Block Copolymer Micelles Research Articles

Docetaxel-loaded block copolymer micelles labeled with 188Re for combined radiochemotherapy

Block copolymer micelles (BCMs), nano-self-assemblies of amphiphilic copolymers with a hydrophobic core surrounded by a hydrophilic corona, were explored for the simultaneous delivery of a lipophilic chemotherapeutic drug and radiation to tumors. Docetaxel (DTX)-functionalized BCMs were radiolabeled with the β− emitter 188Re by two different approaches (direct and indirect labelling) affording in both cases 188Re-Pz-DTX-BCMs with high purity (>98%). The 188Re-labeled BCMs are stable in PBS pH 7.4 and in cell culture medium, at 37 °C. Cell uptake of 188Re-Pz-DTX-BCMs in MDA-MB-231 metastatic breast cancer cells and MNNG/HOS osteosarcoma cells presented a maximal uptake of ca. 12% at 24 h incubation time. Biodistribution studies in tumor-bearing nude mice (MDA-MB-231 human xenografts) has shown prolonged circulation lifetime in the bloodstream and moderate uptake in the tumor (1.8 ± 0.8% I.A./g at 24 h p.i.). The prolonged blood circulation lifetime together with the in vivo stability, suggests that the micelles are potentially useful as drug delivery system to tumors by the EPR effect. As far as we are aware, we describe herein the first example of BCMs, 188Re-Pz-DTX-BCMs, as versatile nanoplatforms for the simultaneous delivery of beta radiation (188Re) and the chemotherapeutic drug (DTX) potentially useful for cancer therapy. The expected synergistic effect of such combination in pain therapy and/or cancer progression holds promise when compared to the conventional sequential treatment.

Scattering Form Factor of Block Copolymer Micelles with Corona Chains Discretely Distributed on the Core Surface.

Small-angle scattering is a powerful tool to investigate micellar structure, and a model form factor proposed by Pedersen and Gerstenberg [Pedersen, J. S.; Gerstenberg, M. Macromolecules 1996, 29, 1363-1365] has been used quite frequently to analyze experimentally obtained scattering data of block copolymer micelles. Their model consists of a spherical core and the Gaussian corona chains attached to the core surface; the corona chains are considered to be approximately continuously (evenly) distributed on the core surface. In this paper, we present a micellar form factor model in which the corona chains are discretely distributed on the core surface. Our proposed discrete model was found to deviate from the Pedersen-Gerstenberg model as well as another model [Svaneborg, C.; Pedersen, J. S. Phys. Rev. E 2001, 64, R01802.], which incorporates the approximate interference effect between the corona chains, in conditions in which the scattering from the corona chains is stronger than that from a core with lower number density of the corona chains.

Three-dimensional superlattice engineering with block copolymer epitaxy.

Three-dimensional (3D) structures at the nanometer length scale play a crucial role in modern devices, but their fabrication using traditional top-down approaches is complex and expensive. Analogous to atomic lattices, block copolymers (BCPs) spontaneously form a rich variety of 3D nanostructures and have the potential to substantially simplify 3D nanofabrication. Here, we show that the 3D superlattice formed by BCP micelles can be controlled by lithographically defined 2D templates matching a crystallographic plane in the 3D superlattice. Using scanning transmission electron microscopy tomography, we demonstrate precise control over the lattice symmetry and orientation. Excellent ordering and substrate registration can be achieved, propagating through 284-nanometer-thick films. BCP epitaxy also showed exceptional lattice tunability, with a continuous Bain transformation from a body-centered cubic to a face-centered cubic lattice. Lattice stability was mediated by molecular packing frustration, and surface-induced lattice reconstruction was observed, leading to the formation of a unique honeycomb lattice.

Block Copolymer Micelles Generated by Crystallization-Driven Self-Assembly in Polymer Matrices

In this review, we show how Crystallization-Driven Self-Assembly (CDSA), a method originally employed for the self-assembly of block copolymers in solution, was extended to the synthesis of elongated micellar nanostructures in polymer matrices. By highlighting some of the works published by our group in this area, the conditions to synthesize nanostructured polymers by CDSA are discussed. The knowledge of these conditions will allow developing a new generation of nanomaterials with tailored architecture based on a given application.

Soft Confined Assembly of Polymer-Tethered Inorganic Nanoparticles in Cylindrical Micelles

Cylindrical block copolymer (BCP) micelles could be considered as two-dimensional (2D) soft confined space for assembly of inorganic nanoparticles (NPs). However, the deformable boundary of the mic...

Silicon Tetrapyrazinoporphyrazine Derivatives-Incorporated Carbohydrate-Based Block Copolymer Micelles for Photodynamic Therapy.

Developing nonaggregated photosensitizers (PSs) for efficient photodynamic therapy (PDT) using polymeric micelles (PMs) has been challenging. In this study, axially substituted nonaggregated silicon tetrapyrazinoporphyrazine (SiTPyzPz) derivatives in carbohydrate-based block glycopolymer-based PMs were designed and used as PSs for PDT. To achieve the nonaggregated PSs, SiTPyzPz was axially substituted with trihexylsiloxy (THS) groups to form SiTPyzPz-THS, which exhibited highly monomeric behaviors in organic solvents. Moreover, three block copolymers were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Each copolymer comprised hydrophobic polystyrene blocks and loadable SiTPyzPz-THS, and one or two consisted of two possible hydrophilic blocks, polyethylene glycol or poly(glucosylethyl methacrylate). The self-assembly of SiTPyzPz-THS and the block copolymers in aqueous solvents induced the formation of spherical PMs with core-shell or core-shell-corona structures. The SiTPyzPz-THS in the PMs exhibited monomeric state, intense fluorescence emission, and outstanding singlet oxygen generation; moreover, it did not form aggregates. During the in vitro test, which was performed to investigate the PDT efficiency, the PMs, which consisted of poly(glucosylethyl methacrylate) shells, exhibited high photocytotoxicity and cellular internalization ability. Consequently, the PM systems of nonaggregated PSs and carbohydrate-based block copolymers could become very promising materials for PDT owing to their photophysicochemical properties and considerable selectivity against cancer cells.

Designer Nanoparticles as Robust Superlubrication Vectors.

Phosphatidylcholine lipid bilayers or liposomes at interfaces in aqueous environments can provide extremely efficient lubrication. This is attributed to the hydration lubrication mechanism acting at the highly hydrated phosphocholine-headgroup layers exposed at the outer surface of each bilayer. Micelles exposing such phosphocholine groups could be an attractive alternative to liposomes due to their much easier preparation and structure control, but all studies to date of surfactant micelles have revealed that at relatively low normal stresses the surface layers rupture and friction increases abruptly. Here, we examine surface interactions between three kinds of phosphocholine-exposing micelles with different designed structures: single-tail surfactant micelles, homo-oligomeric micelles, and block copolymer micelles. Normal and shear forces between mica surfaces immersed in solutions of these micelles were measured using a surface force balance. The adsorbed layers on the mica were imaged using atomic force microscope, revealing surface structures ranging from wormlike to spherical micelles. The block copolymer micelles showed relatively low coverage arising from their stabilizing corona and consequently poor lubrication (μ ∼ 10–1). In contrast, the surfactant and homo-oligomeric micelles fully covered the mica surface and demonstrated excellent lubrication (μ ∼ O(10–3)). However, while the boundary layer of single-tailed surfactant micelles degraded under moderate pressure, the homo-oligomeric micellar boundary layer was robust at all applied contact pressures in our study (up to about 5 MPa). We attribute the difference to the much greater energy required to remove a homo-oligomeric molecule from its micelle, resulting in far greater stability under pressure and shear.

Direct Observation of Micelle Fragmentation via In Situ Liquid-Phase Transmission Electron Microscopy.

Recently, attention has been directed toward understanding the dynamics and relaxation kinetics of block copolymer micelles, including mechanisms such as micelle fragmentation and fusion. The few prior studies on block copolymer micelle fragmentation relied on ensemble averaging techniques such as small-angle X-ray scattering and dynamic light scattering; some individual particles were imaged by ex situ transmission electron microscopy. Here we report the direct observation of fragmentation for three molecular weights of 1,2-polybutadiene-block-poly(ethylene oxide) (PB-PEO) micelles in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide using high-temperature liquid-phase transmission electron microscopy (LP-TEM). The use of in situ LP-TEM provides unique insights into the evolution of block copolymer micelles during fragmentation. Specifically, upon heating to 170 °C, a sequence of morphological transitions from a spherical micelle to a prolate ellipsoid, then a "peanut" shape, followed by a two-spherical-compartment micelle was observed, where the last is presumed to be the transition state.

Cationic Block Copolymer Nanoparticles with Tunable DNA Affinity for Treating Rheumatoid Arthritis

AbstractA high concentration of cell‐free DNA (cfDNA) in joints is considered a disease causative agent of rheumatoid arthritis (RA) and cfDNA scavenging has been regarded as an efficient therapeutic avenue. Cationic polymers can hamper progression of joint inflammation in a rat model of RA by scavenging cfDNA; however, they may cause systemic toxicity due to the strong positive charges. To reduce the toxicity, herein a library of cationic nanoparticles (cNPs) of block copolymer micelles is developed and the effects of structure and surface composition on cNP efficacy to bind nucleic acids, toxicity, and therapeutic activity on a collagen induced arthritis (CIA) rat model of RA are assessed. The library includes cNPs with a homoshell from poly(lactic‐co‐glycolic acid)‐block‐poly(2‐(dimethylamino)ethyl methacrylate) (PLGA‐b‐PDMA) block copolymers and cNPs with a mixed shell of poly(ethylene glycol) (PEG) and PDMA by coself‐assembling PLGA‐b‐PDMA and PLGA‐b‐PEG block copolymers. Relatively to the homoshell cNPs, introduction of PEG segments translates into a lower DNA binding efficacy while preserving ability to hamper joint inflammation. Moreover, they show a greater accumulation and longer retention at the inflamed joints, allowing a lower administration frequency. In conclusion, this work shows that the therapeutic index of cationic materials can be tuned by introducing surface neutral moieties.

Novel neuroprotection using antioxidant nanoparticles in a mouse model of head trauma.

Free radicals and reactive oxygen species are related to deteriorating pathological conditions after head trauma because of their secondary effects. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) scavenges free radicals; however, this molecule is also toxic. Here, we have evaluated the neuroprotective effect of antioxidant nanoparticles, which consisted of a novel core-shell type nanoparticle containing 4-amino-TEMPO, that is, redox-active nitroxide radical-containing nanoparticles (RNPs). Institute of Cancer Research mice were subjected to a head-impact procedure, randomly divided into four groups and intravenously (3 mg/kg) administered phosphate-buffered saline, TEMPO, micelle (a self-assembling block copolymer micelle without a TEMPO moiety), or RNP through the tail vein immediately thereafter and intraperitoneally at days 1, 3, and 5 after traumatic brain injury (TBI). The RNP distribution was detected by rhodamine labeling. Cognitive behavior was assessed using the neurological severity score and a rotarod test at days 1, 3, and 7 following TBI, and contusion volume was measured at day 7 after TBI. Free radical-scavenging capacity was analyzed by electron paramagnetic resonance on day 1 after TBI, and immunostaining was used to observe mobilization of microglia (Iba-1) and rescued neuronal cells (NeuN). Redox-active nitroxide radical-containing nanoparticle was detected in the microvessels around the injured area in the brain. Cognitive behavior assessment was significantly better, and contusion volume was significantly smaller in the RNP group compared with the other groups. Superoxide anion scavenging capacity was significantly higher in the RNP group, and neuronal loss was significantly suppressed around the injured area at day 7 after TBI. Furthermore, in the RNP group, neurodegenerative microglia production was suppressed at days 3 and 7 after TBI, whereas neuroprotective microglia production was higher at day 7 after TBI. The RNP administration after TBI improved cognitive behavior and reduced contusion volume by improving reactive oxygen species scavenging capacity. Therefore, RNP may have a neuroprotective effect after TBI. Therapeutic test.

Enhancing Targeted Cancer Treatment by Combining Hyperthermia and Radiotherapy Using Mn-Zn Ferrite Magnetic Nanoparticles.

Radiotherapy (RT) is a major treatment method for non-small-cell lung cancer (NSCLC), and development of new treatment modality is now critical to amplify the negative effects of RT on tumors. In this study, we demonstrated a nanoparticle-loaded block copolymer micellar system for cancer hyperthermia treatment (HT) that can be used for synergistic therapy under alternating magnetic field (AMF) and radiation field. Block copolymer micelles (polyethylene glycol-block-polycaprolactone, or PEG-PCL) containing hyaluronic acid (HA) and Mn-Zn ferrite magnetic nanoparticles (MZF) were fabricated via a two-step preparation. HA-modified Mn-Zn ferrite magnetic nanoparticles (MZF-HA) can be enriched in CD44 highly expressing tumor cells, such as A549 (human lung adenocarcinoma cell line), through an active targeting mechanism via receptor-ligand binding of HA and CD44 (HA receptor). MZF can generate thermal energy under an AMF, leading to a local temperature increase to approximately 43 °C at tumor sites for mild HT, and the increased tumor oxygenation can enhance the therapeutic effect of RT. In vitro experiments show that MZF-HA is able to achieve excellent specific targeting performance toward A549 cells with excellent biocompatibility as well as enhanced therapy performance under HT and RT in vitro by apoptosis flow cytometry. In the A549 subcutaneous tumor xenografts model, MRI confirms the enrichment of MZF-HA in tumor, and hypoxia immunohistochemistry analysis (IHC) proved the increased tumor oxygenation after HT. Furthermore, the tumor volume decreases to 49.6% through the combination of HT and RT in comparison with the 58.8% increase of the untreated group. These results suggest that the application of MZF-HA is able to increase the therapeutic effect of RT on A549 and can be used for further clinical NSCLC treatment evaluation.

Polypseudorotaxanes of Pluronic® F127 with Combinations of α- and β-Cyclodextrins for Topical Formulation of Acyclovir.

Acyclovir (ACV) is one of the most used antiviral drugs for the treatment of herpes simplex virus infections and other relevant mucosal infections caused by viruses. Nevertheless, the low water solubility of ACV limits both its bioavailability and antiviral performance. The combination of block copolymer micelles and cyclodextrins (CDs) may result in polypseudorotaxanes with tunable drug solubilizing and gelling properties. However, the simultaneous addition of various CDs has barely been investigated yet. The aim of this work was to design and characterize ternary combinations of Pluronic® F127 (PF127), αCD and βCD in terms of polypseudorotaxane formation, rheological behavior, and ACV solubilization ability and controlled release. The formation of polypseudorotaxanes between PF127 and the CDs was confirmed by FT-IR spectroscopy, X-ray diffraction, and NMR spectroscopy. The effects of αCD/βCD concentration range (0–7% w/w) on copolymer (6.5% w/w) gel features were evaluated at 20 and 37 °C by rheological studies, resulting in changes of the copolymer gelling properties. PF127 with αCD/βCD improved the solubilization of ACV, maintaining the biocompatibility (hen’s egg test on the chorio-allantoic membrane). In addition, the gels were able to sustain acyclovir delivery. The formulation prepared with similar proportions of αCD and βCD provided a slower and more constant release. The results obtained suggest that the combination of Pluronic with αCD/βCD mixtures can be a valuable approach to tune the rheological features and drug release profiles from these supramolecular gels.

Co‐Assembly of Gd(III)‐Based Metallosurfactant and Conjugated Polymer Nanoparticles in Organosilica Cross‐Linked Block Copolymer Micelles for Highly Efficient MRI and Fluorescent Bimodal Imaging

AbstractConformity of two biological imaging entities, magnetic resonance imaging (MRI) and fluorescence imaging, is achieved through co‐assembly of a Gd(III)‐based metallosurfactant, conjugated polymeric nanoparticles, and amphiphilic block copolymer F127 (PEO106PPO70PEO106) followed by crosslinking with organosilica. The cross‐linked micelles with a size around 100 nm exhibit outstanding dispersion stability in aqueous and phosphate buffered saline solutions, bright fluorescence emission, and high relaxivities, providing a new approach to synthesize highly efficient bimodal contrast agents. The relaxivities of the co‐assembled micelles are synergistically enhanced by incorporation of Gd(III) complexes with high hydration number (q = 3) and elongation of rotation correlation time to achieve r1 values up to 105.37 mm−1 s−1 (at 1.5 T), which is over 20 times that of clinically used MRI contrast agents and among the highest values of all the nanoparticular MRI contrast agents. The external PEO layer endows these micelles with very low cytotoxicity for both in vitro and in vivo imaging. Meanwhile, thanks to the enhanced permeability and retention effect originating from their nanoscale sizes, the bimodal contrast agents show a prolonged blood circulation time in vivo and targeted accumulation at tumor regions to display outstanding MRI imaging performance.

Preparation of polyethylene glycol-polyacrylic acid block copolymer micelles with pH/hypoxic dual-responsive for tumor chemoradiotherapy

Block copolymers of poly(ethylene glycol)-poly(acrylic acid) linked with metronidazole (MN-PAA-PEG) were prepared via carbodiimide and esterification methods, and self-assembled into core-shell micelles as nano radiosensitizers and carriers of doxorubicin (DOX) delivery. These DOX/MN-PAA-PEG micelles exhibited good pH value and hypoxia dual-responsive properties via analyzing the change of micelle size and drug‒release behavior under hypoxia humor condition. The results of the cell test indicated that DOX was efficiently delivered by DOX/MN-PAA-PEG micelles into the cell nuclei. Compared to 22.4 % of their DOX release under pH 7.4, the rate of DOX release from DOX/MN-PAA-PEG micelles under reducing condition (pH 5.0) was up to 55.9 %. DOX-loaded micelles under 600 MU electron radiation and hypoxia induced the rapidest apoptosis of the tumor-cells, indicating the synergistic effect of their radiotherapy and chemotherapy from the prepared micelles. In vivo investigation and fluorescence imaging revealed that MN-PAA-PEG possessed no toxicity on main organs, and DOX/MN-PAA-PEG micelles were mainly accumulated in the tumor site at 10 h of post-injection, suggesting their good passive tumor-targeted effect. These results suggested that DOX/MN-PAA-PEG micelles were promising candidates for chemoradiotherapy on tumor.

Contrast variation of micelles composed of Ca2+ and block copolymers of two negatively charged polyelectrolytes

Block copolymers were prepared with two anionic polyelectrolyte blocks: sodium polyacrylate (PA) and sodium polystyrene sulfonate (PSS), in order to investigate their phase behavior in aqueous solution in the presence of Ca2+ cations. Depending on the concentration of polymer and Ca2+ and on the ratio of the block lengths in the copolymer, spherical micelles were observed. Micelle formation arises from the specific interaction of Ca2+ with the PA block only. An extensive small-angle scattering study was performed in order to unravel the structure and dimensions of the block copolymer micelles. Deuteration of the PA block enabled us to perform contrast variation experiments using small-angle neutron scattering at variable ratios of light and heavy water which were combined with information from small-angle X-ray scattering and dynamic light scattering.Graphical Block copolymers with two anionic polyelectrolyte blocks, sodium polyacrylate (PA) and sodium polystyrene sulfonate (PSS) self-assemble in response to an addition of Ca2+ cations. Deuteration of the PA block made possible contrast variation experiments using SANS at variable ratios of H2O/D2O, which in combination with SAXS revealed the morphology of the self-assemblies.

Influence of Core Cross-Linking and Shell Composition of Polymeric Micelles on Immune Response and Their Interaction with Human Monocytes.

Block copolymer micelles have received increasing attention in the last decades, in particular for their appealing properties in nanomedicine. However, systematic investigations of the interaction between polymeric micelles and immune cells are still rare. Therefore, broader studies comparing the structural effects remain inevitable for a comprehensive understanding of the immune response and for the design of efficient, nonimmunogenic delivery systems. Here, we present novel block copolymer micelles with the same hydrophobic core, based on a copolymer of BA and VDM, and various hydrophilic shells ranging from common PEG derivatives to morpholine-based materials. The influence of these shells on innate immune responses was studied in detail. In addition, we investigated the impact of micelle stability by varying the cross-linking density in the micellar core. Surprisingly, whereas different shells had only a minor impact on immune response, micelles with reduced cross-linking density considerably enhanced the release of cytokines from isolated human monocytes. Moreover, the uptake of non-cross-linked micelles by monocytes was significantly higher as compared to cross-linked materials. Our study emphasizes the importance of the micellar stability on the interaction with the immune system, which is the key for any stealth properties in vivo. Polymers based on morpholines result in a similar low response as the PEG derivative and may represent an interesting alternative to the common PEGylation.

Block copolymer micelles confined in cylindrical nanopores: Effects of annealing solvents and hybridization

Amphiphilic block copolymer micelles have been intensively investigated and applied into various research fields for decades. One of the most promising characteristics for block copolymer micelles is the selective incorporation of metal precursors in the cores or coronas of the micelles. By combining with nanoporous membranes, aligned polymer nanostructures can be generated, facilitating the applications such as nanolithography and catalysis. The morphology transitions and controllability of block copolymer micelles in confined geometries, however, have seldom been studied. In addition, for hybrid micelles in which polymer segments are selectively incorporated with inorganic metal precursors, the relationship between hybridization and morphologies of polymer nanostructures in the confined states is still under discussion. In this work, we investigate the effects of annealing solvents and hybridization with metal precursors (gold(III) chloride trihydrate (HAuCl4 · 3H2O)) on the morphologies of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer micelles confined in the nanopores of anodic aluminum oxide (AAO) templates. Tuned by the annealing solvent vapors and the selective ion complexation between HAuCl4 and P4VP cores, various morphologies can be effectively controlled, such as the spherical-micelles-in-rod morphology, the parallel-cylinders-in-rod morphology, and the hemispherical-micelles-in-rod morphology. This study not only investigates the effects of annealing solvent vapors and hybridization on the morphologies of block copolymer micelles confined in cylindrical nano-geometries but also offers a viable route for preparing metal nanoparticles embedded in porous templates.

The Importance of Cooperativity in Polymer Blending: Toward Controlling the Thermoresponsive Behavior of Blended Block Copolymer Micelles.

Understanding, predicting, and controlling the self-assembly behavior of stimuli-responsive block copolymers remains a pertinent challenge. As such, the copolymer blending protocol provides an accessible methodology for obtaining a range of intermediate polymeric nanostructures simply by blending two or more block copolymers in the desired molar ratio to target specific stimuli-responsiveness. Herein, thermoresponsive diblock copolymers are blended in various combinations to investigate whether the resultant cloud point temperature can be modulated by simple manipulation of the molar ratio. Thermoresponsive amphiphilic diblock copolymers composed of statistical poly(n-butyl acrylate-co-N,N-dimethylacrylamide) core-forming blocks and four different thermoresponsive corona-forming blocks, namely poly(diethylene glycol monomethyl ether methacrylate) (p(DEGMA)), poly(N-isopropylacrylamide), poly(N,N-diethylacrylamide), and poly(oligo(ethylene glycol) monomethyl ether methacrylate) (p(OEGMA)) are selected for evaluation. Using variable temperature turbidimetry, the thermoresponsive behavior of blended diblock copolymer self-assemblies is assessed and compared to the thermoresponsive behavior of the constituent pure diblock copolymer micelles to determine whether comicellization is achieved and more significantly, whether the two blended corona-forming thermoresponsive blocks exhibit cooperative behavior. Interestingly, blended diblock copolymer micelles composed of p(DEGMA)/p(OEGMA) mixed coronae display cooperative behavior, highlighting the potential of copolymer blending for the preparation of stimuli-responsive nanomaterials in applications such as oil recovery, drug delivery, biosensing, and catalysis.

Synthesis and Characterization of pH-Responsive PEG-Poly(β-Amino Ester) Block Copolymer Micelles as Drug Carriers to Eliminate Cancer Stem Cells

PEG-poly(β-amino ester) (PEG-PBAE), which is an effective pH-responsive copolymer, was mainly synthesized by Michael step polymerization. Thioridazine (Thz), which was reported to selectively eliminate cancer stem cells (CSCs), was loaded into PEG-PBAE micelles (PPM) prepared by self-assembly at low concentrations. The critical micelle concentrations (CMC) of PPM in water were 2.49 μg/mL. The pH-responsive PBAE segment was soluble due to protonated tertiary amine groups when the pH decreased below pH 6.8, but it was insoluble at pH 7.4. The Thz-loaded PEG-PBAE micelle (Thz/PPM) exhibited a spherical shape, and the drug loading was 15.5%. In vitro release of Thz/PPM showed that this pH-sensitivity triggered the rapid release of encapsulated Thz in a weakly acidic environment. The in vitro cytotoxicity and cellular uptake of various formulations at pH 7.4 and 5.5 were evaluated on the mammospheres (MS), which were sorted by MCF-7 human breast cancer cell lines and identified to be a CD44+/CD24− phenotype. The results of the cytotoxicity assay showed that blank micelles were nontoxic and Thz/PPM exhibited a similar anti-CSC effect on MS compared to Thz solution. Stronger fluorescence signal of Coumarin-6 (C6) was observed in MS treated by C6-loaded PPM (C6/PPM) at pH 5.5. The tumor inhibition rate and tumor weight of the free DOX and Thz/PPM groups were significantly different from those of the other groups, which free DOX and Thz/PPM effectively suppressed breast tumor growth in vivo. The above experimental results showed that Thz/PPM is an ideal and effective pH-responsive drug delivery carrier to a targeted therapy of CSCs.

Integrin Subtypes and Nanoscale Ligand Presentation Influence Drug Sensitivity in Cancer Cells.

Cancer cell–matrix interactions have been shown to enhance cancer cell survival via the activation of pro-survival signaling pathways. These pathways are initiated at the site of interaction, i.e., integrins, and thus, their inhibition has been the target of therapeutic strategies. Individual roles for fibronectin-binding integrin subtypes αvβ3 and α5β1 have been shown for various cellular processes; however, a systematic comparison of their function in adhesion-dependent chemoresistance is lacking. Here, we utilize integrin subtype-specific peptidomimetics for αvβ3 and α5β1, both as blocking agents on fibronectin-coated surfaces and as surface-immobilized adhesion sites, in order to parse out their role in breast cancer cell survival. Block copolymer micelle nanolithography is utilized to immobilize peptidomimetics onto highly ordered gold nanoparticle arrays with biologically relevant interparticle spacings (35, 50, or 70 nm), thereby providing a platform for ascertaining the dependence of ligand spacing in chemoprotection. We show that several cellular properties—morphology, focal adhesion formation, and migration—are intricately linked to both the integrin subtype and their nanospacing. Importantly, we show that chemotherapeutic drug sensitivity is highly dependent on both parameters, with smaller ligand spacing generally hindering survival. Furthermore, we identify ligand type-specific patterns of drug sensitivity, with enhanced chemosurvival when cells engage αvβ3 vs α5β1 on fibronectin; however, this is heavily reliant on nanoscale spacing, as the opposite is observed when ligands are spaced at 70 nm. These data imply that even nanoscale alterations in extracellular matrix properties have profound effects on cancer cell survival and can thus inform future therapies and drug testing platforms.