Acid-Induced Activated Cell-Penetrating Peptide-Modified Cholesterol-Conjugated Polyoxyethylene Sorbitol Oleate Mixed Micelles for pH-Triggered Drug Release and Efficient Brain Tumor Targeting Based on a Charge Reversal Mechanism

Glioblastoma multiforme is the most devastating malignant brain tumor in adults. Even with the standard care of therapy, the prognosis remains dismal due to tumor heterogeneity, tumor infiltration, and, more importantly, the restrictive nature of the blood-brain barrier (BBB). To overcome the challenge of effectively delivering therapeutic cargo into the brain, herein a "smart", multifunctional polymeric micelle was developed using a cholesterol-conjugated polyoxyethylene sorbitol oleate. A cell-penetrating peptide, arginine-glycine repeats (RG)₅, was incorporated into the micelles to improve cellular uptake, while a pH-sensitive masking sequence, histidine-glutamic acid repeats (HE)₅, was introduced for charge shielding to minimize nonspecific binding and uptake at physiological pH. Results demonstrated that (RG)₅- and (HE)₅-modified mixed micelles were optimized using this strategy to effectively mask the cationic charges of the activated cell-penetrating peptide (RG)₅ at physiological pH, i.e., limiting internalization, and were selectively triggered in response to a mildly acidic microenvironment in vitro based on a charge reversal mechanism. In vivo results further confirmed that such micelles preferentially accumulated in both brain and tumor tissues in both xenograft and orthotropic glioma mouse models. Furthermore, micelles significantly inhibited tumor growth with limited toxicity to peripheral tissues. The combination of BBB penetration, tumor targeting, potent efficacy, and high tolerance of these micelles strongly suggests that they could be a promising candidate for safe and effective drug delivery to the brain.

Visual and Colorimetric High-Throughput Analysis of Chiral Carboxylic Acids Based on Enantioselective Charge Shielding of Gold Nanoparticles

Because chiral carboxylic acids (CCAs) are a class of important biological molecules and common functional moieties found in pharmaceutical molecules, the chiral analysis of CCAs has received much attention. Herein, we developed a simple, rapid, and cost-effective method for visual and colorimetric high-throughput analysis of CCAs using chiral di-imine structure-modified gold nanoparticles (C-AuNPs) as the probe. The C-AuNPs are positively charged in the presence of zinc ion, and they can be enantioselectively shielded by the negatively charged CCA enantiomers. Therefore, upon the addition of different concentrations and enantiomeric excess (ee) of CCAs, the C-AuNP-based sensor shows the different levels of aggregation along with the visual changes in solution color, which can achieve simultaneous analysis of the concentration and ee of CCAs. The chiral recognition mechanism based on C-AuNPs was investigated by the determination of binding constants ( K) and molecular simulation methods. Our approach is expected to have the wide-ranging applications in the developing region for enantio-sensing of various chiral drugs and biomolecules.

Physical Polyurethane Hydrogels via Charge Shielding through Acids or Salts

Physical hydrogels with tunable stress-relaxation and excellent stress recovery are formed from anionic polyurethanes via addition of acids, monovalent salts, or divalent salts. Gel properties can be widely adjusted through pH, salt valence, salt concentration, and monomer composition. We propose and investigate a novel gelation mechanism based on a colloidal system interacting through charge repulsion and chrage shielding, allowing a broad use of the material, from acidic (pH 4-5.5) to pH-neutral hydrogels with Young's moduli ranging from 10 to 140 kPa.