Table 2 Basic characteristics of the 11 ex vivo placental perfusion investigating the maternal-fetal transfer of engineered NPs

 [37]

Human

6

Ag NPs/ carboxyl or PEG

2–15 or 5–15^b

40 or 75 μg/mL^c/ 6 h

spICP-MS

Bright-field light microscopy

Higher transplacental transport for smaller and PEGylated Ag NPs, while carboxylated Ag NPs accumulated more in placental tissue.

 [31]

Human

6

Au NPs/ carboxyl or PEG

3.5 ± 1.2 or 4.5 ± 1.5^b

25 μg/mL^c/ 6 h

LA- and SF-ICP-MS

/

Only PEGylated Au NPs observed in the fetal circulation. Placental tissue accumulation similar for both Au NP types.

 [38]

Rat

11

Au NPs

20^a

5.8 μg/mL^d/ 3 h

ICP-MS

Hyper-spectral microscopy imaging

Au NPs translocated across the rat placenta within 20 min of maternal infusion.

 [23]

Human

n.d.

Au NPs/ PEG

15 or 30^a

1.6 × 10¹¹ or 1.6 × 10¹⁰ particles/mL^d/ 18 min

ICP-MS

TEM and bright-field light microscopy

No placental transfer of Au NPs detected. Visual confirmation of localization of NPs in syncytiotrophoblasts.

 [23]

Human

n.d.

Au NPs/ PEG

10 or 15^a

9.1 × 10⁹ or 2.0 × 10⁹ particles/mL^c/ 6 h

ICP-MS

TEM and bright-field light microscopy

No transfer of Au NPs across placenta regardless of NP size. Visual confirmation of placental tissue uptake of Au NPs.

 [25]

Human

6

SiO₂ NPs/ fluorophore

25 or 50^a

100 μg/mL^c/ 6 h

Fluorescence microscopy

Confocal microscopy

Limited transfer of both SiO₂ NP sizes to fetal perfusate despite placental accumulation.

 [39]

Human

n.d.

Magnetic NPs/ starch or PEI

100 or 150^a

50 μg/mL^c/ 6 h

Magnetic system

Bright-field light microscopy

Limited transfer of magnetic NPs from the maternal to the fetal circuit. Histological findings confirmed the presence of NPs in placental tissue.

 [34]

Human

6

TiO₂ NPs/ amine or carboxyl

4 to 8^a

10 μg/mL^c/ 6 h

SF-ICP-MS

/

No translocation of both TiO₂ NP types to the fetal circulation but accumulation in placental tissue.

 [40]

Human

7

PS NPs/ fluorophore

80 or 500^a

25 μg/mL^c/ 6 h

Fluorescence microscopy

/

80 nm PS NPs able to cross the placenta, while 500 nm PS NPs retained in the placenta or maternal circuit.

 [41]

Human

12

PS NPs/ fluorophore and carboxyl

43.7 ± 8, 44.1 ± 7.1, 220.5 ± 5.1, or 289.4 ± 10.2^b

25 μg/mL^e/ 6 h

Fluorescence microscopy

TEM

Increased translocation of plain compared to carboxylated PS NPs after 6 h of perfusion. Significantly higher transfer of NPs in the fetal to maternal direction observed with bidirectional transfer studies. Placental accumulation of all NPs regardless of modification and perfusion direction.

 [42]

Human

32

PS NPs/ fluorophore, amine, or carboxyl

63 ± 10, 71 ± 11, 78 ± 20, 88 ± 7, 89 ± 3, 181 ± 11, 224 ± 17, 455 ± 32, 451 ± 28, 494 ± 29, or 499 ± 8^b

25 μg/mL^c/ 6 h

Fluorescence microscopy

/

Plain and small carboxylated PS NPs but not aminylated PS NPs transferred across the placenta after 6 h of perfusion.

 [43]

Human

16

PS NPs/ fluorophore

50, 80, 240, or 500^a

25 μg/mL^c/ 6 h

/

TEM

PS NPs up to 240 nm crossed the placenta and reached the fetal circuit. 500 nm PS NPs mainly retained in the placental tissue and maternal circuit.