Thrombin-Responsive, Brain-Targeting Nanoparticles for Improved Stroke Therapy

Abstract

Current treatments for ischemic stroke are insufficient. The lack of effective pharmacological approaches can be mainly attributed to the difficulty in overcoming the blood-brain barrier. Here, we report a simple strategy to synthesize protease-responsive, brain-targeting nanoparticles for the improved treatment of stroke. The resulting nanoparticles respond to proteases enriched in the ischemic microenvironment, including thrombin or matrix metalloproteinase-9, by shrinking or expanding their size. Targeted delivery was achieved using surface conjugation of ligands that bind to proteins that were identified to enrich in the ischemic brain using protein arrays. By screening a variety of formulations, we found that AMD3100-conjugated, size-shrinkable nanoparticles (ASNPs) exhibited the greatest delivery efficiency. The brain targeting effect is mainly mediated by AMD3100, which interacts with CXCR4 that is enriched in the ischemic brain tissue. We showed that ASNPs significantly enhanced the efficacy of glyburide, a promising stroke therapeutic drug whose efficacy is limited by its toxicity. Due to their high efficiency in penetrating the ischemic brain and low toxicity, we anticipate that ASNPs have the potential to be translated into clinical applications for the improved treatment of stroke patients.

Autocatalytic Delivery of Brain Tumor–Targeting, Size‐Shrinkable Nanoparticles for Treatment of Breast Cancer Brain Metastases

“…Accordingly, we synthesized maleimide‐terminated PEG‐PCL‐ NECP ‐PEG, or Mal‐PEG‐PCL‐ NECP ‐PEG, which were obtained through the same synthesis procedures as that for PEG‐PCL‐ NECP ‐PEG, except that MAL‐PEG‐OH was used to initiate the ring‐opening polymerization of ε‐caprolactone (Figure S4, Supporting Information). After the nanoprecipitation procedure, Mal‐PEG‐PCL‐ NECP ‐PEG NPs were incubated with AMD3100, which was pre‐thiolated according to our recently published procedure 16a. We characterized and compared the NPs with and without AMD3100 in mice that bear comparable tumor loads (Figure 4c, upper panel), and found that conjugation of AMD3100 significantly enhanced the accumulation of NPs in tumors by 11.9‐fold (Figure 4c,d).…”

“…NE‐responsive micellular NPs were synthesized using PEG‐ NECP ‐PCL and PEG‐PCL‐ NECP ‐PEG through the standard nanoprecipitation process 16a. Control non‐responsive NPs were synthesized using PEG‐PCL.…”

“…In seeking target molecules for preferential delivery to BCBMs, we focused on CXCR4, a chemokine receptor that is highly expressed in BCBMs and plays a critical role in metastasis 16c. Analysis by Western Blot and immunostaining confirmed that CXCR4 was highly expressed in metastatic tumors but not in the region without tumors in the brain ( Figure a,b).…”

“…We found that both the size shrinkable and expandable NPs delivered drugs to BCBMs in efficiency significantly greater than non‐responsive NPs. Among the three NPs, the size shrinkable NPs demonstrated the greatest efficiency and thus were selected for further customization for tumor targeting through surface conjugation of AMD3100, a ligand binding with CXCR4 overexpressed in tumor cells 16. We found that conjugation of AMD3100 further enhanced the delivery efficiency.…”

“…NPs were synthesized through nanoprecipitation according to our recent report 16a. Briefly, for synthesis of PEG‐PCL and PEG‐ NECP ‐PCL NPs, the polymers were dissolved in tetrahydrofuran (THF) and added dropwise into deionized water (THF/water = 1:3) under stirring.…”