•A surface organic-inorganic coating via electrophoretic deposition can exhibit a sustained-release behavior of zinc.•This coating presents antibacterial abilities in a concentration-dependent manner and also benefits the growth of osteoblasts.•The chemical composition of the coatings and their formation mechanism were explored via XRD, XPS and SAED analysis.Increased use of reconstruction procedures in orthopedics has improved the life of patients undergoing surgery. However, surgical site infection remains a major challenge. Efforts were made to fabricate antibacterial surfaces with good biocompatibility. This present study aimed to fabricate zinc-incorporated chitosan/gelatin (CS/G) nanocomposite coatings on the titanium substrates via electrophoretic deposition (EPD). Physicochemical characterization confirmed that zinc was successfully deposited in a metallic oxide/salt complex status. Transmission electron microscopic (TEM) results observed formation of core-shell nanosized particles released from the coatings. The selected-area electron diffraction (SAED) pattern of the particles presented faces of ZnO with organic background. Mechanical tests showed improved tensile and shear bond strength between substrates and zinc-incorporated coating surfaces. Zinc-incorporated CS/G coatings presented antibacterial abilities against both Gram-negative E. coli and Gram-positive S. aureus in a concentration-dependent manner. The generation of ZnO/Zn2+ complex in the coatings may contribute to bacteria inhibition. In vitro study demonstrated that appropriate concentration of zinc could promote proliferative and osteogenic activities of rat bone marrow stromal cells. The present study suggested that zinc-incorporated CS/G coating was a promising candidate for surface modification of biomedical materials.Download high-res image (125KB)Download full-size image

Crystallinity is related to the degree of order and the crystal size of a given crystalline substance. It can affect the quality of hydroxyapatite (HA) and its abnormality can lead to diseases of hard mineralized tissues. Crystallinity index (CI) is a quantitative indicator of crystallinity. Various techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, and many methods based on these techniques have been used to define the CI of HA. The present study compares these methods and summarizes their characters for hydrothermally synthesized HA crystals with different aging time. Additionally, correlation coefficients between CIs calculated by different methods and crystal size (R12) and correlation coefficients among various CIs (R22) were obtained from linear-regression analysis. Scanning electron microscopy (SEM) was utilized as a supplementary technique to observe the morphological changes during the HA aging process. The results showed larger crystal size, increased crystallinity and more regular morphology of HA with increased aging time. All the R12 and R22 were above 0.9 and there were no significant differences between R12. However, different CI-calculating methods showed individual characters or limitations during their application. Such results suggested XRD, FTIR and Raman techniques used in this study were generally consistent and efficient but their special characters should be considered during their application. Researchers should choose certain appropriate technique and method to obtain CI on the basis of sample characteristics and experimental conditions.

Injected bone substitutes (IBSs) have become increasingly attractive in the field of tissue engineering due to their patient convenience, easy administration as well as minimally invasive procedure for tissue repair. To develop a novel and smart IBS with desirable properties for future in vivo bone regenerative, nano-sized hydroxyapatite (Nano-HA) or antibacterial Ag+, or a combination of them, was initially loaded into a chitosan–poly(vinyl alcohol) (CS–PVA) thermo-sensitive hydrogel. Then the functionalized hydrogel was mixed with PMMA to optimize the final bulk behaviors of the PMMA cement. Finally, the physicochemical properties, anti-bacterial activity, biomineralization ability, and mechanical property changes under simulated physiological conditions of the cements were tested by a type K thermocouple, scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-computed tomography (μ-CT), X-ray photoelectron spectroscopy (XPS), calcium ion test kit and mechanical compression tests. The results showed that the CS–PVA thermo-sensitive hydrogel decreased the Tmax, prolonged the working time, created irregular pores and led to appropriate mechanical properties of the cements. Nano-HA particles induced better mineralization capacity of the cements without acting negatively on the mechanical properties. Ag+ incorporation remarkably enhanced the anti-bacterial activity of the cements for prevention of post-operative infection. Ultimately, such results suggested the injectable and multi-functional cement with p-PMMA/CS–PVA/Nano-HA/Ag+ combination would hold strong promise for future bone reconstruction applications.

Biomedical metallic materials, such as titanium and stainless steel, have already been used in the clinic and tissue engineering fields for many years. However, the bio-inert surface limited and challenged their applications. The present study aimed to fabricate and characterize chitosan–gelatin (CSG) nanosphere based antibacterial coatings for surface functionalization of biomedical metallic materials. A CSG nanosphere coating was fabricated on titanium substrate via electrophoretic deposition (EPD). Tetracycline (Tc), as a model functional agent, was loaded into the coating during fabrication. The mechanism of fabricating Tc loaded CSG nanosphere coatings via EPD was investigated for the first time. Characterization of the coatings showed nanosphere structure, and nanospheres can be released from the coatings. The entrapment of Tc was confirmed by fluorescent microscope, Fourier transform infrared spectroscopy and X-ray diffraction. It could also be proved that new hydrogen bonds formed between Tc and gelatin, as well as the increased crystallinity of the coating. Mechanical test demonstrated enhanced mechanical interlocking in the coating-titanium interface of the high Tc concentration group. After coating preparation, the antibacterial effect of Tc was preserved both qualitatively and quantitatively. These results suggested that a Tc loaded CSG nanosphere coating could be successfully fabricated via EPD, and used for the functionalization of a titanium substrate. CSG nanosphere coating loaded with other functional agents would be a promising surface functionalization strategy for biomedical metallic materials.

When the enamel layer is breached due to external physical and chemical reasons, the underlying dentin is exposed to a wet and bacteria-laden oral environment. Accordingly, some diseases related to exposed dentin, such as dentin hypersensitivity and bacterial invasion, usually occur and affect patients' day-to-day lives. The aim of this study was to evaluate the effectiveness of injectable calcium phosphate cement (CPC) on occluding dentinal tubules and antibacterial properties when loaded with chlorhexidine (CHX) under a simulated oral environment, which was believed to be beneficial for dental biomimetic reconstruction and minimum intervention therapy. The particle size, surface morphology and composition of CPC were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The apatite formation ability, occluding effects, drug delivery and antibacterial properties of CPC and CHX-loaded CPC were further investigated using non-destructive attenuated total reflection infrared (ATR-IR) spectroscopy, Raman spectroscopy, SEM observation, permeability test, UV analysis and a disk-diffusion method. The results showed that both CPC and CHX-loaded CPC could continually form enamel-like apatite layers on the exposed dentin surface. After facing an acidic environment, the apatite layer still effectively occluded the dentinal tubules. Furthermore, CHX loaded CPC showed a sustained release of CHX over a timeframe of a week and revealed significant antibacterial effect compared to the blank control without CHX. Therefore, the results suggest that due to the unique self-setting ability, injectability, apatite-mineralization capacity and similar composition to a tooth, CPC could be used as a promising biomaterial to reconstruct the breached enamel on exposed dentin through a biomimetic and minimally invasive way. Moreover, due to the excellent drug-delivery property, CPC could easily carry antibiotics to inhibit the bacteria causing further pulp infection.

•Coatings based on chitosan, gelatin and strontium are proposed.•An organic-inorganic nanocomposite coatings are formed by electrophoretic deposition.•Nanocomposite coatings are deposited in a mild condition.•Strontium carbonate is produced in the coatings.•The strontium-containing coatings are favorable for proliferation and differentiation of MC3T3-E1 cells.Metal orthopedic implants still face challenges in some compromised conditions, partly due to bio-inertness. The present study aimed to functionalize metallic implants with organic-inorganic nanocomposite (strontium-containing chitosan/gelatin) coatings through a simple single-step electrophoretic deposition under mild conditions. The surface characterization and in vitro cellular response were studied and compared with chitosan/gelatin (CS/G) coatings. SEM images suggested the inorganic nanoparticles may be encapsulated within or mixed with organic polymers. The XRD patterns showed that strontium carbonate was generated in the coatings. The TEM images revealed strontium-containing nanoparticles were released from the coatings in PBS. The continuous release after the initial burst release ensured the enduring effects of the functionalized surface. The tensile bond strength of the coatings to the substrates increased after the addition of strontium. In vitro cellular study confirmed that strontium-containing coatings supported the proliferation of MC3T3-E1 cells and exhibited excellent ability to enhance the differentiation of such pre-osteoblasts. Therefore, such organic-inorganic nanocomposite coatings are a promising candidate to functionalize orthopedic implant surfaces.Schematic illustration of strontium-containing chitosan/gelating coatings using electrophoretic deposition method.

Injectable polymethylmethacrylate (PMMA) bone cement is a widely used bone substitute in cemented arthroplasty, vertebroplasty and osteoporosis fractures. However, due to the inappropriate stiffness, poor bioactivity and high polymerization temperature of PMMA, aseptic loosening of the implanted cement at the bone–cement interface still could be observed in a high rate of patients. To improve the performance of PMMA, artificial extracellular matrices like chitosan–glycerophosphate (CS–GP) thermosensitive hydrogel was introduced into PMMA acting as a pore forming agent and osteoconductive nano-sized hydroxyapatite (nano-HA)/antibiotic gentamicin (GM) as a carrier. It is shown that CS–GP thermosensitive hydrogel can effectively create open pores at the surface of the PMMA cement, which is believed to facilitate bone tissue ingrowth and improve the cement anchorage at the bone–cement interface in future clinical applications. Meanwhile, such a hydrogel effectively decreases the maximum polymerization temperature to below 30 °C, prolongs the working time to more than 720 s and produces cement with a proper modulus of elasticity and a compressive yield strength ranging from 402 to 584 MPa and from 3.1 to 5.9 MPa, respectively. Furthermore, the incorporated nano-HA particles sufficiently increase the mineralization capacity of the cement without compromising its mechanical properties and the incorporated GM remarkably enhances the anti-bacterial activity of the cement. More importantly, nano-HA and GM enriched CS–GP thermosensitive hydrogel effectively improve the overall performance of PMMA cement without influencing the cell survival, suggesting the injectable p-PMMA/CS–GP/nano-HA/GM cement will hold strong promise for future bone reconstruction applications.

The electrophoretic deposition (EPD) technique can be used to fabricate functional coating on titanium implant. In this study, chitosan/silk fibroin composite coatings were deposited onto titanium substrates viaEPD at about 4 °C, which was recommended for protein stability and cell viability. We tested the characterization and cell behavior of the hydrogel coatings. The obtained gelatinous coatings had a similar macroporous structure with pore size ranging from 100 to 300 μm. The silk fibroin content in the coatings increased proportionally with the increase of the silk fibroin in the electrophoretic solutions. The shear and tensile bond strength of the coatings to titanium substrates increased with the increasing silk fibroin content. In vitro biological tests indicated that chitosan/silk fibroin composite coatings had better cellular affinity than pure chitosan coatings. Therefore, the low temperature EPD is an advanced technique for preparing functional coating on titanium surface and chitosan/silk fibroin composite coatings are promising candidates for loading bioactive protein and appropriate cells.

The electrophoretic deposition (EPD) technique can be used to fabricate functional coating on titanium implant. In this study, chitosan/silk fibroin composite coatings were deposited onto titanium substrates viaEPD at about 4 °C, which was recommended for protein stability and cell viability. We tested the characterization and cell behavior of the hydrogel coatings. The obtained gelatinous coatings had a similar macroporous structure with pore size ranging from 100 to 300 μm. The silk fibroin content in the coatings increased proportionally with the increase of the silk fibroin in the electrophoretic solutions. The shear and tensile bond strength of the coatings to titanium substrates increased with the increasing silk fibroin content. In vitro biological tests indicated that chitosan/silk fibroin composite coatings had better cellular affinity than pure chitosan coatings. Therefore, the low temperature EPD is an advanced technique for preparing functional coating on titanium surface and chitosan/silk fibroin composite coatings are promising candidates for loading bioactive protein and appropriate cells.