Impaired dental implant osseointegration in rat with streptozotocin-induced diabetes.

OBJECTIVE: Few studies have reported on the impact of oxidative stress on the dental implant failure. The aim of this study was to investigate the impact of hyperglycemia-induced oxidative stress on dental implant osseointegration in diabetes mellitus (DM). METHODS: Acid-treated titanium implants were bilaterally placed in the maxillary alveolar ridge of streptozotocin-induced diabetic (DM group) and control rats after extraction of first molars. Histological analysis and micro-push-out test were performed 4 weeks after surgery. Oxidative stress and osteogenic markers in the surrounding bone were quantified by real-time polymerase chain reaction. In the in vitro study, rat bone marrow-derived mesenchymal stem cells (BMMSCs) were cultured on acid-treated titanium discs in a high-glucose (HG) or normal environment. Intracellular reactive oxygen species (ROS), cell proliferation, alkaline phosphatase (ALP) activity, and extracellular calcification were evaluated following antioxidant treatment with N-acetyl-L-cysteine (NAC). RESULTS: The implant survival rate was 92.9% and 75.0% in control and DM group, respectively. Bone-implant contact and push-out loads were significantly lower in the DM group. Expression of superoxide dismutase 1 at the mRNA level and on immunohistochemistry was significantly lower in the DM group. In vitro experiments revealed that the HG condition significantly increased ROS expression and suppressed the proliferation and extracellular calcification of BMMSCs, while NAC treatment significantly restored ROS expression, cell proliferation, and calcification. The ALP activity of both groups was not significantly different. CONCLUSION: In diabetes, high-glucose-induced oxidative stress downregulates proliferation and calcification of BMMSCs, impairing osseointegration and leading to implant failure.

Biocompatibility of titanium from the viewpoint of its surface.

Among metals, Ti and majority of its alloys exhibit excellent biocompatibility or tissue compatibility. Although their high corrosion resistance is a factor in the biocompatibility of Ti and Ti alloys, it is clear that other factors exist. In this review, the corrosion resistance and passive film of Ti are compared to those of other metallic biomaterials, and their band gap energies, Egs, are compared to discuss the role of Eg in the reactivity with living tissues. From the perspective of the material's surface, it is possible to explain the excellent biocompatibility of Ti by considering the following factors: Ti ions are immediately stabilized not to show toxicity if it is released to body fluids; good balance of positive and negative charges by the dissociation of surface hydroxyl groups on the passive film; low electrostatic force of the passive film inducing a natural adsorption of proteins maintaining their natural conformation; strong property as n-type semiconductor; lower band gap energy of the passive film on Ti generating optimal reactivity; and calcium phosphate formation is caused by this reactivity. The results suggest that due to the passive oxide film, the optimal balance between high corrosion resistance and appropriate reactivity of Ti is the predominate solution for the excellent biocompatibility of Ti.

Band structures of passive films on titanium in simulated bioliquids determined by photoelectrochemical response: principle governing the biocompatibility.

The band structures and band gap energies, E g, of passive films formed on titanium (Ti) in simulated bioliquids, Hanks' solution (Hanks) and saline, were evaluated. Ti was polarized at 0, -0.1, and -0.2 VAg/AgCl, E f, for 1 h. After polarization, the surfaces were characterized using X-ray photoelectron spectroscopy, and the photoelectrochemical responses were evaluated. The current change during photoirradiation was recorded as a photocurrent transient at each measuring potential, E m, and by changing the wavelength of the incident light. Passive films consisted of a very thin TiO2 layer containing small amounts of Ti2O3 and TiO, hydroxyl groups, and water. During polarization in Hanks, calcium and phosphate ions were incorporated or formed calcium phosphate but not in saline. Calcium phosphate and hydroxyl groups influenced the band structure. E g was graded in Hanks but constant in saline, independent of E f and E m. The passive film on Ti behaved as an n-type semiconductor containing two layers: an inner oxide layer with a large E g and an outer hydroxide layer with a small E g. In Hanks, E g was 3.3-3.4 eV in the inner oxide layer and 2.9 eV in the outer hydroxide layer. In saline, E g was 3.3 eV in the inner layer and 2.7 eV in the outer layer. Calcium phosphate and hydroxyl groups influenced the band structure of the passive film. The E g of the outermost surface was smaller than that of TiO2 ceramics, which is probably one of the principles of the excellent biocompatibility of Ti among metals.

Comparison of microstructures and mechanical properties of 3 cobalt-chromium alloys fabricated with soft metal milling technology.

STATEMENT OF PROBLEM: Although several manufacturers market soft metal milling blanks and systems, comprehensive comparative studies of differences in properties across commercially available soft metal milling alloys are lacking. PURPOSE: The purpose of this in vitro study was to compare the microstructures and mechanical properties of 3 soft metal milling cobalt-chromium (Co-Cr) alloys (Ceramill Sintron, Soft Metal, and Sintermetall). MATERIAL AND METHODS: Disk-shaped specimens (for surface characterization and hardness test) and dumbbell-shaped specimens (for tensile test as per International Organization for Standardization (ISO) 22674) were prepared by following each soft metal milling manufacturer's instructions. The crystal structures and microstructures of the 3 alloys were evaluated with optical microscopy, X-ray diffractometry (XRD), and scanning electron microscopy with electron backscattered diffraction (EBSD). The mechanical properties were investigated with a tensile test and Vickers hardness test (n=6). The results of the mechanical (tensile and hardness) tests were analyzed with 1-way ANOVA and the post hoc Tukey multiple comparison test (α=.05). RESULTS: The Sintermetall specimen showed a finer microstructure and more porosity than the other 2 alloys. The XRD and EBSD analyses showed that the γ (face-centered cubic, fcc) matrix phase was predominant in the Ceramill Sintron alloy and the ε (hexagonal close-packed, hcp) matrix phase was predominant in the Soft Metal alloy. The Sintermetall alloy showed a slightly higher amount of ε phase than γ phase, with more chromium carbide formation than the other 2 alloys. The Ceramill Sintron alloy showed a significantly higher tensile strength than the other 2 alloys (P<.05), but a significantly lower 2% offset yield strength than the other 2 alloys (P<.05). The highest elongation was found in the Ceramill Sintron alloy, followed by the Sintermetall and Soft Metal alloys. The elastic modulus was the highest in the Sintermetall alloy, followed by the Soft Metal and Ceramill Sintron alloys. No significant differences in Vickers hardness values were detected among the 3 alloys (P=.263). CONCLUSIONS: The different commercially available soft metal milling blanks and systems produced dissimilar alloys in terms of crystal structures and microstructures and, as a result, different mechanical properties.

Time Transient of Calcium and Phosphate Ion Adsorption by Rutile Crystal Facets in Hanks' Solution Characterized by XPS.

For the elucidation of the mechanism of calcium phosphate formation on commercially pure titanium (CP Ti) in the human body, rutile TiO2 single crystal plates with (001), (110), and (111) facets, namely, TiO2(001), TiO2(110), and TiO2(111), and polycrystalline plates (TiO2(poly)) were immersed in a simulated body fluid, Hanks' solution (Hanks), for 100-105 s, and the adsorption of calcium and phosphate ions was precisely characterized employing X-ray photoelectron spectroscopy (XPS). Previously published CP Ti data were used for comparison. Prior to immersion in Hanks, oxygen content was more than twice as high as that of titanium due to the existence of hydroxyl groups and water on the oxides. After immersion in Hanks, the composition and chemical state of the TiO2 substrates remained unchanged. Among the electrolytes contained in Hanks, only calcium and phosphate ions were adsorbed by and incorporated onto TiO2 surfaces. Adsorption of calcium ions onto rutile did not exhibit any systematic increase of calcium with immersion time except TiO2(poly). Adsorption of phosphate ions was initially constant, followed by an increase with the logarithm of immersion time. The adsorption rate of phosphate ions decreased in the following order: TiO2(001), TiO2(poly), TiO2(111), CP Ti, and TiO2(110). The coordination number and band gap of each crystal facet of rutile is important for the adsorption and incorporation of phosphate ions. Regular calcium phosphate formation on CP Ti is possibly enabled by the surface oxide film, which consists chiefly of amorphous TiO2. However, calcium phosphate formation kinetics on CP Ti differed from those on the TiO2 crystalline phase. These findings may further the understanding of CP Ti hard tissue compatibility.

Effect of Post-Sintering Conditions on the Mechanical Properties of a New Co-Cr Alloy Produced by New Subtractive Manufacturing.

In this study, we investigated the effect of sintering temperature (1300, 1350, or 1400 °C) and holding time (1 or 2 h) on the mechanical properties of a cobalt-chromium (Co-Cr) alloy (Soft Metal) produced by milling/post-sintering, using a tensile test (n = 6). Prior to the test, the different nanostructures arising from the sintering conditions were also analyzed. The phase ratio of γ (face-centered cubic) phase to ɛ (hexagonal close-packed) phase increased mainly with increasing temperature. The formation of Cr23C6 carbide was greatest in the 1350 °C groups when compared to the other temperature groups. The 1400 °C groups had a substantially greater grain size than the 1300 °C and 1350 °C groups, together with a significant number of annealing twins inside the matrix phases. Overall, the 1350 °C groups showed the most superior properties. The 1400 °C groups showed a mean 0.2% yield strength under 500 MPa. The holding times did not significantly affect the mechanical properties (p > 0.05).

Deposition of boron doped DLC films on TiNb and characterization of their mechanical properties and blood compatibility.

Diamond-like carbon (DLC) material is used in blood contacting devices as the surface coating material because of the antithrombogenicity behavior which helps to inhibit platelet adhesion and activation. In this study, DLC films were doped with boron during pulsed plasma chemical vapor deposition (CVD) to improve the blood compatibility. The ratio of boron to carbon (B/C) was varied from 0 to 0.4 in the film by adjusting the flow rate of trimethylboron and acetylene. Tribological tests indicated that boron doping with a low B/C ratio of 0.03 is beneficial for reducing friction (µ = 0.1), lowering hardness and slightly increasing wear rate compared to undoped DLC films. The B/C ratio in the film of 0.03 and 0.4 exhibited highly hydrophilic surface owing to their high wettability and high surface energy. An in vitro platelet adhesion experiment was conducted to compare the blood compatibility of TiNb substrates before and after coating with undoped and boron doped DLC. Films with highly hydrophilic surface enhanced the blood compatibility of TiNb, and the best results were obtained for DLC with the B/C ratio of 0.03. Boron doped DLC films are promising surface coatings for blood contacting devices.

Modulation of friction dynamics in water by changing the combination of the loop- and graft-type poly(ethylene glycol) surfaces.

A Velcro-like poly(ethylene glycol) (PEG) interface was prepared in order to control the friction dynamics of material surfaces. Graft- and loop-type PEGs were formed on mirror-polished Ti surfaces using an electrodeposition method with mono- and di-amine functionalized PEGs. The friction dynamics of various combinations of PEG surfaces (i.e., graft-on-graft, loop-on-loop, graft-on-loop, and loop-on-graft) were investigated by friction testing. Here, only the Velcro-like combinations (graft-on-loop and loop-on-graft) exhibited a reversible friction behavior (i.e., resetting the kinetic friction coefficient and the reappearance of the maximum static friction coefficient) during the friction tests. The same tendency was observed when the molecular weights of loop- and graft-type PEGs were tested at 1 k and 10 k, respectively. This indicates that a Velcro-like friction behavior could be induced by simply changing the conformation of PEGs, which suggests a novel concept of altering polymer surfaces for the effective control of friction dynamics.

Bone healing with oxytocin-loaded microporous ß-TCP bone substitute in ectopic bone formation model and critical-sized osseous defect of rat.

AIM: This study investigated the efficacy of the hypothalamic nonapeptide oxytocin (OT) by direct delivery to local defects using a microporous ß-tricalcium phosphate (TCP) as the carrier for the future applications as a method to achieve predictable bone regeneration of large osseous defects requiring sinus bone graft and guided bone regeneration procedures for implant placement. MATERIAL AND METHODS: Both the ectopic and new bone formation induced by the OT-loaded microporous ß-TCP powder was histomorphometrically compared with unloaded ß-TCP in a subcutaneous ectopic bone formation model and calvarial critical-sized defects (CSDs) in 45 rats. RESULTS: The OT-loaded ß-TCP clearly enhanced ectopic bone formation compared with the unloaded control group. A High initial OT dose (250 µg) significantly increased ectopic bone formation at an early healing time-point compared with a lower OT dose (50 µg). The OT-loaded samples displayed greater new bone formation in the rat calvarial CSDs. Extensive new bone formation was achieved in the calvarial CSDs with the higher OT dose. CONCLUSION: These results suggest that local OT delivery to bone substitute promotes new bone formation via an osteoinductive mode of action.

Influence of stress-relieving heat treatments on the efficacy of Co-Cr-Mo-W alloy copings fabricated using selective laser melting.

Purpose This study aimed to evaluate the influence of stress-relieving heat treatments on the metal-ceramic bond strength and fitness accuracy of selective laser melting (SLM)-fabricated Co-Cr alloy copings.Methods SLM-manufactured Co-Cr samples were stress-relieved at 750 (Ht-750) and 1150 °C (Ht-1150). The microstructure, surface roughness, metal-ceramic bond strength, marginal and internal fit, Vickers hardness, and residual stress were then compared with those of the non-heat-treated group (As-built). The results were analyzed using one-way ANOVA and post-hoc tests (Tukey's or Student's t test) (P = 0.05).Results The microstructure of the Ht-1150 samples had a brittle oxide layer and lower surface roughness, resulting in significantly lower bond strength values than those of the other groups. The As-built group exhibited significantly lower marginal gap values than the Ht-750 and Ht-1150 groups. Therefore, the post-heat treatments degraded the marginal fitness. The surface residual stress in all sample groups were compressive because of the sandblasting effect. The compressive stresses were larger in Ht-1150 than in As-built and Ht-750 owing to their low hardness values.Conclusions Stress-relief annealing porcelain-fused-to-metal single crowns does not improve bond strength and degrades fitness accuracy because additional post-heat treatments induce thermal distortion. These findings are expected to facilitate the direct application of As-built SLM single crowns in dentistry to minimize post-manufacturing costs and time.

Effect of luting system with acidic primers on the durability of bonds with Ti-15Mo-5Zr-3Al titanium alloy and its component metals.

This study evaluated the effect of luting system with acidic primers on the durability of bonds with Ti-15Mo-5Zr-3Al titanium alloy (Ti-15Mo-5Zr-3Al) and its component metals. Adherend metals were Ti-15Mo-5Zr-3Al, Ti, Mo, Zr, and Al. Four primers were evaluated as adhesion promoters: Alloy Primer (ALP), Estenia Opaque Primer (EOP), M. L. Primer (MLP), and Super Bond liquid (SBL). An acrylic resin was used as the luting material. Pre- and post-thermocycling shear bond strength was determined to evaluate the bonding durability, and the results were compared using non-parametric statistical analyses (n=11/group). The post-thermocycling bond strength in MPa (median) associated with ALP, EOP, MLP, and SBL were 18.8, 19.8, 4.1, and 0.8, respectively, for Ti-15Mo-5Zr-3Al. The results showed that two primers containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) were effective for the durability of bonding of Ti-15Mo-5Zr-3Al to the resin. MDP enhanced the bonding durability of the resin bonded to either Ti, Zr, or Al.

Effect of ultraviolet irradiation treatment on shear bond strength between polymethyl methacrylate and cobalt-chromium-molybdenum alloy.

We aimed to elucidate the effects of ultraviolet (UV) irradiation on the shear bond strength (SBS) between heat-cured polymethyl methacrylate (PMMA) and a Co-Cr-Mo alloy. Disk-shaped Co-Cr-Mo alloy prepared by casting were subjected to different UV treatment times (0, 15, and 30 min). To determine the effect of UV treatment on surface properties of the alloy, surface roughness, wettability, and chemical compositions were analyzed. To evaluate the SBS, cylindrical PMMA was bonded to the UV-treated alloy, and subsequently subjected to the SBS test after 24 h of storage at room temperature or following 10,000 thermal cycles (n=10/group). After the UV treatment, the surface roughness remained unchanged, but oxidation resulted in the surface exhibiting greater hydrophilic characteristics. The UV-treated group showed significantly higher SBS values than those of the non-treated group (p<0.001). These results suggested that UV treatment-mediated oxidation improved the bond strength between PMMA and Co-Cr-Mo alloy.

Innovative design of bone quality-targeted intervertebral spacer: accelerated functional fusion guiding oriented collagen and apatite microstructure without autologous bone graft.

BACKGROUND CONTEXT: Although autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting. PURPOSE: We developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure. STUDY DESIGN: This was an in vivo animal study. METHODS: Intervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2-L3 or L4-L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests. RESULTS: The spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The push-out load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix. CONCLUSIONS: The developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft. CLINICAL SIGNIFICANCE: Our results provide a foundation for designing future spacers for interbody fusion in human.

Research and development of metals for medical devices based on clinical needs.

The current research and development of metallic materials used for medicine and dentistry is reviewed. First, the general properties required of metals used in medical devices are summarized, followed by the needs for the development of α + ß type Ti alloys with large elongation and ß type Ti alloys with a low Young's modulus. In addition, nickel-free Ni-Ti alloys and austenitic stainless steels are described. As new topics, we review metals that are bioabsorbable and compatible with magnetic resonance imaging. Surface treatment and modification techniques to improve biofunctions and biocompatibility are categorized, and the related problems are presented at the end of this review. The metal surface may be biofunctionalized by various techniques, such as dry and wet processes. These techniques make it possible to apply metals to scaffolds in tissue engineering.

Evaluation of cytocompatibility and osteoconductivity of Zr-14Nb-5Ta-1Mo alloy with MC3T3-E1 cells.

The cytocompatibility and osteoconductivity of the Zr-14Nb-5Ta-1Mo alloy were investigated using a mouse osteoblastic cell line (MC3T3-E1) to promote the application of this newly developed alloy in dental/medical treatment. The initial cell-attached morphology was visualized by fluorescent staining, and cells cultured on the Zr alloy showed similar cell adhesion behavior to cells cultured on titanium (Ti). In our 5-day proliferation investigation, similar cell numbers were obtained with both Zr alloy and Ti. These results indicate that the cytocompatibility of Zr alloy is similar to that of Ti. In addition, the similar results in the evaluation of alkaline phosphatase (ALP) activity and staining of deposited calcium using alizarin red S with both Zr alloy and Ti indicated that the osteoconductivity of the Zr alloy is similar to that of Ti. Our results prove the good cytocompatibility and osteoconductivity of the Zr-14Nb-5Ta-1Mo alloy, enabling its promotion for use in dental/medical applications.

Surface properties and biocompatibility of sandblasted and acid-etched titanium-zirconium binary alloys with various compositions.

Ti-Zr alloys have been investigated as an alternative to commercially pure Ti (c.p.Ti). According to our previous studies on the mechanical properties of Ti-Zr alloys, a Zr proportion in the range of 30-50 mol% has competitive advantages over Ti-10Zr and c.p.Ti. The aim of this study is to evaluate the biological response to Ti-Zr alloys with different compositions and their surface characteristics. Alloy surfaces are modified by sandblasting and sulfuric acid etching. As a result, similar surface structures are observed for c.p.Ti, Ti-10Zr, and Ti-30Zr, whereas Ti-50Zr does not form a micro-rough structure by the same treatment process. No significant difference is found in the viability of cells on c.p.Ti, Ti-10Zr, and Ti-30Zr, whereas lower cell attachment levels are detected on Ti-50Zr. In summary, Ti-30Zr reliably forms a micro-rough structure, which provides one evidence for its application in a new dental implant material.

Effect of Rotational Modes on Torque/Force Generation and Canal Centering Ability during Rotary Root Canal Instrumentation with Differently Heat-Treated Nickel-Titanium Instruments.

This study aimed to evaluate how various rotational modes influence the torque/force production and shaping ability of ProTaper Universal (PTU; non-heat-treated) and ProTaper Gold (PTG; heat-treated) nickel−titanium instruments. J-shaped resin canals were instrumented with PTU or PTG using an automated instrumentation device operated with reciprocating rotation [150° clockwise and 30° counterclockwise (R150/30) or 240° clockwise and 120° counterclockwise (R240/120)], optimum torque reverse motion (OTR), or continuous rotation (CR) (n = 10 each). Maximum force and torque were recorded, and canal centering ratios were calculated. Statistical analysis was performed with two-way ANOVA and a Bonferroni test (α = 0.05). The results were considered with reference to previous studies on the microstructure of the instruments. The upward force generated by R240/120 and OTR was smaller than that generated by R150/30 and CR in PTG (p < 0.05). The clockwise torque produced by OTR was lower than that produced by R150/30 in PTU and R240/120 and CR in PTG (p < 0.05). R240/120 and OTR induced less canal deviation compared to CR in PTU at 0 mm from the apex (p < 0.05). In conclusion, R240/120 and OTR reduced the screw-in force in PTG and improved the canal centering ability in PTU, which may be associated with the heat treatment-induced microstructural difference of the two instruments.

Outstanding in vivo mechanical integrity of additively manufactured spinal cages with a novel "honeycomb tree structure" design via guiding bone matrix orientation.

BACKGROUND CONTEXT: Therapeutic devices for spinal disorders, such as spinal fusion cages, must be able to facilitate the maintenance and rapid recovery of spinal function. Therefore, it would be advantageous that future spinal fusion cages facilitate rapid recovery of spinal function without secondary surgery to harvest autologous bone. PURPOSE: This study investigated a novel spinal cage configuration that achieves in vivo mechanical integrity as a devise/bone complex by inducing bone that mimicked the sound trabecular bone, hierarchically and anisotropically structured trabeculae strengthened with a preferentially oriented extracellular matrix. STUDY DESIGN/SETTINGS: In vivo animal study. METHODS: A cage possessing an anisotropic through-pore with a grooved substrate, that we termed "honeycomb tree structure," was designed for guiding bone matrix orientation; it was manufactured using a laser beam powder bed fusion method through an additive manufacturing processes. The newly designed cages were implanted into sheep vertebral bodies for 8 and 16 weeks. An autologous bone was not installed in the newly designed cage. A pull-out test was performed to evaluate the mechanical integrity of the cage/bone interface. Additionally, the preferential orientation of bone matrix consisting of collagen and apatite was determined. RESULTS: The cage/host bone interface strength assessed by the maximum pull-out load for the novel cage without an autologous bone graft (3360±411 N) was significantly higher than that for the conventional cage using autologous bone (903±188 N) after only 8 weeks post-implantation. CONCLUSIONS: These results highlight the potential of this novel cage to achieve functional fusion between the cage and host bone. Our study provides insight into the design of highly functional spinal devices based on the anisotropic nature of bone. CLINICAL SIGNIFICANCE: The sheep spine is similar to the human spine in its stress condition and trabecular bone architecture and is widely recognized as a useful model for the human spine. The present design may be useful as a new spinal device for humans.

Enhancement of antibacterial property of titanium by two-step micro arc oxidation treatment.

A customized micro arc oxidation (MAO) treatment technique was developed to obtain desirable antibacterial properties on titanium surfaces. The two-step MAO treatment was applied to fabricate a specimen containing both Ag and Zn in its surface oxide layer. Surface analyses and metal-ion release tests were performed to evaluate the presence of Ag and Zn and the ion release behavior for simulating practical usage, respectively. Additionally, the antibacterial properties of the specimens were also evaluated using gram-negative facultative anaerobic bacteria. The MAO-treated specimens containing both Ag and Zn showed excellent antibacterial properties against Escherichia coli, and the properties were sustained even after 28 days of immersion in physiological saline to simulate the living environment.