Polymeric Micelles (polymeric + micelle)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science


Selected Abstracts


Bionanotechnology: Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Mater.
Amphiphilic block copolymers can form polymer micelles for delivering hydrophobic fluorescent probes with aggregation-induced emission properties, as presented by A. K.-Y. Jen et al. on page 1413. By itself, 1,1,2,3,4,5-hexaphenylsilole (HPS) exhibits dramatically enhanced blue-green fluorescent emission efficiencies when encapsulated within the hydrophobic core of a polymeric micelle. When HPS is co-encapsulated with bis(4-(N -(1-naphthyl) phenylamino)-phenyl)fumaronitrile, effective orange-red fluorescence resonance energy transfer can be demonstrated within live RAW 264.7 cells. Illustration provided by Brent Polishak. [source]


Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Wen-Chung Wu
Abstract Three amphiphilic block copolymers are employed to form polymeric micelles and function as nanocarriers to disperse hydrophobic aggregation-induced emission (AIE) dyes, 1,1,2,3,4,5-hexaphenylsilole (HPS) and/or bis(4-(N -(1-naphthyl) phenylamino)-phenyl)fumaronitrile (NPAFN), into aqueous solution for biological studies. Compared to their virtually non-emissive properties in organic solutions, the fluorescence intensity of these AIE dyes has increased significantly due to the spatial confinement that restricts intramolecular rotation of these dyes and their better compatibility in the hydrophobic core of polymeric micelles. The effect of the chemical structure of micelle cores on the photophysical properties of AIE dyes are investigated, and the fluorescence resonance energy transfer (FRET) from the green-emitting donor (HPS) to the red-emitting acceptor (NPAFN) is explored by co-encapsulating this FRET pair in the same micelle core. The highest fluorescence quantum yield (,62%) could be achieved by encapsulating HPS aggregates in the micelles. Efficient energy transfer (>99%) and high amplification of emission (as high as 8 times) from the NPAFN acceptor could also be achieved by spatially confining the HPS/NPAFN FRET pair in the hydrophobic core of polymeric micelles. These micelles could be successfully internalized into the RAW 264.7 cells to demonstrate high-quality fluorescent images and cell viability due to improved quantum yield and reduced cytotoxicity. [source]


Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance Probes,

ADVANCED MATERIALS, Issue 16 2005
H. Ai
Increased contrast in magnetic resonance imaging (MRI) is accomplished using polymeric micelles loaded with superparamagnetic iron oxide (SPIO) nanoparticles encapsulated in biocompatible, biodegradable poly(,-caprolactone)- b -poly(ethylene glycol) (PCL- b -PEG) copolymers (see Figure). The loaded micelles show significantly improved T2 relaxivities and remarkable MRI detection sensitivity. [source]


The Formation of Biodegradable Polymeric Micelles from Newly Synthesized Poly(aspartic acid)- block -Polylactide AB-Type Diblock Copolymers

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 6 2004
Hidetoshi Arimura
Abstract Summary: A poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymer was synthesized through the polymerization of , -benzyl- L -aspartate- N -carboxyanhydride [Asp(OBzl)-NCA] with amino-terminating polylactide (NH2 -PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the monomer/initiator ratio. Dynamic light scattering measurements of PAsp- block -PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated. The structure and formation of micelles of the poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymers synthesized here. [source]


Reversible Three-State Switching of Multicolor Fluorescence Emission by Multiple Stimuli Modulated FRET Processes within Thermoresponsive Polymeric Micelles,

ANGEWANDTE CHEMIE, Issue 30 2010
Changhua Li
Micellare Verkehrsampeln: Das im Titel bezeichnete System mit resonantem Fluoreszenzenergietransfer (FRET) nutzt eine Art Donorfarbstoff und zwei Arten Akzeptorfarbstoffe. Das An- und Ausschalten der Fluoreszenz der beiden Akzeptorfarbstoffe kann über den pH-Wert bzw. Licht gesteuert werden. Dieses neuartige vielfarbige lumineszierende Polymersystem kann als ratiometrische Sonde mit einstellbarer Empfindlichkeit für pH-Wert und Temperatur fungieren. [source]


Functional Polymeric Micelles Formed from a Novel Cationic Star Block Copolymer

CHEMPHYSCHEM, Issue 10 2003
Ren-Hua Jin Dr.
Flowers made from stars: A star polymer, which consists of a porphyrin center to which four arms with cationic poly(ethyleneimine) (PEI) and hydrophobic poly(phenyloxazoline) (PPOZ) segments were attached, was synthesized and shown to form micelles in both aqueous and organic media (see picture). In aqueous media, the star formed a micelle in which a hydrophobic PPOZ core was surrounded by cationic corona PEI. The porphyrin moieties enclosed in the micellar core can effectively communicate with an ionic substrate enriched in the cationic corona. In organic media, the star gave a flowerlike micelle in which the ionomer segment PEI assembled to form a core and the nonionic PPOZ segments formed a looplike corona coating the core. [source]


Ultrasonic-activated micellar drug delivery for cancer treatment

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009
Ghaleb A. Husseini
Abstract The use of nanoparticles and ultrasound in medicine continues to evolve. Great strides have been made in the areas of producing micelles, nanoemulsions, and solid nanoparticles that can be used in drug delivery. An effective nanocarrier allows for the delivery of a high concentration of potent medications to targeted tissue while minimizing the side effect of the agent to the rest of the body. Polymeric micelles have been shown to encapsulate therapeutic agents and maintain their structural integrity at lower concentrations. Ultrasound is currently being used in drug delivery as well as diagnostics, and has many advantages that elevate its importance in drug delivery. The technique is noninvasive, thus no surgery is needed; the ultrasonic waves can be easily controlled by advanced electronic technology so that they can be focused on the desired target volume. Additionally, the physics of ultrasound are widely used and well understood; thus ultrasonic application can be tailored towards a particular drug delivery system. In this article, we review the recent progress made in research that utilizes both polymeric micelles and ultrasonic power in drug delivery. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:795,811, 2009 [source]


Amphiphilic PEG/alkyl-grafted comb polylactides

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007
Xuwei Jiang
Abstract Amphiphilic polylactides (PLAs) with well-defined architectures were synthesized by ring-opening polymerization of AB monomers (glycolides) substituted with both a long chain alkyl group and a triethylene glycol segment terminated in either a methyl or benzyl group. The resulting amphiphilic PLAs had number average molecular weights >100,000 g/mol. DSC analysis revealed a first-order phase transition at , 20 °C, reflecting the crystalline nature of the linear alkyl side chains. Polymeric micelles were prepared by the solvent displacement method in water. Dynamic light scattering measurements support formation of a mixture of 20-nm-diameter unimolecular micelles and 60-nm particles comprised of an estimated 25 polymer molecules. UV,vis characterization of micelles formed from acetone,water solutions containing azobenzene confirmed encapsulation of the hydrophobic dye, suggesting their potential as new amphiphilic PLAs as drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5227,5236, 2007 [source]


Bionanotechnology: Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Mater.
Amphiphilic block copolymers can form polymer micelles for delivering hydrophobic fluorescent probes with aggregation-induced emission properties, as presented by A. K.-Y. Jen et al. on page 1413. By itself, 1,1,2,3,4,5-hexaphenylsilole (HPS) exhibits dramatically enhanced blue-green fluorescent emission efficiencies when encapsulated within the hydrophobic core of a polymeric micelle. When HPS is co-encapsulated with bis(4-(N -(1-naphthyl) phenylamino)-phenyl)fumaronitrile, effective orange-red fluorescence resonance energy transfer can be demonstrated within live RAW 264.7 cells. Illustration provided by Brent Polishak. [source]


The antitumor activity of NK012, an SN-38,incorporating micelle, in combination with bevacizumab against lung cancer xenografts

CANCER, Issue 19 2010
Hirotsugu Kenmotsu MD
Abstract BACKGROUND: It has been demonstrated that NK012, a novel 7-ethyl-10-hydroxycamptothecin (SN-38)-incorporating polymeric micelle, exerts significantly more potent antitumor activity against various human tumor xenografts than irinotecan (CPT-11) (a water-soluble prodrug of SN-38). Combination therapy of anticancer agents with bevacizumab (Bv), an anti-vascualr endothelial growth factor humanized monoclonal antibody, has more potently inhibited tumor growth than either agent alone. In the current study, the authors examined the antitumor effect of NK012 in combination with Bv against human lung cancer. METHODS: Nude mice bearing lung adenocarcinoma (PC-14 or A549 xenografts) were administered NK012 at SN-38-equivalent doses of 5 mg/kg or 30 mg/kg in combination with or without Bv at 5 mg/kg. CPT-11 at a dose of 66.7 mg/kg was administered with or without Bv at a dose of 5 mg/kg in the same experimental model. To evaluate interaction with Bv, the pharmacokinetics and microvessel density in tumors that were treated on each regimen were analyzed. RESULT: In vitro, the growth-inhibitory effect of NK012 was 50-fold more potent than that of CPT-11 and was almost equivalent to that of SN-38. In vivo studies revealed that the combination of NK012 plus Bv had significantly greater antitumor activity against human lung cancer xenografts compared with NK012 alone (PC-14, P = .0261; A549, P < .001). The pharmacokinetic profile of NK012 revealed that coadministration of Bv did not interfere with the accumulation of NK012. CONCLUSIONS: In this study, significant antitumor activity was noted with NK012 in combination with Bv against lung cancer cells. The current results warrant the clinical evaluation of NK012 in lung cancer. Cancer 2010. © 2010 American Cancer Society. [source]


Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+ -Dependent Enzymes

ELECTROANALYSIS, Issue 7-8 2010

Abstract Previous work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+ -dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6,,W/cm2 and current density of 845±35.5,,A/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD. [source]


Enhancement of Aggregation-Induced Emission in Dye-Encapsulating Polymeric Micelles for Bioimaging

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2010
Wen-Chung Wu
Abstract Three amphiphilic block copolymers are employed to form polymeric micelles and function as nanocarriers to disperse hydrophobic aggregation-induced emission (AIE) dyes, 1,1,2,3,4,5-hexaphenylsilole (HPS) and/or bis(4-(N -(1-naphthyl) phenylamino)-phenyl)fumaronitrile (NPAFN), into aqueous solution for biological studies. Compared to their virtually non-emissive properties in organic solutions, the fluorescence intensity of these AIE dyes has increased significantly due to the spatial confinement that restricts intramolecular rotation of these dyes and their better compatibility in the hydrophobic core of polymeric micelles. The effect of the chemical structure of micelle cores on the photophysical properties of AIE dyes are investigated, and the fluorescence resonance energy transfer (FRET) from the green-emitting donor (HPS) to the red-emitting acceptor (NPAFN) is explored by co-encapsulating this FRET pair in the same micelle core. The highest fluorescence quantum yield (,62%) could be achieved by encapsulating HPS aggregates in the micelles. Efficient energy transfer (>99%) and high amplification of emission (as high as 8 times) from the NPAFN acceptor could also be achieved by spatially confining the HPS/NPAFN FRET pair in the hydrophobic core of polymeric micelles. These micelles could be successfully internalized into the RAW 264.7 cells to demonstrate high-quality fluorescent images and cell viability due to improved quantum yield and reduced cytotoxicity. [source]


Synthesis of PEOlated Fe3O4@SiO2 Nanoparticles via Bioinspired Silification for Magnetic Resonance Imaging

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Happy Tan
Abstract Inspired by the biosilification process, a highly benign synthesis strategy is successfully developed to synthesize PEOlated Fe3O4@SiO2 nanoparticles (PEOFSN) at room temperature and near-neutral pH. The success of such a strategy lies in the simultaneous encapsulation of Fe3O4 nanocrystals and silica precursors into the core of PEO-based polymeric micelles. The encapsulation results in the formation of a silica shell being confined to the interface between the core and corona of the Fe3O4 -nanocrystal-loaded polymeric micelles. Consequently, the surface of the Fe3O4@SiO2 nanoparticle is intrinsically covered by a layer of free PEO chains, which enable the PEOFSN to be colloidally stable not only at room temperature, but also upon incubation in the presence of proteins under physiological conditions. In addition, the silica shell formation does not cause any detrimental effects to the encapsulated Fe3O4 nanocrystals with respect to their size, morphology, crystallinity, and magnetic properties, as shown by their physicochemical behavior. The PEOFSN are shown to be good candidates for magnetic resonance imaging (MRI) contrast agents as demonstrated by the high r2/r1 ratio with long-term stability under high magnetic field, as well as the lack of cytotoxicity. [source]


Magnetite-Loaded Polymeric Micelles as Ultrasensitive Magnetic-Resonance Probes,

ADVANCED MATERIALS, Issue 16 2005
H. Ai
Increased contrast in magnetic resonance imaging (MRI) is accomplished using polymeric micelles loaded with superparamagnetic iron oxide (SPIO) nanoparticles encapsulated in biocompatible, biodegradable poly(,-caprolactone)- b -poly(ethylene glycol) (PCL- b -PEG) copolymers (see Figure). The loaded micelles show significantly improved T2 relaxivities and remarkable MRI detection sensitivity. [source]


Ultrasonic-activated micellar drug delivery for cancer treatment

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009
Ghaleb A. Husseini
Abstract The use of nanoparticles and ultrasound in medicine continues to evolve. Great strides have been made in the areas of producing micelles, nanoemulsions, and solid nanoparticles that can be used in drug delivery. An effective nanocarrier allows for the delivery of a high concentration of potent medications to targeted tissue while minimizing the side effect of the agent to the rest of the body. Polymeric micelles have been shown to encapsulate therapeutic agents and maintain their structural integrity at lower concentrations. Ultrasound is currently being used in drug delivery as well as diagnostics, and has many advantages that elevate its importance in drug delivery. The technique is noninvasive, thus no surgery is needed; the ultrasonic waves can be easily controlled by advanced electronic technology so that they can be focused on the desired target volume. Additionally, the physics of ultrasound are widely used and well understood; thus ultrasonic application can be tailored towards a particular drug delivery system. In this article, we review the recent progress made in research that utilizes both polymeric micelles and ultrasonic power in drug delivery. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:795,811, 2009 [source]


Biodistribution characteristics of all- trans retinoic acid incorporated in liposomes and polymeric micelles following intravenous administration

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2005
Shigeru Kawakami
Abstract The aim of this study was to investigate the biodistribution characteristics of all- trans retinoic acid (ATRA) incorporated in liposomes and polymeric micelles following intravenous administration. [3H] ATRA were incorporated in distearoylphosphatidylcholine (DSPC)/cholesterol (6:4) liposomes. Two types of block copolymers, poly (ethylene glycol)-b-poly-(aspartic acid) derivatives with benzyl (Bz-75) groups, were synthesized to prepare the polymeric micelles for [3H]ATRA incorporation. ATRA were dissolved in mouse serum to analyze their inherent distribution. After intravenous administration, the blood concentration of [3H] ATRA in liposomes and polymeric micelles (Bz-75) was higher than that of inherent [3H]ATRA, suggesting that liposomes and polymeric micelles (Bz-75) control the distribution of ATRA. Pharmacokinetic analysis demonstrated that [3H]ATRA incorporated in polymeric micelles (Bz-75) exhibit the largest AUCblood and lowest hepatic clearance of ATRA, suggesting that polymeric micelles (Bz-75) are an effective ATRA carrier system for acute promyelocytic leukemia (APL) therapy. These results have potential implications for the design of ATRA carriers for APL patients. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:2606,2615, 2005 [source]


In-vitro and in-vivo evaluation of pH-responsive polymeric micelles in a photodynamic cancer therapy model

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2001
J. Taillefer
pH-sensitive polymeric micelles of randomly and terminally alkylated N-isopropylacrylamide copolymers were prepared and characterized. Aluminium chloride phthalocyanine (AlClPc), a second generation sensitizer for the photodynamic therapy of cancer, was incorporated in the micelles by dialysis. Their photodynamic activities were evaluated in-vitro against EMT-6 mouse mammary tumour cells and in-vivo against EMT-6 tumours implanted intradermally on each hind thigh of Balb/c mice. pH-sensitive polymeric micelles were found to exhibit greater cytotoxicity in-vitro than control Cremophor EL formulations. In the presence of chloroquine, a weak base that raises the internal pH of acidic organelles, in-vitro experiments demonstrated the importance of endosomal/lysosomal acidity for the pH-sensitive polymeric micelles to be fully effective. Biodistribution was assessed by fluorescence of tissue extracts after intravenous injection of 2 ,mol kg,1 AlClPc. The results revealed accumulation of AlClPc polymeric micelles in the liver, spleen and lungs, with a lower tumour uptake than AlClPc Cremophor EL formulations. However, polymeric micelles exhibited similar activity in-vivo to the control Cremophor EL formulations, demonstrating the higher potency of AlClPc polymeric micelles when localized in tumour tissue. It was concluded that polymeric micelles represent a good alternative to Cremophor EL preparations for the vectorization of hydrophobic drugs. [source]


Synthesis and characterization of core,shell-type polymeric micelles from diblock copolymers via reversible addition,fragmentation chain transfer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2006
Ping Zhang
Abstract A method was developed to enable the formation of nanoparticles by reversible addition,fragmentation chain transfer polymerization. The thermoresponsive behavior of polymeric micelles was modified by means of micellar inner cores and an outer shell. Polymeric micelles comprising AB block copolymers of poly(N -isopropylacrylamide) (PIPAAm) and poly(2-hydroxyethylacrylate) (PHEA) or polystyrene (PSt) were prepared. PIPAAm- b -PHEA and PIPAAm- b -PSt block copolymers formed a core,shell micellar structure after the dialysis of the block copolymer solutions in organic solvents against water at 20 °C. Upon heating above the lower critical solution temperature (LCST), PIPAAm- b -PHEA micelles exhibited an abrupt increase in polarity and an abrupt decrease in rigidity sensed by pyrene. In contrast, PIPAAm- b -PSt micelles maintained constant values with lower polarity and higher rigidity than those of PIPAAm- b -PHEA micelles over the temperature range of 20,40 °C. Structural deformations produced by the change in the outer polymer shell with temperature cycles through the LCST were proposed for the PHEA core, which possessed a lower glass-transition temperature (ca. 20 °C) than the LCST of the PIPAAm outer shell (ca. 32.5 °C), whereas the PSt core with a much higher glass-transition temperature (ca. 100 °C) retained its structure. The nature of the hydrophobic segments composing the micelle inner core offered an important control point for thermoresponsive drug release and the drug activity of the thermoresponsive polymeric micelles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3312,3320, 2006 [source]


Chemo-Enzymatic Synthesis of Degradable PTMC- b -PECA- b -PTMC Triblock Copolymers and their Micelle Formation for pH-Dependent Controlled Release

MACROMOLECULAR BIOSCIENCE, Issue 6 2009
Sachiko Kaihara
Abstract A series of degradable triblock copolymers, poly(trimethylene carbonate)- block -poly[poly(ethylene glycol)- co -cyclic acetal]- block -poly(trimethylene carbonate) (PTMC- b -PECA- b -PTMC), were chemo-enzymatically synthesized. Cyclic acetal was introduced into a poly(ethylene glycol) segment as a degradable segment to impart a pH-dependent degradation nature and to prevent the production of acidic degradation products. Amphiphilic polymeric micelles were successfully prepared, and the properties of the micelles were significantly affected by their chemical compositions and the molecular weights. A drug release study showed that the release rate increased as the pH of the buffer decreased due to the degradation of the cyclic acetal segments, indicating its high utility for pH-sensitive controlled release. [source]


Cascade Reactions in Polymeric Nanoreactors: Mono (Rh)- and Bimetallic (Rh/Ir) Micellar Catalysis in the Hydroaminomethylation of 1-Octene

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2008
Barbara Gall
Abstract The concept of micellar catalysis was transferred to the hydroaminomethylation of 1-octene with N,N -dimethylamine. In the first series of experiments a rhodium(I) complex with amphiphilic triphenylphosphane functionalized poly(2-oxazoline)s as macroligand was applied as catalyst. Results obtained under standard hydroformylation conditions (T,=,100,°C, p,=,50 bar) were not satisfying with regard to activities and selectivities of the hydroaminomethylation reaction. Rising the temperature to 150,°C increased the yield of amine to 22% with a corresponding n/iso selectivity of 7.5 and a TOF number of 461 h,1. Best results were obtained by applying a dual Rh/Ir catalyst within the polymeric micelles leading at lower temperature of 130,°C to an amine yield of 24% with a corresponding n/iso selectivity of 11 and TOF numbers of about 600 h,1. [source]


The Formation of Biodegradable Polymeric Micelles from Newly Synthesized Poly(aspartic acid)- block -Polylactide AB-Type Diblock Copolymers

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 6 2004
Hidetoshi Arimura
Abstract Summary: A poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymer was synthesized through the polymerization of , -benzyl- L -aspartate- N -carboxyanhydride [Asp(OBzl)-NCA] with amino-terminating polylactide (NH2 -PLA) as a macroinitiator. The chain length of the PAsp segment could be easily controlled by changing the monomer/initiator ratio. Dynamic light scattering measurements of PAsp- block -PLA aqueous solutions revealed the formation of polymeric micelles. Changes in the micelles as a function of pH were investigated. The structure and formation of micelles of the poly(aspartic acid)- block -polylactide (PAsp- block -PLA) diblock copolymers synthesized here. [source]


Light-sensitive Intelligent Drug Delivery Systems,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009
Carmen Alvarez-Lorenzo
Drug delivery systems (DDS) capable of releasing an active molecule at the appropriate site and at a rate that adjusts in response to the progression of the disease or to certain functions/biorhythms of the organism are particularly appealing. Biocompatible materials sensitive to certain physiological variables or external physicochemical stimuli (intelligent materials) can be used for achieving this aim. Light-responsiveness is receiving increasing attention owing to the possibility of developing materials sensitive to innocuous electromagnetic radiation (mainly in the UV, visible and near-infrared range), which can be applied on demand at well delimited sites of the body. Some light-responsive DDS are of a single use (i.e. the light triggers an irreversible structural change that provokes the delivery of the entire dose) while others able to undergo reversible structural changes when cycles of light/dark are applied, behave as multi-switchable carriers (releasing the drug in a pulsatile manner). In this review, the mechanisms used to develop polymeric micelles, gels, liposomes and nanocomposites with light-sensitiveness are analyzed. Examples of the capability of some polymeric, lipidic and inorganic structures to regulate the release of small solutes and biomacromolecules are presented and the potential of light-sensitive carriers as functional components of intelligent DDS is discussed. [source]


Cancer-associated pH-responsive tetracopolymeric micelles composed of poly(ethylene glycol)- b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008
Kyung Taek Oh
Abstract To create a novel vector for specifically delivering anticancer therapy to solid tumors, we used diafiltration to synthesize pH-sensitive polymeric micelles. The micelles, formed from a tetrablock copolymer [poly(ethylene glycol) -b -poly(L -histidine)- b -poly(L -lactic acid)- b -poly(ethylene glycol)] consisted of a hydrophobic poly(L -histidine) (polyHis) and poly(L -lactic acid) (PLA) core and a hydrophilic poly(ethylene glycol) (PEG) shell, in which we encapsulated the model anticancer drug doxorubicin (DOX). The robust micelles exhibited a critical micellar concentration (CMC) of 2.1,3.5,µg/ml and an average size of 65,80,nm pH 7.4. Importantly, they showed a pH-dependent micellar destabilization, due to the concurrent ionization of the polyHis and the rigidity of the PLA in the micellar core. In particular, the molecular weight of PLA block affected the ionization of the micellar core. Depending on the molecular weight of the PLA block, the micelles triggering released DOX at pH 6.8 (i.e. cancer acidic pH) or pH 6.4 (i.e. endosomal pH), making this system a useful tool for specifically treating solid cancers or delivering cytoplasmic cargo in vivo. Copyright © 2008 John Wiley & Sons, Ltd. [source]