Assessment of ZnO and SiO₂ nanoparticle permeability through and toxicity to the blood–brain barrier using Evans blue and TEM

Figures & data

Table 1 Administration concentrations and volumes of 28-day repeated oral administrations in rats

Experimental group	Test material	Sex	Number of animals	Administration concentration (mg/kg)	Administration volume (mL/kg)
Group 1 (negative control)	Distilled water	Female	5	0	10
Group 2 (diluting agent)	HEPES-citrate buffer	Female	5	0	10
Group 3 (diluting agent)	HEPES-serine buffer	Female	5	0	10
Group 4 (diluting agent)	L-arginine	Female	5	0	10
Group 5 (high volume)	ZnO (20 nm, − charge)	Female	5	500	10
Group 6 (high volume)	ZnO (20 nm, + charge)	Female	5	500	10
Group 7 (high volume)	SiO2 (20 nm, − charge)	Female	5	2,000	10
Group 8 (high volume)	SiO2 (20 nm, + charge)	Female	5	1,000	10

Abbreviations: HEPES, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid); ZnO, zinc oxide; SiO₂, silica.

Table 2 Administration concentrations and volumes for 90-day SiO₂^EN100(R) and SiO₂^EN20(R) oral administrations and SiO₂^EN100(−) and SiO₂^EN20(−) dermal administrations

Method	Test material	Administration concentration (mg/kg)	Administration volume (mL/kg)
Oral	SiO2^EN20(R)	1,000	10
administration	SiO2^EN100(R)	1,000	10
Dermal	SiO2^EN20(−)	2,000	10
administration	SiO2^EN100(−)	2,000	10

Figure 1 Standard curve of Evans blue.

Note: Evans blue dye (Sigma-Aldrich Co., St Louis, MO, USA).

Abbreviation: OD, optical density.

Figure 2 The difference value between ZnO NP treated groups and control groups.

Notes: (A) OD value of each brain region extracted from ZnO^SM20(+)- and ZnO^SM20(−)-treated rats; (B) each brain region of the amount of Evans blue per unit (g). Evans blue dye (Sigma-Aldrich Co., St Louis, MO, USA).

Abbreviations: OD, optical density; ZnO, zinc oxide; NP, nanoparticle.

Figure 3 The difference value between SiO₂ NP treated groups and control groups.

Notes: (A) OD value of each brain region extracted from SiO₂^EN20(R)- and SiO₂^EN20(−)-treated rats; (B) each brain region of the amount of Evans blue per unit (g).

Abbreviations: OD, optical density; SiO₂, silica; NP, nanoparticle.

Figure 4 Detection of the neuron-specific protein NeuN on rat left hemispheres.

Notes: Cerebellum regions of tested rats are pictured and organized according to zinc oxide (ZnO) character (particle sizes [20 and 100 nm], positively and negatively charged surfaces, and injected concentrations), as indicated by black bars. (A) Phosphate-buffered saline-injected control normal rat brain of cerebellum region; (B) 10 mg of ZnO^SM20(+); (C) 0.1 mg of ZnO^SM20(+); (D) 10 mg of ZnO^SM20(−); (E) 0.1 mg of ZnO^SM20(−); (F) 10 mg of ZnO^SM100(+); (G) 0.1 mg of ZnO^SM100(+); (H) 10 mg of ZnO^SM100(−); (I) 0.1 mg of ZnO^SM100(−).

Figure 5 Silica nanoparticle in SH-SY5Y neuroblastoma cell.

Notes: (A) Transmission electron microscope image of SH-SY5Y neuroblastoma cells treated with SiO₂^EN100(–); (B) graph of energy-dispersive X-ray spectroscope analysis. The green circle highlights the Si peak.

Abbreviations: Fe, iron; Nb, niobium; O, oxygen; Pb, lead; Si, silicon; SiO₂, silica; Zn, zinc.

Figure 6 Transmission electron microscope images of the brain regions of a silica (SiO₂) repeatedly treated rats.

Notes: (A–C) Dermally administered SiO₂^EN20(−); (D–F) dermally administered SiO₂^EN100(−); (G–I) orally administered SiO₂^EN20(R); (J–L) orally administered SiO₂^EN100(R).

Figure 7 The results of energy-dispersive X-ray spectroscope analysis of SiO₂^EN20(–)-treated rat hippocampus via dermal administration.

Notes: A and B are examples of suspected nano-size dot and graph of energy-dispersive X-ray spectroscope analysis.

Abbreviations: Ca, calcium; Cl, chlorine; Cu, copper; Fe, iron; O, oxygen; OS, osmium; P, phosphorus; SiO₂, silica; EDS, energy-dispersive X-ray spectroscope.

Figure 8 Analysis of suspected nano-size dot in SiO₂^EN100(−) dermal administration group.

Notes: (A) Transmission electron microscope image of hippocampus in SiO₂^EN100(–) dermal administration group; (B) enlarged image of suspected substance; (C) graph of energy-dispersive X-ray spectroscope analysis.

Abbreviations: C, carbon; Cl, chlorine; Cu, copper; Os, osmium; Pb, lead; SiO₂, silica; Ti, titanium.