Hybrid Melittin Cytolytic Peptide-Driven Ultrasmall Lipid Nanoparticles Block Melanoma Growth <i>in Vivo</i>

The cytolytic peptide melittin is a potential anticancer candidate that may be able to overcome tumor drug resistance due to its lytic properties. However, <i>in vivo</i> applications of melittin are limited due to its main side effect, hemolysis, which is especially pronounced following intravenous administration. Here, we designed a hybrid cytolytic peptide, α-melittin, in which the N-terminus of melittin is linked to the C-terminus of an amphipathic α-helical peptide (α-peptide) <i>via</i> a GSG linker. The strong α-helical configuration allows α-melittin to interact with phospholipids and self-assemble into lipid nanoparticles, with a high efficiency for α-melittin encapsulation (>80%) and a strong ability to control the structure of the nanoparticle (∼20 nm). This α-melittin-based lipid nanoparticle (α-melittin-NP) efficiently shields the positive charge of melittin (18.70 ± 0.90 mV) within the phospholipid monolayer, resulting in the generation of a neutral nanoparticle (2.45 ± 0.56 mV) with reduced cytotoxicity and a widened safe dosage range. Confocal imaging data confirmed that α-melittin peptides were efficiently released from the nanoparticles and were cytotoxic to the melanoma cells. Finally, α-melittin-NPs were administered to melanoma-bearing mice <i>via</i> intravenous injection. The growth of the melanoma cells was blocked by the α-melittin-NPs, with an 82.8% inhibition rate relative to the PBS-treated control group. No side effects of treatment were found in this study. Thus, the excellent properties of α-melittin-NP give it potential clinical applications in solid tumor therapeutics through intravenous administration

Design and Synthesis of a Lead Sulfide Based Nanotheranostic Agent for Computer Tomography/Magnetic Resonance Dual-Mode-Bioimaging-Guided Photothermal Therapy

Dual-modality-imaging-guided photothermal therapy (PTT) exhibits great potential in the field of diagnosis and treatment. Herein, we report a controllable method (atom-transfer radical polymerization) for the preparation of gadolinium­(III)-complex-grafted lead sulfide (GCGLS) nanoparticles. A series of characterizations (such as TEM, HR-TEM, EDX, XRD, FTIR, etc.) prove that GCGLS nanoparticles have been successfully prepared. The GCGLS nanoparticles with ultrasmall sizes (ca. 11 nm) have quite strong photoabsorption intensity in the near-infrared (NIR) region because of a low S vacancy concentration of lead sulfide. As the addition amount of gadolinium­(III) complexes increases, the sizes of the GCGLS nanoparticles show no evidence of changing. The temperature of the GCGLS nanoparticle solution can quickly elevate to 57.5 °C in 10 min after NIR laser irradiation (1.5 W cm^–2) at 808 nm; this result reveals that it possesses high photothermal conversion efficiency (∼31%). When the GCGLS nanoparticles are injected into the mice, it is clearly observed that there is efficient accumulation in the tumor site. Moreover, the GCGLS nanoparticles also show excellent prominent X-ray computer tomography (CT) and <i>T</i>₁-weighted magnetic resonance (<i>T</i>₁-MR) imaging in vitro/vivo. By the combination of GCGLS and NIR laser irradiation, an effective tumor treatment experiment is conducted in mice. Therefore, the prepared GCGLS nanoparticles with dual-modality-imaging-guided PTT can be used as potential diagnosis and treatment reagents for clinical applications

Mechanistic Insights into LDL Nanoparticle-Mediated siRNA Delivery

Although small interfering RNA (siRNA) can silence the expression of disease-related genes, delivery of these highly charged molecules is challenging. Delivery approaches for siRNAs are actively being pursued, and improved strategies are required for nontoxic and efficient delivery for gene knockdown. Low density lipoprotein (LDL) is a natural and endogenous nanoparticle that has a rich history as a delivery vehicle. Here, we examine purified LDL nanoparticles as carriers for siRNAs. When siRNA was covalently conjugated to cholesterol, over 25 chol-siRNA could be incorporated onto each LDL without changing nanoparticle morphology. The resulting LDL-chol-siRNA nanoparticles were selectively taken up into cells via LDL receptor mediated endocytosis, resulting in enhanced gene silencing compared to free chol-siRNA (38% gene knock down versus 0% knock down at 100 nM). However, silencing efficiency was limited by the receptor-mediated entrapment of the LDL-chol-siRNA nanoparticles in endolysosomes. Photochemical internalization demonstrated that endolysosome disruption strategies significantly enhance LDL-mediated gene silencing (78% at 100 nM)

Melittin-Containing Hybrid Peptide Hydrogels for Enhanced Photothermal Therapy of Glioblastoma

The design of biocompatible and efficacious anticancer biomaterials to achieve relatively low tumor recurrence rates is the main pursuit of cancer photothermal therapy (PTT). RADA16-I is a synthetic amphiphilic peptide with the sequence RADARADARADARADA that can self-assemble into a peptide nanofiber hydrogel. In this study, we synthesized a novel melittin–RADA₃₂–indocyanine green (ICG) hydrogel (“MRI hydrogel”), which contains melittin in the peptide hydrogel backbone and ICG in the hydrogel matrix, for enhanced PTT of glioblastomas. The MRI hydrogel exhibited physiologic characteristics similar to those of the RADA₁₆ hydrogel, while displaying concentration-dependent cytotoxicity to C6 glioma cells and photothermal effects. The in vivo biodistribution of the MRI hydrogel was visualized by near-infrared fluorescence and photoacoustic imaging. More importantly, in vivo PTT provided by the MRI hydrogel significantly reduced the tumor size and the tumor recurrence rate compared with the RADR₁₆-ICG hydrogel and other controls, suggesting a synergistic effect of MRI hydrogel-carried melittin and ICG-based PTT treatment. Thus, MRI provides an alternative tool for the safe and efficient PTT treatment of tumors

Tumor Ablation and Therapeutic Immunity Induction by an Injectable Peptide Hydrogel

Immunosuppressive tumor microenvironments (TMEs) create tremendous obstacles for an effective cancer therapy. Herein, we developed a melittin-RADA₃₂ hybrid peptide hydrogel loaded with doxorubicin (DOX) for a potent chemoimmunotherapy against melanoma through the active regulation of TMEs. The formed melittin-RADA₃₂-DOX (MRD) hydrogel has an interweaving nanofiber structure and exhibits excellent biocompatibility, controlled drug release properties both <i>in vitro</i> and <i>in vivo</i>, and an enhanced killing effect to melanoma cells. A single-dose injection of MRD hydrogel retarded the growth of primary melanoma tumors by more than 95% due to loaded melittin and DOX, with concomitant recruitment of activated natural killer cells in the tumors. Furthermore, MRD hydrogel can activate dendritic cells of draining lymph nodes, specifically deplete M2-like tumor-associated macrophages (TAMs), and produce active, cytotoxic T cells to further defend the cells against remaining tumors, providing potent anticancer efficacy against subcutaneous and metastatic tumors <i>in vivo</i>. Multidose injection of MRD hydrogel eliminated 50% of the primary tumors and provided a strong immunological memory effect against tumor rechallenge after eradication of the initial tumors. Owing to its abilities to perform controlled drug release, regulate innate immune cells, deplete M2-like TAMs, direct anticancer and immune-stimulating capabilities, and reshape immunosuppressive TMEs, MRD hydrogel may serve as a powerful tool for anticancer applications