Adsorption of bilirubin on poly‐L‐lysine‐containing nylon membranes: applications in affinity chromatography

Microporous polyamide membranes were activated by 1,1′‐carbonyldiimidazole (CDI) and subsequently bound with hydroxyethyl cellulose (HEC) to amplify reactive groups. Then poly‐L ‐lysine (PLL) as ligand was immobilized onto the HEC‐nylon membranes. The contents in HEC and PLL of PLL‐attached membranes were 153.2 and 63.8 mg (g nylon membrane)^?1, respectively. Such PLL‐HEC affinity membranes were used to adsorb bilirubin from bilirubin‐phosphate and bilirubin‐albumin solutions. The adsorption mechanism of bilirubin and the effects of temperature and ionic strength on adsorption were investigated by batch experiments. The results showed that the adsorption capacity increased with increasing temperature but decreased with increasing NaCl concentration, and the adsorption isotherm fitted the Freundlich model well. Dynamic experiments showed that PLL‐attached membranes can readily remove the bilirubin from bilirubin‐albumin solutions. Copyright © 2005 Society of Chemical Industry     

In vitro cadmium removal from human serum by Cibacron Blue F3GA–thionein‐complex conjugated affinity membranes

A new membrane affinity biosorbent carrying thionein has been developed for selective removal of cadmium ions from human serum. Microporous poly(2‐hydroxyethyl methacrylate) (pHEMA) membranes were prepared by photopolymerization of HEMA. The pseudo dye ligand Cibacron Blue F3GA (CB) was covalently immobilized on the pHEMA membranes. Then, the cysteine‐rich metallopeptide thionein was conjugated onto the CB‐immobilized membrane. The maximum amounts of CB immobilized and thionein conjugated on the membranes were 1.07 µmol cm⁻² and 0.92 µmol cm⁻², respectively. The hydrophilic pHEMA membrane had a swelling ratio of 58% (w/w) with a contact angle of 45.8 °. CB‐immobilized and CB‐immobilized–thionein‐conjugated membranes were used in the Cd(II) removal studies. Cd(II) ion adsorption appeared to reach equilibrium within 30 min and to follow a typical Langmuir adsorption isotherm. The maximum capacity (q _m) of the CB‐immobilized membranes was 0.203 (µmol Cd(II)) cm⁻² membrane and increased to 1.48 (µmol Cd(II)) cm⁻² upon CB–thionein‐complex conjugation. The pHEMA membranes retained their cadmium adsorption capacity even after 10 cycles of repeated use. © 2000 Society of Chemical Industry     

Poly(2‐hydroxyethylmethacrylate)/chitosan dye and different metal‐ion‐immobilized interpenetrating network membranes: Preparation and application in metal affinity chromatography

Composite membranes were synthesized with 2‐hydroxyethylmethacrylate and chitosan (pHEMA/chitosan) via an ultraviolet‐initiated photopolymerization technique in the presence of an initiator (α,α′‐azobisisobutyronitrile). The interpenetrating network (IPN) membranes were improved by the immobilization of dye molecules via hydroxyl and amino groups on the membrane surfaces from the IPNs. A triazidine dye (Procion Green H‐4G) was covalently immobilized as a ligand onto the IPN membranes. The protein showed various affinities to different chelated metal ions on the membrane surfaces that best matched its own distribution of functional sites, resulting in a distribution of binding energies. In support of this interpretation, two different metal ions, Zn(II) and Fe(III), were chelated with the immobilized dye molecules. The adsorption and binding characteristics of the different metal‐ion‐chelated dye‐immobilized IPN membranes for the lysozyme were investigated with aqueous solutions in magnetically stirred cells. The experimental data were analyzed with two adsorption kinetic models, pseudo‐first‐order and pseudo‐second‐order, to determine the best fit equation for the adsorption of lysozyme onto IPN membranes. The second‐order equation for the lysozyme–dye–metal‐chelated IPN membrane systems was the most appropriate equation for predicting the adsorption capacity for all the tested adsorbents. The reversible lysozyme adsorption on the dye‐immobilized and metal‐ion‐chelated membranes obeyed the Temkin isotherm. The lysozyme adsorption capacity of the pHEMA/chitosan dye, pHEMA/chitosan dye–Zn(II), and pHEMA/chitosan dye–Fe(III) membranes were 2.54, 2.85, and 3.64 mg cm^?2, respectively. The nonspecific adsorption of the lysozyme on the plain pHEMA/chitosan membrane was about 0.18 mg cm^?2. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1843–1853, 2003     

Human serum albumin adsorption on poly[(glycidyl methacrylate)‐co‐(methyl methacrylate)] beads modified with a spacer‐arm‐attached L‐histidine ligand

Poly(GMA/MMA) beads were synthesized from glycidyl methacrylate (GMA) and methyl methacrylate (MMA) in the presence of a cross‐linker (i.e. ethyleneglycol dimethacrylate) (EGDMA) via suspension polymerization. The epoxy groups of the poly(GMA/MMA) beads were converted into amino groups with either ammonia or 1,6‐diaminohexane (i.e. spacer‐arm). An L ‐histidine ligand was then covalently immobilized on the aminated (poly(GMA/MMA)‐AH) and/or the spacer‐arm attached (poly(GMA/MMA)‐SAH) beads using glutaric dialdehyde as a coupling agent. Both affinity adsorbents were used in human serum albumin (HSA) adsorption/desorption studies under defined pH, ionic strength or temperature conditions in a batch reactor. The spacer‐arm attached affinity adsorbent resulted in an increase in the adsorption capacity to HSA when compared to the aminated counterpart (i.e. poly(GMA/MMA)‐AH). The maximum adsorption capacities of the affinity adsorbents were found to be significantly high, i.e. 43.7 and 80.2 mg g^?1 (of the beads), while the affinity constants, evaluated by the Langmuir model, were 3.96 × 10^?7 and 9.53 × 10^?7 mol L^?1 for poly(GMA/MMA)‐AH and poly(GMA/MMA)‐SAH, respectively. The adsorption capacities of the affinity adsorbents were decreased for HSA by increasing the ionic strength, adjusted with NaCl. The adsorption kinetics of HSA were analysed by using pseudo‐first and pseudo‐second‐order equations. The second‐order equation fitted well with the experimental data. Copyright © 2005 Society of Chemical Industry     

Synthesis,physical properties,and crystallization of optically active poly(L‐phenyllactic acid) and poly(L‐phenyllactic acid‐co‐L‐lactic acid)

Optically active poly(L ‐phenyllactic acid) (Ph‐PLLA), poly(L ‐lactic acid) (PLLA), and poly(L ‐phenyllactic acid‐co‐L ‐lactic acid) with weight‐average molecular weight exceeding 6 × 10³ g mol^?1 were successfully synthesized by acid catalyzed direct polycondensation of L ‐phenyllactic acid and/or L ‐lactic acid in the presence of 2.5–10 wt % of p‐toluenesulfonic acid. Their physical properties and crystallization behavior were investigated by differential scanning calorimetry, thermogravimetry, and polarimetry. The absolute value of specific optical rotation ([α]) for Ph‐PLLA (?38 deg dm^?1 g^?1 cm³) was much lower than that of [α] for PLLA (?150 deg dm^?1 g^?1 cm³), suggesting that the helical nature was reduced by incorporation of bulky phenyl group. PLLA was crystallizable during solvent evaporation, heating from room temperature, and cooling from the melt. Incorporation of a very low content of bulky phenyllactyl units even at 4 mol % suppressed the crystallization of L ‐lactyl unit sequences during heating and cooling, though the copolymers were crystallizable for L ‐phenylactyl units up to 6 mol % during solvent evaporation. The activation energy of thermal degradation (ΔE_td) for Ph‐PLLA (200 kJ mol^?1) was higher than that for PLLA (158 kJ mol^?1). The ΔE_td for the copolymers increased with an increase in L ‐phenyllactyl unit content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

β‐Galactosidase immobilization into poly(hydroxyethyl methacrylate) membrane and performance in a continuous system

The activity of β‐galactosidase immobilized into a poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane increased from 1.5 to 10.8 U/g pHEMA upon increase in enzyme loading. The K_m values for the free and the entrapped enzyme were found to be 0.26 and 0.81 mM, respectively. The optimum reaction temperatures for the free and the entrapped β‐galactosidase were both found to be 50°C. Similarly, the optimum reaction pH was 7.5 for both the free and the entrapped enzyme. The immobilized β‐galactosidase was characterized in a continuous system during lactose hydrolysis and the operational inactivation rate constant (k_iop) of the entrapped enzyme was found to be 3.1 × 10⁻⁵ min⁻¹. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1367–1373, 1999     

Production of L‐methionine by immobilized pellets of Aspergillus oryzae in a packed bed reactor

Production of L ‐methionine by immobilized pellets of Aspergillus oryzae in a packed bed reactor was investigated. Based on the determination of relative enzymatic activity in the immobilized pellets, the optimum pH and temperature for the resolution reaction were 8.0 and 60 °C, respectively. The effects of substrate concentration on the resolution reaction were also investigated and the kinetic constants (K_m and V_m) of immobilized pellets were found to be 7.99 mmol dm^?3 and 1.38 mmol dm^?3 h^?1, respectively. The maximum substrate concentration for the resolution reaction without inhibition was 0.2 mol dm^?3. The L ‐methionine conversion rate reached 94% and 78% when substrate concentrations were 0.2 and 0.4 mol dm^?3, respectively, at a flow rate of 7.5 cm³ h^?1 using the small‐scale packed bed reactor developed. The half‐life of the L ‐aminoacylase in immobilized pellets was 70 days in continuous operation. All the results obtained in this paper exhibit a practical potential of using immobilized pellets of Aspergillus oryzae in the production of L ‐methionine. © 2002 Society of Chemical Industry     

Novel magnetic nanoparticles for the hydrolysis of starch with Bacillus licheniformis α‐amylase

Novel magnetic nanoparticles with an average size of 350–400 nm with N‐methacryloyl‐(L )‐phenylalanine (MAPA) as a hydrophobic monomer were prepared by the surfactant‐free emulsion polymerization of 2‐hydroxyethyl methacrylate, MAPA, and magnetite in an aqueous dispersion medium. MAPA was synthesized from methacryloyl chloride and L ‐phenylalanine methyl ester. The specific surface area of the nonporous magnetic nanoparticles was found to be 580 m²/g. Magnetic poly[2‐hydroxyethyl methacrylate–N‐methacryloyl‐(L )‐phenylalanine] nanoparticles were characterized by Fourier transform infrared spectroscopy, electron spin resonance, atomic force microscopy, and transmission electron microscopy. Elemental analysis of MAPA for nitrogen was estimated as 4.3 × 10^?3 mmol/g of nanoparticles. Then, magnetic nano‐poly[2‐hydroxyethyl methacrylate–N‐methacryloyl‐(L )‐phenylalanine] nanoparticles were used in the adsorption of Bacillus licheniformis α‐amylase in a batch system. With an optimized adsorption protocol, a very high loading of 705 mg of enzyme/g nanoparticles was obtained. The adsorption phenomena appeared to follow a typical Langmuir isotherm. The inverse of enzyme affinity for free amylase (181.82 mg/mL) was higher than that for immobilized enzyme (81.97 mg/mL). Storage stability was found to increase with adsorption. It was observed that the enzyme could be repeatedly adsorbed and desorbed without a significant loss in the adsorption amount or enzyme activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Methionine‐Containing Poly(amino acid) Hybrid Fibers via Self‐Assembly at Aqueous Interface

Summary: Using sulfonium groups to create a novel fiber material, methionine‐containing hybrid fibers were prepared from S‐methylated poly(L ‐methionine) and poly(L ‐lysine, L ‐methionine) solutions with gellan solution by polyion complex (PIC) formation via self‐assembly at the aqueous interface. The breaking strain of the PIC fibers were increased by incorporation of methionine residues into the poly(L ‐lysine). These findings may provide a new approach for preparing a wool‐like fiber in aqueous media using the synthetic water‐soluble methionine‐containing poly(amino acid)s.

SEM image of Met‐containing PIC fiber: (a) poly[Met¹⁹Met(SMe)⁸¹]‐gellan fiber (magnification, ×500).     

Immobilization of glucoamylase on the plain and on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres

Immobilization glucoamylase onto plain and a six‐carbon spacer arm (i.e., hexamethylene diamine, HMDA) attached poly(2‐hydroxyethylmethacrylate‐ethyleneglycol dimethacrylate) [poly(HEMA‐EGDMA] microspheres was studied. The microspheres were prepared by suspension polymerization and the spacer arm was attached covalently by the reaction of carbonyl groups of poly(HEMA‐EGDMA). Glucoamylase was then covalently immobilized either on the plain of microspheres via CNBr activation or on the spacer arm‐attached microspheres via CNBr activation and/or using carbodiimide (CDI) as a coupling agent. Incorporation of the spacer arm resulted an increase in the apparent activity of the immobilized enzyme with respect to enzyme immobilized on the plain of the microspheres. The activity yield of the immobilized glucoamylase on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres was 63% for CDI coupling and 82% for CNBr coupling. This was 44% for the enzyme, which was immobilized on the plain of the unmodified poly(HEMA‐EGDMA) microspheres via CNBr coupling. The K_m values for the immobilized glucoamylase preparations (on the spacer arm‐attached microspheres) via CDI coupling 0.9% dextrin (w/v) and CNBr coupling 0.6% dextrin (w/v) were higher than that of the free enzyme 0.2% dextrin (w/v).The temperature profiles were broader for both immobilized preparations than that of the free enzyme. The operational inactivation rate constants (k_iop) of immobilized enzymes were found to be 1.42 × 10^?5 min^?1 for CNBr coupled and 3.23 × 10^?5 min^?1 for CDI coupled glucoamylase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2702–2710, 2001     

Hydrophilic modification of poly(vinylidene fluoride) membrane with poly(vinyl pyrrolidone) via a cross‐linking reaction

A highly hydrophilic hollow fiber poly(vinylidene fluoride) (PVDF) membrane [PVDF‐cl‐poly(vinyl pyrrolidone) (PVP) membrane] was prepared by a cross‐linking reaction with the hydrophilic PVP, which was immobilized firmly on the outer surface and cross‐section of the PVDF hollow fiber membrane via a simple immersion process. The cross‐linking between PVDF and PVP was firstly verified via nuclear magnetic resonance measurement on PVP solution after cross‐linking. The hydrophilic stability of the modified PVDF membrane was evaluated by measuring the pure water flux after different times of immersion and drying. The anti‐fouling properties were estimated by cyclic filtration of protein solution. When the cross‐linking time was as long as 6 hr and the PVP content reached 5 wt %, the pure water flux (J_v) was constant as ～ 600 L m^?2 hr^?1. The hydrophilicity of the PVDF‐cl‐PVP membrane was significantly enhanced and exhibited a good stability. The PVDF‐cl‐PVP membrane showed an excellent anti‐protein‐fouling performance during the cyclic filtration of bovine serum albumin solution. Therefore, a highly hydrophilic and anti‐protein‐fouling PVDF hollow fiber membrane with a long‐term stability can be prepared by a simple and economical cross‐linking process with PVP. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Adsorption of IgG on spacer‐arm and L‐arginine ligand attached poly(GMA/MMA/EGDMA) beads

This work presents data on human immunoglobulin G (HIgG) adsorption onto L ‐arginine ligand attached poly(GMA/MMA/EGDMA)‐based affinity beads which were synthesized from methyl methacrylate (MMA) and glycidiyl methacrylate (GMA) in the presence of a crosslinker (i.e., ethylene glycol dimethacrylate; EGDMA) by suspension polymerization. The epoxy groups of the poly(GMA/MMA/EGDMA) beads were converted into amino groups after reaction with ammonia or 1,6‐diaminohexane (i.e., spacer‐arm). With L ‐arginine as a ligand, it was covalently immobilized on the aminated (poly(GMA/MMA/EGDMA)‐ AA) and/or the spacer‐arm attached (poly(GMA/MMA/EGDMA)‐SA) beads, using glutaric dialdehyde as a coupling agent. Both affinity poly(GMA/MMA/EGDMA)‐based beads were used in HIgG adsorption/desorption studies under defined pH, ionic strength, or temperature conditions in a batch reactor, using acid‐treated poly(GMA/MMA/EGDMA) beads as a control system. The poly(GMA/MMA/EGDMA)‐SA affinity beads resulted in an increase in the adsorption capacity to HIgG compared with the aminated counterpart (i.e., poly(GMA/MMA/EGDMA)‐AA). The maximum adsorption capacities of the poly(GMA/MMA/EGDMA)‐AA and poly(GMA/MMA/EGDMA)‐SA affinity beads were found to be 112.36 and 142 mg g^?1, and the affinity constants (K_d), evaluated by the Langmuir model, were 2.48 × 10^?7 and 6.98 × 10^?7M, respectively. Adsorption capacities of the poly(GMA/MMA/EGDMA)‐AA and poly(GMA/MMA/EGDMA)‐SA were decreased with HIgG by increasing the ionic strength adjusted with NaCl. Adsorption kinetic of HIgG onto both affinity adsorbents was analyzed with first‐ and second‐order kinetic equations. The first‐order equation fitted well with the experimental data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 672–679, 2007     

A robust affinity chromatography system based on ceramic monoliths coated with poly(amino acid)‐based polymeric constructs

Traditional chromatographic separation systems are disadvantaged by low flow rates, a high pressure drop across the column, low capacity and poor reusability. Searching for more efficient separation systems we introduced the use of a ceramic monolith as robust support in bioseparations. A coating consisting of l ‐asparagine as ligand, poly(l ‐lysine) as spacer arm and a commercial poly(ethylene acrylic acid) film forming copolymer network (Michem 4983‐40R) was developed as a coating for these ceramic monoliths. Poly(l ‐lysine) was synthesized by ring‐opening polymerization of ε‐trifluoroacetyl‐l ‐lysine N‐carboxyanhydride and coupled to a commercial film‐forming poly(ethylene acrylic acid) network. This construct was then ‘decorated’ with l ‐asparagine via the terminal amino functional groups of poly(L‐lysine) and coated onto the ceramic monolith to selectively bind l ‐asparaginase. Adsorption/elution experiments showed reversible binding between l ‐asparagine and l ‐asparaginase, and the subsequent release of l ‐asparaginase, and between 83% and 94% of the active enzyme was recovered by elution with d ‐asparagine and NaCl solutions. The functional activity of the eluted l ‐asparaginase was verified by a Nessler's assay. While traditional separation processes (adsorption and elution) using gel bead packings take many hours, the ceramic monolith system achieves the same of level of separation in about 1 h. This new system served as a proof of concept for its application in protein separation and purification. This work paves the way to a better understanding of the use of ceramic monoliths as stationary phase coated with a stable polymer construct for more robust and efficient supports in affinity chromatography. © 2020 Society of Industrial Chemistry     

Synthesis and characterization of biodegradable block copolymer pluronic‐b‐poly(L‐lysine)

This study presented the investigations on the synthesis of a novel biodegradable block copolymer of pluronic‐b‐poly(L ‐lysine) (pluronic‐b‐PLL), which combined the characteristics of aliphatic polyester and poly(amino acids). The synthesis work started with end‐capping of pluronic with N‐t‐butoxycarbonyl‐L ‐phenylalanine using dicyclohexylcarbodiimide in the presence of 4‐dimethylaminopyridine, followed by a deprotection process to obtain the amino‐terminated pluronic; the new primary amino group in the modified pluronic initiated ring‐opening polymerization of amino acid N‐carboxyanhydride, which afforded the pluronic‐b‐poly(N^ε‐(Z)‐L ‐lysine) block copolymer. Finally, removal of the side‐chain N^ε‐(carbonybenzoxy) end protecting groups yields the block copolymer of pluronic‐b‐PLL. The products were characterized by ¹H‐NMR, FTIR, DSC, and GPC. The block copolymer micelle containing the anticancer drug paclitaxel was prepared by the double emulsion method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Formation of honeycomb films from poly(L‐lactide)‐block‐poly(ethylene glycol) via water‐droplet templating

The fabrication of honeycomb‐patterned films from amphiphilic poly(L ‐lactide)‐block‐poly(ethylene glycol) (PLEG) in a high‐humidity atmosphere is reported. The influence of the solution concentration on pattern formation was investigated. Moreover, by comparing the different conditions of fabricating regular structures between PLEG and poly(phenylene oxide), the mechanism of the regular pattern formation was studied. Finally, by adding sodium dodecylsulfate to a concentrated solution of 1 g L^?1 PLEG? CHCl₃ which otherwise could not form regular pores, we found that regular pores could be obtained. The PLEG honeycomb films are expected to be of use in cell culture, tissue engineering and many other areas. Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of novel optically active poly(imide–urethane)s derived from N,N′‐(pyromellitoyl)‐bis‐(L‐leucine) diisocyanate and aromatic diols

N,N′‐(Pyromellitoyl)‐bis‐(L ‐leucine) diacid was reacted with ethyl chloroformate in the presence of triethylamine followed by reaction with activated sodium azide and gave N,N′‐(pyromellitoyl)‐bis‐(L ‐leucine) diacylazide in high yield. This diacylazide was heated in dry benzene and gave the unstable N,N′‐(pyromellitoyl)‐bis‐(L ‐leucine) diisocyanate ( 5 ) in quantitative yield. Thus, diisocyanate 5 was generated in situ and polycondensation reaction of this monomer with several aromatic diols, such as 4,4′‐dihydroxybiphenyl, 1,4‐hydroquinone, bisphenol A, phenolphthalein and 1,4‐dihydroxyanthraquinone, was performed in dry toluene under refluxing in the presence of 1,4‐diazabicyclo[2.2.2]octane (triethylenediamine) as a catalyst. The polymerization reactions proceeded within 48 h, producing a series of optically active poly(imide–urethane)s with good yield and moderate inherent viscosity in the range 0.18–0.28 dl g^?1. All of the above polymers were fully characterized by infrared spectra, elemental analyses and specific rotation. Some structural characterization and physical properties of these optically active poly(imide–urethane)s are reported Copyright © 2003 Society of Chemical Industry     

Comparative studies on bioconversion of benzaldehyde to L‐phenylacetylcarbinol (L‐PAC) using calcium alginate‐ and barium alginate‐immobilized cells of Torulaspora delbrueckii

Comparison of the production of L ‐phenylacetylcarbinol (L ‐PAC) from benzaldehyde by cells of Torulaspora delbrueckii immobilized in calcium alginate and barium alginate showed that cells immobilized in calcium alginate beads were usable for up to six cycles compared with nine cycles for barium alginate‐immobilized cells. Barium alginate‐immobilized cells yielded a total of 2.17 g of L ‐PAC in nine cycles whereas in the case of calcium alginate‐immobilized cells, a total of 1.17 g of L ‐PAC was formed when 400 mg benzaldehyde and 400 mm³ of acetaldehyde were used in each cycle as substrate and co‐substrate respectively. Copyright © 2003 Society of Chemical Industry     

Preparation and characterization of nanohydroxyapatite strengthening nanofibrous poly(L‐lactide) scaffold for bone tissue engineering

A biomimetic nanofibrous poly(L ‐lactide) scaffold strengthened by nanohydroxyapatite particles was fabricated via a thermally induced phase separation technique. Scanning electron microscopy results showed that nanohydroxyapatite particles uniformly dispersed in the nanofibrous poly(L ‐lactide) scaffold (50–500 nm in fiber diameter) with slight aggregation at a high nHA content, but showed no influence on the interconnected macroporous and nanofibrous structure of the scaffold. The nanofibrous poly(L ‐lactide) scaffold presented a specific surface area of 34.06 m² g^?1, which was much higher than that of 2.79 m² g^?1 for the poly(L ‐lactide) scaffold with platelet structure. Moreover, the specific surface area of the nanofibrous scaffold was further enhanced by incorporating nanohydroxyapatite particles. With increasing the nanohydroxyapatite content, the compressive modulus and amount of bovine serum albumin adsorbed on the surface of the nanofibrous composite scaffold were markedly improved, as opposed to the decreased crystallinity. In comparison to poly(L ‐lactide) scaffold, both the nanofibrous poly(L ‐lactide) and poly(L ‐lactide)/nanohydroxyapatite scaffolds exhibited a faster degradation rate for their much larger specific surface area. The culture of bone mesenchymal stem cell indicated that the composite nanofibrous poly(L ‐lactide) scaffold with 50 wt % nanohydroxyapatite showed the highest cells viability among various poly(L ‐lactide)‐based scaffolds. The strengthened biomimetic nanofibrous poly(L ‐lactide)/nanohydroxyapatite composite scaffold will be a potential candidate for bone tissue engineering. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of ABA type tri‐block copolymers derived from p‐dioxanone,L‐lactide and poly(ethylene glycol)

A series of triblock co‐polymers, consisting of a poly(ethylene glycol) (PEG) central block joined to two blocks of random p‐dioxanone‐co‐L ‐lactide copolymers were synthesized by ring‐opening polymerization of p‐dioxanone (PDO) and L ‐lactide (LLA) initiated by PEG in the presence of stannous 2‐ethylhexanoate catalyst. The resulting copolymers were characterized by various techniques including ¹H and ¹³C NMR and FTIR spectroscopies, gel permeation chromatography, inherent viscosity, wide‐angle X‐ray diffractometry (WAXD) and differential scanning calorimetry (DSC). The conversion of PDO and L ‐lactide into the polymer was studied various mole ratios and at different polymerization temperature from ¹H NMR spectra. Results of WAXD and DSC showed that the crystallinity of PEG macroinitiator was greatly influenced by the composition of PDO and L ‐lactide in the copolymer. The triblock copolymers with low molecular weight were soluble in water at below room temperature. © 2003 Society of Chemical Industry