Targeted delivery of intracellularly active diagnostics and therapeutics in vivo is a major challenge in cancer nanomedicine. A nanocarrier should possess long circulation time yet be small and stable enough to freely navigate through interstitial space to deliver its cargo to targeted cells. Herein, it is shown that by adding targeting ligands to nanoparticles that mimic high-density lipoprotein (HDL), tumor-targeted sub-30-nm peptide-lipid nanocarriers are created with controllable size, cargo loading, and shielding properties. The size of the nanocarrier is tunable between 10 and 30 nm, which correlates with a payload of 15-100 molecules of fluorescent dye. Ligand-directed nanocarriers targeting epidermal growth factor receptor (EGFR) are confirmed both in vitro and in vivo. The nanocarriers show favorable circulation time, tumor accumulation, and biodistribution with or without the targeting ligand. The EGFR targeting ligand is proved to be essential for the EGFR-mediated tumor cell uptake of the nanocarriers, a prerequisite of intracellular delivery. The results demonstrate that targeted HDL-mimetic nanocarriers are useful delivery vehicles that could open new avenues for the development of clinically viable targeted nanomedicine.

Getting straight to the point: A peptide–phospholipid‐based biomimetic nanocarrier was developed that can transport cargo molecules directly into cytosolic compartments through a non‐endocytotic uptake mechanism mediated by scavenger receptor class B type I (SR‐BI; see schematic illustration). The fluorescent image shows the cytosolic localization of a dye (red) delivered by the nanocarrier to SR‐BI‐positive cells (nuclei: blue, membranes: cyan).

The cytolytic peptide melittin is a potential anticancer candidate that may be able to overcome tumor drug resistance due to its lytic properties. However, in vivo 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) via 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 via 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.

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Nasopharyngeal carcinoma (NPC) is a very regional malignant head and neck cancer that has attracted widespread attention for its unique etiology, epidemiology and therapeutic options. To achieve high cure rates in NPC patients, theranostic approaches are actively being pursued and improved efforts remain desirable in identifying novel biomarkers and establishing effective therapeutic approaches with low long-term toxicities. Here, we discovered that the scavenger receptor class B type I (SR-B1) was overexpressed in all investigated NPC cell lines and 75% of NPC biopsies, demonstrating that SR-B1 is a potential biomarker of NPC. Additional functional analysis showed that SR-B1 has great effect on cell motility while showing no significant impact on cell proliferation. As high-density lipoproteins (HDL) exhibit strong binding affinities to SR-B1 and HDL mimetic peptides are reportedly capable of inhibiting tumor growth, we further examined the SR-B1 targeting ability of a highly biocompatible HDL-mimicking peptide-phospholipid scaffold (HPPS) nanocarrier and investigated its therapeutic effect on NPC. Results show that NPC cells with higher SR-B1 expression have superior ability in taking up the core constituents of HPPS. Moreover, HPPS inhibited the motility and colony formation of 5-8F cells, and significantly suppressed the NPC cell growth in nude mice without inducing tumor cell necrosis or apoptosis. These results indicate that HPPS is not only a NPC-targeting nanocarrier but also an effective anti-NPC drug. Together, the identification of SR-B1 as a potential biomarker and the use of HPPS as an effective anti-NPC agent may shed new light on the diagnosis and therapeutics of NPC.

Small interfering RNA (siRNA) is a powerful tool for specifi c gene suppression in vivo and more recently has reached human clinical trials as a potential therapeutic approach. [ 1 ] Due to their highly negative charge, naked siRNAs cannot readily penetrate through cell membranes and thus require delivery strategies. A variety of nonviral delivery approaches have been developed to effi ciently traffi c siRNA into cells, including chemical modifi cation (e.g., cholesterol-siRNA), [ 2 ] conjugation to peptides, [ 3 ] antibodies [ 4 ] or nanoparticles, [ 5 ] electrostatic association with cationic delivery systems, [ 6 ] and encapsulation into lipid nanoparticles. [ 7 ] Therapeutic application of RNA interference (RNAi) requires delivery of siRNAs into the cytoplasm of targeted cells and tissues, where they are recognized and associated with RNA-induced silencing complex (RISC) to perform their function. [ 8 ] This rate-limiting delivery step has been dealt with by several approaches, such as co-encapsulation of fusogenic lipid [ 9 ] or fusogenic peptide, [ 10 ] liposomal bubbles and ultrasound, [ 11 ] laser-induced gene silencing via gold nanoshells, [ 12 ] and photochemical internalization (PCI). [ 13 ] However, these approaches generally disrupt the cytoplasmic membrane or require the uptake of siRNA through endocytosis before the siRNA can be released into the cytoplasm, and therefore improved approaches for cytosolic delivery of siRNA are required.We recently reported a high-density lipoprotein (HDL)-mimicking peptide-phospholipid scaffold (HPPS) nanocarrier for the direct cytosolic delivery of fl uorescent dyes via the scavenger receptor class B type I (SRBI) pathway. [ 14 ] The central components of the HPPS are phospholipids, cholesteryl oleate, and amphipathic α -helical peptides, which mimic apolipoprotein A-I (ApoA-1), the major protein in HDL. The interaction between the self-assembled peptide network and the colloidal phospholipid monolayer enables the HPPS to mimic the behavior of plasma-derived HDL in both structural and functional properties, such as monodisperse size, long circulation half-life, excellent biocompatibility, and more importantly the ability to target SRBI-expressing cancer cells. [ 15 ] The SRBI pathway is particularly attractive for siRNA delivery because of its ability to directly transport payload into the cytosol of targeted cells, thus providing a viable alternative to prevent the intracellularly active siRNA from detrimental endo-lysosomal degradation. [ 16 , 17 ] To investigate the siRNA loading capability and delivery effi ciency of HPPS, bcl-2 oncogene with anti-apoptotic activity was chosen as a cellular RNAi target. Cholesterolmodifi ed bcl-2 siRNA (chol-si-bcl-2) was intercalated into the phospholipid monolayer of HPPS, which resulted in stable HPPS-chol-si-bcl-2 nanoparticles ( Figure 1 A). HPPSchol-si-bcl-2 was purifi ed using fast protein liquid chromatography (FPLC). The fi nal siRNA payload and recovery yield of HPPS-chol-si-bcl-2 were examined by varying the initia...

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HPPS is a safe, efficient nanocarrier for RNAi therapeutics in vivo.