Search

The COVID-19 pandemic has brought an unprecedented crisis to the global health sector. When discharging COVID-19 patients in accordance with throat or nasal swab protocols using RT-PCR, the potential risk of reintroducing the infection source to humans and the environment must be resolved. Here, 14 patients including 10 COVID-19 subjects were recruited; exhaled breath condensate (EBC), air samples and surface swabs were collected and analyzed for SARS-CoV-2 using reverse transcription-polymerase chain reaction (RT-PCR) in four hospitals with applied natural ventilation and disinfection practices in Wuhan. Here we discovered that 22.2% of COVID-19 patients (n = 9), who were ready for hospital discharge based on current guidelines, had SARS-CoV-2 in their exhaled breath (~105 RNA copies/m3). Although fewer surface swabs (3.1%, n = 318) tested positive, medical equipment such as face shield frequently contacted/used by healthcare workers and the work shift floor were contaminated by SARS-CoV-2 (3–8 viruses/cm2). Three of the air samples (n = 44) including those collected using a robot-assisted sampler were detected positive by a digital PCR with a concentration level of 9–219 viruses/m3. RT-PCR diagnosis using throat swab specimens had a failure rate of more than 22% in safely discharging COVID-19 patients who were otherwise still exhaling the SARS-CoV-2 by a rate of estimated ~1400 RNA copies per minute into the air. Direct surface contact might not represent a major transmission route, and lower positive rate of air sample (6.8%) was likely due to natural ventilation (1.6–3.3 m/s) and regular disinfection practices. While there is a critical need for strengthening hospital discharge standards in preventing re-emergence of COVID-19 spread, use of breath sample as a supplement specimen could further guard the hospital discharge to ensure the safety of the public and minimize the pandemic re-emergence risk.

Coronavirus disease 2019 (COVID-19) patients exhaled millions of severe acute respiratory syndrome coronavirus 2 RNA copies per hour, which plays an important role in COVID-19 transmission. Exhaled breath had a higher positive rate (26.9%, n = 52) than surface (5.4%, n = 242) and air (3.8%, n = 26) samples.

Philipp Diebolder,1 Miguel Vazquez-Pufleau,2 Nilantha Bandara,1 Cedric Mpoy,1 Ramesh Raliya,2 Elijah Thimsen,2 Pratim Biswas,2 Buck E Rogers1 1Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO, USA; 2Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, St Louis, MO, USA Introduction: Siliceous nanoparticles (NPs) have been extensively studied in nanomedicine due to their high biocompatibility and immense biomedical potential. Although numerous technologies have been developed, the synthesis of siliceous NPs for biomedical applications mainly relies on a few core technologies predominantly intended to produce spherical-shaped NPs. Methods: In this context, the impact of different morphologies of siliceous NPs on biodistribution in vivo is limited. In the present study, we developed a novel technique based on an aerosol silane reactor to produce sintered silicon NPs of similar size but different surface areas due to distinct spherical subunits. Silica-converted particles were functionalized for radiolabeling with copper-64 (64Cu) to systematically analyze their behavior in the passive targeting of A431 tumor xenografts in mice after intravenous injection.Results: While low nonspecific uptake was observed in most organs, the majority of particles were accumulated in the liver, spleen, and lung. Depending on the morphologies and functionalization, significant differences in the uptake profiles of the particles were observed. In terms of tumor uptake, spherical shapes with lower surface areas showed the highest accumulation and tumor-to-blood ratios of all investigated particles.Conclusion: This study highlights the importance of shape and fuctionalization of siliceous NPs on organ and tumor accumulation as significant factors for biomedical applications. Keywords: silicon, silica, human tumor xenograft, PEGylation, 64Cu

Philipp Diebolder,1 Miguel Vazquez-Pufleau,2 Nilantha Bandara,1 Cedric Mpoy,1 Ramesh Raliya,2 Elijah Thimsen,2 Pratim Biswas,2 Buck E Rogers1 1Department of Radiation Oncology, Washington University School of Medicine, St Louis, MO, USA; 2Department of Energy, Environmental and Chemical Engineering, Washington University in St Louis, St Louis, MO, USA Introduction: Siliceous nanoparticles (NPs) have been extensively studied in nanomedicine due to their high biocompatibility and immense biomedical potential. Although numerous technologies have been developed, the synthesis of siliceous NPs for biomedical applications mainly relies on a few core technologies predominantly intended to produce spherical-shaped NPs. Methods: In this context, the impact of different morphologies of siliceous NPs on biodistribution in vivo is limited. In the present study, we developed a novel technique based on an aerosol silane reactor to produce sintered silicon NPs of similar size but different surface areas due to distinct spherical subunits. Silica-converted particles were functionalized for radiolabeling with copper-64 (64Cu) to systematically analyze their behavior in the passive targeting of A431 tumor xenografts in mice after intravenous injection.Results: While low nonspecific uptake was observed in most organs, the majority of particles were accumulated in the liver, spleen, and lung. Depending on the morphologies and functionalization, significant differences in the uptake profiles of the particles were observed. In terms of tumor uptake, spherical shapes with lower surface areas showed the highest accumulation and tumor-to-blood ratios of all investigated particles.Conclusion: This study highlights the importance of shape and fuctionalization of siliceous NPs on organ and tumor accumulation as significant factors for biomedical applications. Keywords: silicon, silica, human tumor xenograft, PEGylation, 64Cu

Research Summaries: Nanotoxicology: An emerging discipline evolving from studies of ultrafine particles; Translocation of inhaled ultrafine manganese oxide particles to the central nervous system; Nanoparticle (NP) uptake by type I alveolar epithelial cells and their oxidant stress response; Toxicology of nanoparticles: A historical perspective; In vivo skin penetration of quantum dot nanoparticles in the murine model: The effect of UVR; Testing nanomaterials of unknown toxicity: An example based on Platinum nanoparticles of different shapes; Nanoparticles and the Brain: Cause for Concern?; Concept of assessing nanoparticle hazards considering nano-particle dosemetric and chemical/biological response-metrics; Validation of an LDH assay for assessing nanoparticle toxicity; Safety assessment for nanotechnology and nanomedicine: concepts of nanotoxicology., Prepared in cooperation with University of Minnesota, Department of Mechanical Engineering, Minneapolis, MN, and Washington University in St. Louis, Department of Chemical Engineering, St. Louis, MO.

Soubir Basak1, David Brogan2, Hans Dietrich2, Rogers Ritter3, Ralph G Dacey2, Pratim Biswas11Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA; 2Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, USA; 3Stereotaxis Inc., St. Louis, MO, USAAbstract: A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient.  Keywords: nanoparticle ferrofluid, gel-brain model, drug delivery, magnetic agglomeration, transport, magnetic fields

Soubir Basak1, David Brogan2, Hans Dietrich2, Rogers Ritter3, Ralph G Dacey2, Pratim Biswas11Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA; 2Department of Neurological Surgery, Washington University School of Medicine, St. Louis, MO, USA; 3Stereotaxis Inc., St. Louis, MO, USAAbstract: A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient.  Keywords: nanoparticle ferrofluid, gel-brain model, drug delivery, magnetic agglomeration, transport, magnetic fields

This work is subdivided into four parts. The first part consists of characterizing high jet velocity impactors, developing their scaling criteria to facilitate instrument design and prediction of impactor performance under conditions where no calibration data are available. The second part discusses the problem of distortion of size distributions by aerosol sampling instruments because of particle size changes occurring due to vapor or condensable phase transport to and from the particles. The severity of the problem is demonstrated both theoretically and experimentally for a few commonly used aerosol sampling instruments. The third part is the development of a 'Particle Trap Impactor' working on the virtual impaction principle. The inherent problems of bounce and re-entrainment in conventional impactors is minimized, without the addition of substrates such as grease, in these impactors. The result of operating the unit at high temperature is also discussed. The final part is the calculation of the scavenging rate of particles due to differential impaction. The results are used to determine upperbounds on the number concentration of particles entering the impactor to minimize biasing the measurements.

This work is subdivided into four parts. The first part consists of characterizing high jet velocity impactors, developing their scaling criteria to facilitate instrument design and prediction of impactor performance under conditions where no calibration data are available. The second part discusses the problem of distortion of size distributions by aerosol sampling instruments because of particle size changes occurring due to vapor or condensable phase transport to and from the particles. The severity of the problem is demonstrated both theoretically and experimentally for a few commonly used aerosol sampling instruments. The third part is the development of a 'Particle Trap Impactor' working on the virtual impaction principle. The inherent problems of bounce and re-entrainment in conventional impactors is minimized, without the addition of substrates such as grease, in these impactors. The result of operating the unit at high temperature is also discussed. The final part is the calculation of the scavenging rate of particles due to differential impaction. The results are used to determine upperbounds on the number concentration of particles entering the impactor to minimize biasing the measurements.

This work is subdivided into four parts. The first part consists of characterizing high jet velocity impactors, developing their scaling criteria to facilitate instrument design and prediction of impactor performance under conditions where no calibration data are available. The second part discusses the problem of distortion of size distributions by aerosol sampling instruments because of particle size changes occurring due to vapor or condensable phase transport to and from the particles. The severity of the problem is demonstrated both theoretically and experimentally for a few commonly used aerosol sampling instruments. The third part is the development of a 'Particle Trap Impactor' working on the virtual impaction principle. The inherent problems of bounce and re-entrainment in conventional impactors is minimized, without the addition of substrates such as grease, in these impactors. The result of operating the unit at high temperature is also discussed. The final part is the calculation of the scavenging rate of particles due to differential impaction. The results are used to determine upperbounds on the number concentration of particles entering the impactor to minimize biasing the measurements.