Effect of particle size on in vitro cytotoxicity of titania and alumina nanoparticles

Figures & data

Table 1. Commercial source and description of manufactured nanoparticles.

Particles type	Supplier	Description and characterisation
5 nm TiO2	Nanostructrured & Amorphous Materials, Inc, Houston, TX	Titanium (IV) oxide, 5 nm average particle size (APS), 99.9% anatase, 200–220 m^2/g of specific surface area (SSA), Stock #: 5420 HT
200 nm TiO2	Acros Organics, Morris Plains, NJ	Titanium (IV) oxide, 99.9% anatase powder, Product No. 213580050
10 nm Al2O3	Nanostructrured & Amorphous Materials, Inc, Houston, TX	Aluminum oxide in water dispersion, 10 ± 5 nm APS, 190 m^2/g SSA, 20% Al2O3 by wt., 99.9% gamma phase, Stock #7016WJWG
50 nm Al2O3	Alfa Aesar, Ward Hill, MA	Aluminium oxide, 40–50 nm APS, Powder, 32–40 m^2/g SSA, 30% gamma and 70% delta, Stock #44932

Figure 1. TEM images of particles used in this study. (a) 5 nm TiO₂; (b) 200 nm TiO₂; (c) 10 nm Al₂O₃ and (d) 50 nm Al₂O₃.

Table 2. Particle characterisation by DLS, SMPS.

Particle type/nominal size (nm)	Particle size (nm)
	DLS (in water)	DLS (in media without serum)	DLS (in media with serum)	SMPS
TiO2/5	317 ± 10.7	534 ± 29	310 ± 47	4.3 ± 1.27
TiO2/200	314.4 ± 4.7	1441 ± 115	299 ± 5	180 ± 1.4^a
Al2O3/10	54.8 ± 1.5	2332 ± 271	727 ± 20	6 ± 1.5
Al2O3/50	194 ± 2.4	2681 ± 408	786 ± 51	75.7 ± 2.23
Notes: ^a200 nm TiO2 could not be aerosolised by the electrospray. Its native particle size was evaluated by analyzing SEM images (n = 423).

Figure 2. Effect of NP exposure on cell viability, as determined by the colony number after a 5-day exposure. Asterisk (*) represents significant difference from the control group (p ≤ 0.05).

Figure 3. Effect of NP exposure on cell proliferation, as determined by average cell number per colony after: (a) 2-day exposure; (b) 5-day exposure. Asterisk (*) denotes significant difference from the control group or between two comparing groups (p ≤ 0.05).

Figure 4. Cytotoxicity of metal NPs to A549 cells after a 5-day exposure determined by the alamarBlue®. Asterisk (*) represents significant difference from the control group or between two comparing groups (p ≤ 0.05).

Figure 5. Comparison of cell proliferation of cell groups cultured with metal NP dispersion and the corresponding supernatant using a clonogenic assay. Asterisk (*) represents significant difference from the control group or between two comparing groups (p ≤ 0.05).

Figure 6. Cell response curves for 5 and 200 nm TiO₂ and 10 and 50 nm Al₂O₃ NPs: (a) proliferation and (b) metabolism. Dose is expressed as surface area concentration (m²/L). The curve represents an exponential regression for the response.