Preparation and bioactive properties of chitosan and casein phosphopeptides composite coatings for orthopedic implants

Biological MWCNT/chitosan composite coating with outstanding anti-corrosion property for implants

Biocompatible coatings that can protect metal implants have great potential in tissue engineering. In this work, MWCNT/chitosan composite coatings with hydrophobic-hydrophilic asymmetric wettability were facilely prepared by one-step in situ electrodeposition. The resultant composite coating exhibits excellent thermal stability and mechanical strength (0.76 MPa), benefiting from the compact internal structure. The thickness of the coating can be controlled precisely by the amounts of transferred charges. The MWCNT/chitosan composite coating demonstrates a lower corrosion rate due to its hydrophobicity and compact internal structure. Compared with exposed 316 L stainless steel, its corrosion rate is reduced by two orders of magnitude from 3.004 × 10^-1 mm/yr to 5.361 × 10^-3 mm/yr. The content of iron released from 316 L stainless steel into the simulated body fluid drops to 0.1 mg/L under the protection of the composite coating. In addition, the composite coating enables efficient calcium enrichment from simulated body fluids and promotes the formation of bioapatite layers on the coating surface. This study contributes to furthering the practical application of chitosan-based coatings in implant anticorrosion.

Biocompatibility and osteoinductive ability of casein phosphopeptide modified polyetheretherketone

Polyetheretherketone (PEEK) is a potential implant material for dental application due to its excellent mechanical properties. However, its biological inertness and poor osteoinductive ability limited its clinical application. Based on a lay-by-layer self-assembly technique, here we incorporated casein phosphopeptide (CPP) onto PEEK surface by a simple two-step strategy to address the poor osteoinductive ability of PEEK implants. In this study, the PEEK specimens were positively charged by 3-ammoniumpropyltriethoxysilane (APTES) modification, then the CPP was adsorbed onto the positively charged PEEK surface electrostatically to obtain CPP-modified PEEK (PEEK-CPP) specimens. The surface characterization, layer degradation, biocompatibility and osteoinductive ability of the PEEK-CPP specimens were studied in vitro. After CPP modification, the PEEK-CPP specimens had a porous and hydrophilic surface and presented enhanced cell adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells. These findings indicated that CPP modification could significantly improve the biocompatibility and osteoinductive ability of PEEK-CPP implants in vitro. In a word, CPP modification is a promising strategy for the PEEK implants to achieve osseointegration.

Rationally designed bioactive milk-derived protein scaffolds enhanced new bone formation

Recently, a number of studies reported that casein was composed of various multifunctional bioactive peptides such as casein phosphopeptide and β-casochemotide-1 that bind calcium ions and induce macrophage chemotaxis, which is crucial for bone homeostasis and bone fracture repair by cytokines secreted in the process. We hypothesized that the effects of the multifunctional biopeptides in casein would contribute to improving bone regeneration. Thus, we designed a tissue engineering platform that consisted of casein and polyvinyl alcohol, which was a physical-crosslinked scaffold (milk-derived protein; MDP), via simple freeze-thaw cycles and performed surface modification using 3,4-dihydroxy-l-phenylalanine (DOPA), a mussel adhesive protein, for immobilizing adhesive proteins and cytokines for recruiting cells in vivo (MDP-DOPA). Both the MDP and MDP-DOPA groups proved indirectly contribution of macrophages migration as RAW 264.7 cells were highly migrated toward materials by contained bioactive peptides. We implanted MDP and MDP-DOPA in a mouse calvarial defect orthotopic model and evaluated whether MDP-DOPA showed much faster mineral deposition and higher bone density than that of the no-treatment and MDP groups. The MDP-DOPA group showed the accumulation of host M2 macrophages and mesenchymal stem cells (MSCs) around the scaffold, whereas MDP presented mostly M1 macrophages in the early stage.

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Bioactive peptide-containing scaffold was fabricated via simple freeze-thaw cycles, and subsequently, the surface was modified with adhesive protein.

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We confirmed that the multifunctional biopeptides regulated the migration of macrophages and enhanced osteogenic differentiation.

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The bioactive peptide-containing scaffold showed much faster and higher mineral deposition in vivo animal studies compared to the other groups.

Dual-Functional Polyetheretherketone Surface with an Enhanced Osteogenic Capability and an Antibacterial Adhesion Property In Vitro by Chitosan Modification

A chitosan layer was covalently bonded to a polyetheretherketone (PEEK) surface using a simple facile self-assembly method to address inadequate biological activity and infection around the implant. The surface characterization, layer degradation, biological activity, and antibacterial adhesion properties of chitosan-modified PEEK (PEEK-CS) were studied. Through chitosan grafting, the surface morphology changed, the surface roughness increased, and the contact angle decreased significantly. PEEK-CS boosted cell adhesion, proliferation, increased alkaline phosphate activity, extracellular matrix mineralization, and expression of osteogenic genes. PEEK-CS demonstrated less adhesion to Porphyromonas gingivalis as well as less bacterial adhesion to P. gingivalis and Streptococcus mutans. According to our findings, chitosan modification significantly improved the osteogenic ability and antibacterial adhesion of PEEK in vitro.

Casein-Coated Molybdenum Disulfide Nanosheets Augment the Bioactivity of Alginate Microspheres for Orthopedic Applications

Defects and disorders of the bone due to disease, trauma, or abnormalities substantially affect a person's life quality. Research in bone tissue engineering is motivated to address these clinical needs. The present study demonstrates casein-mediated liquid exfoliation of molybdenum disulfide (MoS₂) and its coupling with alginate to create microspheres to engineer bone graft substitutes. Casein-exfoliated nano-MoS₂ was chemically characterized using different analytical techniques. The UV-visible spectrum of nano-MoS₂-2 displayed strong absorption peaks at 610 and 668 nm. In addition, the XPS spectra confirmed the presence of the molybdenum (Mo, 3d), sulfur (S, 2p), carbon (C, 1s), oxygen (O, 1s), and nitrogen (N, 1s) elements. The exfoliated MoS₂ nanosheets were biocompatible with the MG-63, MC3T3-E1, and C2C12 cells at 250 μg/mL concentration. Further, microspheres were created using alginate, and they were characterized physiochemically and biologically. Stereomicroscopic images showed that the microspheres were spherical with an average diameter of 1 ± 0.2 mm. The dispersion of MoS₂ in the alginate matrix was uniform. The alginate-MoS₂ microspheres promoted apatite formation in the SBF (simulated body fluid) solution. Moreover, the alginate-MoS₂ was biocompatible with MG-63 cells and promoted cell proliferation. Higher alkaline phosphatase activity and mineralization were observed on the alginate-MoS₂ with the MG-63 cells. Hence, the developed alginate-MoS₂ microsphere could be a potential candidate for a bone graft substitute.

The Influence of Casein Coatings on the Corrosion Behavior of Mg-Based Alloys

This article discusses the influence of conversion casein coatings with a thickness of about 20 µm on the structure and the corrosion behavior of two magnesium alloys: MgCa2Zn1 and MgCa2Zn1Gd3. Casein is a protein that, along with whey protein, is a part of milk. Casein coatings are appropriate for bone growth because they contain high amounts of calcium and phosphorus. In this work, casein coatings and casein-free coatings were applied on Mg-based alloys using the conversion process. The structure and topography observations were presented. The corrosion behavior was determined by electrochemical and immersion tests, and electrochemical impedance spectroscopy (EIS) in chloride-rich Ringer solution. The obtained results show that conversion casein coatings effectively protect Mg-based alloys against corrosion. This was confirmed by higher corrosion potentials (E_corr), polarization resistances (R_p) derived from Tafel’s and EIS analysis, as well as low hydrogen release. The volume of hydrogen released after 216 h of immersion for casein coatings applied to MgCa2Zn1 and MgCa2Zn1Gd3 alloys was 19.25 and 12.42 mL/cm², respectively. The improvement in corrosion resistance of casein coatings was more significant for Mg alloy dopped with gadolinium. The lower corrosion rate of casein conversion coatings is explained by the synergistic effect of the addition of Gd in the Mg-based alloy and the formation of dense, tight conversion casein coatings on the surface of this alloy.

Point-of-care antimicrobial coating protects orthopaedic implants from bacterial challenge

Implant related infections are the most common cause of joint arthroplasty failure, requiring revision surgeries and a new implant, resulting in a cost of $8.6 billion annually. To address this problem, we created a class of coating technology that is applied in the operating room, in a procedure that takes less than 10 min, and can incorporate any desired antibiotic. Our coating technology uses an in situ coupling reaction of branched poly(ethylene glycol) and poly(allyl mercaptan) (PEG-PAM) polymers to generate an amphiphilic polymeric coating. We show in vivo efficacy in preventing implant infection in both post-arthroplasty infection and post-spinal surgery infection mouse models. Our technology displays efficacy with or without systemic antibiotics, the standard of care. Our coating technology is applied in a clinically relevant time frame, does not require modification of implant manufacturing process, and does not change the implant shelf life.

The effect of coating chitosan on Porphyromonas gingivalis biofilm formation in the surface of orthodontic mini-implant

Infection is the main problem for the failure of orthodontic mini-implant. Modern prevention of infection is now focused on local antibacterial coatings on implant devices. Chitosan is biocompatible and has antibacterial properties. Azithromycin is a synthetic antibiotic with immunomodulatory properties in which it has an advantage over the rest of antibiotics. This study aimed to evaluate the effect coating chitosan on the orthodontic mini-implant in Porphyromonas gingivalis biofilm formation. This is an experimental study using 25 orthodontic mini-implants. Five samples were coated with chitosan, 5 samples were coated with chitosan-azithromycin, 5 samples were coated with azithromycin, 5 samples were uncoated, and 5 samples were uncoated and were not exposed to P. gingivalis. P. gingivalis biofilms on the surface of the orthodontic mini-implant were observed after 24 h of incubation. P. gingivalis biofilm mass inhibition was highest in the azithromycin-treated group, followed by chitosan + azithromycin and chitosan only. The one-way ANOVA statistic test and post hoc Bonferroni statistic test of P. gingivalis biofilm mass show a significant difference between and within groups of experiments (P < 0.05). The Pearson correlation test with a value of R = +0.88, indicated that the bacterial viability count and the biofilm mass have a strong positive correlation. In conclusion, orthodontic mini-implant coated with chitosan, chitosan with azithromycin, or azithromycin only effectively suppressed P. gingivalis biofilm formation.

Surface functionalization of chitosan as a coating material for orthopaedic applications: A comprehensive review

Metallic implants have dominated the biomedical implant industries for the past century for load-bearing applications, while the polymeric implants have shown great promise for tissue engineering applications. The surface properties of such implants are critical as the interaction of implant surfaces, and the body tissues may lead to unfavourable reactions. Desired implant properties are biocompatibility, corrosion resistance, and antibacterial activity. A polymer coating is an efficient and economical way to produce such surfaces. A lot of research has been carried out on chitosan (CS)-modified metallic and polymer scaffolds in the last decade. Different methods such as electrophoretic deposition, sol-gel methods, dip coating and spin coating, electrospinning, etc. have been utilized to produce CS coatings. However, a systematic review of chitosan coatings on scaffolds focussing on widely employed techniques is lacking. This review surveys literature concerning the current status of orthopaedic applications of CS for the purpose of coatings. In this review, the various preparation methods of coating, and the role of the surface functionalities in determining the efficiency of coatings are discussed. Effect of nanoparticle additions on the polymeric interfaces and in regulating the properties of surface coatings are also investigated in detail.

Effect of RGD content in poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-alt-maleic acid) hydrogels on the expansion of ovarian cancer stem-like cells

The extracellular matrix (ECM) affects cell behaviors, such as survival, proliferation, motility, invasion, and differentiation. The arginine-glycine-aspartic acid (RGD) sequence is present in several ECM proteins, such as fibronectin, collagen type I, fibrinogen, laminin, vitronectin, and osteopontin. It is very critical to develop ECM-like substrates with well-controlled features for the investigation of influence of RGD on the behavior of tumor cells. In this study, poly(ethylene glycol) (PEG)-crosslinked poly(methyl vinyl ether-alt-maleic acid) (P(MVE-alt-MA)) hydrogels (PEMM) with different RGD contents were synthesized, fully characterized, and established as in vitro culture platforms to investigate the effects of RGD content on cancer stem cell (CSC) enrichment. The morphology, proliferation, and viability of SK-OV-3 ovarian cancer cells cultured on hydrogels with different RGD contents, the expression of CSC markers and malignant signaling pathway-related genes, and drug resistance were systematically evaluated. The cell aggregates formed on the hydrogel surface with a lower RGD content acquired certain CSC-like properties, thus drug resistance was enhanced. In contrast, the drug sensitivity of cells on the higher RGD content surface increased because of less CSC-like properties. However, the presence of RGD in the stiff hydrogels (PEMM2) had less effect on the stemness expression than did its presence in the soft hydrogels (PEMM1). The results suggest that RGD content and matrix stiffness can lead to synergetic effects on the expression of cancer cell stemness and the epithelial-mesenchymal transition (EMT), interleukin-6 (IL-6), and Wnt pathways.

A Review of In-Situ Grown Nanocomposite Coatings for Titanium Alloy Implants

Composite coatings are commonly applied to medical metal implants in order to improve biocompatibility and/or bioactivity. In this context, two types of titanium-based composite coatings have been reviewed as biocompatible and anti-bacterial coatings. The different composites can be synthesised on the surface of titanium using various methods, which have their own advantages and disadvantages. Moving with the smart and nanotechnology, multifunctional nanocomposite coatings have been introduced on implants and scaffolds for tissue engineering with the aim of providing more than one properties when required. In this context, titanium dioxide (TiO2) nanotubes have been shown to enhance the properties of titanium-based implants as part of nanocomposite coatings.

Synthesis and characterization of L-tyrosine-conjugated quaternary ammonium salt chitosan and their cytocompatibility as a potential tissue engineering scaffold

A novel amino acid-modified biomacromolecule was designed and synthesized as the quaternary ammonium salt chitosan grafted-tyrosine (CA-g-Tyr) suitable for biomedical applications. L-tyrosine was grafted onto the quaternary ammonium salt chitosan (CA) by N-(3-dimethylaminopropy)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The chemical structure of CA-g-Tyr was confirmed by Fourier transform infrared (FTIR) spectroscopy and ¹³C-NMR. The change in the crystalline structure after the graft was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The surface wettability and moisturizing performance of the CA-g-Tyr were also characterized. The CA-g-Tyr film possessed good hydrophilicity, and the mechanical tensile experiments showed that the introduction of tyrosine gave CA mechanical properties more suitable for blood vessel. Cell experiments showed that the endothelial cells can adhere and proliferate better on the surface of a CA-g-Tyr film than CA. The results confirm the favorable properties and biocompatibility of CA-g-Tyr with potential applications as scaffolds for tissue engineering.

Polydopamine-Assisted Immobilization of Chitosan Brushes on a Textured CoCrMo Alloy to Improve its Tribology and Biocompatibility

Due to their bioinert and reliable tribological performance, cobalt chromium molybdenum (CoCrMo) alloys have been widely used for articular joint implant applications. However, friction and wear issues are still the main reasons for the failure of implants. As a result, the improvement of the tribological properties and biocompatibility of these alloys is still needed. Thus, surface modification is of great interest for implant manufacturers and for clinical applications. In this study, a strategy combining laser surface texturing and chitosan grafting (mussel inspired) was used to improve the tribological and biocompatible behaviors of CoCrMo. The microstructure and chemical composition were investigated by atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The tribological properties were discussed to determine their synergistic effects. To evaluate their biocompatibility, osteoblast cells were cocultured with the modified surface. The results show that there is a distinct synergistic effect between laser surface texturing and polymer brushes for improving tribological behaviors and biocompatibility. The prepared chitosan brushes on a textured surface are a strong mechanism for reducing friction force. The dimples took part in the hydrodynamic lubrication and acted as the container for replenishing the consumed lubricants. These brushes also promote the formation of a local lubricating film. The wear resistance of the chitosan brushes was immensely improved. Further, the worn process was observed, and the mechanism of destruction was demonstrated. Co-culturing with osteoblast cells showed that the texture and grafting have potential applications in enhancing the differentiation and orientation of osteoblast cells.

Bioinspired surface modification of orthopedic implants for bone tissue engineering

Biomedical implants have been widely used in various orthopedic treatments, including total hip arthroplasty, joint arthrodesis, fracture fixation, non-union, dental repair, etc. The modern research and development of orthopedic implants have gradually shifted from traditional mechanical support to a bioactive graft in order to endow them with better osteoinduction and osteoconduction. Inspired by structural and mechanical properties of natural bone, this review provides a panorama of current biological surface modifications for facilitating the interaction between medical implants and bone tissue and gives a future outlook for fabricating the next-generation multifunctional and smart implants by systematically biomimicking the physiological processes involved in formation and functioning of bones.

Reconstructive Science in Orthopedic Oncology

Limb salvage is widely practiced as standard of care in most cases of extremity bone sarcoma. Allograft and endoprosthesis reconstructions are the most widely utilized modalities for the reconstruction of large segment defects, however complication rates remain high. Aseptic loosening and infection remain the most common modes of failure. Implant integration, soft-tissue function, and infection prevention are crucial for implant longevity and function. Macro and micro alterations in implant design are reviewed in this manuscript. Tissue engineering principles using nanoparticles, cell-based, and biological augments have been utilized to develop implant coatings that improve osseointegration and decrease infection. Similar techniques have been used to improve the interaction between soft tissues and implants. Tissue engineered constructs (TEC) used in combination with, or in place of, traditional reconstructive techniques may represent the next major advancement in orthopaedic oncology reconstructive science, although preclinical results have yet to achieve durable translation to the bedside.

Fabricating hierarchical micro and nano structures on implantable Co-Cr-Mo alloy for tissue engineering by one-step laser ablation

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co-Cr-Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co-Cr-Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co-Cr-Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants.

Surface modification of chitosan film via polydopamine coating to promote biomineralization in bone tissue engineering

Chitosan-based material has been widely used as bone substitute due to its good biocompatibility and biodegradability. However, the hydrophobic surface of chitosan film constrains the osteogenesis mineralization in the process of bone regeneration. For this reason, we develop a novel polydopamine-modified chitosan film suitable for bone tissue engineering applications by a simple and feasible route in this study. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the process of surface modification. For comparison, surface wettability, the capacity of mineralization in vitro, and biocompatibility of the chitosan film and the polydopamine-modified chitosan film were assessed. Research results indicate that the polydopamine-modified chitosan film has good hydrophilicity. It is very evident that the polydopamine treatment significantly influences the biomineralization capacity of the chitosan-based substrates, which enhance the growth rate of apatite on the modified chitosan film. Besides, MC3T3-E1 osteoblast experiments demonstrate that the cells can adhere and grow well on the polydopamine-modified chitosan film. It is anticipated that this polydopamine-modified chitosan film, which can be prepared in large quantities simply, should have potential applications in bone tissue engineering.

Antimicrobial technology in orthopedic and spinal implants

Infections can hinder orthopedic implant function and retention. Current implant-based antimicrobial strategies largely utilize coating-based approaches in order to reduce biofilm formation and bacterial adhesion. Several emerging antimicrobial technologies that integrate a multidisciplinary combination of drug delivery systems, material science, immunology, and polymer chemistry are in development and early clinical use. This review outlines orthopedic implant antimicrobial technology, its current applications and supporting evidence, and clinically promising future directions.