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1.
Biomacromolecules ; 25(2): 715-728, 2024 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-38271957

RESUMO

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil-water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications.


Assuntos
Cistamina , Nanopartículas , Emulsões/química , Óleo de Semente do Linho , Celulose/química , Nanopartículas/química , Água/química
2.
J Am Chem Soc ; 144(2): 951-962, 2022 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-34985896

RESUMO

Living crystallization-driven self-assembly of polymeric and molecular amphiphiles is of growing interest as a seeded growth route to uniform 1D, 2D, and more complex micellar nanoparticles with controlled dimensions and a range of potential applications. Although most studies have been performed using colloidally stable seeds in bulk solution, growth of block copolymer (BCP) nanofibers from seeds confined to a surface is attracting increased attention. Herein, we have used atomic force microscopy (AFM) to undertake detailed studies of the growth of BCP nanofibers from immobilized seeds located on a Si surface. Through initial ex situ AFM studies and in situ AFM video analysis in solution, we determined that growth occurred in four stages, whereby an initial surface-bound growth regime transitions to surface-limited growth. As the nanofiber length increases, surface influence is diminished as the newly grown micelle segment is no longer bound to the Si substrate. Finally, a surface-independent regime occurs where nanofiber growth continues into bulk solution. In addition to the anticipated nanofiber elongation, our studies revealed occasional examples of AFM tip-induced core fragmentation. In these cases, the termini of the newly formed fragments were also active to further growth. Furthermore, unidirectional growth was detected in cases where the seed was oriented at a significant angle with respect to the surface, thereby restricting unimer access to one terminus.

3.
J Am Chem Soc ; 144(43): 19799-19812, 2022 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-36260789

RESUMO

Micelleplexes show great promise as effective polymeric delivery systems for nucleic acids. Although studies have shown that spherical micelleplexes can exhibit superior cellular transfection to polyplexes, to date there has been no report on the effects of micelleplex morphology on cellular transfection. In this work, we prepared precision, length-tunable poly(fluorenetrimethylenecarbonate)-b-poly(2-(dimethylamino)ethyl methacrylate) (PFTMC16-b-PDMAEMA131) nanofiber micelleplexes and compared their properties and transfection activity to those of the equivalent nanosphere micelleplexes and polyplexes. We studied the DNA complexation process in detail via a range of techniques including cryo-transmission electron microscopy, atomic force microscopy, dynamic light scattering, and ζ-potential measurements, thereby examining how nanofiber micelleplexes form, as well the key differences that exist compared to nanosphere micelleplexes and polyplexes in terms of DNA loading and colloidal stability. The effects of particle morphology and nanofiber length on the transfection and cell viability of U-87 MG glioblastoma cells with a luciferase plasmid were explored, revealing that short nanofiber micelleplexes (length < ca. 100 nm) were the most effective delivery vehicle examined, outperforming nanosphere micelleplexes, polyplexes, and longer nanofiber micelleplexes as well as the Lipofectamine 2000 control. This study highlights the potential importance of 1D micelleplex morphologies for achieving optimal transfection activity and provides a fundamental platform for the future development of more effective polymeric nucleic acid delivery vehicles.


Assuntos
Nanofibras , Ácidos Nucleicos , Micelas , Transfecção , Polímeros , DNA
4.
J Am Chem Soc ; 143(15): 5805-5814, 2021 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-33851530

RESUMO

Although micelles derived from the solution self-assembly of amphiphilic molecules and polymers have been prepared with a wide variety of shapes, examples with well-defined branched structures have remained elusive. We describe a divergent, directed self-assembly approach to low dispersity dendritic micelles with a high degree of structural perfection and tailorable branch numbers and generations. We use block copolymer amphiphiles as precursors and a crystallization-driven seeded growth approach whereby the termini of fiber-like micelles function as branching sites. Different dendrimeric generations are accessible by adjusting the ratio of added unimers to pre-existing seed micelles where the branch positions are determined by the reduced coronal chain grafting density on the surface of the micelle crystalline core. We demonstrate the spatially defined decoration of the assemblies with emissive nanoparticles and utility of the resulting hybrids as fluorescent sensors for anions where the dendritic architecture enables ultrahigh sensitivity.


Assuntos
Dendrímeros/química , Micelas , Ânions/química , Cristalização , Compostos Ferrosos/química , Limite de Detecção , Microscopia de Força Atômica , Polivinil/química , Pontos Quânticos/química , Silanos/química , Espectrometria de Fluorescência , Sulfetos/análise , Propriedades de Superfície
5.
Small ; 17(10): e2100472, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33590708

RESUMO

The design and assembly of peptide-based materials has advanced considerably, leading to a variety of fibrous, sheet, and nanoparticle structures. A remaining challenge is to account for and control different possible supramolecular outcomes accessible to the same or similar peptide building blocks. Here a de novo peptide system is presented that forms nanoparticles or sheets depending on the strategic placement of a "disulfide pin" between two elements of secondary structure that drive self-assembly. Specifically, homodimerizing and homotrimerizing de novo coiled-coil α-helices are joined with a flexible linker to generate a series of linear peptides. The helices are pinned back-to-back, constraining them as hairpins by a disulfide bond placed either proximal or distal to the linker. Computational modeling indicates, and advanced microscopy shows, that the proximally pinned hairpins self-assemble into nanoparticles, whereas the distally pinned constructs form sheets. These peptides can be made synthetically or recombinantly to allow both chemical modifications and the introduction of whole protein cargoes as required.


Assuntos
Nanopartículas , Peptídeos , Fenômenos Biofísicos , Estrutura Secundária de Proteína , Proteínas
6.
Chemistry ; 27(4): 1374-1382, 2021 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-32990374

RESUMO

Understanding the fine details of the self-assembly of building blocks into complex hierarchical structures represents a major challenge en route to the design and preparation of soft-matter materials with specific properties. Enzymatically synthesised cellodextrins are known to have limited water solubility beyond DP9, a point at which they self-assemble into particles resembling the antiparallel cellulose II crystalline packing. We have prepared and characterised a series of site-selectively fluorinated cellodextrins with different degrees of fluorination and substitution patterns by chemoenzymatic synthesis. Bearing in mind the potential disruption of the hydrogen-bond network of cellulose II, we have prepared and characterised a multiply 6-fluorinated cellodextrin. In addition, a series of single site-selectively fluorinated cellodextrins was synthesised to assess the structural impact upon the addition of one fluorine atom per chain. The structural characterisation of these materials at different length scales, combining advanced NMR spectroscopy and microscopy methods, showed that a 6-fluorinated donor substrate yielded multiply 6-fluorinated cellodextrin chains that assembled into particles presenting morphological and crystallinity features, and intermolecular interactions, that are unprecedented for cellulose-like materials.

7.
Langmuir ; 37(30): 9215-9221, 2021 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-34297578

RESUMO

The design of new functional materials and devices substantially relies on self-assembly of hierarchical structures. Formation of 2D platelets is known in the enzymatic synthesis of cellulose-like polymers. Here we demonstrate the feasibility of postsynthesis assembly of novel fluorinated cellodextrins. Highly ordered 2D structures of large lateral dimensions, unattainable in the polymerization process, can be formed because of postsynthesis assembly of the cellodextrins. These cellodextrins were also involved in coassembly with cellulose nanocrystals (CNCs) leading to hybrid systems. The hybrid architectures obtained depend on the content of fluorine atoms in the fluorinated cellodextrins. Monofluorinated cellodextrins coassemble with CNCs into a nanoweb, while multifluorinated cellodextrins assemble around the CNCs.


Assuntos
Celulose , Nanopartículas , Celulose/análogos & derivados , Dextrinas , Polímeros
8.
Langmuir ; 37(21): 6521-6532, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34015220

RESUMO

Understanding the nanostructure and nanomechanical properties of surface layers of erucamide, in particular the molecular orientation of the outermost layer, is important to its widespread use as a slip additive in polymer materials. Extending our recent observations of nanomorphologies of erucamide layers on a hydrophilic silica substrate, here we evaluate its nanostructure on a more hydrophobic polypropylene surface. Atomic force microscopy (AFM) imaging revealed the molecular packing, thickness, and surface coverage of the erucamide layers, while peak force quantitative nanomechanical mapping (QNM) showed that erucamide reduced the adhesive response on polypropylene. Synchrotron X-ray reflectivity (XRR) was used to probe the out-of-plane structure of the surface layers. Static contact angle measurements further corroborated on the resulting wettability, also demonstrating the efficacy of erucamide physisorption in facilitating control over polypropylene surface wetting. The results show the formation of erucamide monolayers, bilayers and multilayers, depending on the concentration in the spin-cast solution. Correlation of AFM, XRR and wettability results consistently points to the molecular orientation in the outermost layer, i.e. with the erucamide tails pointing outward for the surface nanostructures with different morphologies (i.e., bilayers and multilayers). Rare occurrence of monolayers with exposed hydrophilic head groups were observed only at the lowest erucamide concentration. Compared with our previous observations on the hydrophilic surface, the erucamide surface coverage was much higher on the more hydrophobic propylene surface at similar erucamide concentrations in the spin-cast solution. Furthermore, the structure, molecular orientation and nanomechanical properties of the spin-cast erucamide multilayers atop polypropylene were also similar to those on industrially relevant polypropylene fibers coated with erucamide via blooming. These findings shed light on the nanostructural features of the erucamide surface layer underpinning its nanomechanical properties, relevant to many applications in which erucamide is commonly used as a slip additive.

9.
Sensors (Basel) ; 21(9)2021 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-33925843

RESUMO

The increase in capabilities of Scanning Probe Microscopy (SPM) has resulted in a parallel increase in complexity that limits the use of this technique outside of specialised research laboratories. SPM automation could substantially expand its application domain, improve reproducibility and increase throughput. Here, we present a bottom-up design in which the combination of positioning stages, orientation, and detection of the probe produces an SPM design compatible with full automation. The resulting probe microscope achieves sub-femtonewton force sensitivity whilst preserving low mechanical drift (2.0±0.2 nm/min in-plane and 1.0±0.1 nm/min vertically). The additional integration of total internal reflection microscopy, and the straightforward operations in liquid, make this instrument configuration particularly attractive to future biomedical applications.


Assuntos
Microscopia de Varredura por Sonda , Microscopia , Fenômenos Mecânicos , Reprodutibilidade dos Testes
10.
J Am Chem Soc ; 142(31): 13469-13480, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32594739

RESUMO

The creation of organic heterojunctions from conjugated polymers on the nanoscale has attracted recent attention as a consequence of their considerable potential in optoelectronic devices. Herein, we report proof-of-concept results on a versatile synthetic strategy to access various linearly segmented nanowire heterojunctions with controlled dimensions using the seeded growth "living crystallization-driven self-assembly" method followed by a secondary crystallization step. Specifically, we describe the creation of coaxial and also segmented coaxial B-A-B and A-B-A nanowires with a solvophilic poly(ethylene glycol) (PEG) corona, an inner crystalline core that consists of poly(di-n-hexylfluorene) (PDHF), which functions as a donor, and an outer crystalline core of poly(3-(2'-ethylhexyl)thiophene) (P3EHT), which acts as an acceptor. The latter is present either along the entire nanowire or solely in the central or terminal segments. These assemblies were created by seeded growth of two types of π-conjugated polymeric building blocks, the triblock copolymer PDHF-b-P3EHT-b-PEG and the diblock copolymer PDHF-b-PEG, by using fiber-like seeds derived from either material. The nanowires with both solid-state donor and acceptor blocks exhibit Förster resonance energy transfer (FRET) from the PDHF inner core to the P3EHT outer core which was characterized by fluorescence spectroscopy and laser confocal scanning fluorescence microscopy (LCSM). The FRET in the solid-state coaxial heterojunctions with an inner PDHF core and an outer P3EHT core was enhanced relative to the directly analogous system in which the P3EHT block was solvated.


Assuntos
Nanofios/química , Polímeros/síntese química , Cristalização , Estrutura Molecular , Tamanho da Partícula , Polímeros/química , Propriedades de Superfície
11.
J Am Chem Soc ; 141(48): 19088-19098, 2019 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-31657915

RESUMO

Fiber-like micelles based on biodegradable and biocompatible polymers exhibit considerable promise for applications in nanomedicine, but until recently no convenient methods were available to prepare samples with uniform and controllable dimensions and spatial control of functionality. "Living" crystallization-driven self-assembly (CDSA) is a seeded growth method of growing importance for the preparation of uniform 1D and 2D core-shell nanoparticles from a range of crystallizable polymeric amphiphiles. However, in the case of poly(l-lactide) (PLLA), arguably the most widely utilized biodegradable polymer as the crystallizable core-forming block, the controlled formation of uniform fiber-like structures over a substantial range of lengths by "living" CDSA has been a major challenge. Herein, we demonstrate that via simple modulation of the solvent conditions via the addition of trifluoroethanol (TFE), DMSO, DMF and acetone, uniform fiber-like nanoparticles from PLLA diblock copolymers with controlled lengths up to 1 µm can be prepared. The probable mechanism involves improved unimer solvation by a reduction of hydrogen bonding interactions among PLLA chains. We provide evidence that this minimizes undesirable unimer aggregation which otherwise favors self-nucleation that competes with epitaxial crystallization from seed termini. This approach has also allowed the formation of well-defined segmented block comicelles with PLLA cores via the sequential seeded-growth of PLLA block copolymers with different corona-forming blocks.


Assuntos
Resinas Acrílicas/química , Micelas , Nanopartículas/química , Poliésteres/química , Cristalização , Ligação de Hidrogênio , Nanopartículas/ultraestrutura , Tamanho da Partícula , Solubilidade , Solventes
12.
Nat Mater ; 17(12): 1145-1153, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30297813

RESUMO

Although several new types of synthetic cell-like entities are now available, their structural integration into spatially interlinked prototissues that communicate and display coordinated functions remains a considerable challenge. Here we describe the programmed assembly of synthetic prototissue constructs based on the bio-orthogonal adhesion of a spatially confined binary community of protein-polymer protocells, termed proteinosomes. The thermoresponsive properties of the interlinked proteinosomes are used collectively to generate prototissue spheroids capable of reversible contractions that can be enzymatically modulated and exploited for mechanochemical transduction. Overall, our methodology opens up a route to the fabrication of artificial tissue-like materials capable of collective behaviours, and addresses important emerging challenges in bottom-up synthetic biology and bioinspired engineering.


Assuntos
Células Artificiais , Temperatura , Resinas Acrílicas/química , Animais , Bovinos , Mecanotransdução Celular , Ácidos Polimetacrílicos/química , Soroalbumina Bovina/química , Biologia Sintética
13.
J Am Chem Soc ; 140(49): 17127-17140, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30392357

RESUMO

Fiber-like block copolymer (BCP) micelles offer considerable potential for a variety of applications; however, uniform samples of controlled length and with spatially tailored chemistry have not been accessible. Recently, a seeded growth method, termed "living" crystallization-driven self-assembly (CDSA), has been developed to allow the formation of 1D micelles and block comicelles of precisely controlled dimensions from BCPs with a crystallizable segment. An expansion of the range of core-forming blocks that participate in living CDSA is necessary for this technique to be compatible with a broad range of applications. Few examples currently exist of well-defined, water-dispersible BCP micelles prepared using this approach, especially from biocompatible and biodegradable polymers. Herein, we demonstrate that BCPs containing a crystallizable polycarbonate, poly(spiro[fluorene-9,5'-[1,3]-dioxan]-2'-one) (PFTMC), can readily undergo living CDSA processes. PFTMC- b-poly(ethylene glycol) (PEG) BCPs with PFTMC:PEG block ratios of 1:11 and 1:25 were shown to undergo living CDSA to form near monodisperse fiber-like micelles of precisely controlled lengths of up to ∼1.6 µm. Detailed structural characterization of these micelles by TEM, AFM, SAXS, and WAXS revealed that they comprise a crystalline, chain-folded PFTMC core with a rectangular cross-section that is surrounded by a solvent swollen PEG corona. PFTMC- b-PEG fiber-like micelles were shown to be dispersible in water to give colloidally stable solutions. This allowed an assessment of the toxicity of these structures toward WI-38 and HeLa cells. From these experiments, we observed no discernible cytotoxicity from a sample of 119 nm fiber-like micelles to either healthy (WI-38) or cancerous (HeLa) cell types. The living CDSA process was extended to PFTMC- b-poly(2-vinylpyridine) (P2VP), and addition of this BCP to PFTMC- b-PEG seed micelles led to the formation of well-defined segmented fibers with spatially localized coronal chemistries.

14.
J Am Chem Soc ; 140(23): 7222-7231, 2018 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-29847112

RESUMO

Chiral polymers are ubiquitous in nature, and the self-assembly of chiral materials is a field of widespread interest. In this paper, we describe the formation of chiral metallopolymers based on poly(cobaltoceniumethylene) ([PCE] n+), which have been prepared through oxidation of poly(cobaltocenylethylene) (PCE) in the presence of enantiopure N-acyl-amino-acid-derived anionic surfactants, such as N-palmitoyl-l-alanine (C16-l-Ala) and N-palmitoyl-d-alanine (C16-d-Ala). It is postulated that the resulting metallopolymer complexes [PCE][C16-l/d-Ala] n contain close ionic contacts, and exhibit chirality through the axially chiral ethylenic CH2-CH2 bridges, leading to interaction of the chromophoric [CoCp2]+ units through chiral space. The steric influence of the long palmitoyl (C16) surfactant tail is key for the transmission of chirality to the polymer, and results in a brushlike amphiphilic macromolecular structure that also affords solubility in polar organic solvents (e.g., EtOH, THF). Upon dialysis of these solutions into water, the hydrophobic palmitoyl surfactant substituents aggregate and the complex assembles into superhelical ribbons with identifiable "handedness", indicating the transmission of chirality from the molecular surfactant to the micrometer length scale, via the macromolecular complex.

15.
Nat Mater ; 16(4): 481-488, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28068313

RESUMO

The creation of shaped, uniform and colloidally stable two-dimensional (2D) assemblies by bottom-up methods represents a challenge of widespread current interest for a variety of applications. Herein, we describe the utilization of surface charge to stabilize self-assembled planar structures that are formed from crystallizable polymer precursors by a seeded growth approach. Addition of crystallizable homopolymers with charged end-groups to seeds generated by the sonication of block copolymer micelles with crystalline cores yields uniform platelet micelles with controlled dimensions. Significantly, the seeded growth approach is characterized by a morphological memory effect whereby the origin of the seed, which can involve a quasi-hexagonal or rectangular 2D platelet precursor, dictates the observed 2D platelet shape. This new strategy is illustrated using two different polymer systems, and opens the door to the construction of 2D hierarchical structures with broad utility.

16.
Chemistry ; 24(58): 15556-15565, 2018 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-30047561

RESUMO

The controlled solution self-assembly of an amphiphilic perylene diimide (PDI), with a hydrophobic perylene core and hydrophilic imide substituents with polydisperse oligo(ethylene glycol) (OEG) tethers is presented. It was possible, by a seeded-growth mechanism, to form colloidally stable, one-dimensional fibres with controllable lengths (from 400 to 1700 nm) and low dispersities (1.19-1.29) via a living supramolecular polymerisation process. Under the solvent conditions used, it was found that molecularly dissolved material (unimer) was present in samples of the fibre-like supramolecular assemblies. The free unimer may be present in a conformationally derived kinetically trapped state and/or may represent a more soluble PDI fraction with longer hydrophilic tethers. Significantly, it was also possible to form segmented supramolecular block copolymers by the addition of PDI unimer to chemically distinct PDI seeds, yielding fibres with controlled lengths. These results represent a significant advance in the ability to form PDI-based supramolecular polymers with precisely controlled lengths and architectures.

17.
Biochim Biophys Acta ; 1857(12): 1829-1839, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27614060

RESUMO

A challenge associated with the utilisation of bioenergetic proteins in new, synthetic energy transducing systems is achieving efficient and predictable self-assembly of individual components, both natural and man-made, into a functioning macromolecular system. Despite progress with water-soluble proteins, the challenge of programming self-assembly of integral membrane proteins into non-native macromolecular architectures remains largely unexplored. In this work it is shown that the assembly of dimers, trimers or tetramers of the naturally monomeric purple bacterial reaction centre can be directed by augmentation with an α-helical peptide that self-associates into extra-membrane coiled-coil bundle. Despite this induced oligomerisation the assembled reaction centres displayed normal spectroscopic properties, implying preserved structural and functional integrity. Mixing of two reaction centres modified with mutually complementary α-helical peptides enabled the assembly of heterodimers in vitro, pointing to a generic strategy for assembling hetero-oligomeric complexes from diverse modified or synthetic components. Addition of two coiled-coil peptides per reaction centre monomer was also tolerated despite the challenge presented to the pigment-protein assembly machinery of introducing multiple self-associating sequences. These findings point to a generalised approach where oligomers or longer range assemblies of multiple light harvesting and/or redox proteins can be constructed in a manner that can be genetically-encoded, enabling the construction of new, designed bioenergetic systems in vivo or in vitro.


Assuntos
Proteínas de Bactérias/metabolismo , Metabolismo Energético , Complexos de Proteínas Captadores de Luz/metabolismo , Fotossíntese , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteobactérias/metabolismo , Adaptação Fisiológica , Proteínas de Bactérias/química , Proteínas de Bactérias/efeitos da radiação , Metabolismo Energético/efeitos da radiação , Cinética , Luz , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/efeitos da radiação , Simulação de Dinâmica Molecular , Fotossíntese/efeitos da radiação , Complexo de Proteínas do Centro de Reação Fotossintética/química , Complexo de Proteínas do Centro de Reação Fotossintética/efeitos da radiação , Conformação Proteica em alfa-Hélice , Multimerização Proteica , Proteobactérias/efeitos da radiação , Relação Estrutura-Atividade
18.
J Am Chem Soc ; 139(27): 9221-9228, 2017 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-28557444

RESUMO

Poly(l-lactide) (PLLA)-based nanoparticles have attracted much attention with respect to applications in drug delivery and nanomedicine as a result of their biocompatibility and biodegradability. Nevertheless, the ability to prepare PLLA assemblies with well-defined shape and dimensions is limited and represents a key challenge. Herein we report access to a series of monodisperse complex and hierarchical colloidally stable 2D structures based on PLLA cores using the seeded growth, "living-crystallization-driven self-assembly" method. Specifically, we describe the formation of diamond-shaped platelet micelles and concentric "patchy" block co-micelles by using seeds of the charge-terminated homopolymer PLLA24[PPh2Me]I to initiate the sequential growth of either additional PLLA24[PPh2Me]I or a crystallizable blend of the latter with the block copolymer PLLA42-b-P2VP240, respectively. The epitaxial nature of the growth processes used for the creation of the 2D block co-micelles was confirmed by selected area electron diffraction analysis. Cross-linking of the P2VP corona of the peripheral block in the 2D block co-micelles using Pt nanoparticles followed by dissolution of the interior region in good solvent for PLLA led to the formation of novel, hollow diamond-shaped assemblies. We also demonstrate that, in contrast to the aforementioned results, seeded growth of the unsymmetrical PLLA BCPs PLLA42-b-P2VP240 or PLLA20-b-PAGE80 alone from 2D platelets leads to the formation of diamond-fiber hybrid structures.


Assuntos
Nanopartículas/química , Poliésteres/síntese química , Cristalização , Micelas , Conformação Molecular , Tamanho da Partícula , Poliésteres/química , Propriedades de Superfície
19.
J Am Chem Soc ; 139(12): 4409-4417, 2017 03 29.
Artigo em Inglês | MEDLINE | ID: mdl-28211270

RESUMO

Rectangular platelets formed by the self-assembly of block copolymers in selective solvents are of interest for a range of applications. Recently, we showed that the seeded growth of crystallizable blends of a block copolymer and homopolymer yields well-defined, low area dispersity examples of these two-dimensional (2D) structures. The key feature was the use of the same crystallizable polymer segment in the seed and blend components to enable an efficient homoepitaxial growth process. Herein we demonstrate that this 2D crystallization-driven self-assembly approach can be extended to heteroepitaxial growth by the use of different crystallizable polymers with compatible crystal structures. This allows the formation of well-defined "patchy" rectangular platelets and platelet block comicelles with different core chemistries. The use of scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy provided key information on the spatial location of the components in the resulting assemblies and thereby valuable insight into the 2D heteroepitaxial growth process.

20.
J Am Chem Soc ; 138(39): 12902-12912, 2016 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-27552126

RESUMO

Hydrogen bonds are among the most common interactions used by nature for the creation of hierarchical structures from smaller building blocks. Herein, we describe an in-depth study of the hierarchical assembly of cylindrical block comicelles with a crystallizable poly(ferrocenyldimethylsilane) (PFS) core via H-bonding interactions to form complex supermicellar structures. Well-defined block comicelles bearing H-bond donor (HD) segments (M(PFS-b-PMVSOH)), or H-bond acceptor (HA) segments (M(PFS-b-P2VP)), and non-interacting (N) segments (M(PFS-b-PtBA)) were created by the living crystallization-driven self-assembly (CDSA) method [PMVSOH = hydroxyl-functionalized poly(methylvinylsiloxane), P2VP = poly(2-vinylpyridine), PtBA = poly(tert-butyl acrylate), M = micelle segment]. Due to the control provided by the living CDSA approach, both the block comicelles and the individual segments were virtually monodisperse in length, which facilitated their predictable hierarchical assembly into higher-level structures. Two cases were investigated in detail: first, the interaction of N-HA-N triblock comicelles with the HD homopolymer PMVSOH, and second, the interaction of N-HD-N triblock comicelles with very short HA cylinders (seeds). By manipulation of several factors, namely coronal steric effects (via the PtBA corona chain) and attractive interaction strength (via the H-bonding interaction between P2VP and PMVSOH), the aggregation of the triblock comicelles could be controlled, and well-defined multi-micrometer-size structures such as "shish-kebab"-shaped supermicelles were prepared. The ability of the seeds adsorbed on the block comicelles to function as initiators for living CDSA to generate fence-like "shish-kebab" superstructures was also explored.

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