Tailoring Copper-Doped Bioactive Glass/Chitosan Coatings with Angiogenic and Antibacterial Properties

Implant coatings are frequently applied to modulate tissue response and delivery of drugs. Copper (Cu)-containing coatings on dental implant abutments have been proposed to improve soft tissue integration and reduce the risk for peri-implant infections. However, precise control over Cu loading and release kinetics remains a major challenge. In this study, we introduced a bottom-up coating deposition method based on nanoparticle assembly to allow for local release of Cu ions from implant surfaces. We first doped mesoporous bioactive glass (MBG) nanoparticles with various amounts of Cu. Subsequently, we suspended these Cu-doped MBG (Cu-MBG), Cu-free MBG nanoparticles, or mixtures thereof in chitosan solution and prepared a series of composite coatings on commercially pure titanium disks as model surfaces for transmucosal components of bone implants through electrophoretic deposition (EPD). By changing the Cu-MBG:MBG ratio of the composite coatings, we controlled the Cu release kinetics without changing other coating properties. Human gingival fibroblasts proliferated on the composite coatings except for coatings with the highest amount of Cu, which inhibited their proliferation. The migration rate of human umbilical vein endothelial cells cultured on the composite coatings was highest on coatings containing equal amounts of Cu-MBG and Cu-free MBG. Antibacterial tests confirmed that Cu-containing coatings reduced the growth of Porphyromonas gingivalis up to fivefold compared with uncoated implants. In conclusion, our data indicate that the EPD method is suitable to deposit nanoparticle-based coatings onto dental implants, which enhance endothelial cell migration and reduce bacterial growth.

Advancing bone tissue engineering one layer at a time: a layer-by-layer assembly approach to 3D bone scaffold materials

The layer-by-layer (LbL) assembly technique has shown excellent potential in tissue engineering applications. The technique is mainly based on electrostatic attraction and involves the sequential adsorption of oppositely charged electrolyte complexes onto a substrate, resulting in uniform single layers that can be rapidly deposited to form nanolayer films. LbL has attracted significant attention as a coating technique due to it being a convenient and affordable fabrication method capable of achieving a wide range of biomaterial coatings while keeping the main biofunctionality of the substrate materials. One promising application is the use of nanolayer films fabricated by LbL assembly in the development of 3-dimensional (3D) bone scaffolds for bone repair and regeneration. Due to their versatility, nanoscale films offer an exciting opportunity for tailoring surface and bulk property modification of implants for osseous defect therapies. This review article discusses the state of the art of the LbL assembly technique, and the properties and functions of LbL-assembled films for engineered bone scaffold application, combination of multilayers for multifunctional coatings and recent advancements in the application of LbL assembly in bone tissue engineering. The recent decade has seen tremendous advances in the promising developments of LbL film systems and their impact on cell interaction and tissue repair. A deep understanding of the cell behaviour and biomaterial interaction for the further development of new generations of LbL films for tissue engineering are the most important targets for biomaterial research in the field. While there is still much to learn about the biological and physicochemical interactions at the interface of nano-surface coated scaffolds and biological systems, we provide a conceptual review to further progress in the LbL approach to 3D bone scaffold materials and inform the future of LbL development in bone tissue engineering.

Preparation of Daidzein microparticles through liquid antisolvent precipitation under ultrasonication

In this study, daidzein microparticles (DMP) were prepared using an improved ultrasound-assisted antisolvent precipitation method. Preliminary experiments were conducted using six single-factor experiments, and principal component analysis (PCA) was adopted to obtain the three staple elements of the ultrasonic power, solution concentration, and nozzle diameter. The response surface Box-Behnken (BBD) design was used to optimize the level of the above factors. The optimal preparation conditions of the DMP were obtained as follows: the flow rate was 4 mL/min, the concentration of the daidzein solution was 16 mg/mL, the ratio of antisolvent to solvent (liquid-to-liquid ratio) was 9, the nozzle diameter was 300 μm, the ultrasonic power was 180 W (665 W/L), and the system speed was 760 r/min. The minimum average particle size of DMP was 181 ± 2 nm. The properties of daidzein particles before and after preparation were analyzed via scanning electron microscopy, X-ray diffraction analysis, Differential scanning calorimetry and Fourier transform infrared spectroscopy, no obvious change in its chemical structure was observed, but crystallinity was reduced. Compared with daidzein powder, DMP has a higher solubility and stronger antioxidant capacity. The above results indicate that the improved method of ultrasonication combined with antisolvent can reduce the size of daidzein particles and has a great potential in practical production.

Degradation Behavior of Polymers Used as Coating Materials for Drug Delivery-A Basic Review

The purpose of the work was to emphasize the main differences and similarities in the degradation mechanisms in the case of polymeric coatings compared with the bulk ones. Combined with the current background, this work reviews the properties of commonly utilized degradable polymers in drug delivery, the factors affecting degradation mechanism, testing methods while offering a retrospective on the evolution of the controlled release of biodegradable polymeric coatings. A literature survey on stability and degradation of different polymeric coatings, which were thoroughly evaluated by different techniques, e.g., polymer mass loss measurements, surface, structural and chemical analysis, was completed. Moreover, we analyzed some shortcomings of the degradation behavior of biopolymers in form of coatings and briefly proposed some solving directions to the main existing problems (e.g., improving measuring techniques resolution, elucidation of complete mathematical analysis of the different degradation mechanisms). Deep studies are still necessary on the dynamic changes which occur to biodegradable polymeric coatings which can help to envisage the future performance of synthesized films designed to be used as medical devices with application in drug delivery.

Electrodeposition of Polysaccharide and Protein Hydrogels for Biomedical Applications

In the last few decades, polysaccharide and protein hydrogels have attracted significant attentions and been applied in various engineering fields. Polysaccharide and protein hydrogels with appealing physical and biological features have been produced to meet different biomedical applications for their excellent properties related to biodegradability, biocompatibility, nontoxicity, and stimuli responsiveness. Numerous methods, such as chemical crosslinking, photo crosslinking, graft polymerization, hydrophobic interaction, polyelectrolyte complexation and electrodeposition have been employed to prepare polysaccharide and protein hydrogels. Electrodeposition is a facile way to produce different polysaccharide and protein hydrogels with the advantages of temporal and spatial controllability. This paper reviews the recent progress in the electrodeposition of different polysaccharide and protein hydrogels. The strategies of pH induced assembly, Ca2+ crosslinking, metal ions induced assembly, oxidation induced assembly derived from electrochemical methods were discussed. Pure, binary blend and ternary blend polysaccharide and protein hydrogels with multiple functionalities prepared by electrodeposition were summarized. In addition, we have reviewed the applications of these hydrogels in drug delivery, tissue engineering and wound dressing.

Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) improved osteogenic differentiation of the human induced pluripotent stem cells while considered as an artificial extracellular matrix

Cocell polymers can be the best implants for replacing bone defects in patients. The pluripotent stem cells produced from the patient and the nanofibrous polymeric scaffold that can be completely degraded in the body and its produced monomers could be also usable are the best options for this implant. In this study, electrospun poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibers were fabricated and characterized and then osteogenic differentiation of the human-induced pluripotent stem cells (iPSCs) was investigated while cultured on PHBV scaffold. MTT results showed that cultured iPSCs on PHBV proliferation were increased compared to those cultured on tissue culture polystyrene (TCPS) as the control. Alkaline phosphatase (ALP) activity and calcium content were also significantly increased in iPSCs cultured on PHBV compared to the cultured on TCPS under osteogenic medium. Gene expression evaluation demonstrated that Runx2, collagen type I, ALP, osteonectin, and osteocalcin were upregulated in iPSCs cultured on PHBV scaffold in comparison with those cultured on TCPS for 2 weeks. Western blot analysis have shown that osteocalcin and osteopontin expression as two major osteogenic markers were increased in iPSCs cultured on PHBV scaffold. According to the results, nanofiber-based PHBV has a promising potential to increase osteogenic differentiation of the stem cells and iPSCs-PHBV as a cell-co-polymer construct demonstrated that has a great efficiency for use as a bone tissue engineered bioimplant.

Surface Modification of SPIONs in PHBV Microspheres for Biomedical Applications

Surface modification of superparamagnetic iron oxide nanoparticles (SPIONs) has been introduced with lauric acid and oleic acid via co-precipitation and thermal decomposition methods, respectively. This modification is required to increase the stability of SPIONs when incorporated in hydrophobic, biodegradable and biocompatible polymers such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). In this work, the solid-in-oil-in-water (S/O/W) emulsion-solvent extraction/evaporation method was utilized to fabricate magnetic polymer microspheres incorporating SPIONs in PHBV. The prepared magnetic PHBV microspheres exhibited particle sizes <1 µm. The presence of functional groups of lauric acid, oleic acid and iron oxide in the PHBV microspheres was confirmed by Fourier Transform Infrared spectroscopy (FTIR). X-ray diffraction (XRD) analysis was performed to further confirm the success of the combination of modified SPIONs and PHBV. Thermogravimetric analysis (TGA) indicated that PHBV microspheres were incorporated with SPIONs^Lauric as compared with SPIONs^Oleic. This was also proven via magnetic susceptibility measurement as a higher value of this magnetic property was detected for PHBV/SPIONs^Lauric microspheres. It was revealed that the magnetic PHBV microspheres were non-toxic when assessed with mouse embryotic fibroblast cells (MEF) at different concentrations of microspheres. These results confirmed that the fabricated magnetic PHBV microspheres are potential candidates for use in biomedical applications.

Electric Field-Assisted Orientation of Short Phosphate Glass Fibers on Stainless Steel for Biomedical Applications

Structural and compositional modifications of metallic implant surfaces are being actively investigated to achieve improved bone-to-implant bonding. In this study, a strategy to modify bulk metallic surfaces by electrophoretic deposition (EPD) of short phosphate glass fibers (sPGF) is presented. Random and aligned orientation of sPGF embedded in a poly(acrylic acid) matrix is achieved by vertical and horizontal EPD, respectively. The influence of EPD parameters on the degree of alignment is investigated to pave the way for the fabrication of highly aligned sPGF structures in large areas. Importantly, the oriented sPGF structure in the coating, owing to the synergistic effects of bioactive composition and fiber orientation, plays an important role in directional cell migration and enhanced proliferation. Moreover, gene expression of MC3T3-E1 cells cultured with different concentrations of sPGF is thoroughly assessed to elucidate the potential stimulating effect of sPGF on osteogenic differentiation. This study represents an innovative exploitation of EPD to develop textured surfaces by orientation of fibers in the macroscale, which shows great potential for directional functionalization of metallic implants.

Electrophoretic deposition: a versatile tool against biomaterial associated infections

Biomaterial-associated infections (BAIs) are today considered as one of the most withering complications of orthopedic implant surgery. Even though BAIs occur relatively infrequently in primary joint replacement surgeries (incidence rates around 1-2%), revision arthroplasties carry up to 40% risk of infection recurrence, with devastating consequences for the patient and significant associated cost. Once the responsible pathogens, mainly bacteria, attach to the surface of the biomaterial, they start creating layers of extracellular matrix with complex architectures, called biofilms. These last mentioned, encapsulate and protect bacteria by hindering the immune response and impeding antibiotics from reaching the pathogens. To prevent such an outcome, the surface of the biomaterials, in particular implants, can be modified in order to play the role of inherent drug delivery devices or as substrates for antibacterial/multifunctional coating deposition. This paper presents an overview of novel electrochemically-triggered deposition strategies, with a focus on electrophoretic deposition (EPD), a versatile and cost-effective technique for organic and inorganic material deposition. Other than being a simple deposition tool, EPD has been recently employed to create novel micro/nanostructured surfaces for multi-purpose antibacterial approaches, presented in detail in this review. In addition, a thorough comparison and assessment of the latest antibacterial and multifunctional compounds deposited by means of EPD have been reported, followed by a critical reflection on current and future prospects of the topic. The relative simplicity of EPD's application, has, by some means, undermined the fundamental requirement of rationality of multifunctional coating design. The demanding practical needs for a successful clinical translation in the growing fields of tissue engineering and antibacterial/multifunctional implant coatings, calls for a more systematic in vitro experimental design rationale, in order to make amends for the scarcity of significant in vivo and clinical studies.

Bilayered BMP2 Eluting Coatings on Graphene Foam by Electrophoretic Deposition: Electroresponsive BMP2 Release and Enhancement of Osteogenic Differentiation

Recent development of three-dimensional graphene foam (GF) with conductive and interconnected macroporous structure is attracting particular attention as platforms for tissue engineering. However, widespread application of GF as bone scaffolds is restricted due to its poor mechanical property and inert surface character. To overcome these drawbacks, in this study, a bilayered biopolymer coating was designed and successfully deposited covering the entire surface area of GF skeleton. A poly(lactic-co-glycolic acid) layer was first dip-coated to strengthen the GF substrate, followed by the electrophoretic codeposition of a hybrid layer, consisting of chitosan and BMP2, to functionalize GF with the ability to recruit and induce osteogenic differentiation of hMSC. Our data indicated that the mechanical property of GF was significantly increased without compromising the macroporous structure. Importantly, the immobilized BMP2 exhibited sustained and electroresponsive release profiles with rapid response to the electric field exerted on GF, which is beneficial to balancing BMP2 dose in a physiological environment. Moreover, the osteogenic differentiation of hMSC was significantly improved on the functionalized GF. Taking advantage of the unique macrostructure from GF as well as the superior mechanical properties and BMP2 release profile supported by the deposited coatings, it is therefore expected that the developed GF could be a promising alternative as innovative bone-forming favorable scaffolds.

Electrophoretic deposition of chitosan/gelatin coatings with controlled porous surface topography to enhance initial osteoblast adhesive responses

Electrophoretically deposited (EPD) coatings have often been employed recently for the addition of different new chemical compositions to classic chitosan coatings to improve the biocompatibility and therapeutic potential of coated implants. However, little attention has been paid to enhance the cell response to EPD coatings via integrating the effects of chemical components and surface topography. Here, we fabricated EPD chitosan/gelatin (CS/G) coatings with controlled porous surface topography by controlling bubble generation in the EPD process via changing the gelatin content in solution from 0, 0.01, 0.1, and 1 to 10 mg ml^-1. The pure chitosan coating surface was characterized by homogeneous large pores of 500 μm. After 0.01 mg ml^-1 gelatin was added, 180 μm small pores appeared on the walls of large pores. As the gelatin content increased to 0.1 mg ml^-1, a number of small pores increased noticeably. When the gelatin content reached 1 mg ml^-1, large pores disappeared, and the coating displayed homogeneous small pores. 10 mg ml^-1 gelatin concentration led to coatings consisting of small pores with not integral and continuous structures. The initial osteoblastic responses, including cell adherence progress, spreading area, proliferation rate, and focal adhesion-related gene expression, gradually improved from 0 to 0.01, 0.1, and 1 mg ml^-1 gelatin content, but decreased from 1 to 10 mg ml^-1. All these results indicated that the initial cell responses to coatings reached a peak when it was 1 mg ml^-1 gelatin and they had homogeneous small pores, which might contribute to the synergistic effects of the porous surface structure and components. This work would be beneficial for expanding the potential application of EPD coatings.