Journal of Biomimetics, Biomaterials and Biomedical Engineering Vol. 72

Abstract: This study explores the impact of heat treatment parameters on the hardness and microstructure of 17-4PH stainless steel samples fabricated by additive manufacturing, with a focus on dimensional changes throughout the process. The additive manufacturing method used was Bound Metal Deposition (BMD), which includes digital scanning, 3D metal printing, sintering, and post-processing. It was observed that the printed parts undergo a substantial size increase 16.96% (height) and 18.14% (diameter) to compensate for material loss during the binder removal stage in sintering. Although the sintered parts shrink relative to the printed samples, they remain 3.25% taller and 6.05% wider than the original CAD dimensions. Following sintering, the samples underwent solution treatment and aging at various temperatures and times. Microstructural analysis post-solution treatment revealed a martensitic structure as the predominant phase. Aging caused the formation of strengthening precipitates, leading to peak hardness values of 422.0 and 303.0 HV0.5 at aging temperatures of 480 °C and 620 °C for 1 hour, respectively. Dimensional changes during the precipitation hardening stage were minimal and considered negligible.

Abstract: The healing of bone defects is still challenging as therapies like autografts and allografts have limited benefits, especially in load-bearing positions. Bovine Hydroxyapatite (BHA) is a natural biological substance that can be used as a filler to replace damaged bones and overcome the low fracture toughness and brittleness of synthetic Hydroxyapatite (HA). This study presents the precipitation method of Magnesium (Mg)-doped Bovine Hydroxyapatite (Mg-BHA). FTIR analysis ensured the existence of phosphate (PO₄ ³), hydroxyl (OH) and carbonate (CO ^-2) groups of HA. After sintering, XRD analysis showed excellent stability in the BHA structure, represented by a slight change in Mg position. Vickers hardness showed a massive increment from ~4.6 GPa to ~7 GPa as the impurity rate increased. SEM analysis showed a denser microstructure with less porosity as the amount of Mg concentration increased. This research ensured that MgBHA could be potentially applied for medical applications due to the improvement in physical and mechanical properties of HA.

Abstract: Hydroxyapatite (HAp) derived from bovine bone waste is extensively explored for biomedical applications due to its close chemical resemblance to natural bone. However, its intrinsic brittleness and thermal instability remain critical limitations. In this study, HAp–titanium (5–20 wt.%) composites were synthesized using the self-propagating high temperature synthesis (SHS) method within the range of 750–950°C. X-ray diffraction (XRD) analysis confirmed the in-situ formation of CaTiO₃ at 850°C, which significantly improved densification and microstructural consolidation. At higher temperature (950°C), partial decomposition of HAp to tricalcium phosphate (TCP) was observed, consistent with phase evolution trends reported in the literature. Scanning electron microscopy (SEM) revealed distinct grain morphology transitions across the processing window, supporting the identified phase transformations. The results demonstrate a clear correlation between phase evolution and microstructural development: CaTiO₃ formation enhances densification, while TCP contributes to favorable bioresorbability. These findings highlight the tunability of SHS-derived HAp–Ti composites and their promising potential as bone substitute materials with adjustable bioactivity.

Abstract: Percutaneous coronary intervention (PCI) is a minimally invasive treatment for ischemic heart disease, commonly supported by balloon-expandable stents to prevent arterial restenosis. Stent materials must combine high ultimate tensile strength, high ductility, low 0.2% proof strength, high corrosion resistance, high X-ray visibility, and magnetic susceptibility close to that of human soft tissues. The Co-20Cr-15W-10Ni (mass%) alloy, standardized as ASTM F90 and commonly referred to as L605 is widely employed for this purpose. Recently, the demand for stents with smaller diameters and thinner struts has grown, as these significantly lower restenosis risk. Alloys for thin-strut stents therefore require exceptional mechanical and physical performance. This paper reviews the microstructures and mechanical and physical properties of the carbon- and Pt-modified Co-Cr-W-Ni alloys developed by our group. The Co-20Cr-15W-10Ni-0.2C (mass%) alloy achieved an excellent strength–ductility balance and a low 0.2% proof strength owing to the γ-stabilizing effect of carbon. First-principles calculations further revealed that carbon addition increases stacking fault energies (SFEs) in Co-Cr alloys. Pt-modified Co-Cr alloys exhibited higher X-ray visibility than L605 and greater strength than Pt-Cr steel while maintaining comparable ductility. Collectively, these results indicate that carbon- and Pt-modified Co-Cr alloys are promising candidates for next-generation balloon-expandable stents, particularly thin-strut designs.

Abstract: This study developed collagen-PVA hydrogel microneedles containing Aloe vera and Calendula officinalis for wound dressing. Microneedles with different Aloe vera: Calendula officinalis ratios 1:3, 1:1, and 3:1 were evaluated for swelling, mechanical strength, and antibacterial activity. Higher Aloe vera enhanced swelling, flexibility, and Escherichia coli inhibition, while higher Calendula officinalis improved tensile strength and Staphylococcus aureus inhibition. The 1:1 ratio offered the most balanced performance, demonstrating potential for effective wound healing applications.

Abstract: The development of biocomposite nanofiber-based wound dressing materials using Polylactic Acid (PLA), cellulose, and chitosan was carried out through the electrospinning method. The ideal wound dressing should be biocompatible, biodegradable, antibacterial, and able to maintain optimal wound moisture with its water resistance. In this study, various material compositions and electrospinning feed rates were applied to study their effects on water resistance. The solution mixing process was carried out using Dichloromethane and Dimethylformamide solvents, followed by electrospinning at a voltage of 20 kV with a feed rate ranging from 5 ml/hour to 9 ml/hour, characterization included hydrophobicity testing, scanning electron microscope (SEM), and Fourier Transform Infrared (FTIR). The resulting nanofiber-based wound dressing, based on hydrophobicity testing, was found to have the lowest contact angle value at a feed rate of 6 ml/hour with a 100% PLA composition of 77.9096°, and the highest contact angle value at a feed rate of 6 ml/hour with a chitosan and cellulose composition of 89.37°. This indicates that the combination of cellulose and chitosan is able to maintain stable surface properties despite changing process conditions. Overall, the effect of flow rate on surface properties is strongly influenced by material composition, which ultimately determines the contact angle. This contact angle value plays a crucial role in determining water resistance, whether the surface tends to be hydrophilic (readily absorbs water) or hydrophobic (repels water). Keywords: Wound Dressing, Nanofiber, Polylactic Acid, Cellulose, Chitosan, Electrospinning

Abstract: This investigation assessed how incorporating vanillin into a dental adhesive influences bacterial adhesion and biofilm formation. Experimental adhesives, formulated with 0.5% and 1.0% vanillin, were compared against a vanillin-free adhesive and a control using a multi-species biofilm model. No significant differences in bacterial adhesion were observed across the groups, with optical density (OD) values ranging from 0.28 to 0.40. In contrast, adhesives containing vanillin demonstrated a marked reduction in biofilm formation. After 48 hours, the strongest inhibition was recorded for the 1.0% vanillin adhesive (0.63 ± 0.07), followed by the 0.5% vanillin adhesive (0.77 ± 0.04), which were significantly lower than the vanillin-free (1.19 ± 0.08) and control (1.68 ± 0.05) groups. While biofilm accumulation increased in all groups by 72 hours, the vanillin-containing adhesives consistently maintained lower values than the controls. A concentration-dependent effect was confirmed by percent reduction analysis, which showed the 1.0% vanillin adhesive lowered biofilm by 62.5% at 48 hours and 45.0% at 72 hours. Vanillin also suppressed acidogenicity, as reflected by significantly higher culture medium pH values that remained near neutral at both 48 and 72 h, while the vanillin-free adhesive and control dropped below the critical pH 5.5 threshold. These findings suggest that vanillin effectively suppresses biofilm development without impacting bacterial adhesion, potentially serving as a natural additive to enhance the antibacterial properties of dental adhesives and minimize the risk of secondary caries.

Abstract: The long-term performance of dental implants relies on material stability and sustained osseointegration. This study analyzed titanium implant after six years of clinical function and compared it with unused implants to assess surface integrity. Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to evaluate morphology and elemental composition, while surface roughness was measured to detect changes. SEM showed direct bone attachment, and EDX confirmed calcium, phosphorus, sodium, oxygen, and carbon associated with osseointegration. Roughness values increased slightly due to adherent bone tissue, but no evidence of surface wear or degradation was observed. These results demonstrate that titanium maintains chemical stability, biocompatibility, and reliability for long-term dental implant applications.

Abstract: Background: Knee joint replacement surgery is a widely used procedure for managing severe knee osteoarthritis, rheumatoid arthritis, and traumatic arthritis. The selection of implant materials plays a crucial role in the long-term success of the procedure, influencing biomechanical stability, biocompatibility, and wear resistance. Polyether ether ketone (PEEK), a high-performance thermoplastic polymer, has recently gained attention as a potential alternative to conventional metal and polymer implants due to its closer elastic modulus to human bone, excellent biocompatibility, and radiolucency. However, the intrinsic bio-inertness and wear resistance limitations of PEEK have raised concerns regarding its early osseointegration and long-term durability. Methods: To overcome these challenges, researchers have explored various modifications, including bioactive coatings, composite reinforcement, and porous structuring, to enhance it clinical performance. This review evaluates the current applications of PEEK in knee surgery, comparing its properties with commonly used materials such as ultra-high-molecular-weight polyethylene (UHMWPE), cobalt-chromium (CoCr), and titanium. Results: We analyze its role in procedures such as high tibial osteotomy (HTO) and anterior cruciate ligament reconstruction (ACLR). While PEEK demonstrates promising mechanical and biological advantages, further studies on long-term performance, wear behavior, and improved osseointegration techniques are essential to determine its suitability as a standard implant material in knee surgery. Conclusions: PEEK has the potential to serve as an alternative implant material for knee joint replacement due to its biomechanical compatibility and favorable biological properties. However, addressing its bio-inertness and wear resistance limitations through material modifications remains a key area for future research.

Abstract: β Ti-18Mo-xCr alloy has been widely used as an orthopedic implant material because this alloy has the advantage of high strength a lower modulus of elasticity than commercial alloys Ti-6Al-4V, good corrosion resistance. and formability. This research aims to find alloys with high corrosion resistance and low modulus of elasticity and identify the presence of phase β after heat treatment. Ti-18Mo-7Cr is obtained from the melting process using an arc melting furnace followed by heat treatment (solution and aging treatment). To determine the modulus of elasticity using a sonelastic tool and hardness test using Microhardness Vickers. The EIS method was used to determine the corrosion resistance using a 0.9% NaCl solution as a simulated body fluid. The modulus of elasticity owned by the solution treatment alloy tends to be lower than that of the aging alloy. The lowest elastic modulus value and the highest hardness value are found in the Ti-18Mo-7Cr ST850 alloy, which is 91 GPa and 471.42 HV. For corrosion resistance, the aging treatment alloy shows a lower corrosion rate than the solution treatment alloy and is much lower than that of the Ti-6Al-4V alloy. On the other hand, the solution treatment can stabilize the β phase and reduce the corrosion rate due to heating below transus temperature, but aging with a longer holding time can also reduce corrosion resistance more than the corrosion resistance of the solution treatment. The alloy Ti-18Mo-7Cr AT500 has the lowest corrosion rate among the samples in this study, which is 0,0004225 mmpy.