Self-assembled Tat nanofibers as effective drug carrier and transporter

Glutathione-adaptive peptide amphiphile vesicles rationally designed using positionable disulfide-bridges for effective drug transport

The drug loading/releasing capability of GSH-responsive nanovesicles self-assembled from peptide amphiphiles was controlled by varying the location and number of disulfide-linkages in the peptide for the selective drug-release into tumor cells.

Hampering brain tumor proliferation and migration using peptide nanofiber:siPLK1/MMP2 complexes

Aim: To develop a nonviral tool for the delivery of siRNA to brain tumor cells using peptide nanofibers (PNFs). Materials & methods: Uptake of PNFs was evaluated by confocal microscopy and flow cytometry. Gene silencing was determined by RT-qPCR and cell invasion assay. Results: PNFs enter phagocytic (BV-2) and nonphagocytic (U-87 MG) cells via endocytosis and passive translocation. siPLK1 delivered using PNFs reduced the expression of polo-like kinase 1 mRNA and induced cell death in a panel of immortalized and glioblastoma-derived stem cells. Moreover, targeting MMP2 using PNF:siMMP2 reduced the invasion capacity of U-87 MG cells. We show that stereotactic intra-tumoral administration of PNF:siPLK1 significantly extends the survival of tumor bearing mice comparing with the untreated tumor bearing animals. Conclusion: Our results suggest that this nanomedicine-based RNA interference approach deserves further investigation as a potential brain tumor therapeutic tool.

Interface-Enrichment-Induced Instability and Drug-Loading-Enhanced Stability in Inhalable Delivery of Supramolecular Filaments

Filamentous microorganisms traveling in aerosol particles display enhanced deposition and retention in the lungs. Inspired by this shape-related biological effect, we report here on the use of supramolecular filaments as potential inhalable drug carriers within aerosols via jet nebulization. We found that the peptide design and supramolecular stability play a crucial role in the interfacial stability and aerosolization properties of the supramolecular filaments. Monomeric units with a positively charged C-terminus produced filaments with reduced aerosol stability, promoting morphological changes after nebulization. Conversely, having a neutral or negatively charged terminus yielded filaments with enhanced stability, where supramolecular integrity is maintained with only reduced length. Our results suggest that molecular enrichment at the air-liquid interface during nebulization is the primary factor to deplete the monomeric peptide amphiphiles in solution, accounting for the observed morphological disruption/transitions. Importantly, encapsulation of drugs and dyes within filaments notably stabilize their supramolecular structure during nebulization, and the loaded filaments exhibit a linear release profile from a nebulizer device. We envision the use of this supramolecular carrier system as an effective platform for the inhalation-based treatment of many lung diseases.

Peptide-/Drug-Directed Self-Assembly of Hybrid Polyurethane Hydrogels for Wound Healing

Drug-loading hydrogels are promising candidates in the bioengineering research field; nevertheless, hydrophobic drug loading into a hydrophilic carrier system remains unsolved and is full of challenges. In this work, following the potential dual interactions between peptides and aromatic drugs, we developed a potent hybrid hydrogel formation method, namely, "peptide-/drug-directed self-assembly". The hybrid hydrogels were synthesized using polyethylene glycol (PEG)-based Fmoc-FF peptide hybrid polyurethane, in which curcumin could be encapsulated through self-assembly with Fmoc-FF peptide via π-π stacking. On the basis of this, curcumin loading capacity could be improved to as high as 3.3 wt % with sustained release. In addition, the curcumin loading enhanced the hydrogel mechanical properties from 4 kPa to over 10 kPa, similar to that of natural soft tissues. Furthermore, the hydrogels were injectable with self-healing properties since the Fmoc-FF peptide/curcumin coassembly was noncovalent and reversible. Spectroscopy results confirmed the existence of the coassembly of Fmoc-FF peptide/curcumin. Further in vivo experiments effectively demonstrated that the hydrogels could improve the cutaneous wound healing in a full-thickness skin defected model. This peptide-/drug-directed self-assembly of hybrid polyurethane hydrogel could be used as a promising platform for tissue-engineering scaffold and biomedical application.

Injectable peptide hydrogel as intraperitoneal triptolide depot for the treatment of orthotopic hepatocellular carcinoma

Chemotherapy is among the limited choices approved for the treatment of hepatocellular carcinoma (HCC) at intermediate and advanced stages. Preferential and prolonged drug exposure in diseased sites is required to maximize the therapeutic index of the drug. Here, we report an injectable supramolecular peptide hydrogel as an intraperitoneal depot for localized and sustained release of triptolide for the treatment of orthotopic HCC. We chose peptide amphiphile C₁₆-GNNQQNYKD-OH-based nanofibers as gelators and carriers for triptolide. Sustained triptolide release from the hydrogel was achieved over 14 days in vitro, with higher accumulation in and cytotoxicity against human HCC Bel-7402 in comparison with L-02 fetal hepatocytes. After intraperitoneal injection, the hydrogel showed prolonged retention over 13 days and preferential accumulation in the liver, realizing HCC growth inhibition by 99.7 ± 0.1% and animal median survival extension from 19 to 43 days, without causing noticeable pathological changes in the major organs. These results demonstrate that injectable peptide hydrogel can be a potential carrier for localized chemotherapy of HCC.

Fine-Tuning the Linear Release Rate of Paclitaxel-Bearing Supramolecular Filament Hydrogels through Molecular Engineering

One key design feature in the development of any local drug delivery system is the controlled release of therapeutic agents over a certain period of time. In this context, we report the characteristic feature of a supramolecular filament hydrogel system that enables a linear and sustainable drug release over the period of several months. Through covalent linkage with a short peptide sequence, we are able to convert an anticancer drug, paclitaxel (PTX), to a class of prodrug hydrogelators with varying critical gelation concentrations. These self-assembling PTX prodrugs associate into filamentous nanostructures in aqueous conditions and consequently percolate into a supramolecular filament network in the presence of appropriate counterions. The intriguing linear drug release profile is rooted in the supramolecular nature of the self-assembling filaments which maintain a constant monomer concentration at the gelation conditions. We found that molecular engineering of the prodrug design, such as varying the number of oppositely charged amino acids or through the incorporation of hydrophobic segments, allows for the fine-tuning of the PTX linear release rate. In cell studies, these PTX prodrugs can exert effective cytotoxicity against glioblastoma cell lines and also primary brain cancer cells derived from patients and show enhanced tumor penetration in a cancer spheroid model. We believe this drug-bearing hydrogel platform offers an exciting opportunity for the local treatment of human diseases.

Poisonous Caterpillar-Inspired Chitosan Nanofiber Enabling Dual Photothermal and Photodynamic Tumor Ablation

As caterpillars detect the presence of predators and secrete poison, herein, we show an innovative and highly effective cancer therapeutic system using biocompatible chitosan nanofiber (CNf) installed with a pH-responsive motif that senses tumor extracellular pH, pH_e, prior to delivering dual-modal light-activatable materials for tumor reduction. The filamentous nanostructure of CNf is dynamic during cell interaction and durable in blood circulation. Due to its amine group, CNf uptakes a large amount of photothermal gold nanoparticles (AuNPs, >25 wt %) and photodynamic chlorin e6 (Ce6, >5 wt %). As the innovative CNf approaches tumors, cationic CNf effectively discharges AuNPs connected to the pH-responsive motif via electrostatic repulsion and selectively binds to tumor cells that are generally anionic, via the electrostatic attraction accompanied by CNf. We demonstrated via these actions that the endocytosed Ce6 (on CNf) and AuNPs (free from CNf) significantly elicited tumor cell death under light irradiation. As a result, the synergistic interplay of thermogenesis and photodynamic action was observed to switch on at the pH_e, resulting in a striking reduction in tumor formation and growth rate upon light exposure.

In situ hydrogelation of forky peptides in prostate tissue for drug delivery

Herein, we have designed and synthesized a novel forky peptide D3F3 that transforms into a hydrogel through crosslinking induced by ZIs stimuli. We have employed D3F3 as a suitable drug carrier that is conjugated with DOX. Since the concentration of zinc ions necessary for triggering gelation falls into the physiological range present in prostate tissue, while other cationic ions fail to trigger at physiological concentrations, the peptide-based drug delivery system (DDS) is injectable and would achieve prostate tissue-specific self-assembly in situ. The D3F3 hydrogels exhibited an optimal gelation time, satisfactory mechanical strength (can be enhanced after incorporation of DOX) as well as excellent thixotropic properties. The DDS reserved some DOX in the prostate 24 h after the injection, making local sustained release possible. In addition, the peptide materials demonstrated no cytotoxicity against normal fibroblast cells and no damage was observed to the prostate tissue of rats. The drug release followed a non-Fickian diffusion model, with no burst release observed. Importantly, the DOX-hydrogel system exhibited good anti-cancer efficacy when incubated with prostate cancer cells DU-145. Therefore, this study lays the groundwork for the future design of tissue-specific DDSs that are triggered by cationic ions (e.g. zinc ions), and the platform could be further developed to incorporate other potent drugs utilized in the field of prostate cancer therapy, thereby increasing their potency and reducing their side effects.

Peptide-modulated self-assembly as a versatile strategy for tumor supramolecular nanotheranostics

Advances in supramolecular self-assembly have promoted the development of theranostics, the combination of both therapeutic and diagnostic functions in a single nanoplatform, which is closely associated with antitumor applications and has shown promising potential in personalized medicine. Peptide-modulated self-assembly serves as a versatile strategy for tumor supramolecular nanotheranostics possessing controllability, programmability, functionality and biosafety, thus promoting the translation of nanotheranostics from bench to bedside. In this review, we will focus on the self-assembly of peptide-photosensitizers and peptide-drugs as well as multicomponent cooperative self-assembly for the fabrication of nanotheranostics that integrate diagnosis and therapeutics for antitumor applications. Emphasis will be placed on building block design, interaction strategies and the potential relationships between their structures and properties, aiming to increase understanding of the critical role of peptide-modulated self-assembly in advancing antitumor supramolecular nanotheranostics.

Advances in intracellular delivery through supramolecular self-assembly of oligonucleotides and peptides

Cells utilize natural supramolecular assemblies to maintain homeostasis and biological functions. Naturally inspired modular assembly of biomaterials are now being exploited for understanding or manipulating cell biology for treatment, diagnosis, and detection of diseases. Supramolecular biomaterials, in particular peptides and oligonucleotides, can be precisely tuned to have diverse structural, mechanical, physicochemical and biological properties. These merits of oligonucleotides and peptides as building blocks have given rise to the evolution of numerous nucleic acid- and peptide-based self-assembling nanomaterials for various medical applications, including drug delivery, tissue engineering, regenerative medicine, and immunotherapy. In this review, we provide an extensive overview of the intracellular delivery approaches using supramolecular self-assembly of DNA, RNA, and peptides. Furthermore, we discuss the current challenges related to subcellular delivery and provide future perspectives of the application of supramolecular biomaterials for intracellular delivery in theranostics.

Enzyme-Triggered Morphological Transition of Peptide Nanostructures for Tumor-Targeted Drug Delivery and Enhanced Cancer Therapy

The use of smart drug carriers to realize cancer-targeted drug delivery is a promising method to improve the efficiency of chemotherapy and reduce its side effects. A surfactant-like peptide, Nap-FFGPLGLARKRK, was elaborately designed for cancer-targeted drug delivery based on an enzyme-triggered morphological transition of the self-assembled nanostructures. The peptide has three functional motifs: the aromatic motif of Nap-FF- to promote peptide self-assembly, the enzyme-cleavable segment of -GPLGLA- to introduce enzyme sensitivity, and the positively charged -RKRK- segment to balance the molecular amphiphilicity as well as to facilitate interaction with cell membranes. The peptide self-assembles into long fibrils with hydrophobic inner cores, which can encapsulate a high amount of anticancer drug doxorubicin (DOX). By having enzyme responsibility, these fibrils can be degraded into thinner ones by the cancer-overexpressed matrix metalloproteinase-7 (MMP7) at tumor sites and precipitate out to give sustained release of DOX, resulting in cancer-targeted drug delivery and selective cancer killing. In vivo antitumor experiments with mice confirm the high efficiency of such enzyme-responsive peptidic drug carriers in successfully suppressing the tumor growth and metastasis while greatly reducing the side effects. The study demonstrates the feasibility of using enzyme-sensitive peptide nanostructures for efficient and targeted drug delivery, which have great potential in biomedical cancer treatment.

Syndiotactic peptides for targeted delivery

Lack of cell-type specificity and proteolytic susceptibility have long been the major bottlenecks for the development of peptide-based biomaterials for targeted drug delivery. Though a poly-l backbone provides the adaptability to re-conform the peptide structure to bind to a receptor, it also makes the peptide more susceptible to proteolytic cleavage. We have attempted to address this issue by designing a set of syndiotactic peptides de novo, with alternating l- and d-amino acids in succession. The designed peptides have higher rates of cellular uptake than the Tat (48-60) peptide in breast and cervical cancer cells. The uptake is independent of concentration, temperature and endocytosis (clathrin mediated). Importantly, the peptides are stable in both human plasma and bovine serum. The peptide-drug conjugates are much less toxic to the non-cancerous cells than cancer cells. The designed peptides are a step forward towards the development of targeted drug delivery vectors on peptide templates. STATEMENT OF SIGNIFICANCE: Present options in chemotherapy have multiple side effects arising from the lack of cell-type specificity, which makes them synonymous with "a Pyrrhic victory". Proteolytic susceptibility and non-specificity towards cancer cells has stunted the development of peptide-based biomaterials for targeted drug delivery. We have designed a set of peptides, addressing the above-mentioned roadblocks at an in vitro level. The peptides were designed on the template of a naturally existing peptide antibiotic from Bacillus brevis. The designed peptides have higher rates of cellular transduction than the model peptide (Tat), and is majorly membrane based. The peptides are stable in serum and selective towards cancer cells. Observations presented in this work can potentially take the discipline of de novo design of biomaterial conjugates forward.

A sequentially responsive and structure-transformable nanoparticle with a comprehensively improved 'CAPIR cascade' for enhanced antitumor effect

An intravenously administered drug delivery system should undergo a five-step 'CAPIR' cascade (circulation, accumulation, penetration, internalization and release), and the maximal efficiency of each step is of great importance to obtain the improved final therapeutic benefits and overall survival rate. Here, a pH/matrix metalloproteinase-9 (MMP9) sequentially responsive and continuously structure-transformable nanoparticle assembled from a doxorubicin (DOX)-conjugated peptide was exploited for comprehensively improving the 'CAPIR cascade' and eventually enhancing the therapeutic efficacy. The chimeric peptide can self-assemble into spherical nanoparticles (RGD-sNPs) at pH 7.4 with a particle size of 45.7 ± 5.4 nm. By a combination of passive and active targeting mechanisms, RGD-sNPs achieved efficient accumulation at the tumor site (∼15.1% ID g-1 within 24 h). Both in vitro and in vivo experiments revealed that RGD-sNPs can be transformed into rod-like nanoparticles (S-NFs) triggered by MMP9 that overexpressed in the tumor microenvironment, demonstrating remarkable advantages of deep tumor penetration, prolonged drug retention with ∼3.7% ID g-1 at 96 h, and 2-fold enhanced internalization. Subsequently, S-NFs would respond to the intracellular weakly acidic stimuli to rapidly release DOX for induction of cytotoxicity and apoptosis. Meanwhile, the remaining peptide was further converted into long fibers (length >5 μm) with significant cytotoxicity, thereby exerting a synergistic antitumor effect. Thus RGD-sNPs displayed superior antitumor efficacy and extended the median survival period to 55 days. This provides a new horizon for the exploration of high-performance antitumor nanomedicines.

Doxorubicin-reinforced supramolecular hydrogels of RGD-derived peptide conjugates for pH-responsive drug delivery

Doxorubicin reinforced the self-assembly of RGD-derived peptide conjugates responsive to mild acidity.

Structure and luminescence properties of supramolecular polymers of amphiphilic aromatic thioether–peptide conjugates in water

We present the preparation of luminophore–peptide conjugates that self-assemble into phosphorescent supramolecular polymers in neutral buffer.

Self-Healing Supramolecular Hydrogels for Tissue Engineering Applications

Self-healing supramolecular hydrogels have emerged as a novel class of biomaterials that combine hydrogels with supramolecular chemistry to develop highly functional biomaterials with advantages including native tissue mimicry, biocompatibility, and injectability. These properties are endowed by the reversibly cross-linked polymer network of the hydrogel. These hydrogels have great potential for realizing yet to be clinically translated tissue engineering therapies. This review presents methods of self-healing supramolecular hydrogel formation and their uses in tissue engineering as well as future perspectives.

Mesoporous NiS2 nanospheres as a hydrophobic anticancer drug delivery vehicle for synergistic photothermal–chemotherapy

Monodispersed mesoporous NiS₂ nanospheres (mNiS₂ NSs) have been successfully developed here through a facile solvothermal method to act as a hydrophobic drug delivery vehicle for synergistic photothermal–chemo treatment of cancer.

Self-Repair of Structure and Bioactivity in a Supramolecular Nanostructure

Supramolecular nanostructures formed through self-assembly can have energy landscapes, which determine their structures and functions depending on the pathways selected for their synthesis and processing and on the conditions they are exposed to after their initial formation. We report here on the structural damage that occurs in supramolecular peptide amphiphile nanostructures, during freezing in aqueous media, and the self-repair pathways that restore their functions. We found that freezing converts long supramolecular nanofibers into shorter ones, compromising their ability to support cell adhesion, but a single heating and cooling cycle reverses the damage and rescues their bioactivity. Thermal energy in this cycle enables noncovalent interactions to reconfigure the nanostructures into the thermodynamically preferred long nanofibers, a repair process that is impeded by kinetic traps. In addition, we found that nanofibers disrupted during freeze-drying also exhibit the ability to undergo thermal self-repair and recovery of their bioactivity, despite the extra disruption caused by the dehydration step. Following both freezing and freeze-drying, which shorten the 1D nanostructures, their self-repair capacity through thermally driven elongation is inhibited by kinetically trapped states, which contain highly stable noncovalent interactions that are difficult to rearrange. These states decrease the extent of thermal nanostructure repair, an observation we hypothesize applies to supramolecular systems in general and is mechanistically linked to suppressed molecular exchange dynamics.

Integration of Cell-Penetrating Peptides with Rod-like Bionanoparticles: Virus-Inspired Gene-Silencing Technology

Inspired by the high gene transfer efficiency of viral vectors and to avoid side effects, we present here a 1D rod-like gene-silencing vector based on a plant virus. By decorating the transacting activator of transduction (TAT) peptide on the exterior surface, the TAT-modified tobacco mosaic virus (TMV) achieves a tunable isoelectric point (from ∼3.5 to ∼9.6) depending on the TAT dose. In addition to enhanced cell internalization, this plant virus-based vector (TMV-TAT) acquired endo/lysosomal escape capacity without inducing lysosomal damage, resulting in both high efficiency and low cytotoxicity. By loading silencer green fluorescent protein (GFP) siRNA onto the TMV-TAT vector (siRNA@TMV-TAT) and interfering with GFP-expressing mouse epidermal stem cells (ESCs/GFP) in vitro, the proportion of GFP-positive cells could be knocked down to levels even lower than 15% at a concentration of ∼100% cell viability. Moreover, by interfering with GFP-expressing highly metastatic hepatocellular carcinoma (MHCC97-H/GFP) tumors in vivo, treatment with siRNA@TMV-TAT complexes for 10 days achieved a GFP-negative rate as high as 80.8%. This work combines the high efficiency of viral vectors and the safety of nonviral vectors and may provide a promising strategy for gene-silencing technology.

Supramolecular self assembly of nanodrill-like structures for intracellular delivery

Despite recent advances in the supramolecular assembly of cell-penetrating peptide (CPP) nanostructures, the tuning of size, shape, morphology and packaging of drugs in these materials still remain unexplored. Herein, through sequential ligation of peptide building blocks, we create cell-penetrating self-assembling peptide nanomaterials (CSPNs) with the capability to translocate inside cells. We devised a triblock array of Tat48-59 [HIV-1 derived transactivator of transcription48-59] based CPPs, conjugated to up to four Phenylalanine (Phe) residues through an amphiphilic linker, (RADA)2. We observed that the sequential addition of Phe leads to the transition of CSPN secondary structures from a random coil, to a distorted α-helix, a β-sheet, or a pure α-helix. This transition occurs due to formation of a heptad by virtue of even number of Phe. Atomic force microscopy revealed that CSPNs form distinct shapes reminiscent of a "drill-bit". CSPNs containing two, three or four Phe, self-assemble into "nanodrill-like structures" with a coarse-twisted, non-twisted or fine-twisted morphology, respectively. These nanodrills had a high capacity to encapsulate hydrophobic guest molecules. In particular, the coarse-twisted nanodrills demonstrate higher internalization and are able to deliver rapamycin, a hydrophobic small molecule that induced autophagy and are capable of in vivo delivery. Molecular dynamics studies provide microscopic insights into the structure of the nanodrills that can contribute to its morphology and ability to interact with cellular membrane. CSPNs represent a new modular drug delivery platform that can be programmed into exquisite structures through sequence-specific fine tuning of amino acids.

Sequentially Responsive Therapeutic Peptide Assembling Nanoparticles for Dual-Targeted Cancer Immunotherapy

Combination therapeutic regimen is becoming a primary direction for current cancer immunotherapy to broad the antitumor response. Functional nanomaterials offer great potential for steady codelivery of various drugs, especially small molecules, therapeutic peptides, and nucleic acids, thereby realizing controllable drug release, increase of drug bioavailability, and reduction of adverse effects. Herein, a therapeutic peptide assembling nanoparticle that can sequentially respond to dual stimuli in the tumor extracellular matrix was designed for tumor-targeted delivery and on-demand release of a short d-peptide antagonist of programmed cell death-ligand 1 (^DPPA-1) and an inhibitor of idoleamine 2,3-dioxygenase (NLG919). By concurrent blockade of immune checkpoints and tryptophan metabolism, the nanoformulation increased the level of tumor-infiltrated cytotoxic T cells and in turn effectively inhibited melanoma growth. To achieve this, an amphiphilic peptide, consisting of a functional 3-diethylaminopropyl isothiocyanate (DEAP) molecule, a peptide substrate of matrix metalloproteinase-2 (MMP-2), and ^DPPA-1, was synthesized and coassembled with NLG919. The nanostructure swelled when it encountered the weakly acidic tumor niche where DEAP molecules were protonated, and further collapsed due to the cleavage of the peptide substrate by MMP-2 that is highly expressed in tumor stroma. The localized release of ^DPPA-1 and NLG919 created an environment which favored the survival and activation of cytotoxic T lymphocytes, leading to the slowdown of melanoma growth and increase of overall survival. Together, this study offers new opportunities for dual-targeted cancer immunotherapy through functional peptide assembling nanoparticles with design features that are sequentially responsive to the multiple hallmarks of the tumor microenvironment.

Preclinical development of drug delivery systems for paclitaxel-based cancer chemotherapy

Paclitaxel (PTX) is one of the most successful drugs ever used in cancer chemotherapy, acting against a variety of cancer types. Formulating PTX with Cremophor EL and ethanol (Taxol®) realized its clinical potential, but the formulation falls short of expectations due to side effects such as peripheral neuropathy, hypotension, and hypersensitivity. Abraxane®, the albumin bound PTX, represents a superior replacement of Taxol® that mitigates the side effects associated with Cremophor EL. While Abraxane® is now considered a gold standard in chemotherapy, its 21% response rate leaves much room for further improvement. The quest for safer and more effective cancer treatments has led to the development of a plethora of innovative PTX formulations, many of which are currently undergoing clinical trials. In this context, we review recent development of PTX drug delivery systems and analyze the design principles underpinning each delivery strategy. We chose several representative examples to highlight the opportunities and challenges of polymeric systems, lipid-based formulations, as well as prodrug strategies.

Preclinical development of drug delivery systems for paclitaxel-based cancer chemotherapy

Paclitaxel (PTX) is one of the most successful drugs ever used in cancer chemotherapy, acting against a variety of cancer types. Formulating PTX with Cremophor EL and ethanol (Taxol®) realized its clinical potential, but the formulation falls short of expectations due to side effects such as peripheral neuropathy, hypotension, and hypersensitivity. Abraxane®, the albumin bound PTX, represents a superior replacement of Taxol® that mitigates the side effects associated with Cremophor EL. While Abraxane® is now considered a gold standard in chemotherapy, its 21% response rate leaves much room for further improvement. The quest for safer and more effective cancer treatments has led to the development of a plethora of innovative PTX formulations, many of which are currently undergoing clinical trials. In this context, we review recent development of PTX drug delivery systems and analyze the design principles underpinning each delivery strategy. We chose several representative examples to highlight the opportunities and challenges of polymeric systems, lipid-based formulations, as well as prodrug strategies.

Rational Design of a New Self-Codelivery System from Redox-Sensitive Camptothecin-Cytarabine Conjugate Assembly for Effectively Synergistic Anticancer Therapy

Herein, two careful selected anticancer drugs camptothecin (CPT) and cytarabine (Ara-C) with different biological action mechanisms and different water solubility are conjugated together through a glutathione (GSH) cleavable disulfide bond to construct a redox-sensitive drug-drug conjugate, which can self-assemble into nanoparticles, thus notably improving the water solubility of CPT and the cell membrane permeability of Ara-C. Compared with free drugs, the self-assembled CPT-ss-Ara nanoparticles can concentrate in tumor tissues through the enhanced permeability and retention (EPR) effect, then they can be rapidly internalized by tumor cells and degrade into free drugs for killing the tumor cells when exposed to the reductive environment (GSH) of tumor cells, thereby reducing the injury to normal cells. Meanwhile, the CPT-ss-Ara nanoparticles can effectively protect CPT and Ara-C molecules from biological inactivation before their arrival in tumor microenvironment since free CPT and Ara-C are easy to partly lose their therapy efficacy due to their structure degradation in blood circulation. The in vitro and in vivo anticancer experimental results indicate that simultaneous release of free CPT and Ara-C can realize synergistic chemotherapy effects, thus markedly improve their anticancer activity. Therefore, our designed carrier-free, redox-sensitive CPT-ss-Ara nanoparticles might have promising clinical application to combat cancers.

Co-delivery of docetaxel and silibinin using pH-sensitive micelles improves therapy of metastatic breast cancer

Breast cancer is the most vicious killer for women, and tumor metastasis is one of the leading causes of breast cancer therapy failure. In this study, a new pH-sensitive polymer (polyethylene glycol-block-poly[(1,4-butanediol)-diacrylate-β-N,N-diisopropylethylenediamine], BDP) was synthesized. Based on BDP, docetaxel/silibinin co-delivery micelles (DSMs) was constructed. DSM had a well-defined spherical shape under the transmission electron microscope with average hydrodynamic diameter of 85.3±0.4 nm, and were stable in the bloodstream but could dissociate to release the chemotherapeutic agents in the low pH environment of the endo/lysosomes in the tumor cells. Compared with free drugs, DSM displayed greatly enhanced cellular uptake, higher cytotoxicity and a stronger anti-metastasis effect against mouse breast cancer cell line 4T1. In 4T1 tumor-bearing mice treated with DSM (twice a week for 3 weeks), the inhibition rate on tumor growth and metastasis reached 71.9% and 80.1%, respectively. These results reveal that DSM might be a promising drug delivery system for metastatic breast cancer therapy.

Self-assembling prodrugs

Covalent modification of therapeutic compounds is a clinically proven strategy to devise prodrugs with enhanced treatment efficacies. This prodrug strategy relies on the modified drugs that possess advantageous pharmacokinetic properties and administration routes over their parent drug. Self-assembling prodrugs represent an emerging class of therapeutic agents capable of spontaneously associating into well-defined supramolecular nanostructures in aqueous solutions. The self-assembly of prodrugs expands the functional space of conventional prodrug design, affording a possible pathway to more effective therapies as the assembled nanostructure possesses distinct physicochemical properties and interaction potentials that can be tailored to specific administration routes and disease treatment. In this review, we will discuss the various types of self-assembling prodrugs in development, providing an overview of the methods used to control their structure and function and, ultimately, our perspective on their current and future potential.

Terminating DNA Tile Assembly with Nanostructured Caps

Precise control over the nucleation, growth, and termination of self-assembly processes is a fundamental tool for controlling product yield and assembly dynamics. Mechanisms for altering these processes programmatically could allow the use of simple components to self-assemble complex final products or to design processes allowing for dynamic assembly or reconfiguration. Here we use DNA tile self-assembly to develop general design principles for building complexes that can bind to a growing biomolecular assembly and terminate its growth by systematically characterizing how different DNA origami nanostructures interact with the growing ends of DNA tile nanotubes. We find that nanostructures that present binding interfaces for all of the binding sites on a growing facet can bind selectively to growing ends and stop growth when these interfaces are presented on either a rigid or floppy scaffold. In contrast, nucleation of nanotubes requires the presentation of binding sites in an arrangement that matches the shape of the structure's facet. As a result, it is possible to build nanostructures that can terminate the growth of existing nanotubes but cannot nucleate a new structure. The resulting design principles for constructing structures that direct nucleation and termination of the growth of one-dimensional nanostructures can also serve as a starting point for programmatically directing two- and three-dimensional crystallization processes using nanostructure design.

A Supramolecular Vaccine Platform Based on α-Helical Peptide Nanofibers

A supramolecular peptide vaccine system was designed in which epitope-bearing peptides self-assemble into elongated nanofibers composed almost entirely of alpha-helical structure. The nanofibers were readily internalized by antigen presenting cells and produced robust antibody, CD4+ T-cell, and CD8+ T-cell responses without supplemental adjuvants in mice. Epitopes studied included a cancer B-cell epitope from the epidermal growth factor receptor class III variant (EGFRvIII), the universal CD4+ T-cell epitope PADRE, and the model CD8+ T-cell epitope SIINFEKL, each of which could be incorporated into supramolecular multi-epitope nanofibers in a modular fashion.

Enzymatic activation of cell-penetrating peptides in self-assembled nanostructures triggers fibre-to-micelle morphological transition

We report here a proof-of-concept design of a multi-domain cell-penetrating peptide amphiphile (CPPA) which can self-assemble into fibrous nanostructures and transform into spherical micelles upon enzymatic degradation by matrix metalloproteinase-2 (MMP-2) up-regulated in the tumour environment. Concomitant with this morphological transition, the cell-penetrating peptide (CPP), which was previously buried inside the CPPA fibers, could be presented on the surface of the CPPA micelles, enhancing their cell-penetrating ability. These multifunctional and enzyme-responsive CPP nanostructures hold potential as nanocarriers for tumour-targeted intracellular delivery of therapeutic and diagnostic agents.

Drug-Bearing Supramolecular Filament Hydrogels as Anti-Inflammatory Agents

We report here on the covalent conversion of the anti-inflammatory agent ketoprofen into self-assembling prodrugs that enable the effective purification of ketoprofen enantiomers, the improved selectivity and potency of ketoprofen, as well as the formation of one-component drug-bearing supramolecular hydrogels. We found that the ketoprofen hydrogelator could exhibit much-enhanced selectivity for cyclooxygenase 2 (COX-2) over COX-1, reduce the concentration of inflammatory cytokines (IL-1 and TNFα), and induce apoptosis in fibroblast-like synoviocytes while maintaining biocompatibility with healthy chondrocytes. In addition, these anti-inflammatory agent-containing hydrogels demonstrated the ability to retain the therapeutic within a joint cavity after intra-articular injection, exhibiting a slow, steady release into the plasma. We believe that upon further optimization these drug-based injectable supramolecular hydrogels could provide the basis for a local treatment strategy for rheumatoid arthritis and similar conditions.

Gemcitabine Integrated Nano-Prodrug Carrier System

Peptide nanomaterials have received a great deal of interest in drug-delivery applications due to their biodegradability, biocompatibility, suitability for large-scale synthesis, high drug-loading capacities, targeting ability, and ordered structural organization. The covalent conjugation of drugs to peptide backbones results in prolonged circulation time and improved stability of drugs. Therapeutic efficacy of gemcitabine, which is used for breast cancer treatment, is severely compromised due to its rapid plasma degradation. Its hydrophilic nature poses a challenge for both its efficient encapsulation into nanocarrier systems and its sustained release property. Here, we designed a new peptide prodrug molecule for the anticancer drug gemcitabine, which was covalently conjugated to the C-terminal of 9-fluorenylmethoxy carbonyl (Fmoc)-protected glycine. The prodrug was further integrated into peptide nanocarrier system through noncovalent interactions. A pair of oppositely charged amyloid-inspired peptides (Fmoc-AIPs) were exploited as components of the drug-carrier system and self-assembled into one-dimensional nanofibers at physiological conditions. The gemcitabine integrated nanoprodrug carrier system exhibited slow release and reduced the cellular viability of 4T1 breast cancer cell line in a time- and concentration-dependent manner.

Host Materials Transformable in Tumor Microenvironment for Homing Theranostics

A pathology-adaptive nanosystem, in which nest-like hosts are built based on nanofibers that are transformed from i.v. injected nanoparticles under the acidic tumor microenvironment. The solid tumor is artificially modified by nest-like hosts readily and firmly, resulting in highly efficient accumulation and stabilization of guest theranostics. This strategy shows great potential for the theranostics delivery to tumors.

Self-Assembled Bifunctional Peptide as Effective Drug Delivery Vector with Powerful Antitumor Activity

E-cadherin/catenin complex is crucial for cancer cell migration and invasion. The histidine-alanine-valine (HAV) sequence has been shown to inhibit a variety of cadherin-based functions. In this study, by fusing HAV and the classical tumor-targeting Arg-Gly-Asp (RGD) motif and Asn-Gly-Arg (NGR) motif to the apoptosis-inducing peptide sequence-AVPIAQK, a bifunctional peptide has been constructed with enhanced tumor targeting and apoptosis effects. This peptide is further processed as a nanoscale vector to encapsulate the hydrophobic drug docetaxel (DOC). Bioimaging analysis shows that peptide nanoparticles can penetrate into xenograft tumor cells with a significantly long retention in tumors and high tumor targeting specificity. In vivo, DOC/peptide NPs are substantially more effective at inhibiting tumor growth and prolonging survival compared with DOC control. Together, the findings of this study suggest that DOC/peptide NPs may have promising applications in pulmonary carcinoma therapy.

Aloe Vera for Tissue Engineering Applications

Aloe vera, also referred as Aloe barbadensis Miller, is a succulent plant widely used for biomedical, pharmaceutical and cosmetic applications. Aloe vera has been used for thousands of years. However, recent significant advances have been made in the development of aloe vera for tissue engineering applications. Aloe vera has received considerable attention in tissue engineering due to its biodegradability, biocompatibility, and low toxicity properties. Aloe vera has been reported to have many biologically active components. The bioactive components of aloe vera have effective antibacterial, anti-inflammatory, antioxidant, and immune-modulatory effects that promote both tissue regeneration and growth. The aloe vera plant, its bioactive components, extraction and processing, and tissue engineering prospects are reviewed in this article. The use of aloe vera as tissue engineering scaffolds, gels, and films is discussed, with a special focus on electrospun nanofibers.

Peptide hormones and lipopeptides: from self-assembly to therapeutic applications

This review describes the properties and activities of lipopeptides and peptide hormones and how the lipidation of peptide hormones could potentially produce therapeutic agents combating some of the most prevalent diseases and conditions. The self-assembly of these types of molecules is outlined, and how this can impact on bioactivity. Peptide hormones specific to the uptake of food and produced in the gastrointestinal tract are discussed in detail. The advantages of lipidated peptide hormones over natural peptide hormones are summarised, in terms of stability and renal clearance, with potential application as therapeutic agents. © 2017 The Authors Journal of Peptide Science published by European Peptide Society and John Wiley & Sons Ltd.