Applying the Retro-Enantio Approach To Obtain a Peptide Capable of Overcoming the Blood-Brain Barrier

Ultrasound-Activated Sensitizers and Applications

Modalities for photo-triggered anticancer therapy are usually limited by their low penetrative depth. Sonotheranostics especially sonodynamic therapy (SDT), which is different from photodynamic therapy (PDT) by the use of highly penetrating acoustic waves to activate a class of sound-responsive materials called sonosensitizers, has gained significant interest in recent years. The effect of SDT is closely related to the structural and physicochemical properties of the sonosensitizers, which has led to the development of new sound-activated materials as sonosensitizers for various biomedical applications. This Review provides a summary and discussion of the types of novel sonosensitizers developed in the last few years and outlines their specific designs and the potential challenges. The applications of sonosensitizers with various functions such as for imaging and drug delivery as well as in combination with other treatment modalities would provide new strategies for disease therapy.

Targeted Nanoswitchable Inhibitors of Protein-Protein Interactions Involved in Apoptosis

Progress in drug delivery is hampered by a lack of efficient strategies to target drugs with high specificity and precise spatiotemporal regulation. The remote control of nanoparticles and drugs with light allows regulation of their action site and dosage. Peptide-based drugs are highly specific, non-immunogenic, and can be designed to cross the plasma membrane. In order to combine target specificity and remote control of drug action, here we describe a versatile strategy based on a generalized template to design nanoswitchable peptides that modulate protein-protein interactions upon light activation. This approach is demonstrated to promote photomodulation of two important targets involved in apoptosis (the interactions Bcl-xL-Bak and MDM2-p53), but can be also applied to a large pool of therapeutically relevant protein-protein interactions mediated by α-helical motifs. The template can be adjusted using readily available information about hot spots (residues contributing most to the binding energy) at the protein-protein interface of interest.

Combined Use of Oligopeptides, Fragment Libraries, and Natural Compounds: A Comprehensive Approach To Sample the Druggability of Vascular Endothelial Growth Factor

The modulation of protein–protein interactions (PPIs) is emerging as a highly promising tool to fight diseases. However, whereas an increasing number of compounds are able to disrupt peptide‐mediated PPIs efficiently, the inhibition of domain–domain PPIs appears to be much more challenging. Herein, we report our results related to the interaction between vascular endothelial growth factor (VEGF) and its receptor (VEGFR). The VEGF–VEGFR interaction is a typical domain–domain PPI that is highly relevant for the treatment of cancer and some retinopathies. Our final goal was to identify ligands able to bind VEGF at the region used by the growth factor to interact with its receptor. We undertook an extensive study, combining a variety of experimental approaches, including NMR‐spectroscopy‐based screening of small organic fragments, peptide libraries, and medicinal plant extracts. The key feature of the successful ligands that emerged from this study was their capacity to expose hydrophobic functional groups able to interact with the hydrophobic hot spots at the interacting VEGF surface patch.

MiniAp-4: A Venom-Inspired Peptidomimetic for Brain Delivery

Drug delivery across the blood–brain barrier (BBB) is a formidable challenge for therapies targeting the central nervous system. Although BBB shuttle peptides enhance transport into the brain non‐invasively, their application is partly limited by lability to proteases. The present study proposes the use of cyclic peptides derived from venoms as an affordable way to circumvent this drawback. Apamin, a neurotoxin from bee venom, was minimized by reducing its complexity, toxicity, and immunogenicity, while preserving brain targeting, active transport, and protease resistance. Among the analogues designed, the monocyclic lactam‐bridged peptidomimetic MiniAp‐4 was the most permeable. This molecule is capable of translocating proteins and nanoparticles in a human‐cell‐based BBB model. Furthermore, MiniAp‐4 can efficiently deliver a cargo across the BBB into the brain parenchyma of mice.

Lipid bilayer crossing--the gate of symmetry. Water-soluble phenylproline-based blood-brain barrier shuttles

Drug delivery to the brain can be achieved by various means, including blood-brain barrier (BBB) disruption, neurosurgical-based approaches, and molecular design. Recently, passive diffusion BBB shuttles have been developed to transport low-molecular-weight drug candidates to the brain which would not be able to cross unaided. The low water solubility of these BBB shuttles has, however, prevented them from becoming a mainstream tool to deliver cargos across membranes. Here, we describe the design, synthesis, physicochemical characterization, and BBB-transport properties of phenylproline tetrapeptides, (PhPro)4, an improved class of BBB shuttles that operates via passive diffusion. These PhPro-based BBB shuttles showed 3 orders of magnitude improvement in water solubility compared to the gold-standard (N-MePhe)4, while retaining very high transport values. Transport capacity was confirmed when two therapeutically relevant cargos, nipecotic acid and l-3,4-dihydroxyphenylalanine (i.e., l-DOPA), were attached to the shuttle. Additionally, we used the unique chiral and conformationally restricted character of the (PhPro)4 shuttle to probe its chiral interactions with the lipid bilayer of the BBB. We studied the transport properties of 16 (PhPro)4 stereoisomers using the parallel artificial membrane permeability assay and looked at differences in secondary structure. Most stereoisomers displayed excellent transport values, yet this study also revealed pairs of enantiomers with high enantiomeric discrimination and different secondary structure, where one enantiomer maintained its high transport values while the other had significantly lower values, thereby confirming that stereochemistry plays a significant role in passive diffusion. This could open the door to the design of chiral and membrane-specific shuttles with potential applications in cell labeling and oncology.