This journal is © The Royal Society of Chemistry 2015 Metallomics
Cite this: DOI: 10.1039/c4mt00240g
The metallobiochemistry of ultratrace levels of
platinum group elements in the rat
E. Sabbioni,
a
S. Fortaner,
b
S. Manenti,*
c
F. Groppi,
c
M. Bonardi,
c
S. Bosisio
d
and
M. Di Gioacchino
a
The use of platinum, palladium and rhodium (Platinum Group Elements – PGEs) and the possibility of
exposure to their ultratrace levels is increasing. In fact, the exponential development of metallic PGE-
based nanoparticles (o100 nm in size) opens extraordinary perspectives in the areas of electrocatalysts
and catalytic converters, magnetic nanopowders, polymer membranes, cancer therapy, coatings, plastics,
nanofibres and textiles. Like other metal-based nanoparticles, exposure to PGEs nanoparticles may result
in a release of ultratrace amounts of Pt, Pd, Rh ions in the body whose metabolic fate and toxicity still
need to be evaluated. Furthermore, PGEs can act as allergic sensitizers by acting as haptens and inducing
both type I and IV allergic reactions. In this work we studied the in vivo metabolic patterns of ultratrace
levels of potent allergens and sensitizers PGE halogenated salts.
191
Pt,
103
Pd and
101m
Rh radioisotopes were
prepared via cyclotron irradiation and used for radiolabelling Na
2
191
PtCl
4
, Na
2
103
PdCl
4
and Na
2
101m
RhCl
6
salts. These anionic chlorocomplexes were intraperitoneally injected into rats (114 ng Pt kg
1
bodyweight;
24 ng Pd kg
1
b.w.; 16 ng Rh kg
1
b.w.). At 16 h post-exposure, PGEs were poorly but significantly
retained in all tissues analysed. Kidneys, spleen, adrenal gland, liver, pancreas and small intestine were the
organs with the highest Pt, Pd, Rh concentrations. In the blood 30–35% of
103
Pd and
191
Pt and 10% of
101m
Rh were recovered in the plasma, mainly bound to albumin and to a less extent to transferrin.
The hepatic and renal intracellular distribution showed the highest recovery of
191
Pt,
103
Pd and
101m
Rh in
the nuclear fraction (liver) and in the cytosol (kidney). Chromatographic separation and ultrafiltration
experiments on kidney and liver cytosols showed the strong ability of biochemical macromolecules to
bind
191
Pt,
103
Pd and
101m
Rh, and being responsible for the retention of the three elements in the body.
The link to macromolecules is the basis for the sensitizing capacity of PGEs.
Introduction
Platinum (Pt), palladium (Pd) and rhodium (Rh) (Platinum Group
Elements – PGEs) have historically been the metal components of
the three-way catalytic converters of air pollution control devices
mainly of cars and trucks.
1
In the form of highly dispersed
particles with diameters in the 1–10 nm range
2
these auto-
catalysts are unique in converting harmful hydrocarbons,
carbon monoxide, and nitrogen oxide emissions from gasoline
engines into less harmful CO
2
,N
2
and H
2
O.
3
However, this type
of device is not totally environmentally clean. The hot exhaust
gases flowing through the catalytic converter cause abrasion
and ablation of these latter,
4
leading to the release of micronic
and nanosized PGEs particulates to air, roads, tunnels as well
as roadside soil,
5
representing anthropogenic environmental
pollutants for the general population.
6
Moreover, occupational
exposure to PGEs occurs during mining, processing, refining
and catalyst manufacture.
7
PGEs have other applications, representing a further source
for human exposure. Platinum is used in biomedicine in anti-
cancer drugs,
8
and as a component of pacemakers, catheters
and defibrillators;
9
in industrial processes as a catalyst as in the
polymerisation of olefins, and the refining of petroleum and
ammonia oxidation; in electronic industries and glass manu-
facturing; and in jewellery where it represents the second
largest demand.
10
Palladium is used in electronic applications;
in dentistry for dental crowns and bridges though they have
been increasingly replaced by all-ceramic; in jewelry; in the
chemical industry, in fuel cell technology; for coinage purpose;
and in hydrogen purification.
11
Although catalytic converters
use about 80% of the world’s rhodium production, this metal is
applied in the glass industry, mostly for production of fiberglass
a
Aging Research Centre (Ce.S.I.), ‘‘G. d’Annunzio- University Foundation’’,
Via dei Vestini-21, 66100 Chieti, Italy
b
European Commission, IHCP, JRC-Ispra, Via Fermi, 2749, 21027 Ispra,
Varese, Italy
c
UNIMI e INFN Sezione di Milano LASA, Via F.lli Cervi-201, 20090 Segrate, Milan,
Italy. E-mail: simone.manenti@mi.infn.it
d
Department of Radiation Science and Technology, Delft University of Technology,
Mekelweg 15, 2629 JB Delft, The Netherlands
Received 12th September 2014,
Accepted 22nd December 2014
DOI: 10.1039/c4mt00240g
www.rsc.org/metallomics
Metallomics
PAPER
Published on 22 December 2014. Downloaded by Universita di Chieti -Pescara on 23/01/2015 07:39:08.
View Article Online
View Journal