RESUMO
Self-assembled biomaterials are an important class of materials that can be injected and formed in situ. However, they often are not able to meet the mechanical properties necessary for many biological applications, losing mechanical properties at low strains. We synthesized hybrid hydrogels consisting of a poly(γ-glutamic acid) polymer network physically cross-linked via grafted self-assembling ß-sheet peptides to provide non-covalent cross-linking through ß-sheet assembly, reinforced with a polymer backbone to improve strain stability. By altering the ß-sheet peptide graft density and concentration, we can tailor the mechanical properties of the hydrogels over an order of magnitude range of 10-200 kPa, which is in the region of many soft tissues. Also, due to the ability of the non-covalent ß-sheet cross-links to reassemble, the hydrogels can self-heal after being strained to failure, in most cases recovering all of their original storage moduli. Using a combination of spectroscopic techniques, we were able to probe the secondary structure of the materials and verify the presence of ß-sheets within the hybrid hydrogels. Since the polymer backbone requires less than a 15% functionalization of its repeating units with ß-sheet peptides to form a hydrogel, it can easily be modified further to incorporate specific biological epitopes. This self-healing polymer-ß-sheet peptide hybrid hydrogel with tailorable mechanical properties is a promising platform for future tissue-engineering scaffolds and biomedical applications.
Assuntos
Hidrogéis/síntese química , Peptídeos/química , Ácido Poliglutâmico/análogos & derivados , Hidrogéis/química , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Ácido Poliglutâmico/química , Estrutura Secundária de ProteínaRESUMO
The judicious compositional and structural design of a branched co-polymeric surfactant allows for the production of highly stable oil in water emulsion droplets with reversible electrostatic aggregation behaviour.
RESUMO
Sol-gel hybrids are inorganic/organic co-networks with nanoscale interactions between the components leading to unique synergistic mechanical properties, which can be tailored, via a selection of the organic moiety. Methacrylate based polymers present several benefits for class II hybrids (which exhibit formal covalent bonding between the networks) as they introduce great versatility and can be designed with a variety of chemical side-groups, structures and morphologies. In this study, the effect of high cross-linking density polymers on the structure-property relationships of hybrids generated using poly(3-trimethoxysilylpropyl methacrylate) (pTMSPMA) and tetraethyl orthosilicate (TEOS) was investigated. The complexity and fine scale of the co-network interactions requires the development of new analytical methods to understand how network evolution dictates the wide-ranging mechanical properties. Within this work we developed data manipulation techniques of acoustic-AFM and solid state NMR output that provide new approaches to understand the influence of the network structure on the macroscopic elasticity. The concentration of pTMSPMA in the silica sol affected the gelation time, ranging from 2 h for a hybrid made with 75 wt% inorganic with pTMSPMA at 2.5 kDa, to 1 minute for pTMSPMA with molecular weight of 30 kDa without any TEOS. A new mechanism of gelation was proposed based on the different morphologies derived by AC-AFM observations. We established that the volumetric density of bridging oxygen bonds is an important parameter in structure/property relationships in SiO2 hybrids and developed a method for determining it from solid state NMR data. The variation in the elasticity of pTMSPMA/SiO2 hybrids originated from pTMSPMA acting as a molecular spacer, thus decreasing the volumetric density of bridging oxygen bonds as the inorganic to organic ratio decreased.
Assuntos
Géis/química , Metacrilatos/química , Dióxido de Silício/química , Difusão Dinâmica da Luz , Módulo de Elasticidade , Espectroscopia de Ressonância Magnética , Microscopia de Força Atômica , Transição de Fase , Polímeros/química , TermogravimetriaRESUMO
We report on a versatile and time-efficient method to fabricate calcium phosphate (CaP) microcapsules by utilizing oil-in-water emulsion droplets stabilized with synthetic branched copolymer (BCP) as templates. The BCP was designed to provide a suitable architecture and functionality to produce stable emulsion droplets, and to permit the mineralization of CaP at the surface of the oil droplet when incubated in a solution containing calcium and phosphate ions. The CaP shells of the microcapsules were established to be calcium deficient hydroxyapatite with incorporated chlorine and carbonate species. These capsule walls were made fluorescent by decoration with a fluorescein-bisphosphonate conjugate.
RESUMO
Particle get-together: Surface functionalization with a branched copolymer surfactant is used to create responsive inorganic particles that can self-assemble in complex structures. The assembly process is triggered by a pH switch that reversibly activates multiple hydrogen bonds between ceramic particles (see picture; yellow) and soft templates (n-decane; green).
Assuntos
Óxido de Alumínio/química , Polímeros/química , Tensoativos/química , Ligação de Hidrogênio , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
Although several strategies are now available to produce functional microcompartments analogous to primitive cell-like structures, little progress has been made in generating protocell constructs with self-controlled membrane permeability. Here we describe the preparation of water-dispersible colloidosomes based on silica nanoparticles and delineated by a continuous semipermeable inorganic membrane capable of self-activated, electrostatically gated permeability. We use crosslinking and covalent grafting of a pH-responsive copolymer to generate an ultrathin elastic membrane that exhibits selective release and uptake of small molecules. This behaviour, which depends on the charge of the copolymer coronal layer, serves to trigger enzymatic dephosphorylation reactions specifically within the protocell aqueous interior. This system represents a step towards the design and construction of alternative types of artificial chemical cells and protocell models based on spontaneous processes of inorganic self-organization.
Assuntos
Células Artificiais/química , Células Artificiais/metabolismo , Permeabilidade da Membrana Celular , Compostos Inorgânicos/química , Eletricidade Estática , Alcanos/química , Emulsões , Nanopartículas/química , Tamanho da Partícula , Fosforilação , Polímeros , Silanos/química , Dióxido de Silício/química , Água/químicaRESUMO
Poly[2-(methacryloyloxy)ethylphosphorylcholine]-coated SPIONs were prepared through ATRP and amidation coupling reactions. The coated SPIONs exhibited high stability and re-dispersability in phosphate buffered saline and uptake in a stem cell line, with high T(2) relaxivity.
Assuntos
Compostos Férricos/química , Compostos Férricos/metabolismo , Metacrilatos/química , Nanopartículas/química , Fosforilcolina/análogos & derivados , Células-Tronco/metabolismo , Animais , Soluções Tampão , Técnicas de Química Sintética , Coloides , Estabilidade de Medicamentos , Compostos Férricos/síntese química , Camundongos , Fosforilcolina/química , Ácidos Polimetacrílicos , Coloração e RotulagemRESUMO
Multi-purpose amphiphilic branched copolymer surfactants can be used to simultaneously stabilise and cross-link emulsion droplets to produce encapsulated spheres and hollow capsules.
Assuntos
Polímeros/síntese química , Cápsulas/síntese química , Cápsulas/química , Emulsões/química , Tamanho da Partícula , Polímeros/química , Propriedades de Superfície , Tensoativos/síntese química , Tensoativos/químicaRESUMO
We describe the first example of a tri-phasic oil-in-water-in-air 'dry water emulsion'. The method combines highly stable oil-in-water emulsions prepared using branched copolymer surfactants, with aqueous droplet encapsulation using 'dry water' technology.
Assuntos
Composição de Medicamentos , Emulsões/química , Óleos/química , Água/química , Ar , Concentração de Íons de Hidrogênio , Polímeros/química , Dióxido de Silício/química , Tensoativos/químicaRESUMO
Subtle changes in copolymer surfactant architecture and chain-end functionality can induce diverse behaviours in pH-responsive branched copolymer-stabilized emulsions.
RESUMO
Making and breaking: Stable, functional micrometer-sized emulsion droplets can be assembled into various complex macroscopic liquid structures (see picture). The hierarchical assembly process is mediated by interactions between polymeric surfactant molecules located on the droplet surfaces. These interdroplet interactions are reversible, therefore these "engineered emulsions" can be readily disassembled by using a simple pH switch.
RESUMO
We describe a new one-pot, single-step route for the preparation of pH-responsive branched polymer nanoparticles. These polymers, which are based on the pH-responsive monomer 2-(diethylamino)ethyl methacrylate (DEA) and hydrophilic macromonomer poly(ethyleneglycol) methacrylate (PEGMA), are synthesised using a modified conventional free-radical polymerisation. Consequently, their preparation is generic, scaleable and tolerant of functionality. In aqueous solution the branched copolymers form core-shell structures at basic pH and on reducing the solution pH they become hydrated and swell, displaying similar characteristics to those of pH-responsive shell cross-linked micelles and microgels. We demonstrate good control over the hydrodynamic particle size, polymer chain-end, and the uptake and release of a model hydrophobe and also the ability to tune the apparent pKa of the DEA residues by varying the degree of branching. These results augur well for commercially viable tunable release applications.
RESUMO
The use of new shell cross-linked micelles as pH-responsive particulate emulsifiers is described for the first time. 1-Undecanol-in-water emulsions of 18 mum diameter are formed at pH 8, whereas complete demulsification occurs at pH 2.