A dual brain-targeting curcumin-loaded polymersomes ameliorated cognitive dysfunction in intrahippocampal amyloid-β1-42-injected mice

Abstract

Due to the impermeability of the blood-brain barrier and the nonselective distribution of drugs in the brain, the therapeutic access to intractable neurological disorders is challenging. In this study, dual brain-targeting polymersomes (POs) functionalized by transferrin and Tet-1 peptide (Tf/Tet-1-POs) promoted the transportation of curcumin into the brain and provided neuroprotection. The modification of the ligands that bind to the surface of POs was revealed by X-ray photoelectron spectroscopy analysis. The cell uptake of a coculture model of mouse brain capillary endothelial cells with neurons showed that the Tf/Tet-1-POs had significant transportation properties and possessed affinity for neurons. The pharmacokinetic analysis showed that the blood-brain barrier permeability-surface efficiency of the Tf/Tet-1-POs was 0.28 mL/h/g and that the brain tissue uptake rate (% ID/g) was 0.08, which were significant compared with the controls (P<0.05). The curcumin-encapsulated Tf/Tet-1-POs provided neuroprotection and ameliorated cognitive dysfunction in intrahippocampal amyloid-β1-42-injected mice. These results suggest that the dual brain-targeting POs are more capable of drug delivery to the brain that can be exploited as a multiple noninvasive vehicle for targeting therapeutics.

Keywords: Alzheimer’s disease; Tet-1 peptide; polymersomes; transferrin.

Figure 1

NMR spectrum of maleimide-PEG-PLGA copolymer in CDCl3. Notes: (A) ¹H NMR spectrum and (B) ¹³C NMR spectrum of maleimide-PEG-PLGA copolymer in CDCl₃. Abbreviations: PEG, poly(ethylene glycol); PLGA, poly(D,L-lactic-co-glycolic acid); ppm, part per million.

Figure 2

TEM images of Tf/Tet-1-POs (bar 200 and 50 nm). Abbreviations: TEM, transmission electron microscopy; Tf, transferrin; POs, polymersomes.

Figure 3

X-ray photoelectron spectroscopy analysis of POs modified with various ligands. Notes: Carbon C1s envelopes: (A) POs, (B) Tf-POs, (C) Tet-1-POs, and (D) Tf/Tet-1-POs. Oxygen O1s envelopes: (E) POs, (F) Tf-POs, (G) Tet-1-POs, and (H) Tf/Tet-1-POs. Nitrogen envelopes: (I) POs, (J) Tf-POs, (K) Tet-1-POs, and (L) Tf/Tet-1-POs. The peaks at binding energies of 281–307 eV, 527–545 eV, and 398–414 eV were ascribed to the elements C1s, O1s, and N1s, respectively. The XPS survey scans were elucidated. The curve fitting results showed that the C1s regions could be presented by four peaks (A–D), of which the peak 1 signal represented C-C/C-H (285.1 eV), the peak 2 signal represented C-O-C (286.4 eV), the peak 3 signal represented O=C-C*(-C)-O (287.6 eV), and peak 4 signal that corresponded to O-C=O (289.1 eV), respectively. The O1s regions could be presented by peak signals that corresponded to O=C (peak 5, 532.6 eV) and O–C (peak 6, 533.4 eV) (E–H). The N1s generated in Tf-POs, Tet-1-POs, and Tf/Tet-1-POs could be corresponded to peak 7. Abbreviations: POs, polymersomes; Tf, transferrin.

Figure 4

Cellular uptakes of various ligands-modified POs by bEnd.3 and Neuro-2a cells at 37°C for 2 hours (bar 200 μm). Notes: Fluorescence imaging of Neuro-2a cells: (A) 6-coumarin-POs, (B) 6-coumarin-Tf-POs, (C) 6-coumarin-Tet-1-POs, and (D) 6-coumarin-Tf/Tet-1-POs. Fluorescence imaging of BCECs: (E) 6-coumarin-POs, (F) 6-coumarin-Tf-POs, (G) 6-coumarin-Tet-1-POs, and (H) 6-coumarin-Tf/Tet-1-POs. (I) Uptake index of various ligands-modified POs by Neuro-2a cells in the coculture model of bEnd.3 cells with Neuro-2a cells. *P<0.05. Abbreviations: POs, polymersomes; Tf, transferrin; BCECs, brain capillary endothelial cells; UI, uptake index.

Figure 5

In vivo images. Notes: In vivo images of nude mice administered with fluorescent probe DiR-labeled POs at 2 hours. (A) DiR-POs, (B) DiR-Tet-1-POs, (C) DiR-POs, and (D) DiR-Tf/Tet-1-POs. Ex vivo images of the brain administered with fluorescent probe Dir-labeled POs at 2 hours: (A′) DiR-POs, (B′) DiR-Tet-1-POs, (C′) DiR-Tf-POs, and (D′) DiR-Tf/Tet-1-POs. Abbreviations: DiR, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide; POs, polymersomes; Tf, transferrin.

Figure 6

In vitro release of curcumin from Tf/Tet-1-POs (n=3). Abbreviations: Tf, transferrin; POs, polymersomes.

Figure 7

Pharmacokinetic parameters and brain transport properties of various ligands-modified POs loaded with curcumin administered by iv injection to mice (n=6). Notes: (A) BBB permeability–surface efficiency (PS). (B) Brain tissue uptake rate (% ID/g brain). PS refers to the brain permeability surface area product. *P<0.05 values indicate the difference as compared with the POs control group. Abbreviations: POs, polymersomes; iv, intravenous; BBB, blood–brain barrier; Tf, transferrin.

Figure 8

Neuroprotection offered by various ligands-modified POs loaded with curcumin against amyloid-β_1–42-induced cognitive dysfunction in mice estimated during the Morris water maze test. Notes: (A) Behavioral test procedures performed in the first 5 days. (B) A spatial probe trial carried out on the sixth day. Sham control: saline was injected instead of amyloid-β_1–42; AD control: intravenous administration of saline was carried out. ^▼P<0.05, significant difference compared with the sham control; *P<0.05, significant difference compared with the AD control (n=8). Abbreviations: POs, polymersomes; AD, Alzheimer’s disease; Cur, curcumin; Tf, transferrin.