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Biomedical subjects

Xian-Fu Lin

Publications and source records attributed to Xian-Fu Lin.

12 recordsLinked to original sources
PubMed2006

Bioactive galactose-branched polyelectrolyte multilayers and microcapsules: self-assembly, characterization, and biospecific lectin adsorption.

We describe the fabrication of multilayers and microcapsules with biologically designed targeting activity using chemoenzymatic synthesized carbohydrate-branched polyelectrolytes. A novel cationic d-galactose-branched copolymer [poly(vinyl galactose ester-co-methacryloxyethyl trimethylammonium chloride), PGEDMC] is alternated with poly(styrene sulfonate) (PSS) to form thin multifilms by the layer-by-layer (LbL) technique on such different solid surfaces as quartz slides, poly(ethylene terephthalate) (PET) films, silicon wafers, and polystyrene (PS) microparticles. The experimental protocols were first optimized on flat, smooth silica substrates using UV-vis, contact angle, and atomic force microscopy (AFM) measurements. The film properties of PGEDMC/PSS multilayers are modified by varying polyelectrolyte concentration, ionic strength, and counteranion types. Hollow capsules were formed after the removal of colloidal templates; transmission (TEM) and scanning (SEM) electron microscopy were used to verify the LbL process integrity. PGEDMC/PSS planar films and capsules carrying beta-galactose as recognition signals have specific recognition abilities with peanut agglutinin (PNA) lectin rather than concanavalin A (Con A) lectin observed by fluorescence spectroscopy.

Adsorption↗
PubMed2006

Basic ionic liquid as catalysis and reaction medium: a novel and green protocol for the Markovnikov addition of N-heterocycles to vinyl esters, using a task-specific ionic liquid, [bmIm]OH.

A basic ionic liquid, 1-methyl-3-butylimidazolium hydroxide ([bmIm]OH), has been introduced as a catalyst and reaction medium for the Markovnikov addition of N-heterocycles to vinyl esters under mild conditions. The evidence for the role of this basic ionic liquid [bmIm]OH in promoting the Markovnikov addition has been given. On the basis of the evidence, a mechanism was postulated.

Journal Article↗
PubMed2006

Chemo-enzymatic synthesis of raffinose-branched polyelectrolytes and self-assembly application in microcapsules.

A novel biocompatible polyelectrolyte poly(vinyl raffinose-co-acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe(2+)/K(2)S(2)O(8)/H(2)O(2) starting from enzymatically-synthesized monomer: 1-O-vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV-Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano-capsule-carrying galactose residue is a potential targeting drug-controlled delivery systems.

Acrylates↗
PubMed2005

Hydrolase-catalyzed Michael addition of imidazoles to acrylic monomers in organic medium.

Hydrolase-catalyzed Michael addition of imidazole derivatives to acrylic monomers in organic medium was described. A serial of N-substituted imidazole derivatives were successfully synthesized in moderate yields by the catalysis of hydrolases in organic medium. Nine commercially available hydrolases from different sources were screened and all of them were found to be able to catalyze this type of addition reaction. The reaction yields depended on the solvent properties and the solvents with higher log P value supported this enzyme-catalyzed reaction to give higher conversion. Influence of the structure of the Michael acceptor and donor on the enzymatic Michael addition was also investigated. The acceptor with shorter alcohol chain afforded a higher yield. A more rapid conversion was observed when the donor had an electron-withdrawing group. This hydrolase-catalyzed Michael addition reaction has widened the applicability of biocatalysts in organic and bioorganic synthesis.

Acrylates↗
PubMed2005

Regioselective enzymatic acylation of ribavirin to give potential multifunctional derivatives.

Lipase-catalyzed synthesis of potential multifunctional ribavirin derivatives was performed in acetone. Divinyl dicarboxylates with different chain lengths (C4, C6, C9, C10) were used as acyl donors and the reactions were catalyzed by lipase immobilized on acrylic resin from Candida antarctica (CAL-B). Ribavirin was regioselectivly acylated at the primary hydroxyl groups and the corresponding vinyl esters (C4, C6, C9, C10) were prepared in respective yields of 48%, 65%, 54%, 55%.

Acetone↗
PubMed2004

Regiospecific alkaline protease-catalyzed divinyl acyl transesterifications of primary hydroxyl groups of mono- and di-saccharides in pyridine.

This paper describes highly selective transesterification reactions, catalyzed by an alkaline protease from Bacillus subtilis in pyridine, of several mono- and di-saccharides with divinyl dicarboxylates ranging from 4 to 10 carbon atoms. A series of polymerizable vinyl fatty acid sugar esters were obtained with good selectivity and high yields. Most products had high proportions of the alpha anomer. The influences of the enzymes, solvents, temperature, and acyl donor chain length on the reaction were studied. Vinyl sugar esters offer a new family of functional water-soluble monomers for preparation of sugar-containing polymers.

Bacillus subtilis↗
PubMed2004

Michael addition of imidazole with acrylates catalyzed by alkaline protease from Bacillus subtilis in organic media.

A new activity of alkaline protease from Bacillus subtilis for Michael addition reactions of imidazole, 4-nitro-1H-imidazole and 2-methyl-4-nitro-1H-imidazole with acrylates and acrylic acid was investigated. The reactions were carried out in pyridine at 50 degrees C for 72 h. Five N-substituted imidazole derivatives were obtained using acrylate esters, but not acrylic acid, in yields from 62% to 76%.

Acrylates↗
PubMed2004

Controllable regioselective enzymatic synthesis of polymerizable 5'-O-vinyl- and 3'-O-vinyl-nucleoside analogues in acetone.

An efficient synthesis of polymerizable 3'- and 5'-O-acyl-nucleoside derivatives has been developed from inosine and 2'-deoxyuridine by enzyme-catalyzed regioselective acylation with divinyl dicarboxylates. In acetone, Lipozyme (immobilized lipase from Mucor miehei) gave 5'-O-acyl-nucleoside products, and PPL (lipase from porcine pancreas) provided 3'-O-acyl-nucleoside products.

Acetone↗
PubMed2004

Enzyme catalyzed synthesis of some vinyl drug esters in organic medium.

A series of vinyl drug esters was synthesized using acyclovir and chloramphenicol with different carbon chain length acyl donors by alkaline protease from Bacillus subtilis and Lipozyme respectively, in non-aqueous medium. The corresponding vinyl drug derivatives were confirmed by nuclear magnetic resonance and infrared spectrometry. The influences of different organic solvents, reaction time, temperature, and content of water on synthesis of vinyl chloramphenicol esters were studied.

Acyclovir↗