RESUMO
Amino-bearing polymers, coated with apatite or similar minerals, have attracted significant attention for their potential in medical applications. In this study, an amino-terminated hyperbranched polybenzimidazole (HBPBI) membrane was used as a substrate for apatite growth. The membrane was soaked in solutions of CaCl2, Na2HPO4 and SBF to yield an apatite coating. The structure and morphology of the layers were characterized by FTIR-ATR, XRD and FESEM. The results indicate that the high densities of amino, imide and imidazole groups on the amino-terminated HBPBI membrane provide active sites for the growth of apatite.
Assuntos
Polímeros/química , Apatitas/análise , Apatitas/química , Polímeros/análise , Soluções/análise , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
A novel technique of simultaneous peptide enrichment and wash-free in-situ self-desalting for MALDI analysis is reported, where a newly synthesized block copolymer with a microphase-separated configuration is applied to embed salts with its hydrophilic domain of poly(ethylene oxide) and concentrate peptides with its hydrophobic domain of polysulfone.
Assuntos
Mioglobina/química , Peptídeos/química , Polietilenoglicóis/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Sulfonas/química , Bicarbonatos/química , Ácidos Cólicos/química , Dodecilsulfato de Sódio/químicaRESUMO
The transport of lithium ions in cation-exchange membranes based on sulfonated copolyimide membranes is reported. Diffusion coefficients of lithium are estimated as a function of the water content in membranes by using pulsed field gradient (PFG) NMR and electrical conductivity techniques. It is found that the lithium transport slightly decreases with the diminution of water for membranes with water content lying in the range 14 < λ < 26.5, where λ is the number of molecules of water per fixed sulfonate group. For λ < 14, the value of the diffusion coefficient of lithium experiences a sharp decay with the reduction of water in the membranes. The dependence of the diffusion of lithium on the humidity of the membranes calculated from conductivity data using Nernst-Planck type equations follows a trend similar to that observed by NMR. The possible explanation of the fact that the Haven ratio is higher than the unit is discussed. The diffusion of water estimated by (1)H PFG-NMR in membranes neutralized with lithium decreases as λ decreases, but the drop is sharper in the region where the decrease of the diffusion of protons of water also undergoes considerable reduction. The diffusion of lithium ions computed by full molecular dynamics is similar to that estimated by NMR. However, for membranes with medium and low concentration of water, steady state conditions are not reached in the computations and the diffusion coefficients obtained by MD simulation techniques are overestimated. The curves depicting the variation of the diffusion coefficient of water estimated by NMR and full dynamics follow parallel trends, though the values of the diffusion coefficient in the latter case are somewhat higher. The WAXS diffractograms of fully hydrated membranes exhibit the ionomer peak at q = 2.8 nm(-1), the peak being shifted to higher q as the water content of the membranes decreases. The diffractograms present additional peaks at higher q, common to wet and dry membranes, but the peaks are better resolved in the wet membranes. The ionomer peak is not detected in the diffractograms of dry membranes.
Assuntos
Lítio/química , Naftalenos/química , Resinas Sintéticas/química , Água/química , Cátions/química , DifusãoRESUMO
A series of poly(ethylene oxide) (PEO) segmented polysulfone copolymers with different PEO content has been successfully synthesized via condensation polymerization of 4,4'-dichlorodiphenylsulfone (DCDPS), chlorine-end-capped poly(ethylene oxide) (PEO-Cl(2))) and 4,4'-dihydroxybiphenyl (DHBP) in N,N-dimethylacetamide (DMAc) in the presence of anhydrous potassium carbonate at 160 degrees C for 20 h. The resulting copolymers showed high molecular weights (Mn=28,000-40,200 Da) and relatively narrow molecular weight distributions (Mw/Mn=1.57-1.87). They are well soluble in common organic solvents such as chloroform and tetrahydrofuran. Films with high tensile strength (38-50 MPa) and good elasticity of elongation (elongation at break: 190-430%) were prepared by solution cast from the copolymer solutions in chloroform. Sirolimus and paclitaxel were used as drugs and their release kinetics were investigated. For both drugs, the release rate was strongly influenced by the PEO content of the polymer films, i.e., PSF-PEO films with higher PEO content showed larger drug release rate. Film swelling due to liquid sorption is mainly responsible for the drug release.