Ecotoxicity of photocatalytically active titanium dioxide nanoparticles:
A model study with Caenorhabditis elegans.
Judith Angelstorf1, Wolfgang Ahlf2, Susanne Heise1
1Hamburg University of Applied Sciences
2Technical University Hamburg Harburg, Germany.
Contact: judith.angelstorf@haw-hamburg.deBackground

Materials and methods

Titanium dioxide nanoparticles (TiO2 NPs), which are increasingly
used in a variety of consumer products, enter the aquatic
environment with urban and industrial waste waters. According tomodeled data, TiO2 NPs are expected to accumulate in the sedimentphase with a rate of 273 to 1409 µg kg-1 y-1[1]. The ecotoxicologicale e a ce oof TiO
O2, however,o e e , iss sstill poopoorlyyuunderstood.
de s ood This
soongoinggo grelevancestudy aims to elucidate the ecotoxicological effects of TiO2 NPs on
the aquatic environment based on lab experiments using
Caenorhabditis elegans as a model for for the elucidation of specifictoxic responses. As many of the commercially used TiO2 NPs arephotocatalytically active, the main focus of this study will be theimpact of UV-exposure on the toxicity of the nanomaterial. This
poster shows first results on the effects of unirradiated particles
towards C.elegans.
C elegans

The standardized bioassay ISO 10872, a chronic
test using the nematode Caenorhabditis elegans
as model organism, is applied for thenanomaterial testing. Ecotoxicological endpoints
are reproduction, fertility and growth.
The testmaterial P 25 Aeroxide ((DegussagAG)) hasa primary particle size of 21 nm and a crystal
structure of 75% anatase and 25% rutile. It isdispersed in ultrapure water without stabilizersusing magnetic stirring and an ultrasonic bath.
The particle size distribution in the TiO2
dispersions introduced to the test are determinedby Dynamic Light Scattering (DLS) and ScanningElectron Microscopypy ((SEM).
)

Results and Discussion

Conclusions

96 h Exposure to P 25
100

Growth80

Inhhibition [%]Reproduction
60

*40
20

Chronic effects
Significant effects on reproduction wereobserved after 96 h exposure to TiO2 NPs(35% inhibition of the reproduction rate at50 mg/L).No significant effects on growthrate were observed up to 50mg/L.

010mg/L

30mg/L

50mg/l-20

Fig. 2: Inhibition of growth and reproduction of C.elegans exposed toTiO2 for 96 h [mean inhibition and CV in %]; * p-Value <0.01 (oneway ANOVA)

A

B

Fig. 1 Stereomicroscope images
A: C.elegans exposed to 20mg/L TiO2 for 96 h;
B: C.elegans exposed to TiO2 -free media for 96 h (Control)

B

A

Long-term- effects
No significant effects on reproduction andgrowth rate were observed up to 50mg/L
after 12 days exposure to TiO2 NPs.

4 mg/LI/I max [%]40 mg/L0,8100 mg/L

0,60,40,2This study
Thit d provides
id strong
tevidenceid
ffor
ingestion and egestion of agglomerated
TiO2 NPs by C.elegans.
The problem of agglomeration effects inthis bioassay is currently unresolved.
The effects of unirradiated TiO2 observed inthi study
thist d do
d nott indicate
i di t an environmental
it lrisk regarding the expected environmental
concentrations.

Elimination of TiO2 particles
Agglomerates are egested completely after
96 h in TiO2 free media, visible (no figureshown).

Future perspectives

Particle size distribution
All dispersions show a wide range ofparticle sizes, which is also reflected in
the relatively high PDI values (tab.1).
Particle sizes in the dispersions increase
with increasing particle concentration.

1,2

Reproduction of C.elegans is inhibited
significantly by exposure to TiO2 NPs atconcentrations of 50 mg/L.

Uptake of TiO2 particles
Agglomerated particles are visible in theintestinal tract of about 80% of the worms
after 96 h exposure to TiO2 (Fig. 1). Titanium
was located subcutaneously with Energy
Dispersive X-ray (EDX)-analysis (Fig. 2).

Fig. 2: Critical point dried worm exposed to 20 mg/L TiO2 for 96 h,
A: EDX mapping of Titanium with 20 keV
B: SEM image, SE detector, 5 keV

1Malvern.de

The further studies aim at investigatinggg
 photo induced toxic effects of P 25 as aphoto catalytic substance the influence of P 25 on toxicity of cocontaminants elucidating the importance ofphoto-modification and photo-sensitization
processes
 the impact of TiO2 -contamination on
sediment toxicity.

01

10100

1000

10000

The further studies aim at establishing

Particle size [nm]Fig. 3: Particle size distribution at concentrations of 4, 40 and 100 mg/L
TiO2 gained by DLS; shown as standardized “Mean Intensity”values.

Conc[mg/L]

Media4
H2O40
H2O
100
H2O
2 H2O+ M9
20 H2O + M9
100 H2O + M9PDIAverage particle
size*[nm]0,6071285
0,46731439
0,45641637
0,63226470,4683
1688
0,563
1111

CV[%]

Tab. 1: DLS measures of TiO2 dispersions in H2O, pure andintroduced to M9 media. * Average Intensity mean values (10repeated measures); PDI: Poly Dispersity Index.

211922152941

Agglomeration behavior
According to the DLS data (table 1),
addition of M9 media to TiO2 dispersions
leads to agglomeration and formation oflarger particles. Agglomeration andsedimentation of the particles is also
visible macroscopically.

 Scanning Electron Microscopy to monitor
particle size distribution during
ecotoxicological testing.

Reference[1] Gottschalk, F.et al., 2009. Modeled Environmental
Concentrations of Engineered Nanomaterials (TiO2, ZnO, Ag,CNT, Fullerenes) for Different Regions. Environmental
Science & Technology, 43(24), 9216-9222.

Acknowledgements
Thanks to Michael Gröger (ITMC UHH) for his help with DLS, to Jens Timmermann (TUHH) for his help with SEM and EDX and to the OECD Sponsorship Programme for the provision of test material. Work was partially funded by Pro Exzellenzia.