Table 1 Basic characteristics of the 15 in vitro studies investigating the maternal-fetal transfer of engineered NPs

 [22]

BeWo b30^a

Ag and Ag₂S NPs/lipoic acid, citrate, or PEI

28 ± 2, 47 ± 5, 48 ± 5, or 51 ± 5^c

1 μg/mL/ 4, 6, 18, and 24 h

ICP-MS and spICP-MS

/

Internalization and transfer of different Ag NP types in the BeWo b30 cell layer dependent on surface chemistry.

 [23]

BeWo b30

Au NPs/ PEG

10^b

3.6 × 10¹⁰ particles/mL/6, 24, and 48 h

/

AMG and TEM

After exposure for 6 h, 24 h, and 48 h, aggregates of Au NPs detected in BeWo b30 cells.

 [24]

BeWo b30^a

Fe₃O₄ NPs/Na-oleate

8^b

50 or 100 μg/mL^e/ 24 h

/

Bright-field light microscopy and TEM

Increased transport of Fe₃O₄ across and uptake in BeWo b30 cells NPs after Na-oleate-coating.

 [24]

BeWo b30^a

SiO₂ NPs/fluorophore

25 or 50^b

25 or 50 μg/mL^e/ 6 h

Fluorescence microscopy

Confocal microscopy

SiO₂ NPs crossed the BeWo b30 cells without a significant effect of particle size or concentration on transport or internalization.

 [25]

BeWo b30^a

SiO₂ NPs/fluorophore

25 or 50^b

100 μg/mL^e/ 24 h^f

Fluorescence microscopy

Confocal microscopy

Limited transport of SiO₂ NPs across the BeWo b30 cells. Confocal microscopy visually confirmed particle accumulation in the cells.

 [26]

BeWo b30^a

PS NPs/fluorophore

50 or 100^b

500 μg/mL/ 24 h^f

Fluorescence microscopy

Confocal microscopy

Suggested size-dependent transport and cellular uptake as 50 nm PS NPs transferred to the fetal compartment at a higher rate compared to 100 nm PS NPs.

 [27]

3A-sub-E

PS NPs/carboxyl and fluorophore

20, 40, 100, 200, or 500^b

10 μg/mL/ 4 h

Flow cytometry and confocal microscopy

TEM

Differentially sized fluorescent PS NPs present in the trophoblast cells after 4 h of exposure, Cellular NP uptake highest and lowest for 40 nm and 500 nm PS NPs, respectively.

 [28]

BeWo b30^a

PS NPs/carboxyl and fluorophore

50^b

10 μg/mL/ 24 h

Fluorescence microscopy

/

Limited translocation of PS NPs across the BeWo b30 cell layer without relation to NP charge.

 [29]

HTR-8

PM_2.5

<2500^d

0.5 μg/mL/ 24 and 48 h

/

TEM

PM_2.5 particle uptake visualized within the inner mitochondrial membranes of exposed first trimester placental cells without difference in the 24 h and 48 h exposure groups.

 [30]

HTR-8

Wood smoke particles

< 1000^d

0.5 μg/mL/ 48 h

/

TEM

Wood smoke particles entered the cell and localized to the mitochondria in trophoblast cells, causing structural damage.

 [31]

BeWo b30/ HPEC-A2^a

Au NPs/carboxyl or PEG

3.5 ± 1.2 or 4.5 ± 1.5^c

25 or 50 μg/mL/ 24 h

ICP-MS

LA-ICP-MS and TEM

PEGylated and carboxylated Au NPs crossed the co-culture in low amounts. Higher cellular uptake for carboxylated Au NPs, and slightly increased translocation for PEGylated Au NPs.

 [32]

BeWo b30/ HVMF

Au NPs/carboxyl or PEG

3.5 ± 1.2, 4.5 ± 1.5, 13.5 ± 3, or 14.0 ± 3.5^c

50 μg/mL/ 24 h

ICP-MS

LA-ICP-MS and TEM

Higher uptake for the smaller, carboxylated Au NPs compared to the larger, PEGylated Au NPs, which barely passed the co-culture.

 [33]

BeWo/hPC-PL^a

SPIONs/starch, PEI, or CMX

n.d.

200 μg/mL/ 3 or 24 h

AAS and MPS

Bright-field light microscopy and confocal microscopy

PEI-coated SPIONs (cationic) remained primarily in the co-culture. Starch- and CMX-coated SPIONS (neutral and anionic, respectively) were able to pass the cell layer to a greater extent.

 [34]

BeWo b30/ HPEC-A2^a

TiO₂ NPs/ amine or carboxyl

4 to 8^b

1 μg/mL/ 6 or 24 h

SF-ICP-MS

/

No transplacental transfer of TiO₂ NPs. Both types internalized in the BeWo b30 and HPEC-A2 cells of the co-culture.

 [35]

BeWo b30/ HPEC-A2^a

PS NPs/ fluorophore

49 or 70^b

50 or 500 μg/mL/ 24 h^f

Fluorescence microscopy

/

70 nm PS NPs did not cross the co-culture. Small amounts of 49 nm PS NPs detected in the basolateral compartment after 24 h of exposure. Similar results for static and shaken conditions.

 [36]

BeWo b30/ HPEC-A2^a

PS NPs/ fluorophore and carboxyl

46.3 ± 6.0^c

10 or 100 μg/mL/ 24 h

AF4-UV

Confocal microscopy

Within 24 h, no transport across the co-culture for both concentrations of PS NPs. Internalization of PS NPs in BeWo cells shown by confocal microscopy.