Brain Targeting, Antioxidant Polymeric Nanoparticles for Stroke Drug Delivery and Therapy

Abstract

Ischemic stroke is a leading cause of death and disability and remains without effective treatment options. Improved treatment of stroke requires efficient delivery of multimodal therapy to ischemic brain tissue with high specificity. Here, this article reports the development of multifunctional polymeric nanoparticles (NPs) for both stroke treatment and drug delivery. The NPs are synthesized using an reactive oxygen species (ROS)-reactive poly (2,2'-thiodiethylene 3,3'-thiodipropionate) (PTT) polymer and engineered for brain penetration through both thrombin-triggered shrinkability and AMD3100-mediated targeted delivery. It is found that the resulting AMD3100-conjugated, shrinkable PTT NPs, or ASPTT NPs, efficiently accumulate in the ischemic brain tissue after intravenous administration and function as antioxidant agents for effective stroke treatment. This work shows ASPTT NPs are capable of efficient encapsulation and delivery of glyburide to achieve anti-edema and antioxidant combination therapy, resulting in therapeutic benefits significantly greater than those by either the NPs or glyburide alone. Due to their high efficiency in brain penetration and excellent antioxidant bioactivity, ASPTT NPs have the potential to be utilized to deliver various therapeutic agents to the brain for effective stroke treatment.

Keywords: anti-edema; antioxidants; blood-brain barrier; shrinkable nanoparticles; stroke.

Figure 1.

Schematic diagrams of ASPTT NP design and combination therapy for stroke treatment. a) Construction of ASPTT NPs through self-assembly of PEG-PTT-T-PEG block copolymer and size shrink behavior of ASPTT NPs in response to thrombin. b) Brain targeting and BBB penetration of ASPTT NPs in stroke-bearing mice. c) Antioxidant therapy of ASPTT NPs in ischemic brain by reacting with excess ROS. d) Anti-edema of ASPTT NPs through delivering glyburide.

Figure 2.

Synthesis and characterization of polymers. a) Enzyme-catalyzed synthesis of carboxyl-terminated PEG-PTT block copolymer. b) Characterization of PEG-PTT block copolymers. c) Chemical synthesis of PEG-PTT-peptide and PEG-PTT-T-PEG.

Figure 3.

Characterization and evaluation of thrombin responsive PEG-PTT-T-PEG NPs. a–c) DLS (left) and TEM (right) analyses of PEG-PTT-T-PEG NPs in PBS with thrombin (100 nm). Scale bar: 100 nm. d–i) Representative images (d,f,h) and semi-quantification (e,g,i) of NPs in stroke mice receiving the indicated treatments.

Figure 4.

Characterization of PEG-PTT-T-PEG NPs for stroke treatment. a) Characterization of the ROS scavenging effect of PEG-PTT-T-PEG NPs by DCFDA assay. Representative images (b) and quantification (d) of cerebral infarction in MCAO mice receiving treatment of the indicated PEG-PTT-T-PEG NPs. c) Western blot analysis of ischemic brain tissues isolated from mice with and without PEG-PTT-T-PEG NPs treatment. Representative images (e) and semi-quantification (f) of NPs in the brains of MCAO mice received with the indicated treatment.

Figure 5.

Enhancing delivery of PEG-PTT-T-PEG NPs to the ischemic brain through CXCR4 targeting. a) Western Blot analysis of the expression of CXCR4 in the ischemic and normal brain. b) Representative images of brain and brain slices and d) semi-quantification of NPs in the brains from mice receiving the indicated treatment. c) Representative fluorescence images of CY5.5-loaded NPs (red) in the stroke regions (right side of dotted line).

Figure 6.

Characterization of glyburide-loaded ASPTT NPs for stroke treatment. a) Release of glyburide in PBS at 37 °C with/without thrombin (100 nm) and ROS (10 μm). b) Representative images and c) quantification of cerebral infarction in MCAO mice receiving the indicated treatments. d) Neurological scores (day 3 after surgery, n = 5) and e) Kaplan–Meier survival analysis (n = 10) of MCAO mice receiving the indicated treatments. Representative images (f) and quantification (g) of Evans blue extravasation in MCAO mice received the indicated treatments.