Plasma sprayed fluoride and zinc doped hydroxyapatite coated titanium for load-bearing implants

Advanced surface modification techniques for titanium implants: a review of osteogenic and antibacterial strategies

Titanium (Ti) implants are widely used in orthopedic and dental applications due to their excellent mechanical strength, corrosion resistance, and biocompatibility. However, their limited osteointegration and susceptibility to bacterial infections remain major clinical challenges. Recent advancements in surface modification techniques have significantly improved the osteogenic and antibacterial properties of Ti implants. This review summarizes key strategies, including ion doping, hydroxyapatite (HAp) coatings, nanostructured surfaces, and graphene-based modifications. Zinc (Zn)-doped coatings increase osteoblast proliferation by 25%, enhance cell adhesion by 40%, and inhibit Staphylococcus aureus by 24%. Magnesium (Mg)-doped Ti surfaces enhance osteoblast differentiation, with 38% increased alkaline phosphatase (ALP) activity and a 4.5-fold increase in cell proliferation. Copper (Cu)-doped coatings achieve 99.45% antibacterial efficacy against S. aureus and 98.65% against Escherichia coli (E. coli). Zn-substituted HAp promotes mineralized nodule formation by 4.5-fold and exhibits 16.25% bacterial inhibition against E. coli. Graphene-based coatings stimulate bone marrow stem cells (BMSCs) and provide light-responsive surface potentials for enhanced osteogenesis. Despite these advancements, challenges remain in optimizing ion release kinetics and long-term stability. Future research should focus on multi-functional coatings that integrate osteogenic, antibacterial, and immunomodulatory properties to enhance clinical performance and patient outcomes.

Application of advanced surface modification techniques in titanium-based implants: latest strategies for enhanced antibacterial properties and osseointegration

Titanium-based implants, renowned for their excellent mechanical properties, corrosion resistance, and biocompatibility, have found widespread application as premier implant materials in the medical field. However, as bioinert materials, they often face challenges such as implant failure caused by bacterial infections and inadequate osseointegration post-implantation. Thus, to address these issues, researchers have developed various surface modification techniques to enhance the surface properties and bioactivity of titanium-based implants. This review aims to outline several key surface modification methods for titanium-based implants, including acid etching, sol-gel method, chemical vapor deposition, electrochemical techniques, layer-by-layer self-assembly, and chemical grafting. It briefly summarizes the advantages, limitations, and potential applications of these technologies, presenting readers with a comprehensive perspective on the latest advances and trends in the surface modification of titanium-based implants.

The Application Progress of Nonthermal Plasma Technology in the Modification of Bone Implant Materials

With the accelerating trend of global aging, bone damage caused by orthopedic diseases, such as osteoporosis and fractures, has become a shared international event. Traffic accidents, high-altitude falls, and other incidents are increasing daily, and the demand for bone implant treatment is also growing. Although extensive research has been conducted in the past decade to develop medical implants for bone regeneration and healing of body tissues, due to their low biocompatibility, weak bone integration ability, and high postoperative infection rates, pure titanium alloys, such as Ti-6A1-4V and Ti-6A1-7Nb, although widely used in clinical practice, have poor induction of phosphate deposition and wear resistance, and Ti-Zr alloy exhibits a lack of mechanical stability and processing complexity. In contrast, the Ti-Ni alloy exhibits toxicity and low thermal conductivity. Nonthermal plasma (NTP) has aroused widespread interest in synthesizing and modifying implanted materials. More and more researchers are using plasma to modify target catalysts such as changing the dispersion of active sites, adjusting electronic properties, enhancing metal carrier interactions, and changing their morphology. NTP provides an alternative option for catalysts in the modification processes of oxidation, reduction, etching, coating, and doping, especially for materials that cannot tolerate thermodynamic or thermosensitive reactions. This review will focus on applying NTP technology in bone implant material modification and analyze the overall performance of three common types of bone implant materials, including metals, ceramics, and polymers. The challenges faced by NTP material modification are also discussed.

Hydroxyapatite nano-pillars on TI-6Al-4V: Enhancements in cell spreading and proliferation during cell/surface integration

Despite the attractive combinations of cell/surface interactions, biocompatibility, and good mechanical properties of Ti-6Al-4V, there is still a need to enhance the early stages of cell/surface integration that are associated with the implantation of biomedical devices into the human body. This paper presents a novel, easy and reproducible method of nanoscale and nanostructured hydroxyapatite (HA) coatings on Ti-6Al-4V. The resulting nanoscale coatings/nanostructures are characterized using a combination of Raman spectroscopy, scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanostructured/nanoscale coatings are shown to enhance the early stages of cell spreading and integration of bone cells (hFOB cells) on Ti-6Al-4V surfaces. The improvements include the acceleration of extra-cellular matrix, cell spreading and proliferation by nanoscale HA structures on the coated surfaces. The implications of the results are discussed for the development of HA nanostructures for the improved osseointegration of Ti-6Al-4V in orthopedic and dental applications.

Physico-Chemical and Biological Features of Fluorine-Substituted Hydroxyapatite Suspensions

Infections related to orthopedic/stomatology surgery are widely recognized as a significant health concern. Therefore, the development of new materials with superior biological properties and good stability could represent a valuable alternative to the classical treatments. In this paper, the fluorine-substituted hydroxyapatite (FHAp) suspension, with the chemical formula Ca10(PO4)6(OH)2-2xF2x (where x = 0.05), was prepared using a modified coprecipitation technique. Stability studies were conducted by zeta potential and ultrasound measurements for the first time. The X-ray diffraction (XRD) patterns of FHAp powders displayed a hexagonal structure akin to that of pure hydroxyapatite (HAp). The XPS general spectrum revealed peaks corresponding to the constituent elements of fluorine-substituted hydroxyapatite such as calcium, phosphorus, oxygen, and fluorine. The purity of the obtained FHAp samples was confirmed by energy-dispersive X-ray spectroscopy (EDS) studies. The FHAp morphology was evaluated by scanning electron microscopy (SEM) measurements. Fourier-transform infrared spectroscopy (FTIR) studies were performed in order to study the vibrational properties of the FHAp samples. The FHAp suspensions were tested for antibacterial activity against reference strains such as Staphylococcus aureus 25923 ATCC, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231. Additionally, the biocompatibility of the FHAp suspensions was assessed using human fetal osteoblastic cells (hFOB 1.19 cell line). The results of our biological tests suggest that FHAp suspensions are promising candidates for the future development of new biocompatible and antimicrobial agents for use in the biomedical field.

The Incorporation of Zinc into Hydroxyapatite and Its Influence on the Cellular Response to Biomaterials: A Systematic Review

Zinc is known for its role in enhancing bone metabolism, cell proliferation, and tissue regeneration. Several studies proposed the incorporation of zinc into hydroxyapatite (HA) to produce biomaterials (ZnHA) that stimulate and accelerate bone healing. This systematic review aimed to understand the physicochemical characteristics of zinc-doped HA-based biomaterials and the evidence of their biological effects on osteoblastic cells. A comprehensive literature search was conducted from 2022 to 2024, covering all years of publications, in three databases (Web of Science, PUBMED, Scopus), retrieving 609 entries, with 36 articles included in the analysis according to the selection criteria. The selected studies provided data on the material's physicochemical properties, the methods of zinc incorporation, and the biological effects of ZnHA on bone cells. The production of ZnHA typically involves the wet chemical synthesis of HA and ZnHA precursors, followed by deposition on substrates using processes such as liquid precursor plasma spraying (LPPS). Characterization techniques confirmed the successful incorporation of zinc into the HA lattice. The findings indicated that zinc incorporation into HA at low concentrations is non-cytotoxic and beneficial for bone cells. ZnHA was found to stimulate cell proliferation, adhesion, and the production of osteogenic factors, thereby promoting in vitro mineralization. However, the optimal zinc concentration for the desired effects varied across studies, making it challenging to establish a standardized concentration. ZnHA materials are biocompatible and enhance osteoblast proliferation and differentiation. However, the mechanisms of zinc release and the ideal concentrations for optimal tissue regeneration require further investigation. Standardizing these parameters is essential for the effective clinical application of ZnHA.

Curcumin and resveratrol delivery from multi-functionalized calcium phosphate scaffold enhances biological properties

Natural medicinal compounds (NMCs) can assist effectively in treating bone disorders. NMC release kinetics from a ceramic bone tissue engineering scaffold can be tailored. However, inferior physicochemical properties halt their therapeutic applications and need a carrier system for delivery. We developed a multi-functionalized scaffold to understand the effect of curcumin (Cur) and resveratrol (Rsv) on in vitro biological properties. Polycaprolactone (PCL) nanoparticles encapsulated resveratrol in the polymeric matrix. Nanoparticles showed a hydrodynamic diameter of about 180 nm, - 16 mV zeta potential, and up to ~65 % encapsulation efficiency. Scaffolds made of zinc-doped tricalcium phosphate (Zn-TCP) were coated with curcumin followed by either resveratrol (Cur-Rsv) or resveratrol nanoparticles (Cur-Rsv-NP). NMC-loaded scaffolds exhibited a biphasic release pattern over 60 days. Solubility and hydrophobic-hydrophilic interactions affected the NMC release profile. Resveratrol showed rapid release as compared to curcumin. The treated scaffold increased the cell viability of human fetal osteoblast (hFOB) by 1.8-fold as compared to the control. It exhibited a 6-fold increase in cytotoxicity toward osteosarcoma (MG-63) cells as compared to the untreated scaffold. NMCs loaded scaffold effectively inhibited Staphylococcus aureus from colonizing over the scaffold. Zinc doping enhanced osteoblast growth and prevented bacterial colony formation. Such design principle provided a direction for developing multi-functionalized calcium phosphate (CaP) scaffolds against bone diseases for orthopedic applications.

Magnetic Bone Tissue Engineering: Reviewing the Effects of Magnetic Stimulation on Bone Regeneration and Angiogenesis

Bone tissue engineering emerged as a solution to treat critical bone defects, aiding in tissue regeneration and implant integration. Mainly, this field is based on the development of scaffolds and coatings that stimulate cells to proliferate and differentiate in order to create a biologically active bone substitute. In terms of materials, several polymeric and ceramic scaffolds have been developed and their properties tailored with the objective to promote bone regeneration. These scaffolds usually provide physical support for cells to adhere, while giving chemical and physical stimuli for cell proliferation and differentiation. Among the different cells that compose the bone tissue, osteoblasts, osteoclasts, stem cells, and endothelial cells are the most relevant in bone remodeling and regeneration, being the most studied in terms of scaffold-cell interactions. Besides the intrinsic properties of bone substitutes, magnetic stimulation has been recently described as an aid in bone regeneration. External magnetic stimulation induced additional physical stimulation in cells, which in combination with different scaffolds, can lead to a faster regeneration. This can be achieved by external magnetic fields alone, or by their combination with magnetic materials such as nanoparticles, biocomposites, and coatings. Thus, this review is designed to summarize the studies on magnetic stimulation for bone regeneration. While providing information regarding the effects of magnetic fields on cells involved in bone tissue, this review discusses the advances made regarding the combination of magnetic fields with magnetic nanoparticles, magnetic scaffolds, and coatings and their subsequent influence on cells to reach optimal bone regeneration. In conclusion, several research works suggest that magnetic fields may play a role in regulating the growth of blood vessels, which are critical for tissue healing and regeneration. While more research is needed to fully understand the relationship between magnetism, bone cells, and angiogenesis, these findings promise to develop new therapies and treatments for various conditions, from bone fractures to osteoporosis.

TiO2/HA and Titanate/HA Double-Layer Coatings on Ti6Al4V Surface and Their Influence on In Vitro Cell Growth and Osteogenic Potential

Hydroxyapatite (HA) layers are appropriate biomaterials for use in the modification of the surface of implants produced inter alia from a Ti6Al4V alloy. The issue that must be solved is to provide implants with appropriate biointegration properties, enabling the permanent link between them and bone tissues, which is not so easy with the HA layer. Our proposition is the use of the intermediate layer ((IL) = TiO₂, and titanate layers) to successfully link the HA coating to a metal substrate (Ti6Al4V). The morphology, structure, and chemical composition of Ti6Al4V/IL/HA systems were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS). We evaluated the apatite-forming ability on the surface of the layer in simulated body fluid. We investigated the effects of the obtained systems on the viability and growth of human MG-63 osteoblast-like cells, mouse L929 fibroblasts, and adipose-derived human mesenchymal stem cells (ADSCs) in vitro, as well as on their osteogenic properties. Based on the obtained results, we can conclude that both investigated systems reflect the physiological environment of bone tissue and create a biocompatible surface supporting cell growth. However, the nanoporous TiO₂ intermediate layer with osteogenesis-supportive activity seems most promising for the practical application of Ti6Al4V/TiO₂/HA as a system of bone tissue regeneration.

Synthesis of Ti6Al4V/SrFHA Composites by Microwave-Assisted Liquid Phase Deposition and Calcination

The feasibility of synthesis of Ti6Al4V/SrFHA (Ca9.37Sr0.63(PO4)6F2) composites via coating strontium and fluorine co-doped HA to Ti6Al4V substrate by microwave-assisted liquid phase deposition and calcination was evaluated, with a focus on the effect of the deposition temperature from 30 °C to 70 °C. The outcomes demonstrate that strontium and fluorine can be successfully doped into HA to form a SrFHA coating with modified micromorphology which is deposited on the alloy. When the deposition temperature was 50 °C, the coating with the largest uniform continuous SrFHA coverage was obtained. After calcination, the adhesion strength and Vickers microhardness of the Ti6Al4V/SrFHA composite increased from 0.68 MPa and 323 HV to 2.41 MPa and 329 HV, respectively, with a decrease in the water contact angle from 10.88° to 7.24°, exhibiting enhancement of both mechanical properties and wettability. Moreover, the composite obtained at the deposition temperature of 50 °C exhibited good bioactivity based on the simulate body fluid (SBF) test. On account of the above features primarily as a result of the combined effect of the co-doping of strontium and fluorine, high crystallinity of SrFHA, large surface roughness, and formation of the titanium oxide transition layer, the Ti6Al4V/SrFHA composite shows great potential in dental implantology.

3D printed hydroxyapatite - Zn2+ functionalized starch composite bone grafts for orthopedic and dental applications

Hydroxyapatite (HA) - polymer composite based 3D printed bone grafts require extensive mechanical and biological property optimization for specific clinical needs. This fuels the need to develop innovative methods of optimization. Using an in-house extrusion-based 3D printer, we show the feasibility of fabricating hydroxyapatite- Zn2+ functionalized starch composites as artificial bone graft substitutes. The experimental procedure for this purpose is fortified with a univariate multi-objective optimization strategy to predict the best composition. The compressive strength of the grafts improves up to ~ 4 folds by parametric optimization and Zn2+ functionalization, without any post-processing. These grafts maintain mechanical integrity and strength during 6 weeks of dissolution study in simulated body fluid (SBF), while the non -functionalized starch-HA grafts fully degrade within a week. The Zn2+ functionalization results in up to ~ 79% antibacterial efficacy against S. aureus. Osteoblast cell viability increases ~ 1.6 folds on these graft surfaces on day 11. Our innovative methods of optimization are expected to reduce the experiment time, cost, and chance of human error in 3D printing. This study redefines the importance of understanding composition and process dependence for making a functionalized 3D printed bone graft for repairing low load-bearing defects such as craniomaxillofacial bone.