Characterizing the Structure of pH Dependent Polyelectrolyte Block Copolymer Micelles

Lee, Albert S.; Gast, Alice P.; Bütün, Vural; Armes, Steven P.

doi:10.1021/ma981865o

Cited by 282 publications

(277 citation statements)

References 21 publications

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“…These measurements reveal the presence of micellar aggregates due to the hydrophobicity of the pendant diclofenac and hydrophilicity of the PGA backbone. The difference in size depending on solution conditions is likely a consequence of the lower ionization and increased charge shielding occurring in 100 mM sodium acetate, pH 6.3 compared with 10 mM sodium phosphate, pH 7.4; the reduced electrostatic repulsion in the former allows for higher aggregation numbers and thus larger particle sizes (44). Because of the self-assembly into micellar aggregates, pendant ester linkages are sequestered into the hydrophobic core, which is likely a major factor in the slow diclofenac release kinetics that we observed.…”

Section: Resultsmentioning

confidence: 99%

Multimonth controlled small molecule release from biodegradable thin films

Hsu

Park

Hagerman

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Long-term, localized delivery of small molecules from a biodegradable thin film is challenging owing to their low molecular weight and poor charge density. Accomplishing highly extended controlled release can facilitate high therapeutic levels in specific regions of the body while significantly reducing the toxicity to vital organs typically caused by systemic administration and decreasing the need for medical intervention because of its longlasting release. Also important is the ability to achieve high drug loadings in thin film coatings to allow incorporation of significant drug amounts on implant surfaces. Here we report a sustained release formulation for small molecules based on a soluble charged polymer-drug conjugate that is immobilized into nanoscale, conformal, layer-by-layer assembled films applicable to a variety of substrate surfaces. We measured a highly predictable sustained drug release from a polymer thin film coating of 0.5-2.7 μm that continued for more than 14 mo with physiologically relevant drug concentrations, providing an important drug delivery advance. We demonstrated this effect with a potent small molecule nonsteroidal anti-inflammatory drug, diclofenac, because this drug can be used to address chronic pain, osteoarthritis, and a range of other critical medical issues.NSAID | polyelectrolyte multilayers | polymer prodrug

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Section: Resultsmentioning

confidence: 99%

Multimonth controlled small molecule release from biodegradable thin films

Hsu

Park

Hagerman

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…This weakly basic copolymer is molecularly dispersed at low pH, but forms well-defined PDEA-core micelles in alkaline solution. [20] The unimer-to-micelle transition occurs over a relatively narrow range (pH 7-9), which depends on both the molecular weight and block composition of the copolymer. Bütün et al showed that the PDMA blocks of these copolymers can be selectively quaternized by reaction with simple alkyl halides to produce permanently cationic blocks.…”

mentioning

confidence: 99%

Layer‐by‐Layer Formation of Smart Particle Coatings Using Oppositely Charged Block Copolymer Micelles

et al. 2007

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The development of novel surface coatings using the layerby-layer (LbL) application of polyelectrolytes has gained widespread attention over the last decade, [1,2] driven by a desire to develop highly functional surface coatings for producing novel composite materials. Initially, the LbL approach was demonstrated for planar surfaces.[1] Subsequently, it has been shown that colloidal substrates such as nanoparticles [2] and emulsion droplets [3,4] can also be coated. Recently, developments have been reported whereby one or more of the polyelectrolyte layers are replaced by a particulate component. [5] This has considerably increased the number of possible systems and the range of proposed applications for this platform technology; for example, it has been demonstrated that enzymes and vesicles can be incorporated into these films, suggesting possible uses as biosensors and microreactors.

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“…Polyamines with appropriate hydrophobicity, including poly[2-(N,N-diethylamino)ethyl methacrylate] (PEAMA), are known to show phase transitions as a function of pH [25][26][27]. Utilizing this character, various environmentally sensitive polymeric materials have been developed.…”

Section: Ph Response Of Hanpmentioning

confidence: 99%

Design and Preparation of a Nanoprobe for Imaging Inflammation Sites

Yoshitomi

Nagasaki

2012

Biointerphases

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To image inflammation sites, we developed a novel nanoparticle, hydroxylamine-containing nanoparticle (HANP), which emits an intense electron spin resonance (ESR)-signal triggered by enzymatic oxidation reaction and pH-sensitive self-disintegration. The nanoparticle was prepared from an amphiphilic block copolymer, poly (ethylene glycol)-b-poly[4-(2,2,6,6-tetramethylpiperidine-1-hydroxyl)aminomethylstyrene] (PEG-b-PMNT-H), which spontaneously forms a core-shell type polymeric micelle (particle diameter = ca. 50 nm) in aqueous media. Because the PMNT-H segment in the block copolymer possesses amino groups in each repeating unit, the particle can be disintegrated by protonation of the amino groups in an acidic pH environment such as inflammation sites, which is confined to the hydrophobic core of HANP.Mixing HANP with horseradish peroxidase (HRP)/H 2 O 2 mixture resulted in enzymatic oxidization of the hydroxylamines in the PEG-b-PMNT-H and converted the hydroxylamine to the stable nitroxide radical form in PEGb-poly[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)aminomethylstyrene] (PEG-b-PMNT), which shows an intense ESR signal. It is interesting to note that the ESR signal increased at a greater rate under acidic conditions (pH 5.6) than that under neutral conditions (pH 7.4), although the enzymatic activity of HRP under neutral conditions is known to be much higher than that under acidic conditions. This indicates that enzymatic oxidation reaction was accelerated by synchronizing the disintegration of HANP under acidic conditions. On the basis of these results, HANP can be used as a high-performance ESR probe for imaging of inflammation sites.

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Characterizing the Structure of pH Dependent Polyelectrolyte Block Copolymer Micelles

Cited by 282 publications

References 21 publications

Multimonth controlled small molecule release from biodegradable thin films

Multimonth controlled small molecule release from biodegradable thin films

Layer‐by‐Layer Formation of Smart Particle Coatings Using Oppositely Charged Block Copolymer Micelles

Design and Preparation of a Nanoprobe for Imaging Inflammation Sites

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