Cooperative Hierarchical Self-Assembly of Peptide Dendrimers and Linear Polypeptides into Nanoarchitectures Mimicking Viral Capsids

pH-Responsive chimaeric pepsomes based on asymmetric poly(ethylene glycol)-b-poly(l-leucine)-b-poly(l-glutamic acid) triblock copolymer for efficient loading and active intracellular delivery of doxorubicin hydrochloride

pH-Responsive chimaeric polypeptide-based polymersomes (refer to as pepsomes) were designed and developed from asymmetric poly(ethylene glycol)-b-poly(l-leucine)-b-poly(l-glutamic acid) (PEG-PLeu-PGA, PEG is longer than PGA) triblock copolymers for efficient encapsulation and triggered intracellular delivery of doxorubicin hydrochloride (DOX·HCl). PEG-PLeu-PGA was conveniently prepared by sequential ring-opening polymerization of l-leucine N-carboxyanhydride and γ-benzyl-l-glutamate N-carboxyanhydride using PEG-NH2 as an initiator followed by deprotection. Pepsomes formed from PEG-PLeu-PGA had unimodal distribution and small sizes of 64-71 nm depending on PLeu block lengths. Interestingly, these chimaeric pepsomes while stable at pH 7.4 were quickly disrupted at pH 5.0, likely due to alternation of ionization state of the carboxylic groups in PGA that shifts PGA blocks from hydrophilic and random coil structure into hydrophobic and α-helical structure. DOX·HCl could be actively loaded into the watery core of pepsomes with a high loading efficiency. Remarkably, the in vitro release studies revealed that release of DOX·HCl was highly dependent on pH, in which about 24.0% and 75.7% of drug was released at pH 7.4 and 5.0, respectively, at 37 °C in 24 h. MTT assays demonstrated that DOX·HCl-loaded pepsomes exhibited high antitumor activity, similar to free DOX·HCl in RAW 264.7 cells. Moreover, they were also potent toward drug-resistant MCF-7 cancer cells (MCF-7/ADR). Confocal microscopy studies showed that DOX·HCl-loaded pepsomes delivered and released drug into the cell nuclei of MCF-7/ADR cells in 4 h, while little DOX·HCl fluorescence was observed in MCF-7/ADR cells treated with free drug under otherwise the same conditions. These chimaeric pepsomes with facile synthesis, efficient drug loading, and pH-triggered drug release behavior are an attractive alternative to liposomes for targeted cancer chemotherapy.

Recent developments and applications of bioinspired dendritic polymers

This review highlights the bioinspired applications of dendritic polymers, focusing on their structure–function relationship to natural biomolecules such as proteins.

Virus-inspired mimics: self-assembly of dendritic lipopeptides into arginine-rich nanovectors for improving gene delivery

With inspirations from natural viruses, arginine-containing dendritic lipopeptides were designed for bioinspired fabrication.

Controlling the number of dendrimers in dendrimicelle nanoconjugates from 1 to more than 100

Herein, we present a facile strategy to controllably build up dendrimicelles by self-assembly of anionic PAMAM dendrimers with cationic-neutral diblock copolymers. We present a systematic study incorporating a full decade (0-9) of dendrimer generations, tracing the gradual variation from aggregates (G0 and G1) to self-assembled micelles (G2-G8), and an unidendrimer micelle structure (G9) by different scattering techniques (light and X-ray). The formed micelles (G2-G9) are spherical in shape with a hydrodynamic radius of about 25 nm. Interestingly, the micellar size, structure and number of incorporated block copolymers are independent of the dendrimer generation (for G2 to G9), while the aggregation number of the dendrimers decreases from 108 to 1, and the stability of the micelles increases upon an increase in the dendrimer generation. Moreover, the micelles with lower generation dendrimers transform from spherical into worm-like structures upon an increase in the positive charge fraction (excess polymers) or ionic strength, while micelles with higher generation dendrimers do not show such a transition. This differential behavior is in-line with a change from a flexible configuration into rigid globular nanoparticles with increasing dendrimer generation. The reported systematic investigation of dendrimicelles comprising a full decade of dendrimer generations provides the basis for versatile strategies focused on building up new (multi)functional materials, e.g. by packing multiple types of dendrimers with different functional groups or encapsulated cargos controllably within one micelle.

Bio-inspired supramolecular hybrid dendrimers self-assembled from low-generation peptide dendrons for highly efficient gene delivery and biological tracking

Currently, supramolecular self-assembly of dendrons and dendrimers emerges as a powerful and challenging strategy for developing sophisticated nanostructures with excellent performances. Here we report a supramolecular hybrid strategy to fabricate a bio-inspired dendritic system as a versatile delivery nanoplatform. With a rational design, dual-functionalized low-generation peptide dendrons (PDs) self-assemble onto inorganic nanoparticles via coordination interactions to generate multifunctional supramolecular hybrid dendrimers (SHDs). These SHDs exhibit well-defined nanostructure, arginine-rich peptide corona, and fluorescent signaling properties. As expected, our bio-inspired supramolecular hybrid strategy largely enhances the gene transfection efficiency of SHDs approximately 50 000-fold as compared to single PDs at the same R/P ratio. Meanwhile the bio-inspired SHDs also (i) provide low cytotoxicity and serum resistance in gene delivery; (ii) provide inherent fluorescence for tracking intracellular pathways including cellular uptake, endosomal escape, and gene release; and (iii) work as an alternative reference for monitoring desired protein expression. More importantly, in vivo animal experiments demonstrate that SHDs offer considerable gene transfection efficiency (in muscular tissue and in HepG2 tumor xenografts) and real-time bioimaging capabilities. These SHDs will likely stimulate studies on bio-inspired supramolecular hybrid dendritic systems for biomedical applications both in vitro and in vivo.

Core-shell supramolecular gelatin nanoparticles for adaptive and "on-demand" antibiotic delivery

The treatment of bacterial infection is one of the most challenging tasks in the biomedical field. Antibiotics were developed over 70 years and are regarded as the most efficient type of drug to treat bacterial infection. However, there is a concern that the overuse of antibiotics can lead to a growing number of multidrug-resistant bacteria. The development of antibiotic delivery systems to improve the biodistribution and bioavailability of antibiotics is a practical strategy for reducing the generation of antibiotic resistance and increasing the lifespan of newly developed antibiotics. Here we present an antibiotic delivery system (Van⊂SGNPs@RBC) based on core-shell supramolecular gelatin nanoparticles (SGNPs) for adaptive and "on-demand" antibiotic delivery. The core composed of cross-linked SGNPs allows for bacterial infection-microenvironment responsive release of antibiotics. The shell coated with uniform red blood cell membranes executes the function of disguise for reducing the clearance by the immune system during the antibiotic delivery, as well as absorbs the bacterial exotoxin to relieve symptoms caused by bacterial infection. This approach demonstrates an innovative and biomimetic antibiotic delivery system for the treatment of bacterial infection with a minimum dose of antibiotics.

Smart nanovehicles based on pH-triggered disassembly of supramolecular peptide-amphiphiles for efficient intracellular drug delivery

A novel type of nanovehicle (NV) based on stimuli-responsive supramolecular peptide-amphiphiles (SPAs, dendritic poly (L-lysine) non-covalently linked poly (L-leucine)) is developed for intracellular drug delivery. To determine the pH-dependent mechanism, the supramolecular peptide-amphiphile system (SPAS) is investigated at different pH conditions using a variety of physical and chemical approaches. The pH-triggered disassembly of SPAS can be attributed to the disappearance of non-covalent interactions within SPAs around the isoelectric point of poly (L-leucine). SPAS is found to encapsulate guest molecules at pH 7.4 but release them at pH 6.2. In this way, SPAS is able to act as a smart NV to deliver its target to tumor cells using intracellular pH as a trigger. The DOX-loaded NVs are approximately 150 nm in size. In vitro release profiles and confocal laser scanning microscopy (CLSM) images of HepG2 cells confirm that lower pH conditions can trigger the disassembly of NVs and so achieve pH-dependent intracellular DOX delivery. In vitro cytotoxicity of the DOX-loaded NVs to HepG2 cells demonstrate that the smart NVs enhance the efficacy of hydrophobic DOX. Fluorescence-activated cell sorting (FACS) and CLSM results show that the NVs can enhance the endocytosis of DOX into HepG2 cells considerably and deliver DOX to the nuclei.

Functional and biodegradable dendritic macromolecules with controlled architectures as nontoxic and efficient nanoscale gene vectors

Gene therapy has provided great potential to revolutionize the treatment of many diseases. This therapy is strongly relied on whether a delivery vector efficiently and safely directs the therapeutic genes into the target tissue/cells. Nonviral gene delivery vectors have been emerging as a realistic alternative to the use of viral analogs with the potential of a clinically relevant output. Dendritic polymers were employed as nonviral vectors due to their branched and layered architectures, globular shape and multivalent groups on their surface, showing promise in gene delivery. In the present review, we try to bring out the recent trend of studies on functional and biodegradable dendritic polymers as nontoxic and efficient gene delivery vectors. By regulating dendritic polymer design and preparation, together with recent progress in the design of biodegradable polymers, it is possible to precisely manipulate their architectures, molecular weight and chemical composition, resulting in predictable tuning of their biocompatibility as well as gene transfection activities. The multifunctional and biodegradable dendritic polymers possessing the desirable characteristics are expected to overcome extra- and intracellular obstacles, and as efficient and nontoxic gene delivery vectors to move into the clinical arena.

Polymeric micelles with π–π conjugated moiety on glycerol dendrimer as lipophilic segments for anticancer drug delivery

Novel polymeric micelles with cinnamate moieties immobilized on glycerol dendrimer as lipophilic segments were reported as carriers for drug delivery.

Syntheses, Structures, Characterisation, and Spectroscopic Properties of CuI and AgI Complexes with Extended C–H···π and π···π Interactions

Based on the ligands N,N′-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (pmb) and N,N′-bis(pyridin-2-ylmethylene)biphenyl-4,4′-diamine (pmbb), the three compounds [Cu2(pmb) (PPh3)2(Cl)2] (1), [Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)2·2DMF (2), and [Ag2(pmbb)(PPh3)2] (ClO4)2 (3) have been synthesised and characterised. Structural analysis reveals that all of these complexes contain 1D supramolecular arrays, with different variations in π-stacking patterns and intermolecular C–H···π interactions. Crystal structures of 1 and 2 contain 1D tape-like arrays formed by C–H···π and π···π interactions, and an ordered-layer-lattice of DMF and BF4– in 2 is located between the one-dimensional array. For 3, π-stacking interactions lead to the construction of 1D supramolecular arrays and a 2D network. The results indicate that C–H···π and π···π interactions play an important role in the construction of the supramolecular structure. In addition, the absorption peaks of complexes 1 and 3 in the solid state at room temperature show intraligand charge transfer and metal-to-ligand charge transfer absorptions. The optical and fluorescent properties of 2 were also studied in acetonitrile solution at room temperature.

Progressive macromolecular self-assembly: from biomimetic chemistry to bio-inspired materials

Macromolecular self-assembly (MSA) has been an active and fruitful research field since the 1980s, especially in this new century, which is promoted by the remarkable developments in controlled radical polymerization in polymer chemistry, etc. and driven by the demands in bio-related investigations and applications. In this review, we try to summarize the trends and recent progress in MSA in relation to biomimetic chemistry and bio-inspired materials. Our paper covers representative achievements in the fabrication of artificial building blocks for life, cell-inspired biomimetic materials, and macromolecular assemblies mimicking the functions of natural materials and their applications. It is true that the current status of the deliberately designed and obtained nano-objects based on MSA including a variety of micelles, multicompartment vesicles, and some hybrid and complex nano-objects is at their very first stage to mimic nature, but significant and encouraging progress has been made in achieving a certain similarity in morphologies or properties to that of natural ones. Such achievements also demonstrate that MSA has played an important and irreplaceable role in the grand and long-standing research of biomimetic and bio-inspired materials, the future success of which depends on mutual and persistent efforts in polymer science, material science, supramolecular chemistry, and biology.

Star-shaped polymer consisting of a porphyrin core and poly(L-lysine) dendron arms: synthesis, drug delivery, and in vitro chemo/photodynamic therapy

A novel star-shaped polymer, porphyrin-poly(L-lysine) dendrons (PP-PLLD), is synthesized by the click reaction between azido-modified porphyrin and propargyl focal point poly(L-lysine) dendrons. Its chemical structure is characterized by (1) H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography (GPC) is analyses etc. Due to its amphiphilic property, the obtained PP-PLLD has a low critical micelle concentration in an aqueous solution, and can load doxorubicin (DOX) with a loading amount of 64 μg mg(-1) . By in vitro toxicity assay, PP-PLLD has no dark cytotoxicity but has significant phototoxicity. Moreover, DOX-loaded PP-PLLD shows a higher cytotoxicity under the light condition than PP-PLLD or DOX alone, suggesting PP-PLLD has a potential application in combined photodynamic therapy and chemotherapy.

Dendronized heparin-doxorubicin conjugate based nanoparticle as pH-responsive drug delivery system for cancer therapy

Heparin drug conjugates are currently investigated as excellent candidates for drug delivery vehicles. In this study, we report the preparation and characterization of dendronized heparin-doxorubicin (heparin-DOX) conjugate as pH-sensitive drug delivery vehicle by combination of the features of dendrimer and heparin. Dynamic light scattering (DLS) and transmission electron microscope (TEM) studies demonstrated the dendronized heparin-DOX conjugate self-assembled into compact nanoparticles with negatively charged surface. The nanoparticles with 9.0 wt% (weight percent) of doxorubicin (DOX) showed pH-sensitive property due to the faster drug release rate at pH 5.0 and slow release rate at pH 7.4 aqueous. The nanoparticles were shown to effectively kill cancer cells in vitro. Notablely, the nanoparticles resulted in strong antitumor activity, high antiangiogenesis effects and induced apoptosis on the 4T1 breast tumor model due to the evidences from mice weight shifts, tumor weights, tumor growth curves, immunohistochemical assessment and histological analysis. It's also noteworthy that dendronized heparin and its nanoparticle with drug demonstrated no significant toxicity to healthy organs of both tumor-bearing and healthy mice, which was confirmed by histological analysis compared with free drug DOX. The dendronized heparin-DOX conjugate based nanopatilce with high antitumor activity and low side effects may be therefore a potential nanoscale drug delivery vehicle for breast cancer therapy.

Efficacious hepatoma-targeted nanomedicine self-assembled from galactopeptide and doxorubicin driven by two-stage physical interactions

Polymers bearing pendant galactosyl group are attractive for targeted intracellular antitumor drug delivery to hepatoma cells (e.g. HepG2 and SMMC7721 cells) with asialoglycoprotein receptor (ASGP-R). Herein, a series of galactopeptides was synthesized through ring-opening polymerization of L-glutamate N-carboxyanhydride, deprotection of benzyl group and subsequent Huisgens cycloaddition "click" reaction with azide-modified galactosyl group. The copolypeptides were revealed to have excellent hemocompatibilities, and cell and tissue compatibilities, which rendered their potential for drug delivery applications. The hepatoma-targeted micellar nanoparticle (i.e. nanomedicine) was fabricated by cooperative self-assembly of galactopeptide and doxorubicin (DOX) induced by two-stage physical interactions. In vitro DOX release from nanomedicine was accelerated in the intracellular acidic condition. Through the recognition between galactose ligand and ASGP-R of HepG2 cells, the endocytosis of galactosylated nanomedicine was significantly promoted, which was demonstrated by confocal laser scanning microscopy and flow cytometry. Remarkably, the galactose-decorated nanomedicine retained much higher antitumor activity toward HepG2 cells in contrast to the nanomedicine without galactosyl group in vitro and in vivo. The above superiorities indicated that the galactosylated nanomedicine possessed great promising for hepatoma-targeted chemotherapy.