Key Engineering Materials Vol. 659

Abstract: Hydroxyapatite has been used as bone substitutes in many applications due to its biocompatibility and osteoconductivity. Generally, it is considered to be biostable and shows limited resorption in the body. In some circumstances, resorption of bone substitutes is more desirable since it could accelerate the bone healing process. It is known that processing route is one of the crucial parameters that could affect the properties of materials. Three different processes were employed in this study to fabricate hydroxyapatite samples including low temperature transformation of three-dimensionally printed calcium sulfate (HA1), high temperature sintering of three-dimensionally printed hydroxyapatite (HA2) and high temperature sintering of mold pressed hydroxyapatite (HA3). HA1 was found to contain high porosity and low crystallinity whereas HA2 had high porosity and high crystallinity. HA3 had low porosity, but high crystallinity. In vitro resorbability of these samples was studied by submerging all the samples in simulated body fluid (SBF) for 1, 7, 14 and 28 days and determining their phase composition, density change, liquid absorption, ions release and microstructure. It was found that HA1 showed the greatest density loss and liquid absorption followed by HA2 and HA3 respectively. Calcium and phosphorus ions in SBF were observed to decrease with submerging times for HA1 and HA2, but remained constant for HA3. SEM studies showed that new calcium phosphate crystals were found to form on the surface of the HA1 and HA2 samples whereas none was found on HA3. These results suggested that HA1 had the greatest resorbability and calcium phosphate crystals forming ability on its surface followed by HA2 and HA3 respectively. Therefore, porosity and crystallinity of the samples resulting from different processing routes are important factors for in vitro resorbability of hydroxyapatite.

Abstract: Bleached shellac (BS), a biodegradable natural resin purified from insect lac, has been used in a varity of controlled drug delivery systems. Nevertheless, there were negligible researches explored the potential of it as in injectable in situ microparticles (ISM) applications. The goal of this study was to utilize BS to form ISM (shellac-solution dispersed into an external olive oil phase, as o/o emulsion) prepared by two-syringe technique. Addition of glyceryl monostearate (GMS) as stabilizer obviously decreased the emulsion droplet size. ISM emulsion comprising 5% w/w GMS in external phase could form into droplets and precipitate in form of microparticles after exposure to phosphate buffer. 2-Pyrrolidone was the most appropriate solvent to form massive microparticles with regular shape especially at ratio of 7:3 external:internal phases. ISM transformation was occurred after exposure to phosphate buffer and tended to reduce the droplet size when ratio of external phase was higher than 50%. Incorporation of doxycycline hyclate did not influence the amount and size of ISM. Therefore shellac exhibited as an alternative polymer matrix for ISM which higher amount of GMS could reduce the size of emulsion droplet and volume phase ratio seriously influenced on emulsion size and ISM formation.

Abstract: In situ forming gel with solvent exchange mechanism is one of drug delivery systems for periodontitis treatment. The system is injected into the desired site then transforms into a gel state when the solvent diffuses out and aqueous diffuses in. The in situ forming Eudragit RS gels loading 1, 5 and 10%w/w metronidazole (MT) were developed in this study using N-methyl pyrrolidone (NMP), 2-pyrrolidone and dimethyl sulfoxide (DMSO) as solvent. The viscosity of the gel systems in all solvents were increased as drug or polymer amount was increased with Newtonian flow behavior. Transformation into gel was evident after initiated the systems in phosphate buffer pH 6.8. NMP systems exhibited the lowest work of syringeability through 18 G syringe. Drug release from dialysis tube of DMSO systems was slower than that of NMP and 2-pyrrolidone systems, respectively. Antimicrobial activity against Staphylococcus aureus of the systems comprising MT using NMP as solvent was greater than that using 2-pyrrolidone and DMSO, respectively, which the antimicrobial activity was increased as the drug amount was increased. Therefore, the solvent type affected the viscosity, gel formation, syringeability, drug release and antimicrobial activity of Eudragit RS systems. These developed systems sustained the drug release and inhibited the bacterial growth hence they were interesting systems for periodontitis treatment.

Abstract: An inadequate dural closure is one of the most challenging problems for neurosurgeons during the surgical procedures. A repair of the dura mater by natural or synthetic materials is often needed. This should satisfy fundamental criteria for example preventing cerebrospinal fluid leakage, exhibiting similar mechanical properties to the natural dura mater and not inducing foreign body reaction or inflammation. Oxidized regenerated cellulose (ORC) and polycaprolactone (PCL) have been extensively used as hemostatic agent and implant in many biomedical applications due to their long term proven safety, biodegradability and biocompatibility. This study investigated the potential of using a combination of ORC and PCL as a novel dural substitute. ORC/PCL composites were prepared by solution infiltration of ORC sheet with PCL solution (Mw ≈ 80,000) at various concentrations ranging 10-50 g/100 ml. Characterizations including density, tensile properties and microstructure were then performed. It was found that the density of all formulations did not differ and were in the range of 0.5-0.6 kg m^-3. Microstructure of the samples typically comprised a bilayer structure having a PCL layer on one side and the ORC/PCL mixed layer on another side. Tensile modulus and strength initially decreased with increasing PCL concentration for up to 20% and re-increased again with further increasing PCL concentration. Elongation at break of all formulations was not significantly different. Both physical and mechanical properties of the samples were found to be similar to those of natural human dura mater.

Abstract: Last few decades, tamarind seed that is the food industrial waste was extracted their kernel to obtain xyloglucan for food, cosmetic, and medical applications. This study aimed to practically prepare and physically characterize the films containing xyloglucan (XG), bacterial cellulose (BC) and glycerol (GLY) for cosmetic applications. In the experiment, the films were prepared by varying (XG:GLY)-%BC ratio and using solution casting method. Preliminary, the films were observed the morphology. Subsequently, it was performed the adhesive test by using Texture Analyzer. From the preparation, it was found that the addition of BC provided the non-wrinkled films unlike the films that were prepared without BC addition. However, low transparent films were obtained from the addition of BC. From the adhesive test, the stickiness (SN), the adhesiveness (AN), and the cohesiveness (CN) were obtained simultaneously. The results revealed that the increasing of GLY and BC trendily increased SN and CN of the films, which (10:90)-9% films provided the highest SN (57.64 g) and AN (1.01 g.sec). However, (10:90)-9% films and (20:80)-8% provided insignificant difference of SN and AN. Meanwhile, (30:70)-7% films provided the lowest SN (10.77 g) and AN (0.21 g.sec). Moreover, the influence of GLY and BC on decreasing of CN was significantly found on (30:70)-7% films only. As the results, it could be concluded as the addition of BC into the films provided the non-wrinkled films, and the increasing of GLY provided the high adhesive films that suitable to apply on the skin for used as the transdermal patch. In the future works, the films will be added by the herbal extracts to provide biological activities such as anti-oxidation, anti-microbial, and anti-melanogenesis to the films.

Abstract: Silk fibroin, gelatin, and chitosan blended solution in formic acid with different composition ratios were electrospun. The fiber could be produced from SF:G : C blended solution at weight blending ratios (%wt: %wt: ml) of 10:20:0, 10:20:0.5, 10:20;1, 10:20:1.5, 10:20:2, and 20:10:1. When the chitosan content in blended solution increased, the average diameter decreased from 245 to 100 nm and fiber size distribution was narrow. The SF: G: C solution at ratio of 10:20:1 under high electric field and long spinning distance provided the continuous and uniform fibers. The formic acid as solvent did not affect to the electrospinnability and morphology of SF: G: C blended nanofiber. Tensile strength of SF: G: C (10:20:1) blended nanofiber was decreased with increasing of silk fibroin content, SF: G: C (20:10:1). The results indicated that SF: G: C electrospun nanofiber mats could be prepared and have a potential to be applied in membrane application.

Abstract: The design of engineered bone substitutes takes biocompatibility and mechanical compatibility into account as prerequisite requirements. Titanium (Ti) and hydroxyapatite (HA) with chemical formula of Ca₁₀(PO₄)₆(OH)₂, show good biocompatibility and are known as biomaterials. To combine metal powder (Ti) and ceramic powder (HA) as a composite material with mechanical properties comparable to those of natural bones needs strategy. In this work, powder metallurgy process was employed to produce Ti-HA composites, with nominal HA powder contents in the range of 0-100 vol.%. Mixtures of Ti and HA powders were pressed in a rigid die. Sintering was performed in vacuum atmosphere. The as-sintered specimens were tested on biocompatibility in a human-osteoblast cells. It was found that processing and materials parameters, including compaction pressure, control the composite microstructures and mechanical properties. Laboratory bone tissue culturing showed that a bone tissue could grow on the artificial bones (sintered Ti-HA composites).

Abstract: Hydroxyapatite (HAp), with chemical formula of Ca₁₀(PO₄)₆(OH)₂,is one of the most popular biomaterials applied as a scaffold or a scaffold component in bone tissue engineering. Synthesis of this material using calcium from a natural sourcewill be a good strategy for cost reduction. Waste cockle shells containing abundance of nearly pure calcium carbonate (CaCO₃) are ideal sources of calcium. In this study, the waste cockle shells were turned to CaO nanoparticles using a simple chemical route. The CaO nanoparticle was used as a starting material to react with hydrous and anhydrous calcium hydrogen phosphate (CaHPO₄) with calcium-to-phosphate (Ca/P) ratios in the range of1.5-1.67 under a mechanochemical process. The synthesized products were characterized by X-ray diffraction technique and scanning electron microscope.The experimental results revealed that under the same reaction timethe reaction using the dehydrated CaHPO₄yielded a mixture ofHApand residual CaHPO₄whereas the reaction using hydratedCaHPO₄(CaHPO₄.2H₂O) yieldeda mixture of HApand beta tricalcium phosphate (β-TCP). The HAp yields of the reactions using dehydrated and hydratedCaHPO₄were 71% and 51 %, respectively.

Abstract: This research aimed to study the compatibility and properties of deproteinized natural rubber latex (DNRL)/gelatinized starch blended films for use as transdermal patches. Various starches were previously gelatinized by heat treatment. Then, the DNRL/gelatinized starch blended films were prepared by simple mixing of DNRL with gelatinized starch and then drying at 50°C. The various parameters such as types (potato, sago, bean, corn, tapioca, rice and glutinous starches), amounts (5, 10, 15 and 20 part per hundred of rubber (phr)) and concentrations of gelatinized starch pastes (5, 10, 20 and 50%) were evaluated. It was found that all starch types could be blended as a homogeneous mixture with DNRL only in 5 phr. Bean starch also provided the good mixture in 10 and 15 phr. Rice and corn starches in the concentrations up to 20 phr could also be blended. Higher concentration of gelatinized starch pastes obtained the higher viscous liquids that were difficult to blend as a homogeneous mixture with DNRL, and provided inhomogeneous blended films. The dried films of all homogeneous DNRL/gelatinized starch mixtures were slightly yellowish transparent with good physical appearances. The tensile strength, swelling and erosion of these blended films increased when increasing amounts of gelatinized starch, but their elasticities were not different comparing to that of DNRL film itself. However, their strengths should be further improved by adding some plasticizers. Some drugs would be further loaded in these homogeneous film formulations for transdermal delivery.