Brain penetration enhancer-based on amino acid prodrug self-assembling nanoparticles: a streamlined strategy for...

Treating brain malignancies remains a significant challenge because the blood-brain barrier (BBB) restricts the permeability of chemotherapeutic agents in sufficient amounts. One efficient strategy to enhance drug passage through the BBB is targeting brain transporters such as the amino acid and combination with nanoparticles. In the present study, we use hydrophobic phenylalanine (Phe) to modify methotrexate (MTX) as a prodrug to enhance drug penetration into the brain parenchyma. Specifically, phenylalanine-methotrexate prodrug (Phe-MTX) was self-assembled to spherical nanoparticles to form phenylalanine-methotrexate prodrug nanoparticles (Phe-MTX prodrug NPs) to improve brain permeability. The structure of the Phe-MTX prodrug was confirmed by FTIR, ¹HNMR, ¹³CNMR, PXRD, DSC, TGA, and EDX. Particle size, zeta potential, and morphology of Phe-MTX prodrug NPs were analyzed using TEM and DLS methods. Phe-MTX prodrug NPs demonstrated enhanced antitumor activity against human brain tumor U87MG cells compared to untreated MTX. The IC₅₀ values of untreated MTX and Phe-MTX prodrug NPs against U87MG cells after 48 h were 187.64 μg/mL and 78.68 μg/mL, respectively. Compared to the parent drug, Phe-MTX prodrug NPs increased the brain-to-plasma concentration ratio, brain uptake clearance, and the drug's plasma half-life in rats. The Phe-MTX prodrug NPs significantly increased the brain penetration index by approximately nine fold compared to the untreated drug. These results indicate that the amino acid-mediated prodrug approach may be a promising strategy for treating brain malignancies.