Research: Comparing ASTM F1671 with a Modified Dot-Blot Method to Evaluate Personal Protective Materials.

Effective personal protective equipment (PPE) is critical in preventing the spread of infectious diseases. Appropriate test systems and test soils are needed to adequately evaluate PPE. ASTM test method F903, which specifies the test method setup also used in ASTM F1670 and F1671, has been used for decades to test liquid (ASTM F1670) or viral (ASTM F1671) penetration resistance of PPE fabrics. However, an alteration of the bacteriophage propagation method detailed in the standard was necessary to obtain consistent titers of virus. In this study, modification of the nutrient broth provided consistently higher titers of virus and the use of the top agar in smaller increments prevented premature solidification. This study then compared the standard ASTM F1671 (using bacteriophage ϕχ174) with a modified dot-blot method to assess viral penetration of PPE materials. The results indicated that ASTM F1671 and the dot-blot apparatus methods were equivalent. The dot-blot method described here is less labor intensive and faster than the ASTM F1671 method. However, using the dot-blot system, which uses antibodies to detect the bacteriophage and signal amplification, does not indicate if virus viability or infectivity is retained, whereas the ASTM F1671 method indicates both. Nonetheless, the method presented in this investigation is a substantial improvement of a standard method for viral challenge testing of PPE materials.

Research: Using Clinically Relevant Test Soils to Evaluate Personal Protective Materials.

Effective personal protective equipment (PPE) is critically important to preventing the spread of infectious diseases. Appropriate test systems and test soils are needed to adequately evaluate PPE. ASTM test method F903, which specifies the test method setup also used in ASTM F1670/F1670M-17a and ASTM F1671/F1671M-13, has been used for decades to test liquid penetration resistance of fabrics. All three standards require at least 60 mL of challenge liquid, such as synthetic blood solution (F1670) or bacteriophage in nutrient broth (F1671). The three ASTM test methods also are labor intensive and prone to exhibiting problems with leakage around the gaskets. Previous work comparing the F903 test apparatus with a modified dot-blot apparatus to evaluate the visual penetration of a blood test soil in series of commercially available gowns and drapes demonstrated that the methods are comparable and revealed that penetration through PPE material may depend on the test solution. The study described here evaluated a series of clinically relevant test soils (blood, vomit, urine, and feces) in penetration of PPE garments using the modified dot-blot apparatus. The results indicated that a vomit test soil penetrates PPE material more often than blood, urine, or fecal test soils and that the blood test soil has the least number of PPE failures. Incorporating clinically relevant, chemically defined test soils to evaluate PPE material should be considered to protect healthcare workers and reduce the spread of infectious material.

Evaluation of Apparatus Used to Test Liquid through Protective Materials: Comparison of a Modified Dot-Blot Apparatus to the ASTM Penetration Cell.

Personal protective equipment (PPE), such as gowns used in the latest Ebola outbreak in Western Africa, are critical in preventing the spread of deadly diseases. Appropriate test systems and test soils are needed to adequately evaluate PPE. ASTM F903, Standard Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Liquid, has been used for decades to test fabrics' resistance to liquid penetration. However, this test apparatus requires at least 60 mL of test solutions, is labor intensive, and has problems with leakage around the gaskets. We compared the F903 test apparatus to a modified dot-blot apparatus to evaluate the visual penetration of a blood test soil. A series of commercially available gowns and drapes were tested in each apparatus. Using blood test soil at 2 psi, there was no statistically significant difference between the two methods except for in one gown. By comparing this gown in the ASTM test apparatus with and without a screen, the particular screen selected did not account for the difference between the dot-blot and F903 apparatuses; however, it is conceivable that a particular screen/fabric combination could account for this difference. The modified dot-blot apparatus was evaluated using three different test solutions: blood, vomit, and a labeled protein (goat anti-rabbit immunoglobulin G-horseradish peroxidase [GaR IgG-HRP]) in a blood test soil solution. This testing revealed significant difference in penetration for some of the PPE garments. The modified dot-blot had several large advantages over the ASTM apparatus-over six times less specimen volume and no edge or gasket leakage. In addition, nitrocellulose can be easily incorporated into the modified dot-blot apparatus, enabling the trapping of viruses and proteins that penetrate PPE-thus permitting the use of antibodies to quickly and sensitively detect penetration.

Controlled initial surge despite high drug fraction and high solubility.

Potential connections between release profiles and solvent evaporation rates alongside polymer chemistry were elucidated for the release of tetracycline hydrochloride from two different poly (d, l-lactide-co-glycolide) (PLGA) film matrices containing high drug fractions (50%, 30%, and 15%), and prepared at two distinct solvent evaporation rates. At highest tetracycline concentrations (50%), (i) the early release rates were ≤0.5 µg/min in all cases; (ii) release was linear from systems fabricated with lower lactic content and slower solvent evaporation rate and bimodal from systems fabricated with higher lactic content and faster evaporation rate; (iii) surface fractions covered by the drug were similar at both evaporation rates for 85:15 PLGA but very different for 50:50 PLGA, leading to unexpectedly reduced early release from 50:50 PLGA than from 85:15 PLGA when both the matrices were fabricated using a slower evaporation rate. These features remained unaffected in case of low drug concentration. Results suggested that during the formation of the drug-polymer microstructure, the combined effect of polymer chemistry and solvent evaporation rate sets apart the surface characteristics and the initial release profiles of systems containing high drug fraction, and an appropriate combination of these parameters may be utilized to control the early stage of drug release.

Evaluating Device Design and Cleanability of Orthopedic Device Models Contaminated with a Clinically Relevant Bone Test Soil.

UNLABELLED: Reusable medical devices need to be cleaned prior to disinfection or sterilization and subsequent use to prevent infections. The cleanability of medical devices depends in part on the design of the device. This study examined how models of orthopedic medical devices of increasing complexity retain calcium phosphate bone cement, a relevant test soil for these devices. METHODS: The dye Alizarin Red S and micro-computed tomography (µCT) were used to assess the amount and location of bone cement debris in a series of model orthopedic devices. Testing was performed after soiling and cleaning once, and soiling and cleaning 10 times. RESULTS: The color change of the dye after reacting with the bone cement was useful for indicating the presence of bone cement in these models. High-resolution µCT analysis provided the volume and location of the bone cement. Models that were more complex retained significantly more bone debris than simpler designs. Model devices repeatedly soiled and cleaned 10 times retained significantly more bone debris than those soiled and cleaned once. CONCLUSION: Significantly more bone cement was retained in the more complex lumen structures. This information may be useful in designing reusable orthopedic devices, and other complex medical devices with lumens.

Evaluation of intraocular reactivity to metallic and ethylene oxide contaminants of medical devices in a rabbit model.

OBJECTIVE: To evaluate the intraocular reactivity to metallic and ethylene oxide (EO) contaminants of ophthalmic devices in rabbits. DESIGN: Two experimental animal studies. PARTICIPANTS: Thirty-five New Zealand white rabbits. METHODS: A metallic exposure study and an EO exposure study were performed. In the first study, both eyes of 25 rabbits were equally allocated to intracameral injections of alumina 0.2 µg, alumina 20 µg, copper sulfate 0.4 µg, copper sulfate 20 µg, or an aqueous control. In the second study, 10 rabbits were allocated (5 per group) to receive intracamerally an ophthalmic viscosurgical device (OVD) exposed to EO or not exposed to EO (control). All eyes were examined by slit lamp at baseline and 3, 6, 9, 24, 48, and 72 hours after exposure, with dilated indirect ophthalmoscopy being performed at 24 and 72 hours. Tonometry was performed only in the first study. MAIN OUTCOME MEASURES: Grade of corneal clouding, anterior chamber (AC) flare, AC cells, AC fibrin, iridal hyperemia, cell and fibrin on the lens surface, vitreous haze and cells, lens opacities, intraocular pressure, and onset time. RESULTS: For metallic compounds at the study's low doses, mean inflammatory grades were 0.2 or less above the control for all responses at all time points. For the high-dose alumina, mean inflammatory grades peaked at 6 to 9 hours at 0.5 to 0.7 above the control responses for conjunctival congestion, iris hyperemia, AC cells, flare, and fibrin and declined over the remaining time points. For the high-dose copper sulfate, mean inflammatory grades peaked between 3 and 24 hours at 1.2 to 1.8 above the control responses for conjunctival congestion, iris hyperemia, AC cells, flare, fibrin, and corneal clouding, then subsequently declined. The intraocular pressure changes appeared significant for only high-dose copper sulfate, with mean declines of 4.3 to 7.5 mmHg at 6 to 72 hours. No clinically meaningful differences in ocular inflammation were observed between the OVD exposed to EO and the OVD not exposed to EO. CONCLUSIONS: Alumina and copper sulfate did not cause clinically meaningful ocular inflammation at the low study levels (levels expected with ophthalmic devices). Ethylene oxide exposure of an OVD was not associated with inflammation.

The effects of contact lens materials on a multipurpose contact lens solution disinfection activity against Staphylococcus aureus.

OBJECTIVES: To determine the effect of 8 different lens materials on polyhexamethylene biguanide (PHMB) concentration in multipurpose solution (MPS) levels over time and to determine the effect of lenses on lens solution microbial efficacy over time. METHODS: Silicone hydrogel lenses and conventional hydrogel lenses were soaked in polypropylene lens cases filled with contact lens MPS containing 1 ppm PHMB for 6, 12, 24, 72, and 168 hours. Cases filled with the same solution without lenses were controls. After each time period, solutions from cases with the 8 types of lenses and controls were assayed for activity against Staphylococcus aureus according to International Organization for Standardization-14729 with modifications. Solutions were analyzed for PHMB concentration at each time point. RESULTS: Some of the different lens materials significantly affected the PHMB concentration (P<0.0001) and the biocidal efficacy. Etafilcon A lenses significantly decreased PHMB levels after only 6 hours of lens soak time. The product lot of MPS used was also significant (P<0.0001). Enfilcon A, senofilcon A, and lotrafilcon B lenses did not significantly decrease PHMB levels. CONCLUSIONS: The efficacy of MPS was affected by some lens materials and PHMB concentration. Lens materials differ in their effect on PHMB concentration and the subsequent efficacy of the MPS. Over time, some lens materials can significantly reduce the PHMB concentration and the MPS's microbial activity against S. aureus.

The effect of contact lens materials on disinfection activity of polyquaternium-1 and myristamidopropyl dimethylamine multipurpose solution against Staphylococcus aureus.

OBJECTIVES: This study examined the interaction of seven different lens materials with a multipurpose solution (MPS) containing the disinfectants polyquaternium-1 (0.001%) and myristamidopropyl dimethylamine (0.0005%). The objective of this study was to determine whether the different lens materials affect the concentration of a disinfectant in this commercially available MPS and the efficacy of the disinfectant against Staphylococcus aureus. METHODS: Silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrafilcon B) and a conventional hydrogel lens (etafilcon A) were soaked in polypropylene lens cases filled with commercially available MPS containing 0.001% polyquaternium-1 and 0.0005% myristamidopropyl dimethylamine for 6, 12, 24, 72, and 168 hours. Empty lens cases were also filled with MPS. After each time point, solutions from cases containing the seven types of lenses and controls were assayed for activity against S. aureus according to International Standards Organization 14729 standard with modifications. Test solutions were analyzed for polyquaternium-1 and myristamidopropyl dimethylamine concentration at each time point. RESULTS: The concentration of polyquaternium-1 and myristamidopropyl dimethylamine remaining in the lens cases was reduced only slightly over time. Storage with the lenses did not adversely affect biocidal efficacy of the solution, and in some cases, it was significantly better (P=0.0029). CONCLUSION: The efficacy of this polyquaternium-1 and myristamidopropyl dimethylamine MPS to kill S. aureus was not adversely affected by the presence of lens materials soaking in the cases. Thus, current methods for performing solution antimicrobial testing should be reevaluated.

Impact of contact lens materials on multipurpose contact lens solution disinfection activity against Fusarium solani.

OBJECTIVE: To investigate the effects of eight different soft contact lenses on disinfection efficacy of a multipurpose solution (MPS) containing polyhexamethylene biguanide (PHMB) against Fusarium solani. METHODS: Six silicone hydrogel lenses (galyfilcon A, senofilcon A, comfilcon A, enfilcon A, balafilcon A, and lotrifilcon B) and two conventional hydrogel lenses (polymacon and etafilcon A) were placed in polypropylene lens cases filled with MPS containing 0.0001% PHMB and soaked for 6, 12, 24, 72, and 168 hours. After each interval, depleted MPS from lens cases were removed and assayed for activity against F. solani according to International Organization for Standardization (ISO) 14729 stand-alone procedure. A portion was aliquoted for chemical analysis. RESULTS: Soaking etafilcon A, balafilcon A, and polymacon lenses for 6 hours reduced the concentration of PHMB in MPS by more than half the stated labeled concentration, with concentrations below the limit of detection for etafilcon A-depleted and balafilcon A-depleted solutions after 12 and 72 hours of soaking, respectively. Except for comfilcon A-depleted solutions, all others failed to consistently obtain one log reduction of F. solani. The solutions soaked with etafilcon A, balafilcon A, and polymacon lenses for 24 hours or more lost all or almost all fungicidal activity against F. solani. CONCLUSIONS: Over time, the disinfectant uptake by some lenses can significantly reduce the PHMB concentration and the fungicidal activity of the MPS against F. solani. Current ISO methodology does not address the reduction in microbiocidal efficacy when lenses are soaked in MPS. The ISO committee should consider adding "soaking experiments" to quantify the effect that contact lens materials have on the performance of MPSs.

Material properties that predict preservative uptake for silicone hydrogel contact lenses.

OBJECTIVES: To assess material properties that affect preservative uptake by silicone hydrogel lenses. METHODS: We evaluated the water content (using differential scanning calorimetry), effective pore size (using probe penetration), and preservative uptake (using high-performance liquid chromatography with spectrophotometric detection) of silicone and conventional hydrogel soft contact lenses. RESULTS: Lenses grouped similarly based on freezable water content as they did based on total water content. Evaluation of the effective pore size highlighted potential differences between the surface-treated and non-surface-treated materials. The water content of the lens materials and ionic charge are associated with the degree of preservative uptake. CONCLUSIONS: The current grouping system for testing contact lens-solution interactions separates all silicone hydrogels from conventional hydrogel contact lenses. However, not all silicone hydrogel lenses interact similarly with the same contact lens solution. Based upon the results of our research, we propose that the same material characteristics used to group conventional hydrogel lenses, water content and ionic charge, can also be used to predict uptake of hydrophilic preservatives for silicone hydrogel lenses. In addition, the hydrophobicity of silicone hydrogel contact lenses, although not investigated here, is a unique contact lens material property that should be evaluated for the uptake of relatively hydrophobic preservatives and tear components.

Environmental fate of polyhexamethylene biguanide.

Polyhexamethylene biguanide (PHMB) is used as a bacteriocidal agent in a variety of applications from medical devices to pools, but is highly toxic to some aquatic species. The stability of PHMB in various environmental matrices was examined. 80% of PHMB was present in fortified creek samples after 20 days, but bound immediately to soils with the exception of sandy soil. PHMB was absorbed to below detectable levels by weathered concrete within 12 h. In addition, one over the counter wound care product containing PHMB was evaluated to assess environmental leaching; detectable levels (20 µg/mL) were still present after 1 week.

Increased UVA exposures and decreased cutaneous Vitamin D(3) levels may be responsible for the increasing incidence of melanoma.

Cutaneous malignant melanoma (CMM) has been increasing at a steady exponential rate in fair-skinned, indoor workers since before 1940. A paradox exists between indoor and outdoor workers because indoor workers get three to nine times less solar UV (290-400 nm) exposure than outdoor workers get, yet only indoor workers have an increasing incidence of CMM. Thus, another "factor(s)" is/are involved that increases the CMM risk for indoor workers. We hypothesize that one factor involves indoor exposures to UVA (321-400 nm) passing through windows, which can cause mutations and can break down vitamin D(3) formed after outdoor UVB (290-320 nm) exposure, and the other factor involves low levels of cutaneous vitamin D(3). After vitamin D(3) forms, melanoma cells can convert it to the hormone, 1,25-dihydroxyvitamin D(3), or calcitriol, which causes growth inhibition and apoptotic cell death in vitro and in vivo. We measured the outdoor and indoor solar irradiances and found indoor solar UVA irradiances represent about 25% (or 5-10 W/m(2)) of the outdoor irradiances and are about 60 times greater than fluorescent light irradiances. We calculated the outdoor and indoor UV contributions toward different biological endpoints by weighting the emission spectra by the action spectra: erythema, squamous cell carcinoma, melanoma (fish), and previtamin D(3). Furthermore, we found production of previtamin D(3) only occurs outside where there is enough UVB. We agree that intense, intermittent outdoor UV overexposures and sunburns initiate CMM; we now propose that increased UVA exposures and inadequately maintained cutaneous levels of vitamin D(3) promotes CMM.

Steam sterilization and internal count sheets: assessing the potential for cytotoxicity.

Count sheets, when placed in contact with surgical instruments during steam sterilization, can transfer ink to the instruments. To explore whether this poses a safety concern, stainless steel instruments were placed on top of completely inked paper and subjected to steam sterilization, extracted, and tested for cytotoxicity. Preprinted labels were examined in a similar fashion. Extracts from stainless steel devices exposed to ink, toner, or labels showed no significant cytotoxic response, although the ink residue on the devices after steam sterilization is difficult to remove and detrimental to the instrument. Placing a barrier between the count sheet and the devices facilitates reuse of the instruments.

Hyperthermia increases the cytotoxicity of many exogenous compounds.

Cytotoxicity testing of extracts from medical device materials is typically conducted at 37 degrees C. It may be more relevant to screen extracts from device materials for in vitro cytotoxicity at temperatures found in febrile patients. To address this, the cytotoxicity of selected chemicals, drugs, and medical device extracts was evaluated in vitro following incubation at normothermic (37 degrees C) and hyperthermic (39 degrees C) conditions. In L929 cells, the percentage of cell death increased from 2-fold to more than 4-fold after chemical exposure when cells were maintained at 39 degrees C. Extracts of some medical devices and materials showed a 10-fold increase in cytotoxicity when cells were maintained at 39 degrees C as compared to 37 degrees C. For many of the substances in this study, exogenous compounds that are toxic at normothermic conditions (37 degrees C) are more cytotoxic under hyperthermic conditions (39 degrees C). The toxicity of compounds was more readily discernable at the higher incubation temperature, even at lower concentrations. In vitro cytotoxicity testing of chemicals and extracts at febrile temperatures can provide more sensitive and relevant biocompatibility tests than under normothermic conditions alone.

The presence of fecal test soil protects bacteria during cleaning/disinfection.

Reusable medical devices (RMDs) must be reprocessed between uses to render them safe for each use and each patient. Cleaning used devices removes organic and inorganic soil making them either safe for reuse or ready for disinfection/sterilization depending on the device. Although cleaning is an important step in a RMD's life cycle, it is not always a priority during device design. In addition, when performing cleaning validation, it is recommended that the manufacturer takes into consideration, what the most appropriate or worst case conditions are in terms of type of soil or the presence of bacteria. This study compared the ability of three different cleaning/disinfecting agents (water, alcohol, and bleach) to remove bacteria and fecal test soil from two different polymers: polypropylene and ultrahigh molecular weight polyethylene (UHMWPE) with two different roughness. There were some differences in the effects of the cleaning/disinfecting agents, the materials, and the roughness depending on the particular circumstances. However, the most consistent effect on the removal of bacteria was the presence of soil, which protected the bacteria from being removed. Conversely, the presence of bacteria played little role in the removal of soil. Although the interactions between material type and roughness, soil type, and bacteria are complicated, they should be taken into account during device design and reprocessing validation to create a device that is easy and safe to use. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1706-1710, 2019.

Extraction and stability of ethylene oxide residue in medical devices.

Ethylene oxide (EO) gas is commonly used to sterilize medical devices. A major concern is the amount of residue that may remain on or in the device and be available in the body. Some standards (ASTMF619 and ISO 10993-12) recommend using two different extraction solutions (one polar, one nonpolar), for sample preparation prior to testing medical devices. However, ISO 10993-7 recommends water to process medical devices to determine EO residual levels. To address this, EO residual levels were examined in different extraction solutions. EO residual levels from devices and materials extracted with different solutions were evaluated. Results from this study indicate little difference between extraction solutions of water, cell culture media, and serum (less than 30% difference). Given the increased cost and increased background noise of media or serum over water, using only water to process medical devices and materials for EO residues appears adequate.

Solvent or thermal extraction of ethylene oxide from polymeric materials: Medical device considerations.

Ethylene oxide (EO) gas is commonly used to sterilize medical devices. Bioavailable residual EO, however, presents a significant toxicity risk to patients. Residual EO is assessed using international standards describing extraction conditions for different medical device applications. We examine a series of polymers and explore different extraction conditions to determine residual EO. Materials were sterilized with EO and exhaustively extracted in water, in one of three organic solvents, or in air using thermal desorption. The EO exhaustively extracted varies significantly and is dictated by two factors: the EO that permeates the material during sterilization; and the effectiveness of the extraction protocol in flushing residual EO from the material. Extracted EO is maximized by a close matches between Hildebrand solubility parameters δpolymer , δEO , and δsolvent . There remain complexities to resolve, however, because maximized EO uptake and detection are accompanied by great variability. These observations may inform protocols for material selection, sterilization, and EO extraction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2455-2463, 2018.

Impact of nitinol stent surface processing on in-vivo nickel release and biological response.

Although nitinol is widely used in percutaneous cardiovascular interventions, a causal relationship between nickel released from implanted cardiovascular devices and adverse systemic or local biological responses has not been established. The objective of this study was to investigate the relationship between nitinol surface processing, in-vivo nickel release, and biocompatibility. Nitinol stents manufactured using select surface treatments were implanted into the iliac arteries of minipigs for 6 months. Clinical chemistry profile, complete blood count, serum and urine nickel analyses were performed periodically during the implantation period. After explant, stented arteries were either digested and analyzed for local nickel concentration or fixed and sectioned for histopathological analysis of stenosis and inflammation within the artery. The results indicated that markers for liver and kidney function were not different than baseline values throughout 180 days of implantation regardless of surface finish. In addition, white blood cell, red blood cell, and platelet counts were similar to baseline values for all surface finishes. Systemic nickel concentrations in serum and urine were not significantly different between processing groups and comparable to baseline values during 180 days of implantation. However, stents with non-optimized surface finishing had significantly greater nickel levels in the surrounding artery compared to polished stents. These stents had increased stenosis with potential for local inflammation compared to polished stents. These findings demonstrate that proper polishing of nitinol surfaces can reduce in-vivo nickel release locally, which may aid in minimizing adverse inflammatory reactions and restenosis. STATEMENT OF SIGNIFICANCE: Nitinol is a commonly used material in cardiovascular medical devices. However, relationships between nitinol surface finishing, in-vivo metal ion release, and adverse biological responses have yet to be established. We addressed this knowledge gap by implanting single and overlapped nitinol stents with different surface finishes to assess systemic impact on minipigs (i.e. serum and urine nickel levels, liver and kidney function, immune and blood count) over the 6 month implantation period. In addition, nickel levels and histopathology in stented arteries were analyzed on explant to determine relationships between surface processing and local adverse tissue reactions. The findings presented here highlight the importance of surface processing on in-vivo nickel release and subsequent impact on local biological response for nitinol implants.

Designing for cleanability: The effects of material, surface roughness, and the presence of blood test soil and bacteria on devices.

Cleaning reusable medical devices removes organic and inorganic soil, which allows for effective disinfection and sterilization. However, it is not always clear what variables to consider when validating cleaning. This study compared the ability of 3 different cleaning agents (ie, water, alcohol, and bleach) to remove bacteria (ie, vegetative and spores) and artificial blood test soil from 2 common device materials: polypropylene and ultra-high-molecular-weight polyethylene. There was a complex interaction between bacteria, soil, and surface roughness.