Self-assembling chimeric polypeptide-doxorubicin conjugate nanoparticles that abolish tumours after a single injection

Therapeutic Effect of IL-4 Receptor-Targeting Pro-Apoptotic Peptide (AP1-ELP-KLAK) in Glioblastoma Tumor Model

BACKGROUND

Thermal-responsive self-assembled elastin-like polypeptide (ELP)-based nanoparticles are an emerging platform for controlled delivery of therapeutic peptides, proteins and small molecular drugs. The antitumor effect of bioengineered chimeric polypeptide AP1-ELP-KLAK containing an interleukin-4 receptor (IL-4R) targeting peptide and pro-apoptotic peptide (KLAKLAK) was evaluated in glioblastoma (GBM) in vitro and in vivo.

METHODS AND RESULTS

Herein, the therapeutic effect of AP1-ELP-KLAK was tested in advanced, and less curable glioblastoma cells with higher expression of IL-4R. Glioblastoma cell lines stably expressing different reporter systems i.e., caspase-3 sensor (surrogate marker for cellular apoptosis) or effluc/enhanced firefly luciferase (cellular viability) were established to measure cell death non-invasively. Bioluminescence imaging (BLI) of D54/effluc and U97MG/effluc treated with AP1-ELP-KLAK exhibited higher cell death up to 2~3-fold than the control. Treatment with AP1-ELP-KLAK resulted in time-dependent increase of caspase-3 sensor BLI activity in D54/C cells and D54/C tumor-bearing mice. Intravenous injection of AP1-ELP-KLAK dramatically reduced tumor growth by inducing cellular apoptosis in D54/effluc tumor-bearing mice. Further, the immuno-histological examination of the excised tumor tissue confirmed the presence of apoptotic cells as well as caspase-3 activation.

CONCLUSION

Collectively, AP1-ELP-KLAK effectively induced cellular apoptosis of glioblastoma cells and non-invasive imaging provides a window for real-time monitoring of anti-tumor effect with the provision of improving therapeutic efficacy in a glioblastoma mice model.

Rapid discovery of self-assembling peptides with one-bead one-compound peptide library

Self-assembling peptides have shown tremendous potential in the fields of material sciences, nanoscience, and medicine. Because of the vast combinatorial space of even short peptides, identification of self-assembling sequences remains a challenge. Herein, we develop an experimental method to rapidly screen a huge array of peptide sequences for self-assembling property, using the one-bead one-compound (OBOC) combinatorial library method. In this approach, peptides on beads are N-terminally capped with nitro-1,2,3-benzoxadiazole, a hydrophobicity-sensitive fluorescence molecule. Beads displaying self-assembling peptides would fluoresce under aqueous environment. Using this approach, we identify eight pentapeptides, all of which are able to self-assemble into nanoparticles or nanofibers. Some of them are able to interact with and are taken up efficiently by HeLa cells. Intracellular distribution varied among these non-toxic peptidic nanoparticles. This simple screening strategy has enabled rapid identification of self-assembling peptides suitable for the development of nanostructures for various biomedical and material applications.

Self-assembling peptides have a range of potential applications but developing self-assembling sequences can be challenging. Here, the authors report on a one-bead one-compound combinatorial library where fluorescence is used to detect the potential for self-assembly and identified candidates are evaluated.

Genetically Encoded Elastin-Like Polypeptides for Drug Delivery

Elastin-like polypeptides (ELPs) are thermally responsive biopolymers that consist of a repeated amino acid motif derived from human tropoelastin. These peptides exhibit temperature-dependent phase behavior that can be harnessed to produce stimuli-responsive biomaterials, such as nanoparticles or injectable drug delivery depots. As ELPs are genetically encoded, the properties of ELP-based biomaterials can be controlled with a precision that is unattainable with synthetic polymers. Unique ELP architectures, such as spherical or rod-like micelles or injectable coacervates, can be designed by manipulating the ELP amino acid sequence and length. ELPs can be loaded with drugs to create controlled, intelligent drug delivery systems. ELPs are biodegradable, nonimmunogenic, and tolerant of therapeutic additives. These qualities make ELPs exquisitely well-suited to address current challenges in drug delivery and have spurred the development of ELP-based therapeutics to treat diseases-such as cancer and diabetes-and to promote wound healing. This review focuses on the use of ELPs in drug delivery systems.

Emerging self-assembling peptide nanomaterial for anti-cancer therapy

Recently it is mainly focused on anti-tumor comprehensive treatments like finding target tumor cells or activating immune cells to inhibit tumor recurrence and metastasis. At present, chemotherapy and molecular-targeted drugs can inhibit tumor cell growth to a certain extent. However, multi-drug resistance and immune escape often make it difficult for new drugs to achieve expected effects. Peptide hydrogel nanoparticles is a new type of biological material with functional peptide chains as the core and self-assembling peptide (SAP) as the framework. It has a variety of significant biological functions, including effective local inflammation suppression and non-drug-resistant cell killing. Besides, it can induce immune activation more persistently in an adjuvant independent manner when compared with simple peptides. Thus, SAP nanomaterial has great potential in regulating cell physiological functions, drug delivery and sensitization, vaccine design and immunotherapy. Not only that, it is also a potential way to focus on some specific proteins and cells through peptides, which has already been examined in previous research. A full understanding of the function and application of SAP nanoparticles can provide a simple and practical strategy for the development of anti-tumor drugs and vaccine design, which contributes to the historical transition of peptide nanohydrogels from bench to bedside and brings as much survival benefits as possible to cancer patients.

Machine learning to determine optimal conditions for controlling the size of elastin-based particles

This paper evaluates the aggregation behavior of a potential drug and gene delivery system that combines branched polyethyleneimine (PEI), a positively-charged polyelectrolyte, and elastin-like polypeptide (ELP), a recombinant polymer that exhibits lower critical solution temperature (LCST). The LCST behavior of ELP has been extensively studied, but there are no quantitative ways to control the size of aggregates formed after the phase transition. The aggregate size cannot be maintained when the temperature is lowered below the LCST, unless the system exhibits hysteresis and forms irreversible aggregates. This study shows that conjugation of ELP with PEI preserves the aggregation behavior that occurs above the LCST and achieves precise aggregate radii when the solution conditions of pH (3, 7, 10), polymer concentration (0.1, 0.15, 0.3 mg/mL), and salt concentration (none, 0.2, 1 M) are carefully controlled. K-means cluster analyses showed that salt concentration was the most critical factor controlling the hydrodynamic radius and LCST. Conjugating ELP to PEI allowed crosslinking the aggregates and achieved stable particles that maintained their size below LCST, even after removal of the harsh (high salt or pH) conditions used to create them. Taken together, the ability to control aggregate sizes and use of crosslinking to maintain stability holds excellent potential for use in biological delivery systems.

Tumor Microenvironment-Responsive Nanococktails for Synergistic Enhancement of Cancer Treatment via Cascade Reactions

A combination treatment strategy that relies on the synergetic effects of different therapeutic approaches has been considered to be an effective method for cancer therapy. Herein, a chemotherapeutic drug (doxorubicin, Dox) and a manganese ion (Mn²⁺) were co-loaded into regenerated silk fibroin-based nanoparticles (NPs), followed by the surface conjugation of phycocyanin (PC) to construct tumor microenvironment-activated nanococktails. The resultant PC-Mn@Dox-NPs showed increased drug release rates by responding to various stimulating factors (acidic pH, hydrogen peroxide (H₂O₂), and glutathione), revealing that they could efficiently release the payloads (Dox and Mn²⁺) in tumor cells. The released Dox could not only inhibit the growth of tumor cells but also generated a large amount of H₂O₂. The elevated H₂O₂ was decomposed into the highly harmful hydroxyl radicals and oxygen through an Mn²⁺-mediated Fenton-like reaction. Furthermore, the generated oxygen participated in photodynamic therapy (PDT) and produced abundant singlet oxygen. Our investigations demonstrate that these PC-Mn@Dox-NPs exhibit multiple bioresponsibilities and favorable biosafety. By integrating Dox-induced chemotherapy, Mn²⁺-mediated chemodynamic therapy, and PC-based PDT via cascade reactions, PC-Mn@Dox-NPs achieved enhanced in vitro and in vivo anticancer efficacies compared to all the mono- or dual-therapeutic approaches. These findings reveal that PC-Mn@Dox-NPs can be exploited as a promising nanococktail for cascade reaction-mediated synergistic cancer treatment.

Anticancer nanocage platforms for combined immunotherapy designed to harness immune checkpoints and deliver anticancer drugs

The interaction of programmed cell death 1 ligand 1 (PD-L1) with its receptor, programmed cell death 1 (PD-1), inhibits T cell responses. Monoclonal antibodies that block this interaction have been shown effective as immunotherapy. However, only a subset of cancers exhibits a durable response to PD-1/PD-L1 blockade. Moreover, antibody-based immune checkpoint blockade is costly and is occasionally accompanied by systemic side effects. To overcome these limitations of antibody-based immune checkpoint blockade, an immune checkpoint-blocking ferritin nanocage displaying 24 PD-L1 binding peptides (PD-L1pep1) on its surface was designed and constructed. These ferritin nanocages displaying PD-L1pep1 (PpNF) specifically bind to PD-L1 expressed on cancer cells or to purified PD-L1 with a ~30 nM binding affinity. The addition of PpNF to co-cultures of T cells and cancer cells inhibited PD-1/PD-L1 interactions and restored T cell activities. In a mouse model of syngeneic colon cancer, PpNF specifically targeted tumors and showed antitumor activity. Moreover, PpNF nanocages encapsulating the chemotherapeutic drug doxorubicin had more potent antitumor activity than a monoclonal antibody against PD-L1. These results demonstrate that ferritin nanocages displaying surface PD-L1pep1 can be efficiently applied for immunotherapy, especially when encapsulating small chemotherapeutic drugs. These nanocages may have promise as an immunotherapeutic nanomedicine against various solid tumors.

Brain penetrating peptides and peptide-drug conjugates to overcome the blood-brain barrier and target CNS diseases

Nearly one in six people worldwide suffer from disorders of the central nervous system (CNS). There is an urgent need for effective strategies to improve the success rates in CNS drug discovery and development. The lack of effective technologies for delivering drugs and genes to the brain due to the blood-brain barrier (BBB), a structural barrier that effectively blocks most neurotherapeutic agents from reaching the brain, has posed a formidable hurdle for CNS drug development. Brain-homing and brain-penetrating molecular transport vectors, such as brain permeable peptides or BBB shuttle peptides, have shown promise in overcoming the BBB and ferrying the drug molecules to the brain. The BBB shuttle peptides are discovered by phage display technology or derived from natural neurotropic proteins or certain viruses and harness the receptor-mediated transcytosis molecular machinery for crossing the BBB. Brain permeable peptide-drug conjugates (PDCs), composed of BBB shuttle peptides, linkers, and drug molecules, have emerged as a promising CNS drug delivery system by taking advantage of the endogenous transcytosis mechanism and tricking the brain into allowing these bioactive molecules to pass the BBB. Here, we examine the latest development of brain-penetrating peptide shuttles and brain-permeable PDCs as molecular vectors to deliver small molecule drug payloads across the BBB to reach brain parenchyma. Emerging knowledge of the contribution of the peptides and their specific receptors expressed on the brain endothelial cells, choice of drug payloads, the design of PDCs, brain entry mechanisms, and delivery efficiency to the brain are highlighted. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

Designing sub-20 nm self-assembled nanocarriers for small molecule delivery: Interplay among structural geometry, assembly energetics, and cargo release kinetics

Biological constraints in diseased tissues have motivated the need for small nanocarriers (10-30 nm) to achieve sufficient vascular extravasation and pervasive tumor penetration. This particle size limit is only an order of magnitude larger than small molecules, such that cargo loading is better described by co-assembly processes rather than simple encapsulation. Understanding the structural, kinetic, and energetic contributions of carrier-cargo co-assembly is thus critical to achieve molecular-level control towards predictable in vivo behavior. These interconnected set of properties were systematically examined using sub-20 nm self-assembled nanocarriers known as three-helix micelles (3HM). Both hydrophobicity and the "geometric packing parameter" dictate small molecule compatibility with 3HM's alkyl tail core. Planar obelisk-like apomorphine and doxorubicin (DOX) molecules intercalated well within the 3HM core and near the core-shell interface, forming an integral component to the co-assembly, as corroborated by small-angle X-ray and neutron-scattering structural studies. DOX promoted crystalline alkyl tail ordering, which significantly increased (+63%) the activation energy of 3HM subunit exchange. Subsequently, 3HM-DOX displayed slow-release kinetics (t_1/2 = 40 h) at physiological temperatures, with ~50× greater cargo preference for the micelle core as described by two drug partitioning coefficients (micellar core/shell K_p1 ~ 24, and shell/bulk solvent K_p2 ~ 2). The geometric and energetic insights between nanocarrier and their small molecule cargos developed here will aid in broader efforts to deconvolute the interconnected properties of carrier-drug co-assemblies. Adding this knowledge to pharmacological and immunological explorations will expand our understanding of nanomedicine behavior throughout all the physical and in vivo processes they are intended to encounter.

Theranostic supramolecular polymers formed by the self-assembly of a metal-chelating prodrug

The direct linkage of two camptothecin moieties to a metal chelator creates a self-assembling prodrug capable of associating in aqueous solution into theranostic supramolecular polymers.

Water-dispersible unadulterated α-mangostin particles for biomedical applications

α-Mangostin, the extract from pericarp of Garcinia mangostana L . or mangosteen fruit, has been applied in various biomedical products because of its minimal skin irritation, and prominent anti-inflammatory, antimicrobial and immune-modulating activities. Owing to its low water solubility, the particle formulations are necessary for the applications of α-mangostin in aqueous media. The particle formulations are usually prepared using surfactants and/or polymers, usually at a larger amount of these auxiliaries than the amount of α-mangostin itself. Here, we show the self-assembly of α-mangostin molecules into water-dispersible particles without a need of any polymers/surfactants. Investigations on chemical structure, crystallinity and thermal properties of the obtained α-mangostin particles, in comparison to the conventional α-mangostin crystalline solid, confirm no formation of the new compound during the particle formation and suggest changes in intermolecular interactions among α-mangostin molecules and significantly more hydroxyl functionality positioned at the particles' surface. The ability of the water suspension of the α-mangostin to inhibit the growth of Propionibacterium acnes, the acne-causing bacteria, is similar to that of the solution of the conventional α-mangostin in 5% dimethyl sulfoxide. Moreover, at 12.7 ppm in an aqueous environment of RAW 264.7 cell culture, α-mangostin suspension exhibits five times higher anti-inflammatory activity than the conventional α-mangostin solution, with the same acceptable cytotoxicity of less than 20% cell death.

Characteristics of Molecularly Engineered Anticancer Drug Conjugated Organic Nanomicelles for Site-Selective Cancer Cell Rupture and Growth Inhibition of Tumor Spheroids

Site-selective uptake and specific biodistribution of chemotherapeutic drugs are essential prerequisites for targeted cancer therapy. Especially, antibody and peptide conjugated drugs have been attempted as localized therapeutic agents. However, the characteristics of drug conjugated nanosystems are less explored, which are limited with their toxicity, low therapeutic efficacy, complicated synthesis, and high costs. Herein, we report a biocompatible (about 95%) molecularly engineered anticancer drug conjugated nanomicelles (∼200 nm in size) for site-selective CD44 overexpressed cancer cell rupture and tumor growth inhibition. Microscopic analysis demonstrates the distinct visualization of organic-organic interfaces (∼5 nm), which are corroborated with spectroscopic measurements confirmed the conjugation of niclosamide drug with hyaluronic acid (NIC-HA). Uniformly distributed hemocompatible (about 99%) organic nanomicelles exhibit the cellular membrane and cytoplasmic targeting with significant cellular rupture (IC₅₀ of 4 μM for MDA MB 231 cells) indicating their inherent targeting ability for cancer cells and cancer stem cells. An inclusive in vitro and in vivo analysis for targeted antitumor activity (HT1080 tumor xenograft model) of NIC-HA nanoconjugates (∼24.6% loading) exhibited promising cancer cell death and tumor growth inhibition (60%, p < 0.05) due to STAT-3 signaling pathway inhibition and induction of apoptosis in CD44-positive triple negative breast cancer cells.

Bioengineered elastin- and silk-biomaterials for drug and gene delivery

Advances in medical science have led to diverse new therapeutic modalities, as well as enhanced understanding of the progression of various disease states. These findings facilitate the design and development of more customized and exquisite drug delivery systems that aim to improve therapeutic indices of drugs to treat a variety of conditions. Synthetic polymer-based drug carriers have often been the focus of such research. However, these structures suffer from challenges with heterogeneity of the starting material, limited chemical features, complex functionalization methods, and in some cases a lack of biocompatibility. Consequently, protein-based polymers have garnered much attention in recent years due to their monodisperse features, ease of production and functionalization, and biocompatibility. Genetic engineering techniques enable the advancement of protein-based drug delivery systems with finely tuned physicochemical properties, and thus an expanded level of customization unavailable with synthetic polymers. Of these genetically engineered proteins, elastin-like proteins (ELP), silk-like proteins (SLP), and silk-elastin-like proteins (SELP) provide a unique set of alternatives for designing drug delivery systems due to their inherent chemical and physical properties and ease of engineering afforded by recombinant DNA technologies. In this review we examine the advantages of genetically engineered drug delivery systems with emphasis on ELP and SLP constructions. Methods for fabrication and relevant biomedical applications will also be discussed.

Selective Capture and Recovery of Monoclonal Antibodies by Self-Assembling Supramolecular Polymers of High Affinity for Protein Binding

The separation and purification of therapeutic proteins from their biological resources pose a great limitation for industrial manufacturing of biologics in an efficient and cost-effective manner. We report here a supramolecular polymeric system that can undergo multiple reversible processes for efficient capture, precipitation, and recovery of monoclonal antibodies (mAbs). These supramolecular polymers, namely immunofibers (IFs), are formed by coassembly of a mAb-binding peptide amphiphile with a rationally designed filler molecule of varying stoichiometric ratios. Under the optimized conditions, IFs can specifically capture mAbs with a precipitation yield greater than 99%, leading to an overall mAb recovery yield of 94%. We also demonstrated the feasibility of capturing and recovering two mAbs from clarified cell culture harvest. These results showcase the promising potential of peptide-based supramolecular polymers as reversible affinity precipitants for mAb purification.

Tumor Subtype Determines Therapeutic Response to Chimeric Polypeptide Nanoparticle-based Chemotherapy in Pten-deleted Mouse Models of Sarcoma

PURPOSE

Nanoparticle-encapsulated drug formulations can improve responses to conventional chemotherapy by increasing drug retention within the tumor and by promoting a more effective antitumor immune response than free drug. New drug delivery modalities are needed in sarcomas because they are often chemoresistant cancers, but the rarity of sarcomas and the complexity of diverse subtypes makes it challenging to investigate novel drug formulations.

EXPERIMENTAL DESIGN

New drug formulations can be tested in animal models of sarcomas where the therapeutic response of different formulations can be compared using mice with identical tumor-initiating mutations. Here, using Cre/loxP and CRISPR/Cas9 techniques, we generated two distinct mouse models of Pten-deleted soft-tissue sarcoma: malignant peripheral nerve sheath tumor (MPNST) and undifferentiated pleomorphic sarcoma (UPS). We used these models to test the efficacy of chimeric polypeptide doxorubicin (CP-Dox), a nanoscale micelle formulation, in comparison with free doxorubicin.

RESULTS

The CP-Dox formulation was superior to free doxorubicin in MPNST models. However, in UPS tumors, CP-Dox did not improve survival in comparison with free doxorubicin. While CP-Dox treatment resulted in elevated intratumoral doxorubicin concentrations in MPNSTs, this increase was absent in UPS tumors. In addition, elevation of CD8+ T cells was observed exclusively in CP-Dox-treated MPNSTs, although these cells were not required for full efficacy of the CP nanoparticle-based chemotherapy.

CONCLUSIONS

These results have important implications for treating sarcomas with nanoparticle-encapsulated chemotherapy by highlighting the tumor subtype-dependent nature of therapeutic response.

TME-Responsive Polyprodrug Micelles for Multistage Delivery of Doxorubicin with Improved Cancer Therapeutic Efficacy in Rodents

It is of great significance to develop multifunctional biomaterials to effectively deliver anticancer drug to tumor cells for cancer therapy. Here, inspired by the specific tumor microenvironment (TME) cues, a unique multistage pH/redox-responsive polyprodrug composed of amphiphilic pH-sensitive diblock copolymer poly(ethylene glycol) methyl ether-b-poly(β-amino esters) conjugated with doxorubicin (DOX) via redox-sensitive disulfide bonds (mPEG-b-PAE-ss-DOX) is designed and developed. This polyprodrug can self-assemble into micelles (DOX-ss@PMs) at low concentration with high serum stability, indicating that DOX-ss@PMs have prolonged circulation time. The dual pH/redox-responsiveness of the multistage platform is thoroughly evaluated. In vitro results demonstrate that DOX-ss@PMs can highly accumulate at tumor site, followed by responding to the acidity for disassembly and effectively penetrating into the tumor cells. DOX is released from the platform due to the cleavage of disulfide bonds induced by high glutathione (GSH) concentration, thereby inducing the apoptosis of tumor cells. In vivo studies further reveal that multistage DOX-ss@PMs can more efficiently inhibit the growth of tumors and improve the survival of tumor-bearing mice in comparison to the free drug and control. These results imply that multistage delivery system might be a potential and effective strategy for drug delivery and DOX-ss@PMs could be a promising nanomedicine for cancer chemotherapy.

Tumor microenvironment-oriented adaptive nanodrugs based on peptide self-assembly

The aberrant metabolism of tumor cells creates an inimitable microenvironment featuring acidic pH, high glutathione (GSH) levels, and overexpression of certain enzymes, which benefits the overwhelming progress of a tumor. Peptide self-assembly, emerging as a biofriendly and versatile fabrication strategy, harnesses multiple noncovalent interactions to obtain a variety of nanostructures tailored on demand. Orchestrating the reversible nature of noncovalent interactions and abnormal physiological parameters in the tumor microenvironment enables peptide-based nanodrugs to be targetable or switchable, thereby improving the drugs' bioavailability and optimizing the treatment outcome. This review will focus on peptide-modulated self-assembly of photosensitizers, chemotherapeutic drugs, immunoactive agents for tumor microenvironment-oriented adaptive phototherapy, chemotherapy, immunotherapy and combinatorial therapy. We will emphasize the building block design, the intermolecular interaction principle, adaptive structural transformation in the tumor microenvironment and corresponding therapeutic efficacy, and aim to elucidate the critical role of peptide-modulated, tumor microenvironment-oriented adaptive assemblies in improving the therapeutic index. Challenges and opportunities will be covered as well to advance the development and clinical application of tumor therapies based on peptide self-assembly materials and techniques.

Elastin-Like Polypeptides for Biomedical Applications

Elastin-like polypeptides (ELPs) are stimulus-responsive biopolymers derived from human elastin. Their unique properties—including lower critical solution temperature phase behavior and minimal immunogenicity—make them attractive materials for a variety of biomedical applications. ELPs also benefit from recombinant synthesis and genetically encoded design; these enable control over the molecular weight and precise incorporation of peptides and pharmacological agents into the sequence. Because their size and sequence are defined, ELPs benefit from exquisite control over their structure and function, qualities that cannot be matched by synthetic polymers. As such, ELPs have been engineered to assemble into unique architectures and display bioactive agents for a variety of applications. This review discusses the design and representative biomedical applications of ELPs, focusing primarily on their use in tissue engineering and drug delivery.

Transient stealth coating of liver sinusoidal wall by anchoring two-armed PEG for retargeting nanomedicines

A major critical issue in systemically administered nanomedicines is nonspecific clearance by the liver sinusoidal endothelium, causing a substantial decrease in the delivery efficiency of nanomedicines into the target tissues. Here, we addressed this issue by in situ stealth coating of liver sinusoids using linear or two-armed poly(ethylene glycol) (PEG)-conjugated oligo(l-lysine) (OligoLys). PEG-OligoLys selectively attached to liver sinusoids for PEG coating, leaving the endothelium of other tissues uncoated and, thus, accessible to the nanomedicines. Furthermore, OligoLys having a two-armed PEG configuration was ultimately cleared from sinusoidal walls to the bile, while OligoLys with linear PEG persisted in the sinusoidal walls, possibly causing prolonged disturbance of liver physiological functions. Such transient and selective stealth coating of liver sinusoids by two-arm-PEG-OligoLys was effective in preventing the sinusoidal clearance of nonviral and viral gene vectors, representatives of synthetic and nature-derived nanomedicines, respectively, thereby boosting their gene transfection efficiency in the target tissues.

Self-assembled nucleo-tripeptide hydrogels provide local and sustained doxorubicin release

Self-assembled nucleo-peptide hydrogels have a nanofibril structure composed of noncovalent molecular interactions between peptide groups as well as π-π stacking and Watson-Crick interactions via complementary nucleobases. These hydrogels have specific benefits for biomedical applications due to their DNA-like interactions in addition to the well-known advantages of peptide biomaterials: biocompatibility, extracellular matrix (ECM)-like structure, and bottom-up design. Inspired by the nucleobase stacking structure, we hypothesized that nucleo-peptides would be able to deliver the DNA-intercalating chemotherapeutic, doxorubicin (Dox) in a sustained manner when delivered locally to a solid tumor. Ade-FFF nucleo-peptide hydrogels were able to load a high concentration of Dox (1 mM) and demonstrated continuous release under in vitro degradation conditions. We adopted an in vivo tumor-bearing mouse model to evaluate the delivery of Dox by Ade-FFF hydrogels. We found that Dox-containing hydrogels reduced tumor growth and resulted in greater apoptosis-mediated cell death in the tumor as evidenced by caspase-3 expression. Pharmacokinetics and biodistribution studies also supported the observation that Dox delivery by an Ade-FFF hydrogel improves sustained delivery in the local tumor site. This study demonstrates the potential of self-assembled nucleo-peptides in biomedical applications by using their distinctive DNA-like structure.

Functional peptide-based drug delivery systems

Peptides are one of the most important functional motifs for constructing smart drug delivery systems (DDSs). Functional peptides can be conjugated with drugs or carriers via covalent bonds, or assembled into DDSs via supramolecular forces, which enables the DDSs to acquire desired functions such as targeting and/or environmental responsiveness. In this mini review, we first introduce the different types of functional peptides that are commonly used for constructing DDSs, and we highlight representative strategies for designing smart DDSs by using functional peptides in the past few years. We also state the challenges of peptide-based DDSs and come up with prospects.

Anthraquinone: a promising scaffold for the discovery and development of therapeutic agents in cancer therapy

Cancer, characterized by uncontrolled malignant neoplasm, is a leading cause of death in both advanced and emerging countries. Although, ample drugs are accessible in the market to intervene with tumor progression, none are totally effective and safe. Natural anthraquinone (AQ) equivalents such as emodin, aloe-emodin, alchemix and many synthetic analogs extend their antitumor activity on different targets including telomerase, topoisomerases, kinases, matrix metalloproteinases, DNA and different phases of cell lines. Nano drug delivery strategies are advanced tools which deliver drugs into tumor cells with minimum drug leakage to normal cells. This review delineates the way AQ derivatives are binding on these targets by abolishing tumor cells to produce anticancer activity and purview of nanoformulations related to AQ analogs.

FT-IR Spectroscopic Analysis of the Secondary Structures Present during the Desiccation Induced Aggregation of Elastin-Like Polypeptide on Silica

Previously, we found that elastin-like polypeptide (ELP), when dried above the lower critical solution temperature on top of a hydrophilic fused silica disk, exhibited a dynamic coalescence behavior. The ELP initially wet the silica, but over the next 12 h, dewett the surface and formed aggregates of precise sizes and shapes. Using Fourier-transform infrared (FT-IR) spectroscopy, the present study explores the role of secondary structures present in ELP during this progressive desiccation and their effect on aggregate size. The amide I peak (1600-1700 cm-1) in the ELP's FT-IR spectrum was deconvoluted using the second derivative method into eight subpeaks (1616, 1624, 1635, 1647, 1657, 1666, 1680, 1695 cm-1). These peaks were identified to represent extended strands, β-turns, 3(10)-helix, polyproline I, and polyproline II using previous studies on ELP and molecules similar in peptide composition. Positive correlations were established between the various subpeaks, water content, and aggregate size to understand the contributions of the secondary structures in particle formation. The positive correlations suggest that type II β-turns, independent of the water content, contributed to the growth of the aggregates at earlier time points (1-3.5 h). At later time points (6-12 h), the aggregate growth was attributed to the formation of 3(10)-helices that relied on a decrease in water content. Understanding these relationships gives greater control in creating precisely sized aggregates and surface coatings with varying roughness.

Genetically Encoded Stealth Nanoparticles of a Zwitterionic Polypeptide-Paclitaxel Conjugate Have a Wider Therapeutic Window than Abraxane in Multiple Tumor Models

Small-molecule therapeutics demonstrate suboptimal pharmacokinetics and bioavailability due to their hydrophobicity and size. One way to overcome these limitations-and improve their efficacy-is to use "stealth" macromolecular carriers that evade uptake by the reticuloendothelial system. Although unstructured polypeptides are of increasing interest as macromolecular drug carriers, current recombinant polypeptides in the clinical pipeline typically lack stealth properties. We address this challenge by developing new unstructured polypeptides, called zwitterionic polypeptides (ZIPPs), that exhibit "stealth" behavior in vivo. We show that conjugating paclitaxel to a ZIPP imparts amphiphilicity to the polypeptide chain that is sufficient to drive its self-assembly into micelles. This in turn increases the half-life of paclitaxel by 17-fold compared to free paclitaxel, and by 1.6-fold compared to the nonstealth control, i.e., ELP-paclitaxel. Treatment of mice bearing highly aggressive prostate or colon cancer with a single dose of ZIPP-paclitaxel nanoparticles leads to near-complete eradication of the tumor, and these nanoparticles have a wider therapeutic window than Abraxane, an FDA-approved taxane nanoformulation.

pH-Responsive hyperbranched polypeptides based on Schiff bases as drug carriers for reducing toxicity of chemotherapy

Polymeric micelles have great potential in drug delivery systems because of their multifunctional adjustability, excellent stability, and biocompatibility. To further increase the drug loading efficiency and controlled release ability, a pH-responsive hyperbranched copolymer methoxy poly(ethylene glycol)-b-polyethyleneimine-poly(Nε-Cbz-l-lysine) (MPEG-PEI-PBLL) was synthesized successfully. MPEG-PEI-NH2 was synthesized to initiate the ring-opening polymerization of benzyloxycarbonyl substituted lysine N-carboxyanhydride (Z-lys NCA). The introduction of Schiff bases in the polymer make it possible to respond to the variation of pH values, which cleaved at pH 5.0 while stable at pH 7.4. As the polymer was amphiphilic, MPEG-PEI-PBLL could self-assemble into micelles. Owing to the introduction of PEI, which make the copolymer hyperbranched, the pH-responsive micelles could efficiently encapsulate theranostic agents, such as doxorubicin (DOX) for chemotherapy and NIRF dye DiD for in vivo near-infrared (NIR) imaging. The drug delivery system prolonged the drug circulation time in blood and allowed the drug accumulate effectively at the tumor site. Following the guidance, the DOX was applied in chemotherapy to achieve cancer therapeutic efficiency. All the results demonstrate that the polymer micelles have great potential for cancer theranostics.

Biological Assembly of Modular Protein Building Blocks as Sensing, Delivery, and Therapeutic Agents

Nature has evolved a wide range of strategies to create self-assembled protein nanostructures with structurally defined architectures that serve a myriad of highly specialized biological functions. With the advent of biological tools for site-specific protein modifications and de novo protein design, a wide range of customized protein nanocarriers have been created using both natural and synthetic biological building blocks to mimic these native designs for targeted biomedical applications. In this review, different design frameworks and synthetic decoration strategies for achieving these functional protein nanostructures are summarized. Key attributes of these designer protein nanostructures, their unique functions, and their impact on biosensing and therapeutic applications are discussed.

Nanotoxicology of an Elastin-like Polypeptide Rapamycin Formulation for Breast Cancer

The clinical utility of rapamycin (Rapa) is limited by solubility, bioavailability, and side effects. To overcome this, our team recently reported an elastin-like polypeptide (ELP) nanoparticle with high affinity, noncovalent drug binding, and integrin-mediated cellular uptake. Given the scarcity of pharmacology/toxicology studies of ELP-based drug carriers, this article explores safety and efficacy of ELP-Rapa. ELP-Rapa nanoparticles tested negative for hemolysis, did not interfere in plasma coagulation nor in platelet function, and did not activate the complement. Upon incubation with HepG2 cells, ELP-Rapa revealed significant cellular uptake and trafficking to acidic organelles, consistent with lysosomes. Internalized ELP-Rapa nanoparticles increased oxidative stress 4-fold compared to free drug or free ELP controls. However, mice bearing orthotopic hormone receptor positive BT-474 breast tumors, given a high dose (∼10-fold above therapeutic dose) of 1 month administration of ELP-Rapa, did not induce hepatotoxicity. On the other hand, tumor growth and mTOR signaling were suppressed without affecting body weight. Nanoparticles assembled using ELP technology appear to be a safe and efficient strategy for delivering Rapa.

A self-assembled carrier-free nanosonosensitizer for photoacoustic imaging-guided synergistic chemo-sonodynamic cancer therapy

As one of the most promising noninvasive therapeutic modalities, sonodynamic therapy (SDT) can focus the ultrasound energy on tumor sites located in deep tissue and locally activate the preloaded sonosensitizer to kill tumor cells. However, exploring sonosensitizers with high SDT efficacy and desirable biosafety is still a significant challenge. Herein, we utilized the hydrophilic-hydrophobic self-assembly technology to assemble the hydrophobic organic dye Ce6 and broad spectral anti-cancer agent Paclitaxel with hydrophilic organic dye IR783 to generate a nanoscale sonosensitizer, Ce6-PTX@IR783, without the introduction of extra nanomaterials into the fabrication to guarantee high therapeutic biosafety and further potential clinical translation. The constructed nanodrug was endowed with an external ultrasound-activatable chemo-sonodynamic effect and photoacoustic imaging performance via integrating multiple moieties into one nanosystem. Ce6 could enhance the sonodynamic effect, while PTX exerted a chemotherapeutic effect, and IR783 was applied to increase tumor-specific accumulation and assist in fulfilling photoacoustic imaging. In particular, the small particle size (70 nm) of Ce6-PTX@IR783 contributed to the increased tumor accumulation via the enhanced permeability and retention effect. The high synergistically chemo-sonodynamic therapeutic efficacy has been successfully demonstrated in vitro and in vivo, in addition to the demonstrated high biodegradability, biocompatibility and biosafety. This facile self-assembly procedure provides an intriguing strategy for highly efficient utilization of hydrophobic drugs and is liable to realize large-scale production and further clinical translation.

The role of critical micellization concentration in efficacy and toxicity of supramolecular polymers

The inception and development of supramolecular chemistry have provided a vast library of supramolecular structures and materials for improved practice of medicine. In the context of therapeutic delivery, while supramolecular nanostructures offer a wide variety of morphologies as drug carriers for optimized targeting and controlled release, concerns are often raised as to how their morphological stability and structural integrity impact their in vivo performance. After intravenous (i.v.) administration, the intrinsic reversible and dynamic feature of supramolecular assemblies may lead them to dissociate upon plasma dilution to a concentration below their critical micellization concentration (CMC). As such, CMC represents an important characteristic for supramolecular biomaterials design, but its pharmaceutical role remains elusive. Here, we report the design of a series of self-assembling prodrugs (SAPDs) that spontaneously associate in aqueous solution into supramolecular polymers (SPs) with varying CMCs. Two hydrophobic camptothecin (CPT) molecules were conjugated onto oligoethylene-glycol (OEG)-decorated segments with various OEG repeat numbers (2, 4, 6, 8). Our studies show that the lower the CMC, the lower the maximum tolerated dose (MTD) in rodents. When administrated at the same dosage of 10 mg/kg (CPT equivalent), SAPD 1, the one with the lowest CMC, shows the best efficacy in tumor suppression. These observations can be explained by the circulation and dissociation of SAPD SPs and the difference in molecular and supramolecular distribution between excretion and organ uptake. We believe these findings offer important insight into the role of supramolecular stability in determining their therapeutic index and in vivo efficacy.

Engineering the Architecture of Elastin-Like Polypeptides: From Unimers to Hierarchical Self-Assembly

Well-defined tunable nanostructures formed through the hierarchical self-assembly of peptide building blocks have drawn significant attention due to their potential applications in biomedical science. Artificial protein polymers derived from elastin-like polypeptides (ELPs), which are based on the repeating sequence of tropoelastin (the water-soluble precursor to elastin), provide a promising platform for creating nanostructures due to their biocompatibility, ease of synthesis, and customizable architecture. By designing the sequence and composition of ELPs at the gene level, their physicochemical properties can be controlled to a degree that is unmatched by synthetic polymers. A variety of ELP-based nanostructures are designed, inspired by the self-assembly of elastin and other proteins in biological systems. The choice of building blocks determines not only the physical properties of the nanostructures, but also their self-assembly into architectures ranging from spherical micelles to elongated nanofibers. This review focuses on the molecular determinants of ELP and ELP-hybrid self-assembly and formation of spherical, rod-like, worm-like, fibrillar, and vesicle architectures. A brief discussion of the potential biomedical applications of these supramolecular assemblies is also included.

Unification of lower and upper critical solution temperature phase behavior of globular protein solutions in the presence of multivalent cations

In globular protein systems, upper critical solution temperature (UCST) behavior is common, but lower critical solution temperature (LCST) phase transitions are rare. In addition, the temperature sensitivity of such systems is usually difficult to tune. Here we demonstrate that the charge state of globular proteins in aqueous solutions can alter their temperature-dependent phase behavior. We show a universal way to tune the effective protein interactions and induce both UCST and LCST-type transitions in the system using trivalent salts. We provide a phase diagram identifying LCST and UCST regimes as a function of protein and salt concentrations. We further propose a model based on an entropy-driven cation binding mechanism to explain the experimental observations.

Effects of molecular weight and structural conformation of multivalent-based elastin-like polypeptides on tumor accumulation and tissue biodistribution

In order to improve clinical outcomes for novel drug delivery systems, distinct optimization of size, shape, multifunctionality, and site-specificity are of utmost importance. In this study, we designed various multivalent elastin-like polypeptide (ELP)-based tumor-targeting polymers in which multiple copies of IL-4 receptor (IL-4R)-targeting ligand (AP1 peptide) were periodically incorporated into the ELP polymer backbone to enhance the affinity and avidity towards tumor cells expressing high levels of IL-4R. Several ELPs with different molecular sizes and structures ranging from unimer to micelle-forming polymers were evaluated for their tumor accumulation as well as in vivo bio-distribution patterns. Different percentages of cell binding and uptake were detected corresponding to polymer size, number of targeting peptides, or unimer versus micelle structure. As compared to low molecular weight polypeptides, high molecular weight AP1-ELP showed superior binding activity with faster entry and efficient processing in the IL-4R-dependent endocytic pathway. In addition, in vivo studies revealed that the high molecular weight micelle-forming AP1-ELPs (A86 and A100) displayed better tumor penetration and extensive retention in tumor tissue along with reduced non-specific accumulation in vital organs, when compared to low molecular weight non-micelle forming AP1-ELPs. It is suggested that the superior binding activities shown by A86 and A100 may depend on the multiple presentation of ligands upon transition to a micelle-like structure rather than a larger molecular weight. Thus, this study has significance in elucidating the different patterns underlying unimer and micelle-forming ELP-mediated tumor targeting as well as the in vivo biodistribution.

Supramolecular Engineering of Molecular Inhibitors in an Adaptive Cytotoxic Nanoparticle for Synergistic Cancer Therapy

Combinatorial regimens that rationally pair molecular inhibitors with standard cytotoxic chemotherapeutics are used to improve therapeutic outcomes. Simultaneously engineering these therapies within a single nanocarrier that spans cytotoxic, antiangiogenic, and anti-invasive mechanisms and that enables the delivery of unique drug combinations remains a technical challenge. In this study, we developed a simple and broadly applicable strategy in which ultrastable cytotoxic nanoparticles with an established excellent antitumor efficacy and π-rich inner core structure supramolecularly stabilized the antiangiogenic molecular inhibitor apatinib to create a synergistic drug delivery system (termed sTKI-pSN38). This small-sized nanoparticle accomplished the sequential release of both encapsulated drugs to exert antimetastatic, antivascular, and cytotoxic activities simultaneously. In xenograft models of hepatocellular carcinoma, a single intravenous administration of sTKI-pSN38 elicited robust and durable tumor reduction and suppressed metastasis to lymph nodes. Interestingly, sTKI-pSN38 treatment alleviated intratumoral hypoxia, which could contribute to impaired tumor metastasis and reduced drug resistance. Collectively, this nanotherapeutic platform offers a new strategy for cancer therapy by simply engineering a drug cocktail in conventional nanoparticles and by enabling the spatiotemporal modulation of drug release to enhance the synergy of the combined drugs.

Evaluation of Strategies for Decreasing Blood Glucose Using Albuminbinding Domain

OBJECTIVE

Frequent administrations for DPPIV-resistant GLP-1 analogs are necessary to maintain the blood concentrations due to the short half-life of less than 5 minutes. However, most delivery systems that possess the ability of sustainable release of GLP-1 have drawbacks such as low yield, high cost and undesirable side effects. Therefore, we aimed to prepare a simple and efficient delivery system that could be feasibly applied to reduce blood glucose.

METHODS

A novel GLP-1 delivery system (GLP-1-ELPs-SA) was prepared and characterized by circular dichroism. Furthermore, the activity and property of GLP-1-ELPs-SA were evaluated in vitro and in vivo.

RESULTS

GLP-1-ELPs-SA are easily expressed in E. coli in a soluble formulation and purified through the inverse transition cycle. GLP-1-ELPs-SA spontaneously generated depot under physiological conditions. GLP-1-ELPs-SA was also found to be dispersed in the blood vessels from the depot and showed a high affinity to bind with mice (C57BL/6J) albumin, which shows that GLP-1-ELPs-SA has a long circulation time in vivo.

CONCLUSION

Our delivery system could markedly decrease the clearance of recombinant proteins based on serum albumin, without substantially increasing the protein molecular weight and remarkably reducing the blood glucose within 120 h.

Manipulation of the dually thermoresponsive behavior of peptide-based vesicles through modification of collagen-like peptide domains

Materials that respond to temporally defined exogenous cues continue to be an active pursuit of research toward on-demand nanoparticle drug delivery applications, and using one or more exogenous temperature stimuli could significantly expand the application of nanoparticle-based drug delivery formulations under both hyperthermal and hypothermal conditions. Previously we have reported the development of a biocompatible and thermoresponsive elastin-b-collagen-like polypeptide (ELP-CLP) conjugate that is capable of self-assembling into vesicles and encapsulating small molecule therapeutics that can be delivered at different rates via a single temperature stimulus. Herein we report the evaluation of multiple ELP-CLP conjugates, demonstrating that the inverse transition temperature (T t) of the ELP-CLPs can be manipulated by modifying the melting temperature (T m) of the CLP domain, and that the overall hydrophilicity of the ELP-CLP conjugate also may alter the T t. Based on these design parameters, we demonstrate that the ELP-CLP sequence (VPGFG)6-(GPO)7GG can self-assemble into stable vesicles at 25°C and dissociate at elevated temperatures by means of the unfolding of the CLP domain above its T m. We also demonstrate here for the first time the ability of this ELP-CLP vesicle to dissociate via a hypothermic temperature stimulus by means of exploiting the inverse transition temperature (T t) phenomena found in ELPs. The development of design rules for manipulating the thermal properties of these bioconjugates will enable future modifications to either the ELP or CLP sequences to more finely tune the transitions of the conjugates for specific biomedical applications.

Introducing Temperature-Controlled Phase Transition Elastin-like Polypeptides to Transient Electronics: Realization of Proactive Biotriggered Electronics with Local Transience

Transient electronics have dramatically changed inner-body therapy in health care. They stand out because of their harmless dissolution in the human body with no lingering electronic trash. However, high-precision biomedical implants require programmable and serial remedy operations, and controlling the whole-device destruction is not proactive and precise. Thus, a novel biotriggered and temperature-controlled transient electronics fabrication method using elastin-like polypeptides (ELPs) as triggers is proposed. Biocompatible ELPs simply mixed with trace silver nanowire (AgNW) can serve as the "switch" for the electronics to respond to local temperature changes in deionized water, exhibiting an agile response time. A ratio gradient experiment of the ELPs and AgNW shows that more programmable and precise transience properties (initial resistance, ready time, response time, and stable resistance) can be achieved by using a designated proportion. Further, we validated that the 3D-printing-based ELP-triggering transient electronics fabrication method is very simple yet effective for preparing transient wireless charging LEDs. Transient devices comprising ELPs-AgNW and PLGA-Ag respond within 160 s below 10 °C and degrade within a certain period.

Preparation and characterization of β-casein stabilized lipopeptide lyotropic liquid crystal nanoparticles for delivery of doxorubicin

A kind of lyotropic liquid crystal nanoparticle (LLC NPs) has been designed and prepared. LLC NPs are dSMO/OA/β-casein/water quaternary systems, and their cubic or hexagonal microstructures have been characterized by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS). The phase transition of LLC NPs takes place with ratio and pH adjustments. The properties, such as cytotoxicity, stability, drug encapsulation and release ability, have been investigated with MTT assay, cryo-TEM and UV-Vis spectroscopy. The results showed that LLC NPs were nontoxic to cells and stable to enzymatic degradation. Hydrophilic drug doxorubicin hydrochloride (DOX·HCl) could be effectively encapsulated in LLC NPs and its release rate could be regulated by pH. It was concluded that LLC NPs are potential nanocarriers in nanomedicine technologies. We hope that this work provides new guidelines for the rational design of LLC NP systems with lipopeptides for biomedical applications.