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ABSTRACT: The ability to engineer particles has the potential to shift the paradigm in the creation of new medicines and diagnostics. Complete control over particle characteristics, such as size, shape, mechanical property, and surface chemistry, can enable rapid translation and facilitate the US Food and Drug Administration (FDA) approval of particle technologies for the treatment of cancer, infectious diseases, diabetes, and a host of other major illnesses. The incorporation of natural and artificial external stimuli to trigger the release of drugs enables exquisite control over the release profiles of drugs in a given environment. In this article, we examine several readily scalable top-down methods for the fabrication of shape-specific particles that utilize stimuli-responsive biomaterials for controlled drug delivery. Special attention is given to Particle Replication In Nonwetting Templates (PRINT®) technology and the application of novel triggered-release synthetic and natural polymers.
Advanced drug delivery reviews 01/2012; 64(11):1021-30. · 11.96 Impact Factor
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ABSTRACT: New methods to direct the self-assembly of particles are highly sought after for multiple applications, including photonics, electronics, and drug delivery. Most techniques, however, are limited to chemical patterning on spherical particles, limiting the range of possible structures. We developed a lithographic technique for fabrication of chemically anisotropic rod-like particles in which we can specify both the size and shape of particles and implement multiple diverse materials to control interfacial interactions. Multiphase rod-like particles, including amphiphilic diblock, triblock, and multiblock were fabricated in the same template mold having a tunable hydrophilic/hydrophobic ratio. Self-assembly of diblock or triblock rods at a water/oil interface led to the formation of bilayer or ribbon-like structures.
Journal of the American Chemical Society 10/2011; 134(13):5801-6. · 9.91 Impact Factor
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ABSTRACT: Herein we report the design of a photocurable amphiphilic co-network consisting of perfluoropolyether and poly(ethylene glycol) segments that display outstanding nonfouling characteristics with respect to spores of green fouling alga Ulva when cured under high humidity conditions. The analysis of contact angle hysteresis revealed that the poly(ethylene glycol) density at the surface was enhanced when cured under high humidity. The nonfouling behavior of nonbiocidal surfaces against marine fouling is rare because such surfaces usually reduce the adhesion of organisms rather than inhibit colonization. We propose that the resultant surface segregation of these materials induced by high humidity may be a promising strategy for achieving nonfouling materials, and such an approach is more important than simply concentrating poly(ethylene glycol) moieties at an interface because the low surface energy has been maintained in our work.
Langmuir 08/2011; 27(17):10365-9. · 4.19 Impact Factor
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ABSTRACT: We demonstrate a facile way of cross-linking hydrophobic perfluoropolyethers, PFPEs, with a series of hydrophilic poly(ethylene glycol)s, PEGs, to prepare a range of amphiphilic networks for use as fouling-release coatings. The PFPE matrix of the networks endows the coating with a low surface energy while the PEG is added to weaken fouling adhesion. It is therefore envisioned that the coating surfaces of these optically transparent and mechanically robust films will display hydrophobicity leading to nonfouling and fouling release characteristics. Two kinds of functionalized PEG oligomers have been cross-linked with reactive, dimethacryloxy-functionalized PFPE oligomers to form a range of amphiphilic networks: (i) a monomethacryloxy-functionalized PEG macromonomer (454 g/mol) (PEG454−MA) which was used to yield blends with flexible PEG chains on the surface as well as in bulk and (ii) a dimethacryloxy-functionalized PEG (550 g/mol) (PEG550−DMA) which results in PEG chains that are relatively more restricted in the network blends and serve as an added difunctional cross-linker for the network along with the dimethacryloxy-functionalized PFPE. The PFPE/PEG cross-linked networks coated on a substrate show very low swelling characteristics in water when PEG454−MA comprises not more than 10 wt % of the overall composition or when PEG550−DMA is used and does not comprise more than 30 wt % of the overall composition. The PFPE/PEG454−MA coatings having PEG chains with one untethered chain end were found to display relatively high spore and barnacle release performance in comparison to PFPE/PEG550−DMA coatings which have the PEG chains in a more restricted network topology.
01/2011;
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ABSTRACT: Herein we describe a versatile and readily scalable approach for the fabrication of particles with a variety of shapes and sizes from a single master template by augmenting the particle replication in nonwetting templates (PRINT) method with mechanical elongation. Repetition of the elongation steps in one direction leads to the fabrication of linear particles with high aspect ratio (AR), over 40 times greater than in the original master, while a range of particle shapes can be obtained by repeating the elongation procedure while changing the stretching direction, generating diamond, rectangular, curved parallelogram particles from a single cubic master.
Langmuir 01/2011; 27(2):524-8. · 4.19 Impact Factor
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Yapei Wang,
Louis M Pitet,
John A Finlay,
Lenora H Brewer,
Gemma Cone,
Douglas E Betts,
Maureen E Callow,
James A Callow,
Dean E Wendt,
Marc A Hillmyer,
Joseph M DeSimonea
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ABSTRACT: The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M(w) = 1500 g mol(-1)) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M(w) = 300, 475, 1100 g mol(-1)), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.
Biofouling 01/2011; 27(10):1139-50. · 4.43 Impact Factor
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ABSTRACT: A multilayer film consisting of poly(acrylic acid) (PAA) and an azobenzene-containing surfactant (AzoTEA) was fabricated via a layer-by-layer assembly technique. The micellar structure favored by AzoTEA while in solution results in a bilayer structure when deposited on a substrate surface. This aggregation conversion behavior favors the deposition of AzoTEA and PAA in an alternating pattern to form a photoresponsive multilayer film. The molecular amphiphilicity of AzoTEA can be tuned by photoisomerization of the azobenzene moiety, which affects the aggregation behavior of AzoTEA in both films and solutions. The disassembly of AzoTEA aggregates caused by photoirradiation can induce the disassembly of the whole multilayer film. The AzoTEA-PAA multilayer films were found to be stable in pH 4 acetic acid (AcOH) solution, unless treated with UV radiation. On the basis of the different stability of multilayers with or without photoirradiation, when the multilayer films are selectively irradiated with UV light, the regions exposed to UV radiation disassembled after being immersed in pH 4 AcOH solution for 10 min but the regions not exposed to photoradiation are maintained on the substrate. Moreover, the plausible mechanism for the assembly and disassembly of these multilayer films and the confirmation of erasable films by atomic force microscopy are discussed.
Langmuir 03/2010; 26(12):9736-41. · 4.19 Impact Factor
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ABSTRACT: We have fabricated a charge transfer interaction driven supramolecular amphiphile, the self-assembly nanostructures of which can change between vesicles and irregular continuous aggregates reversibly in response to redox stimuli.
Chemical Communications 10/2009; · 6.17 Impact Factor
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ABSTRACT: A new concept of designing a photocontrollable supramolecular polymer nanocontainer through the electrostatic association between an azobenzene-containing surfactant (AzoC10) and a double-hydrophilic block ionomer, poly(ethylene glycol)-b-poly(acrylic acid) (PEG(43)-PAA(153)), is described. Such a block ionomer complex can self-assemble in aqueous solution and form vesicle-like aggregates, which are composed of a poly(ethylene glycol) corona and a poly(acrylic acid) shell associated with azobenzene-containing surfactant. The photoisomerization of azobenzene moieties in the block ionomer complex can reversibly tune the amphiphilicity of the surfactants, inducing the disassembly of the vesicles. Such block ionomer complex vesicles are further evaluated as nanocontainers capable to encapsulate and release guest solutes on demand controlled by light irradiation. For example, the vesicles encapsulating the fluorescein sodium display clear spherical images observed by fluorescence microscopy. However, such fluorescence-marked images disappear after releasing the solute from the vesicles triggered by the UV light. Such novel materials are of both basic and practical significance, especially as prospective nanocontainers for cargo delivery.
Langmuir 08/2009; 26(2):709-15. · 4.19 Impact Factor
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Advanced Materials 06/2009; 21(43):4362 - 4365. · 13.88 Impact Factor
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Advanced Materials 06/2009; 21(28):2849 - 2864. · 13.88 Impact Factor
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Angewandte Chemie International Edition 01/2009; 48(47):8962-5. · 13.45 Impact Factor
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ABSTRACT: A photocontrolled molecular shuttle SAM based on an alpha-cyclodextrin (alpha-CD)/azobenzene inclusion complex on rough gold surfaces is fabricated, which can reversibly switch the surface wettability by transferring external energy (light) to molecular mechanical motion.
Chemical Communications 12/2008; · 6.17 Impact Factor
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ABSTRACT: This paper describes the assembly and disassembly of vesicles formed by a UV-responsive poly(ethylene glycol) terminated malachite green derivative. The UV-responsive amphiphile with both a hydrophobic malachite green group and a hydrophilic PEG group can self-organize into vesicles in water before UV irradiation. However, upon UV irradiation, the photochromic moiety can be ionized to its corresponding cation, leading to the disassembly of these vesicles. In addition, the cation can thermally recover its electrically neutral form, and the disassembled species can form vesicles reversibly on the basis of a thermal reverse reaction. The reverse reaction is temperature-controlled and can be speeded up by thermal treatment. By using various characterization techniques, e.g., transmission electron microscopy, dynamic light scattering, UV-visible spectroscopy, and NMR spectroscopy, we have confirmed that the vesicle structures can be formed, disassembled, and recovered by the above-mentioned treatments. It is anticipated greatly that this line of research may provide new insights into the mechanism behind stimuli-responsive formation and rupture of molecular assemblies, facilitating the design and synthesis of new surface active molecules for the fabrication of stimuli-responsive materials with designed functions.
Langmuir 04/2007; 23(7):4029-34. · 4.19 Impact Factor
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ABSTRACT: In this paper, we describe the use of block copolymer micelles to incorporate Azo-AOT, an azobenzene-containing amphiphile having a structure suitable for reverse micelle formation and the fabrication of polyelectrolyte/micelle multilayer films. Interestingly, it is found that the PS21-PAA157 micelles can incorporate more Azo-AOT molecules than the PS115-PAA15 micelles, which is different from the case of incorporation of noncharged hydrophobic molecules. Moreover, Azo-AOT incorporated into the PS21-PAA157 micelles undergoes a faster photoisomerization than in the PS115-PAA15 micelles, which seems to be related to different aggregation states of Azo-AOT in the two micelles. From the data of UV-vis spectra, we can infer that Azo-AOT adopts a reverse micelle-like aggregation state in the PS115-PAA15 micelles and disperses in the interface between the core and corona of PS21-PAA157 micelles. These polyelectrolyte/micelle films incorporating functional amphiphiles have great potential in the field of functional thin films.
Langmuir 03/2007; 23(5):2874-8. · 4.19 Impact Factor
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Angewandte Chemie International Edition 02/2007; 46(16):2823-6. · 13.45 Impact Factor
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ABSTRACT: We have described the synthesis of a series of poly(aryl ether) dendrimers with telluride in the core and oligo(ethylene oxide)
chains at the periphery which act as glutathione peroxidase (GPx) mimics. These series of compounds were well characterized
by 1H-NMR, 13C-NMR and ESI-MS. Using different ROOH (H2O2, cumene hydroperoxide) for testing the antioxidizing properties of these compounds, we have found that from generation 0
to 2, the activity of the dendritic GPx mimics first decreased and then increased. This can be explained on the basis of a
greater steric hindrance, going from generation 0 to 1, and stronger binding interactions going from generation 1 to 2. In
other words, there exists a balance between binding interactions and steric hindrance that may optimize the GPx activity.
Chinese Science Bulletin 09/2006; 51(19):2315-2321. · 1.32 Impact Factor
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ABSTRACT: We report on the use of block copolymer micelles of polystyrene-b-poly(acrylic acid) (PS-b-PAA) as matrixes for incorporating dibenzyl diselenide. We found that the water-insoluble diselenide, after being incorporated into the micelles, demonstrates glutathione peroxidase (GPx) activity in water. Surprisingly, the mimicking system can be adjusted to show higher GPx activity by increasing the ionic strength of the solution simply upon addition of NaCl. Moreover, dibenzyl diselenide incorporated into the micelles is quite stable and maintains its GPx activity even after exposure to the atmosphere.
Langmuir 07/2006; 22(13):5552-5. · 4.19 Impact Factor
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ABSTRACT: We described the use of block copolymer micelles as building blocks for the incorporation of water-insoluble photochromic species of azobenzene and the fabrication of multilayer films by alternating the deposition of the block copolymer micelles of poly(styrene-b-acrylic acid), incorporating azobenzene and poly(diallyl-dimethylammonium chloride). The azobenzene incorporated into the block copolymer micelles can undergo a reversible photoisomerization under the irradiation of UV and visible light sources. An interesting finding is that the photoisomerization of the azobenzene in the multilayer film is faster than it is in its normal solid film, but very similar to that in its diluted solution. Furthermore, the amount of azobenzene incorporated into the micelles can influence the photoisomerization rates in the films. Therefore, we expect that the block copolymer micelles may provide a proper microenvironment for the photoisomerization of azobenzene and the as-prepared polyelectrolyte/block copolymer micelle thin films will be useful for photoswitching materials.
Langmuir 05/2006; 22(8):3906-9. · 4.19 Impact Factor
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ABSTRACT: Novel hyperbranched polyselenides with multi-catalytic sites at the branching units have been synthesized which may provide a new approach towards glutathione peroxidase mimics.
Chemical Communications 03/2006; · 6.17 Impact Factor
