Self-Assembled ROS-Sensitive Polymer-Peptide Therapeutics Incorporating Built-in Reporters for Evaluation of Treatment Efficacy.

One of the major challenges in current cancer therapy is to maximize therapeutic effect and evaluate tumor progression under the scheduled treatment protocol. To address these challenges, we synthesized the cytotoxic peptide (KLAKLAK)2 (named KLAK) conjugated amphiphilic poly(ß-thioester)s copolymers (H-P-K) composed of reactive oxygen species (ROS) sensitive backbones and hydrophilic polyethylene glycol (PEG) side chains. H-P-K could self-assemble into micelle-like nanoparticles by hydrophobic interaction with copolymer backbones as cores and PEG and KLAK as shells. The assembled polymer-peptide nanoparticles remarkably improved cellular internalization and accumulation of therapeutic KLAK in cells. Compared to free KLAK peptide, the antitumor activity of H-P-K was significantly enhanced up to ∼400 times, suggesting the effectiveness of the nanoscaled polymer-peptide conjugation as biopharmaceuticals. The higher antitumor activity of nanoparticles was attributed to the efficient disruption of mitochondrial membranes and subsequent excessive ROS production in cells. To realize the ROS monitoring and treatment evaluation, we encapsulated squaraine (SQ) dyes as built-in reporters in ROS-sensitive H-P-K micelles. The overgenerated ROS around mitochondria stimulated the swelling of nanoparticles and subsequent release of SQ, which formed H-aggregates and significantly increased the photoacoustic (PA) signal. We believed that this self-assembled polymer-peptide nanotherapeutics incorporating built-in reporters has great potential for high antitumor performance and in situ treatment evaluation.

Recent progress of therapeutic peptide based nanomaterials: from synthesis and self-assembly to cancer treatment.

Peptides have shown great potential in cancer treatment due to their good biocompatibility and low toxicity. However, the bioavailability and adverse immune response of peptides limit their further translation from bench to bedside. Over the past few decades, various peptide-based nanomaterials have been developed for drug delivery and cancer treatment. Compared with therapeutic peptides alone, self-assembled peptide nanomaterials have obvious advantages, such as improved stability and biodistribution for high-performance cancer therapy. In this review, we have described the synthesis, self-assembly and the anti-cancer application of therapeutic peptides and their conjugates, particularly polymer-peptide conjugates (PPCs).

Enzyme-sensitive cytotoxic peptide-dendrimer conjugates enhance cell apoptosis and deep tumor penetration.

Peptide nanodrugs have been developed as promising antitumor chemotherapeutics because they partially overcome the drawbacks of free peptide drugs, but insufficient tumor penetration and interference of peptide function limit their further application. In this work, we have developed multifunctional peptide conjugated dendrimers for improving tumor penetration, cancer cell-specific peptide delivery and anticancer ability. The cytotoxic peptide KLAK, cell-penetrating peptide TAT and matrix metalloproteinase 2 (MMP2)-sensitive peptide-poly(ethylene glycol) (PEG) were conjugated onto dendrimers by one-pot synthesis to gain PKT-S-PEG. The enzyme-sensitive properties and incubation stability of the dendrimers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, the cell viability, internalization pathway, mitochondria-regulated apoptosis and tumor penetration ability were measured by CCK-8 assay, lysosome colocalization, JC-1 assay and multicellular spheroid (MCS) experiments, respectively, in human primary glioblastoma (U87) cells. PKT-S-PEG showed significantly enhanced intracellular delivery performance, antitumor efficacy and deep tumor penetration capacity compared to a control non-MMP2 sensitive dendrimer PKT-C-PEG. The MMP2-overexpressing tumor microenvironment caused deprotection by removal of PEG, resulting in the decrease of particle size and exposure of KLAK and TAT, which enhanced tumor penetration, the entry of bioactive peptides into cells and subsequently the effective disruption of mitochondria. We believe that the peptide-dendrimer conjugate has potential for specific and effective delivery of peptide-based therapeutics into tumors.