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1.
Chem Rev ; 123(8): 4188-4236, 2023 Apr 26.
Article in English | MEDLINE | ID: mdl-37015056

ABSTRACT

Preceramic polymers (PCPs) are a group of specialty macromolecules that serve as precursors for generating inorganics, including ceramic carbides, nitrides, and borides. PCPs represent interesting synthetic challenges for chemists due to the elements incorporated into their structure. This group of polymers is also of interest to engineers as PCPs enable the processing of polymer-derived ceramic products including high-performance ceramic fibers and composites. These finished ceramic materials are of growing significance for applications that experience extreme operating environments (e.g., aerospace propulsion and high-speed atmospheric flight). This Review provides an overview of advances in the synthesis and postpolymerization modification of macromolecules forming nonoxide ceramics. These PCPs include polycarbosilanes, polysilanes, polysilazanes, and precursors for ultrahigh-temperature ceramics. Following our review of PCP synthetic chemistry, we provide examples of the application and processing of these polymers, including their use in fiber spinning, composite fabrication, and additive manufacturing. The principal objective of this Review is to provide a resource that bridges the disciplines of synthetic chemistry and ceramic engineering while providing both insights and inspiration for future collaborative work that will ultimately drive the PCP field forward.

2.
ACS Biomater Sci Eng ; 7(7): 3103-3113, 2021 07 12.
Article in English | MEDLINE | ID: mdl-34100582

ABSTRACT

Recent efforts have demonstrated that the morphology of ceramics can be manipulated to control both their deformation mechanism and mechanical performance. However, precise control of the ceramic nanostructure is still difficult to achieve. Biotemplating, leading to biomorphic materials, provides a facile route to manipulate the nanostructure of the resulting materials, and the use of melanin as a coating provides a new route to biotemplated materials. Melanin is underutilized for structural materials partly due to the cost of procuring it from natural sources and the inability to control the shape and sizes of melanin particles. Taking a combined synthetic biology and chemical synthesis approach, we report the melanization of Escherichia coli and its subsequent silanization and functionalization with preceramic polymers to make novel biomorphic silicon-based ceramic materials. Graft-to and graft-from reactions were used to append preceramic polymers to the melanin, followed by pyrolysis under argon. Samples were analyzed by FTIR, XRD, XPS, and TEM and found to retain the shape and size of the original cells with high fidelity. The homogeneity of coverage and yield of the resulting ceramic materials depended on the type of grafting reaction. This work provides a promising proof-of-concept that bacterial-templated ceramics can be readily made and opens a host of possibilities for further studies and applications.


Subject(s)
Melanins , Polymers , Ceramics , Silicon
3.
ACS Biomater Sci Eng ; 3(9): 2064-2075, 2017 Sep 11.
Article in English | MEDLINE | ID: mdl-33440560

ABSTRACT

Regenerated silk fibroin, a biopolymer derived from silkworm cocoons, is a versatile material that has been widely explored for a number of applications (e.g., drug delivery, tissue repair, biocompatible electronics substrates, and optics) due to its attractive biochemical properties and processability. Here, we report on the free-form printing of silk-based, 3D microstructures through multiphoton lithography. Utilizing multiphoton lithography in conjunction with specific photoinitiator chemistry and postprint cross-linking, a number of microarchitectures were achieved including self-supporting fibroin arches. Further, the straightforward production of high fidelity and biofunctional protein architectures was enabled through the printing of aqueous fibroin/immunoglobulin solutions.

4.
Small ; 11(29): 3539-44, 2015 Aug 05.
Article in English | MEDLINE | ID: mdl-25940859

ABSTRACT

Synthetic hemozoin crystals (ß-hematin) are assembled with aluminium nanoparticles (nAl) to create a nanomaterial composite that is highly energetic and reactive. The results here demonstrate that hemozoin rapidly oxidizes the nAl fuel to release large amounts of energy (+12.5 ± 2.4 kJ g(-1) ).


Subject(s)
Aluminum/chemistry , Biomimetic Materials/chemistry , Energy Transfer , Heme/chemistry , Metal Nanoparticles/chemistry , Nanoconjugates/chemistry , Crystallization/methods , Hot Temperature , Metal Nanoparticles/ultrastructure , Nanoconjugates/ultrastructure , Particle Size
5.
MRS Bull ; 40(12): 1089-1101, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26989295

ABSTRACT

Protein- and peptide-based structural biopolymers are abundant building blocks of biological systems. Either in their natural forms, such as collagen, silk or fibronectin, or as related synthetic materials they can be used in various technologies. An emerging area is that of biomimetic materials inspired by protein-based biopolymers, which are made up of small molecules rather than macromolecules and can therefore be described as supramolecular polymers. These materials are very useful in biomedical applications because of their ability to imitate the extracellular matrix both in architecture and their capacity to signal cells. This article describes important features of the natural extracellular matrix and highlight how these features are being incorporated into biomaterials composed of biopolymers and supramolecular polymers. We particularly focus on the structures, properties, and functions of collagen, fibronectin, silk, and the supramolecular polymers inspired by them as biomaterials for regenerative medicine.

7.
Biomacromolecules ; 14(10): 3509-14, 2013 Oct 14.
Article in English | MEDLINE | ID: mdl-23987229

ABSTRACT

Derived from Bombyx mori cocoons, regenerated silk fibroin (RSF) exhibits excellent biocompatibility, high toughness, and tailorable biodegradability. Additionally, RSF materials are flexible, optically clear, easily patterned with nanoscale features, and may be doped with a variety bioactive species. This unique combination of properties has led to increased interest in the use of RSF in sustainable and biocompatible electronic devices. In order to explore the applicability of this biopolymer to the development of future bioelectronics, the dielectric breakdown strength (Ebd) of RSF thin films was quantified as a function of protein conformation. The application of processing conditions that increased ß-sheet content (as determined by FTIR analysis) and produced films in the silk II structure resulted in RSF materials with improved Ebd with values reaching up to 400 V/µm.


Subject(s)
Fibroins/chemistry , Silk/chemistry , Tensile Strength , Animals , Bombyx , Fibroins/metabolism , Materials Testing , Particle Size , Protein Conformation , Silk/metabolism , Surface Properties
8.
J Mater Chem B ; 1(40): 5505-5514, 2013 Oct 28.
Article in English | MEDLINE | ID: mdl-32261258

ABSTRACT

The combination of appealing structural properties, biocompatibility, and the availability of renewable and inexpensive raw materials, make keratin-based materials attractive for a variety of applications. In this paper, we report on the antimicrobial functionalization of keratin-based materials, including wool cloth and regenerated cellulose/keratin composite films and nanofibers. The functionalization of these materials was accomplished utilizing a facile chlorination reaction that converts the nitrogen-bearing moieties of keratin into halamine compounds. Halamine-charged wool cloth exhibited rapid and potent bactericidal activity against several species of bacteria and induced up to a 5.3 log (i.e., 99.9995%) reduction in the colony forming units of Bacillus thuringiensis spores within 10 min. Keratin-containing composites were prepared by the spin coating and coaxial electrospinning of extracted/oxidized alpha-keratin and cellulose acetate (CA) solubilized in formic acid, followed by CA deacetylation. Regenerated cellulose/keratin materials chlorinated to display halamines were also effective in killing Escherichia coli and Staphylococcus aureus bacteria. Electrospun core/shell nanofibers engineered to maximize keratin-Cl surface area displayed higher activity against S. aureus than films composed of the same materials. The halamine-based antimicrobial functionalization methods demonstrated for keratin-based materials in this paper are anticipated to translate to other protein biopolymers of interest to the biomaterials community.

9.
Biomacromolecules ; 13(7): 2037-45, 2012 Jul 09.
Article in English | MEDLINE | ID: mdl-22651251

ABSTRACT

Organophosphates are some of the most acutely toxic compounds synthesized on an industrial scale, and organophosphorus hydrolase (OPH) has the ability to hydrolyze and inactivate a number of these chemicals. However, OPH activity is vulnerable to harsh environmental conditions that would accompany its practical utility in the field; a limitation that can also be extended to conditions required for incorporation of OPH into useful materials. Here we present evidence that entrapment of OPH in silk fibroin leads to stabilization of OPH activity under a variety of conditions that would otherwise reduce free enzyme activity, such as elevated temperature, UV light exposure and the presence of detergent. Silk fibroin entrapment of OPH also allowed for its dispersal into a polyurethane-based coating that retained organophosphate hydrolysis activity after formulation, application and drying. Together, the data presented here demonstrate the utility of silk fibroin entrapment for the protection of OPH activity under a variety of environmental conditions.


Subject(s)
Aryldialkylphosphatase/chemistry , Fibroins/chemistry , Polyurethanes/chemistry , Animals , Bombyx , Enzyme Stability , Hydrolysis , Insecticides/chemistry , Methyl Parathion/chemistry , Preservation, Biological , Sodium Dodecyl Sulfate/chemistry , Surface Properties , Temperature , Ultraviolet Rays
10.
ACS Appl Mater Interfaces ; 4(3): 1724-32, 2012 Mar.
Article in English | MEDLINE | ID: mdl-22352921

ABSTRACT

Bacterial spores, such as those of the Bacillus genus, are extremely resilient, being able to germinate into metabolically active cells after withstanding harsh environmental conditions or aggressive chemical treatments. The toughness of the bacterial spore in combination with the use of spores, such as those of Bacillus anthracis, as a biological warfare agent necessitates the development of new antimicrobial textiles. In this work, a route to the production of fabrics that kill bacterial spores and cells within minutes of exposure is described. Utilizing this facile process, unmodified silk cloth is reacted with a diluted bleach solution, rinsed with water, and dried. The chlorination of silk was explored under basic (pH 11) and slightly acidic (pH 5) conditions. Chloramine-silk textiles prepared in acidified bleach solutions were found to have superior breaking strength and higher oxidative Cl contents than those prepared under caustic conditions. Silk cloth chlorinated for ≥1 h at pH 5 was determined to induce >99.99996% reduction in the colony forming units of Escherichia coli, as well as Bacillus thuringiensis Al Hakam (B. anthracis simulant) spores and cells within 10 min of contact. The processing conditions presented for silk fabric in this study are highly expeditionary, allowing for the on-site production of protein-based antimicrobial materials from a variety of agriculturally produced feed-stocks.


Subject(s)
Anti-Bacterial Agents/pharmacology , Bacillus thuringiensis/drug effects , Halogenation/drug effects , Silk/chemistry , Textiles , Bacillus thuringiensis/cytology , Chloramines/chemistry , Chlorides/analysis , Escherichia coli/drug effects , Hydrogen-Ion Concentration/drug effects , Magnetic Resonance Spectroscopy , Microbial Sensitivity Tests , Oxidation-Reduction/drug effects , Photoelectron Spectroscopy , Spores, Bacterial/drug effects , Stress, Mechanical , Time Factors
12.
J Am Chem Soc ; 130(1): 4-5, 2008 Jan 09.
Article in English | MEDLINE | ID: mdl-18067293

ABSTRACT

A 12-mer peptide, identified through phage display biopanning, has been used for the first time to induce the rapid formation of ferroelectric (tetragonal) nanocrystalline BaTiO3 at room temperature from an aqueous salt precursor solution at near neutral pH. BaTiO3 is widely used in capacitors, thermistors, displays, and sensors owing to its attractive dielectric, ferroelectric, pyroelectric, optical, and electrochemical properties. Two 12-mer peptides (BT1 and BT2) were selected from a phage-displayed peptide library via binding to tetragonal BaTiO3 powder. While these peptides possessed various types of amino acids, 8 of the 12 amino acids were common to both peptides. Each of these peptides induced the formation of faceted nanoparticles (50-100 nm diameter) from an aqueous precursor solution. X-ray diffraction and selected area electron diffraction patterns obtained from these faceted nanoparticles were consistent with the BaTiO3 compound. Rietveld analyses of the X-ray diffraction patterns yielded good fits to tetragonal crystal structures, with the BaTiO3 formed in the presence of the BT2 peptide exhibiting the most tetragonal character. A coating of the latter BaTiO3 nanoparticles exhibited polarization hysteresis (a well-known characteristic of ferroelectric materials) at room temperature and a relative permittivity of 2200. Such rapid, peptide-induced precipitation at room temperature provides new opportunities for direct BaTiO3 formation on low-melting or reactive materials (e.g., plastics, cloths, bio-organics) and the low temperature integration of BaTiO3 into electronic devices (e.g., on silicon or flexible polymer substrates).


Subject(s)
Barium Compounds/chemical synthesis , Biotechnology/methods , Nanostructures , Oligopeptides/chemistry , Barium Compounds/chemistry , Crystallization , Hydrogen-Ion Concentration , Magnetics , Salts , Solutions , Temperature , Titanium
14.
Nature ; 446(7132): 172-5, 2007 Mar 08.
Article in English | MEDLINE | ID: mdl-17344850

ABSTRACT

The carbothermal reduction of silica into silicon requires the use of temperatures well above the silicon melting point (> or =2,000 degrees C). Solid silicon has recently been generated directly from silica at much lower temperatures (< or =850 degrees C) via electrochemical reduction in molten salts. However, the silicon products of such electrochemical reduction did not retain the microscale morphology of the starting silica reactants. Here we demonstrate a low-temperature (650 degrees C) magnesiothermic reduction process for converting three-dimensional nanostructured silica micro-assemblies into microporous nanocrystalline silicon replicas. The intricate nanostructured silica microshells (frustules) of diatoms (unicellular algae) were converted into co-continuous, nanocrystalline mixtures of silicon and magnesia by reaction with magnesium gas. Selective magnesia dissolution then yielded an interconnected network of silicon nanocrystals that retained the starting three-dimensional frustule morphology. The silicon replicas possessed a high specific surface area (>500 m(2) g(-1)), and contained a significant population of micropores (< or =20 A). The silicon replicas were photoluminescent, and exhibited rapid changes in impedance upon exposure to gaseous nitric oxide (suggesting a possible application in microscale gas sensing). This process enables the syntheses of microporous nanocrystalline silicon micro-assemblies with multifarious three-dimensional shapes inherited from biological or synthetic silica templates for sensor, electronic, optical or biomedical applications.


Subject(s)
Biomimetics/methods , Diatoms/chemistry , Silicon/chemistry , Magnesium/chemistry , Magnesium Oxide/chemistry , Models, Chemical , Nanostructures/chemistry , Oxidation-Reduction , Porosity , Temperature
17.
Chem Commun (Camb) ; (15): 1776-7, 2004 Aug 07.
Article in English | MEDLINE | ID: mdl-15278181

ABSTRACT

Peptides that promote the rapid, room-temperature precipitation of amorphous germania nanoparticle networks from solution have been identified via use of a combinatorial peptide display library.

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