Experimental evaluation of respiratory droplet spread to rooms connected by a central ventilation system.

This article presents results from an experimental study to ascertain the transmissibility of the SARS-CoV-2 virus between rooms in a building that are connected by a central ventilation system. Respiratory droplet surrogates made of mucus and virus mimics were released in one room in a test building, and measurements of concentration levels were made in other rooms connected via the ventilation system. The paper presents experimental results for different ventilation system configurations, including ventilation rate, filtration level (up to MERV-13), and fractional outdoor air intake. The most important finding is that respiratory droplets can and do transit through central ventilation systems, suggesting a mechanism for viral transmission (and COVID-19 specifically) within the built environment in reasonable agreement with well-mixed models. We also find the deposition of small droplets (0.5-4 µm) on room walls to be negligibly small.

Investigation of potential aerosol transmission and infectivity of SARS-CoV-2 through central ventilation systems.

The COVID-19 pandemic has raised concern of viral spread within buildings. Although near-field transmission and infectious spread within individual rooms are well studied, the impact of aerosolized spread of SARS-CoV-2 via air handling systems within multiroom buildings remains unexplored. This study evaluates the concentrations and probabilities of infection for both building interior and exterior exposure sources using a well-mixed model in a multiroom building served by a central air handling system (without packaged terminal air conditioning). In particular, we compare the influence of filtration, air change rates, and the fraction of outdoor air. When the air supplied to the rooms comprises both outdoor air and recirculated air, we find filtration lowers the concentration and probability of infection the most in connected rooms. We find that increasing the air change rate removes virus from the source room faster but also increases the rate of exposure in connected rooms. Therefore, slower air change rates reduce infectivity in connected rooms at shorter durations. We further find that increasing the fraction of virus-free outdoor air is helpful, unless outdoor air is infective in which case pathogen exposure inside persists for hours after a short-term release. Increasing the outdoor air to 33% or the filter to MERV-13 decreases the infectivity in the connected rooms by 19% or 93% respectively, relative to a MERV-8 filter with 9% outdoor air based on 100 quanta/h of 5 µm droplets, a breathing rate of 0.48 m3/h, and the building dimensions and air handling system considered.

Biomimetic surgical mesh to replace fascia with tunable force-displacement.

Here we mimic the mechanical properties of native fascia to design surgical mesh for fascia replacement. Despite the widespread acceptance of synthetic materials as tissue scaffolds for pelvic floor disorders, mechanical property mismatch between mesh and adjacent native tissue drives fibrosis and erosion, leading the FDA to remove several surgical meshes from the market. However, autologous tissue does not induce either fibrosis or adjacent tissue erosion, suggesting the potential for biomimetic surgical mesh. In this study, we determined the design rules for mesh that mimics native fascia by mathematically modeling multi-component polymer networks, composed of elastin-like and collagen-like fibers, using a spring-network model. To validate the model, we measured the stress-strain curves of native bovine and nonhuman primate (Macaca mulatta) abdominal fascia in both toe and linear regions. We find that the stiffer collagen-like fibers must remain limp until the elastin-like fibers extend to the initial length of spanning collagen-like fibers under uniaxial tension. Comparing model results to experiment determines the product of fiber volume fraction and elastic modulus, a critical design parameter. Dual fiber mesh with mechanical properties that mimic fascia are feasible. These results have broad application to a wide range of soft tissue replacements including ~200,000 surgeries/year for pelvic floor disorders, because standard-of-care mesh contain only stiffer polymers that behave more like collagen than native tissue.

Measurement of Inflammation in Eosinophilic Esophagitis Using an Eosinophil Peroxidase Assay.

OBJECTIVES: We describe a simple, quick method to measure an eosinophil granule protein, eosinophil peroxidase (EPO), as a marker of eosinophil activity, in eosinophilic esophagitis (EoE). METHODS: Esophageal mucosal brushings initially were collected from 36 patients with active EoE (n=13), resolved EoE (n=13), and controls (n=10) before endoscopic biopsy collection; the brushes were frozen at -80 ºC until assayed. EPO on the brush was measured in a colorimetric assay visually and by spectrophotometric absorbance measurements (at 492 nm), and was compared with peak eosinophil counts in esophageal biopsy specimens. The assay was calibrated with known EPO concentrations; as EPO increased in the assay, the color changed from light yellow to dark brown. RESULTS: Mucosal brush specimens from active EoE yielded orange to dark brown colors with absorbance measurements > 1.1 U; in contrast, control and resolved EoE brush specimens yielded a light to dark yellow color with absorbance measurements < 1.1. We then corroborated the results at the bedside (real time) in 16 additional patients. EPO on the brush was measured directly in < 1 h in the assay visually and by absorbance at 492 nm. Absorbance units strongly correlated with peak eosinophil counts both with the frozen brush (rs=0.79, P<0.0001) and with the bedside (rs=0.86, P<0.00017) approaches. CONCLUSIONS: The results support the use of this rapid method to detect and monitor EoE disease activity. Moreover, because eosinophils infiltrate and degranulate in the esophagus in EoE in a patchy manner, this method may be more accurate than current practice by testing for an eosinophil constituent from both intact and degranulated cells, and by sampling large portions of the esophageal lumen rather than small biopsy specimens that may not be representative of eosinophil involvement.

Size and shape characterization of hydrated and desiccated exosomes.

Exosomes are stable nanovesicles secreted by cells into the circulation. Their reported sizes differ substantially, which likely reflects the difference in the isolation techniques used, the cells that secreted them, and the methods used in their characterization. We analyzed the influence of the last factor on the measured sizes and shapes of hydrated and desiccated exosomes isolated from the serum of a pancreatic cancer patient and a healthy control. We found that hydrated exosomes are close-to-spherical nanoparticles with a hydrodynamic radius that is substantially larger than the geometric size. For desiccated exosomes, we found that the desiccated shape and sizing are influenced by the manner in which drying occurred. Isotropic desiccation in aerosol preserves the near-spherical shape of the exosomes, whereas drying on a surface likely distorts their shapes and influences the sizing results obtained by techniques that require surface fixation prior to analysis.

Extracellular Eosinophil Granule Protein Deposition in Ringed Esophagus with Sparse Eosinophils.

BACKGROUND: Eosinophilic esophagitis (EoE) remains difficult to classify because of varying presentations. Not uncommonly, patients present with symptoms of esophageal dysfunction and have esophageal changes on endoscopy resembling EoE but without >15 eosinophils/HPF. Patients with low numbers of eosinophils in esophageal biopsy specimens may have esophageal changes and symptomatic disease brought about by eosinophil granule protein deposition without recognizable intact cells. AIM: To determine whether extracellular eosinophil granule protein deposition is present in the esophagi of patients with low eosinophil numbers who have clinical symptoms and characteristic endoscopic esophageal changes of EoE including ringed esophagus (RE). METHODS: Esophageal biopsy specimens were studied from eight EoE patients with >15 eosinophils per high power field (HPF) and nine patients with RE (<15 eosinophils/HPF). The specimens were analyzed for eosinophil granule proteins, major basic protein 1 (eMBP1) and eosinophil-derived neurotoxin (EDN), by indirect immunofluorescence. RESULTS: Both EoE and RE showed positive EDN and eMBP1 extracellular deposition; control esophagus showed minimal or none. Comparing EoE and RE, extracellular EDN and eMBP1 were similar except that EDN in EoE was greater in the distal esophagus. CONCLUSIONS: This study highlights the importance of assessing eosinophil granule protein deposition in esophageal disease with potential eosinophil involvement. Persistent/progressive esophageal changes may be brought about by eosinophil granule proteins despite low numbers of intact cells. The meaning of "resolution" in EoE may need to be redefined based on numbers of esophageal eosinophils, extracellular eosinophil granule protein deposition, and subsequent clinical course of patients.

Electron microscopy elucidates eosinophil degranulation patterns in patients with eosinophilic esophagitis.

BACKGROUND: In patients with eosinophilic esophagitis (EoE), eosinophils accumulate and release granule proteins onto esophageal epithelium. However, little is understood about the mechanism of eosinophil degranulation. OBJECTIVE: To determine and quantify eosinophil degranulation patterns, we studied esophageal biopsy specimens from both the proximal and distal esophagi of 9 randomly selected patients with EoE. METHODS: The specimens were fixed in glutaraldehyde, embedded, sectioned, and imaged by means of transmission electron microscopy. Eosinophils and their granules were identified by their distinctive morphology, and all eosinophils and granules were imaged. A total of 1672 images from 18 esophageal specimens were evaluated and graded. Eosinophils were categorized based on membrane integrity and by cytoplasmic vesiculation as evidence of piecemeal degranulation. Granules were categorized based on reversal of staining (eosinophil granule core lightening) and localization within and outside the cells. RESULTS: The results revealed that greater than 98% of eosinophils infiltrating the esophagus in patients with EoE demonstrate morphologic abnormalities ranging from granule changes with reversal of staining to marked cytoplasmic vesiculation to loss of cellular membrane integrity with cytolytic disruption and release of intact membrane-bound granules into the tissues. Approximately 81% of eosinophils showed membrane disruption. Extracellular granules were abundant in at least 70% of the images, and approximately 50% of these granules showed reversal of staining. On the basis of the prominence of tubulovesicular development, piecemeal degranulation appears closely related to the other morphologic changes seen in patients with EoE. CONCLUSION: These findings reveal that eosinophils in esophageal biopsy specimens from patients with EoE are abnormal, with greater than 80% showing cytolysis, and therefore that evaluation by means of light microscopy after hematoxylin and eosin staining might not accurately reflect eosinophil involvement.

Electrospray differential mobility analysis for nanoscale medicinal and pharmaceutical applications.

Nanoscale characterization tools hold the potential to overcome long-standing medicinal and pharmaceutical challenges. For example, electrospray differential mobility analysis (ES-DMA) is an emerging tool that rapidly provides label-free multimodal size distributions for proteins and particles from ~1 nm to <500 nm with subnanometer precision. Here we critically review the contributions of this tool to medicine, pharmaceutical practice, and pharmaceutical production. Our review critically evaluates, first, the use of ES-DMA for diagnostic strategies that detect and quantify lipoproteins, bacterial infections, viruses and amyloid fibrillation and then focuses on ES-DMA's contribution to treatment strategies that employ tailored virus-like particles as vaccines and decorated nanoparticle vectors for gene delivery. Our review also highlights ES-DMA's contribution to viral clearance and antibody aggregation and potential as a process analytical technology (PAT). FROM THE CLINICAL EDITOR: Electrospray differential mobility analysis is an emerging nanotechnology-based tool with potential clinical utility in the detection and quantification of lipoproteins, glycoproteins, viruses, amyloids, bacterial infections. Its contribution to treatment strategies and pharmaceutical production is also discussed in this comprehensive review.

Evaluation of entropy driven jet symmetry transitions.

Here we determine whether entropy drives planar turbulent jets into round turbulent jets. Determining when a jet flow transitions from one symmetry to the next is an important but incompletely resolved problem. The constructal view argues that the transition between symmetries of jet flows is governed by the minimization or maximization of entropy. Here we explore whether entropy increases with the transition of a planar turbulent jet into a round turbulent jet and whether entropy maximization (or minimization) predicts the same location of symmetry transition as velocity matching. We find that entropy considerations presented do not predict this transition.

Physical characterization of icosahedral virus ultra structure, stability, and integrity using electrospray differential mobility analysis.

We present a rapid and quantitative method to physically characterize the structure and stability of viruses. Electrospray differential mobility analysis (ES-DMA) is used to determine the size of capsomers (i.e., hexons) and complete capsids. We demonstrate how to convert the measured mobility size into the icosahedral dimensions of a virus, which for PR772 become 68.4 nm for vertex-to-vertex, 54.4 nm for facet-to-facet, and 58.2 nm for edge-to-edge lengths, in reasonable agreement with dimensions from transmission electron microscopy for other members of the family Tectiviridae (e.g., PRD1). These results indicate ES-DMA's mobility diameter most closely approximates the edge-to-edge length. Using PR772's edge length (36.0 nm) and the size of the major capsid hexon (≈8.4 nm) from ES-DMA with icosahedral geometry, PR772's T = 25 symmetry is confirmed and the number of proteins in the capsid shell is determined. We also demonstrate the use of ES-DMA to monitor the temporal disintegration of PR772, the thermal degradation of PP7, and the appearance of degradation products, essential to viral stability assays. These results lay groundwork essential for the use of ES-DMA for a variety of applications including monitoring of vaccine and gene therapy vector products, confirmation of viral inactivation, and theoretical studies of self-assembling macromolecular structures.

Polypeptide grafted hyaluronan: A self-assembling comb-branched polymer constructed from biological components.

Rheological evidence is provided demonstrating that covalent grafting of monodisperse isotactic poly(L-leucine) branches onto linear hyaluronan (HA) polysaccharide chains yields comb-branched HA chains that self-assemble into long-lived physical networks in aqueous solutions driven by hydrophobic interactions between poly(L-leucine) chains. This is in stark contrast to native (unmodified) HA solutions which exhibit no tendency to form long-lived physical networks.

Probing the nucleus model for oligomer formation during insulin amyloid fibrillogenesis.

We find evidence for a direct transition of insulin monomers into amyloid fibrils without measurable concentrations of oligomers or protofibrils, suggesting that fibrillogenesis may occur directly from assembly of denaturing insulin monomers rather than by successive transitions through protofibril nuclei. To support our finding, we obtain size distributions using electrospray differential mobility analysis (ES-DMA), which provides excellent resolution to clearly distinguish among small oligomers and rapidly generates statistically significant size distributions. The distributions detect an absence of significant peaks between 6 nm and 17 nm as the monomer reacts into fibers-exactly the size range observed by others for small-angle-neutron-scattering-measured intermediates and for circular supramolecular structures. They report concentrations in the nanomolar range, whereas our limit of detection remains three-orders-of-magnitude lower (<5 pmol/L). This finding, along with the lack of significant increases in the ß-sheet content of monomers using circular dichroism, suggests monomers do not first structurally rearrange and accumulate in a ß-rich state but react and reorganize at the growing fiber's tip. These results quantitatively inform reaction-based theories of amyloid fiber formation and have implications for neurodegenerative, protein conformation ailments including Alzheimer's disease and bovine spongiform encephalopathy.

Packing and size determination of colloidal nanoclusters.

Here we demonstrate a rapid and quantitative means to characterize the size and packing structure of small clusters of nanoparticles in colloidal suspension. Clustering and aggregation play important roles in a wide variety of phenomena of both scientific and technical importance, yet characterizing the packing of nanoparticles within small clusters and predicting their aerodynamic size remains challenging because available techniques can lack adequate resolution and sensitivity for clusters smaller than 100 nm (optical techniques), perturb the packing arrangement (electron microscopies), or provide only an ensemble average (light scattering techniques). In this article, we use electrospray-differential mobility analysis (ES-DMA), a technique that exerts electrical and drag forces on the clusters, to determine the size and packing of small clusters. We provide an analytical model to determine the mobility size of various packing geometries based on the projected area of the clusters. Data for clusters aggregated from nominally 10 nm gold particles and nonenveloped viruses of various sizes show good agreement between measured and predicted cluster sizes for close-packed spheres.

Oral Administration of 99mTechnetium-Labeled Heparin in Eosinophilic Esophagitis.

OBJECTIVE: To determine if heparin labeled with 99mTechnetium (99mTc) could be an imaging probe to detect eosinophil-related inflammation in eosinophilic esophagitis and to determine the biodistribution and radiation dosimetry of 99mTc-heparin oral administration using image-based dosimetry models with esophageal modeling. METHODS: Freshly prepared 99mTc-heparin was administered orally to 5 research subjects. Radioactivity was measured by whole-body scintigraphy and single-photon emission computed tomography during the 24 hours postadministration. Following imaging, endoscopic examination was performed. The biodistribution of esophageal radioactivity was compared with endoscopic findings, eosinophil counts in biopsy tissues, and immunostaining for eosinophil granule major basic protein-1 (eMBP1). These studies were conducted from July 1, 2013, until April 22, 2017. RESULTS: Oral administration of 99mTc-heparin was well tolerated in all 5 subjects. The entire esophagus could be visualized dynamically during oral administration. Bound esophageal radioactivity marked areas of inflammation as judged by endoscopy scores, by eosinophils per high power field and by localization of eMBP1 using immunostaining. Ninety percent of the radioactivity did not bind to the esophagus and passed through the gastrointestinal tract. CONCLUSION: The biodistribution of ingested 99mTc-heparin is almost exclusively localized to the gastrointestinal tract. Radiation exposure was highest in the lower gastrointestinal tract and was comparable with other orally administered diagnostic radiopharmaceuticals. The use of swallowed 99mTc-heparin may aid in assessing eosinophil-related inflammation in the esophagus.

Length distribution of single-walled carbon nanotubes in aqueous suspension measured by electrospray differential mobility analysis.

The first characterization of the length distribution of single-walled carbon nanotubes (SWCNT) dispersed in a liquid by electrospray differential mobility analysis (ES-DMA) is presented. Although an understanding of geometric properties of SWCNTs, including length, diameter, aspect ratio, and chirality, is essential for commercial applications, rapid characterization of nanotube length distributions remains challenging. Here the use of ES-DMA to obtain length distributions of DNA-wrapped SWCNTs dispersed in aqueous solutions is demonstrated. Lengths measured by ES-DMA compare favorably with those obtained from multiangle light scattering, dynamic light scattering, field flow fractionation with UV/vis detection, and atomic force microscopy, validating ES-DMA as a technique to measure SWCNTs of <250 nm in length. The nanotubes are previously purified and dispersed by wrapping with oligomeric DNA in aqueous solution and centrifuging to remove bundles and amorphous carbon. These dispersions are particularly attractive due to their amenability to bulk processing, ease of storage, high concentration, compatibility with biological and high-throughput manufacturing environments, and for their potential applications ranging from electronics and hydrogen-storage vessels to anticancer agents.

Quantitative characterization of quantum dot-labeled lambda phage for Escherichia coli detection.

We characterize CdSe/ZnS quantum dot (QD) binding to genetically modified bacteriophage as a model for bacterial detection. Interactions among QDs, lambda (lambda) phage, and Escherichia coli are examined by several cross-validated methods. Flow and image-based cytometry clarify fluorescent labeling of bacteria, with image-based cytometry additionally reporting the number of decorated phage bound to cells. Transmission electron microscopy, image-based cytometry, and electrospray differential mobility analysis allow quantization of QDs attached to each phage (4-17 QDs) and show that lambda phage used in this study exhibits enhanced QD binding to the capsid by nearly a factor of four compared to bacteriophage T7. Additionally, the characterization methodology presented can be applied to the quantitative characterization of other fluorescent nanocrystal-biological conjugates.

Quantitative characterization of virus-like particles by asymmetrical flow field flow fractionation, electrospray differential mobility analysis, and transmission electron microscopy.

Here we characterize virus-like particles (VLPs) by three very distinct, orthogonal, and quantitative techniques: electrospray differential mobility analysis (ES-DMA), asymmetric flow field-flow fractionation with multi-angle light scattering detection (AFFFF-MALS) and transmission electron microscopy (TEM). VLPs are biomolecular particles assembled from viral proteins with applications ranging from synthetic vaccines to vectors for delivery of gene and drug therapies. VLPs may have polydispersed, multimodal size distributions, where the size distribution can be altered by subtle changes in the production process. These three techniques detect subtle size differences in VLPs derived from the non-enveloped murine polyomavirus (MPV) following: (i) functionalization of the surface of VLPs with an influenza viral peptide fragment; (ii) packaging of foreign protein internally within the VLPs; and (iii) packaging of genomic DNA internally within the VLPs. These results demonstrate that ES-DMA and AFFFF-MALS are able to quantitatively determine VLP size distributions with greater rapidity and statistical significance than TEM, providing useful technologies for product development and process analytics.

Designing pre-tensioned core-shell fibers to treat pelvic floor disorders.

Here we relate support provided to the pelvic floor by composite fibers having pre-tensioned cores secured by thin shells to tunable fiber properties. Surgical treatment of pelvic floor disorders including stress urinary incontinence and pelvic organ prolapse often inserts polymeric mesh to support pelvic fascia. However, achieving optimal levels of mesh tension and organ lift in minimally invasive surgeries remains challenging. Fibers with pre-tensioned cores and biodegradable shells have the potential to overcome this challenge by allowing reconstructive surgeons to "dial in" specific amounts of support without over tensioning mesh slings, which may lead to soft tissue erosion and voiding dysfunction. Consequently, this study quantifies the relationship between fiber dimensions and properties with the lift these fibers (once integrated into mesh) can provide to pelvic organs. Our linear elastic model quantifies the minimum and maximum amount of pre-tensioning allowed from tissue lift and core-shell delamination considerations, respectively. The model indicates that the elastic modulus of the biodegradable shell polymer should be orders of magnitude larger than that of the core polymer and be at least 10% of the core radius to preserve tension within the core that subsequently translates into tissue support.

Determination of protein aggregation with differential mobility analysis: application to IgG antibody.

Here we describe the use of electrospray differential mobility analysis (ES-DMA), also known as gas-phase electrophoretic mobility molecular analysis (GEMMA), as a method for measuring low-order soluble aggregates of proteins in solution. We demonstrate proof of concept with IgG antibodies. In ES-DMA, aqueous solutions of the antibody protein are electrosprayed and the various aerosolized species are separated according to their electrophoretic mobility using a differential mobility analyzer. In this way, complete size distributions of protein species present from 3 to 250 nm can be obtained with the current set up, including distinct peaks for IgG monomers to pentamers. The sizes of the IgG and IgG aggregates measured by DMA were found to be in good agreement with those calculated from simple models, which take the structural dimensions of IgG from protein crystallographic data. The dependence of IgG aggregation on the solution concentration and ionic strength was also examined, and the portion of aggregates containing chemically crosslinked antibodies was quantified. These results indicate that ES-DMA holds potential as a measurement tool to study protein aggregation phenomena such as those associated with antibody reagent manufacturing and protein therapeutics.