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1.
Polymers with multiple tunable responses were achieved by incorporating boronic acid functionality along the backbone of a thermoresponsive polymer. The inherent Lewis acidity and diol‐sensitivity of boronic acid moieties allowed these polymers to respond to changes in pH and glucose concentration. Through reversible addition‐fragmentation chain transfer copolymerization of boronic acid‐containing monomers with N‐isopropylacrylamide, well‐defined block copolymers were synthesized containing a hydrophilic N,N‐dimethylacrylamide block and a second, responsive block with temperature‐dependent water solubility, making the resulting polymers capable of self‐assembly into nanostructures upon heating. By incorporating boronic acids within the thermoresponsive block, the cloud point of the polymer depended on the solution conditions, including pH and diol concentration, allowing tunable cloud point ranges. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2309–2317  相似文献   

2.
Starburst triblock copolymers consisting of 8‐arm poly(ethylene glycol) (8‐arm PEG) and biodegradable poly(L ‐lactide) (PLLA) or its enantiomer poly(D ‐lactide) (PDLA), 8‐arm PEG‐b‐PLLA‐b‐PEG ( Stri‐L ), and 8‐arm PEG‐b‐PDLA‐b‐PEG ( Stri‐D ) were synthesized. An aqueous solution of a 1:1 mixture ( Stri‐Mix ) of Stri‐L and Stri‐D assumed a sol state at room temperature, but instantaneously formed a physically crosslinked hydrogel in response to increasing temperature. The resulting hydrogel exhibited a high‐storage modulus (9.8 kPa) at 37 °C. Interestingly, once formed at the transition temperature, the hydrogel was stable even after cooling below the transition temperature. The hydrogel formation process was irreversible because of the formation of stable stereocomplexes. In aqueous solution, gradual hydrolytic erosion was observed because of degradation of the hydrogel. The combination of rapid temperature‐triggered irreversible hydrogel formation, high‐mechanical strength, and degradation behavior render this polymer mixture system suitable for use in injectable biomedical materials, for example, as a drug delivery system for bioactive reagents or a biodegradable scaffold for tissue engineering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6317–6332, 2008  相似文献   

3.
With diabetes mellitus becoming an important public health concern, insulin‐delivery systems are attracting increasing interest from both scientific and technological researchers. This feature article covers the present state‐of‐the‐art glucose‐responsive insulin‐delivery system (denoted as GRIDS), based on responsive polymer materials, a promising system for self‐regulated insulin delivery. Three types of GRIDS are discussed, based on different fundamental mechanisms of glucose‐recognition, with: a) glucose enzyme, b) glucose binding protein, and c) synthetic boronic acid as the glucose‐sensitive component. At the end, a personal perspective on the major issues yet to be worked out in future research is provided.  相似文献   

4.
Glucose responsive block copolymer featuring boronic acid as a glucose responsive moiety and glycine are reported. The first block is polymerized through reversible addition–fragmentation chain transfer (RAFT) polymerization and the resulting poly(N‐acryloylmorpholine)113 (PAcM) is employed as a macro‐chain transfer agent for chain extension with pentafluorophenyl acrylate (PFPA) yielding a well‐defined PAcM113block‐poly(pentafluorophenyl acrylate)84 (PPFPA). The PPFPA block is then reacted with functional (3‐aminomethyl) phenyl boronic acid and glycine via post‐polymerization modification and the structure of the block copolymer is confirmed by proton nuclear magnetic resonance (NMR), 19F NMR, Fourier transform infrared, and gel permeation chromatography. By copolymerizing glycine into the polymer backbone, the relative pKa of the block copolymer is significantly lowered. The block copolymer can self‐assemble into core–shell micelles in aqueous solution and disassemble in response to glucose at the physiological pH. Furthermore, the encapsulation and release of Nile red (NR) as a hydrophobic model drug is studied under the physiological pH. The influence of the glucose concentration on the NR release from the polymeric micelles is demonstrated. These results suggested that the glucose‐responsive poly[(AcM)113b‐(3‐(aminomethyl)phenylboronic acid hydrochloride(‐co‐Gly)84] block copolymer has potential applications as a glucose‐responsive polymer for insulin delivery. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 422–431  相似文献   

5.
Thermoresponsive, biodegradable polymeric hydrogel networks are used widely in medicinal applications. Poly(d ,l ‐lactic acid‐co‐glycolic acid)‐b‐poly(ethylene glycol)‐b‐poly(d ,l ‐lactic acid‐co‐glycolic acid) (PLGA‐PEG‐PLGA) triblock copolymers exhibit a sol–gel transition upon heating. The effect of PLGA block and PEG chain molecular weights (MWs) on the gelling temperature of polymer aqueous solution (20% w/w) is described. All polymer solutions convert into a hard gel within 2 °C of the gelling temperature. The release properties of the gels were displayed using paracetamol as a representative drug. A linear relation is described between the gelling temperature and PLGA block MW. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 35–39  相似文献   

6.
A new type of glucose‐responsive hydrogel with rapid response to blood glucose concentration change at physiological temperature has been successfully developed. The polymeric hydrogel contains phenylboronic acid (PBA) groups as glucose sensors and thermo‐responsive poly (N‐isopropylacrylamide) (PNIPAM) groups as actuators. The response rate of the hydrogel to environmental glucose concentration change was significantly enhanced by introducing grafted poly(N‐isopropylacrylamide‐co‐3‐acrylamidophenylboronic acid) [poly(NIPAM‐co‐AAPBA)] side chains onto crosslinked poly(NIPAM‐co‐AAPBA) networks for the first time. The synthesized comb‐type grafted poly(NIPAM‐co‐AAPBA) hydrogels showed satisfactory equilibrium glucose‐responsive properties, and exhibited much faster response rate to glucose concentration change than normal type crosslinked poly(NIPAM‐co‐AAPBA) hydrogels at physiological temperature. Such glucose‐responsive hydrogels with rapid response rate are highly attractive in the fields of developing glucose‐responsive sensors and self‐regulated drug delivery systems. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

7.
The insulin therapy constitutes the preferred treatment for Diabetes Mellitus (DM). The traditional insulin therapy, which consists of daily subcutaneous insulin injections to control blood glucose level, is not able to regulate the blood glucose level precisely. In this research, to facilitate the diabetic patient life, an intelligent drug delivery system based on a biodegrable biopolymer to control the insulin release, was designed. In this system, chitosan‐polyethylene glycol hydrogel and glucose oxidize play the role of drug carrier and glucose biosensor, respectively. To increase the hydrogel drug loading capacity, hydrogels with different PEG content were synthesized and insulin was loaded by swelling‐diffusion method into them. The loaded hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), High performance liquid chromatography (HPLC), and Thermogravimetric analysis (TGA). Finally, the thermodynamic study for insulin loading process was performed to investigate the stability of the drug in the system.  相似文献   

8.
Herein, we report a new drug‐delivery system (DDS) that is comprised of a near‐infrared (NIR)‐light‐sensitive gold‐nanorod (GNR) core and a phase‐changing poly(ε‐caprolactone)‐b‐poly(ethylene glycol) polymer corona (GNR@PCL‐b‐PEG). The underlying mechanism of the drug‐loading and triggered‐release behaviors involves the entrapment of drug payloads among the PCL crystallites and a heat‐induced phase change, respectively. A low premature release of the pre‐loaded doxorubicin was observed in PBS buffer (pH 7.4) at 37 °C (<10 % of the entire payload after 48 h). However, release could be activated within 30 min by conventional heating at 50 °C, above the Tm of the crystalline PCL domain (43.5 °C), with about 60 % release over the subsequent 42 h at 37 °C. The NIR‐induced heating of an aqueous suspension of GNR@PCL‐b‐PEG under NIR irradiation (802 nm) was investigated in terms of the irradiation period, power, and concentration‐dependent heating behavior, as well as the NIR‐induced shape‐transformation of the GNR cores. Remotely NIR‐triggered release was also explored upon NIR irradiation for 30 min and about 70 % release was achieved in the following 42 h at 37 °C, with a mild warming (<4 °C) of the surroundings. The cytotoxicity of GNR@PCL‐b‐PEG against the mouse fibroblastic‐like L929 cell‐line was assessed by MTS assay and good compatibility was confirmed with a cell viability of over 90 % after incubation for 72 h. The cellular uptake of GNR@PCL‐b‐PEG by melanoma MEL‐5 cells was also confirmed, with an averaged uptake of 1250(±110) particles cell?1 after incubation for 12 h (50 μg mL?1). This GNR@PCL‐b‐PEG DDS is aimed at addressing the different requirements for therapeutic treatments and is envisaged to provide new insights into DDS targeting for remotely triggered release by NIR activation.  相似文献   

9.
We developed a carbohydrate sensing material, which consists of a crystalline colloidal array (CCA) incorporated into a polyacrylamide hydrogel (PCCA) with pendent boronic acid groups. The embedded CCA diffracts visible light, and the PCCA diffraction wavelength reports on the hydrogel volume. This boronic acid PCCA responds to species containing vicinal cis diols such as carbohydrates. This PCCA photonic crystal sensing material responds to glucose in low ionic strength aqueous solutions by swelling and red shifting its diffraction as the glucose concentration increases. The hydrogel swelling results from a Donnan potential due to formation of boronate anion; the boronic acid pK(a) decreases upon glucose binding. This sensing material responds to glucose and other sugars at <50 microM concentrations in low ionic strength solutions.  相似文献   

10.
DNA‐tethered poly‐N‐isopropylacrylamide copolymer chains, pNIPAM, that include nucleic acid tethers have been synthesized. They are capable of inducing pH‐stimulated crosslinking of the chains by i‐motif structures or to be bridged by Ag+ ions to form duplexes. The solutions of pNIPAM chains undergo crosslinking at pH 5.2 or in the presence of Ag+ ions to form hydrogels. The hydrogels reveal switchable hydrogel‐to‐solution transitions by the reversible crosslinking of the chains at pH 5.2 and the separation of the crosslinking units at pH 7.5, or by the Ag+ ion‐stimulated crosslinking of the chains and the reverse dissolution of the hydrogel by the cysteamine‐induced elimination of the Ag+ ions. The DNA‐crosslinked hydrogels are thermosensitive and undergo reversible temperature‐controlled hydrogel‐to‐solid transitions. The solid pNIPAM matrices are protected against the OH? or cysteamine‐stimulated dissociation to the respective polymer solutions.  相似文献   

11.
In this study, we immobilized enzymes by combining covalent surface immobilization and hydrogel entrapment. A model enzyme, glucose oxidase (GOX), was first covalently immobilized on the surface of silica nanoparticles (SNPs) via 3‐aminopropyltriethoxysilane (APTES), and the resultant SNP‐immobilized enzyme was physically entrapped within photopolymerized hydrogels prepared from two different molecular weights (MWs) (575 and 8000 Da) of poly(ethylene glycol)(PEG). The hydrogel entrapment resulted in a decrease in reaction rate and an increase in apparent Km of SNP‐immobilized GOX, but these negative effects could be minimized by using hydrogel with a higher MW PEG, which provides higher water content and larger mesh size. The catalytic rate of the PEG 8000 hydrogel was about ten times faster than that of the PEG 575 hydrogel because of enhanced mass transfer. Long‐term stability test demonstrated that SNP‐immobilized GOX entrapped within hydrogel maintained more than 60% of its initial activity after a week, whereas non‐entrapped SNP‐immobilized GOX and entrapped GOX without SNP immobilization maintained less than 20% of their initial activity. Incorporation of SNPs into hydrogel enhanced the mechanical strength of the hydrogel six‐fold relative to bare hydrogels. Finally, a hydrogel microarray entrapping SNP‐immobilized GOX was fabricated using photolithography and successfully used for quantitative glucose detection. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

12.
A novel multifunctional amphiphilic graft copolymer has been synthesized consisting of a biodegradable poly(l ‐aspartic acid) backbone that was decorated by water‐soluble poly(ethylene glycol) (PEG) and pH‐responsive poly(N,N‐diethylaminoethyl methacrylate) (PDEAEMA) side‐chains as well as thiol pendant groups. This graft copolymer together with doxorubicin (DOX) formed micelles in water at pH = 10.0 with PDEAEMA and DOX acting as the core and PEG serving as the micellar corona. Upon oxidation, the thiol groups dimerized to form disulfide bonds, thus “locking in” the micellar structure. These crosslinked micelles expanded as the pH was decreased from 7.4 to 5.0 or upon the addition, at pH = 7.4, of glutathione (GSH), a thiol‐containing oligopeptide that is present in cancerous cells and cleaves disulfide bonds. At pH = 5.0, GSH addition triggered the disassembly of the micelles. The expansion and disassembly of the micelles have been determined via in vitro experiments to evaluate their DOX release behavior. More importantly, the graft copolymer micelles could enter cells by means of endocytosis and deliver DOX to the nuclei of ovarian cancer BEL‐7402 cells. Thus, this polymer and its micelles are promising candidates for drug delivery applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1536–1546  相似文献   

13.
Copolymer networks of poly(methacrylic acid) (PMAA) and poly(ethylene glycol) (PEG) exhibit large changes in their swelling behavior over a narrow pH range due to the reversible formation/dissociation of interpolymer complexes between the polymer chains. Intepolymer complexation occurs in copolymer gels of PMAA and PEG due to hydrogen bonding between protonated acid groups and the ether groups of the PEG. Because of their nature, these gels have been identified for use as delivery vehicles for macromolecular drugs. In this work, solid‐state, nuclear magnetic resonance nuclear Overhauser enhancement (NOE) experiments were performed to detect the molecular level complexation between PMAA and deuterated PEG in copolymer blends and crosslinked networks. For gels swollen in acidic media at room temperature or at 37 °C, strong enhancements were detected in the 13C resonance of the PEG carbons. The NOE was generated due to energy transfer between the rapidly rotating methyl group protons and the deuterated PEG carbons. The presence of the NOE was indicative of close packing of the polymer chains and was evidence of the presence of the intermacromolecular complexes. In basic solutions, no NOE was detected in the PEG, as the complexes were dissociated and the chains were separated in space. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2823–2831, 2000  相似文献   

14.
A novel polymer complex system sensitive to glucose was studied as a candidate material for formulating a chemically regulated insulin release system. A ternary copolymer of N-vinyl-2-pyrrolidone (NVP), 3-acrylamidophenylboronic acid (AAm-PBA) and N,N-dimethylaminopropylacrylamide (DMAPAA) (poly(NVP-co-PBA-co-DMAPAA)) was synthesized by radical copolymerization. The phenylboronic acid group in this copolymer serves as a glucose sensor moiety. Poly(NVP-co-PBA-co-DMAPAA) was soluble in water in the pH range of 3–12, in sharp contrast to a binary copolymer of NVP and AAm-PBA (poly(NVP-co-PBA)) which showed solubility only under alkaline aqueous conditions, where the boronic acid group is in a tetrahedral ionized form. The protonated amino group in poly(NVP-co-PBA-DMAPAA) contributed to increase the solubility of the polymer under physiological and acidic aqueous conditions. Furthermore, poly(NVP-co-PBA-co-DMAPAA) formed a stable polymer complex gel with poly(vinyl alcohol) (PVA) in pH 7.4 phosphate buffered solution due to the formation of a covalent linkage between the boronic acid groups in ternary copolymer and diol units in PVA. The release of myoglobin as model protein from the complex gel was increased immediately after the addition of glucose, due to the transition of gel into sol state, indicating the feasibility of this complex gel as a candidate material for a glucose-responsive delivery system for insulin.  相似文献   

15.
A hetero‐arm star polymer, poly(ethylene glycol)‐poly(N‐isopropylacrylamide)‐poly(L‐lysine) (PEG‐PNIPAM‐PLys), was synthesized by “clicking” the azide group at the junction of PEG‐b‐PNIPAM diblock copolymer with the alkyne end‐group of poly(L‐lysine) (PLys) homopolymer via 1,3‐dipolar cycloaddition. The resultant polymer was characterized by gel permeation chromatography, proton nuclear magnetic resonance, and Fourier transform infrared spectroscopes. Surprisingly, the PNIPAM arm of this hetero‐arm star polymer nearly lose its thermal responsibility. It is found that stable polyelectrolyte complex micelles are formed when mixing the synthesized polymer with poly(acrylic acid) (PAA) in water. The resultant polyelectrolyte complex micelles are core‐shell spheres with the ion‐bonded PLys/PAA chains as core and the PEG and PNIPAM chains as shell. The PNIPAM shell is, as expected, thermally responsive. However, its lower critical solution temperature is shifted to 37.5 °C, presumably because of the existence of hydrophilic components in the micelles. Such star‐like PEG‐PNIPAM‐PLys polymer with different functional arms as well as its complexation with anionic polymers provides an excellent and well‐defined model for the design of nonviral vectors to deliver DNA, RNA, and anionic molecular medicines. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1450–1462, 2009  相似文献   

16.
Hydrogel formation triggered by a change in temperature is an attractive mechanism for in situ gelling biomaterials for pharmaceutical applications such as the delivery of therapeutic proteins. In this study, hydrogels were prepared from ABA triblock polymers having thermosensitive poly(N-(2-hydroxypropyl) methacrylamide lactate) flanking A-blocks and hydrophilic poly(ethylene glycol) B-blocks. Polymers with fixed length A blocks (~22 kDA) but differing PEG-midblock lengths (2, 4 and 10 kDa) were synthesized and dissolved in water with dilute fluorescein isothiocyanate (FITC)-labeled dextrans (70 and 500 kDA). Hydrogels encapsulating the dextrans were formed by raising the temperature. Fluorescence recovery after photobleaching (FRAP) studies showed that diffusion coefficients and mobile fractions of the dextran dyes decreased upon elevating temperatures above 25 °C. Confocal laser scanning microscopy and cryo-SEM demonstrated that hydrogel structure depended on PEG block length. Phase separation into polymer-rich and water-rich domains occurred to a larger extent for polymers with small PEG blocks compared to polymers with a larger PEG block. By changing the PEG block length and thereby the hydrogel structure, mobility of FITC-dextran could be tailored. At physiological pH the hydrogels degraded over time by ester hydrolysis, resulting in increased mobility of the encapsulated dye. Since diffusion can be controlled according to polymer design and concentration, plus temperature, these biocompatible hydrogels are attractive as potential in situ gelling biodegradable materials for macromolecular drug delivery.  相似文献   

17.
The synthesis of a novel photoreactive poly(ethylene glycol) (PEG)‐based polymer with caged carbonyl groups is reported. We further demonstrate its use for the on‐demand fabrication of hydrogels. For rapid gelation, a hydrazide‐functionalized PEG is used as the second component for the hydrogel preparation. The photoreactive PEG‐based polymer is designed for controlled cleavage of the protecting groups upon exposure to UV light releases free aldehyde moieties, which readily react with hydrazide groups in situ. This hydrogel system may find applications in controlled release drug delivery applications, when combined with in situ gelation. Furthermore, the possibility of forming gels specifically upon UV irradiation gives an opportunity for 3D fabrication of degradable scaffolds.

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18.

In the present work a self‐regulated insulin delivery system based on the hydrogel poly(2‐hydroxyethyl methacrylate‐co‐N,N‐dimethylaminoethyl methacrylate) with entrapped glucose oxidase, catalase and insulin was developed and evaluated both by in vitro and in vivo studies. The hydrogels were characterized by FTIR, DSC, SEM and elemental analysis. The swelling studies were carried out in different pH and glucose solutions. The mesh size of the hydrogels and diffusion coefficient of water and insulin in different glucose solution was calculated. The effect of the crosslinking agent (ethylene glycol dimethacrylate) concentration (0–2% w/w) on swelling and insulin release was studied. The equilibrium swelling and insulin release was found to depend on the external glucose concentration and dimethylaminoethyl methacrylate content of the hydrogels. The in vivo studies indicated that the entrapped insulin was stable and was effective in reducing the blood glucose of streptozotocin induced diabetic rats. The histopathological studies revealed that there was no fibrous tissue encapsulation after 56 days of implantation.  相似文献   

19.
A pyrene‐containing phenylboronic acid (PBA) functionalized low‐molecular‐weight hydrogelator was synthesized with the aim to develop glucose‐sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8–12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL?1. The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π–π stacking, and van der Waals interactions are the key factors for the self‐assembled gelation. The diol‐sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose‐responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose‐induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin‐loaded hydrogel showed thixotropic self‐recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells.  相似文献   

20.
Amphiphilic self‐folding random copolymers exhibit different solution behaviors depending on the identity of the hydrophobic/hydrophilic units. Herein, it is demonstrated that changing the hydrophilic unit from poly(ethylene glycol) to the sugar trehalose causes increased discrepancy in the polarity difference with a fluorinated hydrophobic segment and changes the aggregation state of the polymer in water. The PEG‐fluorinated and trehalose/PEG‐fluorinated amphiphilic random copolymers were the most efficient at encapsulating a fluorinated agrochemical. The small‐molecule agrochemical exerts a strong influence on the self‐assembly of the polymers, demonstrating that fluorous interactions result in not only intramolecular self‐folding behavior but also intermolecular polymer association to form well‐defined nanoparticles. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 352–359  相似文献   

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