Advanced Materials Research Vol. 506

Abstract: A preparation of well-dispersed magnetite nanoparticles was demonstrated in this study. Magnetite nanoparticles (MNPs) were synthesized by a hydrothermal method using aloe vera extract and serial centrifugation was employed to separate the sizes of well-dispersed particles. Well-dispersed MNPs with average sizes of 241, 227, 195, 165, 141 and 93 nm were obtained. They were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometry (VSM). XRD results indicated the MNPs were Fe₃O₄. Magnetic hysteresis loop measurements of the samples showed superparamagnetic properties. Pulsed nuclear magnetic resonance (NMR) showed stable proton (¹H) spin-spin relaxation time (T2) values of water with suspended magnetite nanoparticles over a time course of 20 min, suggesting they were well-dispersed. The synthesized magnetite nanoparticles showed low cytotoxicity to NIH 3T3 cells at concentrations of 1-10%.

Abstract: Environmental responsibility is increasing in importance to both consumers and industries. Biopolymer like poly (lactic acid); PLA is an interesting polymer to replace existing petroleum-based material. PLA is very rigid but inherently brittle and easily thermal degraded during processing. To improve the toughness of PLA, poly (butylene adipate-co-terephthalate); PBAT is widely used. This study focuses on the properties of PLA/PBAT blends. The effects of blend composition on the morphology and properties of PLA/PBAT blends were investigated. Also, the use of Irganox antioxidant in improving blend properties is reported. The results showed that the morphology and properties of the blends depend strongly on blend composition. SEM analysis revealed a co-continuous structure in the blend with 50% PLA. The co-continuous structure remained after the addition of Irganox antioxidant. The addition of antioxidant led to a significant improvement in tensile and thermal properties of the blend. The elongation at break and decomposition temperature of the 50/50 blend increased markedly after 0.3% Irganox antioxidant was added.

Abstract: Properties of biopolymer films which were blended from pectin and flour were investigated. Pectin was extracted from pomelo peel by using hydrochloric acid. The extracted pectin was high methoxyl that was characterized by FTIR. Biopolymer film was prepared by blending pectin (3% and 5%) and flour (1% of corn flour, rice flour, and glutinous rice flour) solution at different ratio (4:1 and 3:2). SEM analysis, tensile strength (TS), elongation, and thickness were studied. Tensile test was affected by the amount of pectin and type of flour. At the same concentration of pectin and the ratio of pectin and flour, tensile strength of the film form glutinous rice flour blending was higher than rice and corn flour. The stress of film from glutinous rice flour, rice flour, and corn flour at 3% pectin at ratio of pectin and flour 3:2 was 68.65, 58.25, 46.31 MPa, respectively. In addition, the tensile stress was increased when the amount of glutinous rice flour was increased. The film thickness was 0.1±0.02 mm. Considered the properties of these polymer compared with synthetic polymer, these are interesting alternative for packaging material production.

Abstract: Hypercoiling poly (styrene-alt-maleic anhydride) (PSMA) is known to undergo conformational transition in response to environmental stimuli. This behavior allows it to associate with the phospholipid, 2-dilauryl-sn-glycero-3-phosphocholine (DLPC) to produce nanostructures analogous to lipoproteins. The complex represents a new bio-mimetic delivery vehicle with applications in the cosmetic and pharmaceutical industries. This study investigates, for the first time, the association behavior of PSMA and DLPC through the combination of different analytical techniques. The results indicate that the association is primarily driven by hydrophobic interactions and depends on various factors including the polymer/lipid ratio, the polymer molecular weight and the pH of the aqueous environment. The conformational transition of PSMA leads to the formation of discrete micellar complexes involving anisotropic-to-isotropic lipid phase transformation. As the number of hydrophobic moieties in the polymer is increased, the pH-dependent conformational transition of the polymer plays less important part in achieving this phase transition of the lipid.

Abstract: Human dermis was used as a new source of raw material for tissue engineering scaffold fabrication. Three human dermal solutions were prepared from different fractions after centrifugation and denoted as DS-1, DS-2 and DS-3. Approximately, the ratios of sulfated GAGs to collagen were 0.03, 0.02 and 0.04 for DS-1, DS-2 and DS-3, respectively. Scaffolds from the human dermal solutions and the commercial bovine type I collagen (Sigma^®, St. Louis, MO, USA) were fabricated. The scaffolds were submerged in the normal culture medium and the calcium depositions were determined at day 1, 7 and 21. The highest calcium deposit was found in the scaffolds from type I collagen, the second were the scaffolds from DS-2, the third were the scaffolds from DS-1 and the lowest were the scaffolds from DS-3 for all time points. Histological sections stained with von Kossa stain explicitly exhibit the calcium depositions in the scaffolds. The calcium deposited in a manner according to the sulfated GAGs/collagen ratios of the scaffold materials. Calcium deposits are naturally incoperated into the collagen matrix of the human dermal solution-derived scaffolds. In bone tissue engineering, interpretation of experimental results should be careful of the spontaneous calcium deposition in scaffolds from collagen.

Abstract: Four metal tert-butoxides, namely: aluminum (III) tert-butoxide, Al (Ot-C₄H₉)₃, tin (II) tert-butoxide, Sn (Ot-C₄H₉)₂, titanium (IV) tert-butoxide, Ti (Ot-C₄H₉)₄, and lithium tert-butoxide, Li (Ot-C₄H₉), were used as initiators in the bulk ring-opening polymerization (ROP) of ε-caprolactone (CL). The polymerizations were carried out at 120 °C for 72 hrs. It was found that the Al (Ot-C₄H₉)₃ only partially dissolved in the CL monomer and gave a low % conversion. The Li (Ot-C₄H₉) initiator did not dissolve and gave no polymerization. In contrast, the Sn (Ot-C₄H₉)₂ initiator dissolved completely, albeit very slowly, and gave a high % conversion. The Ti (Ot-C₄H₉)₄ initiator was by far the easiest and quickest to dissolve and also gave a high % conversion. Consequently, Ti (Ot-C₄H₉)₄-initiated polymerization was studied further by dilatometry at 120°C. From the kinetic results, a first-order rate constant, k_p, of 0.120 l mol^-1 min^-1 was obtained.

Abstract: Apatite-wollastonite bioactive glass-ceramic scaffolds were fabricated from the SiO₂-CaO-P₂O₅ MgO-CaF₂ glass system by controlled crystallization between 800 and 1200C of the melted and quenched glass powder. Wood powder with controlled particle size distribution was used to obtain bioactive glass-ceramic scaffolds by burning-out process during crystallization of glass. Bioactive phases of apatite and wollastonite were found in all crystallized samples but the relative amount depended on the crystallization temperature. The bioactivity was studied via simulated body fluid (SBF) solution from 2 to 12 weeks. After soaking for 2 weeks, a porous hydroxyl-carbonate apatite (HCA) layer formed at the SBF-glass ceramic interface and the HCA layer thickness increased at longer soaking periods. This study led to a promising platform for hard tissue engineering.

Abstract: The ionic substitutions have been proposed as a tool to improve the biological performance of hydroxyapatite (HAp) based materials. In the present work, the systems of Ca_(10-x)Mg_x(PO₄)₆(OH)₂ (MgHAp, x = 0, 1, 2, and 3) were successfully synthesized by solgel method. To obtain nanocrystalline of MgHAp, the prepared precursors were calcined in air at 600 °C for 2 h. The samples were characterized by Xray diffraction (XRD) and transmission electron microscope (TEM) observation. The XRD results confirm the formation of pure phase of HAp with the lattice parameter a in the range of 0.94170.9479 nm and c of 0.68410.6919 nm. The crystallite sizes of the powder are found to be 3546 nm as evaluated by the XRD line broadening method. The morphology of the samples are spherical shape of diameter less than 100 nm as evaluated by TEM. The corresponding selected area electron diffraction (SAED) analysis further confirms the formation of hexagonal structure of HAp.

Abstract: Lipase-catalysed polymerization is an emerging green alternative method for the synthesis of polylactic acid (PLA) from lactic acid (LA) monomer. Use of the lipase catalyst avoids the need for potentially toxic chemical catalysts. The concentration of the lipase enzyme is one of several factors which influence the polymerization process. This paper reports on the effects of the lipase concentration on the characteristics of the low molecular weight polylactic acid (PLA) formed via lipase-catalyzed polymerization of lactic acid. The polylactic acid products made by this method are characterized by Fourier Transform Infrared Spectroscopy (FTIR). Low molecular weight polylactic acid could be successfully produced from commercial lactic acid by using the commercial lipase Lipozyme TL IM at 50 °C in a 5-hour reaction.

Abstract: N,O-Carboxymethyl chitosans were synthesized by the reaction between shrimp, crab and squid chitosans with monochloroacetic acid under basic conditions at 50°C. The mole ratio of reactants was obtained from various reaction conditions of shrimp chitosan polymer and oligomer types. The mole ratio 1:12:6 of chitosan:sodium hydroxide:monochloroacetic acid was used for preparing carboxymethyl of chitosan polymer types while carboxymethyl of chitosan oligomer types were used the mole ratio 1:6:3 of chitosan:sodium hydroxide:monochloroacetic acid. The chemical structure was analyzed by fourier transformed infrared spectroscopy (FT-IR) and proton nuclear magnatic resonance spectroscopy (¹H-NMR). The FT-IR was used for confirm the insertion of carboxymethyl group on chitosan molecules. The ¹H-NMR was used for determining the degree of substitution (DS) of carboxymethylation at hydroxyl and amino sites of chitosans. Carboxymethyl chitosan samples had the total DS of carboxymethylation ranging from 1.0-2.2. The highest of DS of carboxymethylation was from shrimp chitosan oligomer type.