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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heparin has been widely investigated in medicine and biomedical applications as an anticoagulant. This paper described a covalent modification of poly (lactic acid) (PLA) films with heparin-carrying microcapsules. The heparin-carrying microcapsules were achieved by layer-by-layer (LbL) self-assembly technology by which poly (allylamine hydrochloride) (PAH) and heparin were alternately coated on the Ca(2+)-cross-linked alginate hydrogel. The microcapsules were characterized by scanning electron microscopy (SEM), zeta potential analysis and Fourier transform infrared spectroscopy (FTIR), and then grafted to PLA films by -CONH- linkage between surface PLA molecules with residual primary amino groups on the outer PAH layer of microcapsules, in the presence of catalysts of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). SEM and FTIR revealed the formation of -CONH- linkage. In vitro antithrombogenicity by the method of the activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) tests showed that surface-modified PLA films had superior coagulation properties to original PLA films. It is suggested that the present method would provide a potential effective tool for biomaterial modification.
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PMID:Construction of anticoagulant poly (lactic acid) films via surface covalent graft of heparin-carrying microcapsules. 1915 61

Poly(lactic acid) (PLA) microparticles were coated with layer-by-layer (LbL) films containing insulin and the pH-dependent release of insulin was studied. The LbL films were prepared on the surface of PLA microparticles by the alternate deposition of insulin and poly(allylamine hydrochloride) (PAH) through the electrostatic attraction between insulin and PAH. The insulin loading on the PLA microparticles depended on the film thickness, which corresponded to the number of insulin layers, and on the pH of the solution used to deposit insulin. The insulin loading increased with the film thickness and when the film was prepared at pH 7.4. The LbL films decomposed upon exposure to acidic solutions because the electrostatic attraction between the insulin and the PAH in the films disappeared when the charge on insulin changed from negative to positive at an acidic pH, which resulted in the release of insulin. The temperature and salt concentration did not affect the pH stability of the LbL films. The pH threshold for insulin release was pH 5.0-6.0, which corresponds to isoelectric point of insulin, 5.4. The release of insulin from the microparticles was rapid, and was almost complete within a few minutes. The circular dichroism spectra showed that the released insulin retained its original secondary structure. Our insulin-loaded PLA microparticles may be useful for the controlled release of insulin.
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PMID:Poly(lactic acid) microparticles coated with insulin-containing layer-by-layer films and their pH-dependent insulin release. 2473 41

Functional thin films containing insulin were prepared using layer-by-layer (LbL) deposition of insulin and negatively- or positively-charged polymers on the surface of solid substrates. LbL films composed of insulin and negatively-charged polymers such as poly(acrylic acid) (PAA), poly(vinylsulfate) (PVS), and dextran sulfate (DS) were prepared through electrostatic affinity between the materials. The insulin/PAA, insulin/PVS, and insulin/DS films were stable in acidic solutions, whereas they decomposed under physiological conditions as a result of a change in the net electric charge of insulin from positive to negative. Interestingly, the insulin-containing LbL films were stable even in the presence of a digestive-enzyme (pepcin) at pH 1.4 (stomach pH). In contrast, LbL films consisting of insulin and positively-charged polymers such as poly(allylamine hydrochloride) (PAH) decomposed in acidic solutions due to the positive charges of insulin generated in acidic media. The insulin-containing LbL films can be prepared not only on the surface of flat substrates, such as quartz slides, but also on the surface of microparticles, such as poly(lactic acid) (PLA) microbeads. Thus, insulin-containing LbL film-coated PLA microbeads can be handled as a powder. In addition, insulin-containing microcapsules were prepared by coating LbL films on the surface of insulin-doped calcium carbonate (CaCO3) microparticles, followed by dissolution of the CaCO3 core. The release of insulin from the microcapsules was accelerated at pH 7.4, whereas it was suppressed in acidic solutions. These results suggest the potential use of insulin-containing microcapsules in the development of oral formulations of insulin.
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PMID:Development of Functional Thin Polymer Films Using a Layer-by-Layer Deposition Technique. 2896 62