Quantitative biokinetics over a 28 day period of freshly generated, pristine, 20 nm silver nanoparticle aerosols in healthy adult rats after a single 1½-hour inhalation exposure.

BACKGROUND: There is a steadily increasing quantity of silver nanoparticles (AgNP) produced for numerous industrial, medicinal and private purposes, leading to an increased risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure. RESULTS: To study the fate of inhaled AgNP, healthy adult rats were exposed to 1½-hour intra-tracheal inhalations of pristine 105Ag-radiolabeled, 20 nm AgNP aerosols (with mean doses across all rats of each exposure group of deposited NP-mass and NP-number being 13.5 ± 3.6 µg, 7.9 ± 3.2•1011, respectively). At five time-points (0.75 h, 4 h, 24 h, 7d, 28d) post-exposure (p.e.), a complete balance of the [105Ag]AgNP fate and its degradation products were quantified in organs, tissues, carcass, lavage and body fluids, including excretions. Rapid dissolution of [105Ag]Ag-ions from the [105Ag]AgNP surface was apparent together with both fast particulate airway clearance and long-term particulate clearance from the alveolar region to the larynx. The results are compatible with evidence from the literature that the released [105Ag]Ag-ions precipitate rapidly to low-solubility [105Ag]Ag-salts in the ion-rich epithelial lining lung fluid (ELF) and blood. Based on the existing literature, the degradation products rapidly translocate across the air-blood-barrier (ABB) into the blood and are eliminated via the liver and gall-bladder into the small intestine for fecal excretion. The pathway of [105Ag]Ag-salt precipitates was compatible with auxiliary biokinetics studies at 24 h and 7 days after either intravenous injection or intratracheal or oral instillation of [110mAg]AgNO3 solutions in sentinel groups of rats. However, dissolution of [105Ag]Ag-ions appeared not to be complete after a few hours or days but continued over two weeks p.e. This was due to the additional formation of salt layers on the [105Ag]AgNP surface that mediate and prolonge the dissolution process. The concurrent clearance of persistent cores of [105Ag]AgNP and [105Ag]Ag-salt precipitates results in the elimination of a fraction > 0.8 (per ILD) after one week, each particulate Ag-species accounting for about half of this. After 28 days p.e. the cleared fraction rises marginally to 0.94 while 2/3 of the remaining [105Ag]AgNP are retained in the lungs and 1/3 in secondary organs and tissues with an unknown partition of the Ag species involved. However, making use of our previous biokinetics studies of poorly soluble [195Au]AuNP of the same size and under identical experimental and exposure conditions (Kreyling et al., ACS Nano 2018), the kinetics of the ABB-translocation of [105Ag]Ag-salt precipitates was estimated to reach a fractional maximum of 0.12 at day 3 p.e. and became undetectable 16 days p.e. Hence, persistent cores of [105Ag]AgNP were cleared throughout the study period. Urinary [105Ag]Ag excretion is minimal, finally accumulating to 0.016. CONCLUSION: The biokinetics of inhaled [105Ag]AgNP is relatively complex since the dissolving [105Ag]Ag-ions (a) form salt layers on the [105Ag]AgNP surface which retard dissolution and (b) the [105Ag]Ag-ions released from the [105Ag]AgNP surface form poorly-soluble precipitates of [105Ag]Ag-salts in ELF. Therefore, hardly any [105Ag]Ag-ion clearance occurs from the lungs but instead [105Ag]AgNP and nano-sized precipitated [105Ag]Ag-salt are cleared via the larynx into GIT and, in addition, via blood, liver, gall bladder into GIT with one common excretional pathway via feces out of the body.

Quantitative biokinetics over a 28 day period of freshly generated, pristine, 20 nm titanium dioxide nanoparticle aerosols in healthy adult rats after a single two-hour inhalation exposure.

BACKGROUND: Industrially produced quantities of TiO2 nanoparticles are steadily rising, leading to an increasing risk of inhalation exposure for both professionals and consumers. Particle inhalation can result in inflammatory and allergic responses, and there are concerns about other negative health effects from either acute or chronic low-dose exposure. RESULTS: To study the fate of inhaled TiO2-NP, adult rats were exposed to 2-h intra-tracheal inhalations of 48V-radiolabeled, 20 nm TiO2-NP aerosols (deposited NP-mass 1.4 ± 0.5 µg). At five time points (1 h, 4 h, 24 h, 7d, 28d) post-exposure, a complete balance of the [48V]TiO2-NP fate was quantified in organs, tissues, carcass, lavage and body fluids, including excretions. After fast mucociliary airway clearance (fractional range 0.16-0.31), long-term macrophage-mediated clearance (LT-MC) from the alveolar region is 2.6-fold higher after 28d (integral fraction 0.40 ± 0.04) than translocation across the air-blood-barrier (integral fraction 0.15 ± 0.01). A high NP fraction remains in the alveoli (0.44 ± 0.05 after 28d), half of these on the alveolar epithelium and half in interstitial spaces. There is clearance from both retention sites at fractional rates (0.02-0.03 d- 1) by LT-MC. Prior to LT-MC, [48V]TiO2-NP are re-entrained to the epithelium as reported earlier for 20 nm inhaled gold-NP (AuNP) and iridium-NP (IrNP). CONCLUSION: Comparing the 28-day biokinetics patterns of three different inhaled NP materials TiO2-NP, AuNP and IrNP, the long-term kinetics of interstitial relocation and subsequent re-entrainment onto the lung-epithelium is similar for AuNP and Ir-NP but slower than for TiO2-NP. We discuss mechanisms and pathways of NP relocation and re-entrainment versus translocation. Additionally, after 28 days the integral translocated fractions of TiO2-NP and IrNP across the air-blood-barrier (ABB) are similar and become 0.15 while the translocated AuNP fraction is only 0.04. While NP dissolution proved negligible, translocated TiO2-NP and IrNP are predominantly excreted in urine (~ 0.1) while the urinary AuNP excretion amounts to a fraction of only 0.01. Urinary AuNP excretion is below 0.0001 during the first week but rises tenfold thereafter suggesting delayed disagglomeration. Of note, all three NP dissolve minimally, since no ionic radio-label release was detectable. These biokinetics data of inhaled, same-sized NP suggest significant time-dependent differences of the ABB translocation and subsequent fate in the organism.

Size dependent translocation and fetal accumulation of gold nanoparticles from maternal blood in the rat.

BACKGROUND: There is evidence that nanoparticles (NP) cross epithelial and endothelial body barriers. We hypothesized that gold (Au) NP, once in the blood circulation of pregnant rats, will cross the placental barrier during pregnancy size-dependently and accumulate in the fetal organism by 1. transcellular transport across the hemochorial placenta, 2. transcellular transport across amniotic membranes 3. transport through ~20 nm wide transtrophoblastic channels in a size dependent manner. The three AuNP sizes used to test this hypothesis are either well below, or of similar size or well above the diameters of the transtrophoblastic channels. METHODS: We intravenously injected monodisperse, negatively charged, radio-labelled 1.4 nm, 18 nm and 80 nm ¹98AuNP at a mass dose of 5, 3 and 27 µg/rat, respectively, into pregnant rats on day 18 of gestation and in non-pregnant control rats and studied the biodistribution in a quantitative manner based on the radio-analysis of the stably labelled ¹98AuNP after 24 hours. RESULTS: We observed significant biokinetic differences between pregnant and non-pregnant rats. AuNP fractions in the uterus of pregnant rats were at least one order of magnitude higher for each particle size roughly proportional to the enlarged size and weight of the pregnant uterus. All three sizes of ¹98AuNP were found in the placentas and amniotic fluids with 1.4 nm AuNP fractions being two orders of magnitude higher than those of the larger AuNP on a mass base. In the fetuses, only fractions of 0.0006 (30 ng) and 0.00004 (0.1 ng) of 1.4 nm and 18 nm AuNP, respectively, were detected, but no 80 nm AuNP (<0.000004 (<0.1 ng)). These data show that no AuNP entered the fetuses from amniotic fluids within 24 hours but indicate that AuNP translocation occurs across the placental tissues either through transtrophoblastic channels and/or via transcellular processes. CONCLUSION: Our data suggest that the translocation of AuNP from maternal blood into the fetus is NP-size dependent which is due to mechanisms involving (1) transport through transtrophoblastic channels - also present in the human placenta - and/or (2) endocytotic and diffusive processes across the placental barrier.

Serum protein identification and quantification of the corona of 5, 15 and 80 nm gold nanoparticles.

When nanoparticles (NP) enter the body they come into contact with body fluids containing proteins which can adsorb to their surface. These proteins may influence the NP interactions with the biological vicinity, eventually determining their biological fate inside the body. Adsorption of the most abundantly binding proteins was studied after an in vitro 24 hr incubation of monodisperse, negatively charged 5, 15 and 80 nm gold spheres (AuNP) in mouse serum by a two-step analysis: proteomic protein identification and quantitative protein biochemistry. The adsorbed proteins were separated from non-adsorbed proteins by centrifugation and gel electrophoresis and identified using a MALDI-TOF-MS-Proteomics-Analyzer. Quantitative analysis of proteins in gel bands by protein densitometry, required the focus on predominantly binding serum proteins. Numerous proteins adsorbed to the AuNP depending on their size, e.g., apolipoproteins or complement C3. The qualitative and quantitative amount of adsorbed proteins differed between 5, 15 and 80 nm AuNP. Band intensities of adsorbed proteins decreased with increasing AuNP sizes based not only on their mass but also on their surface area. Summarizing, the AuNP surface is covered with serum proteins containing transport and immune related proteins among others. Hence, protein binding depends on the size, surface area and curvature of the AuNP.

Cellular uptake and localization of inhaled gold nanoparticles in lungs of mice with chronic obstructive pulmonary disease.

BACKGROUND: Inhalative nanocarriers for local or systemic therapy are promising. Gold nanoparticles (AuNP) have been widely considered as candidate material. Knowledge about their interaction with the lungs is required, foremost their uptake by surface macrophages and epithelial cells. METHODS: Scnn1b-Tg and Wt mice inhaled a 21-nm AuNP aerosol for 2 h. Immediately (0 h) or 24 h thereafter, bronchoalveolar lavage (BAL) macrophages and whole lungs were prepared for stereological analysis of AuNP by electron microscopy. RESULTS: AuNP were mainly found as singlets or small agglomerates of ≤ 100 nm diameter, at the epithelial surface and within lung-surface structures. Macrophages contained also large AuNP agglomerates (> 100 nm). At 0 h after aerosol inhalation, 69.2±4.9% AuNP were luminal, i.e. attached to the epithelial surface and 24.0±5.9% in macrophages in Scnn1b-Tg mice. In Wt mice, 35.3±32.2% AuNP were on the epithelium and 58.3±41.4% in macrophages. The percentage of luminal AuNP decreased from 0 h to 24 h in both groups. At 24 h, 15.5±4.8% AuNP were luminal, 21.4±14.2% within epithelial cells and 63.0±18.9% in macrophages in Scnn1b-Tg mice. In Wt mice, 9.5±5.0% AuNP were luminal, 2.2±1.6% within epithelial cells and 82.8±0.2% in macrophages. BAL-macrophage analysis revealed enhanced AuNP uptake in Wt animals at 0 h and in Scnn1b-Tg mice at 24 h, confirming less efficient macrophage uptake and delayed clearance of AuNP in Scnn1b-Tg mice. CONCLUSIONS: Inhaled AuNP rapidly bound to the alveolar epithelium in both Wt and Scnn1b-Tg mice. Scnn1b-Tg mice showed less efficient AuNP uptake by surface macrophages and concomitant higher particle internalization by alveolar type I epithelial cells compared to Wt mice. This likely promotes AuNP depth translocation in Scnn1b-Tg mice, including enhanced epithelial targeting. These results suggest AuNP nanocarrier delivery as successful strategy for therapeutic targeting of alveolar epithelial cells and macrophages in COPD.

Binding of polystyrene and carbon black nanoparticles to blood serum proteins.

CONTEXT: Once inhaled, nanoparticles (NP) deposit on the lung surface and have first contact with the epithelial lung lining fluid (ELF) rich in proteins, which may bind to NP. OBJECTIVE: In this study, we investigate the parameters that influence the binding between NP and proteins. MATERIALS AND METHODS: We used the proteins albumin, transferrin (TF), and apolipoprotein A-1 (all known as proteins from ELF) and different NP (polystyrene NP with negative, positive, and neutral surface coatings, Printex G and Printex 90) as models. RESULTS: In all cases, a linear correlation of the added NP amount and the amount of bound proteins was found and was described quantitatively by binding indices. Bovine serum albumin (BSA), TF, and apo A-1 were bound to the largest extent to hydrophobic NP, which shows the extraordinary importance of the NP's surface properties. DISCUSSION: The binding index indicates the relevance of primary particle size and surface properties, including hydrophobicity. CONCLUSION: Size and surface modifications of NP determine their protein binding. Our results suggest that the formation of conjugates of BSA, TF, and Apo A-1 with NP may play an important role in their translocation across the air-blood-barrier and subsequent biokinetics.

Size dependence of the translocation of inhaled iridium and carbon nanoparticle aggregates from the lung of rats to the blood and secondary target organs.

Currently, translocation of inhaled insoluble nanoparticles (NP) across membranes like the air-blood barrier into secondary target organs (STOs) is debated. Of key interest are the involved biological mechanisms and NP parameters that determine the efficiency of translocation. We performed NP inhalation studies with rats to derive quantitative biodistribution data on the translocation of NP from lungs to blood circulation and STOs. The inhaled NP were chain aggregates (and agglomerates) of either iridium or carbon, with primary particle sizes of 2-4 nm (Ir) and 5-10 nm (C) and aggregate sizes (mean mobility diameters) between 20 and 80 nm. The carbon aggregates contained a small fraction ( < 1%) of Ir primary particles. The insoluble aggregates were radiolabeled with (192)Ir. During 1 h of inhalation, rats were intubated and ventilated to avoid extrathoracic NP deposition and to optimize deep lung NP deposition. After 24 h, (192)Ir fractions in the range between 0.001 and 0.01 were found in liver, spleen, kidneys, heart, and brain, and an even higher fraction (between 0.01 and 0.05) in the remaining carcass consisting of soft tissue and bone. The fractions of (192)Ir carried with the carbon NP retained in STOs, the skeleton, and soft tissue were significantly lower than with NP made from pure Ir. Furthermore, there was significantly less translocation and accumulation with 80-nm than with 20-nm NP aggregates of Ir. These studies show that both NP characteristics--the material and the size of the chain-type aggregates--determine translocation and accumulation in STOs, skeleton, and soft tissue.

Age-Dependent Rat Lung Deposition Patterns of Inhaled 20 Nanometer Gold Nanoparticles and their Quantitative Biokinetics in Adult Rats.

The increasing use of gold nanoparticles leads to a possible increase of exposure by inhalation. Therefore, we have studied the deposition patterns of inhaled 20 nm gold nanoparticles (AuNP) in 7-90 day old rats and their biokinetics in 60 day old ones. Wistar-Kyoto rats inhaled intratracheally 20 nm 195Au-radiolabeled AuNP by negative pressure ventilation over 2 h. Immediately afterward lungs were excised, inflated and microwave dried. AuNP deposition was analyzed by single-photon emission computed tomography, computed-tomography and autoradiography. Completely balanced, quantitative biodistributions in major organs and all body tissues and total excretion were analyzed from 1 h to 28 d after inhalation. Intratracheal inhalation caused AuNP deposition predominately in the caudal lungs, independent of age. About 30% AuNP were deposited on airway epithelia and rapidly cleared by mucociliary clearance. About 80% of AuNP deposited in alveoli was relocated from the epithelium into the interstitium within 24 h and was inaccessible to broncho-alveolar lavage. During interstitial long-term retention, re-entrainment within macrophages back onto the lung epithelium and to the larynx and gastrointestinal tract (GIT) dominated AuNP clearance (rate 0.03 d-1) In contrast, AuNP-translocation across the air-blood barrier was much smaller leading to persistent retention in secondary organs and tissues in the ranking order liver > soft issue > spleen > kidneys > skeleton > blood > uterus > heart > brain. The age-independent, inhomogeneous AuNP deposition was probably caused by the negative pressure ventilation. Long-term AuNP clearance was dominated by macrophage-mediated transport from the interstitium to the larynx and GIT. Translocation across the rat air-blood barrier appeared to be similar to that of humans for similar sized AuNP.

Efficient elimination of inhaled nanoparticles from the alveolar region: evidence for interstitial uptake and subsequent reentrainment onto airways epithelium.

BACKGROUND: There is ongoing discussion that inhaled nanoparticles (NPs, < 100 nm) may translocate from epithelial deposition sites of the lungs to systemic circulation. OBJECTIVES AND METHODS: We studied the disappearance of NPs from the epithelium by sequential lung retention and clearance and bronchoalveolar lavage (BAL) measurements in healthy adult Wistar Kyoto (WKY) rats at various times over 6 months after administration of a single 60- to 100-min intratracheal inhalation of iridium-192 ((192)Ir)-radiolabeled NPs. A complete (192)Ir balance of all organs, tissues, excretion, remaining carcass, and BAL was performed at each time point. RESULTS: Directly after inhalation we found free NPs in the BAL; later, NPs were predominantly associated with alveolar macropages (AMs). After 3 weeks, lavageable NP fractions decreased to 0.06 of the actual NP lung burden. This is in stark contrast to the AM-associated fraction of micron-sized particles reported in the literature. These particles remained constant at about 0.8 throughout a 6-month period. Three weeks after inhalation, 80% of the retained Ir NPs was translocated into epithelium and interstitium. CONCLUSION: There is a strong size-selective difference in particle immobilization. Furthermore, AM-mediated NP transport to the larynx originates not only from the NP fraction retained on the epithelium but also from NPs being reentrained from the interstitium to the luminal side of epithelium. We conclude that NPs are much less phagocytized by AMs than large particles but are effectively removed from the lung surface into the interstitium. Even from these interstitial sites, they undergo AM-mediated long-term NP clearance to the larynx.

Quantitative biokinetics of titanium dioxide nanoparticles after intravenous injection in rats: Part 1.

Submicrometer TiO2 particles, including nanoparticulate fractions, are used in an increasing variety of consumer products, as food additives and also drug delivery applications are envisaged. Beyond exposure of occupational groups, this entails an exposure risk to the public. However, nanoparticle translocation from the organ of intake and potential accumulation in secondary organs are poorly understood and in many investigations excessive doses are applied. The present study investigates the biokinetics and clearance of a low single dose (typically 40-400 µg/kg BW) of 48V-radiolabeled, pure TiO2 anatase nanoparticles ([48V]TiO2NP) with a median aggregate/agglomerate size of 70 nm in aqueous suspension after intravenous (IV) injection into female Wistar rats. Biokinetics and clearance were followed from one-hour to 4-weeks. The use of radiolabeled nanoparticles allowed a quantitative [48V]TiO2NP balancing of all organs, tissues, carcass and excretions of each rat without having to account for chemical background levels possibly caused by dietary or environmental titanium exposure. Highest [48V]TiO2NP accumulations were found in liver (95.5%ID after one day), followed by spleen (2.5%), carcass (1%), skeleton (0.7%) and blood (0.4%). Detectable nanoparticle levels were found in all other organs. The [48V]TiO2NP content in blood decreased rapidly after 24 h while the distribution in other organs and tissues remained rather constant until day-28. The present biokinetics study is part 1 of a series of studies comparing biokinetics after three classical routes of intake (IV injection (part 1), ingestion (part 2), intratracheal instillation (part 3)) under identical laboratory conditions, in order to test the common hypothesis that IV-injection is a suitable predictor for the biokinetics fate of nanoparticles administered by different routes. This hypothesis is disproved by this series of studies.

Quantitative biokinetics of titanium dioxide nanoparticles after oral application in rats: Part 2.

The biokinetics of a size-selected fraction (70 nm median size) of commercially available and 48V-radiolabeled [48V]TiO2 nanoparticles has been investigated in female Wistar-Kyoto rats at retention timepoints 1 h, 4 h, 24 h and 7 days after oral application of a single dose of an aqueous [48V]TiO2-nanoparticle suspension by intra-esophageal instillation. A completely balanced quantitative body clearance and biokinetics in all organs and tissues was obtained by applying typical [48V]TiO2-nanoparticle doses in the range of 30-80 µg•kg-1 bodyweight, making use of the high sensitivity of the radiotracer technique. The [48V]TiO2-nanoparticle content was corrected for nanoparticles in the residual blood retained in organs and tissue after exsanguination and for 48V-ions not bound to TiO2-nanoparticles. Beyond predominant fecal excretion about 0.6% of the administered dose passed the gastro-intestinal-barrier after one hour and about 0.05% were still distributed in the body after 7 days, with quantifiable [48V]TiO2-nanoparticle organ concentrations present in liver (0.09 ng•g-1), lungs (0.10 ng•g-1), kidneys (0.29 ng•g-1), brain (0.36 ng•g-1), spleen (0.45 ng•g-1), uterus (0.55 ng•g-1) and skeleton (0.98 ng•g-1). Since chronic, oral uptake of TiO2 particles (including a nano-fraction) by consumers has continuously increased in the past decades, the possibility of chronic accumulation of such biopersistent nanoparticles in secondary organs and the skeleton raises questions about the responsiveness of their defense capacities, and whether these could be leading to adverse health effects in the population at large. After normalizing the fractions of retained [48V]TiO2-nanoparticles to the fraction that passed the gastro-intestinal-barrier and reached systemic circulation, the biokinetics was compared to the biokinetics determined after IV-injection (Part 1). Since the biokinetics patterns differ largely, IV-injection is not an adequate surrogate for assessing the biokinetics after oral exposure to TiO2 nanoparticles.

Quantitative biokinetics of titanium dioxide nanoparticles after intratracheal instillation in rats: Part 3.

The biokinetics of a size-selected fraction (70 nm median size) of commercially available and 48V-radiolabeled [48V]TiO2 nanoparticles has been investigated in healthy adult female Wistar-Kyoto rats at retention time-points of 1 h, 4 h, 24 h, 7 d and 28 d after intratracheal instillation of a single dose of an aqueous [48V]TiO2-nanoparticle suspension. A completely balanced quantitative biodistribution in all organs and tissues was obtained by applying typical [48V]TiO2-nanoparticle doses in the range of 40-240 µg·kg-1 bodyweight and making use of the high sensitivity of the radiotracer technique. The [48V]TiO2-nanoparticle content was corrected for residual blood retained in organs and tissues after exsanguination and for 48V-ions not bound to TiO2-nanoparticles. About 4% of the initial peripheral lung dose passed through the air-blood-barrier after 1 h and were retained mainly in the carcass (4%); 0.3% after 28 d. Highest organ fractions of [48V]TiO2-nanoparticles present in liver and kidneys remained constant (0.03%). [48V]TiO2-nanoparticles which entered across the gut epithelium following fast and long-term clearance from the lungs via larynx increased from 5 to 20% of all translocated/absorbed [48V]TiO2-nanoparticles. This contribution may account for 1/5 of the nanoparticle retention in some organs. After normalizing the fractions of retained [48V]TiO2-nanoparticles to the fraction that reached systemic circulation, the biodistribution was compared with the biodistributions determined after IV-injection (Part 1) and gavage (GAV) (Part 2). The biokinetics patterns after IT-instillation and GAV were similar but both were distinctly different from the pattern after intravenous injection disproving the latter to be a suitable surrogate of the former applications. Considering that chronic occupational inhalation of relatively biopersistent TiO2-particles (including nanoparticles) and accumulation in secondary organs may pose long-term health risks, this issue should be scrutinized more comprehensively.

Biokinetic datasets of PEI F25-LMW complexed and non-complexed 32P-siRNA within different lung compartments.

Biokinetics data of lung-administered PEI F25-LMW/siRNA polyplexes within different lung compartments are presented. Thereby, at three different timepoints (1 h, 3 h, 8 h), the data was determined by calculations to the 32P-radioactivity in the whole mouse body. Additionally, data was optimized to the available PEI F25-LMW/siRNA polyplexes in the target organ and therefore normalized to the sum of all lung compartments. Methods, other biokinetics data and the discussion of the results are published in "Biokinetic studies of non-complexed siRNA versus nano-sized PEI F25-LMW/siRNA polyplexes following intratracheal instillation into mice" (Lipka et al., 2016 [1]).

Biokinetic studies of non-complexed siRNA versus nano-sized PEI F25-LMW/siRNA polyplexes following intratracheal instillation into mice.

Successful gene therapy requires stability and sufficient bioavailability of the applied drug at the site of action. In the case of RNA interference (RNAi), non-viral vectors play a promising role for delivering intact siRNA molecules. We selected a low molecular weight polyethyleneimine (PEI F25-LMW) and investigated the biokinetics of PEI F25-LMW/siRNA polyplexes in comparison to non-complexed siRNA molecules upon intratracheal application into mice. Additionally, a bronchoalveolar lavage was performed to locate the siRNA within the different lung compartments and to analyse possible inflammatory reactions. Liquid scintillation counting of a 32P-label was used to follow the siRNA within the whole body. During the complete observation time more than 75% of the applied dose was found at the target site. The complexation with PEI F25- LMW prevented the siRNA from being degraded and cleared and prolonged its retention time. A low inflammatory reaction was observed on the basis of cell differentiation. Taken together, PEI F25-LMW meets fundamental requirements on non-viral vectors for local pulmonary siRNA delivery.

In vivo integrity of polymer-coated gold nanoparticles.

Inorganic nanoparticles are frequently engineered with an organic surface coating to improve their physicochemical properties, and it is well known that their colloidal properties may change upon internalization by cells. While the stability of such nanoparticles is typically assayed in simple in vitro tests, their stability in a mammalian organism remains unknown. Here, we show that firmly grafted polymer shells around gold nanoparticles may degrade when injected into rats. We synthesized monodisperse radioactively labelled gold nanoparticles ((198)Au) and engineered an (111)In-labelled polymer shell around them. Upon intravenous injection into rats, quantitative biodistribution analyses performed independently for (198)Au and (111)In showed partial removal of the polymer shell in vivo. While (198)Au accumulates mostly in the liver, part of the (111)In shows a non-particulate biodistribution similar to intravenous injection of chelated (111)In. Further in vitro studies suggest that degradation of the polymer shell is caused by proteolytic enzymes in the liver. Our results show that even nanoparticles with high colloidal stability can change their physicochemical properties in vivo.

Blood protein coating of gold nanoparticles as potential tool for organ targeting.

Nanoparticles (NP) and nanoparticulated drug delivery promise to be the breakthrough for therapy in medicine but raise concerns in terms of nanotoxicity. We present quantitative murine biokinetics assays using polyelectrolyte-multilayer-coated gold NP (AuNP, core diameter 15 and 80 nm; (198)Au radio-labeled). Those were stably conjugated either with human serum albumin (alb-AuNP) or apolipoprotein E (apoE-AuNP), prior to intravenous injection. We compare the biokinetics of protein-AuNP-conjugates with citrate-stabilized AuNP (cit-AuNP). Biokinetics was complemented with histology in organs with high AuNP content using 15 nm double fluorescently-labeled alb-AuNP-conjugates. Protein conjugation massively reduced liver retention (alb-AuNP: 52%, apoE-AuNP: 72%, cit-AuNP: >95%, at 19 h and 48 h) when compared to cit-AuNP. The protein conjugates were retained in lungs (alb-AuNP (18%) and spleen (alb-AuNP (16%), apoE-AuNP (21%) at 19 h. Alb-AuNP show significantly increased fractions in lungs (factors: 60 (30 min); 111 (19 h); 235 (48 h) and brain (factors: 70 (30 min); 90 (19 h); >200 (48 h) compared to cit-AuNP (control) - or even to apoE-AuNP. The influence of protein conjugation on the biodistribution disappears for 80 nm AuNP comparing to control. Histologically, the 15 nm alb-AuNP are mainly located in the endothelium of brain, lungs, liver and kidneys after 30 min, while at 19 h they moved deeper into the parenchyma e.g. in hippocampus. Our study clearly suggests that stable conjugation of AuNP with albumin and apoE prior to intravenous administration increases specificity and efficiency of NP in diseased target-organs thus suggesting a potential role in nanomedicine and nanopharmacology.

Air-blood barrier translocation of tracheally instilled gold nanoparticles inversely depends on particle size.

Gold nanoparticles (AuNP) provide many opportunities in imaging, diagnostics, and therapy in nanomedicine. For the assessment of AuNP biokinetics, we intratracheally instilled into rats a suite of (198)Au-radio-labeled monodisperse, well-characterized, negatively charged AuNP of five different sizes (1.4, 2.8, 5, 18, 80, 200 nm) and 2.8 nm AuNP with positive surface charges. At 1, 3, and 24 h, the biodistribution of the AuNP was quantitatively measured by gamma-spectrometry to be used for comprehensive risk assessment. Our study shows that as AuNP get smaller, they are more likely to cross the air-blood barrier (ABB) depending strongly on the inverse diameter d(-1) of their gold core, i.e., their specific surface area (SSA). So, 1.4 nm AuNP (highest SSA) translocated most, while 80 nm AuNP (lowest SSA) translocated least, but 200 nm particles did not follow the d(-1) relation translocating significantly higher than 80 nm AuNP. However, relative to the AuNP that had crossed the ABB, their retention in most of the secondary organs and tissues was SSA-independent. Only renal filtration, retention in blood, and excretion via urine further declined with d(-1) of AuNP core. Translocation of 5, 18, and 80 nm AuNP is virtually complete after 1 h, while 1.4 nm AuNP continue to translocate until 3 h. Translocation of negatively charged 2.8 nm AuNP was significantly higher than for positively charged 2.8 nm AuNP. Our study shows that translocation across the ABB and accumulation and retention in secondary organs and tissues are two distinct processes, both depending specifically on particle characteristics such as SSA and surface charge.

Cytotoxic and proinflammatory effects of PVP-coated silver nanoparticles after intratracheal instillation in rats.

Silver nanoparticles (AgNP) are among the most promising nanomaterials, and their usage in medical applications and consumer products is growing rapidly. To evaluate possible adverse health effects, especially to the lungs, the current study focused on the cytotoxic and proinflammatory effects of AgNP after the intratracheal instillation in rats. Monodisperse, PVP-coated AgNP (70 nm) showing little agglomeration in aqueous suspension were instilled intratracheally. After 24 hours, the lungs were lavaged, and lactate dehydrogenase (LDH), total protein, and cytokine levels as well as total and differential cell counts were measured in the bronchoalveolar lavage fluid (BALF). Instillation of 50 µg PVP-AgNP did not result in elevated LDH, total protein, or cytokine levels in BALF compared to the control, whereas instillation of 250 µg PVP-AgNP caused a significant increase in LDH (1.9-fold) and total protein (1.3-fold) levels as well as in neutrophil numbers (60-fold) of BALF. Furthermore, while there was no change in BALF cytokine levels after the instillation of 50 µg PVP-AgNP, instillation of 250 µg PVP-AgNP resulted in significantly increased levels of seven out of eleven measured cytokines. These finding suggest that exposure to inhaled AgNP can induce moderate pulmonary toxicity, but only at rather high concentrations.

Biodistribution of inhaled gold nanoparticles in mice and the influence of surfactant protein D.

BACKGROUND: The pulmonary route is very promising for drug delivery by inhalation. In this regard, nanoparticulate drug delivery systems are discussed, and one very promising nano carrier example is gold nanoparticles (Au NP). Directly after their deposition, inhaled Au NP come into contact with pulmonary surfactant protein D (SP-D). SP-D can agglomerate Au NP in vitro, and this may influence the clearance as well as the systemic translocation in vivo. The aim of the present study was to investigate the clearance and translocation of Au NP at a very early time point after inhalation, as well as the influence of SP-D. METHODS: Aerosolized 20-nm radioactively labeled Au NP were inhaled by healthy adult female mice. One group of mice received dissolved 10 µg of SP-D by intratracheal instillation prior to the Au NP inhalation. After a 2-hr Au NP inhalation period, the mice were killed immediately, and the clearance and translocation to the blood stream were investigated. RESULTS: The highest amount of Au NP was associated with the lung tissue. In the bronchoalveolar lavage fluid (BALF), more Au NP remained free compared with the amount associated with the BALF cells. The amount of Au NP cleared by the mucociliary escalator was low, probably because of this very early time point. Instillation of SP-D prior to Au NP inhalation had no statistically significant effect on the biodistribution of the Au NP. CONCLUSION: Our data show that inhaled Au NP are retained in the mouse lungs and are translocated after a short time, and that SP-D has only a minor effect on Au NP translocation and clearance at a very early time point.