Nanometric Micelles with Photo‐Triggered Cytotoxicity

The development of a photo‐responsive micellar system capable of triggering cell death is reported. Precursors of the micelles are synthesized by connecting a lipophilic chain to a hydrophilic polyethylene glycol via a photo‐labile nitrobenzyl group. The resulting amphiphilic units are self‐assembled in water forming 12 nm micelles that are readily internalized into cells. Upon photo‐irradiation, micelles undergo cleavage and yield a cytotoxic nitrosobenzaldehyde derivative, which significantly inhibits the proliferation of MDA‐MB‐231 cells under standard in vitro conditions.     

Self‐Assembled Dual Dye‐Doped Nanosized Micelles for High‐Contrast Up‐Conversion Bioimaging

Sensitized triplet–triplet annihilation based photon up‐conversion (TTA‐UC) greatly improves the scope and applicability of fluorescence bioimaging by enabling anti‐Stokes detection at low powers, thus eliminating the background autofluorescence and limiting the potential damage of the living tissues. Here the authors present a facile, one‐step protocol to prepare dual dye‐doped, TTA‐UC active nanomicelles starting from the commercially available surfactant Kolliphor EL, a component of several FDA approved preparations. These nanosized micelles show an unprecedented up‐conversion yield of 6.5% under 0.1 W cm^?2 excitation intensity in an aqueous, nondeaerated dispersion. The supramolecular architecture obtained preserves the embedded dyes from oxygen quenching, allowing satisfactory anti‐Stokes fluorescence imaging of 3T3 cells. This is the first example of efficient multicomponent up‐converters prepared using highly biocompatible materials approved by the international authority, paving the way for the development of new complex and multifunctional materials for advanced theranostics.     

Enhancement of Aggregation‐Induced Emission in Dye‐Encapsulating Polymeric Micelles for Bioimaging

Three amphiphilic block copolymers are employed to form polymeric micelles and function as nanocarriers to disperse hydrophobic aggregation‐induced emission (AIE) dyes, 1,1,2,3,4,5‐hexaphenylsilole (HPS) and/or bis(4‐(N‐(1‐naphthyl) phenylamino)‐phenyl)fumaronitrile (NPAFN), into aqueous solution for biological studies. Compared to their virtually non‐emissive properties in organic solutions, the fluorescence intensity of these AIE dyes has increased significantly due to the spatial confinement that restricts intramolecular rotation of these dyes and their better compatibility in the hydrophobic core of polymeric micelles. The effect of the chemical structure of micelle cores on the photophysical properties of AIE dyes are investigated, and the fluorescence resonance energy transfer (FRET) from the green‐emitting donor (HPS) to the red‐emitting acceptor (NPAFN) is explored by co‐encapsulating this FRET pair in the same micelle core. The highest fluorescence quantum yield (～62%) could be achieved by encapsulating HPS aggregates in the micelles. Efficient energy transfer (>99%) and high amplification of emission (as high as 8 times) from the NPAFN acceptor could also be achieved by spatially confining the HPS/NPAFN FRET pair in the hydrophobic core of polymeric micelles. These micelles could be successfully internalized into the RAW 264.7 cells to demonstrate high‐quality fluorescent images and cell viability due to improved quantum yield and reduced cytotoxicity.     

Self‐Assembly of Diblock‐Copolymer Micelles for Template‐Based Preparation of PbTiO3 Nanograins

A bottom‐up fabrication route for PbTiO₃ nanograins grown on predefined TiO₂ nanostructures used as seeds is presented. The structuring of the TiO₂ seeds is performed using a self‐organized template constructed from a gold‐loaded micellar monofilm. With this fabrication process, TiO₂ seeds and PbTiO₃ grains with diameters of 12 and 30 nm, respectively, are prepared without the need for electron‐beam lithography. The dimensions of the structure imposed by the micellar template are transferred through all the processing steps to the final PbTiO₃ grains. Furthermore, it is shown that the intermicelle distance and the degree of order in the dried monofilm is mainly determined by the preparation conditions, such as the pulling velocity in the dipping process and the strength of the surface–micelle interaction, and not necessarily by the architectural properties (block length and ratio) of the diblock copolymers that build the micelles. The intermicelle spacing in the dried film is much smaller than the micelle dimensions in solution, and approaches the dimensions of a fully collapsed micelle when the dipping process is performed slowly enough.     

Long‐Circulating Drug‐Dye‐Based Micelles with Ultrahigh pH‐Sensitivity for Deep Tumor Penetration and Superior Chemo‐Photothermal Therapy

Nanocarriers for chemo‐photothermal therapy suffer from insufficient retention at the tumor site and poor penetration into tumor parenchyma. A smart drug‐dye‐based micelle is designed by making the best of the structural features of small‐molecule drugs. P‐DOX is synthesized by conjugating doxorubicin (DOX) with poly(4‐formylphenyl methacrylate‐co‐2‐(diethylamino) ethyl methacrylate)‐b‐polyoligoethyleneglycol methacrylate (P(FPMA‐co‐DEA)‐b‐POEGMA) via imine linkage. Through the π–π stacking interaction, IR780, a near‐infrared fluorescence dye as well as a photothermal agent, is integrated into the micelles (IR780‐PDMs) with the P‐DOX. The IR780‐PDMs show remarkably long blood circulation (t_1/2β = 22.6 h). As a result, a progressive tumor accumulation and retention are presented, which is significant to the sequential drug release. Moreover, when entering into a moderate acidic tumor microenvironment, IR780‐PDMs can dissociate into small‐size conjugates and IR780, which obviously increases the penetration depth of drugs, and then improves the lethality to deep‐seated tumor cells. Owing to the high delivery efficiency and superior chemo‐photothermal therapeutic efficacy of IR780‐PDMs, 97.6% tumor growth in the A549 tumor‐bearing mice is suppressed with a low dose of intravenous injection (DOX, 1.5 mg kg^?1; IR780, 0.8 mg kg^?1). This work presents a brand‐new strategy for long‐acting intensive cancer therapy.     

Neuroendocrine Tumor‐Targeted Upconversion Nanoparticle‐Based Micelles for Simultaneous NIR‐Controlled Combination Chemotherapy and Photodynamic Therapy,and Fluorescence Imaging

Although neuroendocrine tumors (NETs) are slow growing, they are frequently metastatic at the time of discovery and no longer amenable to curative surgery, emphasizing the need for the development of other treatments. In this study, multifunctional upconversion nanoparticle (UCNP)‐based theranostic micelles are developed for NET‐targeted and near‐infrared (NIR)‐controlled combination chemotherapy and photodynamic therapy (PDT), and bioimaging. The theranostic micelle is formed by individual UCNP functionalized with light‐sensitive amphiphilic block copolymers poly(4,5‐dimethoxy‐2‐nitrobenzyl methacrylate)‐polyethylene glycol (PNBMA‐PEG) and Rose Bengal (RB) photosensitizers. A hydrophobic anticancer drug, AB3, is loaded into the micelles. The NIR‐activated UCNPs emit multiple luminescence bands, including UV, 540 nm, and 650 nm. The UV peaks overlap with the absorption peak of photocleavable hydrophobic PNBMA segments, triggering a rapid drug release due to the NIR‐induced hydrophobic‐to‐hydrophilic transition of the micelle core and thus enabling NIR‐controlled chemotherapy. RB molecules are activated via luminescence resonance energy transfer to generate ¹O₂ for NIR‐induced PDT. Meanwhile, the 650 nm emission allows for efficient fluorescence imaging. KE108, a true pansomatostatin nonapeptide, as an NET‐targeting ligand, drastically increases the tumoral uptake of the micelles. Intravenously injected AB3‐loaded UCNP‐based micelles conjugated with RB and KE108—enabling NET‐targeted combination chemotherapy and PDT—induce the best antitumor efficacy.     

One‐Step Hierarchical Assembly of Spheres‐in‐Lamellae Nanostructures from Solvent‐Annealed Thin Films of Binary Diblock Copolymer Micelles

Hierarchical assemblies of dissimilar block copolymers (BCPs) can reveal interesting perspectives on material properties and device performance by providing multiple functionalities. Up to now, hierarchical assemblies of BCPs have been mostly prepared by stepwise assembling methods, in which the first type of BCP nanodomains is used as predefined patterns to guide the second‐level assembly of another BCP. On the other hand, single‐step blending methods suffer from a dilemma in the creation of hierarchical patterns because blending dissimilar BCPs typically induces either macrophase separation of component BCPs or chain‐level hybridization into a single morphology. The present study is designed to overcome this apparent dilemma in polymer blends by exploiting a solvent annealing method. In particular, hierarchically assembled spheres‐in‐lamellae structures from a solvent‐annealed blended film of binary polystyrene‐block‐poly(2‐vinylpyrdine) and polystyrene‐block‐poly(4‐vinyl pyridine) micelles are prepared. The focus of the current study is to understand the different effects of solvent vapor on the component BCPs and the molecular mechanism for the one‐step assembling process. By addressing this issue, the parallelism in the phase behavior of BCP micelles and inorganic nanoparticles is highlighted, the underlying physical processes of which could be suggested as a one‐step assembly principle for hierarchical superstructures beyond the previously reported multistep methods.     

Efficient Isolation and Solubilization of Pristine Single‐Walled Nanotubes in Bile Salt Micelles

We have investigated a wide variety of surfactants for their efficiency in dissolving isolated single‐walled carbon nanotubes (SWNTs) in water. In doing so, we have completely avoided the harsh chemical or mechanical conditions, such as acid or ultrasonic treatments, that are known to damage SWNTs. Bile salts in particular are found to be exceptionally effective in dissolving individual tubes, as evidenced by highly resolved optical absorption spectra, bright bandgap fluorescence, and the unprecedented resolution (～ 2.5 cm^–1) of the radial breathing modes in Raman spectra. This is attributed to the formation of very regular and stable micelles around the nanotubes providing an unusually homogeneous environment. Quantitative information concerning the degree of solubilization is obtained from absorption spectroscopy.     

Chemiluminescent and Antioxidant Micelles as Theranostic Agents for Hydrogen Peroxide Associated‐Inflammatory Diseases

Hydrogen peroxide (H₂O₂) is one of essential oxygen metabolites in living organisms, but is generated in large amounts during inflammatory responses. Therefore, H₂O₂ has great potential as diagnostic and therapeutic markers of several inflammatory and life‐threatening diseases. Here, chemiluminescent and antioxidant micelles are reported as novel theranostic agents for H₂O₂‐associated inflammatory diseases. The chemiluminescent micelles composed of amphiphilic block copolymer Pluronic F‐127, hydroxybenzyl alcohol‐incorporated copolyoxalate (HPOX) and fluorescent dyes perform peroxalate chemiluminescence reactions to detect H₂O₂ as low as 100 nM and image H₂O₂ generated in inflamed mouse ankles. The micelles encapsulating HPOX reduce the generation of reactive oxygen species in lipopolysaccharide (LPS)‐activated macrophages by scavenging overproduced H₂O₂ and releasing antioxidant hydroxybenzyl alcohol (HBA). They also exert inhibitory effects on H₂O₂‐induced apoptosis. HPOX‐based chemiluminescent and antioxidant micelles have great potential as a theranostic agent for H₂O₂‐associated inflammatory diseases.     

pH‐ and NIR Light‐Responsive Micelles with Hyperthermia‐Triggered Tumor Penetration and Cytoplasm Drug Release to Reverse Doxorubicin Resistance in Breast Cancer

The acquisition of multidrug resistance (MDR) is a major hurdle for the successful chemotherapy of tumors. Herein, a novel hybrid micelle with pH and near‐infrared (NIR) light dual‐responsive property is reported for reversing doxorubicin (DOX) resistance in breast cancer. The hybrid micelles are designed to integrate the pH‐ and NIR light‐responsive property of an amphiphilic diblock polymer and the high DOX loading capacity of a polymeric prodrug into one single nanocomposite. At physiological condition (i.e., pH 7.4), the micelles form compact nanostructure with particle size around 30 nm to facilitate blood circulation and passive tumor targeting. Meanwhile, the micelles are quickly dissociated in weakly acidic environment (i.e., pH ≤ 6.2) to release DOX prodrug. When exposed to NIR laser irradiation, the hybrid micelles can trigger notable tumor penetration and cytosol release of DOX payload by inducing tunable hyperthermia effect. In combination with localized NIR laser irradiation, the hybrid micelles significantly inhibit the growth of DOX‐resistant MCF‐7/ADR breast cancer in an orthotopic tumor bearing mouse model. Taken together, this pH and NIR light‐responsive micelles with hyperthermia‐triggered tumor penetration and cytoplasm drug release can be an effective nanoplatform to combat cancer MDR.     

Bioinspired Reversibly Cross‐linked Hydrogels Comprising Polypeptide Micelles Exhibit Enhanced Mechanical Properties

Noncovalently cross‐linked networks are attractive hydrogel platforms because of their facile fabrication, dynamic behavior, and biocompatibility. The majority of noncovalently cross‐linked hydrogels, however, exhibits poor mechanical properties, which significantly limit their utility in load bearing applications. To address this limitation, hydrogels are presented composed of micelles created from genetically engineered, amphiphilic, elastin‐like polypeptides that contain a relatively large hydrophobic block and a hydrophilic terminus that can be cross‐linked through metal ion coordination. To create the hydrogels, heat is firstly used to trigger the self‐assembly of the polypeptides into monodisperse micelles that display transition metal coordination motifs on their coronae, and subsequently cross‐link the micelles by adding zinc ions. These hydrogels exhibit hierarchical structure, are stable over a large temperature range, and exhibit tunable stiffness, self‐healing, and fatigue resistance. Gels with polypeptide concentration of 10%, w/v, and higher show storage moduli of ≈1 MPa from frequency sweep tests and exhibit self‐healing within minutes. These reversibly cross‐linked, hierarchical hydrogels with enhanced mechanical properties have potential utility in a variety of biomedical applications.     

Dendron‐Based Micelles for Topical Delivery of Endoxifen: A Potential Chemo‐Preventive Medicine for Breast Cancer

Endoxifen (EDX) is an active metabolite of tamoxifen that has been proven effective in the prevention and treatment of estrogen‐positive breast cancer; however, oral administration of tamoxifen often causes severe side effects. Here, the topical delivery of EDX is explored using polymeric micelles to achieve localized drug delivery with potentially minimal side effects. EDX is encapsulated into dendron micelles (DM) with various surface groups (‐NH₂, ‐COOH, or ‐Ac) and into cationic liposomes as a control. End‐group modification significantly affects the drug loading, where the DM‐COOH micelles allow the most efficient encapsulation. Furthermore, unlike the burst release from the liposomes, all DMs show sustained release of EDX over 6 days. Each formulation is evaluated for its potential to deliver EDX across the skin layers. DMs substantially enhance the permeation of EDX through both mouse (up to 20‐fold) and human (up to 4‐fold) skin samples relative to ethanol, a chemical penetration enhancer. Franz diffusion cell experiments reveal that DM‐COOH induces the highest flux of EDX among all groups. The enhanced drug loading, controlled release profiles, and enhanced skin permeation all demonstrate that DMs are a useful platform for the topical delivery of EDX, offering a potential alternative administration route for chemoprevention.     

Red‐Light‐Controlled Release of Drug–Ru Complex Conjugates from Metallopolymer Micelles for Phototherapy in Hypoxic Tumor Environments

Traditional photodynamic phototherapy is not efficient for anticancer treatment because solid tumors have a hypoxic microenvironment. The development of photoactivated chemotherapy based on photoresponsive polymers that can be activated by light in the “therapeutic window” would enable new approaches for basic research and allow for anticancer phototherapy in hypoxic conditions. This work synthesizes a novel Ru‐containing block copolymer for photoactivated chemotherapy in hypoxic tumor environment. The polymer has a hydrophilic poly(ethylene glycol) block and a hydrophobic Ru‐containing block, which contains red‐light‐cleavable (650–680 nm) drug–Ru complex conjugates. The block copolymer self‐assembles into micelles, which can be efficiently taken up by cancer cells. Red light induces release of the drug–Ru complex conjugates from the micelles and this process is oxygen independent. The released conjugates inhibit tumor cell growth even in hypoxic tumor environment. Furthermore, the Ru‐containing polymer for photoactivated chemotherapy in a tumor‐bearing mouse model is applied. Photoactivated chemotherapy of the polymer micelles demonstrates efficient tumor growth inhibition. In addition, the polymer micelles do not cause any toxic side effects to mice during the treatment, demonstrating good biocompatibility of the system to the blood and healthy tissues. The novel red‐light‐responsive Ru‐containing polymer provides a new platform for phototherapy against hypoxic tumors.     

Rational Design of Tumor Microenvironment‐Activated Micelles for Programed Targeting of Breast Cancer Metastasis

The poor drug delivery to primary and metastatic tumors of breast cancer remains a great challenge for effective antimetastasis therapy. Herein, a tumor microenvironment‐activated cabazitaxel micelles decorated with legumain‐specific melittin (TCM‐legM) are rationally designed for programed targeting of breast cancer metastasis. TCM‐legM is quiescent in blood circulation, but can be specifically activated by the highly expressed legumain in tumor microenvironments to improve their specific targeting and deep penetrating to primary or metastatic tumors. Thereafter, the activated TCM‐legM can be efficiently internalized by cancer cells and motivate the rapid pH‐responsive drug release for antimetastasis therapy. In metastatic 4T1 breast cancer cells, TCM‐legM presents significant inhibition on the proliferation, migration, and invasion activities. In vivo, TCM‐legM can be effectively delivered to both primary and metastatic tumors of breast cancer with deep tumor penetration and efficient cellular internalization, thereby resulting in a notable reduction of tumor growth and producing a 93.4% suppression of lung metastasis. Taken together, the rationally designed TCM‐legM can provide an intelligent drug delivery strategy to enhance the medical performance on treating breast cancer metastasis.     

Rational Design of Polymeric Hybrid Micelles with Highly Tunable Properties to Co‐Deliver MicroRNA‐34a and Vismodegib for Melanoma Therapy

A polymeric hybrid micelle (PHM) system with highly tunable properties is reported to co‐deliver small molecule and nucleic acid drugs for cancer therapy; this system is structurally simple and easy‐to‐fabricate. The PHM consists of two amphiphilic diblock copolymers, polycaprolactone‐polyethylenimine (PCL‐PEI) and polycaprolactone‐polyethyleneglycol (PCL‐PEG). PHMs are rationally designed with different physicochemical properties by simply adjusting the ratio of the two diblock copolymers and the near neutral PHM‐2 containing a low ratio of PCL‐PEI achieves the optimal balance between high tumor distribution and subsequent cellular uptake after intravenous injection. Encapsulating Hedgehog (Hh) pathway inhibitor vismodegib (VIS) and microRNA‐34a (miR‐34a) into PHM‐2 generates the VIS/PHM‐2/34a co‐delivery system. VIS/PHM‐2/34a shows synergistic anticancer efficacy in murine B16F10‐CD44⁺ cells, a highly metastatic tumor model of melanoma. VIS/PHM‐2/34a synergistically attenuates the expression of CD44, a vital receptor indicating the metastasis of melanoma. Intriguingly, inhibiting Hh pathway by VIS is accompanied by downregulation of CD44 expression, revealing that Hh signaling might be an upstream regulator of CD44 expression in melanoma. Thus, co‐delivery of miR‐34a and VIS demonstrates great potential in cancer therapy, and PHM offers a structurally simple and highly tunable platform for the co‐delivery of small molecule and nucleic acid drugs in tumor combination therapy.     

Multifunctional Molecular Beacon Micelles for Intracellular mRNA Imaging and Synergistic Therapy in Multidrug‐Resistant Cancer Cells

Multidrug resistance (MDR) resulting from overexpression of P‐glycoprotein (Pgp) transporters increases the drug efflux and thereby limits the chemotherapeutic efficacy. It is desirable to administer both an MDR1 gene silencer and a chemotherapeutic agent in a sequential way to generate a synergistic therapeutic effect in multidrug‐resistant cancer cells. Herein, an anti‐MDR1 molecular beacon (MB)‐based micelle (a‐MBM) nanosystem is rationally designed. It is composed of a diacyllipid core densely packed with an MB corona. One of Pgp‐transportable agents, doxorubicin (DOX), is encapsulated in the hydrophobic core of the micelle and in the stem sequence of MB. The a‐MBM‐DOX nanosystem shows an efficient self‐delivery, enhanced enzymatic stability, excellent target selectivity, and high drug‐loading capacity. With its relatively high enzymatic stability, a‐MBM‐DOX initially facilitates intracellular MDR1 mRNA imaging to distinguish multidrug‐resistant and non‐multidrug‐resistant cells and subsequently downregulates the MDR1 gene expression owing to an antisense effect. After that, the MB corona is degraded, destroying the micellar nanostructure and releasing DOX, which result in a high accumulation of DOX in OVCAR8/ADR cells and a high chemotherapeutic efficacy because of successful restoration of drug sensitivity. This micelle approach has the potential for both visualizing MDR1 mRNA and overcoming MDR in a sequential and synergistic way.