Electrodeposited dopamine/strontium-doped hydroxyapatite composite coating on pure zinc for anti-corrosion, antimicrobial and osteogenesis

Highly plastic Zn-0.3Ca alloy for guided bone regeneration membrane: Breaking the trade-off between antibacterial ability and biocompatibility

A common problem for Zn alloys is the trade-off between antibacterial ability and biocompatibility. This paper proposes a strategy to solve this problem by increasing release ratio of Ca2+ ions, which is realized by significant refinement of CaZn13 particles through bottom circulating water-cooled casting (BCWC) and rolling. Compared with conventionally fabricated Zn-0.3Ca alloy, the BCWC-rolled alloy shows higher antibacterial abilities against E. coli and S. aureus, meanwhile much less toxicity to MC3T3-E1 cells. Additionally, plasticity, degradation uniformity, and ability to induce osteogenic differentiation in vitro of the alloy are improved. The elongation up to 49 %, which is the highest among Zn alloys with Ca, and is achieved since the sizes of CaZn13 particles and Zn grains are small and close. As a result, the long-standing problem of low formability of Zn alloys containing Ca has also been solved due to the elimination of large CaZn13 particles. The BCWC-rolled alloy is a promising candidate of making GBR membrane.

Electrospun polycaprolactone-chitosan nanofibers on a zinc mesh as biodegradable guided bone-regeneration membranes with enhanced mechanical, antibacterial, and osteogenic properties for alveolar bone-repair applications

Guided bone-regeneration membrane (GBRM) is commonly used in bone-repair surgery because it blocks fibroblast proliferation and provides spatial support in bone-defect spaces. However, the need for removal surgery and the lack of antibacterial properties of conventional GBRM limit its therapeutic applicability for alveolar bone defects. Here we developed a GBRM for alveolar bone-repair and -regeneration applications through double-sided electrospinning of polycaprolactone and chitosan layers on a Zn mesh surface (denoted DSZM). The DSZM showed a UTS of ∼25.6 MPa, elongation of ∼16.1%, strength-elongation product of ∼0.413 GPa%, and ultrahigh spatial maintenance ability, and the UTS was over 6 times higher than that of commercial Bio-Gide membrane. The DSZM exhibited a corrosion rate of ∼17 µm/y and a Zn ion concentration of ∼0.23 µg/ml after 1 month of immersion in Hanks' solution. The DSZM showed direct and indirect cytocompatibility with exceptional osteogenic differentiation and calcium deposition toward MC3T3-E1 cells. Further, the DSZM showed strongly sustained antibacterial activity against S. aureus and osteogenesis in a rat critical-sized maxillary defect model. Overall, the DSZM fits the requirements for alveolar bone-repair and -regeneration applications as a biodegradable GBRM material due to its spatial support, suitable degradability, cytocompatibility, and antibacterial and osteogenic capabilities. STATEMENT OF SIGNIFICANCE: This work reports the mechanical properties, antibacterial ability and osteogenic properties of electrospun PCL-CS nanofiber on Zn mesh as biodegradable guided bone-regeneration membrane for alveolar bone-repair applications. Our findings demonstrate that the DSZM prepared by double-sided electrospinning of PCL-CS layers on Zn mesh showed a UTS of ∼25.6 MPa, elongation of ∼16.1%, strength-elongation product of ∼0.413 GPa%, and ultrahigh spatial maintenance ability, and the UTS was over 6 times greater than that of commercial Bio-Gide® membrane. The DSZM showed direct and indirect cytocompatibility with exceptional osteogenic differentiation and calcium deposition toward MC3T3-E1 cells. Further, the DSZM showed strongly sustained antibacterial activity against S. aureus and osteogenesis in a rat critical-sized maxillary defect model.

A Critical Review of Biodegradable Zinc Alloys toward Clinical Applications

Biodegradable zinc (Zn) alloys stand out as promising contenders for biomedical applications due to their favorable mechanical properties and appropriate degradation rates, offering the potential to mitigate the risks and expenses associated with secondary surgeries. While current research predominantly centers on the in vitro examination of Zn alloys, notable disparities often emerge between in vivo and in vitro findings. Consequently, conducting in vivo investigations on Zn alloys holds paramount significance in advancing their clinical application. Different element compositions and processing methods decide the mechanical properties and biological performance of Zn alloys, thus affecting their suitability for specific medical applications. This paper presents a comprehensive overview of recent strides in the development of biodegradable Zn alloys, with a focus on key aspects such as mechanical properties, toxicity, animal experiments, biological properties, and molecular mechanisms. By summarizing these advancements, the paper aims to broaden the scope of research directions and enhance the understanding of the clinical applications of biodegradable Zn alloys.

Polydopamine-Based Biomaterials in Orthopedic Therapeutics: Properties, Applications, and Future Perspectives

Polydopamine is a versatile and modifiable polymer, known for its excellent biocompatibility and adhesiveness. It can also be engineered into a variety of nanoparticles and biomaterials for drug delivery, functional modification, making it an excellent choice to enhance the prevention and treatment of orthopedic diseases. Currently, the application of polydopamine biomaterials in orthopedic disease prevention and treatment is in its early stages, despite some initial achievements. This article aims to review these applications to encourage further development of polydopamine for orthopedic therapeutic needs. We detail the properties of polydopamine and its biomaterial types, highlighting its superior performance in functional modification on nanoparticles and materials. Additionally, we also explore the challenges and future prospects in developing optimal polydopamine biomaterials for clinical use in orthopedic disease prevention and treatment.

Presenting dual-functional peptides on implant surface to direct in vitro osteogenesis and in vivo osteointegration

The complex biological process of osseointegration and the bio-inertness of bone implants are the major reasons for the high failure rate of long-term implants, and have also promoted the rapid development of multifunctional implant coatings in recent years. Herein, through the special design of peptides, we use layer-by-layer assembly technology to simultaneously display two peptides with different biological functions on the implant surface to address this issue. A variety of surface characterization techniques (ellipsometry, atomic force microscopy, photoelectron spectroscopy, dissipation-quartz crystal microbalance) were used to study in detail the preparation process of the dual peptide functional coating and the physical and chemical properties, such as the composition, mechanical modulus, stability, and roughness of the coating. Compared with single peptide functional coatings, dual-peptide functionalized coatings had much better performances on antioxidant, cellular adhesion in early stage, proliferation and osteogenic differentiation in long term, as well as in vivo osteogenesis and osseointegration capabilities. These findings will promote the development of multifunctional designs in bone implant coatings, as a coping strategy for the complexity of biological process during osteointegration.

Biomimetic fabrication of sr-silk fibroin co-assembly hydroxyapatite based microspheres with angiogenic and osteogenic properties for bone tissue engineering

Bone defects caused by trauma, tumor resection, or developmental abnormalities are important issues in clinical practice. The vigorous development of tissue engineering technology provides new ideas and directions for regenerating bone defects. Hydroxyapatite (HAp), a bioactive ceramic, is extensively used in bone tissue engineering because of its excellent osteoinductive performance. However, its application is challenged by its single function and conventional environment-unfriendly synthesis methods. In this study, we successfully "green" synthesized sr-silk fibroin co-assembly hydroxyapatite nanoparticles (Sr-SF-HA) using silk fibroin (SF) as a biomineralized template, thus enabling it to have angiogenic activity and achieving the combination of organic and inorganic substances. Then, the rough composite microspheres loaded with Sr-SF-HA (CS/Sr-SF-HA) through electrostatic spraying technology and freeze-drying method were prepared. The CCK-8 test and live/dead cell staining showed excellent biocompatibility of CS/Sr-SF-HA. Alkaline phosphatase (ALP) staining, alizarin red staining (ARS), immunofluorescence, western blotting, and qRT-PCR test showed that CS/Sr-SF-HA activated the expression of related genes and proteins, thus inducing the osteogenic differentiation of rBMSCs. Moreover, tube formation experiments, scratch experiments, immunofluorescence, and qRT-PCR detection indicated that CS/Sr-SF-HA have good angiogenic activity. Furthermore, in vivo studies showed that the CS/Sr-SF-HA possesses excellent biocompatibility, vascular activity, as well as ectopic osteogenic ability in the subcutaneous pocket of rats. This study indicates that the construction of CS/Sr-SF-HA with angiogenic and osteogenic properties has great potential for bone tissue engineering.

External Stimuli-Responsive Strategies for Surface Modification of Orthopedic Implants: Killing Bacteria and Enhancing Osteogenesis

Bacterial infection and insufficient osteogenic activity are the main causes of orthopedic implant failure. Conventional surface modification methods are difficult to meet the requirements for long-term implant placement. In order to better regulate the function of implant surfaces, especially to improve both the antibacterial and osteogenic activity, external stimuli-responsive (ESR) strategies have been employed for the surface modification of orthopedic implants. External stimuli act as "smart switches" to regulate the surface interactions with bacteria and cells. The balance between antibacterial and osteogenic capabilities of implant surfaces can be achieved through these specific ESR manifestations, including temperature changes, reactive oxygen species production, controlled release of bioactive molecules, controlled release of functional ions, etc. This Review summarizes the recent progress on different ESR strategies (based on light, ultrasound, electric, and magnetic fields) that can effectively balance antibacterial performance and osteogenic capability of orthopedic implants. Furthermore, the current limitations and challenges of ESR strategies for surface modification of orthopedic implants as well as future development direction are also discussed.

Designing bioinspired multifunctional nanoplatforms to support wound healing and skin regeneration: Mg-hydroxyapatite meets melanins

Melanin is a multifunctional biological pigment that recently emerged as endowed with anti-inflammatory, antioxidant, and antimicrobial properties and with high potentialities in skin protection and regenerative medicine. Here, a biomimetic magnesium-doped nano-hydroxyapatite (MgHA) was synthesized and decorated with melanin molecules starting from two different monomeric precursors, i.e. 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and dopamine (DA), demonstrating to be able to polymerize on the surface of MgHA nanostructures, thus leading to a melanin coating. This functionalization was realized by a simple and green preparation method requiring mild conditions in an aqueous medium and room temperature. Complementary spectroscopy and electron imaging analyses were carried out to define the effective formation of a stable coating, the percentage of the organic compounds, and the structural properties of resulting melanin-coated nanostructures, which showed good antioxidant activity. The in vitro interaction with a cell model, i.e. mouse fibroblasts, was investigated. The excellent biocompatibility of all bioinspired nanostructures was confirmed from a suitable cell proliferation. Finally, the enhanced biological performances of the nanostructures coated with melanin from DHICA were confirmed by scratch assays. Jointly our findings indicated that low crystalline MgHA and melanin pigments can be efficiently combined, and the resulting nanostructures are promising candidates as multifunctional platforms for a more efficient approach for skin regeneration and protection.

In vitro and in vivo studies on biodegradable Zn porous scaffolds with a drug-loaded coating for the treatment of infected bone defect

Additively manufactured biodegradable zinc (Zn) scaffolds have great potential to repair infected bone defects due to their osteogenic and antibacterial properties. However, the enhancement of antibacterial properties depends on a high concentration of dissolved Zn2+, which in return deteriorates osteogenic activity. In this study, a vancomycin (Van)-loaded polydopamine (PDA) coating was prepared on pure Zn porous scaffolds to solve the above dilemma. Compared with pure Zn scaffolds according to comprehensive in vitro tests, the PDA coating resulted in a slow degradation and inhibited the excessive release of Zn2+ at the early stage, thus improving cytocompatibility and osteogenic activity. Meanwhile, the addition of Van drug substantially suppressed the attachment and proliferation of S. aureus and E. coli bacterial. Furthermore, in vivo implantation confirmed the simultaneously improved osteogenic and antibacterial functions by using the pure Zn scaffolds with Van-loaded PDA coating. Therefore, it is promising to employ biodegradable Zn porous scaffolds with the proposed drug-loaded coating for the treatment of infected bone defects.

Dealloyed nano-porous TiCu coatings with controlled copper release for cardiovascular devices

TiCu coatings with controlled copper release and nano-porous structures were fabricated as biocompatible, blood-contacting interfaces through a two-step process. Initially, coatings with 58 % Cu were created using HiPIMS/DC magnetron co-sputtering, followed by immersion in a dilute HF solution for varying durations to achieve dealloying. The presence of Ti elements in the as-deposited TiCu coatings facilitated their dissolution upon exposure to the dilute HF solution, resulting in the formation of nanopores and increased nano-roughness. Dealloying treatment time correlated with higher Cu/(Ti + Cu) values, nanopore size, and nano-roughness in the dealloyed samples. The dealloyed TiCu coatings with 87 % Cu exhibited a controlled release of copper ions and displayed nanopores (approximately 80 nm in length and 31.0 nm in width) and nano-roughness (Ra roughness: 82 nm). These coatings demonstrated inhibited platelet adhesion and suppressed smooth muscle cell behavior, while supporting favorable endothelial cell viability and proliferation, attributed to the controlled release of copper ions and the extent of nanostructures. In contrast, the as-deposited TiCu coatings with 85 % Cu showed high copper ion release, leading to decreased viability and proliferation of endothelial cells and smooth muscle cells, as well as suppressed platelet adhesion. The TiCu coatings met medical safety standards, exhibiting hemolysis rates of <5 %. The technology presented here paves the way for the simple, controllable, and cost-effective fabrication of TiCu coatings, opening new possibilities for surface modification of cardiovascular devices such as vascular stents and inferior vena cava filters.

Curcumin and Vitamin C dual release from Hydroxyapatite coated Ti6Al4V discs enhances in vitro biological properties

Titanium alloys are widely used as implant materials due to their biocompatibility and superior mechanical properties for high-load-bearing applications. However, one of the major challenges is their inferior bioactivity and osseoconductivity. Hydroxyapatite is widely used as an alternative material for bone implants due to its compositional similarity to natural bone. In this study, hydroxyapatite is coated on Ti6Al4V discs to enhance its bioactivity. The coated discs are drop-casted with curcumin in the lower layer and vitamin C in the upper layer. This study aims to evaluate the effects of this dual drug delivery system on osteoblast cell proliferation, inhibition of osteoclastogenesis, chemo-preventive and infection control properties. The coating strength obtained is 22 ± 2 MPa. The release from the dual delivery system shows a 1.5-fold increase in osteoblast cell viability, a 1.5-fold reduction in osteoclast cell differentiation, a 2-fold decrease in osteosarcoma growth. The release of curcumin demonstrates a 94% antibacterial efficacy, while the release of vitamin C exhibits an efficacy of 98.6% aganist Staphylococcus aureus. This multifunctional system can be used as a potential implant for load-bearing applications.

Zinc-based biomaterials for bone repair and regeneration: mechanism and applications

Zinc (Zn) is one of the most important trace elements in the human body and plays a key role in various physiological processes, especially in bone metabolism. Zn-containing materials have been reported to enhance bone repair through promoting cell proliferation, osteogenic activity, angiogenesis, and inhibiting osteoclast differentiation. Therefore, Zn-based biomaterials are potential substitutes for traditional bone grafts. In this review, the specific mechanisms of bone formation promotion by Zn-based biomaterials were discussed, and recent developments in their application in bone tissue engineering were summarized. Moreover, the challenges and perspectives of Zn-based biomaterials were concluded, revealing their attractive potential and development directions in the future.

Hydroxyapatite coated titanium with curcumin and epigallocatechin gallate for orthopedic and dental applications

Titanium and its alloy are clinically used as an implant material for load-bearing applications to treat bone defects. However, the lack of biological interaction between bone tissue and implant and the risk of infection are still critical challenges in clinical orthopedics. In the current work, we have developed a novel approach by first 1) modifying the implant surface using hydroxyapatite (HA) coating to enhance bioactivity and 2) integrating curcumin and epigallocatechin gallate (EGCG) in the coating that would induce chemopreventive and osteogenic potential and impart antibacterial properties to the implant. The study shows that curcumin and EGCG exhibit controlled and sustained release profiles in acidic and physiological environments. Curcumin and EGCG also show in vitro cytotoxicity toward osteosarcoma cells after 11 days, and the dual system shows a ~94 % reduction in bacterial growth, indicating their in vitro chemopreventive potential and antibacterial efficacy. The release of both curcumin and EGCG was found to be compatible with osteoblast cells and further promotes their growth. It shows a 3-fold enhancement in cellular viability in the dual drug-loaded implant compared to the untreated samples. These findings suggest that multifunctional HA-coated Ti6Al4V implants integrated with curcumin and EGCG could be a promising strategy for osteosarcoma inhibition and osteoblast cell growth while preventing infection.

Metal Ion-Doped Hydroxyapatite-Based Materials for Bone Defect Restoration

Hydroxyapatite (HA)-based materials are widely used in the bone defect restoration field due to their stable physical properties, good biocompatibility, and bone induction potential. To further improve their performance with extra functions such as antibacterial activity, various kinds of metal ion-doped HA-based materials have been proposed and synthesized. This paper offered a comprehensive review of metal ion-doped HA-based materials for bone defect restoration based on the introduction of the physicochemical characteristics of HA followed by the synthesis methods, properties, and applications of different kinds of metal ion (Ag+, Zn2+, Mg2+, Sr2+, Sm3+, and Ce3+)-doped HA-based materials. In addition, the underlying challenges for bone defect restoration using these materials and potential solutions were discussed.

Host bone microstructure for enhanced resistance to bacterial infections

Postoperative bacterial infection is a serious complication of orthopedic surgery. Not only infections that develop in the first few weeks after surgery but also late infections that develop years after surgery are serious problems. However, the relationship between host bone and infection activation has not yet been explored. Here, we report a novel association between host bone collagen/apatite microstructure and bacterial infection. The bone-mimetic-oriented micro-organized matrix structure was obtained by prolonged controlled cell alignment using a grooved-structured biomedical titanium alloy. Surprisingly, we have discovered that highly aligned osteoblasts have a potent inhibitory effect on Escherichia coli adhesion. Additionally, the oriented collagen/apatite micro-organization of the bone matrix showed excellent antibacterial resistance against Escherichia coli. The proposed mechanism for realizing the antimicrobial activity of the micro-organized bone matrix is by the controlled secretion of the antimicrobial peptides, including β-defensin 2 and β-defensin 3, from the highly aligned osteoblasts. Our findings contribute to the development of anti-infective strategies for orthopedic surgeries. The recovery of the intrinsically ordered bone matrix organization provides superior antibacterial resistance after surgery.

Corrosion-tailoring, osteogenic, anti-inflammatory, and antibacterial aspirin-loaded organometallic hydrogel composite coating on biodegradable Zn for orthopedic applications

Zn and its alloys are receiving increasing interest for biodegradable orthopedic implant applications owing to their moderate corrosion rate and the potential functionality of Zn2+. However, their non-uniform corrosion behavior and insufficient osteogenic, anti-inflammatory, and antibacterial properties do not meet the comprehensive requirements of orthopedic implants in clinical use. Herein, an aspirin (an acetylsalicylic acid, ASA, 10, 50, 100, and 500 mg/L)-loaded carboxymethyl chitosan (CMC)/gelatin (Gel)-Zn2+ organometallic hydrogel composite coating (CMC/Gel&Zn2+/ASA) was fabricated on a Zn surface via an alternating dip-coating method, aiming to obtain a material with these comprehensive properties improved. The organometallic hydrogel composite coatings, ca. 12-16 μm in thickness, showed compact, homogeneous, and micro-bulge structured surface morphology. The coatings protected well the Zn substrate from pitting/localized corrosion and contained the release of the bioactive components, Zn2+ and ASA, in a sustained and stable manner in long-term in vitro immersions in Hank's solution. The coated Zn showed greater ability to promote proliferation and osteogenic differentiation for MC3T3-E1 osteoblasts, and better anti-inflammatory capacity when compared with uncoated Zn. Additionally, this coating displayed excellent antibacterial activity against both Escherichia coli (>99 % antibacterial rate) and Staphylococcus aureus (>98 % antibacterial rate). Such appealing properties can be attributed to the compositional nature of the coating, namely the sustained release of Zn2+ and ASA, as well as the surface physiochemical properties because of its unique microstructure. This organometallic hydrogel composite coating can be considered a promising option for the surface modification of biodegradable Zn-based orthopedic implants among others.

Evolution from Bioinert to Bioresorbable: In Vivo Comparative Study of Additively Manufactured Metal Bone Scaffolds

Additively manufactured scaffolds offer significant potential for treating bone defects, owing to their porous, customizable architecture and functionalization capabilities. Although various biomaterials have been investigated, metals - the most successful orthopedic material - have yet to yield satisfactory results. Conventional bio-inert metals, such as titanium (Ti) and its alloys, are widely used for fixation devices and reconstructive implants, but their non-bioresorbable nature and the mechanical property mismatch with human bones limit their application as porous scaffolds for bone regeneration. Advancements in additive manufacturing have facilitated the use of bioresorbable metals, including magnesium (Mg), zinc (Zn), and their alloys, as porous scaffolds via Laser Powder Bed Fusion (L-PBF) technology. This in vivo study presents a comprehensive, side-by-side comparative analysis of the interactions between bone regeneration and additively manufactured bio-inert/bioresorbable metal scaffolds, as well as their therapeutic outcomes. The research offers an in-depth understanding of the metal scaffold-assisted bone healing process, illustrating that Mg and Zn scaffolds contribute to the bone healing process in distinct ways, but ultimately deliver superior therapeutic outcomes compared to Ti scaffolds. These findings suggest that bioresorbable metal scaffolds hold considerable promise for the clinical treatment of bone defects in the near future.

Mesoporous TiO2 Coatings Regulate ZnO Nanoparticle Loading and Zn2+ Release on Titanium Dental Implants for Sustained Osteogenic and Antibacterial Activity

Two major issues are currently hindering the clinical practice of titanium dental implants for the lack of biological activities: immediate/early loading risks and peri-implantitis. To solve these issues, it is urgent to develop multifunctional implants modified with effective osteogenic and antibacterial properties. Zinc oxide nanoparticles (ZnO NPs) possess superior antibacterial activity; however, they can rapidly release Zn²⁺, causing cytotoxicity. In this study, a potential dental implant modification was creatively developed as ZnO nanoparticle-loaded mesoporous TiO₂ coatings (nZnO/MTC-Ti) via the evaporation-induced self-assembly method (EISA) and one-step spin coating. The mesoporous TiO₂ coatings (MTCs) regulated the synthesis and loading of ZnO NPs inside the nanosized pores. The synergistic effects of MTC and ZnO NPs on nZnO/MTC-Ti not only controlled the long-term steady-state release of Zn²⁺ but also optimized the charge distribution on the surface. Therefore, the cytotoxicity of ZnO NPs was resolved without triggering excessive reactive oxygen species (ROS). The increased extracellular Zn²⁺ further promoted a favorable intracellular zinc ion microenvironment through the modulation of zinc transporters (ZIP1 and ZnT1). Owing to that, the adhesion, proliferation, and osteogenic activity of bone mesenchymal stem cells (BMSCs) were improved. Additionally, nZnO/MTC-Ti inhibited the proliferation of oral pathogens (Pg and Aa) by inducing bacterial ROS production. For in vivo experiments, different implants were implanted into the alveolar fossa of Sprague-Dawley rats immediately after tooth extraction. The nZnO/MTC-Ti implants were found to possess a higher capability for enhancing bone regeneration, antibiosis, and osseointegration in vivo. These findings suggested the outstanding performance of nZnO/MTC-Ti implants in accelerating osseointegration and inhibiting bacterial infection, indicating a huge potential for solving immediate/early loading risks and peri-implantitis of dental implants.

Shifting focus from bacteria to host neutrophil extracellular traps of biodegradable pure Zn to combat implant centered infection

The widespread use of orthopedic implants to support or replace bones is increasingly threatened by the risk of incurable bacterial infections, impenetrable microbial biofilms, and irreversible antibiotic resistance. In the past, the development of anti-infective biomaterials focused solely on direct antibacterial properties while ignoring the host's immune response. Inspired by the clearance of infection by the innate neutrophil response and participation in anti-infectious immunity of Zn ions, we report an innovative neutrophil extracellular traps (NETs) strategy, induced by biodegradable pure Zn, which achieved therapeutic efficacy toward biomaterial-related infections. Our in vitro and in vivo data showed that pure Zn was favorable for NETs formation by promoting the release of DNA fibers and granule proteins in a reactive oxygen species (ROS)-dependent manner, thereby retraining and degrading bacteria with an efficiency of up to 99.5%. Transcriptome analysis revealed that cytoskeletal rearrangement and toll-like receptor (TLR) signaling pathway were also involved in Zn-induced NETs formation. Furthermore, the in vivo results of a Staphylococcus aureus (S. aureus)-infected rat model verified that pure Zn potentiated the bactericidal capability of neutrophils around implants, and promoted osseointegration in S. aureus-infected rat femurs. This antibacterial immunity concept lays a foundation for the development of other antibacterial biomaterials and holds great promise for treating orthopedic infections.

Boosting bone cell growth using nanofibrous carboxymethylated cellulose and chitosan on titanium dioxide nanotube array with dual surface charges as a novel multifunctional bioimplant surface

One of the most vital aspects of the orthopedic implant field has been the development of multifunctional coatings that improve bone-implant contact while simultaneously preventing bacterial infection. The present study investigates the fabrication and characterization of multifunctional polysaccharides, including carboxymethyl cellulose (CMCn) and carboxymethyl chitosan nanofibers (CMCHn), as a novel implant coating on titania nanotube arrays (T). Field emission scanning electron microscopy (FESEM) images revealed a nanofibrous morphology with a narrow diameter for CMCn and CMCHn, similar to extracellular matrix nanostructures. Compared to the T surface, the roughness of CMCn and CMCHn samples increased by over 250 %. An improved cell proliferation rate was observed on CMCHn nanofibers with a positively charged surface caused by the amino groups. Furthermore, in an antibacterial experiment, CMCn and CMCHn inhibited bacterial colony formation by 80 % and 73 %, respectively. According to the results, constructed modified CMCn and CMCHn increased osteoblast cell survival while inhibiting bacterial biofilm formation owing to their surface charge and bioinspired physicochemical properties.

Fabrication and properties of multi-functional polydopamine coated Cu/F-codoped hydroxyapatite hollow microspheres as drug carriers

Due to its excellent bone conductivity and drug adsorption as well as pH-responsive drug release property, hydroxyapatite (HAp) is widely used as a drug carrier in bone repair field. Here, we report for the first time a novel multi-functional polydopamine (PDA) coated Cu/F-codoped HAp (Cu/F-HAp-PDA) hollow microspheres. Both Cu²⁺ and F^- were successfully doped into the lattice of HAp and uniformly distributed in the shell of hollow microspheres through a one-step hydrothermal synthesis. Then PDA was coated homogeneously on the outer layer of Cu/F-HAp hollow microspheres. Both Cu/F-HAp and Cu/F-HAp-PDA samples displayed high drug loading efficiency and pH responsive drug release behavior. Moreover, the obtained Cu/F-HAp-PDA hollow microspheres exhibited excellent photothermal conversion efficiency and photothermal stability. The molecular dynamics simulations showed that PDA and HAp can form mutual binding mainly through Ca-O bonding, while doxorubicin (DOX) is mainly bound to PDA molecules through hydrogen bonding and π-π stacking interaction.

Graphene/hydroxyapatite coating deposit on titanium alloys for implant application

Titanium (Ti) implants are widely used in medicine. Meanwhile, surface modification of Ti can strengthen the osseointegration of implants. In this study, we modified Ti implant surfaces, which was coated with GO, HA, HA-2wt%GO and HA-5wt%GO via electrophoresis deposition, to investigate their mechanisms and biological activity. Uncoated Ti was used as the control. Further, we examined the biological behavior and osteogenic performance of mouse bone marrow mesenchymal stem cells (BMSCs) cultured on coatings in vitro. We found that the HA-GO nanocomposite coating improved the roughness and hydrophilicity of the Ti surface. Compared with the uncoated Ti or Ti modified by HA or GO alone, cell adhesion and diffusion were enhanced on HA-GO-modified Ti surfaces. In addition, the proliferation and osteogenic differentiation of BMSCs in vitro were significantly improved on HA-GO-modified surfaces, whereas osteogenesis-related gene expression and alkaline phosphatase activity were slightly enhanced. Furthermore, we noted that bone regeneration was improved in the HA-2wt%GO group in vivo. Thus, the HA-2wt%GO nanocomposite coating might have potential applications in the field of dental implants.

Mussel-Inspired Polydopamine-Based Multilayered Coatings for Enhanced Bone Formation

Repairing bone defects remains a challenge in clinical practice and the application of artificial scaffolds can enhance local bone formation, but the function of unmodified scaffolds is limited. Considering different application scenarios, the scaffolds should be multifunctionalized to meet specific demands. Inspired by the superior adhesive property of mussels, polydopamine (PDA) has attracted extensive attention due to its universal capacity to assemble on all biomaterials and promote further adsorption of multiple external components to form PDA-based multilayered coatings with multifunctional property, which can induce synergistic enhancement of new bone formation, such as immunomodulation, angiogenesis, antibiosis and antitumor property. This review will summarize mussel-inspired PDA-based multilayered coatings for enhanced bone formation, including formation mechanism and biofunction of PDA coating, as well as different functional components. The synergistic enhancement of multiple functions for better bone formation will also be discussed. This review will inspire the design and fabrication of PDA-based multilayered coatings for different application scenarios and promote deeper understanding of their effect on bone formation, but more efforts should be made to achieve clinical translation. On this basis, we present a critical conclusion, and forecast the prospects of PDA-based multilayered coatings for bone regeneration.

Anisotropic expansion effect of Sr doping on the crystal structure of hydroxyapatite

The anisotropic expansion effect of Sr on the HA crystal structure is proposed where the relative expansion rate in the c-axis direction is about 2.22 times that in the a-axis direction.

Anti-tuberculosis drug delivery for tuberculous bone defects

INTRODUCTION

Traditional therapy methods for treating tuberculous bone defects have several limitations. Furthermore, systemic toxicity and disease recurrence in tuberculosis (TB) have not been effectively addressed.

AREAS COVERED

This review is based on references from September 1998 to September 2021 and summarizes the classification and drug-loading methods of anti-TB drugs. The application of different types of biological scaffolds loaded with anti-TB drugs as a novel drug delivery strategy for tuberculous bone defects has been deeply analyzed. Furthermore, the limitations of the existing studies are summarized.

EXPERT OPINION

Loading anti-TB drugs into the scaffold through various drug-loading techniques can effectively improve the efficiency of anti-TB treatment and provide an effective means of treating tuberculous bone defects. This methodology also has good application prospects and provides directions for future research.