Advanced Materials Research Vol. 506

Abstract: NLCs are second generation of lipid nanoparticles which have many advantages that make them interesting for topical drugs delivery systems. All-trans retinoic acids (ATRAs) are highly lipophilic and instable in the presence of air, light and heat. In this study, 0.3% ATRAs loaded NLCs were developed by de novo emulsifications, then were reduced to nanometer range by ultrasonicator. The characterizations of NLCs i.e. size and zeta potential were examined. NLCs with different solid:liquid lipids ratios (2:1, 1:1 and 1:2), were formulated in order to maximize the skin permeation. The results demonstrate the sizes of NLCs were in nanometer ranges with negative zeta potential. Moreover the results showed that the amount of solid lipids in the formulation affected the skin permeation. The highest ATRAs permeations though shed snake skin could be achieved from the NLCs which lipid matrixs were composed of 2:1 solid:liquid lipids ratios.

Abstract: The aim of this study was to investigate the effect of BaZr_0.05Ti_0.95O₃ (BZT) addition on the microstructure, physical, dielectric and piezoelectric properties of hydroxyapatite (HA), and develop new biomaterials which have potential applications in the support for cellular growth and in the system for bone regeneration. In this case the BaZr_0.05Ti_0.95O₃- HA composites (HABZT) were prepared by conventional sintering method. The BZT were added to HA with ratio 0, 10, 20 and 30 %wt. Then the mixed powders were pressed and subsequently sintered at the temperature ranging from 1150 to 1350°C. The result showed that the dielectric and piezoelectric properties were improved by the addition of BZT. Moreover, the bioactivity of the HA improved with addition of BZT especially at 10% as evident by the formation of bone like apatite layers on the surface of all BCZT composites after soaking in simulated body fluid (SBF) for 15 days. The results confirmed the possibility of using these bioactive composites for treatment within the human body.

Abstract: Hydroxyapatite (HA) is classified as one of the important bioceramics, which has been used in orthopedics, medical and dental applications. It has bioactivity and good biocompatibility with the human organism, which is suitable in medical applications as an implant or coating on prostheses such as metal. In this study, the effects of calcinations temperatures on phase formation and physical properties of HA particles were investigated. The HA particles synthesized from bovine bone were cleaned and fired at 800°C and subsequently ball milled for 24 h. Then received HA particles were divided into two parts. The first one was calcined at various temperatures from 900 to 1400°C and the second one was vibratory milled for 4 h and subsequently calcined at various temperatures from 900 to 1400°C. The calcined HA particles were characterized by X-ray diffraction (XRD) for their crystal structure and particle size analysis. Scanning electron microscope (SEM) was used for microstructural.

Abstract: The aim of this work was to analyze the effect of using rice husk ash (RHA) and bovine bone as raw materials of glass-ceramics based on the SiO₂-Na₂O-CaO-P₂O₅ system on their physical, mechanical properties and bioactivity. All of the investigated compositions were prepared by melting the glass mixtures at 1300°C for 3 h. The resulting glass samples were heated at different temperatures ranging from 600 to 1000°C with fixed dwell-time for 2 h for crystallization. Phase identification of the prepared glass ceramics was carried out by X-Ray diffraction (XRD) and scanning electron microscope (SEM) techniques. In addition, in vitro test was carried out in stimulated body fluid (SBF). Differential thermal analysis (DTA) showed that the glass transition occurred at 505°C and crystallization at 700°C. The main crystalline phase form in most glass ceramics is a sodium calcium silicate. The optimum heat treatment temperature, at which the maximum mechanical value (620 HV) could be obtained, is around 1000°C. After incubation in SBF for 7 days, all of the samples show good bioactivity in vitro, as evident by the formation of bone like apatite phase.

Abstract: PLA-co-PEG copolymers synthesized through ring opening polymerization between a lactide monomer and PEG were solution-cast into films. The effect of the molecular weight of PEG and also the percentage of added PEG on the properties of the copolymers were studied. The molecular weight of PEG was 4000, 8000, and 20000 while the percentage of added PEG was varied from 10 to 50 mol%. The NMR spectrums confirmed that the ratio of PLA:PEG in the copolymers are close to the monomer feed of the respective monomers. DSC and TGA results showed that, compared to PLA, the PLA-co-PEG copolymers have slightly lower melting temperatures but similar thermal degradation temperatures. Both molecular weights and the percentage added of PEG influenced the properties of the films. As expected, the tensile strength and Youngs modulus of the PLA-co-PEG copolymer films were lower than that of neat PLA. Conversely, theelongation at break of the copolymer film was higher than that of the PLA when the molecular weight of PEG was 20000. This study suggests that high molecular weight PEG could be used to improve the flexibility of the polymer films.

Abstract: Coconut (Cocos nucifera L.) oil is composed predominately of medium-chain triglycerides which have been reported to be beneficial to human health. It also contains free fatty acids (FFAs) which can combine with glycerol to form monoglycerides, diglycerides, and triglycerides. The analysis of FFAs and their glycerides has been proposed to assess the quality of coconut oil used as raw materials in various industrial fields. The aim of this study was to develop the qualitative method for investigation of FFA and their glycerides in coconut oil using thin layer chromatography (TLC). Coconut oil and standards of FFA and their glycerides were chromatographed separately on Silica gel 60 F254 TLC plates using hexane: ether: acetic acid (60:40:1) and hexane: ethyl acetate: acetic acid (60:40:0.5) as solvent systems A and B, respectively. The spots on developing TLC plates were detected and compared using 254-nm UV light and iodine vapor. The results showed that the resolution of solvent system A was better than that of solvent system B. However, both solvent systems were used to confirm the results. The retention factor (Rf) values of the components were in good agreement with their polarity. This method should provide a guideline for qualitative analysis of coconut oil.

Abstract: The objective of this study was to synthesize shellac phthalate succinate (SHL-PHT-SUC) through organic solvent-free reaction. Firstly, shellac phthalate (SHL-PHT) was prepared by co-grinding and annealing shellac (SHL) with phthalic anhydride (PHTA). The SHL-PHT was subsequently ground with succinic anhydride (SUCA) and activated by the same process to obtain SHL-PHT-SUC. The formation of all SHL derivatives was investigated by the monitoring acid value, insoluble solid and later confirmed by FTIR spectroscopy. The result indicated that the acid value was increased after annealing SHL-PHT with SUCA, suggesting the addition of succinate moiety at SHL-PHT molecule. The presence of C-O stretching of ester linkage was also observed in the FTIR spectrum. The results suggested the formation of SHL-PHT-SUC by esterification. In addition, the thermal stability was assessed by ageing the SHL derivatives at 100°C for 24 h. The SHL-PHT-SUC demonstrated lower stability as compared to SHL-PHT. The stability of SHL derivatives appeared to be related with the cross-linking of the polymer chain. In the case of SHL-PHT-SUC, succinate group, having more molecular mobility, this might encourage fast and extensive cross-linking as compared to the phthalate group and thus promoted the ageing process.

Abstract: In this research, the two-step sintering method was employed to develop the physical properties of Hydroxyapatite (HA) ceramics. HA powder was extracted from bovine bone and vibro-milling method was used to make the fine particles. For the two-step sintering process, the samples were heated up to the first step temperature (T₁=1200^°C) for 6 min then the temperature was lowered down to second step temperatures (T₂=1150^°C and 1100^°C) for 5, 10 and 15 h. Another set of samples were heated up to the first step temperature (T₁=1250^°C) for 6 min then the temperature was lowered down to second step temperature (T₂=1150^°C) for 5, 10 and 15 h. X-ray diffraction (XRD) was carried out for investigating the phase formation in the prepared ceramics. Physical properties of the prepared ceramics were studied such as porosity, density by Archimedess principle. It is found that most of the samples exhibit Ca₅(PO₄)₃(OH) phase with JCPDS number 09-0432. The first step temperature plays the most roles on controlling the density of HA ceramics than T₂ and dwell times. Microstructures of the HA powder and ceramics were characterized using scanning electron microscope (SEM).The feasibility in using the prepared ceramics for bone replacement applications was discussed.

Abstract: A series of 3,5-substituted-4,5-dihydro-1H-pyrazole-1-carbothioamide derivatives were synthesized. Their structures were determined on the basis of spectroscopic data interpretation and their tyrosinase inhibitory activity was determined. The results showed that compound 2 (at 1.00 mg/mL) exhibits significant tyrosinase inhibitory activity with % inhibition of 91.866 ± 2.086 with L-tyrosine as substrate whereas compound 3 (at 1.00 mg/mL) exhibits significant tyrosinase inhibitory activity with % inhibition of 79.266 ± 0.552 and 89.593 ± 1.015 with L-tyrosine and L-DOPA as substrates. The IC₅₀ values of compounds 2 and 3 were further determined comparing with kojic acid and resveratrol. It was found that IC₅₀ values of compounds 2 and 3 were 0.391 ± 0.017 and 0.259 ± 0.005 mg/mL., with L-tyrosine as substrate, which were lower than those of the standard tyrosinase inhibitory resveratrol (0.965 ± 0.016 mg/mL).

Abstract: In this work, thepreparation and morphology of biphasic calcium phosphate (BCP) have been studied. The biphasic calcium phosphate (BCP) ceramics were prepared by mixing between hydroxyapatite (HA) and Beta-tricalcium phosphate (β-TCP) powderby ball milling technique with different ratios (100:0,80:20,60:40,50:50,40:60, 20:80 and 0:100). After that the mixtures were forming by Gel casting method and then sintered at 1200°C, respectively. The phase formation of the biphasic calcium phosphateceramics were studied by X-ray diffraction (XRD) and their ceramic microstructure,shrinkage and density were investigated.