Gediminas Mainelis

Collection of Airborne Microorganisms by Electrostatic Precipitation

The applicability of electrostatic precipitation as a method for bioaerosol collection was investigated by using a modified Electrostatic Aerosol Sampler (EAS) (Model 3100, TSI Inc., St. Paul, MN). The physical and biological efficiencies of this method were determined. The tests were performed using three bacterial species which were collected onto agar, into water, and onto filters. The physical collection efficiency was higher than 80% when using a sampling flow rate of 1 L/min. When the Bacillus subtilis var niger (BG) spores were collected on agar, about 50-60% of the collected culturable organisms formed colonies. The bioefficiency exceeded 90% when the BG spores were collected on a filter, but was only 15-22% when collected into water. The Mycobacterium bovis BCG bacteria recovered at the 0-8% level on all three collection media. The least number of colonies were formed when Pseudomonas fluorescens bacteria were collected on any of the collection media. The data show that the process of electrostat...

Inhibition of lung tumor growth by complex pulmonary delivery of drugs with oligonucleotides as suppressors of cellular resistance

Development of cancer cell resistance, low accumulation of therapeutic drug in the lungs, and severe adverse treatment side effects represent main obstacles to efficient chemotherapy of lung cancer. To overcome these difficulties, we propose inhalation local delivery of anticancer drugs in combination with suppressors of pump and nonpump cellular resistance. To test this approach, nanoscale-based delivery systems containing doxorubicin as a cell death inducer, antisense oligonucleotides targeted to MRP1 mRNA as a suppressor of pump resistance and to BCL2 mRNA as a suppressor of nonpump resistance, were developed and examined on an orthotopic murine model of human lung carcinoma. The experimental results show high antitumor activity and low adverse side effects of proposed complex inhalatory treatment that cannot be achieved by individual components applied separately. The present work potentially contributes to the treatment of lung cancer by describing a unique combinatorial local inhalation delivery of drugs and suppressors of pump and nonpump cellular resistance.

Collection of airborne microorganisms by a new electrostatic precipitator

Bioaerosol exposure assessment and the protection of civil/governmental/military establishments from bioterrorism require the development of low-power bioaerosol collectors that are able not only to efficiently collect airborne microorganisms, but also to preserve their biological integrity. In search for such a method, a new bioaerosol sampler was evaluated. In this device, the airborne microorganisms are imparted electrical charges and are then deposited in an electrical field onto a growth medium (agar). Experiments were conducted with Pseudomonas fluorescens vegetative cells, Bacillus subtilis var. niger (BG) endospores (used to simulate the spores of anthrax-causing Bacillus anthracis when testing bioaerosol sensors) and Penicillium brevicompactum fungal spores. It was found that 80–90% of initially “charge-neutralized” biological particles were removed from the air, when a small amount of ionization was generated in the electrostatic precipitators (ESP) inlet and a precipitation voltage of ±4000V was applied across the agar plates. Over 70% of viable BG and P. brevicompactum spores entering the ESP were enumerated as colony forming units. The bioefficiency of the new sampler was about the same as that of the Biosampler, which was tested in parallel. In experiments with sensitive P. fluorescens vegetative cells, the ESP enumerated twice as many cells as the Biosampler. The latter result indicates that the electrostatic collection method may be especially useful for the collection and enumeration of sensitive airborne microorganisms. Experiments investigating the effect of aging time on the amount of electrical charge carried by the airborne microorganisms showed that the level of electrical charge gradually decreases with increasing aging time. However, even after the P. fluorescens cells had remained airborne for an hour, they retained enough electrical charge to be collected with efficiency higher than 70%.

Electrical charges on airborne microorganisms

Abstract We have investigated the parameters affecting the magnitude and polarity of the electric charges carried by biological particles in the airborne state. A recently developed experimental setup through which we analyzed the electric charges imposed on airborne particles by a means of induction charging (Mainelis et al. (Aerosol Sci. Technol. 2001, submitted for publication)) was utilized for this research. In this study, the microorganisms were aerosolized under controlled conditions and an electric mobility analyzer extracted particles of specific electric mobility. The extracted microorganisms were then analyzed by an optical particle size spectrometer. The amount of electric charge carried by airborne microorganisms was found to depend on the dispersion method and can be more than 10,000 elementary electric charges. This finding contrasts with the low electric charge levels carried by non-biological particles. Our data show that repeated pneumatic dispersion of sensitive bacteria affects their structural integrity, which, in turn, changes the magnitude of electric charges carried by these bacteria. We have concluded that the amount of electric charge carried by aerosolized bacteria may be used as an indicator of mechanical stress. It was also found that the electrical conductivity and the pH level of a bacterial suspension increase during aerosolization from a Collison nebulizer. Thus, these two parameters may be used as indicators of the mechanical stress, injury and loss in viability, endured by bacteria during aerosolization, i.e., measuring the electrical conductivity and pH level of bacterial suspensions may be a simple and convenient method for monitoring the “wear and tear” of the bacteria suspended in deionized water.

Design and Collection Efficiency of a New Electrostatic Precipitator for Bioaerosol Collection

We have developed and tested a new bioaerosol sampler in which airborne microorganisms are collected by electrostatic means. In this sampler, 2 ionizers charge the incoming particles if they carry insufficient electric charge for efficient collection. The organisms are then subjected to a precipitating electric field and are collected onto 2 square agar plates positioned along the flow axis. Tests with nonbiological NaCl particles versus B. subtilis var. niger (BG) spores and vegetative cells have shown that airborne microorganisms are collected more efficiently than nonbiological particles, even when the microorganisms have first passed through an electric charge neutralizer with no additional charging applied. The difference was attributed to the natural charges contained in cell membranes or spore coats of the microorganisms. Charge-neutralized BG spores and vegetative cells were collected at 4 L/min with efficiencies close to 80%, depending on the precipitation voltage, versus 50-60% for NaCl test particles. When incoming BG spores were charged with positive ions and then collected by a precipitating voltage of + 1,300 V, about 80% of the incoming spores were collected and more than 70% of incoming spores formed colonies. These experiments with BG spores have also indicated that there were no significant particle losses inside the sampler. The collection efficiency of biological and nonbiological particles increased to 90-100% when the particles were externally charged and the precipitating voltage was increased to more than - 4,000 V. It has also been shown that the aerosolized BG spores (used as anthrax simulants for bioaerosol sensors) carry a net negative electric charge. Thus the collection efficiency depends on the polarity of the electric field applied across the agar plates. These findings indicate that the collection of airborne microorganisms is possible by electrostatic precipitation without prior electric charging if the microorganisms already carry electric charges. These are usually high immediately after their release into the air.

Potential for exposure to engineered nanoparticles from nanotechnology-based consumer spray products

The potential for human exposure to engineered nanoparticles due to the use of nanotechnology-based consumer sprays (categorized as such by the Nanotechnology Consumer Products Inventory) is examined along with analogous products, which are not specified as nanotechnology-based (regular products). Photon correlation spectroscopy was used to obtain particle size distributions in the initial liquid products. Transmission electron microscopy was used to determine particle size, shape, and agglomeration of the particles. Realistic application of the spray products near the human breathing zone characterized airborne particles that are released during use of the sprays. Aerosolization of sprays with standard nebulizers was used to determine their potential for inhalation exposure. Electron microscopy detected the presence of nanoparticles in some nanotechnology-based sprays as well as in several regular products, whereas the photon correlation spectroscopy indicated the presence of particles <100 nm in all investigated products. During the use of most nanotechnology-based and regular sprays, particles ranging from 13 nm to 20 μm were released, indicating that they could he inhaled and consequently deposited in all regions of the respiratory system. The results indicate that exposures to nanoparticles as well as micrometer-sized particles can be encountered owing to the use of nanotechnology-based sprays as well as regular spray products.

Investigation of Cut-Off Sizes and Collection Efficiencies of Portable Microbial Samplers

This research investigated the physical collection efficiencies and cut-off sizes of SMA MicroPortable, BioCulture, Microflow, Microbiological Air Sampler (MAS-100), Millipore Air Tester (MAT), SAS Super 180, and RCS High Flow portable microbial samplers when collecting Polystyrene Latex particles ranging from 0.5 to 9.8 μm in aerodynamic size. Traditional collection efficiency measurements often directly compare particle concentrations upstream and downstream of the sampler without considering the particle losses. Here, we developed a new approach which tests collection efficiencies of the sampler with and without agar collection plate loaded. This method thus allows estimating the effective collection efficiency, i.e., the fraction of incoming particles deposited onto the agar collection medium only. The experimental cut-off sizes, or d 50, of the investigated samplers ranged from 1.2 μm for the RCS High Flow, 1.7 μm for the MAS-100, 2.1 μm for SAS Super 180, to 2.3 μm for MAT; for other three samplers they were close to or above 5 μm. In most cases the theoretical d 50 was lower than the experimental value, which was likely due to the dissipation of impactor jets and the influence of cross-flow in the multi-nozzle impactors. For most samplers, we observed a notable difference between the collection efficiency obtained by the traditional measurement method and the effective collection efficiency. In general, all samplers collected 10% or less of 0.5 μm particles onto the agar medium. This study indicates that the use of most of the tested bioaerosol samplers may result in a substantial underestimation of bacterial concentrations, especially of single bacterial cells with diameter 0.5–1.0 μm. On the other hand, most of the investigated samplers would be more efficient when collecting larger fungal spores.

Assessment of Electrical Charge on Airborne Microorganisms by a New Bioaerosol Sampling Method

Bioaerosol sampling is necessary to monitor and control human exposure to harmful airborne microorganisms. An important parameter affecting the collection of airborne microorganisms is the electrical charge on the microorganisms. Using a new design of an electrostatic precipitator (ESP) for bioaerosol sampling, the polarity and relative strength of the electrical charges on airborne microorganisms were determined in several laboratory and field environments by measuring the overall physical collection efficiency and the biological collection efficiency at specific precipitation voltages and polarities. First, bacteria, fungal spores, and dust dispersed from soiled carpets were sampled in a walk-in test chamber. Second, a simulant of anthrax-causing Bacillus anthracis spores was dispersed and sampled in the same chamber. Third, bacteria were sampled in a small office while four adults were engaged in lively discussions. Fourth, bacteria and fungal spores released from hay and horse manure were sampled in a horse barn during cleanup operations. Fifth, bacteria in metalworking fluid droplets were sampled in a metalworking simulator. It was found that the new ESP differentiates between positively and negatively charged microorganisms, and that in most of the tested environments the airborne microorganisms had a net negative charge. This adds a signature to the sampled microorganisms that may assist in their identification or differentiation, for example, in an anti-bioterrorism network.

Potential for inhalation exposure to engineered nanoparticles from nanotechnology-based cosmetic powders.

Background: The market of nanotechnology-based consumer products is rapidly expanding, and the lack of scientific evidence describing the accompanying exposure and health risks stalls the discussion regarding its guidance and regulation. Objectives: We investigated the potential for human contact and inhalation exposure to nanomaterials when using nanotechnology-based cosmetic powders and compare them with analogous products not marketed as nanotechnology based. Methods: We characterized the products using transmission electron microscopy (TEM) and laser diffraction spectroscopy and found nanoparticles in five of six tested products. TEM photomicrographs showed highly agglomerated states of nanoparticles in the products. We realistically simulated the use of cosmetic powders by applying them to the face of a human mannequin head while simultaneously sampling the released airborne particles through the ports installed in the mannequin’s nostrils. Results: We found that a user would be exposed to nanomaterial predominantly through nanoparticle-containing agglomerates larger than the 1–100-nm aerosol fraction. Conclusions: Predominant deposition of nanomaterial(s) will occur in the tracheobronchial and head airways—not in the alveolar region as would be expected based on the size of primary nanoparticles. This could potentially lead to different health effects than expected based on the current understanding of nanoparticle behavior and toxicology studies for the alveolar region.

Performance of an Electrostatic Precipitator with Superhydrophobic Surface when Collecting Airborne Bacteria

Modern bioaerosol sampling and analysis techniques that enable rapid detection of low bioagent concentrations in various environments are needed to help us understand the causal relationship between adverse health effects and bioaerosol exposures and also to enable the timely biohazard detection in case of intentional release. We have developed a novel bioaerosol sampler, an electrostatic precipitator with superhydrophobic surface (EPSS), where a combination of electrostatic collection mechanism with superhydrophobic collection surface allows for efficient particle collection, removal, and concentration in water droplets as small as 5 μ L. The samplers performance at different sampling flow rates and sampling times was tested with two common bacteria: Pseudomonas fluorescens and Bacillus subtilis. The collection efficiency was determined using the traditional method of microscopic counting as well as the whole-cell quantitative real-time polymerase chain reaction assay (QPCR). The tests indicated that the new sampler achieves collection efficiency as high as 72%. A combination of the satisfactory collection efficiency and the small collecting water droplet volumes allowed achieving sample concentration rates that exceed 1 × 10 6 . In addition, the collection efficiency for both bacteria obtained by the two different methods was not statistically different, indicating the samplers compatibility with the PCR-based sample analysis techniques. In addition, the whole-cell QPCR does not require DNA extraction prior to the PCR reaction which offers faster sample processing. Very high concentration rates achieved with the new sampler as well as its compatibility with the QPCR methodology point toward its suitability for detecting low concentrations of airborne bacterial agents in various environments.