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1.
The chitosan microspheres (CS‐CL) were prepared by suspension crosslinking method and used as carriers of R‐phycoerythrin (R‐PE). In this study, R‐PE was loaded in the microspheres and released in vitro. The effects of pH value, temperature, ionic strength, and R‐PE concentration on loading efficiency and release behavior were discussed. A novel microsphere that contained agarose (CS‐AR MP) was prepared and the basic loading and releasing behavior for R‐PE of this kind of new microspheres were also investigated. The results showed that all these chitosan microspheres have the ability to control‐release R‐PE. The addition of agarose may somewhat accelerate the release rate of R‐PE from microspheres and reduce the capacity of adsorption for R‐PE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2759–2766, 2007 相似文献
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Fwu‐Long Mi Shin‐Shing Shyu Tsung‐Bi Wong Shiang‐Fang Jang Sung‐Tao Lee Kai‐Tai Lu 《应用聚合物科学杂志》1999,74(5):1093-1107
Chitosangel beads were prepared using an in‐liquid curing method by ionotropic crosslinking or interpolymer linkage with tripolyphosphate (TPP) or polyphosphate (PP). The ionic interaction of chitosan with TPP or PP is pH‐dependent due to the transition of “ladder‐loop” complex structures. Chitosan gel beads cured in a pH value lower than 6 of a TPP solution was a controlled homogeneous ionic‐crosslinking reaction, whereas chitosan gel beads cured in a lower pH PP solution was a nonhomogeneous interpolymer complex reaction due to the mass‐transfer resistance for the diffusion of macromolecular PP. According to the results of FTIR and EDS studies, it was suggested that significantly increasing the ionic‐crosslinking density or interpolymer linkage of a chitosan–TPP or chitosan–PP complex could be achieved by transferring the pH value of curing agent, TPP or PP, from basic to acidic. The swelling behavior of various chitosan beads in acid medium appeared to depend on the ionic‐crosslinking density or interpolymer linkage of the chitosan–TPP or chitosan–PP complex, which were deeply affected by the in‐liquid curing mechanism of the chitosan gel beads. By the transition of the in‐liquid curing mechanism, the swelling degree of chitosan–TPP or chitosan–PP beads was depressed and the disintegration of chitosan–TPP or chitosan–PP beads did not occur in strong acid. The drug‐release patterns of the modified chitosan gel beads in simulated intestinal and gastric juices were sustained for 20 h. These results indicate that the sustained release of anticancer drugs could be achieved due to the variation of the reaction mechanism of a chitosan–polyelectrolyte pH‐dependent ionic interaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1093–1107, 1999 相似文献
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A novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
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Yunyan Bai Zhe Zhang Mingxiao Deng Li Chen Chaoliang He Xiuli Zhuang Xuesi Chen 《Polymer International》2012,61(7):1151-1157
Microgel particles were prepared, made of hydroxypropylcellulose‐graft‐(acrylic acid) (HPC‐g‐AA) and acrylic acid(AA). The particles undergo reversible volume phase transitions in response to both pH and temperature changes while keeping the inherent properties of PAA and HPC‐g‐AA. Dynamic light scattering measurements reveal that the average hydrodynamic radius and hydrodynamic radius distributions of the microgel particles depend on temperature and pH. The microgels exhibit excellent pH sensitivity and a higher swelling ratio at higher pH in aqueous solution. In vitro release study shows that the amount of insulin released from the microgels is less at pH = 1.2 than at pH = 6.8. The results indicate that the resultant microgels seem to be of great potential for intelligent oral drug delivery. Copyright © 2012 Society of Chemical Industry 相似文献
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Linear (1‐arm) and star‐shaped (4‐, 6‐, and 16‐arm) poly(D,L ‐lactide)s (PDLLs) were synthesized by ring‐opening polymerization in bulk of D,L ‐lactide monomer. Hydroxyl end‐group compounds and stannous octoate were used as the initiator and catalyst, respectively. The intrinsic viscosity and glass transition temperature (Tg) of the PDLLs decreased steadily as the branch arm number increased for similar molecular weights. However, the intrinsic viscosity and Tg values of the linear PDLL were less than the star‐shaped PDLL for similar each PDLL arm lengths. Ibuprofen, a poorly water soluble model drug was entrapped in the PDLL microspheres. All drug‐loaded PDLL microspheres were prepared by the oil‐in‐water emulsion solvent evaporation method, were spherical in shape, and had a smooth surface with fine dispersibility. In vitro drug release behaviors indicated that the drug release from the microspheres with higher branch arm number was faster than from those with lower branch arm number. Moreover, the drug release from the star‐shaped PDLL microspheres was slower than that of the linear PDLL microspheres for similar PDLL arm lengths. The drug release behavior could be adjusted through both the branch arm number and arm length of PDLL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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This article describes a new and simple method to control the release of payloads encapsulated in chitosan capsules. The capsules with the liquid core and rigid shell are performed by drop‐wisely adding chitosan solution into anionic surfactant solution. The capsules can be destroyed by β‐CD because β‐CD binds and sequesters surfactant from the shell through the host‐guest interaction. The destruction process is studied by optical microscopy and scanning electron microscopy. The capsules can swell in acid solution and shrink in alkaline solution. It is found that the destruction speed increases with increasing acidity or alkalinity of β‐CD solution. Rhodamine B encapsulated in the liquid‐core of chitosan capsules can be released from the capsules in β‐CD solution. The release rate can be adjusted by the pH value of β‐CD solution. The release speed of the capsule increases with the increase of acidity or alkalinity in β‐CD solution. The above concept can provide more versatility for controlled release of a variety of payloads such as drugs, cosmetics, and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45229. 相似文献
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A multifunctional sandwich type wound dressing was designed in which two types of microspheres, one to alleviate the pain (ibuprofen) and the other to protect the wound from infections (Gentamicin or Ciprofloxacin), were embedded into bilayer chitosan sponge. pH of the wound increases from acidic (pH ~ 5) to basic (pH ~ 8) via infection, so pH-dependent antibiotic release system was designed using gelatin B microspheres to respond to increasing pH. Ibuprofen release from chitosan microspheres, on the other hand, was pH-independent not to intervene with pain management in changing pH conditions. Crosslinking with glutaraldehyde (GA) affected both release profile and size distribution of microspheres and 2.5% GA was chosen to obtain pH-responsive gelatin microspheres with narrow size distribution (80% of microspheres in between 15 and 25 μm). The final system was found to be effective against both Staphylococcus aureus and Escherichia coli and changing pH seemed to affect the antimicrobial agent delivery as desired. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48252. 相似文献
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Nirmal K. Patel Jigar Joshi Deepak Mishra Vishnu A. Patel Vijay Kumar Sinha 《应用聚合物科学杂志》2010,115(6):3442-3450
The aim of the study was to prepare the controlled release dosage of carbamazepine matrix tablets using wet granulation technique. The graft copolymerization of carboxymethyl chitosan (CMCH) with 2‐hydroxyethylmethacrylate (HEMA) was carried out. The product was characterized by Fourier‐transform infrared, scanning electron microscopy, transmission electron micrograph, and X‐ray diffraction anayses. CMCH‐g‐HEMA was used as binder to prepare the matrix tablets containing carbamazepine. The properties of tablets like hardness, friability, and dissolution influenced by binder were studied. In vitro release of the matrix tablets was carried out with the phosphate‐buffered solution (pH 7.4) at 37°C and 100 × g using USP dissolution test apparatus. Release rate of carbamazepine from controlled release matrix tablets was compared with the commercially marketed tablet, Tagretol 200. Results show that after 6 hrs percentage drug release of formulated tablet CGH5 was 20.42% and that of Tegretol 200 was 18.32%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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The utility of the Poly(3‐hydroxybutyrate) (PHB) to encapsulate and control the release of bovine serum albumin (BSA), via microspheres, was investigated. Various preparing parameters, including polymer concentration in oil phase, emulsification concentration in external water phase, volume ratio of inner water phase to oil phase, and volume ratio of primary emulsion to external water phase were altered during the microspheres production. The effects of these changes on the morphological characteristics of the microspheres, size of the microspheres, drug loading, encapsulation efficiency, and drug release rates were examined. The diameter of the microspheres ranged from 6.9 to 20.3 μm and showed different degrees of porous structure depending on the different preparation parameters. The maximum and minimum BSA encapsulation efficiency within the polymeric microspheres were 69.8 and 7.5%, respectively, varying with preparation conditions. The controlled release characteristics of the microspheres for BSA were investigated in pH 7.4 media. The initial BSA burst release from 8.9 to 63.1% followed by constant slow release for 28 days was observed for BSA from BSA‐loaded microspheres and followed the Higuchi matrix model. So, the release behavior of microspheres showed the feasibility of BSA‐loaded microspheres as controlled release devices. Pristine BSA, pristine PHB microspheres, and BSA‐loaded microspheres were analyzed by Fourier transform infrared spectrophotometer, which indicated no interaction between BSA and PHB. Differential scanning calorimetry on BSA‐loaded microspheres indicated a molecular level dispersion of BSA in the microspheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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Microspheres were prepared from carboxymethylated chitosan (CM‐chitosan) and alginate by emulsion phase separation. Their structure and morphology were characterized with IR spectroscopy and scanning electron microscopy. Bovine serum albumin (BSA) was encapsulated in the microspheres to test the release behavior. The swelling behavior, encapsulation efficiency, and release behavior of BSA from the microspheres at different pHs and with a pH‐gradient condition were investigated. The BSA encapsulation efficiency was calculated to be 80%. The degree of swelling of the microspheres without BSA loaded at pH 7.2 was much higher than that at pH 1.0. The encapsulated BSA was quickly released in a Tris–HCl buffer (pH 7.2), whereas a small amount of BSA was released under acid conditions (pH 1.0) because of the strong electrostatic interaction between ? NH2 groups of CM‐chitosan and ? COOH groups of alginic acid and a dense structure caused by a Ca2+ crosslinked bridge. For the simulation of the processing of the drug under the conditions of the intestine, the microspheres were tested in a pH‐gradient medium, in which an acceleration of the release occurred at pH 7.4 after a lag time at a low pH (5.8–6.8). At pH 7.4, a large amount of BSA was released from the microspheres in a short time because of the rapid swelling of the microspheres. However, the release only depended on the diffusion of BSA at relatively low pHs, this resulted in a relatively low release. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 878–882, 2004 相似文献
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Cypriano G da Trindade Neto Ana LP Fernandes Ana IB Santos Waldenice A Morais Marcos VM Navarro Tereza NC Dantas Mrcia R Pereira Jos LC Fonseca 《Polymer International》2005,54(4):659-666
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry 相似文献
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An inexpensive and simple method was adopted for the preparation of chitosan beads, crosslinked with glutaraldehyde (GA), for the controlled release of diclofenac sodium (DS). The beads were prepared by varying the experimental conditions such as pH, temperature, and extent of crosslinking. The absence of any chemical interaction among drug, polymer, and the crosslinking agent was confirmed by FTIR and thermal analysis. The beads were characterized by microscopy, which indicated that the particles were in the size range of 500–700 μm and SEM studies revealed smooth surface and spherical shape of beads. The beads produced at higher temperature and extended exposure to GA exhibited lower drug content, whereas increased drug loading resulted in enhanced drug release. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 211–217, 2007 相似文献
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A series of pH‐sensitive composite hydrogel beads, carboxymethyl cellulose‐g‐poly(acrylic acid)/attapulgite/sodium alginate (CMC‐g‐PAA/APT/SA), were prepared by combining CMC‐g‐PAA/APT composite and SA, using Ca2+ as the ionic crosslinking agent and diclofenac sodium (DS) as the model drug. The effects of APT content and external pH on the swelling properties and release behaviors of DS from the composite hydrogel beads were investigated. The results showed that the composite hydrogel beads exhibited good pH‐sensitivity. Introducing 20% APT into CMC‐g‐PAA hydrogel could change the surface structure of the composite hydrogel beads, decrease the swelling ability, and relieve the burst release effect of DS. The drug cumulative release ratio of DS from the hydrogel beads in simulated gastric fluid was only 3.71% within 3 hour, but in simulated intestinal fluid about 50% for 3 hour, 85% for 12 hour, up to 90% after 24 hour. The obtained results indicated that the CMC‐g‐PAA/APT/SA hydrogel beads could be applied to the drug delivery system as drug carriers in the intestinal tract. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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Biodegradable poly(aspartic acid) (PASP) hydrogel and PASP/gelatin complex were prepared to evaluate their potential application as pH‐sensitive matrices for controlled protein release. Entrapment of myoglobin (Mb) and its release were compared between the two types of carriers. It was found that incorporation of Mb into PASP hydrogel strongly depended on the medium pH and NaCl concentration, and was time‐consuming. However, complete entrapment of Mb into PASP/gelatin complex was found within pH ranged from 2.5 to 4.0, which was concomitant with the formation of PASP/gelatin complex. By adjusting Mb feed ratio, Mb entrapment in the complex can be up to 31.54% (by weight) with high loading efficiency (96.2%). Gradual release of Mb from PASP hydrogel was observed within pH 2.0–7.4, while Mb release from PASP/gelatin complex was negligible within pH 2.0–4.2 for 4 days. In addition, pulsatile Mb release can be achieved by combining polyanhydride with pH‐sensitive PASP/gelatin complex, while the device composed of polyanhydride and PASP hydrogel is mechanically unstable. PASP/gelatin complex formed by electrostatic interactions is superior to the single‐component PASP hydrogel synthesized by chemical cross‐linking as pH‐sensitive matrices for controlled protein release when entrapment of proteins and pH‐sensitivity of protein release are concerned. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006 相似文献
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《国际聚合物材料杂志》2012,61(3):133-139
Poly(N′-isopropylacrylamide-co–methacryl amide) has been prepared by free-radical emulsion polymerization. The copolymer was transformed into thermoresponsive microspheres by chemical crosslinking with N′, N′ Methylenebis-acrylamide (NNMBA). Enalpril maleate (ENAM), an anti-hypertensive drug, was successfully loaded into these microspheres during in-situ polymerization. DSC and X-RD analysis of the drug-loaded and plain microspheres have confirmed partial dispersion of ENAM in the microspheres. SEM confirmed the spherical nature of the particles with a mean particle size of 100 µm. Drug release profiles of these microspheres exhibited a prolonged release of ENAM for more than 12 h. 相似文献
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Controlled release behaviours of nifedipine loaded poly (D,L‐lactide) (PLA) and poly(D,L‐lactide‐co‐glycolide) (PLGA) microspheres are investigated and modelled in this paper. Based on the integrated consideration of diffusion, finite dissolution rate, moving front of dissolution and size distribution of microspheres, a mathematic model is presented to quantitatively describe the drug release kinetics. The coupled partial differential equations are numerically solved. Dynamic concentration profiles of both dissolved and undissolved drug in the microspheres are analyzed. In comparison with the diffusion model and Higuchi model, the proposed dissolution‐diffusion model is characteristic of describing the whole release process without limitation of different dissolution rate or dissolubility. The diffusion coefficient and the dissolution rate constants are evaluated from measured release profiles. The effects of microstructures of polymer microspheres on release behaviours are related to parameters of the model. Based on the mathematical model and in vitro release data, intrinsic mass transfer mechanism is further investigated. 相似文献
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Structure–property relationship of pH‐sensitive (PCL)2(PDEA‐b‐PPEGMA)2 micelles: Experiment and DPD simulation 
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下载免费PDF全文 Quan Chen Yu Qian Xiu Fang Wen Li Juan Zhang 《American Institute of Chemical Engineers》2014,60(10):3634-3646
The experiment and dissipative particle dynamics simulation were carried out on four polymers with different block ratios for the investigation of the structure–property relationship of (poly(ε‐caprolactone)2‐[poly(2‐(diethylamino)ethyl methacrylate)‐b‐poly(poly(ethylene glycol) methyl ether methacrylate)]2 [(PCL)2(PDEA‐b‐PPEGMA)2] micelles. The miktoarm star polymers assembled into spherical micelles composed of PCL core, pH‐sensitive PDEA mesosphere and poly (ethylene glycol) methyl ether methacrylate (PPEGMA) shell. When decreasing pH from 7.4 to 5.0, the hydrodynamic diameter and transmittance of (PCL)2(PDEA‐b‐PPEGMA)2 micelles increased along with globule‐uneven‐extended conformational transitions, owing to the protonation of tertiary amine groups of DEA at lower pH conditions. Doxorubicin (DOX) was mainly loaded in the pH‐sensitive layer, and more DOX were loaded in the core when increasing drug concentrations. The in vitro DOX release from the micelles was significantly accelerated by decreasing pH from 7.4 to 5.0. The results demonstrated that the pH‐sensitive micelles could be used as an efficient carrier for hydrophobic anticancer drugs, achieving controlled and sustained drug release. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3634–3646, 2014 相似文献