Gene/Protein Disease Symptom Drug Enzyme Compound
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 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly(N-isopropylacrylamide) (PNIPAM) microgel particles dispersed in water have been used as a matrix for the polymerization of a hydrophobic monomer, N-methylpyrrole (MPy). The presence of poly(MPy) (PMPy) within the dried composite particles has been confirmed using electron paramagnetic resonance (EPR) measurements which show a characteristic free-radical signal at g=2.007. Electron microscopy data (TEM) show that the composite PNIPAM-xPMPy particles have a "raspberry-like" morphology. (The value for x represents the volume percent of MPy added during synthesis with respect to the total microgel volume.) PCS data indicate that PMPy occupies the majority of the collapsed composite particle volume. The maximum value of x consistent with colloid stability for PNIPAM-xPMPy dispersions is 4.5%. Higher values of x result in coagulation due to interparticle bridging by PMPy. Variable temperature PCS measurements of the PNIPAM-xPMPy dispersions have been used to study the thermally induced collapse of the composite particles. The extent of collapse becomes less with increasing values for x. The embedded PMPy particles restrict the extent of PNIPAM network contraction. The stability of the PNIPAM-4.5PMPy dispersions was investigated by means of turbidity measurements using aqueous 0.1 M NaCl solution. The upper critical flocculation temperatures (UCFT) for PNIPAM and PNIPAM-4.5PMPy dispersions were identical (38-39 degrees C). The flocculation observed was found to be fully reversible. The composite dispersion stability in the absence of salt was attributed to electrosteric stabilization afforded by the PNIPAM matrix. These results indicate that PNIPAM microgel particles may have application as a matrix for the polymerization of hydrophobic monomers in water. Copyright 2000 Academic Press.
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PMID:Microgel Particles as a Matrix for Polymerization: A Study of Poly(N-isopropylacrylamide)-Poly(N-methylpyrrole) Dispersions. 1065 27

Polymeric micelles made of copolymer of N-isopropylacrylamide (NIPAAM), vinyl pyrrolidone (VP) and acrylic acid (AA) having cross-linkage with N,N'-methylene bis-acrylamide (MBA) were used as host carrier in which up to 30%w/w ketorolac (free acid) was entrapped to make the formulation. The lyophilised powder was used for physical characterisation. The drug entrapment was found to be about 80% and the formulation was stable for 8-10 days at room temperature. The smaller the amount of ketorolac dissolved into the micelles, the longer was the formulation shelf life. The size of the particles as measured by dynamic light scattering was found to be around 35 nm diameter at 25 degrees C. TEM picture showed spherical particles. The structure of the polymer and its morphology were characterised by FTIR, NMR and XRD measurements. IR data indicated weak interaction between polymer and ketorolac in the encapsulated system. NMR spectra indicated rigid polymer backbone with intermittent iso-propyl group in the chain. XRD spectra showed significant loss of crystallinity of the drug while being entrapped in the polymeric micelles. The release of drug in aqueous buffer (pH 7.2) from the polymeric micelles at 25 degrees C were 20 and 60% after 2 and 8 h respectively and is temperature and pH dependent. In vitro corneal permeation studies through excised rabbit cornea indicated two fold increase in ocular availability with no corneal damage compared to an aqueous suspension containing same amount of drug as in nanoparticles. The formulation showed significant inhibition of lid closure up to 3 h and PMN migration up to 5 h compared to the suspension containing non-entrapped drug, which did not show any significant effect.
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PMID:Ketorolac entrapped in polymeric micelles: preparation, characterisation and ocular anti-inflammatory studies. 1108 41

Thermally responsive amphiphilic poly(N-isopropylacrylamide) (PNIPAm)-grafted-polyphosphazene (PNIPAm-g-PPP) was synthesized by stepwise cosubstitution of chlorine atoms on polymer backbones with amino-terminated NIPAm oligomers and ethyl glycinate (GlyEt). Polymer structure was confirmed by FT-IR, (1)H NMR, elemental analysis, and GPC. The thermosensitivity of PNIPAm-g-PPP aqueous solution was investigated by turbidity method. The lower critical solution temperature (LCST) of PNIPAm-g-PPP was observed to be approximately 30 degrees C in water, while it was 24 degrees C in 0.1M PBS (pH 7.4). Micellization behavior of PNIPAm-g-PPP in aqueous solution was characterized by fluorescence probe technique, TEM, and DLS. The critical micelle concentration (CMC), thus, determined was 0.0187 g/L. Both TEM and DLS measurement suggested that the diameter of micelles was approximately 190 nm at 20 degrees C. Diflunisal (DIF)-loaded micelles were prepared by dialysis method. In vitro release test at various temperatures was also performed to study the effect of temperature on the drug release profiles. It was demonstrated that DIF release from PNIPAm-g-PPP micelles was slower at the temperature of 37 degrees C than that at 4 degrees C.
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PMID:Thermally responsive polymeric micelles self-assembled by amphiphilic polyphosphazene with poly(N-isopropylacrylamide) and ethyl glycinate as side groups: polymer synthesis, characterization, and in vitro drug release study. 1634 95

We report a study of colloidal thermosensitive core-shell particles by cryo-transmission electron microscopy (cryo-TEM). The particles consist of a solid core of poly(styrene), onto which a network of cross-linked poly(N-isopropylacrylamide) (PNIPAM) is affixed. In water, the shell of these particles swells when the temperature is low. Raising the temperature above 32 degrees C leads to a marked shrinking of the shell. In this letter, we present the first study of these core-shell particles by cryo-TEM in situ, that is, in aqueous solution. We demonstrate that the core-shell particles are well-defined and exhibit a narrow size distribution. In particular, the PNIPAM shell is compact and has a defined outer surface of a slightly irregular shape. The micrographs show that there are density fluctuations within the network. Cryo-TEM of the system above and below the transition temperature furnishes information about the thermosensitive particles that had not been available through other methods employed in previous investigations.
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PMID:Imaging the volume transition in thermosensitive core-shell particles by cryo-transmission electron microscopy. 1651 27

Thermally sensitive micelles self-assembled from poly(N-isopropylacrylamide-co- N,N-dimethylacrylamide)-b-poly(d,l-lactide-co-glycolide)[P(NIPAAm-co-DMAAm)-b-PLGA] are fabricated and used as a carrier for the controlled delivery of paclitaxel. Paclitaxel is efficiently loaded into the micelles by a membrane dialysis method. The lower critical solution temperature (LCST) of the micelles is 39.0 degrees C in PBS. Encapsulation efficiency and loading level of paclitaxel are affected by the initial loading level of paclitaxel, fabrication temperature and polymer composition. The blank and paclitaxel-loaded micelles are characterized by particle size analysis (DLS), morphology (TEM and AFM) and paclitaxel distribution (NMR, DSC and WAXRD). The micelles are spherical in shape, having an average size less than 130 nm. Paclitaxel is molecularly distributed within the core of micelles. Sustained release of paclitaxel is achieved, which is much faster at a temperature above the LCST than at the normal body temperature (37 degrees C). Cytotoxicity of free paclitaxel and paclitaxel-loaded micelles against a human breast carcinoma cell line (MDA-MB-435S) is studied at different temperatures. The cytotoxicity of the paclitaxol-loaded micelles is greater as compared to free paclitaxel. Enhanced cytotoxicity is achieved by the paclitaxol-loaded micelles when the environmental temperature increases slightly above the LCST. Paclitaxel-loaded P(NIPAAm-co-DMAAm)-b-PLGA micelles may provide a good formulation for cancer therapy.
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PMID:Thermally sensitive micelles self-assembled from poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)-b-poly(D,L-lactide-co-glycolide) for controlled delivery of paclitaxel. 1688 Sep 79

N-Isopropylacrylamide and allylamine copolymers (PNIALM) were prepared by radical polymerization method. To endow them with arginine-like cell membrane penetrating function, the aminos in PNIALMs were transformed to guanidinium groups by chemical modification. The formation and guanidinylation PNIALM were confirmed by NMR; the composition of copolymers and the degree of substitution of guanidino in modified copolymer (PNIALM-G) were estimated as well. The electrophoretic assay revealed that PNIALM-G was capable of condensing DNA in spite of lower binding affinity compared to its parent copolymers. The results of particle size analyzer and TEM indicated that at higher copolymer/DNA weight ratios, the copolymer/DNA complexes were condensed to nanoparticles. PNIALM-G1-3 was shown to be very efficient in mediating plasmid DNA transfection to COS-1 cells both in the presence and absence of serum, even superior to PEI.
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PMID:Guanidinylated allylamine-N-isopropylacrylamide copolymer nonviral transgene vectors. 1704 64

The core-shell gold nanoparticles and copolymer of N-isopropylacrylamide (NIPAM) and N,N'-methylenebisacrylamide (MBAA) hybrids (Au@copolymer) were fabricated through surface-initiated atom-transfer radical polymerization (ATRP) on the surface of gold nanoparticles in 2-propanol/water mixed solvents. The surface of citrate-stabilized gold nanoparticles was first modified by a disulfide initiator for ATRP. The slight cross-linking polymerization between NIPAM and MBAA occurred on the gold surface and resulted in the formation of core-shell Au@copolymer nanostructures that were characterized by TEM, and FTIR and UV-visible spectroscopy. Such synthesized Au@copolymer hybrids possess clearly thermosensitive properties and exhibit "inspire" and "expire" water behavior in response to temperature changes in aqueous solution. Because of this property, we enable to trap and encapsulate smaller nanoparticles by using the free space of the copolymer-network scaffold anchored at the gold surface.
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PMID:Thermosensitive copolymer networks modify gold nanoparticles for nanocomposite entrapment. 1715 19

Micro-capsules normally encapsulate therapeutic agents only inside their cavities. In this paper, we report on the synthesis of dually responsive poly(N-isopropylacrylamide) (PNiPAM)-co-acrylic acid (AA) hydrogel cages sub-micrometer in size and the use of these cages as drug carriers. The cavity structure of the cages can enhance volume phase transition compared to solid gel particles, thus favoring drug loading and release. TEM images and FT-IR spectra confirmed that the model drug isoniazid (INH) is located in two regions: within the shell and inside the cavity of the cages. The drugs residing in the shell can form hydrogen bonds with the cage matrix, while the drugs in the cavity are interaction free with the carrier. This difference from the residency of drugs exploited to a structure induced drug release which was programmable controlled by external pH and temperature. In vitro drug release studies showed that in a neutral medium (pH=7.4), major drugs were preserved within the shell, while in an acidic medium (pH=1.2), nearly all of the drugs were released due to the dissociation of hydrogen bonds.
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PMID:Programmable delivery of hydrophilic drug using dually responsive hydrogel cages. 1723 81

A novel thermosensitive amphiphilic graft copolymer PNIPAAm-g-PCbzEA appending carbazole group was successfully designed and synthesized by the free radical copolymerization of N-isopropylacrylamide with hydrophobic precursor polymers of vinyl-functionalized poly(2-(N-carbazolyl)ethyl acrylate) (PCbzEA) in DMF. The PNIPAAm-g-PCbzEA copolymer was characterized by FTIR, (1)H NMR, GPC analysis, UV-vis spectroscopy and fluorescence spectroscopy. The TEM observation shows that the graft copolymer may self-assemble into polymeric micelles exhibiting a nanospheric morphology within a narrow size range of 30-60 nm in aqueous solution. From the (1)H NMR and FTIR analysis, the polymer micelles are composed of hydrophobic PCbzEA segments as the cores and the hydrophilic PNIPAAm segements as outer shells. The resulting micelles exhibited the temperature sensitivity with a lower critical solution temperature (LCST) of 31.5 degrees C and a critical micelle concentration (CMC) of 12.9 mg/L in water. In the study of drug release, an "on-off" drug release profile was found in response to stepwise temperature changes between 20 and 40 degrees C. The cytotoxicity assays for vero cells shows good biocompatibility of the graft copolymer in vitro.
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PMID:Self-assembled, fluorescent polymeric micelles of a graft copolymer containing carbazole for thermo-controlled drug delivery in vitro. 1797 88

A two-stage precipitation polymerization in aqueous solution was used to prepare beta-cyclodextrin/poly(N-isopropylacrylamide) (beta-CD/PNIPAm) core-shell microgels. At the first stage, core microgels with CD moieties were synthesized by precipitation copolymerization of N-isopropylacrylamide (NIPAm) with a monovinyl beta-CD monomer. At the second stage, using the core particles as seeds, PNIPAm shell were further added onto the seeds by NIPAm polymerization. The microgels were characterized by means of Zetasizer Nano-ZS dynamic light scattering, TEM, IR, NMR, DSC, and TGA measurements. Using paeonol as a model drug molecule, the release behaviors of the microgels were investigated. The result indicates that the core-shell microgels could respond to change in temperature. Furthermore, the release of paeonol was related to supramolecular inclusion behavior of beta-CD and temperature sensitivity of PNIPAm.
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PMID:Preparation and properties of cyclodextrin/PNIPAm microgels. 1910 19


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