π-Conjugated-polymer-based fiberlike nanostructures show promising potential in applications ranging from biomedicine to microelectronic devices as a consequence of their shape and their intrinsic ...optoelectronic characteristics. However, these structures can be fragile and subject to dissociation at elevated temperatures or in the presence of certain solvents, and they can be difficult to functionalize. To address these problems, we have synthesized a diblock copolymer containing a π-conjugated crystalline oligo(p-phenylene vinylene) (OPV) segment and a poly(3-(triethoxysilyl)propyl methacrylate) (PTESPMA) block (OPV5-b-PTESPMA35, the subscripts represent the (mean) number of repeat units of each block). Uniform fiberlike micelles of controlled length from 50 nm to ∼1.2 μm with an OPV core were obtained by self-seeding in ethanol. The PTESPMA corona was then cross-linked by an in situ siloxane condensation without micelle aggregation or degradation. The integrity and colloidal stability of micelles were preserved in a good solvent for the OPV block, in a THF/ethanol mixture (v/v = 4/1), and also upon heating in ethanol at 80 °C. Amino groups were installed onto the surface of shell-cross-linked micelles via second-step siloxane condensation by employing the Si-OH groups of the shell as anchoring sites. The amino groups can be used for further introduction of desired functionalities, e.g., Rhodamine B. In addition, trimethylammonium groups were incorporated onto the surface of micelles. These cationic groups not only endow the micelles with excellent colloidal stability in water without micelle aggregation and fragmentation but also enable the micelles to bind double-stranded DNA. In this way, they may possibly serve as vectors for gene therapy. This work opens a new avenue toward π-conjugated-polymer-based fiberlike nanostructures with excellent length tunability, mechanical and colloidal stability, and a capacity for surface functionalization.
Self-seeding of copolymers with a π-conjugated crystalline segment has been considered to be a versatile approach of living crystallization-driven self-assembly to generate uniform fiber-like ...nanostructures with a semiconducting core. The structure of a core-forming block, one of the most important factors affecting the self-seeding process, has not yet been systematically investigated. We synthesized three well-defined diblock copolymers of OBPV n -b-PNIPAM OBPV = oligo(2,5-dibutyloxy-1,4-phenylenevinylene), PNIPAM = poly(N-isopropyl acrylamide), with n = 4, 5, 6, and the same corona-forming PNIPAM block. Here, the subscripts represent the number of repeat units of each block. We then examined in detail their self-assembly behavior, especially under self-seeding conditions. OBPV4-b-PNIPAM49 formed short fiber-like micelles in methanol, but aggregated into ill-defined structures in ethanol and in isopropanol. In contrast, both OBPV5-b-PNIPAM49 and OBPV6-b-PNIPAM49 formed fiber-like micelles of uniform width and with lengths of about 1–2 μm in these solvents. Fiber-like micelles with a broad length distribution were formed by self-seeding of OBPV4-b-PNIPAM49 in methanol. Although uniform fiber-like micelles of controlled lengths can be generated via self-seeding of OBPV5-b-PNIPAM49 and OBPV6-b-PNIPAM49 in methanol, only short fiber-like micelles with a length of about 94 nm were obtained for OBPV6-b-PNIPAM49. Self-seeding of OBPV5-b-PNIPAM49 and OBPV6-b-PNIPAM49 in ethanol gave uniform micelles of controlled lengths. It is interesting to note that the resistance of seed fragments of OBPV6-b-PNIPAM49 toward dissolution is much stronger than that of OPV5-b-PNIPAM49 in these solvents, even though OBPV6 has only one more phenylene vinylene unit than OBPV5. These results demonstrate that the OBPV chain length significantly affects the self-seeding behavior of OBPV-based copolymers. Intriguingly, uniform comicelles with a heterogeneous core of OBPV5 and OBPV6 can be prepared by self-seeding of a mixture of OBPV5-b-PNIPAM49 and OBPV6-b-PNIPAM49, indicative of the great potential of synergistic self-seeding in the fabrication of semiconducting nanofibers with a heterogeneous core.
The self-assembly of block copolymers in solution leads to micellar structures with various morphologies. One way to modify the morphology of these micelles is to blend the block copolymer with a ...homopolymer corresponding to the core-forming block. Although the self-assembly of blends of amorphous homopolymers and block polymers has been extensively studied, there are few examples of solution self-assembly of blends of a core-crystalline block copolymer with a semicrystalline homopolymer. Here we describe a systematic study of the assembly in decane of blends of a polyferrocenylsilane-block-polyisoprene sample (PFS48-b-PI264) with two different PFS homopolymer samples (PFS50 and PFS20). We examine the structures formed as a function of blend composition and compare them to the structures formed from the individual components. PFS48-b-PI264 itself forms long cylindrical micelles, while the two homopolymer samples form stacks of lamellar crystals. Self-assembly of block copolymer mixtures leads to structures with an elongated planar core and fiber-like protrusions from the ends. The details of the structure vary in an interesting and systematic way as the ratio of homopolymer/block copolymer is increased, with important differences seen for the PFS50 and PFS20 homopolymer samples. This study demonstrates that cocrystallization plays a crucial role in determining the structures formed from these mixtures.
Crystalline-coil block copolymers (BCPs) with an amphiphilic corona-forming block broaden the range of solvents in which crystallization-driven self-assembly experiments can be carried out. These ...materials allow one to examine how rather large changes in solvent polarity can affect the self-assembly process, leading to novel uniform structures. Here, we describe the synthesis and self-assembly properties of a crystalline-brush BCP, PFS27-b-P(EG-E)MA48 (PFS, poly(ferrocenyldimethylsilane), and P(EG-E)MA, poly(tetraethylene glycol monododecyl ether methacrylate); the subscripts refer to the mean degrees of polymerization). Tetrahydrofuran (THF) is a common good solvent for both blocks, whereas the corona polymer itself is soluble in alcohols ranging from 2-propanol to 1-decanol and in octane and decane. Self-assembly in 2-propanol was “normal”, forming long (>5 μm) fiber-like micelles of uniform width when the polymer suspended in solvent was heated (i.e., 80 °C) and cooled. Micelles of similar width but uniform and variable length were obtained when micelle fragments were subjected to seeded growth or self-seeding conditions. In primary alcohols (1-butanol to 1-decanol), direct self-assembly led to uniform scarf-like structures (total length ∼2 μm) in which the length of the central platelet increased with the carbon number in the solvent, offset by shorter fiber-like protrusions at the ends. We speculate that these changes are related to the temperature at which core crystallization occurred as the samples cooled. Self-assembly in decane was more complicated. Large (>10 μm) aggregated structures consisting of fiber bundles formed initially. Sonication followed by seeded growth with additional BCP or self-seeding led to relatively uniform elongated lenticular micelles, substantially wider than those formed under these protocols for this BCP in 2-propanol. Solvent polarity has a profound effect on the self-assembly of this BCP with a brush-like amphiphilic corona-forming block.
We describe the crystallization-driven self-assembly of a poly(ferrocenyldimethylsilane) (PFS) block copolymer PFS50-b-P(EG-E)MA48 with amphiphilic pendant groups in the corona-forming block ...P(EG-E)MA (poly(tetraethylene glycol monododecyl ether methacrylate)). The block ratio in terms of the degree of polymerization (the subscripts) was designed to be close to 1 in order to promote formation of two-dimensional micelles by self-assembly in poor solvents for the PFS block. The amphiphilic corona-forming block is soluble in a wide variety of solvents of distinct hydrophilicities and polarities (e.g., 2-propanol, 1-pentanol, 1-octanol, and decane). This property enabled us to examine self-assembly of the block copolymer by the seeded growth protocol in this wide range of different solvents. In 2-propanol, self-assembly was difficult to study except at very low seed micelle concentrations and led to the formation of rounded rectangular platelets. Nearly circular but uniform disks formed in 1-pentanol, and leaf-shaped structures with irregular edges formed in 1-octanol. In 1-pentanol, 3D circular spirals were formed at elevated levels of unimer addition, presumably due to screw dislocations. These structures are all very different from the spherulite objects that we reported previously (Angew. Chem. Int. Ed, 2021, 60, 10,950–10,956) for similar self-assembly experiments with this polymer in decane. We also examine the transition in morphology in mixtures of decane and 1-octanol.
Solution self-assembly of a series of linear ABC triblock terpolymers with a central crystallizable poly(ferrocenyldimethylsilane) (PFS) core-forming “B” block and terminal polystyrene (PS) and ...poly(methyl methacrylate) (PMMA) “A” and “C” blocks has been investigated. Three PS-b-PFS-b-PMMA triblock terpolymers with different block ratios (1, 3.6:1.0:4.7; 2, 7.0:1.0:6.9; and 3, 1.1:1.0:1.4) but with similar degrees of polymerization for the central PFS block were prepared through a combination of living anionic and atom-transfer radical polymerization techniques, together with azide/alkyne “click” chemistry. Cylindrical micelles with a crystalline PFS core were formed in solvents selective for the terminal PS and PMMA blocks. In ethyl acetate, a slightly more selective solvent for the PS block, cylinders with significant microphase separation within the corona in the dry state were observed on the basis of TEM analysis. The use of acetone, which is slightly more selective for the PMMA block than the PS block, led to more distinct microphase separation to generate a “patchy” coronal morphology. Living crystallization-driven self-assembly studies in acetone allowed the formation of uniform cylindrical micelles and block comicelles of controlled length with “patchy” coronal segments by seeded growth methods.
Mass cytometry (MC) measures metal isotope signals from single cells and bead samples. Since large numbers of isotopes can be employed as labels, mass cytometry is a powerful analytical technique for ...multiparameter cytometric assays. The calibration protocol in MC is a critical algorithm, which employs metal-encoded microbeads as an internal standard to correct the data for instrumental signal drift. The current generation of commercially available beads carries four lanthanide elements (cerium, europium, holmium, and lutetium). However, this is not sufficient to calibrate the full span of detection channels, ranging from yttrium (89 amu) to bismuth (209 amu), which are now available. To address this issue we prepared polystyrene microbeads encoded with seven elements (yttrium, indium, and bismuth in addition to the four lanthanides) by multistage dispersion polymerization for MC calibration and normalization. The bead synthesis conditions were optimized to obtain microbeads that were uniform in size and generated strong MC signal intensities at similar levels for the eight encoded isotopes. Metal ion leaching from the beads under storage and application conditions was also examined. We demonstrated that the precision of normalized MC signals in the MC detection channels was improved by employing seven-element-encoded microbeads as a standard.
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•A water-soluble tellurium-containing polymer based on a poly-l-lysine backbone and sulfated tellurophene pendant groups has been synthesized.•The tellurium-containing polymer was ...conjugated to three different antibodies via DBCO-azide click chemistry.•The performance of the conjugates was evaluated by suspension mass cytometry and gave mixed results.
Mass cytometry is a powerful analytical technique for high-dimensional single-cell analysis. In this technique, cells are stained with heavy isotope-tagged antibodies and are analyzed by an inductively coupled plasma time-of-flight mass spectrometer. While the current mass cytometer has more than 100 mass channels, only about 50 are used because reagents are only available for a fraction of the useful elements. Here we describe the synthesis of a tellurium-containing polymer based on poly-l-lysine and sulfated tellurophene. The polymer carried ca. 48 tellurophene units per chain and had a terminal azide group for antibody conjugation. While the polymer could be conjugated to antibodies, the resulting conjugates gave mixed results in mass cytometry immunoassays. For example, a goat anti-mouse (secondary) antibody and an anti-CD19 primary Ab labeled with polymers gave promising results in antibody titration experiments. However, an anti-CD20 Ab labeled with a 126Te-enriched polymer no longer recognized the antigen and showed significant non-specific binding in a 7-plex assay with human PBMCs.
Bead-based assays in flow cytometry are multiplexed analytical techniques that allow rapid and simultaneous detection and quantification of a large number of analytes from small volumes of samples. ...The development of corresponding bead-based assays in mass cytometry (MC) is highly desirable since it could increase the number of analytes detected in a single assay. The microbeads for these assays have to be labeled with metal isotopes for MC detection. One must also be able to functionalize the bead surface with affinity reagents to capture the analytes. Metal-encoded polystyrene microbeads prepared by multi-stage dispersion polymerization can produce effective isotopic signals in MC with relatively small bead-to-bead variations. However, functionalizing this microbead surface with bioaffinity agents remains challenging, possibly due to the interference of the steric-stabilizing PVP corona on the microbead surface. Here, we report a systematic investigation of a silica coating approach to coat Eu-encoded microbeads with thin silica shells, to functionalize the surface with amino groups, and to introduce bioaffinity agents. We examine the effect of silica shell roughness on the bioconjugation capacity and the effect of silica shell thickness on signal quality in MC measurements. To limit non-specific binding, we converted the amino groups on the microbead surface to carboxylic acid groups. Antibodies were effectively attached to microbead by first conjugating NeutrAvidin to the carboxyl-modified bead surface and then attaching biotinylated antibodies to the NeutrAvidin-modified bead surface. The antibody-modified microbeads can specifically capture antigens, which were marked with isotopic labels, and generate strong signals in MC. These are promising results for the development of bead-based assays in MC.
Abstract
Magnetic resonance (MR) angiography is one of the main diagnostic approaches for cardiac-cerebral vascular diseases. Nevertheless, the non-contrast-enhanced MR angiography suffers from its ...intrinsic problems derived from the blood flow-dependency, while the clinical Gd-chelating contrast agents are limited by their rapid vascular extravasation. Herein, we report a hypersensitive MR angiography strategy based on interlocking stratagem of zwitterionic Gd-chelate contrast agents (PAA-Gd). The longitudinal molar relaxivity of PAA-Gd was 4.6-times higher than that of individual Gd-chelates as well as appropriate blood half-life (73.8 min) and low immunogenicity, enabling sophisticated micro-vessels angiography with a resolution at the order of hundred micrometers. A series of animal models of cardiac-cerebrovascular diseases have been built for imaging studies on a 7.0 T MRI scanner, while the clinical translation potential of PAA-Gd has been evaluated on swine on a 3.0 T clinical MRI scanner. The current studies offer a promising strategy for precise diagnosis of vascular diseases.
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