Lifecycle of nanoGEM materials: weathering

Wendel Wohlleben, Sabine Hirth, Bernhard von Vacano (BASF, SE)
Tinh Nguyen (National Institute of Standards and Technology, Gaithersburg, VA, USA)
Socorro Vasquez (Leitat, Barcelona, Spain)
A pilot round robin on weathering: spontaneous vs. induced release
nanoGEM (DE) – NIST (US) – Leitat (ES)
UV irradiation experiments were carried out with similar, not identical setups:
●BASF: ISO4892, Suntest XLS+ both dry and wet weathering (60W/m²)
●Leitat: ISO4892, Suntest XXL+, wet weathering (60W/m²)
●NIST: dry weathering in SPHERE (480 W/m²)
Both degraded bulk material and the spontaneously or induced released fragments were
investigated, and correlations suggest the most simple yet reliable methods to be validated
further by larger round robins.
Days at
NIST/dose
PA degradation is mostly the same for the PA.SiO2.composite,
but SiO2 remains on surface
PA.0% SiO2
PA.4%.SiO2
Mass loss and macrostructure / cracking unchanged.
0
3
10d/
5MJm-2
12 MJ/m2
2
Mass Loss, %
The nanocomposite material nanoGEM.PA.4%SiO2 and nanoGEM.PA.0%SiO2 as reference
were provided to two leading weathering laboratories: Tinh Nguyen (NIST, USA) and Socorro
Vasquez (Leitat, Spain, leader of NanoPolyTox, FP7)
1
35 MJ/m2
0
(~10 years UV)
-1
0
20
Dose (10^3 kJ/m2)
40
5x
50x
5x
50x
16d/
8MJm-2
Leitat: TGA, FT-IR, TEM/EDX
SiO2 on surface detected by ATR 1538 cm-1 ,
0
Absorbance
-0.1
BASF: SEM, XPS
NIST: AFM, FT-IR
on samples from 3 labs:
AUC, LD, TEM/EDX
(ICP-MS tbd)
69d/
35MJm-2
0
10
20
30
40
PA
-0.2
-0.3
nanocomposite
-0.4
-0.5
-0.6
Percent elemental composition
24d/
12MJm-2
by XPS
and by SEM
14
N%
Si %
12
10
8
6
4
2
0
0
-0.7
Dose (10^3 kJ/m2)
2
4
6
8
10
3
12
14
16
18
2
UV dose (x10 kJ/m )
1 µm
Induced release by UV + immersion
Fragments released are mostly polymer,
but some SiO2 can release
● The shear employed to induce release has little influence on results with PA.4%SiO2:
– Micron-range fragments are broken up / deagglomerated by sonication.
– Nano-range fragments mostly independent of A= immersion / B= shaking / C=sonication
● best reproducibility of C=sonication to induce release: matching results from samples
irradiated in different lab, matching results regardless of SDS in immersion fluid.
Quantification of Release
TGA identification of fragments
in rain water, Leitat
2 µm
10 nm
Rain waters,
Leitat
(216 MJ/m²)
200 nm
● NIST-irradiated, BASF-released: measured total
release = 1.22 mg/ml, if the released fragments
had the same composition as the bulk, would
contain 0.023 mg/ml of Si.
● ICP-MS finds 0.06 mg/ml. Hence the
released fragments are 90% polymer, but
the Si in the degraded composite has a
higher chance to release than the polymer.
(compare SEM)
● compare Leitat / Nanopolytox measured 312
mg/m² after 216 MJ/m² (=1.44mg/MJ), and by
TGA and FTIR confirm presence of NP, but
dominance of polymer in fragments.
● Quantification by ICP-MS, gravimetry and Analytical Ultracentrifugation (AUC):
– Same order of magnitude by spontaneous release into rain water ( X ,
gravimetry) and by UV_dry followed by immersion.
– For particle fillers (contrasting fibers) the mechanical shear during immersion is
not important – method robust against shear variations, w or w/o sonication.
● Further harmonization is scheduled for EU SUN + GuideNano + ILSI NanoRelease
(EPA)
200nm
Immersion
water, BASF
(290 MJ/m²)
200nm
„Integration of nanoGEM particles into lung lining vesicles“
●
●
●
APQ found that the affinity of lung lining
phospholipids to nanoparticles is generally very
low, and adsorption is reversible.
Here we demonstrate that surfactant proteins
SP-A and SP-B are required to integrate NPs in
vesicles, but only few NPs (amino, PVP, PEG)
have sufficient affinity to both SPs to decorate
vesicles.
Functionalized NP suspensions with negative
charge and/or steric stab. do get covered by a
mixed lipid/protein corona, but do not form large
structure with lipids in lining fluids
Correlation between SP affinity and vesicle
decoration
Consider the critical flotation of vesicles
in D2O and the critical mass balance:
1 vesicle ~ 10 ZrO2 ~ 1 SiO2 ~ 1/10 Ag
 Already decoration by 1 averagesize Ag or SiO2 particle should
reverse the direction of motion
0.15
0.10
0.00
-150 -100 -50
0
Sedimentation coefficient / Sved
SP-B
SP-C
● decoration observed in BALF, not in
lipids w/o surfactant proteins, even
for same lipid coverage on same
nanoparticles
● particles that decorate vesicles show
high affinity to both SP-A and SP-B:
Scheme of surfactant protrusions:
S. Schurch, R. Qanbar, H. Bachofen, F. Possmayer, Biol Neonate 1995, 67 Suppl 1, 61-76
J. Perez-Gil, Biochim Biophys Acta 2008, 1778, 1676-1695
1
Ag.50.PVP
0
ZrO2.PGA
SiO2.amino
-1
ZrO2.amino
-2
0.001
0.05
Ranking of vesicle / lipid affinity
correlates primarily with charge
with pBALF
2
Lipid vesicle flotation speed
(compared to no particles)
Particles in lung lining fluids
Volume Distribution, a.u.
Nanostrukturierte Materialen: Gesundheit, Exposition und Materialeigenschaften
Lifecycle of nanoGEM materials:
weathering-induced release and
lipid vesicle interactions
0.01
0.1
1
10
100
Lipid corona on particles (SIMS of pellett)
1000
with CuroSurf
with Lipid mix