Load-bearing Orthopedic Applications Research Articles

A strategy for enhancing bioactivity and osseointegration with antibacterial effect by incorporating magnesium in polylactic acid based biodegradable orthopedic implant

Biodegradable orthopedic implants are essential for restoring the physiological structure and function of bone tissue while ensuring complete degradation after recovery. Polylactic acid (PLA), a biodegradable polymer, is considered a promising material due to its considerable mechanical properties and biocompatibility. However, further improvements are necessary to enhance the mechanical strength and bioactivity of PLA for reliable load-bearing orthopedic applications. In this study, a multifunctional PLA-based composite was fabricated by incorporating tricalcium phosphate (TCP) microspheres and magnesium (Mg) particles homogenously at a volume fraction of 40 %. This approach aims to enhance mechanical strength, accelerate pore generation, and improve biological and antibacterial performance. Mg content was incorporated into the composite at varying values of 1, 3, and 5 vol% (referred to as PLA/TCP-1 Mg, PLA/TCP-3 Mg, and PLA/TCP-5 Mg, respectively). The compressive strength and stiffness were significantly enhanced in all composites, reaching 87.7, 85.9, and 84.1 MPa, and 2.7, 3.0, and 3.1 GPa, respectively. The degradation test indicated faster elimination of the reinforcers as the Mg content increased, resulting in accelerated pore generation to induce enhanced osseointegration. Because PLA/TCP-3 Mg and PLA/TCP-5 Mg exhibited cracks in the PLA matrix due to rapid corrosion of Mg forming corrosion byproducts, to optimize the Mg particle content, PLA/TCP-1 Mg was selected for further evaluation. As determined by in vitro biological and antibacterial testing, PLA/TCP-1 Mg showed enhanced bioactivity with pre-osteoblast cells and exhibited antibacterial properties by suppressing bacterial colonization. Overall, the multifunctional PLA/TCP-Mg composite showed improved mechanobiological performance, making it a promising material for biodegradable orthopedic implants.

A novel in-situ synthesized bioactive TaZrTi alloy by high energy laser beam for total knee arthroplasty application

Total knee arthroplasty is the gold standard treatment for end-stage knee osteoarthritis, which could significantly improve function and relieve pain for patients. However, the present materials and manufacturing approaches are dissatisfactory for knee implants. In the present work, a Ta60-Zr20-Ti20 (in wt%) coating was in-situ synthesized onto Ti6Al4V alloy via a high energy laser beam. The microstructure analysis indicated that α-Ta/ZrTi solid solution generated into body-centered cubic (bcc) grains in dimensions of several to hundred micrometers. The Ta-riched dendrites nucleated, grew, and expanded in the ZrTi matrix. The mechanical and biological properties of the in-situ synthesized TaZrTi sample are compared with the conventionally rolled Ti6Al4V, which is also the substrate alloy. The mean values of hardness and elastic modulus of in-situ synthesized TaZrTi tested by the nanoindenter, are 10.31 and 134.84 GPa, respectively. These results are harder than the Ti6Al4V counterpart (5.14 GPa) with a preferred slightly low elastic modulus (152.95 GPa of Ti6Al4V). Subsequently, the in-situ synthesized TaZrTi exhibits an excellent wear resistance demonstrated by nano-scratch experiments. In addition, the osteoblastic and endothelial cells were cultured in vitro to evaluate the biocompatibility of in-situ synthesized TaZrTi. The results show a comparable bioactivity and surface affinity compared with the rolled Ti6Al4V in 7 days. Briefly, this in-situ synthesized TaZrTi alloy is expected to shed light on load-bearing orthopedic applications to relieve the pain of patients, and the findings in this study provide an insightful understanding of laser additive manufactured TaZrTi alloy.

Effect of Different Contents of 63s Bioglass on the Performance of Bioglass-PCL Composite Bone Scaffolds

Bioactive glasses (BG), notably 63s BG, possess distinct properties such as biodegradability, biocompatibility, and the ability to boost cellular interactions. Our research concentrated on formulating polycaprolactone (PCL) porous scaffolds enriched with 63s BG to gauge their combined mechanical and biological potentials. Using twin-screw extrusion, we created composites containing 5%, 10%, and 20% 63s BG. These were transformed into cylindrical scaffolds using 3D printing. Our assessments involved melt flow, SEM, XRD, water contact angle metrics, DSC, and extracorporeal degradation. After co-culturing with MC3T3-E1 cells, an uptick in alkaline phosphatase activity was noted. Preliminary findings demonstrated that as 63s BG content increased, the properties of the composites improved. Yet, they fell short of replicating the mechanical nuances of cortical bone, rendering them inapt for load-bearing orthopedic applications but suitable for mending minor bone defects or cartilage. In summary, while 63s BG brings about significant advancements in scaffold attributes, attaining the mechanical traits ideal for certain medical purposes remains elusive. This investigation offers foundational insights for the evolution of optimized bone tissue engineering materials.

TUNING OF HYDROXYAPATITE WITH NANOPARTICLES OF MULTIPLE METAL OXIDES

Fabrication and commercial application of nano-hydroxyapatite synthetic bioceramic compound is being implemented immensely worldwide in medicine, dentistry, and ceramic industries. In this experimental study, nano-hydroxyapatite has been prepared through the sol-gel method and doped with nano-silica, nano-alumina, and sodium zeolite. The main objective of this study is to improve the properties of nano-hydroxyapatite doped with nanoparticles of different metal oxides for load-bearing orthopaedic applications. The metal oxides have been doped in pure nano-hydroxyapatite by two different methods: physical attachment and chemical methods. After blending these metal oxides in nano-hydroxyapatite powder, comprehensive characterizations of compositional, structural, morphological, thermal, and mechanical properties have been determined through X-ray diffraction, Scanning Electron Microscope, Raman Spectroscopy, Thermogravimetric Analysis, respectively. The experimental outcomes revealed that all properties of the nano-hydroxyapatite material have been improved significantly with doping of metal oxides while nano-alumina was the most effective metal oxide.

Fatigue behaviour of titanium scaffolds with hierarchical porosity produced by material extrusion additive manufacturing

Metallic porous structures (scaffolds) produced by additive manufacturing represent an important class of personalised implants used in load-bearing orthopaedic applications. As such, their fatigue performance must be excellent to prevent the need for revision surgery. This paper provides insight into the high-cycle fatigue behaviour of novel titanium scaffolds with hierarchical porosity and properties comparable to those of human bone that were produced by direct ink writing (DIW) and tested under cyclic loading typical for bone implants. Opposite to traditional expectations in the field of metal fatigue, scaffolds produced with an open intrastrand pore network (14.3%) endured nearly an order of magnitude more cycles than those with relatively compact strands (5.9%) and their normalized fatigue strength (62% of their yield strength in 106 cycles) was competitive with many current titanium scaffolds produced by other additive manufacturing technologies. Improved fatigue performance was related to fatigue crack growth shielding effects that reduced the crack growth rate, prolonged the crack path, and increased energy absorption. Consequently, these novel hierarchically porous titanium structures prepared by DIW can serve safely under cyclic loading conditions, and at the same time can provide multiple open porosity-related functionalities in advanced biomedicine and other industrial sectors.

Microstructural, dielectric, mechanical, and biological properties of hydroxyapatite (HAp)/BZT-BCT (0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3) bio-composites with improved mechano-electrical properties for bone repair

Hydroxyapatite (HAp; Ca10(PO4)6(OH)2) is a commonly used biomaterial for bone tissue repair applications but it has poor electrical conductivity. Whereas, BZT-BCT (0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3) is a lead-free piezoelectric material which can mimic the stress-generated electric potential of electrically-excitable tissues such as bone. This study investigated the mechanical, electrical and bio properties of xHAp/(1-x)BZT-BCT composites. xHAp/(1-x)BZT-BCT composites (with x = 5, 10, 15 and 20 wt%) were synthesized by high energy ball milling (HEBM) assisted solid-state reaction route. X-ray diffraction, scanning electron microscopy, density measurements and cell-material interaction studies of sintered HAp/BZT-BCT composites were carried out and discussed in detail. Dielectric properties of sintered composites were evaluated and compared with the existing theoretical models. Different mechanical properties like Vicker's hardness, fracture toughness, and diametral tensile strength were measured to assess the usability of synthesized composites for load-bearing orthopaedic applications. These various studies showed that incorporation of BZT-BCT in HAp improved its mechanical and electrical properties and thereby significantly increased the proliferation of human osteogenic MG-63 cells. Among all the composites, better mechanical, electrical and biological properties were obtained in 10HAp/90BZT-BCT composites.

Promises of Functionally Graded Material in Bone Regeneration: Current Trends, Properties, and Challenges.

Functionally graded materials (FGMs) are emerging materials systems, with structures and compositions gradually changing in a particular direction. Consequently, the properties of the materials gradually change in the desired direction to achieve particular nonhomogeneous service demands without abrupting the compositional and behavioral interface at the macroscale. FGMs have been found to have high potential as orthopedic implants; because the functional gradient can be adapted in such a manner that the core of FGM should be compatible with the density and strength of bone, interlayers can maintain the structural integrity and outermost layers would provide bioactivity and corrosion resistance, thus overall tailoring the stress shielding effect. This review article discusses the typical FGM systems existing in nature and the human body, focusing on bone tissue. Further, the reason behind the application of these FGMs systems in orthopedic implants is explored in detail, considering the physical and biological necessities. The substantial focus of the present critical review is devoted to two primary topics related to the usage of FGMs for orthopedic implants: (1) the synthesizing techniques currently available to produce FGMs for load-bearing orthopedic applications and (2) the properties, such as mechanical, structural, and biological behavior of the FGMs. This review article gives an insight into the potential of FGMs for orthopedic applications.

Fatigue behaviour and biocompatibility of additively manufactured bioactive tantalum graded lattice structures for load-bearing orthopaedic applications

Laser powder bed fusion (LPBF) additive manufacturing of pure tantalum and their graded lattice structures was systematically investigated, with emphasis on their microstructure evolution, phase formation, surface energy and biological properties in comparison with conventionally forged pure Ta. The LPBF fabricated Ta (LPBF-Ta) exhibited lower contact angles and higher surface energy than the forged-Ta which indicated the better wettability of the LPBF-Ta. The adhesion and proliferation of rat bone marrow stromal cells (rBMSCs) were also enhanced for the LPBF-Ta when compared to forged-Ta. Three different Ta graded gyroid lattice structures (i.e., uniform structure, Y-gradient structure, Z-gradient structure) were designed and fabricated using the same optimised LPBF parameters. Y-gradient structures exhibited the best plateau stress and compressive modulus among three different graded structures due to the maximum local volume fraction on the fracture plane. In fatigue response, Y-gradient outperformed the other two gyroid structures under varying stresses. In terms of cell culture response, the uniform structures performed the best biocompatibility due to its suitable pore size for cell adhesion and growth. This study provides new and in-depth insights into the LPBF additive manufacturing of pure Ta graded lattice structures with desired fatigue and biological properties for load-bearing orthopaedic applications.

The Effect of Energy Density and Nb Content on the Microstructure and Mechanical Properties of Selective Laser Melted Ti-(10-30 wt.%) Nb

In this study, Ti-(0-30 wt.%)Nb alloys developed from elemental powders were fabricated by the Selective Laser Melting (SLM) process. Compositional homogeneity, microstructure and mechanical performance were investigated as a function of energy density. The proportion of un-melted Nb particles and isolated pore count reduced with increasing energy density, while Ti allotropic content (i.e. α’, α” and β) varied with energy density due to in-situ alloying. Increasing the Nb content led to the stabilisation of the α” and β phases. The mechanical properties were similar to those compositions manufactured using casting methods, without further post processing. The addition of 20Nb (wt.%) and using an energy density of 230 J/mm3 resulted in a Young’s Modulus of 65.2 ± 1.8 GPa, a yield strength of 769 ± 36 MPa and a microstructure of predominantly α” martensite. This strength to stiffness ratio (33% higher than Ti-10Nb and 22% higher than Ti-30Nb), is attributed to in-situ alloying that promotes solid solution strengthening and homogenisation. These alloys are strong contenders as materials suitable for implantable load-bearing orthopaedic applications.

In vivo performance of Al2O3-Ti bone implants in the rat femur

BackgroundAlumina-titanium (Al2O3-Ti) biocomposites have been recently developed with improved mechanical properties for use in heavily loaded orthopedic sites. Their biological performance, however, has not been investigated yet.MethodsThe aim of the present study was to evaluate the in vivo biological interaction of Al2O3-Ti. Spark plasma sintering (SPS) was used to fabricate Al2O3-Ti composites with 25 vol.%, 50 vol.%, and 75 vol.% Ti content. Pure alumina and titanium were also fabricated by the same procedure for comparison. The fabricated composite disks were cut into small bars and implanted into medullary canals of rat femurs. The histological analysis and scanning electron microscopy (SEM) observation were carried out to determine the bone formation ability of these materials and to evaluate the bone-implant interfaces.ResultsThe histological observation showed the formation of osteoblast, osteocytes with lacuna, bone with lamellar structures, and blood vessels indicating that the healing and remodeling of the bone, and vasculature reconstruction occurred after 4 and 8 weeks of implantation. However, superior bone formation and maturation were obtained after 8 weeks. SEM images also showed stronger interfaces at week 8. There were differences between the composites in percentages of bone area (TB%) and the number of osteocytes. The 50Ti composite showed higher TB% at week 4, while 25Ti and 75Ti represented higher TB% at week 8. All the composites showed a higher number of osteocytes compared to 100Ti, particularly 75Ti.ConclusionsThe fabricated composites have the potential to be used in load-bearing orthopedic applications.

Multi-scale nacre-inspired lamella-structured Ti-Ta composites with high strength and low modulus for load-bearing orthopedic and dental applications.

Mimicking the hierarchical structure of nacre in artificial materials is a promising approach to obtain high mechanical performance. In this work, nacre-inspired lamella-structured Ti-Ta composites were fabricated by successive spark plasma sintering, mechanical processing and annealing. The specimen sintered at 1200°C and then hot rolled with 60% height reduction exhibited multi-scale lamellar microstructure. At micro-scale, the composite was composed of alternate Ti-enriched and Ta-enriched micro-bands. At nano-scale, highly-ordered lamellar structures consisted of Ti-enriched and Ta-enriched nano-lamellae were found near Ti/Ta micro-bands. The biomimetic-structured Ti-Ta composite possessed appropriate combination of strength (1030MPa ultimate tensile strength) and ductility (10.2% elongation), which is much stronger than pure Ti and comparably strong as Ti-6Al-4V. Moreover, the biomimetic-structured Ti-Ta composite possessed low modulus (80.6GPa). In vitro cell culture experiment revealed that the biomimetic-structured Ti-Ta composite was cytocompatible, evidenced by the well-spread morphology and favorable growth of human bone mesenchymal stem cells (hBMSCs) on material surface. A rat femoral fracture model was employed to evaluate the therapeutic performance of biomimetic-structured Ti-Ta composite implant on fracture healing compared to that of pure Ti. In vivo results showed that the composite implant enhanced fracture healing in rats. Together, the findings obtained in the current work suggest that mimicking the hierarchical structure of nacre in Ti-Ta composite is an effective way for material strengthening. Moreover, the biomimetic-structured Ti-Ta composite with high strength, good ductility, low modulus and favorable biocompatibility is promising for load-bearing applications in orthopedic and dental area.

Addition of Sn to TiNb alloys to improve mechanical performance and surface properties conducive to enhanced cell activity.

Titanium (Ti) alloys with Niobium (Nb) and Tin (Sn) were prepared in order to conduct a systematic study on the bulk and surface properties of as-cast c.p.Ti, binary Ti-40Nb and Ti-10Sn, and ternary Ti-10Nb-5Sn (at.%) to ascertain whether Sn content can be used as an enhancer for cell activity. From a metallurgy viewpoint, a range of binary and ternary alloys displaying distinctive Ti phases (i.e. β, α', α") were achieved at room temperature. Their surface (oxide thickness and composition, roughness, contact angle) and bulk (compressive stiffness, strength, elongation, microhardness, electrical resistance) features were characterised. The same surface roughness was imparted on all the alloys, therefore substrate-cell interactions were evaluated independently from this variable. The physico-mechanical properties of the ternary alloy presented the highest strength to stiffness ratio and thereby proved the most suitable for load-bearing orthopaedic applications. From a cellular response viewpoint, their cytotoxicity, ability to adsorb proteins, to support cell growth and to promote proliferation were studied. Metabolic activity using a mouse model was monitored for a period of 12 days to elucidate the mechanism behind an enhanced proliferation rate observed in the Sn-containing alloys. It was hypothesised that the complex passivating surface oxide layer and the bulk inhomogeneity with two dominant Ti phases were responsible for this phenomenon.

Rationally designed functionally graded porous Ti6Al4V scaffolds with high strength and toughness built via selective laser melting for load-bearing orthopedic applications

Functionally graded materials (FGMs) with porosity variation strategy mimicking natural bone are potential high-performance biomaterials for orthopedic implants. The architecture of FGM scaffold is critical to gain the favorable combination of mechanical and biological properties for osseointegration. In this study, four types of FGM scaffolds with different structures were prepared by selective laser melting (SLM) with Ti6Al4V as building material. All the scaffolds were hollow cylinders with different three-dimensional architectures and had gradient porosity resembling the graded-porous structure of human bone. Two unit cells (diamond and honeycomb-like unit cells) were used to construct the cellular structures. Solid support structures were embedded into the cellular structures to improve their mechanical performances. The physical characteristics, mechanical properties, and deformation behaviors of the scaffolds were compared systematically. All the as-built samples with porosities of ~52–67% exhibited a radial decreasing porosity from the inner layer to the outer layer, and their pore sizes ranged from ~420 to ~630 μm. The compression tests showed the Young's moduli of all the as-fabricated samples (~3.79–~10.99 GPa) were similar to that of cortical bone. The FGM structures built by honeycomb-like unit cells with supporting structure in outer layer exhibited highest yield strength, toughness and stable mechanical properties which is more appropriate to build orthopedic scaffolds for load-bearing application.

Probing the Influence of γ-Sterilization on the Oxidation, Crystallization, Sliding Wear Resistance, and Cytocompatibility of Chemically Modified Graphene-Oxide-Reinforced HDPE/UHMWPE Nanocomposites and Wear Debris.

Osteolysis and aseptic loosening due to wear at the articulating interfaces of prosthetic joints are considered to be the key concerns for implant failure in load-bearing orthopedic applications. In an effort to reduce the wear and processing difficulties of ultrahigh-molecular-weight polyethylene (UHMWPE), our research group recently developed high-density polyethylene (HDPE)/UHMWPE nanocomposites with chemically modified graphene oxide (mGO). Considering the importance of sterilization, this work explores the influence of γ-ray dosage of 25 kGy on the clinically relevant performance-limiting properties of these newly developed hybrid nanocomposites in vitro. Importantly, this work also probes into the cytotoxic effects of the wear debris of different compositions and sizes on MC3T3 murine osteoblasts and human mesenchymal stem cells (hMSCs). In particular, γ-ray-sterilized 1 wt % mGO-reinforced HDPE/UHMWPE nanocomposites exhibit an improvement in the oxidation index (16%), free energy of immersion (-12.1 mN/m), surface polarity (5.0%), and hardness (42%). Consequently, such enhancements result in better tribological properties, especially coefficient of friction (+13%) and wear resistance, when compared with UHMWPE. A spectrum of analyses using transmission electron microscopy (TEM) and in vitro cytocompatibility assessment demonstrate that phagocytosable (0.5-4.5 μm) sterilized 1 mGO wear particles, when present in culture media at 5 mg/mL concentration, induce neither significant reduction in MC3T3 murine osteoblast and hMSC growth nor cell morphology phenotype, during 24, 48, and 72 h of incubation. Taken together, this study suggests that γ-ray-sterilized HDPE/UHMWPE/mGO nanocomposites can be utilized as promising articulating surfaces for total joint replacements.

New network architectures with tunable mechanical properties inspired by origami

From chemistry-based methods to physics-based methods, there are many techniques to construct porous scaffolds for use in tissue engineering. Among them, computer-aided design (CAD) methods combined with additive manufacturing techniques are promising because they allow accurate control of complex scaffold morphology. Inspired by an ancient art, origami, we propose a novel CAD solution for building porous scaffolds with adjustable overall topologies and mechanical properties tuned by the origami-based parameters. Here, we mainly focus on (1) how to obtain a network from an origami structure and how to fabricate it, (2) how to change the network's topology and mechanical properties by tuning the folding angles and plane angles. With the same porosity, it has been demonstrated that the origami-inspired network's stiffness, yield strength, and ultimate compressive strength are much higher than those of other reported networks, which results from the architecture designed by the origami-inspired design concept. This interesting concept can bridge the gap between origami-based networks and load-bearing orthopedic applications with mechanical biomimetic design, but it is not limited to medical applications.

Evaluation of mechanical properties and hemocompatibility of open cell iron foams with polyethylene glycol coating

The increasing demand for improved implant biomaterials encourages their design and development. Degradable biomaterials have gained considerable attention especially in the past few decades. Metallic biomaterials are commonly applied in current medical practice to replace or repair diseased tissue. Structural materials with appropriate mechanical properties are required for load-bearing orthopedic applications. Moreover, biomaterials must fulfil the safety requirements and exhibit reasonable degradation rates to support the failing tissue and allow a gradual load transfer to the healing bone. Metal foams with open cell structure allow the transport of body fluids, growth of new tissues, improvement of degradation rate and reduction of the stress shielding phenomenon. In this work, iron open cell foams were fabricated by means of powder metallurgy processes. The hemocompatibility and mechanical properties of the porous iron materials without and with polyethylene glycol (PEG) coating were evaluated depending on the time of immersion in a simulated body fluid. It has been discovered, that PEG layer has increased the density and strength of iron foams. A mechanism of corrosion of iron foams with PEG coating layer was proposed. The suppression of hemolysis extension, platelet adhesion, and thrombus formation due to the polymer layer was observed as a result.

Three-dimensional cellulose-hydroxyapatite nanocomposite enriched with dexamethasone loaded metal–organic framework: a local drug delivery system for bone tissue engineering

Three-dimensional cellulose-hydroxyapatite nanocomposite integrated with dexamethasone loaded metal organic framework (HA/DMOF) has been synthesized as a local drug delivery system for bone tissue engineering. Initially, in situ dexamethasone encapsulated metal–organic frameworks (DMOFs) were developed and characterized. The synthesized DMOFs are 60–80 nm in size with rhombohedral morphology. Results showed that nearly 16% dexamethasone (Dex) was loaded in DMOFs. These synthesized DMOF nanoparticles were efficiently integrated with carboxymethyl cellulose-hydroxyapatite nanocomposite for the development of three dimensional localized drug delivery system, namely, HA/DMOF. The synthesized HA/DMOF nanocomposite was structurally characterized using various techniques. The mechanical properties of HA/DMOFs were also measured by means of compression test. It was found that the compressive strength and compressive modulus of HA/DMOF nanocomposite are 16.3 ± 1.57 MPa and 0.54 ± 0.073 GPa respectively, which are in the range of cancellous bone. In-vitro release behaviour of Dex from both DMOFs and HA/DMOFs was examined in phosphate buffered solution. It was found that Dex molecules have been released very slowly from HA/DMOF nanocomposite compared to DMOF nanoparticles, and it was sustained for 4 weeks. Cytocompatibility of HA/DMOF nanocomposite was evaluated against pre-osteoblast MC3T3 cells. It was found that the synthesized HA/DMOF nanocomposite is compatible to MC3T3 cells. Moreover, the ALP activity and extracellular mineralization capability of cells were enhanced when cultured with HA/DMOF nanocomposite. Results showed that the synthesized HA/DMOF nanocomposite is a promising material for possible therapeutic as well as load-bearing orthopedic applications.

Effects of Aloe Vera Gel Extract in Doped Hydroxyapatite-Coated Titanium Implants on in Vivo and in Vitro Biological Properties.

Hydroxyapatite-coated titanium alloys have been a popular choice as bone implants for load-bearing applications for the compositional similarity of hydroxyapatite to natural bone. The limited osteoinductive properties exhibited by the hydroxyapatite (HA) coatings have led to the incorporation of growth factor or dopants for improved osseointegration. This study aims to investigate the effects of a naturally occurring aloe vera gel extract, acemannan, in doped hydroxyapatite coatings on the in vitro osteoblast cell viability and in vivo new bone formationin a rat distal femur model. Silver oxide and silica-doped hydroxyapatite coatings were developed by the induction plasma spray coating method on Ti alloys to introduce antibacterial properties along with induction of angiogenic properties, respectively. The doped coating was further consecutively dip coated with acemannan to analyze its effects on the in vivo early stage osseointegration and chitosan to control the burst release of the acemannan from the calcium phosphate matrix. The results show controlled release of acemannan from the chitosan coatings, with enhanced osteoblast cell viability by the incorporation of acemannan in vitro. Improved osseointegration with a seamless implant interface and improved new bone formation was noted by the acemannan and chitosan coating in vivo, 5 weeks after implantation. Our results demonstrate the efficacy of a combination of natural medicine and naturally occurring polymer in a doped hydroxyapatite-coated titanium implant on the bone tissue regeneration for load-bearing orthopedic applications.

Protein adsorption and biodegradation behaviour of Mg–3Zn/HA for biomedical application

Orthopaedic implants demand a new domain of biodegradable materials to avoid second surgery after healing and stress shielding – problems that are associated with clinically used metallic implants. Magnesium (Mg) is a suitable replacement for avoiding stress shielding and second surgery in load-bearing orthopaedic applications. However, the main challenge with magnesium is its high corrosion rate in the physiological environment. Biodegradable magnesium-based composites reinforced with hydroxyapatite (HA) can help in improving corrosion resistance. An effort has been taken here to improve the degradation behaviour and bioactivity of magnesium–HA composites prepared through conventional sintering. Immersion tests in simulated body fluid and fetal bovine serum reveal ∼22% improvement in corrosion resistance in the latter case. The interaction of proteins with the biomaterial surface is of crucial importance in implants as adsorbed proteins define immediate cell attachment and proliferation on the surfaces. In this study, the mechanism of protein adsorption on composites is also analysed. It was observed that ∼40% more protein was adsorbed by the 5 wt% HA-reinforced composite (M5H) in 3 h compared to the structure without HA (M0H). Adsorption of more proteins on the surface of M5H implants indicates better cell proliferation ability and better corrosion resistance, making them a very promising candidate for biodegradable orthopaedic implants.

Polylactide Composite Pins Reinforced with Bioresorbable Continuous Glass Fibers Demonstrating Bone-like Apatite Formation and Spiral Delamination Degradation.

The emergence of polylactide composites reinforced with bioresorbable silicate glass fibers has allowed for the long-term success of biodegradable polymers in load-bearing orthopedic applications. However, few studies have reported on the degradation behavior and bioactivity of such biocomposites. The aim of this work was to investigate the degradation behavior and in vitro bioactivity of a novel biocomposite pin composed of bioresorbable continuous glass fibers and poly-L-D-lactide in simulated body fluid for 78 weeks. As the materials degraded, periodic spiral delamination formed microtubes and funnel-shaped structures in the biocomposite pins. It was speculated that the direction of degradation, from both ends towards the middle of the fibers and from the surface through to the bulk of the polymer matrix, could facilitate bone healing. Following immersion in simulated body fluid, a bone-like apatite layer formed on the biocomposite pins which had a similar composition and structure to natural bone. The sheet- and needle-like apatite nanostructure was doped with sodium, magnesium, and carbonate ions, which acted to lower the Ca/P atomic ratio to less than the stoichiometric apatite and presented a calcium-deficient apatite with low crystallinity. These findings demonstrated the bioactivity of the new biocomposite pins in vitro and their excellent potential for load-bearing applications.