Waraporn Suvannapruk

Development of antibiotics impregnated nanosized silver phosphate-doped hydroxyapatite bone graft

Nanosized Ag3PO4 loaded hydroxyapatite which was prepared by a novel low temperature phosphorization of 3D printed calcium sulfate dihydrate at the nominal silver concentration of 0.001M and 0.005M was impregnated by two antibiotics including gentamicin and vancomycin. Phase composition, microstructure, antibiotics loading, silver content, antimicrobial performance, and cytotoxic potential of the prepared samples were characterized. It was found that the fabricated sample consisted of hydroxyapatite as a main phase and spherical-shaped silver phosphate nanoparticles distributing within the cluster of hydroxyapatite crystals. Antibacterial activity of the samples against two bacterial strains (gram negative P. aeruginosa and gram positive S. aureus) was carried out. It was found that the combination of antibiotics and nanosized Ag3PO4 in hydroxyapatite could enhance the antibacterial performance of the samples by increasing the duration in which the materials exhibited antibacterial property and the size of the inhibition zone depending on the type of antibiotics and bacterial strains compared to those contained antibiotics or nanosilver phosphate alone. Cytotoxic potential against osteoblasts of antibiotics impregnated nanosilver phosphate hydroxyapatite was found to depend on the combination of antibiotics content, type of antibiotics, and nanosilver phosphate content.

Effect of Solvent and Drug Impregnation Techniques on Total Drug Content in Rifampicin Impregnated Hydroxyapatite for Localized Bone Tuberculosis Treatment

Rifampicin drug was experimentally loaded into 3D printed porous hydroxyapatite using two types of solvents (methanol or N-methyl-2-pyrrolidone) and various solution impregnation techniques aiming to maximize the total drug content in the samples. All vacuum assisted impregnations gave greater rifampicin content in the sample than that of atmospheric immersion. For similar vacuum assisted impregnation technique, the use of methanol could produce greater amount of drug in the sample than using N-methyl-2-pyrrolidone. For each solvent, the loading technique which gave maximum drug content was different. 2_step vacuum loading technique could impregnate the greatest amount of drug in the hydroxyapatite sample when using methanol as a solvent while one step vacuum loading technique with 10 % solution level (1_step_10) gave the greatest amount of the impregnated drug when using N-methyl-2-pyrrolidone as a solvent. These differences were related to the evaporation rate of the solvent and the degree of concentrated drug on the surface of the samples.

Evaluation of PEG-PPG-PEG Copolymer Blends for Using as Resorbable Bone Wax

In this study, four types of PEG-PPG-PEG copolymers solids and pastes having different molecular mass (Mw~5800, 8400, 12000 and 14600) were selected and mixed at various compositions ranging from 40 to 60 % by weight. The textures and handling characteristics of the prepared samples were evaluated in comparison to that of the commercial non-resorbable bone wax. Thermal and mechanical properties of the blends were determined by a differential scanning calorimeter and a universal testing machine respectively. It was found that the combination of solid (Mw~8400) and paste-like (Mw~12000) copolymers at the ratio of 40:60 gave the closest smooth texture with good smearability and had similar melting temperature to the commercial bone wax, but having slightly lower compressive stiffness. Preliminary cytotoxicity of the selected formulations against osteoblasts revealed that the cell viability was greater than 70 % indicating that the prepared samples did not show any cytotoxic potential.

Effect of Layer Thickness on the Phosphorization of 3DP Gypsum Based Monolith

Influence of using different layer thickness in three dimensional printing process of calcium sulfate based sample prior to phosphorization process was studied. Phase composition and mechanical properties of the resulting structure were characterized by x-ray diffraction and three-point bending techniques. It was seen that transformation rate, phase composition and flexural strength were all affected by the change in layer thickness. Too high layer thickness, 0.2 mm, caused the disintegration of sample during phosphorization while too low layer thickness, 0.08 mm, decreased the transformation rate. The optimised layer thickness in this study which gave both high conversion rate and flexural properties was found to be 0.1 mm.

Fabrication of Porous Polyethylene by Two-Stepped Heat Treatment and Powder Printing Technique

In this study, a combination of powder printing technique and two-stepped heat treatment was utilized as a mean to prepare porous high density polyethylene structure. Physical and mechanical properties of the resulting structure were then characterized by porosity measurement and monotonic tensile test. It was found that the relationship between structure and properties was strongly influenced by processing conditions including compositions, treatment times and treatment temperatures. This process could increase the properties of porous high density polyethylene significantly over the single-stepped heat treatment without destroying porous structure. Porous high density polyethylene bodies having a porosity ranging from 46-58 percents with tensile strength up to approximately 4 MPa could be successfully prepared in this study.

Properties Alteration of Anti-Tuberculosis Drugs Loaded 3D Printed Hydroxyapatite by Polycaprolactone Coating

Anti-tuberculosis drugs loaded three dimensionally printed hydroxyapatite (3D printed HA) were prepared and coated with polycaprolactone to study the effect of coating on compressive resistance, microstructure, drug content and releasing characteristics. Smooth coating layer was observed on the surfaces of all coated samples while the uncoated samples displayed rough and porous surfaces. Coated samples had greater compressive resistance than uncoated samples, but the total drug contents in coated samples were slightly lower than those of uncoated ones. Both coated and uncoated samples displayed burst release of drugs initially and followed by a small release afterward. Polycaprolactone coating greatly decrease the amount of burst release of rifampicin drug loaded samples, but slightly decrease in the case of isoniazid drug loaded samples. Higher solubility of isoniazid than rifampicin in release media was thought to be the cause of limited efficiency of coating as observed.

Physical and Mechanical Characterizations of Oxidized Regenerated Cellulose/Polycaprolactone Composite for Use as a Synthetic Dura Mater

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.

Preparation of 3DP Hydroxyapatite/Polycaprolactone Composite by a Novel Sequential Infiltration Technique

In this study, a novel sequential infiltration technique using both high and low molecular mass polymers was developed as a means to improve the toughness and mechanical integrity of three dimensional printed hydroxyapatite compared to typical polymer infiltration technique which employed only single molecular mass polymer. Biodegradable polycaprolactone (PCL, Mw ~ 10,000 designated low or Mw ~ 80,000 designated high) were selected as an infiltrant since it has shown good biocompatibility together with a high elongation and energy to failure as compared to other medical polymers. Characterizations including thermogravimetry analysis, flexural properties, in vitro degradation and liquid absorption were carried out. It was observed that the combination of high and low MW infiltration in sequence yielded greater increase in the flexural modulus, strength, elongation and energy at break than those of using only single molecular mass infiltration. This enhancement in mechanical properties was found to be due to the increase in the content of infiltrated polymer into the samples in combination with the synergic effect of low and high molecular mass polycaprolactone resulting from the sequential infiltration.

Performance of Bioactive Hydroxyapatite Coating after Soaking in Simulated Body Fluid

In this study, in vitro acellular bioactivity and tensile bonding strength of hydroxyapatite (HA) coating synthesized by sol-gel technique after long-term storage in simulated body fluid (SBF) for up to 32 days were studied. After soaking in SBF, it was observed that new bone-like apatite layer was formed on the coating indicating the bioactive nature. Bonding strength of sol-gel coated rods was found to decrease with soaking times, from 55 to 30 MPa. In comparison to adhesive bonded titanium rods which were used as control specimens, the values were found to be equal or even greater in certain soaking periods. Debonding at adhesive-titanium interface was the failure mode indicating that the coating is still intact. Therefore, it could be concluded that this sol-gel coating is bioactive and the coating adhesion to substrate is sufficiently strong.