluorooctane (1H-PFO), ethylbenzene, anhydrous p-xylene, and perfluoro-2-butyltetrahydrofurane, and two additional substances 1H,1H,1H,2H,2H-perfluorooctane (5H-PFO) and hexafluoro-1,2,3,4-tetrachlorobutane.

Methods

Serial dilutions were tested by in vitro direct contact cytotoxicity test, validated in accordance with the ISO 10993-5:2009 standard using BALB3T3 and ARPE-19 cell lines, after sample application for 24 hours.

Results

Six of the eight tested substances were cytotoxic according to the above-mentioned ISO standard. Anhydrous p-xylene, ethylbenzene, and PFOA were the most cytotoxic impurities as traces 1.55 ppm, 1.06 ppm, and 28.4 ppm reached the cytotoxicity limit, respectively. Hexafluoro-1,2,3,4-tetrachlorobutane, DFH, and 1H-PFO were cytotoxic at 980, 22,500, and 123,000 ppm, respectively. Both 5H-PFO and perfluoro-2-butyltetrahydrofuran were non-cytotoxic at the highest available concentrations (≥970,000 ppm). The dose-response curves allowed to calculate the cytotoxic concentration (CC₃₀) for each tested substance that would reduce 30% of cell viability and corresponding to the cytotoxicity threshold according to ISO 10993-5.

Conclusions

Our study determined the in vitro cytotoxicity of several impurities in PFO associated with serious adverse incidents in retinal surgery patients.

Translational Relevance

Severe cytotoxicity of some impurities previously found in toxic perfluorocarbon liquids was confirmed. The cytotoxicity test validated according to the ISO 10993-5:2009 standard is a sensible and fast method for reliable detection of the cytotoxicity in perfluorocarbon liquids to guarantee maximal safety for the patients.

Current Situation and Challenges in Vitreous Substitutes

Vitreo-retinal disorders constitute a significant portion of treatable ocular diseases. These pathologies often require vitreo-retinal surgery and, as a consequence, the use of vitreous substitutes. Nowadays, the vitreous substitutes that are used in clinical practice are mainly divided into gases (air, SF₆ , C₂ F₆ , C₃ F₈ ) and liquids (perfluorocarbon liquids, silicone oils, and heavy silicone oils). There are specific advantages and drawbacks to each of these, which determine their clinical indications. However, developing the ideal biomaterial for vitreous substitution continues to be one of the most important challenges in ophthalmology, and a multidisciplinary approach is required. In this sense, recent research has focused on the development of biocompatible, biodegradable, and injectable hydrogels (natural, synthetic, and smart), which also act as medium and long-term internal tamponade agents. This comprehensive review aims to cover the main characteristics and indications for use of the extensive range of vitreous substitutes that are currently used in clinical practice, before going on to describe the hydrogels that have been developed recently and which have emerged as promising biomaterials for vitreous substitution.

Intraocular toxicity caused by MEROCTANE perfluorocarbon liquid

Serious intraocular toxicity cases have been reported worldwide after the use of different perfluorocarbon liquids. The current study reports for the first-time the clinical pictures of cases of acute intraocular toxicity caused by MEROCTANE, a perfluoro-octane commercialized by a Turkish company and distributed in many countries. A series of 18 cases from Chile and Spain was retrospectively analysed. To evaluate the impurity profile, a suspicious MEROCTANE sample (lot OCT.01.2013) was analysed by gas chromatography mass spectrometry and compared with a non-suspicious sample of the same commercial perfluoro-octane (lot OCT 722011). Cytotoxicity was tested following a direct-contact method, taking into consideration the high volatility and hydrophobicity of perfluoro-octane and following the ISO 10993 guideline. Cytotoxicity test showed clear cytotoxic effects of the analysed batch (less than 9% of cell viability). Moreover, chemical analysis demonstrated the presence of many contaminants, some highly toxic (acids and alcohols). Perfluorocarbon liquids are useful tools for intraocular surgery but companies and Agencies of Medical Devices must implement measures that guarantee the safety of these products based on both chemical and cytotoxicity analysis for every batch. Medical staff should be encouraged to report any suspected case to their respective National Agencies.

Benchmarking different brands of perfluorocarbon liquids

PURPOSE

To compare the analytical quality characteristics of currently available CE-marked perfluorocarbon liquids (PFCL) applied intraoperatively during vitreoretinal surgery.

METHODS

Twenty-one samples of 8 brands of perfluorooctane (PFO) and 25 samples of 13 brands of perfluorodecalin (PFD) were analysed. Gas chromatography coupled with mass spectroscopy (GC/MS) was used to determine the content of the main product. The amount of reactive and underfluorinated impurities was analysed and expressed as an H-value using fluoride selective potentiometry after a chemical transformation reaction to detect impurities that triggered both acute and latent toxic effects. UV-active substances were determined in order to draw conclusions on the integrity of primary packaging components. Moreover, we controlled for any 1H-PFO contamination in PFO, as it is known to modify PFO's surface characteristics.

RESULTS

Significant differences in the tested products' purity profiles were detected. The PFO batches revealed H-values ranging from < 10 to 1230 ppm and 1H-PFO concentrations ranging from < 1 to 376 ppm. Leachable substances from packaging components cause UV absorption in the 0.1 to > 3 AU range. The PFD batches revealed H-values ranging from < 10 to 70 ppm and leachables from packaging components resulting in absorbances in the 0 AU to 3.2 AU range.

CONCLUSION

The quality characteristics of the analysed PFCL vary significantly, not only among different brands but among batches from the same manufacturer as well. Manufacturers should communicate the purity of their products in an understandable and clear manner. This would require providing a complete certificate of analysis focussing especially on quality characteristics to enable vitreoretinal surgeons to differentiate between the effects from the PFCL itself and those from impurities.

[Toxicity of heavy liquids]

BACKGROUND

Acute toxicity of perfluorocarbon liquids (PFCL) is a relevant problem in retinal surgery due to impurities in the medicinal product.

OBJECTIVE

This article gives an overview of the current problems, possible explanations, interactions with other medicinal products and approaches to improved patient safety.

RESULTS

Toxicity is caused by impurities in the raw material but can also be caused by interactions with other medicinal products or drugs. The current test procedures do not ideally represent the ophthalmological application but there are promising activities to set the course for the future.

CONCLUSION

The use of PFCL in retinal surgery is generally considered safe. Users should pay attention to the quality of medicinal products.