Silicone Oil Research Articles

Argentinian Flag Sign during Cataract Surgery: Case Reports

Purpose Three case reports involving the Argentinian Flag Sign (AFS) during cataract surgery are presented in this paper with a discussion of the relevance to patients with a history of vitrectomy and silicone oil usage. Insights into the management of cases with similar complications, including surgical strategies, intraoperative findings, and post-surgical outcomes, are offered. Case Presentations Cases 1, 2, and 3 involved a 47-year-old female, a 26-year-old female, and a 57-year-old male, all of whom had a history of retinal detachment, vitrectomy, and silicone oil use. The AFS was observed during cataract surgery in all patients. Intraocular Lens (IOL) implantation was successfully achieved and visual acuity improved in all cases. Conclusion The observation of AFS is more common in younger patients and those with a history of vitreoretinal surgery, and poses surgical challenges to avoid significant impact on postoperative visual acuity. Appropriate preoperative assessment to inform the choice of surgical technique is vital to ensure successful outcomes. Stable anterior chamber pressure should be maintained and the emulsified cortex must be carefully removed. Individualized adjustment of fluid dynamics is required to minimize the risk of radial tearing of the anterior capsule. In conclusion, favorable outcomes may be achieved despite the appearance of the AFS during cataract surgery.

Characteristics and surgical outcomes of giant retinal tear associated rhegmatogenous retinal detachment

Giant retinal tear-associated rhegmatogenous retinal detachment (GRT–RRD) presents a significant surgical challenge. Trauma stands out as one of the risk factors. This retrospective case series aims to assess the outcomes of GRT–RRD patients treated with pars plana vitrectomy (PPV), distinguishing between non-trauma and blunt ocular trauma cases. The medical records and relevant retinal imaging of 60 GRT–RRD patients undergoing PPV and followed with a mean (SD) of 21.2 (13.4) months were reviewed (47 were non-trauma-related and 13 were trauma-related). Both the non-trauma and trauma groups exhibited comparable distribution of proliferative vitreoretinopathy grade (P = 0.067). Following the primary operation, there was no statistically significant difference in the proportion of patients achieving single surgery anatomical success between the non-trauma group (27/47 patients, 57.5%) and the trauma-related group (9/13 patients, 69.2%) (P = 0.534). At the final follow-up, 17 patients remained tamponade with silicone oil. Among the remaining 43 patients, 33/34 patients (97.1%) in the non-trauma group and 9/9 patients (100%) in the non-trauma group (P = 0.661) achieved comparable final surgical anatomical success. Additionally the final vision was comparable between the two trauma categories (Snellen equivalent of 20/125 for the non-trauma group and 20/200 for the trauma group, P = 0.331). In multivariable regression, no significant factors related to primary reattachment rate or final vision were identified. Non-penetrating ocular trauma did not emerge as a significant risk factor for recurrent detachment post-surgery. This study supports that PPV outcomes in GRT–RRD patients are unaffected by the ocular trauma association and reports the effectiveness of PPV in managing these patients.

Demystifying the role of magnetic resonance in identifying intraocular foreign bodies: a case of ocular siderosis

BackgroundOcular siderosis (OS) is a significant cause of visual loss due to retained ferrous intraocular foreign bodies (IOFB). Despite its rarity, OS can lead to severe visual impairment if not promptly diagnosed and treated. This case is notable due to the occult nature of the IOFB, which was undetected by standard imaging modalities, emphasizing the critical role of magnetic resonance imaging (MRI) in such scenarios.Case presentationA 51-year-old Caucasian male presented with progressive vision loss in his right eye over 20 days. Best corrected visual acuity (BCVA) was 20/1000 in the right eye and 20/20 in the left eye. Intraocular pressure (IOP) was 9 mmHg in both eyes. Slit-lamp examination revealed a small linear corneal wound and an iris defect in the right eye, along with a cataract featuring brownish deposits on the anterior capsule. The left eye was normal. Fundus examination of the right eye was hindered by media opacities. Ultrasonography showed a flat retina and choroid with no detectable IOFB. Despite a strong clinical suspicion of OS, computed tomography (CT) did not detect any IOFB. MRI subsequently identified an artifact in the inferior sectors of the right eye, indicative of a metallic IOFB. Surgical intervention involved a 23-gauge vitrectomy, phacoemulsification, IOFB removal and silicon oil (SO) tamponade resulting in a fully restored VA of 20/20 and normal IOP one month post-operation. SO was removed 2 months later. The retina remained adherent with no PVR development, and optical coherence tomography (OCT) scans showed a normal macula.ConclusionsThis case underscores the importance of considering OS in patients with unexplained vision loss and history of ocular trauma, even when initial imaging fails to detect an IOFB. MRI proved crucial in identifying the IOFB, highlighting its value in the diagnostic process. Early detection and surgical removal of IOFBs are essential to prevent irreversible visual damage. This case demonstrates that MRI should be employed when CT and ultrasonography are inconclusive, ensuring accurate diagnosis and timely intervention to preserve vision.

Three-Dimensional Quantitative Analysis of Internal Limiting Membrane Peeling Related Structural Changes in Retinal Detachment Repair

PurposeTo assess macular microstructural changes associated with internal limiting membrane peeling (ILMP) using three-dimensional optical coherence tomography (3D-OCT) in primary macula-off rhegmatogenous retinal detachment (RRD) repairs with vitrectomy and silicone oil (SO) tamponade. DesignRetrospective, consecutive, interventional case series. MethodsSetting: Institutional practice. Patient Population: Patients who received primary RRD repair by a single experienced surgeon between January 2017 and December 2021. Main Outcome Measures: In the qualitative comparative analysis, the presence of macular changes among patients who underwent primary RRD repair with (21 eyes) or without ILMP (20 eyes) were observed. Subsequently, a detailed quantitative analysis of ILMP-related microstructural changes in 56 eyes using both 3D and 2D-OCT images were performed. ResultsIn the qualitative comparative analysis, macular microstructural changes were observed in 95% of ILMP eyes and 5% of non-ILMP eyes (p < 0.001). In the quantitative analysis, four major macular microstructural changes were detected: dimple (75%), dissociated nerve fiber layer (DONFL) (55%), ILM peeling edge thinning (IPET) (64%), and temporal macular groove (TMG) (23%). Dimples (n = 251, average 4.5 ± 5.8 per eye) could be further classified into type I (confined to the inner plexiform layer [IPL]; 73%) and type II (beyond IPL, 27%). The average depth of the deepest dimples was 58 ± 18 μm. The extent of IPET was 6.0 ± 3.7 clock hours. The average length of TMG was 1.8 ± 0.4 mm. Comparing to unoperated fellow eyes, the eyes after ILMP showed decreased inner temporal over nasal retinal thickness ratio (0.86 ± 0.07 versus 0.96 ± 0.03, p < 0.001), shorter disc-fovea distance (4.61 ± 0.32 µm versus 4.78 ± 0.37 µm, p = 0.041), and wider retinal vein trajectories (c’ = 2.48 ± 0.84 versus 3.39 ± 1.61, p = 0.002). ConclusionsMacular microstructural changes are common after ILMP in RRD repair, encompassing both focal changes (dimples, DONFL) and zonal changes (IPET, TMG). DONFL and dimples may be part of a continuum of findings stemming from the same mechanism. IPET and TMG are the results of macular tissue shift due to contracture of the optic disc and neurovascular bundle.

Retinal Toxicity Assessment Following Vitreoretinal Surgery: A Comparison of Silicone Oil and Perfluoropropane Tamponade Using Diopsys® NOVA™

Purpose This study aimed to assess and compare the retinal toxicity associated with silicone oil (SO) and perfluoropropane (C3F8) tamponade following vitreoretinal surgery for fresh rhegmatogenous retinal detachment (RRD), utilizing the office-based Diopsys® NOVA™ system for evaluation. Methods Patients who underwent vitreoretinal surgery for fresh RRD and had SO (group 1) or C3F8 (group 2) tamponade were included in a prospective analysis. Flicker full field electroretinography (ffERG) and pattern electroretinography (PERG) tests were performed at 6 months postoperatively. Results Postoperative best corrected visual acuity (logMAR) was significantly different in group 1 and group 2 patients, 0.48 ± 0.3 and 0.30 ± 0.2, respectively. No significant disparities were found in demographic variables. Flicker ffERG and PERG recordings revealed notable alterations in retinal function parameters in the group 1 compared to the group 2. Conclusion Our findings suggest a correlation between SO tamponade and retinal dysfunction, evidenced by office-based ERG measurements. The Diopsys® NOVA™ protocol offers clinical ease in assessing retinal function. Further controlled studies are essential to validate these findings and guide clinical practice effectively.

Case Study: Compatibility Testing of Pre-Filled Syringe Stopper Technology with Vaporized Hydrogen Peroxide Terminal Sterilization Process.

STERIS and W.L. GORE collaborated on a case study testing the compatibility of a new prefilled syringe plunger design with VHP terminal sterilization. VHP chamber conditions require deep vacuum pulsing, which may represent challenges to prefilled syringe container integrity. The growing industry trend toward VHP sterilization is driven by the FDA search for alternative sterilization methods to EO and the recent publication of a VHP specific process standard. The purpose of the study is to test and report compatibility of the new 0.5 mL GORE IMPROJECT plunger, a silicone free syringe solution for ophthalmic application, with VHP sterilization. Various challenges have been reported when using conventional, siliconized, prefilled syringe systems for intravitreal injections such as subvisible particles, inflammation, silicone floaters, and intraocular pressure increases. The GORE plunger eliminates the need for silicone oil as a lubricant on the plunger and barrel, while meeting strict container closure and terminal sterilization requirements of ophthalmic applications. This case study presents successful results of deep vacuum VHP terminal sterilization process compatibility with the GORE plunger design and material composition. Test results include primary container integrity, stopper off-gassing/ingress, and visual inspection. Principles of VHP vacuum sterilization process, test cycle configuration, and its main parameters are presented.

Relatively low temperature defluorination and carbon coating in CFx by dimethyl silicone oil/polyethylene glycol for enhancing performance of lithium primary battery

Because of the presence of electrochemically inactive C-F2 bond and poor electronic conductivity of C-F, the discharge performance of lithium fluorocarbon (Li/CFx) batteries is limited, despite their extensive use in commercial fields. In this study, dimethyl silicone oil/polyethylene glycol was adopted to improve the performance of CFx through relatively low temperature (350 °C) defluorination and carbon coating. The uniform mixing of dimethyl silicone oil with CFx and the subsequent gas–solid reaction enables mild defluorination, transforming C-F2 into semi-ionic C-F with high conductivity. Furthermore, this dimethyl silicone oil/ polyethylene glycol treated CFx under 350 °C prevent the thermal decomposition of C-F during both of the defluorination and carbon coating process, resulting in improving the electrical performance and capacity protection of CFx. Specifically, the modified CFx cathode exhibits a 2.7 V discharge platform, a discharge capacity of 859.1 mAh/g and the energy density of 1889.7 Wh kg−1 at 0.01C. This approach allows for large scale adjustments of CFx with excellent performance, making it easy to industrialization.

Prefilled Ophthalmic syringes - New Possibilities in Terminal Sterilization.

In a joint study carried out by Gerresheimer, Sterigenics and Früh, it could be shown that also NO2 is well suited to terminally sterilize prefilled ophthalmic syringes. In detail 5 topics were addressed: (1) Compare EtO vs. NO2 penetration into the filled syringe; (2) Analyze gas ingress though 4 different plunger stoppers including silicone oil free and standard rubber plungers; (3) Scrutinize gas ingress through 2 different cap designs based on different elastomer properties; (4) Investigate gas permeation through COP plastic barrels compared to glass; (5) Check if the Tyvek®-layer has an influence on either sterilization.Depending on the needs a suitable sterilization method, packaging and syringe type can be suggested to customers.

Real-Time Observation of Protein Aggregation at Liquid-Liquid Interfaces in a Microfluidic Device.

A droplet microfluidic device to capture in real-time protein aggregation at liquid-liquid interfaces is described. In contrast to conventional methods, typically characterized by a lag time between the application of interfacial stress and the measurement of protein aggregation, here protein adsorption, the formation of a viscoelastic protein layer, aggregation, and shedding of protein particles into solution is simultaneously monitored. The device is applied to analyze the stability of antibodyformulations over a wide range of concentrations (1-180mgmL-1) at the silicone oil (SO)-water interface under controlled mechanical deformation. The adsorption onto oil droplets induces the formation of a viscoelastic protein layer on a subsecond timescale, which progressively restricts the relaxation of the droplets within the chip. Upon mechanical rupture, the protein layer releases particles in solution. The rate of particle formation increases strongly with concentration, similar to the bulk viscosity. Concentrations above 120mgmL-1 lead to aggregation in seconds and drastically decrease the mechanical perturbations required to shed protein particles in solution. These results are important for the development of formulations at high-protein concentrations (>100mgmL-1) and indicate that particular attention should be given to interface-induced particle formation in this concentration range. In this context, low-volume microfluidic platforms allow the assessment of protein physical instabilities early in development and represent attractive tools to optimize antibody stability and formulation design consuming limited amounts ofmaterial.

Cesium lead bromide perovskite nanocrystals as fluorescent taggants for detecting fluid leaks

Fluorescence tagging represents a low cost, fast, and reliable method for leak detection in the chemical industry. Here, the use of halide perovskites as fluorescent taggants is demonstrated to detect piping leakages. To this end, cesium lead bromide (CsPbBr3) nanocrystals were synthesized at room temperature and dissolved in silicon oil as a green luminophore (530 ± 5 nm). The resulting system had a photoluminescence quantum yield of 48 ± 2 % while retaining key optical properties (emission linewidth and lifetime) over the timescale required for typical leak detection (2–30 minutes), even under strongly acidic/basic conditions (pH 1–13) and high pressures (up to 7 atm). Crucially, the operating dose of CsPbBr3 required for leak detection is an order of magnitude lower than those used for typical commercial fluorescent taggants (0.03 versus 0.003 oz mL−1). These results strongly suggest the great potential of halide perovskites towards industrial leak detection applications.

Comparative Analysis of Macular and Optic Disc Perfusion Pre and Post Silicone Oil Removal: A Machine Learning Approach.

In the realm of ophthalmic surgeries, silicone oil is often utilized as a tamponade agent for repairing retinal detachments, but it necessitates subsequent removal. This study harnesses the power of machine learning to analyze the macular and optic disc perfusion changes pre and post-silicone oil removal, using Optical Coherence Tomography Angiography (OCTA) data. Building upon the foundational work of prior research, our investigation employs Gaussian Process Regression (GPR) and Long Short-Term Memory (LSTM) networks to create predictive models based on OCTA scans. We conducted a comparative analysis focusing on the flow in the outer retina and vessel density in the deep capillary plexus (superior-hemi and perifovea) to track perfusion changes across different time points. Our findings indicate that while machine learning models predict the flow in the outer retina with reasonable accuracy, predicting the vessel density in the deep capillary plexus (particularly in the superior-hemi and perifovea regions) remains challenging. These results underscore the potential of machine learning to contribute to personalized patient care in ophthalmology, despite the inherent complexities in predicting ocular perfusion changes.

The sealing pressure variance originated from volume of ferrofluids in magnetic fluid seal

To find the relationship between the volume of ferrofluids injected into the sealing gap and the sealing pressure of magnetic fluid seal, a magnetic fluid sealing experimental equipment is well designed. The ferrofluids used in magnetic fluid seal experiments are expertly synthesized silicone oil based ferrofluids, which have a saturated magnetization as high as 31.4 kA/m. The finding of experiments and simulation results indicates that the sealing pressure has a positive relationship with the volume of ferrofluids when the volume is smaller than 0.5 mL. Based on those results, a theoretical model is established. The key factor affecting the sealing pressure is the thickness of liquid sealing barrier L, which is related to the volume of ferrofluids.

Impact of dimensional variability of primary packaging materials on the break-loose and gliding forces of prefilled syringes.

A prefilled syringe (PFS) should be able to be adequately and consistently extruded during injection for optimal safe drug delivery and accurate dosing. To facilitate appropriate break-loose and gliding forces (BLGF) required during injection, certain primary packaging materials (PPM) such as the syringe barrel and plunger are usually coated with silicone oil, which acts as a lubricant. Due to its direct contact with drug, silicone oil can increase the number of particles in the syringe, which could lead to adverse interactions. Compliance with regulatory defined silicone oil quantities in certain drug products, such as ophthalmic, presents a trade-off with the necessity for desirable low and consistent BLGF. In addition to its siliconization, the dimensional accuracy of PPM has an important role in controlling BLGF. The dimensions of PPM are individualized depending on the product and its design and have certain tolerances that must be met during manufacturing. Most studies on ophthalmic focused on the adverse interactions between silicone oil and the drug. To the authors' knowledge, there have been no public studies so far that have investigated the impact of the dimensional variability of PPM on the BLGF in ophthalmic PFS. In this study, we applied advanced optical shaft and tactile measuring technologies to investigate this impact. The syringes investigated, were first sampled during aseptic production, and tested for BLGF. Subsequently, defined dimensions of PPM were measured individually. The results showed that the dimensional variability of PPM can have a negative impact on the BLGF, despite their conformity to specifications, which indicates that the currently available market quality of PPM is improvable for critical drug products such as ophthalmic. This study could serve as an approach to define product-specific requirements for primary packaging combinations and thus appropriate specifications based on data during the development stage of drug products.

Differential distribution of fibrovascular proliferative membranes in 25-gauge vitrectomy for proliferative diabetic retinopathy.

To analyze the distribution of fibrovascular proliferative membranes (FVPMs) in proliferative diabetic retinopathy (PDR) patients that treated with pars plana vitrectomy (PPV), and to evaluate the outcomes separately. This was a retrospective and cross-sectional study. Consecutive 25-gauge (25-G) PPV cases operated for PDR from May 2018 to April 2020. According to the FVPMs images outlined after operations, subjects were assigned into three groups: arcade type group, juxtapapillary type group, and central type group. All patients were followed up for over one year. General characteristics, operation-related variables, postoperative parameters and complications were recorded. Among 103 eyes recruited, the FVPMs distribution of nasotemporal and inferiosuperioral was significantly different (both P<0.01), with 95 (92.23%) FVPMs located in the nasal quadrants, and 74 (71.84%) in the inferior. The eyes with a central FVPM required the longest operation time, with silicon oil used in most patients, generally combined with tractional retinal detachment (RD) and rhegmatogenous RD, the worst postoperative best-corrected visual acuity (BCVA) and the highest rates of recurrent RD (all P<0.05). FVPM type, age of onset diabetes mellitus, preoperative BCVA, and combined with tractional RD and rhegmatogenous RD were significantly associated with BCVA improvement (all P<0.05). Compared with the central type group, the arcade type group had higher rates of BCVA improvement. FVPMs are more commonly found in the nasal and inferior mid-peripheral retina in addition to the area of arcade vessels. Performing 25-G PPV for treating PDR eyes with central FVPM have relatively worse prognosis.

Retinal redetachment after silicone oil removal: a risk factor analysis

PurposeTo report the rate of retinal redetachment after silicone oil removal following rhegmatogenous retinal detachment surgery and to determine potential risk factors.MethodsRetrospective observational case series of 161 eyes who underwent rhegmatogenous retinal detachment surgery and subsequent silicone oil removal. Pre- and intraoperative risk factors were evaluated using univariate and multivariate logistic regression. We also evaluated the effect of tamponade duration on anatomical outcomes.ResultsThe median tamponade duration was 5.9 [4.3;7.6] months. Seventeen (10.6%) eyes underwent silicone oil removal within 3 months of surgery, with a median delay of 2.3 [2.0;2.8] months. The rate of retinal detachment after silicone oil removal was 14.9%. A history of previous unsuccessful surgery was the only significant risk factor for retinal redetachment after silicone oil removal (OR 4.8, 95%CI [1.5;19.0], p = 0.02). The use of 360° laser retinopexy and concomitant air or gas tamponade during silicone oil removal were not found to affect the redetachment rate. Eyes with silicone oil tamponade ≤ 3 months showed an increased, albeit not significant, risk of developing recurrent rhegmatogenous retinal detachment after silicone oil removal (35.3% versus 12.5%, p = 0.06).ConclusionA retinal redetachment occurred in 14.9% of eyes undergoing silicone oil removal following rhegmatogenous retinal detachment surgery. Previous failed surgery was associated with a 4.8-fold increased risk of developing recurrent rhegmatogenous retinal detachment after silicone oil removal. Eyes with silicone oil tamponade ≤ 3 months tended to have a higher redetachment rate.Trial registration numberID NCT05647928 (12th April 2022)

Effect of 0.625% Intravitreal Povidone-iodine injections in Patients with Endophthalmitis

Purpose: We report on three patients who received 0.625% povidone-iodine (PVI) intravitreal injections to treat endophthalmitis that did not respond to conventional antibiotic treatment or were inoperable.Case summary: Case 1 was a 42-year-old female with suspected left-eye endophthalmitis that developed after anterior chamber irrigation to treat silicone oil emulsification. A 0.625% PVI intravitreal injection reduced inflammation of the anterior chamber and the vitreous. Case 2 was an 84-year-old male who was blind in the left eye due to glaucoma. He was diagnosed with endogenous endophthalmitis on the basis of the anterior chamber hypopyon and vitreous inflammation. After 0.625% PVI intravitreal injection, the endophthalmitis resolved without any recurrence. Case 3 was a 49-year-old female with suspected endogenous left-eye endophthalmitis attributable to a liver abscess. Despite intravitreal antibiotic injections, the inflammation worsened. A 0.625% PVI intravitreal injection improved both the anterior chamber and vitreous inflammation.Conclusions: Intravitreal 0.625% PVI injection is a useful option when a patient with endophthalmitis is likely to not recover full vision, when surgery cannot be performed, and when there is no response to empirical antibiotics.

Electrothermal-Assisted Photothermal Lubrication Surfaces for Continuous Anti-Icing/Deicing in Multiple Low-Temperature Environments.

Solving the problem of ice accumulation on solid surfaces is of great significance to the economic development of the country and the safety of people's lives. In this work, a coating with multifunctional photothermal/electrothermal solid-state lubrication (PEL) for anti-icing/deicing was prepared in layers based on the intrinsic properties of silicone oil and paraffin wax in combination with conductive graphite and multiwalled carbon nanotubes. Silicone oils and paraffins are used as lubricating media giving the coating excellent lubricity, which results in a water sliding angle (SA) of only 12° on the PEL surface. Meanwhile, PEL shows favorable static and dynamic ice resistance at low temperatures; at -10 °C, the freezing time of water droplets on the PEL surface is extended by at least 4 times compared to the bare substrate. Furthermore, PEL also offers highly efficient photothermal and electrothermal deicing performance, which can effectively remove the accumulated ice at a light intensity of 0.6 kW/m2 or an EPD of 0.1 W/cm2. Meanwhile, the synergistic deicing mechanism of photothermal and electrothermal was verified at -20 °C. Interestingly, the coating shows heat-assisted healing ability due to the phase change characteristic of paraffin wax, which allows the coating to regain lubricating properties after mechanical abrasion. Therefore, this work provides a reliable way for the design of stable all-weather anti-icing/deicing strategies at low temperatures.

Coalescence investigations in a small‐scale continuously operated setup for bubble column design

AbstractA novel micro‐channel technique for analyzing the coalescence of bubbles and obtaining relevant information for the creation of a coalescence database is presented. The micro‐channel improves the coalescence investigations by a continuously operated setup, reduces the accumulation of impurities and increases the amount of recorded data. To introduce the new setup, studies with alcoholic, electrolytic aqueous systems and liquid silicone oil as a second liquid are presented, showing the influence of different concentrations. Artificial intelligence has been successfully developed to automate data generation. This approach improves the understanding of bubble coalescence by introducing a reproducible setup. Furthermore, it facilitates the transition to a predictive column design through data‐based decisions and modelling.

Scalable Preparation of Liquid Infused Coatings for Lubrication of 103 m2 Dry Ski Slopes.

To facilitate effective training for freestyle skiers on artificial dry ski slopes, it is crucial to reduce the friction coefficient of the slopes and closely match it with that of snow. Traditional lubrication methods, such as water or soapy water, come with multiple disadvantages, including water waste, which leads to environmental pollution, short-lived effectiveness, and high costs. In this study, we have successfully developed a method for the scalable preparation of a liquid-infused coating (LIC) by tandem spraying inexpensive and environmentally friendly SiO2 particles and silicone oil lubricants. Experimental results showed that the resulting LIC is capable of imparting slippery properties to various surfaces, regardless of the surface chemistry. Moreover, the presence of LIC could reduce the friction coefficient significantly. By carefully regulating the surface composition, we achieved a friction coefficient of 0.059 between a snowboard and the LIC-functionalized ski slope, closely matching that between the snowboard and snow in a typical skiing competition venue (∼0.06). We successfully applied LIC onto 103 m2 dry ski slopes, providing a training ground for professional freestyle skiers.

Evaluation of coating materials on the characterization of size and viability of virus-laden particles collected with an Andersen cascade impactor

Airborne pathogens are typically associated with particles, and the transport behavior of these particles is largely driven by their size. To better understand airborne transmission of viral diseases and develop effective control measures, proper size characterization of virus-laden particles is essential. The Andersen cascade impactor (ACI) is an 8-stage air sampler that separates aerosol particles into 9 aerodynamic size fractions. During sampling with an ACI under certain conditions, particles may bounce upon impact with the collection plates of the ACI, leading to eventual deposition on a stage further downstream than their target stage. Coating collection plates with adhesive materials may help decrease particle bounce; however, it may also affect the viability of collected pathogens. In this study, we evaluated different materials for their ability to minimize particle bounce while conserving virus viability during the collection of viral aerosol particles with an ACI. We evaluated nine materials - Tween® 80, silicone oil, Span® 85, Brij® 35, glycerol, mineral oil, gelatin, bovine serum albumin, and virus growth media - on their effect to inactivate H1N1 influenza virus and bovine coronavirus, a surrogate of SARS-CoV-2. Plates coated with gelatin, silicone oil, and mineral oil resulted in the least reduction of viability for both viruses. These materials were then used to sample viral aerosol particles in a wind tunnel. Results of physical particle collection, viral load and viral viability from the various ACI stages revealed no significant differences in aerodynamic size distribution between coated and uncoated plates, and the size distribution was similar to that reported by an optical particle sizer. Overall, our results did not support the need to coat ACI collection plates when characterizing viral aerosol particles under the conditions of this study. However, we did identify potential coating materials which could conserve virus viability maximally, if particle bounce is of concern.