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 ...198Au-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.
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.
The biokinetics of a size-selected fraction (70 nm median size) of commercially available and
48
V-radiolabeled
48
VTiO
2
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
48
VTiO
2
-nanoparticle suspension by intra-esophageal instillation. A completely balanced quantitative body clearance and biokinetics in all organs and tissues was obtained by applying typical
48
VTiO
2
-nanoparticle doses in the range of 30-80 μg*kg
−1
bodyweight, making use of the high sensitivity of the radiotracer technique. The
48
VTiO
2
-nanoparticle content was corrected for nanoparticles in the residual blood retained in organs and tissue after exsanguination and for
48
V-ions not bound to TiO
2
-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
48
VTiO
2
-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 TiO
2
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
48
VTiO
2
-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 TiO
2
nanoparticles.
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.
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.
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.
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.
Abstract
It is of urgent need to identify the exact physico-chemical characteristics which allow maximum uptake and accumulation in secondary target organs of nanoparticulate drug delivery systems ...after oral ingestion. We administered radiolabelled gold nanoparticles in different sizes (1.4-200 nm) with negative surface charge and 2.8 nm nanoparticles with opposite surface charges by intra-oesophageal instillation into healthy adult female rats. The quantitative amount of the particles in organs, tissues and excrements was measured after 24 h by gamma-spectroscopy. The highest accumulation in secondary organs was mostly found for 1.4 nm particles; the negatively charged particles were accumulated mostly more than positively charged particles. Importantly, 18 nm particles show a higher accumulation in brain and heart compared to other sized particles. No general rule accumulation can be made so far. Therefore, specialized drug delivery systems via the oral route have to be individually designed, depending on the respective target organ.
The biokinetics of a size-selected fraction (70 nm median size) of commercially available and
48
V-radiolabeled
48
VTiO
2
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
48
VTiO
2
-nanoparticle suspension. A completely balanced quantitative biodistribution in all organs and tissues was obtained by applying typical
48
VTiO
2
-nanoparticle doses in the range of 40-240 μg·kg
−1
bodyweight and making use of the high sensitivity of the radiotracer technique. The
48
VTiO
2
-nanoparticle content was corrected for residual blood retained in organs and tissues after exsanguination and for
48
V-ions not bound to TiO
2
-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
48
VTiO
2
-nanoparticles present in liver and kidneys remained constant (0.03%).
48
VTiO
2
-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
48
VTiO
2
-nanoparticles. This contribution may account for 1/5 of the nanoparticle retention in some organs. After normalizing the fractions of retained
48
VTiO
2
-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 TiO
2
-particles (including nanoparticles) and accumulation in secondary organs may pose long-term health risks, this issue should be scrutinized more comprehensively.
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.
To study the fate of inhaled AgNP, healthy adult rats were exposed to 1½-hour intra-tracheal inhalations of pristine
Ag-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•10
, respectively). At five time-points (0.75 h, 4 h, 24 h, 7d, 28d) post-exposure (p.e.), a complete balance of the
AgAgNP fate and its degradation products were quantified in organs, tissues, carcass, lavage and body fluids, including excretions. Rapid dissolution of
AgAg-ions from the
AgAgNP 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
AgAg-ions precipitate rapidly to low-solubility
AgAg-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
AgAg-salt precipitates was compatible with auxiliary biokinetics studies at 24 h and 7 days after either intravenous injection or intratracheal or oral instillation of
AgAgNO
solutions in sentinel groups of rats. However, dissolution of
AgAg-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
AgAgNP surface that mediate and prolonge the dissolution process. The concurrent clearance of persistent cores of
AgAgNP and
AgAg-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
AgAgNP 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
AuAuNP of the same size and under identical experimental and exposure conditions (Kreyling et al., ACS Nano 2018), the kinetics of the ABB-translocation of
AgAg-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
AgAgNP were cleared throughout the study period. Urinary
AgAg excretion is minimal, finally accumulating to 0.016.
The biokinetics of inhaled
AgAgNP is relatively complex since the dissolving
AgAg-ions (a) form salt layers on the
AgAgNP surface which retard dissolution and (b) the
AgAg-ions released from the
AgAgNP surface form poorly-soluble precipitates of
AgAg-salts in ELF. Therefore, hardly any
AgAg-ion clearance occurs from the lungs but instead
AgAgNP and nano-sized precipitated
AgAg-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.
Submicrometer TiO
2
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
48
V-radiolabeled, pure TiO
2
anatase nanoparticles (
48
VTiO
2
NP) 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
48
VTiO
2
NP 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
48
VTiO
2
NP 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
48
VTiO
2
NP 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.
Industrially produced quantities of TiO
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.
To study the fate of inhaled TiO
-NP, adult rats were exposed to 2-h intra-tracheal inhalations of
V-radiolabeled, 20 nm TiO
-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
VTiO
-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
) by LT-MC. Prior to LT-MC,
VTiO
-NP are re-entrained to the epithelium as reported earlier for 20 nm inhaled gold-NP (AuNP) and iridium-NP (IrNP).
Comparing the 28-day biokinetics patterns of three different inhaled NP materials TiO
-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 TiO
-NP. We discuss mechanisms and pathways of NP relocation and re-entrainment versus translocation. Additionally, after 28 days the integral translocated fractions of TiO
-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 TiO
-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.
When particles incorporated within a mammalian organism come into contact with body fluids they will bind to soluble proteins or those within cellular membranes forming what is called a protein ...corona. This binding process is very complex and highly dynamic due to the plethora of proteins with different affinities and fractions in different body fluids and the large variation of compounds and structures of the particle surface. Interestingly, in the case of nanoparticles (NP) this protein corona is well suited to provide a guiding vehicle of translocation within body fluids and across membranes. This NP translocation may subsequently lead to accumulation in various organs and tissues and their respective cell types that are not expected to accumulate such tiny foreign bodies. Because of this unprecedented NP accumulation, potentially adverse biological responses in tissues and cells cannot be neglected a priori but require thorough investigations. Therefore, we studied the interactions and protein binding kinetics of blood serum proteins with a number of engineered NP as a function of their physicochemical properties. Here we show by in vitro incubation tests that the binding capacity of different engineered NP (polystyrene, elemental carbon) for selected serum proteins depends strongly on the NP size and the properties of engineered surface modifications. In the following attempt, we studied systematically the effect of the size (5, 15, 80 nm) of gold spheres (AuNP), surface-modified with the same ionic ligand; as well as 5 nm AuNP with five different surface modifications on the binding to serum proteins by using proteomics analyses. We found that the binding of numerous serum proteins depended strongly on the physicochemical properties of the AuNP. These in vitro results helped us substantially in the interpretation of our numerous in vivo biokinetics studies performed in rodents using the same NP. These had shown that not only the physicochemical properties determined the AuNP translocation from the organ of intake towards blood circulation and subsequent accumulation in secondary organs and tissues but also the the transport across organ membranes depended on the route of AuNP application. Our in vitro protein binding studies support the notion that the observed differences in in vivo biokinetics are mediated by the NP protein corona and its dynamical change during AuNP translocation in fluids and across membranes within the organism.
PDF
