Micelles of different morphologies--advantages of worm-like filomicelles of PEO-PCL in paclitaxel delivery

Polyester nanoparticles delivering chemotherapeutics: Learning from the past and looking to the future to enhance their clinical impact in tumor therapy

Polymeric nanoparticles (NPs), specifically those comprised of biodegradable and biocompatible polyesters, have been heralded as a game-changing drug delivery platform. In fact, poly(α-hydroxy acids) such as polylactide (PLA), poly(lactide-co-glycolide) (PLGA), and poly(ε-caprolactone) (PCL) have been heavily researched in the past three decades as the material basis of polymeric NPs for drug delivery applications. As materials, these polymers have found success in resorbable sutures, biodegradable implants, and even monolithic, biodegradable platforms for sustained release of therapeutics (e.g., proteins and small molecules) and diagnostics. Few fields have gained more attention in drug delivery through polymeric NPs than cancer therapy. However, the clinical translational of polymeric nanomedicines for treating solid tumors has not been congruent with the fervor or funding in this particular field of research. Here, we attempt to provide a comprehensive snapshot of polyester NPs in the context of chemotherapeutic delivery. This includes a preliminary exploration of the polymeric nanomedicine in the cancer research space. We examine the various processes for producing polyester NPs, including methods for surface-functionalization, and related challenges. After a detailed overview of the multiple factors involved with the delivery of NPs to solid tumors, the crosstalk between particle design and interactions with biological systems is discussed. Finally, we report state-of-the-art approaches toward effective delivery of NPs to tumors, aiming at identifying new research areas and re-evaluating the reasons why some research avenues have underdelivered. We hope our effort will contribute to a better understanding of the gap to fill and delineate the future research work needed to bring polyester-based NPs closer to clinical application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Enhancement of cellular uptake by increasing the number of encapsulated gold nanoparticles in polymeric micelles

We apply a combination of polycaprolactone (PCL)-thiol ligand functionalization with flow-controlled microfluidic block copolymer self-assembly to produce biocompatible gold nanoparticle (GNP)-loaded micellar polymer nanoparticles (GNP-PNPs) in which GNPs are encapsulated within PCL cores surrounded by an external layer of poly(ethylene glycol) (PEG). By varying both the relative amount of block copolymer and the microfluidic flow rate, a series of GNP-PNPs are produced in which the mean number of GNPs per PNP in the < 50-nm fraction (Zave,d< 50 nm) varies between 0.1 and 1.9 while the external PEG surface is constant. Zave,d< 50 nm values are determined by statistical analysis of TEM images and compared with the results of cell uptake experiments on MDA-MB-231 cancer cells. For Zave,d< 50 nm ≤ 1 (including a control sample of individual GNPs also with a PEG surface layer), cell uptake is relatively constant, but increases sharply for Zave,d< 50 nm > 1, with a factor of 7 enhancement as Zave,d< 50 nm increases from 1 to ∼2. Enabled by the shear processing control provided by the microfluidic chip, these results provide the first evidence that cellular uptake can be enhanced specifically by increasing the number of GNPs per vector, with other parameters, including polymeric material, internal structure, and external surface chemistry, held constant. They also demonstrate a versatile platform for packaging GNPs in biocompatible polymeric carriers with flow-controlled formulation optimization for various therapeutic and diagnostic applications.

Synthesis of Thermo-Responsive Monofunctionalized Diblock Copolymer Worms

Poly(glycerol monomethacrylate)-block-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) with worm-like morphology is a typical example of reversible addition-fragmentation chain transfer (RAFT) dispersion polymerized thermo-responsive copolymer via polymerization-induced self-assembly (PISA) in aqueous solution. Chain transfer agents (CTAs) are the key component in controlling RAFT, the structures of which determine the end functional groups of the polymer chain. It is therefore of interest to monofunctionalize the polymers via CTA moiety, for bioactive functionality conjugation and in the meantime maintain the precisely controlled morphology of the copolymers and the related property. In this work, a newly designed CTA 5-(2-(tert-butoxycarbonylamino) ethylamino)-2-cyano-5-oxopentan-2-yl benzodithioate (t-Boc CPDB) was synthesized and used for the RAFT polymerization of PGMA45-PHPMA120. Subsequently, PGMA45-PHPMA120 copolymers with primary amine, maleimide, and reduced L-glutathione (a tripeptide) monofunctionalized terminals were synthesized via deprotection and conjugation reactions. These monofunctionalized copolymers maintain worm-like morphology and thermo-responsive property in aqueous solution (10% w/v), as confirmed by the transmission electron microscopy (TEM) images, and the observation of the phase transition behavior in between 4 °C and room temperature (~20 °C), respectively. Summarily, a range of thermo-responsive monofunctionalized PGMA45-PHPMA120 diblock copolymer worms were successfully synthesized, which are expected to offer potential biomedical applications, such as in polymer therapeutics, drug delivery, and diagnostics.

Rhodamine B-Conjugated Fluorescent Block Copolymer Micelles for Efficient Chlorambucil Delivery and Intracellular Imaging

The clinical development of the anticancer drug chlorambucil (CHL) is limited by its low solubility in water, poor bioavailability, and off-target toxicity. Besides, another constraint for monitoring intracellular drug delivery is the non-fluorescent nature of CHL. Nanocarriers based on block copolymers of poly(ethylene glycol)/poly(ethylene oxide) (PEG/PEO) and poly(ε-caprolactone) (PCL) are an elegant choice for drug delivery applications due to their high biocompatibility and inherent biodegradability properties. Here, we have designed and prepared block copolymer micelles (BCM) containing CHL (BCM-CHL) from a block copolymer having fluorescent probe rhodamine B (RhB) end-groups to achieve efficient drug delivery and intracellular imaging. For this purpose, the previously reported tetraphenylethylene (TPE)-containing poly(ethylene oxide)-b-poly(ε-caprolactone) [TPE-(PEO-b-PCL)₂] triblock copolymer was conjugated with RhB by a feasible and effective post-polymerization modification method. In addition, the block copolymer was obtained by a facile and efficient synthetic strategy of one-pot block copolymerization. The amphiphilicity of the resulting block copolymer TPE-(PEO-b-PCL-RhB)₂ led to the spontaneous formation of micelles (BCM) in aqueous media and successful encapsulation of the hydrophobic anticancer drug CHL (CHL-BCM). Dynamic light scattering and transmission electron microscopy analyses of BCM and CHL-BCM revealed a favorable size (10-100 nm) for passive targeting of tumor tissues via the enhanced permeability and retention effect. The fluorescence emission spectrum (λ_ex 315 nm) of BCM demonstrated Förster resonance energy transfer between TPE aggregates (donor) and RhB (acceptor). On the other hand, CHL-BCM revealed TPE monomer emission, which may be attributed to the π-π stacking interaction between TPE and CHL molecules. The in vitro drug release profile showed that CHL-BCM exhibits drug release in a sustained manner over 48 h. A cytotoxicity study proved the biocompatibility of BCM, while CHL-BCM revealed significant toxicity to cervical (HeLa) cancer cells. The inherent fluorescence of RhB in the block copolymer offered an opportunity to directly monitor the cellular uptake of the micelles by confocal laser scanning microscopy imaging. These results demonstrate the potential of these block copolymers as drug nanocarriers and as bioimaging probes for theranostic applications.

Unimolecular Micelles from Randomly Grafted Arborescent Copolymers with Different Core Branching Densities: Encapsulation of Doxorubicin and In Vitro Release Study

A series of amphiphilic arborescent copolymers of generations G1 and G2 with an arborescent poly(γ-benzyl L-glutamate) (PBG) core and poly(ethylene oxide) (PEO) chain segments in the shell, PBG-g-PEO, were synthesized and evaluated as drug delivery nanocarriers. The PBG building blocks were generated by ring-opening polymerization of γ-benzyl L-glutamic acid N-carboxyanhydride (Glu-NCA) initiated with n-hexylamine. Partial or full deprotection of the benzyl ester groups followed by coupling with PBG chains yielded a comb-branched (arborescent polymer generation zero or G0) PBG structure. Additional cycles of deprotection and grafting provided G1 and G2 arborescent polypeptides. Side chains of poly(ethylene oxide) were then randomly grafted onto the arborescent PBG substrates to produce amphiphilic arborescent copolymers. Control over the branching density of G0PBG was investigated by varying the length and the deprotection level of the linear PBG substrates used in their synthesis. Three G0PBG cores with different branching densities, varying from a compact and dense to a loose and more porous structure, were thus synthesized. These amphiphilic copolymers behaved similar to unimolecular micelles in aqueous solutions, with a unimodal number- and volume-weighted size distributions in dynamic light scattering measurements. It was demonstrated that these biocompatible copolymers can encapsulate hydrophobic drugs such as doxorubicin (DOX) within their hydrophobic core with drug loading efficiencies of 42-65%. Sustained and pH-responsive DOX release was observed from the unimolecular micelles, which suggests that they could be useful as drug nanocarriers for cancer therapy.

Nanomaterials: an intra-periodontal pocket drug-delivery system for periodontitis

Periodontitis is a microbiological condition that affects the tissues supporting the teeth. The fundamental to effective periodontal therapy is choosing the suitable antimicrobial and anti-inflammatory agent, together with the proper route of drug administration and delivery system. Intra-periodontal pocket approach with nano drug-delivery systems (NDDS) such as polymeric nanoparticles, gold nanoparticles, silica nanoparticles, magnetic nanoparticles, liposomes, polymersomes, exosomes, nano micelles, niosome, solid lipid nanoparticles, nano lipid carriers, nanocomposites, nanogels, nanofibers, scaffolds, dendrimers, quantum dots, etc., will be appropriate route of drug administration and delivery system. This NDDS delivers the drugs at the site of infection to inhibit growth and promote tissue regeneration. The present review focused on providing comprehensive information on the NDDS for periodontitis, which enhanced therapeutic outcomes via intra-periodontal pocket delivery.

Non-spherical Polymeric Nanocarriers for Therapeutics: The Effect of Shape on Biological Systems and Drug Delivery Properties

This review aims to highlight the importance of particle shape in the design of polymeric nanocarriers for drug delivery systems, along with their size, surface chemistry, density, and rigidity. Current manufacturing methods used to obtain non-spherical polymeric nanocarriers such as filomicelles or nanoworms, nanorods and nanodisks, are firstly described. Then, their interactions with biological barriers are presented, including how shape affects nanoparticle clearance, their biodistribution and targeting. Finally, their drug delivery properties and their therapeutic efficacy, both in vitro and in vivo, are discussed and compared with the characteristics of their spherical counterparts.

Plug-and-Display Photo-Switchable Systems on Plant Virus Nanoparticles

Light can be used to regulate protein interactions with a high degree of spatial and temporal precision. Photo-switchable systems therefore allow the development of controllable protein complexes that can influence various cellular and molecular processes. Here, we describe a plant virus-based nanoparticle shuttle for the distribution of proteins that can be released when exposed to light. Potato virus X (PVX) is often used as a presentation system for heterologous proteins and epitopes, and has ideal properties for biomedical applications such as good tissue penetration and the ability to form hydrogels that present signaling molecules and promote cell adhesion. In this study, we describe three different systems attached to the surface of PVX particles: LOVTRAP, BphP1/QPAS1 and Dronpa145N. We demonstrated the functionality of all three photo-switchable protein complexes in vitro and the successful loading and unloading of PVX particles. The new systems provide the basis for promising applications in the biomedical and biomaterial sciences.

The in vivo fate of polymeric micelles

This review aims to provide a systemic analysis of the in vivo, as well as subcellular, fate of polymeric micelles (PMs), starting from the entry of PMs into the body. Few PMs are able to cross the biological barriers intact and reach the circulation. In the blood, PMs demonstrate fairly good stability mainly owing to formation of protein corona despite controversial results reported by different groups. Although the exterior hydrophilic shells render PMs "long-circulating", the biodistribution of PMs into the mononuclear phagocyte systems (MPS) is dominant as compared with non-MPS organs and tissues. Evidence emerges to support that the copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-PLA) is first broken down into pieces of PEG and PLA and then remnants to be eliminated from the body finally. At the cellular level, PMs tend to be internalized via endocytosis due to their particulate nature and disassembled and degraded within the cell. Recent findings on the effect of particle size, surface characteristics and shape are also reviewed. It is envisaged that unraveling the in vivo and subcellular fate sheds light on the performing mechanisms and gears up the clinical translation of PMs.

A bio-functional polymer that prevents retinal scarring through modulation of NRF2 signalling pathway

One common cause of vision loss after retinal detachment surgery is the formation of proliferative and contractile fibrocellular membranes. This aberrant wound healing process is mediated by epithelial-mesenchymal transition (EMT) and hyper-proliferation of retinal pigment epithelial (RPE) cells. Current treatment relies primarily on surgical removal of these membranes. Here, we demonstrate that a bio-functional polymer by itself is able to prevent retinal scarring in an experimental rabbit model of proliferative vitreoretinopathy. This is mediated primarily via clathrin-dependent internalisation of polymeric micelles, downstream suppression of canonical EMT transcription factors, reduction of RPE cell hyper-proliferation and migration. Nuclear factor erythroid 2-related factor 2 signalling pathway was identified in a genome-wide transcriptomic profiling as a key sensor and effector. This study highlights the potential of using synthetic bio-functional polymer to modulate RPE cellular behaviour and offers a potential therapy for retinal scarring prevention.

Enhanced thermodynamic, pharmacokinetic and theranostic properties of polymeric micelles via hydrophobic core-clustering of superparamagnetic iron oxide nanoparticles

Background

Superparamagnetic iron oxide nanoparticles (SPIO) have been applied for decades to design theranostic polymeric micelles for targeted cancer therapy and diagnostic MR imaging. However, the effects of SPIO on the physicochemical, and biological properties of polymeric micelles have not yet been fully elucidated. Therefore, we investigated potential effect of SPIO on the physical and biological properties of theranostic polymeric micelles using representative cancer drug (doxorubicin; Doxo) and polymer carrier (i.e., poly (ethylene glycol)-co-poly(D,L-lactide), PEG-PLA).

Methods

SPIO were synthesized from Fe(acetyl acetonate)₃ in an aryl ether. SPIO and Doxo were loaded into the polymeric micelles by a solvent-evaporation method. We observed the effect of SPIO-clustering on drug loading, micelle size, thermodynamic stability, and theranostic property of PEG-PLA polymeric micelles. In addition, cellular uptake behaviors, pharmacokinetic and biodistribution study were performed.

Results

SPIO formed hydrophobic geometric cavity in the micelle core and significantly affected the integrity of micelles in terms of micelle size, Doxo loading, critical micelle concentration (CMC) and in vitro dissociation. In vivo pharmacokinetic studies also showed the enhanced Area Under Curve (AUC) and elongated the half-life of Doxo.

Conclusions

Clustered SPIO in micelles largely affects not only MR imaging properties but also biological and physical properties of polymeric micelles.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-022-00255-9.

Pi-stacking Enhances Stability, Scalability of Formation, Control over Flexibility and Circulation Time of Polymeric Filaments

Self-assembling filomicelles (FM) are of great interest to nanomedicine due to their structural flexibility, extensive systemic circulation time, and amenability to unique "cylinder-to-sphere" morphological transitions. However, current fabrication techniques for FM self-assembly are highly variable and difficult to scale. Here, we demonstrate that tetrablock copolymers composed of poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) diblocks linked by a pi-stacking perylene bisimide (PBI) moiety permit rapid, scalable, and facile assembly of FM via the flash nanoprecipitation (FNP) method. Co-assembling the tetrablocks and PEG-b-PPS diblocks at different molar ratios resulted in mixed PBI-containing FM (mPBI-FM) with tunable length and flexibility. The flexibility of mPBI-FM can be optimized to decrease uptake by macrophages in vivo, leading to increased circulation time versus (-)PBI-FM without PBI tetrablocks after intravenous administration in mice. While PEG-b-PPS diblocks form FM within a narrow range of hydrophilic weight fractions, incorporation of pi-stacking PBI groups expanded this range to increase favorability of FM assembly. Furthermore, the aggregation-dependent fluorescence of PBI shifted during oxidation-induced "cylinder-to-sphere" transitions of mPBI-FM into micelles, resulting in a distinct emission wavelength for filamentous versus spherical nanostructures. Thus, incorporation of pi-stacking allows for rapid, scalable assembly of FM with tunable flexibility and stability for theranostic and nanomedicine applications.

Comprehensively enhanced delivery cascade by transformable beaded nanofibrils for pancreatic cancer therapy

Facing the barriers in each step of the in vivo delivery cascade, the low drug delivery efficiency remains problematic in tumor therapy. Although recently the nanofibril drug delivery systems have shown improved circulation and accumulation compared with nanoparticles, the poor deep penetration and cellular internalization hinder their application, especially for pancreatic cancer with dense stroma. To comprehensively address the hurdles in the delivery cascade, a matrix metalloproteinase 2 (MMP-2) responsive transformable beaded nanofibril, which integrates the merits of nanofibril and small-sized nanoparticles, is established. The beaded nanofibril (GD@PPF) is prepared by conjugating gemcitabine-loaded small-sized nanoparticles (GD) with fibrous PEG-PCL (PPF) via GPLGVRG, a substrate peptide of MMP-2. GD@PPF escapes the clearance of the reticuloendothelial system (RES), prolongs the circulation time, and increases the selective accumulation in the tumor as fibrous micelles. Once accumulated in the tumor, small positively-charged GD is released from the beaded nanofibrils in response to MMP-2 overexpression in the stroma of pancreatic cancer, enabling permeation in the dense tumor matrix and cellular internalization, which makes up for the shortcomings of fibrous micelles. Furthermore, the remaining fibrous PPF surround the tumor tightly to impede the efflux of drugs, leading to improved retention. GD@PPF is biocompatible and exhibits excellent antitumor effect in Pan 02 subcutaneous tumor models. Therefore, the MMP-2 responsive transformable beaded nanofibril, which enhances the delivery efficiency in multiple stage of the delivery cascade, presents a promising strategy for pancreatic cancer therapy.

Design and synthesis of an azobenzene-betaine surfactant for photo-rheological fluids

HYPOTHESIS

Morphology of surfactant self-assemblies are governed by the intermolecular interactions and packing constraints of the constituent molecules. Therefore, rational design of surfactant structure should allow targeting of the specific self-assembly modes, such as wormlike micelles (WLMs). By inclusion of an appropriate photo-responsive functionality to a surfactant molecule, light-based control of formulation properties without the need for additives can be achieved.

EXPERIMENTS

A novel azobenzene-containing surfactant was synthesised with the intention of producing photo-responsive wormlike micelles. Aggregation of the molecule in its cis and trans isomers, and its concomitant flow properties, were characterised using UV-vis spectroscopy, small-angle neutron scattering, and rheological measurements. Finally, the fluids capacity for mediating particle diffusion was assessed using dynamic light scattering.

FINDINGS

The trans isomer of the novel azo-surfactant was found to form a viscoelastic WLM network, which transitioned to inviscid ellipsoidal aggregates upon photo-switching to the cis isomer. This was accompanied by changes in zero-shear viscosity up to 16,000×. UV-vis spectroscopic and rheo-SANS analysis revealed π-π interactions of the trans azobenzene chromophore within the micelles, influencing aggregate structure and contributing to micellar rigidity. Particles dispersed in a 1 wt% surfactant solution showed a fivefold increase in apparent diffusion coefficient after UV-irradiation of the mixture.

Efavirenz Loaded Mixed Polymeric Micelles: Formulation, Optimization, and In Vitro Characterization

Efavirenz (EFZ) is a biopharmaceutics classification system (BCS) Class-II, first-line antiretroviral (ARV) drug. However, its utility through the oral route is restricted by its poor solubility. The objective of this study was to formulate EFZ-loaded binary-mixed micelles as a potential carrier for oral administration of EFZ. Rubingh's regular solution theory was used to determine the interaction behavior of the two components (Cremophor RH 40 and Phospholipon 80H) and of the mixed micelles and synergistic behavior was confirmed. The mixed miceller system was formulated using solvent evaporation method and a 3² factorial design was used for the optimization of selected independent variables. Miceller systems were further characterized in terms of morphology, particle size, zeta potential, percent entrapment efficiency, and drug loading. Fourier transform infrared and differential scanning calorimetry measurements confirmed the entrapment of EFZ in the micelles. The optimized formulation presented desirable qualities viz., nanometric size (17.27 ± 0.079), high entrapment efficiency, and good colloidal stability. The prepared optimized micelles can be potential carriers for EFZ in ARV therapies.

Small-Angle X-Ray Scattering Studies of Block Copolymer Nano-Objects: Formation of Ordered Phases in Concentrated Solution During Polymerization-Induced Self-Assembly

We report that polymerization-induced self-assembly (PISA) can be used to prepare lyotropic phases comprising diblock copolymer nano-objects in non-polar media. RAFT dispersion polymerization of benzyl methacrylate (BzMA) at 90 °C using a trithiocarbonate-capped hydrogenated polybutadiene (PhBD) steric stabilizer block in n-dodecane produces either spheres or worms that exhibit long-range order at 40 % w/w solids. NMR studies enable calculation of instantaneous copolymer compositions for each phase during the BzMA polymerization. As the PBzMA chains grow longer when targeting PhBD80 -PBzMA40 , time-resolved small-angle X-ray scattering reveals intermediate body-centered cubic (BCC) and hexagonally close-packed (HCP) sphere phases prior to formation of a final hexagonal cylinder phase (HEX). The HEX phase is lost on serial dilution and the aligned cylinders eventually form disordered flexible worms. The HEX phase undergoes an order-disorder transition on heating to 150 °C and a pure HCP phase forms on cooling to 20 °C.

Saponin surfactants used in drug delivery systems: A new application for natural medicine components

Saponins are a group of compounds widely distributed in the plant kingdom. Due to their amphiphilic characteristic structure, saponins have high surface activity and self-assembly property and can be used as natural biosurfactants. Therefore, saponin has become a potential drug delivery system (DDS) carrier and has attracted the attention of many researchers. Increasing studies have found that when drugs combining with saponins, their solubility or bioavailability are improved. This phenomenon may be due to a synergistic mechanism and provides a potentially novel concept for DDS: saponins may be also used for carrier materials. This review emphasized the molecular characteristics and mechanism of saponins as carriers and the research on the morphology of saponin carriers. Besides, the article also introduced the role and application of saponins in DDS. Although there are still some limitations with the application of saponins such as cost, applicability, and hemolysis, the development of technology and in-depth molecular mechanism research will provide saponins with greater application prospects as DDS carriers.

Design and Development of D‒α‒Tocopheryl Polyethylene Glycol Succinate‒block‒Poly(ε-Caprolactone) (TPGS-b-PCL) Nanocarriers for Solubilization and Controlled Release of Paclitaxel

The objective of this study was to synthesize and characterize a set of biodegradable block copolymers based on TPGS-block-poly(ε-caprolactone) (TPGS-b-PCL) and to assess their self-assembled structures as a nanodelivery system for paclitaxel (PAX). The conjugation of PCL to TPGS was hypothesized to increase the stability and the drug solubilization characteristics of TPGS micelles. TPGS-b-PCL copolymer with various PCL/TPGS ratios were synthesized via ring opening bulk polymerization of ε-caprolactone using TPGS, with different molecular weights of PEG (1–5 kDa), as initiators and stannous octoate as a catalyst. The synthesized copolymers were characterized using ¹H NMR, GPC, FTIR, XRD, and DSC. Assembly of block copolymers was achieved via the cosolvent evaporation method. The self-assembled structures were characterized for their size, polydispersity, and CMC using dynamic light scattering (DLS) technique. The results from the spectroscopic and thermal analyses confirmed the successful synthesis of the copolymers. Only copolymers that consisted of TPGS with PEG molecular weights ≥ 2000 Da were able to self-assemble and form nanocarriers of ≤200 nm in diameter. Moreover, TPGS₂₀₀₀-b-PCL₄₀₀₀, TPGS₃₅₀₀-b-PCL₇₀₀₀, and TPGS₅₀₀₀-b-PCL₁₅₀₀₀ micelles enhanced the aqueous solubility of PAX from 0.3 µg/mL up to 88.4 ug/mL in TPGS₅₀₀₀-b-PCL₁₅₀₀₀. Of the abovementioned micellar formulations, TPGS₅₀₀₀-b-PCL₁₅₀₀₀ showed the slowest in vitro release of PAX. Specifically, the PAX-loaded TPGS₅₀₀₀-b-PCL₁₅₀₀₀ micellar formulation showed less than 10% drug release within the first 12 h, and around 36% cumulative drug release within 72 h compared to 61% and 100% PAX release, respectively, from the commercially available formulation (Ebetaxel^®) at the same time points. Our results point to a great potential for TPGS-b-PCL micelles to efficiently solubilize and control the release of PAX.

Elongated self-assembled nanocarriers: From molecular organization to therapeutic applications

Self-assembled cylindrical aggregates made of amphiphilic molecules emerged almost 40 years ago. Due to their length up to micrometers, those particles display original physico-chemical properties such as important flexibility and, for concentrated samples, a high viscoelasticity making them suitable for a wide range of industrial applications. However, a quarter of century was needed to successfully take advantage of those improvements towards therapeutic purposes. Since then, a wide diversity of biocompatible materials such as polymers, lipids or peptides, have been developed to design self-assembling elongated drug nanocarriers, suitable for therapeutic or diagnostic applications. More recently, the investigation of the main forces driving the unidirectional growth of these nanodevices allowed a translation toward the formation of pure nanodrugs to avoid the use of unnecessary side materials and the possible toxicity concerns associated.

Core-Cross-linked Fluorescent Worm-Like Micelles for Glucose-Mediated Drug Delivery

We herein report the fabrication of core-crosslinked, fluorescent, and surface-functionalized worm-like block copolymer micelles as drug delivery vehicles. The polyether-based diblock terpolymer [allyl-poly(ethylene oxide)-block-poly(2-ethylhexyl glycidyl ether-co-furfuryl glycidyl ether)] was synthesized via anionic ring opening polymerization, and self-assembly in water as a selective solvent led to the formation of long filomicelles. Subsequent cross-linking was realized using hydrophobic bismaleimides as well as a designed fluorescent cross-linker for thermally induced Diels-Alder reactions with the furfuryl units incorporated in the hydrophobic block of the diblock terpolymer. As a fluorescent cross-linker, we synthesized and incorporated a cyanine 5-based bismaleimide in the cross-linking process, which can be used for fluorescence tracking of the particles. Furthermore, we covalently attached glucose to the allyl end groups present on the surface of the micelles to investigate active glucose-mediated transport into suitable cell lines. First studies in 2D as well as 3D cell culture models suggest a glucose-dependent uptake of the particles into cells despite their unusually large size compared to other nanoparticle systems used in drug delivery.

Recent Clinical Developments of Nanomediated Drug Delivery Systems of Taxanes for the Treatment of Cancer

Conventional taxanes are used as cornerstone of the chemotherapeutical treatment for a variety of malignancies. Nevertheless, a large proportion of patients do not benefit from their treatment while they do suffer from severe adverse events related to the solvent or to the active compound. Cremophor EL and polysorbate 80 free formulations, conjugates, oral formulations and different types of drug delivery systems are some examples of the several attempts to improve the treatment with taxanes. In this review article, we discuss recent clinical developments of nanomediated drug delivery systems of taxanes for the treatment of cancer. Targeting mechanisms of drug delivery systems and characteristics of the most commonly used taxane-containing drug delivery systems in the clinical setting will be discussed in this review.

Selected nanotechnologies and nanostructures for drug delivery, nanomedicine and cure

The development of nanoparticle-based drugs has provided many opportunities to diagnose, treat and cure challenging diseases. Through the manipulation of size, morphology, surface modification, surface characteristics, and materials used, a variety of nanostructures can be developed into smart systems, encasing therapeutic and imaging agents with stealth properties. These nanostructures can deliver drugs to specific tissues or sites and provide controlled release therapy. This targeted and sustained drug delivery decreases the drug-related toxicity and increases the patient's compliance with less frequent dosing. Nanotechnology employing nanostructures as a tool has provided advances in the diagnostic testing of diseases and cure. This technology has proven beneficial in the treatment of cancer, AIDS, and many other diseases. This review article highlights the recent advances in nanostructures and nanotechnology for drug delivery, nanomedicine and cures.

Rational design of block copolymer self-assemblies in photodynamic therapy

Photodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed.

Length effect of stimuli-responsive block copolymer prodrug filomicelles on drug delivery efficiency

Filomicelles possess some unique properties for improved in vivo drug delivery efficiency relative to commonly used spherical nanocarriers, which have attracted great interests. However, the length effect of the block copolymer prodrug-based filomicelles with a comparable cross-section diameter on the drug delivery efficiency and antitumor efficacy still need to be systematically studied. In this report, we prepare three optimized nanoparticles with a comparable cross-section diameter of ~40 nm, including long filomicelles (LFMs) with the length of ~2.5 μm, short filomicelles (SFMs) with the length of ~180 nm, and spherical micelles (SMs) with a diameter of ~40 nm. All of them are self-assembled from the pH and oxidation dual-responsive block copolymer prodrug, PEG-b-P(CPTKMA-co-PEMA), consisting of poly(ethylene glycol) (PEG) and a copolymerized block of thioketal-linked camptothecin methacrylate (CPTKMA) and 2-(pentamethyleneimino) ethyl methacrylate (PEMA). At pH 6.5, the nanoparticles are positively charged due to the protonation of PPEMA segments. Among them, SFMs are demonstrated to be internalized into cells most efficiently at pH 6.5 due to larger interaction areas with cell membranes relative to SMs. Moreover, SFMs show prolonged blood circulation similar to SMs as well as deepest tumor penetration and best antitumor efficacy among the three nanoparticles. LFMs show worst in vivo performance because their too long structure limits the cellular uptake and tumor accumulation. Therefore, the responsive polymer prodrug filomicelles with an optimized length show great potentials to overcome the physiological barriers and improve the drug delivery efficiency.

Wormlike micelles with a unique ladder shape formed by a C22-tailed zwitterionic surfactant bearing a bulky piperazine group

Wormlike micelles (WLMs) have been successfully constructed from many different C₂₂-tailed surfactants. Here, we creatively introduced a bulky piperazine group onto a C₂₂-tailed zwitterionic surfactant, N-erucamidopropyl-N,N-piperazine-N-methyl ammonium propanesulfonate (EDPS), and investigated the micellar structure and properties of the EDPS WLMs via molecular dynamics simulation, cryo-TEM and rheological techniques. It was found that 25 mM EDPS increased the zero-shear viscosity to as high as ∼10⁶ mPa s. Furthermore, abnormal rheological behaviors, such as an inflection in the shear thinning region of steady rheology and an abrupt decrease of the shear stress at a critical shear rate, were observed, which was attributed to the unique ladder shape micellar structure. The EDPS WLMs were superior to other C₂₂-tailed surfactants in many aspects, such as a low overlapping concentration, higher viscosity, stable viscosity over the whole pH range, and great temperature and salt (NaCl, CaCl₂ and MgCl₂) tolerance.

A flexible bowl-shaped magnetic assembly for multifunctional gene delivery systems

Magnetic assemblies with special morphologies are promising for versatile biomedical applications due to their intriguing properties and performances. In this work, a polycation-functionalized bowl-shaped magnetic assembly (b-MNP-PGEA) was constructed for magnetic resonance imaging (MRI)-guided synergistic cancer therapy. Taking advantage of distinct properties of Fe₃O₄ nanoparticles, self-assembly concept, morphology control, and appropriate surface functionalization, the as-prepared magnetic assembly with special morphology was expected to work as a multifunctional carrier to realize the combination of magnetofection and photothermal therapy (PTT). The morphology effect of the magnetic assembly on cellular uptake and the subsequent gene transfection were investigated. The feasibility of the magnetic and photothermal carriers for MRI and complementary PTT/gene therapy was also studied. In addition, the excellent in vivo performance of the proposed bowl-shaped multifunctional carriers was demonstrated using a mouse breast cancer model. Interestingly, synergistic effects based on PTT-enhanced gene therapy were achieved. The facile assembly strategy for the development of special bowl-shaped magnetic carriers for synergistic PTT/gene therapy provides a new avenue for the versatile construction of efficient theranostic platforms.

Enzyme-Induced Kinetic Control of Peptide-Polymer Micelle Morphology

In this paper, experiment and simulation were combined to provide a view of the molecular rearrangements underlying the equilibrium and nonequilibrium transitions occurring in stimuli-responsive block copolymer amphiphile self-assemblies. Three block copolymer amphiphiles were prepared, each consisting of a hydrophilic peptide brush, responsive to proteolytic enzymes, and containing one of three possible hydrophobic blocks: (1) poly(ethyl acrylate), (2) poly(styrene), or (3) poly(lauryl acrylate). When assembled, they generate three spherical micelles each responsive to the addition of the bacterial protease, thermolysin. We found core-block-dependent phase transitions in response to the hydrophilic block being truncated by the stimulus. In one example, we found an unexpected, well-defined, pathway-dependent spherical micelle to vesicle phase transition induced by enzymatic stimulus.

Small, Smaller, Nano: New Applications for Potato Virus X in Nanotechnology

Nanotechnology is an expanding interdisciplinary field concerning the development and application of nanostructured materials derived from inorganic compounds or organic polymers and peptides. Among these latter materials, proteinaceous plant virus nanoparticles have emerged as a key platform for the introduction of tailored functionalities by genetic engineering and conjugation chemistry. Tobacco mosaic virus and Cowpea mosaic virus have already been developed for bioimaging, vaccination and electronics applications, but the flexible and filamentous Potato virus X (PVX) has received comparatively little attention. The filamentous structure of PVX particles allows them to carry large payloads, which are advantageous for applications such as biomedical imaging in which multi-functional scaffolds with a high aspect ratio are required. In this context, PVX achieves superior tumor homing and retention properties compared to spherical nanoparticles. Because PVX is a protein-based nanoparticle, its unique functional properties are combined with enhanced biocompatibility, making it much more suitable for biomedical applications than synthetic nanomaterials. Moreover, PVX nanoparticles have very low toxicity in vivo, and superior pharmacokinetic profiles. This review focuses on the production of PVX nanoparticles engineered using chemical and/or biological techniques, and describes current and future opportunities and challenges for the application of PVX nanoparticles in medicine, diagnostics, materials science, and biocatalysis.

Enhanced Cell Killing by Paclitaxel-Loaded Recombinant Protein Micelles Bearing Integrin-Binding and Cell-Penetrating Peptides

Peptide ligands are effective and specific vectors that can target cell surface receptors, and have shown great potential for targeting drug delivery vehicles. Often, materials used as drug delivery matrices are chemically synthesized and difficult to functionalize, which compromises their development as smart drug carriers. Here, we assemble carriers from a recombinant protein as a novel approach to overcome these limitations. We have previously shown that oleosin, a natural surfactant protein, can be engineered to self-assemble into spherical micelles, and that functionalizing oleosin with RGDS can increase cellular uptake in integrin bearing cells. Here, we investigated whether we could further enhance cellular by incorporating either a RGDS synergy peptide PHSRN or a cell-penetrating Tat peptide derived from human immunodeficiency virus (HIV). The resulting modified oleosins self-assemble into spherical micelles in aqueous environments. Spherical micelles made from oleosin can effectively encapsulate the hydrophobic chemotherapeutic drug paclitaxel (PX). After 15 hours, 350 nM PX loaded oleosin micelles equipped with both RGDS and Tat increased cell killing by twofold compared to free paclitaxel, and 1.2-fold compared to micelles made from RGD-oleosin alone. Micelles equipped with PHSRN alone does not facilitate cell killing compared to free paclitaxel, whereas micelles equipped with both PHSRN and RGDS increased cell killing by 1.1 fold compared to micelles with RGDS alone in 15 hours. Therefore, incorporating multiple motifs into oleosin is an approach for candidate for making a versatile drug delivery carrier.

Core-crosslinked worm-like micelles from polyether-based diblock terpolymers

We herein report on the synthesis of polyether-based diblock terpolymers and their self-assembly into complex solution structures (e.g. filomicelles). The aggregates were core-crosslinked and their structure was influenced via ultrasonication.

A simple and versatile route to amphiphilic polymethacrylates: catalytic chain transfer polymerisation (CCTP) coupled with post-polymerisation modifications

Amphiphilic polymers have become key figures in the fields of pharmacology, medicine, agriculture and cosmetics.

Basic principles of drug delivery systems - the case of paclitaxel

Cancer is the second cause of death worldwide, exceeded only by cardiovascular diseases. The prevalent treatment currently used against metastatic cancer is chemotherapy. Among the most studied drugs that inhibit neoplastic cells from acquiring unlimited replicative ability (a hallmark of cancer) are the taxanes. They operate via a unique molecular mechanism affecting mitosis. In this review, we show this mechanism for one of them, paclitaxel, and for other (non-taxanes) anti-mitotic drugs. However, the use of paclitaxel is seriously limited (its bioavailability is <10%) due to several long-standing challenges: its poor water solubility (0.3 μg/mL), its being a substrate for the efflux multidrug transporter P-gp, and, in the case of oral delivery, its first-pass metabolism by certain enzymes. Adequate delivery methods are therefore required to enhance the anti-tumor activity of paclitaxel. Thus, we have also reviewed drug delivery strategies in light of the various physical, chemical, and enzymatic obstacles facing the (especially oral) delivery of drugs in general and paclitaxel in particular. Among the powerful and versatile platforms that have been developed and achieved unprecedented opportunities as drug carriers, microemulsions might have great potential for this aim. This is due to properties such as thermodynamic stability (leading to long shelf-life), increased drug solubilization, and ease of preparation and administration. In this review, we define microemulsions and nanoemulsions, analyze their pertinent properties, and review the results of several drug delivery carriers based on these systems.

Bioresorbable filomicelles for targeted delivery of betulin derivative - In vitro study

Filomicelles (worm-like micelles) possess high drug loading capacity and long circulation time in the bloodstream. A novel approach can be filomicelles with folic acid (FA) as a targeting moiety. Folate-drug delivery systems can target FA receptors (FAR) that are overexpressed in several human carcinomas, which can potentially maximize therapeutic efficacy while minimizing side effects. The aim of this study was to develop filomicelles from combination of poly(L-lactide)-Jeffamine-folic acid and poly(L-lactide)-poly(ethylene glycol) for delivery of betulin derivative. Phosphate derivative of betulin reveals high cytotoxicity against cancer cells, however its application is restricted due to poor solubility in water. Incorporation into hydrophobic core of micelles can effectively solubilize the drug. Three kinds of micelles were obtained with high drug loading capacity. Based on TEM analysis, the copolymers formed exclusively filomicelles or mixture of filomicelles and spherical micelles. All kinds of micelles provided release of betulin derivative for over 9 days and apart the very initial phase displayed similar release profile. The influence of PLA block on initial burst effect was revealed. The in vitro cytotoxicity of betulin derivative loaded micelles against FAR-positive HeLa cells was confirmed, which proves their usefulness for targeted delivery of cytostatic drug.