Simulated Lung Fluid Research Articles

Development and Evaluation of Chitosan Microparticles Based Dry Powder Inhalation Formulations of Rifampicin and Rifabutin.

The lung is the primary entry site and target for Mycobacterium tuberculosis; more than 80% of the cases reported worldwide are of pulmonary tuberculosis. Hence, direct delivery of anti-tubercular drugs to the lung would be beneficial in reducing both, the dose required, as well as the duration of therapy for pulmonary tuberculosis. In the present study, microsphere-based dry powder inhalation systems of the anti-tubercular drugs, rifampicin and rifabutin, were developed and evaluated, with a view to achieve localized and targeted delivery of these drugs to the lung. The drug-loaded chitosan microparticles were prepared by an ionic gelation method, followed by spray-drying to obtain respirable particles. The microparticles were evaluated for particle size and drug release. The drug-loaded microparticles were then adsorbed onto an inhalable lactose carrier and characterized for in vitro lung deposition on an Andersen Cascade Impactor (ACI) followed by in vitro uptake study in U937 human macrophage cell lines. In vivo toxicity of the developed formulations was evaluated using Sprague Dawley rats. Both rifampicin and rifabutin-loaded microparticles had MMAD close to 5 μm and FPF values of 21.46% and 29.97%, respectively. In vitro release study in simulated lung fluid pH 7.4 showed sustained release for 12 hours for rifampicin microparticles and up to 96 hours for rifabutin microparticles, the release being dependent on both swelling of the polymer and solubility of the drugs in the dissolution medium. In vitro uptake studies in U937 human macrophage cell line suggested that microparticles were internalized within the macrophages. In vivo acute toxicity study of the microparticles in Sprague Dawley rats revealed no significant evidence for local adverse effects. Thus, spray-dried microparticles of the anti-tubercular drugs, rifampicin and rifabutin, could prove to be an improved, targeted, and efficient system for treatment of tuberculosis.

Risk assessment of bioaccessible trace elements in smoke haze aerosols versus urban aerosols using simulated lung fluids

Abstract Smoke-haze episodes, caused by uncontrolled peat and forest fires, occur almost every year in the South-East Asian region with increased concentrations of PM2.5 (airborne particulate matter (PM) with diameter ≤ 2.5 μm). Particulate-bound trace elements (TrElems), especially carcinogenic and toxic elements, were measured during smoke haze as well as non-haze periods in 2014 as they are considered to be indicators of potential health effects. The bioaccessibilities of 13 TrElems were investigated using two types of simulated lung fluids (SLFs), Gamble's solution and artificial lysosomal fluid (ALF), instead of the commonly used leaching agent (water). The dissolution kinetics was also examined for these TrElems. Many TrElems showed higher solubility in SLFs, and were more soluble in ALF compared to the Gamble's solution. Cu, Mn and Cd were observed to be the most soluble trace elements in ALF, while in Gamble's solution the most soluble trace elements were Cu, Mn and Zn. The dissolution rates were highly variable among the elements. Health risk assessment was conducted based on the measured concentrations of TrElems and their corresponding toxicities for three possible scenarios involving interactions between carcinogenic and toxic TrElems and SLFs, using the United States Environmental Protection Agency (USEPA) human health risk assessment model. The cumulative cancer risks exceeded the acceptable level (1 in a million i.e. 1 × 10−6). However, the estimation of health quotient (HQ) indicated no significant chronic toxic health effects. The risk assessment results revealed that the assessment of bioaccessibility of particulate-bound TrElems using water as the leaching agent may underestimate the health risk.

Toward Repositioning Niclosamide for Antivirulence Therapy of Pseudomonas aeruginosa Lung Infections: Development of Inhalable Formulations through Nanosuspension Technology

Inhaled antivirulence drugs are currently considered a promising therapeutic option to treat Pseudomonas aeruginosa lung infections in cystic fibrosis (CF). We have recently shown that the anthelmintic drug niclosamide (NCL) has strong quorum sensing (QS) inhibiting activity against P. aeruginosa and could be repurposed as an antivirulence drug. In this work, we developed dry powders containing NCL nanoparticles that can be reconstituted in saline solution to produce inhalable nanosuspensions. NCL nanoparticles were produced by high-pressure homogenization (HPH) using polysorbate 20 or polysorbate 80 as stabilizers. After 20 cycles of HPH, all formulations showed similar properties in the form of needle-shape nanocrystals with a hydrodynamic diameter of approximately 450 nm and a zeta potential of -20 mV. Nanosuspensions stabilized with polysorbate 80 at 10% w/w to NCL (T80_10) showed an optimal solubility profile in simulated interstitial lung fluid. T80_10 was successfully dried into mannitol-based dry powder by spray drying. Dry powder (T80_10 DP) was reconstituted in saline solution and showed optimal in vitro aerosol performance. Both T80_10 and T80_10 DP were able to inhibit P. aeruginosa QS at NCL concentrations of 2.5-10 μM. NCL, and these formulations did not significantly affect the viability of CF bronchial epithelial cells in vitro at microbiologically active concentrations (i.e., ≤10 μM). In vivo acute toxicity studies in rats confirmed no observable toxicity of the NCL T80_10 DP formulation upon intratracheal administration at a concentration 100-fold higher than the anti-QS activity concentration. These preliminary results suggest that NCL repurposed in the form of inhalable nanosuspensions has great potential for the local treatment of P. aeruginosa lung infections as in the case of CF patients.

Testing single extraction methods and in vitro tests to assess the geochemical reactivity and human bioaccessibility of silver in urban soils amended with silver nanoparticles

To assess if the geochemical reactivity and human bioaccessibility of silver nanoparticles (AgNPs) in soils can be determined by routine soil tests commonly applied to other metals in soil, colloidal Ag was introduced to five pots containing urban soils (equivalent to 6.8mgAgkg−1 soil). Following a 45days stabilization period, the geochemical reactivity was determined by extraction using 0.43M and 2M HNO3. The bioaccessibility of AgNPs was evaluated using the Simplified Bioaccessibility Extraction Test (SBET) the “Unified BARGE Method” (UBM), and two simulated lung fluids (modified Gamble’s solution (MGS) and artificial lysosomal fluid (ALF)).The amount of Ag extracted by 0.43M and 2M HNO3 soil tests was <8% and <50%, respectively of the total amount of Ag added to soils suggesting that the reactivity of Ag present in the soil can be relatively low. The bioaccessibility of Ag as determined by the four in vitro tests ranged from 17% (ALF extraction) to 99% (SBET) indicating that almost all Ag can be released from soil due to specific interactions with the organic ligands present in the simulated body fluids.This study shows that to develop sound soil risk evaluations regarding soil contamination with AgNPs, aspects of Ag biochemistry need to be considered, particularly when linking commonly applied soil tests to human risk assessment.

Crystal chemical and structural modifications of erionite fibers leached with simulated lung fluids

Inhalation of erionite has been proven to be the cause of the extended epidemic of malignant mesothelioma occurring in Central Anatolia, Turkey, and of cases of lung diseases in the U.S.A. Its carcinogenicity is three orders of magnitude greater than that of regulated asbestos. Here we report the results of the investigation of the structural and crystal chemical modifications occurring in erionite leached with artificial lysosomal fluid (ALF) and Gamble’s solution. ALF leaching produces a migration of Na+ ions from Ca1 to Ca2 extraframework cationic site, without the occurrence of any significant modification of the chemical composition of the fibers. In contrast, leaching with Gamble’s solution induces a complex ionic-exchange process resulting in a temporary partial replacement of Na+ by Ca2+, coming from the fluid, which is fixed at a third Ca3 cationic site. Subsequently, the exchange process reverses. In fact, Ca2+ is removed from Ca3 and Na+ migrates back to Ca1, the structure being indistinguishable from the starting, unleached material. Such processes seem to be accompanied by a progressive amorphization of fibers. Present data could provide valuable background for a more detailed comprehension of the morphostructural/biological activity relationships inducing pathogenicity.

Lecithin/TPGS-based spray-dried self-microemulsifying drug delivery systems: In vitro pulmonary deposition and cytotoxicity

The aim of the present work was to develop a new solid self-microemulsifying drug delivery system (SMEDDS) for the pulmonary delivery of the poorly water-soluble anti-cancer drug atorvastatin (AVT). Microemulsion (ME) was first developed using isopropyl myristate (IPM), a combination of 2 biocompatible surfactants: lecithin/d-α-tocopheryl polyethylene glycol succinate (TPGS) and ethanol as co-surfactant. Two types of lecithin with different phosphatidylcholine (PC) contents were compared. Phase diagram, physico-chemical characterization and stability studies were used to investigate ME region. Solid SMEDDS were then prepared by spray-drying the selected ME using a combination of carriers composed of sugars, leucine as dispersibility enhancer with or without polyethylene glycol (PEG) 6000. Yield, flow properties, particle size and in vitro pulmonary deposition were used to characterize the spray-dried powders. Reconstituted MEs were characterized in terms of morphology, particle size and size distribution. In vitro cytotoxicity study was undertaken on lung cancer cell line for the selected MEs and SD-SMEDDS formulae. Results showed that the most satisfactory MEs properties were obtained with 1:3 lecithin/TPGS, 1:1 lecithin/oil and 1:1 surfactant/co-surfactant ratios. A larger ME area was obtained with lecithin containing 100% PC compared to the less expensive lecithin containing 20% PC. By manipulating spray drying parameters, carrier composition and ratio of ME lipids to carrier, microparticles with more than 70% of respirable fraction could be prepared. The ME was efficiently recovered in simulated lung fluid even after removal of alcohol. The concurrent delivery of AVT with TPGS in solid SMEDDS greatly enhanced the cytotoxic activity on lung cancer cells.

In vitro dissolution of uranium-contaminated soil in simulated lung fluid containing a pulmonary surfactant.

During the latter part of the twentieth century, the United States developed a highly technical nuclear weapons complex that involved workers at many facilities performing complex missions at a number of different industrial sites across the country. Now, many of these sites are being remediated to remove legacy materials including chemical and radioactive wastes. Along with remediation comes the responsibility to adequately assess risk to cleanup workers who could be exposed to any hazardous materials, including resuspended uranium dust, encountered during environmental restoration. Inhalation of resuspended uranium represents one of the exposure hazards at an abandoned former metal rolling mill where approximately 11 thousand tons of uranium metal was rolled between 1947 and 1958. Residual uranium contamination in the dirt floor of this abandoned site has been exposed to rain, ice, snow, and other environmental factors for more than 50 y. This report describes the solubility of the uranium contamination in this dirt measured in vitro using a modified recipe for simulated lung fluid that contains a pulmonary surfactant. Small (0.1 g) aliquots of dirt collected at this site were sequentially dissolved in simulated lung fluid for increasing periods of time up to 30 d. Solubility was classified according to the ICRP categories as fast, medium, and slow. Results demonstrate that the solubility designation for the uranium contamination in the dirt is approximately 50% fast, 15% medium, and 35-40% slow. There was no observed difference in solubility when a pulmonary surfactant was added to the simulated lung fluid.

Ceramic Refractory Compositions with Biosolubility Characteristics

ABSTRACTIn this work, we studied the dissolution of three different refractory compositions belonging to the ternary system SiO2-CaO-MgO into two Simulated Lung Fluids (SLF). The initial powder mixtures were uniaxially pressed and then sintered at 1300-1400 °C. The sintered samples were immersed for times from 1 to 21 days into a given SLF at 37 °C. The samples were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The dissolution of Ca2+, Mg2+ and Si4+ into the SLF was quantified by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The in vitro studies suggested that all the considered materials had a potential to show a diminished biopersistence in vivo, due to reasons that depended on their chemical and phase composition.

Glutathione-S-transferase: a minor allergen in birch pollen due to limited release from hydrated pollen.

BackgroundRecently, a protein homologous to glutathione-S-transferases (GST) was detected in prominent amounts in birch pollen by proteomic profiling. As members of the GST family are relevant allergens in mites, cockroach and fungi we investigated the allergenic relevance of GST from birch (bGST).MethodologybGST was expressed in Escherichia coli, purified and characterized by mass spectrometry. Sera from 217 birch pollen-allergic patients were tested for IgE-reactivity to bGST by ELISA. The mediator-releasing activity of bGST was analysed with IgE-loaded rat basophil leukaemia cells (RBL) expressing human FcεRI. BALB/c mice were immunized with bGST or Bet v 1. Antibody and T cell responses to either protein were assessed. IgE-cross-reactivity between bGST with GST from house dust mite, Der p 8, was studied with murine and human sera in ELISA. The release kinetics of bGST and Bet v 1 from birch pollen were assessed in water, simulated lung fluid, 0.9% NaCl and PBS. Eluted proteins were quantified by ELISA and analysed by immunoblotting.Principle findingsOnly 13% of 217 birch pollen-allergic patients showed IgE-reactivity to bGST. In RBL assays bGST induced mediator release. Immunization of mice with bGST induced specific IgE and a Th2-dominated cellular immune response comparably to immunization with Bet v 1. bGST did not cross-react with Der p 8. In contrast to Bet v 1, only low amounts of bGST were released from pollen grains upon incubation in water and the different physiological solutions.Conclusion/SignificanceAlthough bGST is abundant in birch pollen, immunogenic in mice and able to induce mediator release from effector cells passively loaded with specific IgE, it is a minor allergen for birch pollen-allergic patients. We refer this discrepancy to its limited release from hydrated pollen. Hence, bGST is an example demonstrating that allergenicity depends mainly on rapid elution from airborne particles.

Evaluation of bioaccessible heavy metal fractions in PM10 from the metropolitan region of Rio de Janeiro city, Brazil, using a simulated lung fluid

Bioaccessibility studies are important for the estimation of the potential effects on human health caused by metals present in inhalable airborne particulate matter (APM) since their chemical forms determine whether the metals are biologically available. In this work, 24-hPM10 samples from four sampling stations (Bonsucesso, Botafogo, Centro and Nova Iguaçu) of the metropolitan region of Rio de Janeiro city (MRRJ), collected in the winter of 2010, were exposed to a simulated lung fluid 3.5 times less saline (TDS=2922mgL−1) than the Gamble's solution (TDS of approximately 10,200mgL−1). The use of a low salt solution had the advantage of preventing damage to the skimmer and/or nebulizer of the inductively coupled plasma (ICP) spectrometer. A certified reference material of urban particulate matter (NIST 1648a) was also analyzed. A set of various heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) was investigated. The use of a less saline fluid showed to be adequate to estimate the pulmonary bioaccessibility of Cd and Co. On the other hand, this procedure could underestimate the bioaccessibility of Cu, Mn, Ni, Pb and Zn. The bioaccessible metal concentrations obtained at all stations varied in a large range from 0.04μgg−1 (for Cd at Centro station) to 115μgg−1 (for Fe at Bonsucesso station) whereas the bioaccessibility varied from 1.1% (for Cr at Botafogo station) to 93% (for Cd at Centro station). The results indicated that the inhalation of bioaccessible metals found in the APM samples of the Rio de Janeiro city probably has an important contribution to the serious respiratory illnesses reported in this city.

Oral bioaccessibility and human exposure to anthropogenic and geogenic mercury in urban, industrial and mining areas

The objective of this study was to characterize the link between bioaccessibility and fractionation of mercury (Hg) in soils and to provide insight into human exposure to Hg due to inhalation of airborne soil particles and hand-to-mouth ingestion of Hg-bearing soil. Mercury in soils from mining, urban and industrial areas was fractionated in organometallic forms; mobile; semi-mobile; and non-mobile forms as well as HCl-extractable Hg. The in vitro bioaccessibility of Hg was obtained by extracting soils with (1) a simulated human gastric fluid (pH1.5), and (2) a simulated human lung fluid (pH7.4). Total soil Hg concentrations ranged from 0.72 to 1.8mgkg−1 (urban areas), 0.28 to 94mgkg−1 (industrial area) and 0.92 to 37mgkg−1 (mining areas). Both organometallic Hg as well as 0.1M HCl extractable Hg were lower (<0.5% of total Hg) than Hg extracted by gastric fluid (up to 1.8% of total Hg) and lung fluid (up to 12% of total Hg). In addition, Hg extracted by lung fluid was significantly higher in urban and industrial soils (average 5.0–6.6% of total Hg) compared to mining soils. Such differences were related to levels of mobile Hg species in urban and industrial soils compared to mining soils. These results strengthen the need to measure site-specific Hg fractionation when determining Hg bioaccessibility. Results also show that ingestion and/or inhalation of Hg from soil particles can contribute up to 8% of adult total Hg intake when compared to total Hg intake via consumption of contaminated fish and animal products from contaminated areas.

Antibiotic-free nanotherapeutics: Ultra-small, mucus-penetrating solid lipid nanoparticles enhance the pulmonary delivery and anti-virulence efficacy of novel quorum sensing inhibitors

Cystic fibrosis (CF) is a genetic disease mainly manifested in the respiratory tract. Pseudomonas aeruginosa (P. aeruginosa) is the most common pathogen identified in cultures of the CF airways, however, its eradication with antibiotics remains challenging as it grows in biofilms that counterwork human immune response and dramatically decrease susceptibility to antibiotics. P. aeruginosa regulates pathogenicity via a cell-to-cell communication system known as quorum sensing (QS) involving the virulence factor (pyocyanin), thus representing an attractive target for coping with bacterial pathogenicity. The first in vivo potent QS inhibitor (QSI) was recently developed. Nevertheless, its lipophilic nature might hamper its penetration of non-cellular barriers such as mucus and bacterial biofilms, which limits its biomedical application. Successful anti-infective inhalation therapy necessitates proper design of a biodegradable nanocarrier allowing: 1) high loading and prolonged release, 2) mucus penetration, 3) effective pulmonary delivery, and 4) maintenance of the anti-virulence activity of the QSI. In this context, various pharmaceutical lipids were used to prepare ultra-small solid lipid nanoparticles (us-SLNs) by hot melt homogenization. Plain and QSI-loaded SLNs were characterized in terms of colloidal properties, drug loading, in vitro release and acute toxicity on Calu-3 cells. Mucus penetration was studied using a newly-developed confocal microscopy technique based on 3D-time-lapse imaging. For pulmonary application, nebulization efficiency of SLNs and lung deposition using next generation impactor (NGI) were performed. The anti-virulence efficacy was investigated by pyocyanin formation in P. aeruginosa cultures. Ultra-small SLNs (<100nm diameter) provided high encapsulation efficiency (68-95%) according to SLN composition, high burst in phosphate buffer saline compared to prolonged release of the payload over >8h in simulated lung fluid with minor burst. All types and concentrations of plain and QSI-loaded SLNs maintained the viability of Calu-3 cells. 3D time-lapse confocal imaging proved the ability of SLNs to penetrate into artificial sputum model. SLNs were efficiently nebulized; NGI experiments revealed their deposition in the bronchial region. Overall, nanoencapsulated QSI showed up to sevenfold superior anti-virulence activity to the free compound. Most interestingly, the plain SLNs exhibited anti-virulence properties themselves, which was shown to be related to anti-virulence effects of the emulsifiers used. These startling findings represent a new perspective of ultimate significance in the area of nano-based delivery of novel anti-infectives.

RIFAMPICIN LOADED SPRAY-DRIED OLIBANUM GUM RESIN PULMOSPHERES FOR LUNG DELIVERY

Pulmospheres of Rifampicin were prepared successfully with cyclodextrin using olibanum gum resin as a rate controlling biodegradable natural polymer by novel spray drying technique. Hydroxypropyl-β-cyclodextrin was used as solubilising agent to enhance the solubility and permeation of poorly soluble rifampicin. The physcochemical characteristics of  rifampicin loaded pulmospheres were evaluated for mean particle size, thermal behaviour and surface morphology. The mean particle size for optimized formulation F1 was found to be 3.5 µm and spray-dried pure rifampicin also showed same value. Scanning Electron Microphotographs of pure drug has shown a typical and regular size indicated crystalline nature, whereas, spray dried pure drug and formulation F1 have shown spherical particles with porous surface indicated the conversion of crystalline drug into amorphous form. Rifampicin loaded spray-dried pulmospheres using olibanum gum resin showed drug release up to 72 hours. The release of rifampicin was greater in simulated physiological fluid of pH 7.4 which was 94 % as compared to simulated lung fluid of pH 5.2 at the end of 72 hours. Rifampicin loaded spray-dried microspheres were proposed for pulmonary drug delivery.  Keywords: Rifampicin, Lung targeting, Olibanum gum resin, Spray-drying, Pulmospheres

Development and application of an inhalation bioaccessibility method (IBM) for lead in the PM10 size fraction of soil

An approach for assessing the inhalation bioaccessibility of Pb in the PM10 size fraction is presented, using an in vitro simulated epithelial lung fluid to represent the extracellular environment of the lung. The developed inhalation bioaccessibility method (IBM) is applied to a range of urban surface soils and mining wastes obtained from Mitrovica, Kosovo, a site where impacts upon human health following exposure to Pb have been internationally publicised. All Pb determinations were undertaken by inductively coupled plasma mass spectrometry (ICP-MS). The pseudo-total concentration of Pb (microwave acid digestion using aqua-regia) varied between matrices: smelter (20,900–72,800mgkg−1), topsoil (274–13,700mgkg−1), and tailings (2990mgkg−1–25,300mgkg−1). The in vitro inhalation bioaccessibility was typically several orders of magnitude lower: smelter (7.0–965mgkg−1), topsoil (9.8–1060mgkg−1), and tailings (0.7mgkg−1–49.2mgkg−1). The % inhalation bioaccessibility ranged from 0.02 to 11.0%, with the higher inhalation bioaccessible Pb concentrations being observed for samples from the Bosniak Mahalla area of Mitrovica (an area proposed for the relocation of internally displaced peoples). The estimated inhalation dose (for adults) calculated from the PM10 pseudo-total Pb concentration ranged from 0.369 to 1.284μgkg−1BWday−1 (smelter), 0.005–0.242μgkg−1BWday−1 (topsoil), and 0.053–0.446μgkg−1BWday−1 (tailings). When daily inhalation doses were calculated using the bioaccessible Pb concentration the modelled exposure doses were much lower: smelter (0.0001–0.0170μgkg−1BWday−1), topsoil (0.0002–0.0187μgkg−1BWday−1) and tailings (0.0001–0.0009μgkg−1BWday−1). Modelled for the neutral pH conditions of the interstitial lung environment, the results indicate a low potential inhalation bioaccessibility for Pb in these samples. Given the already elevated environmental Pb burden experienced by the local population, where significant prolonged dust or particulate generating activities are taking place, or where the inhaled particles are phagocytized, then inhalation exposure has the potential to significantly add to the overall Pb burden. Such data are important for local policy makers to better enable them to assess risk, especially in areas where soils/dusts have elevated levels of contamination.

Preparation and characterization of controlled release poly-ɛ-caprolactone microparticles of isoniazid for drug delivery through pulmonary route

In the present investigation inhaled isoniazid microparticles (IM) and isoniazid polymeric microparticles (INH-PM) using poly-ɛ-caprolactone polymer were prepared through spray drying techniques. The purpose of this investigation is to evaluate lung deposition of IM and INH-PM through cascade impaction study. The drug release of IM and INH-PM was studied using simulated lung fluids at pH7.4 representing the interstitial site and at pH4.5 representing phagocomal site after alveolar macrophage uptake. The kinetic models had also been applied providing the drug release kinetics for IM and INH-PM in simulated lung fluids at pH7.4 and at pH4.5. The results of the particles size and surface characteristics showed the spherical shape and 1–5μm size of IM and INH-PM prepared using spray drying which can be suitable for pulmonary drug delivery. The cascade impaction study with mass median aerodynamic diameter ranging from 1.9 to 4μm confirmed the inhaled characteristics of IM and INH-PM with providing the deep lung deposition where tubercular bacilli reside. From in vitro drug release studies done using simulated lung fluids and goodness of fit with kinetic model applications, it can be concluded that the prepared poly-ɛ-caprolactone microparticles of isoniazid provided the advantage of controlled release characteristics deep inside the lung where tubercular bacilli reside and as suitable for pulmonary drug delivery it may help in improving treatment of tuberculosis through direct administration to site of action.

Dust from Zambian smelters: mineralogy and contaminant bioaccessibility.

Metal smelting is often responsible for local contamination of environmental compartments. Dust materials escaping from the smelting facilities not only settle in the soil, but can also have direct effects on populations living close to these operations (by ingestion or inhalation). In this particular study, we investigate dusts from Cu-Co metal smelters in the Zambian Copperbelt, using a combination of mineralogical techniques (XRD, SEM/EDS, and TEM/EDS), in order to understand the solid speciation of the contaminants, as well as their bioaccessibility using in vitro tests in simulated gastric and lung fluids to assess the exposure risk for humans. The leaching of metals was mainly dependent on the contaminant mineralogy. Based on our results, a potential risk can be recognized, particularly from ingestion of the dust, with bioaccessible fractions ranging from 21 to 89% of the total contaminant concentrations. In contrast, relatively low bioaccessible fractions were observed for simulated lung fluid extracts, with values ranging from 0.01% (Pb) up to 16.5% (Co) of total contaminant concentrations. Daily intakes via oral exposure, calculated for an adult (70 kg, ingestion rate 50 mg dust per day), slightly exceeded the tolerable daily intake limits for Co (1.66× for fly ash and 1.19× for slag dust) and occasionally also for Pb (1.49×, fly ash) and As (1.64×, electrostatic precipitator dust). Cobalt has been suggested as the most important pollutant, and the direct pathways of the population's exposures to dust particles in the industrial parts of the Zambian Copperbelt should be further studied in interdisciplinary investigations.

Characterizing metal(loid) solubility in airborne PM10, PM2.5 and PM1 in Frankfurt, Germany using simulated lung fluids

The purpose of this study is to assess the solubility of traffic-related metal(loid)s associated with airborne PM of human health concern, employing a physiologically-based extraction test with simulated lung fluids (artificial lysosomal fluid (ALF) and Gamble's solution). Airborne PM (PM10, PM2.5 and PM1) samples were collected in Frankfurt am Main, Germany, using a high volume sampler. Following extraction of the soluble metal(loid) fractions, sample filters were digested with a high pressure asher. Metal(loid) concentrations (As, Ce, Co, Cr, Cu, Mn, Ni, Pb, Sb, Ti and V) were determined in extracts and digests per ICP-Q-MS.All metal(loid)s occurred at detectable concentrations in the three airborne PM fractions. Copper was the most abundant element in mass terms, with mean concentrations of 105 and 53 ng/m3 in PM10 and PM2.5, respectively. Many of the metal(loid)s were observed to be soluble in simulated lung fluids, with Cu, As, V and Sb demonstrating the highest overall mobility in airborne PM. For instance, all four elements associated with PM10 had a solubility of >80% in ALF (24 h). Clearly, solubility is strongly pH dependent, as reflected by the higher relative mobility of samples extracted with the acidic ALF.Given their demonstrated solubility, this study provides indirect evidence that a number of toxic metal(loid)s are likely to possess an enhanced pulmonary toxic potential upon their inhalation. The co-presence of many toxic elements of concern in airborne PM suggests an assessment of health risk must consider the possible interactive impacts of multi-element exposures.

Polymeric nanoparticles for pulmonary protein and DNA delivery

Polymeric nanoparticles (NPs) are promising carriers of biological agents to the lung due to advantages including biocompatibility, ease of surface modification, localized action and reduced systemic toxicity. However, there have been no studies extensively characterizing and comparing the behavior of polymeric NPs for pulmonary protein/DNA delivery both in vitro and in vitro. We screened six polymeric NPs: gelatin, chitosan, alginate, poly(lactic-co-glycolic) acid (PLGA), PLGA–chitosan and PLGA–poly(ethylene glycol) (PEG), for inhalational protein/DNA delivery. All NPs except PLGA–PEG and alginate were <300nm in size with a bi-phasic core compound release profile. Gelatin, PLGA NPs and PLGA–PEG NPs remained stable in deionized water, serum, saline and simulated lung fluid (Gamble’s solution) over 5days. PLGA-based NPs and natural polymer NPs exhibited the highest cytocompatibility and dose-dependent in vitro uptake, respectively, by human alveolar type-1 epithelial cells. Based on these profiles, gelatin and PLGA NPs were used to encapsulate plasmid DNA encoding yellow fluorescent protein (YFP) or rhodamine-conjugated erythropoietin (EPO) for inhalational delivery to rats. Following a single inhalation, widespread pulmonary EPO distribution persisted for up to 10days while increasing YFP expression was observed for at least 7days for both NPs. The overall results support both PLGA and gelatin NPs as promising carriers for pulmonary protein/DNA delivery.

Phase partitioning and bioaccessibility of Pb in suspended dust from unsurfaced roads in Missouri—A potential tool for determining mitigation response

Airborne particulate material collected from seventeen rural unsurfaced roads in Missouri's agricultural and resource mining areas were characterized using the BCR sequential extraction procedure and simulated in vitro body fluids to determine the phase partitioning and bioaccessibility of Pb associated with roadway dusts. Results show that dusts produced from driving over unsurfaced roads in the mining area has a substantial portion of the Pb concentration associated with the more mobile exchangeable-plus-carbonate and reducible geochemical phases. By comparison, unsurfaced road dusts outside the resource mining area have lower metal contents, as expected, and a larger portion of the total Pb concentration associated with the immobile oxidizable and non-silicate bound residual phases. SEM/EDS analysis suggests the minerals associated with the more mobile Pb components include cerussite, Pb oxides and sulfates. Compared with the coarser >1 μm size fraction of dust, the <1 μm fraction contains a substantially higher concentration of Pb in association with clay minerals. Extraction tests using simulated body fluids show that gastric fluid can mobilize as much as 69% of the total Pb concentration in mining area road dust samples after five hours. Simulated alveolar lung fluid also was an efficient extractor of Pb from the <1 μm sample dust fraction, dissolving up to 100% of the available Pb after 100 h. Regression analysis suggests that aqua regia total Pb concentration is a good predictor of mobility and bioaccessibility and can be used to minimize costs associated with monitoring suspended dust contamination.

Solubility of Nickel Nanoparticles in Simulated Body Fluids

The paper is dedicated to nickel nanoparticles dissolution in simulated body fluids. By the example of industrial electroexplosive nickel nanopowder it has been demonstrated that dissolution degree in simulated lung fluid and simulated saliva can reach 98.0 and 62.8 wt.% for 24 hours, respectively. The mechanism of nickel dissolution has been proposed. It includes the dissolution of energy saturated oxide film, formed in oxygen saturated simulated saliva, the formation of nickel hydroxycitrate in simulated lung fluid as well.