Surface Physicochemical and Structural Analysis of Functionalized Titanium Dioxide Films

Characterization of aTiO2 surfaces functionalized with CAP-p15 peptide

Functionalization of Titanium implants using adequate organic molecules is a proposed method to accelerate the osteointegration process, which relates to topographical, chemical, mechanical, and physical features. This study aimed to assess the potential of a peptide derived from cementum attachment protein (CAP-p15) adsorbed onto aTiO2 surfaces to promote the deposition of calcium phosphate (CaP) minerals and its impact on the adhesion and viability of human periodontal ligament cells (hPDLCs). aTiO2 surfaces were synthesized by magnetron sputtering technique. The CAP-p15 peptide was physically attached to aTiO2 surfaces and characterized by atomic force microscopy, fluorescence microscopy, and water contact angle measurement. We performed in vitro calcium phosphate nucleation assays using an artificial saliva solution (pH 7.4) to simulate the oral environment. morphological and chemical characterization of the deposits were evaluated by scanning electronic microscopy (SEM) and spectroscopy molecular techniques (Raman Spectroscopy, ATR-FTIR). The aTiO2 surfaces biofunctionalized with CAP-p15 were also analyzed for hPDLCs attachment, proliferation, and in vitro scratch-healing assay. The results let us see that the homogeneous amorphous titanium oxide coating was 70 nanometers thick. The CAP-p15 (1 μg/mL) displayed the ability to adsorb onto the aTiO2 surface, increasing the roughness and maintaining the hydrophilicity of the aTiO2 surfaces. The physical adsorption of CAP-p15 onto the aTiO2 surfaces promoted the precipitation of a uniform layer of crystals with a flake-like morphology and a Ca/P ratio of 1.79. According to spectroscopy molecular analysis, these crystalline deposits correspond to carbonated hydroxyapatite. Regarding cell behavior, the biofunctionalized aTiO2 surfaces improved the adhesion of hPDLCs after 24 h of cell culture, achieving 3.4-fold when compared to pristine surfaces. Moreover, there was an increase in cell proliferation and cell migration processes. Physical adsorption of CAP-p15 onto aTiO2 surfaces enhanced the formation of carbonate hydroxyapatite crystals and promoted the proliferation and migration of human periodontal ligament-derived cells in in vitro studies. This experimental model using the novel bioactive peptide CAP-p15 could be used as an alternative to increasing the osseointegration process of implants.

Tailoring bisphosphonate-doped titanium films to optimally couple cellular responses and antibacterial activity for biomedical applications

Titanium (Ti) is widely utilized as an implant material; nonetheless, its integration with bone tissue faces limitations due to a patient's comorbidities. To address this challenge, we employed a strategic approach involving the growth of thin films by spin-coating and surface functionalization with etidronate (ETI), alendronate (ALE), and risedronate (RIS). Our methodology involved coating of Ti cp IV disks with thin films of TiO2, hydroxyapatite (HA), and their combinations (1:1 and 1:2 v/v), followed by surface functionalization with ETI, ALE, and RIS. Bisphosphonate-doped films were evaluated in terms of surface morphology and physical-chemical properties by techniques such as electron microscopy, confocal microscopy, and x-ray photoelectron spectroscopy. The antibacterial potential of bisphosphonates alone or functionalized onto the Ti surface was tested against Staphylococcus aureus biofilms. Primary human bone mesenchymal stem cells were used to determine in vitro cell metabolism and mineralization. Although RIS alone did not demonstrate any antibacterial effect as verified by minimum inhibitory concentration assay, when Ti surfaces were functionalized with RIS, partial inhibition of Staphylococcus aureus growth was noted, probably because of the physical-chemical surface properties. Furthermore, samples comprising TiO2/HA (1:1 and 1:2 v/v) showcased an enhancement in the metabolism of nondifferentiated cells and can potentially enhance the differentiation of osteoblastic precursors. All samples demonstrated cell viability higher than 80%. Addition of hydroxyapatite and presence of bisphosphonates increase the metabolic activity and the mineralization of human bone mesenchymal cells. While these findings hold promise, it is necessary to conduct further studies to evaluate the system's performance in vivo and ensure its long-term safety. This research marks a significant stride toward optimizing the efficacy of titanium implants through tailored surface modifications.

Modulation of Cell Response through the Covalent Binding of Fibronectin to Titanium Substrates

Titanium (Ti-6Al-4V) substrates were functionalized through the covalent binding of fibronectin, and the effect of the existence of this extracellular matrix protein on the surface of the material was assessed by employing mesenchymal stem cell (MSC) cultures. The functionalization process comprised the usage of the activation vapor silanization (AVS) technique to deposit a thin film with a high surface density of amine groups on the material, followed by the covalent binding of fibronectin to the amine groups using the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) crosslinking chemistry. The biological effect of the fibronectin on murine MSCs was assessed in vitro. It was found that functionalized samples not only showed enhanced initial cell adhesion compared with bare titanium, but also a three-fold increase in the cell area, reaching values comparable to those found on the polystyrene controls. These results provide compelling evidence of the potential to modulate the response of the organism to an implant through the covalent binding of extracellular matrix proteins on the prosthesis.

Functionalization of Titanium Dioxide by In Situ Surface Crystallization of Bisphosphonate-Based Coordination Complexes

Functionalization of highly pure rutile phase titanium dioxide (TiO2) particles with a selected bisphosphonate-based coordination complex (BPCC), ZOLE-Ca form II, was achieved through in situ surface crystallization. The hydrothermal reaction of the selected BPCC was carried out in the presence of photoactivated rutile phase TiO2 by ultraviolet irradiation. The reaction time was varied to control the crystal growth of the BPCC around the TiO2 core, resulting in a functionalized material with different shell thicknesses: TiO2-core:nano-Ca@ZOLE-shell-† (5 min) and TiO2-core:nano-Ca@ZOLE-shell-‡ (10 min). The crystal phase assessment of the BPCC and the polymorphic phase purity of the metal oxide were determined after immobilization through Raman spectroscopy and powder X-ray diffraction. The results initially suggested that the crystallization of a shell comprising the selected BPCC surrounding a highly pure rutile phase TiO2 core was achieved through controlled in situ surface crystallization. Morphological changes, elemental composition and exact atomic distribution in the functionalized materials were addressed employing scanning electron microscopy coupled with energy-dispersive spectroscopy. These analyses unambiguously confirmed that after 5 min, successful incorporation of a thin BPCC shell on the surface of the metal oxide particles was achieved. Particle size distribution measurements revealed an average particle size of 495 d.nm for the functionalized material after the immobilization process. Quantitative determination of the BPCC shell content in TiO2-core:nano-Ca@ZOLE-shell-† was determined through thermogravimetric analysis, estimating a ratio of ∼1:3 (TiO2:BPCC). The cytotoxicity of TiO2-core:nano-Ca@ZOLE-shell-† against MDA-MB-231 (cancer cell model) and hFOB 1.19 (normal osteoblast-like cell model) cell lines was investigated. The results demonstrated significant cell growth inhibition for TiO2-core:nano-Ca@ZOLE-shell-† against MDA-MB-231, specifically at a concentration of 7.5 μM (% RCL = 46 ± 2%, 72 h). Under the same conditions, the functionalized material did not present cytotoxicity against hFOB 1.19 (% RCL ∼ 100%). These important outcomes provide evidence of the surface crystallization of BPCCs onto rutile phase TiO2 for the development of a novel functionalized material with the potential to treat and prevent osteolytic metastases.

Catalytic degradation of methylene blue by biosynthesized Au nanoparticles on titanium dioxide (Au@TiO2)

The degradation of methylene blue is a critical procedure in its wastewater remediation and thus has inspired wide catalysis research with semiconductors such as titanium dioxide (TiO₂) and rare metals such as gold (Au). In this study, we report bacterial cells assisting biosynthesis for Au@TiO₂ as an efficient catalyst for the catalytic degradation of methylene blue. Multiple complementary characterization for bio-Au_x@TiO₂ evidenced the evenly distributed Au nanoparticles (NPs) on the bio-TiO₂ layers. Meanwhile, bio-Au₂@TiO₂ displayed the superior catalytic activity in the degradation of methylene blue with the highest kinetics constant (k_app) value of 0.195 min^-1. In addition, bio-Au₂@TiO₂ keeps stable catalytic activity for up to 10 cycles. The origin of the catalytic activity was investigated by the hydroxyl radical fluorescence quantitative analysis and optical band gap analysis. In the bio-Au₂@TiO₂ catalytic system, Au NPs decreased the band gap energy of TiO₂ and enabled the generation of abundant photogeneration hydroxyl radicals, resulting in an enhanced photocatalytic activity. Our microbial synthesized bio-TiO₂ and bio-Au_x@TiO₂ study would be useful for developing green synthesis catalyst technology.

Recent trends in Bi-based nanomaterials: challenges, fabrication, enhancement techniques, and environmental applications

One of the most enticing approaches to environmental restoration and energy conversion is photocatalysis powered by solar light. Traditional photocatalysts have limited practical uses due to inadequate light absorption, charge separation, and unknown reaction mechanisms. Discovering new visible-light photocatalysts and investigating their modification is crucial in photocatalysis. Bi-based photocatalytic nanomaterials have gotten much interest as they exhibit distinctive geometric shapes, flexible electronic structures, and good photocatalytic performance under visible light. They can be employed as stand-alone photocatalysts for pollution control and energy production, but they do not have optimum efficacy. As a result, their photocatalytic effectiveness has been significantly improved in the recent decades. Numerous newly created concepts and methodologies have brought significant progress in defining the fundamental features of photocatalysts, upgrading the photocatalytic ability, and understanding essential reactions of the photocatalytic process. This paper provides insights into the characteristics of Bi-based photocatalysts, making them a promising future nanomaterial for environmental remediation. The current review discusses the fabrication techniques and enhancement in Bi-based semiconductor photocatalysts. Various environmental applications, such as H₂ generation and elimination of water pollutants, are also discussed in terms of semiconductor photocatalysis. Future developments will be guided by the uses, issues, and possibilities of Bi-based photocatalysts.

A new technique for incorporation of TiO2 nanotubes on a pre-sintered Y-TZP and its effect on bond strength as compared to conventional air-borne particle abrasion and silicatization TiO2 nanotubes application on pre-sintered Y-TZP

OBJECTIVE

This study evaluated the microshear bond strength of a resin cement to Y-TZP after different methods of TiO₂ nanotubes (nTiO₂) incorporation on pre-sintered Y-TZP surfaces.

METHODS

nTiO₂ were synthesized and incorporated on Y-TZP slices as follows (n = 15): 1) nTiO₂ mixed with isopropyl alcohol/manual application (MAl); 2) nTiO₂ mixed with acetone/manual application (MAc); 3) nTiO₂ mixed with isopropyl alcohol/high-pressure vacuum application (HPVAl); 4) nTiO₂ mixed with acetone/high-pressure vacuum application (HPVAc). As controls, surfaces were sandblasted with Al₂O₃ (OX) or Rocatec silicatization (ROC). All ceramics were sintered after nTiO₂ incorporation. Surface treatments of OX and ROC were made after sintering. Surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Resin composite cylinders (1.40 mm diameter and 1 mm height) were cemented with a resin cement, stored in water at 37 °C for 24 h and thermocycled for 10 000 cycles before microshear bond strength evaluation. Data were analyzed with one-way ANOVA and Games-Howell (α = 0.05), and fracture analysis was performed using a stereomicroscope.

RESULTS

EDS confirmed the presence of TiO₂ on treated Y-TZP. The confocal analysis showed higher roughness for HPVAc and OX. There were significant differences between surface treatments (p < 0.001). HPVAl (22.96 ± 10.3), OX (34.16 ± 7.9) and ROC (27.71 ± 9.4) showed higher microshear bond strengths and were statistically similar (p > 0.05). MAC showed intermediary values, and HPVAc and MAl presented decreased bond strength, with a high percentage of premature debonding.

CONCLUSION

High-pressure vacuum application of nTiO₂ mixed with isopropyl alcohol was able to produce bond strength values compared to conventional air abrasion and Rocatec silicatization.

SIGNIFICANCE

The infiltration of TiO₂ nanostructures on the pre-sintered Y-TZP is an interesting approach that can improve bond strength without the need of sandblasting methods.

Nanostructured Titanium Dioxide Surfaces for Electrochemical Biosensing

TiO2 electrochemical biosensors represent an option for biomolecules recognition associated with diseases, food or environmental contaminants, drug interactions and related topics. The relevance of TiO2 biosensors is due to the high selectivity and sensitivity that can be achieved. The development of electrochemical biosensors based on nanostructured TiO2 surfaces requires knowing the signal extracted from them and its relationship with the properties of the transducer, such as the crystalline phase, the roughness and the morphology of the TiO2 nanostructures. Using relevant literature published in the last decade, an overview of TiO2 based biosensors is here provided. First, the principal fabrication methods of nanostructured TiO2 surfaces are presented and their properties are briefly described. Secondly, the different detection techniques and representative examples of their applications are provided. Finally, the functionalization strategies with biomolecules are discussed. This work could contribute as a reference for the design of electrochemical biosensors based on nanostructured TiO2 surfaces, considering the detection technique and the experimental electrochemical conditions needed for a specific analyte.

Titanium-Based Alloy Surface Modification with TiO2 and Poly(sodium 4-styrenesulfonate) Multilayers for Dental Implants

Implant placement is an important repair method in dentistry and orthopedics. Increasing efforts have focused on optimizing the biocompatibility and osseointegration properties of titanium (Ti) and Ti-based alloys. In this work, Ti-based alloys were modified by the layer-by-layer (LbL) technique, which is a simple and versatile method for surface modification. The morphology and chemical structure of LbL films of poly(sodium 4-styrenesulfonate) (PSS) and Ti dioxide (TiO₂) nanoparticles were first characterized employing ultraviolet-visible and Fourier-transform infrared spectroscopies as well as atomic force microscopy for further application in Ti-based alloy implants. The changes provoked by the LbL PSS/TiO₂ film on the Ti-based alloy surfaces were then investigated by scanning electron microscopy and micro-Raman techniques. Finally, in vivo tests (immunolabeling and biomechanical analysis) performed with screw implants in rats suggested that PSS/TiO₂ multilayers promote changes in both topography and chemical surface properties of the screw, providing beneficial effects for osteoblast activity. This simple and relatively low-cost growth process can open up possibilities to improve dental implants and, probably, bone implants in general.

Outlining cell interaction and inflammatory cytokines on UV-photofunctionalized mixed-phase TiO2 thin film

Photofunctionalization mediated by ultraviolet (UV) light seems to be a promising approach to improve the physico-chemical characteristics and the biological response of titanium (Ti) dental implants. Seeing that photofunctionalization is able to remove carbon from the surface, besides to promote reactions on the titanium dioxide (TiO₂) layer, coating the Ti with a stable TiO₂ film could potentialize the UV effect. Thus, here we determined the impact of UV-photofunctionalized mixed-phase (anatase and rutile) TiO₂ films on the physico-chemical properties of Ti substrate and cell biology. Mixed-phase TiO₂ films were grown by radiofrequency magnetron sputtering on commercially pure titanium (cpTi) discs, and samples were divided as follow: cpTi (negative control), TiO₂ (positive control), cpTi UV, TiO₂ UV (experimental). Photofunctionalization was performed using UVA (360 nm - 40 W) and UVC (250 nm - 40 W) lamps for 48 h. Surfaces were analyzed in terms of morphology, topography, chemical composition, crystalline phase, wettability and surface free energy. Pre-osteoblastic cells (MC3T3E1) were used to assess cell morphology and adhesion, metabolism, mineralization potential and cytokine secretion (IFN-γ, TNF-α, IL-4, IL-6 and IL-17). TiO₂-coated surfaces exhibited granular surface morphology and greater roughness. Photofunctionalization increased wettability (p < 0.05) and surface free energy (p < 0.001) on both surface conditions. TiO₂-treated groups featured normal cell morphology and spreading, and greater cellular metabolic activity at 2 and 4 days (p < 0.05), whereas UV-photofunctionalized surfaces enhanced cell metabolism, cell adhered area, and calcium deposition (day 14) (p < 0.05). In general, assessed proteins were found slightly affected by either UV or TiO₂ treatments. Altogether, our findings suggest that UV-photofunctionalized TiO₂ surface has the potential to improve pre-osteoblastic cell differentiation and the ability of cells to form mineral nodules by modifying Ti physico-chemical properties towards a more stable context. UV-modified surfaces modulate the secretion of key inflammatory markers.

Effect of the addition of functionalized TiO2 nanotubes and nanoparticles on properties of experimental resin composites

OBJECTIVE

To evaluate the influence of the addition of functionalized and non-functionalized TiO₂ nanostructures on properties of a resin composite.

METHODS

TiO₂ nanostructures were synthesized and functionalized, using 3-(aminopropyl)triethoxysilane (APTMS) and 3-(trimethoxysilyl)propyl methacrylate (TSMPM). Characterizations were performed with XRD, EDS, TEM, and TGA. Resin composites containing Bis-GMA/TEGDMA, CQ, DABE, and barium-aluminum silicate glass were produced according to TiO₂ nanostructure (nanotube or nanoparticle), concentration (0.3 or 0.9 wt%), and functionalization (APTMS or TSMPM). The resin composite without nanostructures was used as control. The amount of fillers was kept constant at 78.3 wt% for all materials. The degree of conversion (DC - at 0 h and 24 h), maximum polymerization rate (Rp_max), and Knoop microhardness (KHN before and after ethanol softening) were evaluated. Data were analyzed with two-way ANOVA with repeated measures and Tukey's HSD (α = 0.05).

RESULTS

TGA results demonstrated that functionalizations were effective for both nanostructures. For DC, resin composites, time and interaction effect were significant (p < 0.001). Higher DC was found for 0.3-wt%-functionalized-nanotubes at 24 h. For nanoparticles, only 0.9-wt%-non-functionalized and 0.3-wt%-APTMS-functionalized showed DC similar to the control and all other groups showed higher DC (p < 0.05). Rp_max was higher for 0.3-wt%-APTMS-nanotubes, which corresponded to higher DC after 24 h. The lowest Rp_max occurred for 0.9-wt%-TSMPM-nanotubes, which showed smaller DC at 0 h. For KHN, resin composites, ethanol softening and interaction effect were significant (p < 0.001). KHN decreased after ethanol softening all groups, except for 0.3-wt%-TSMPM-nanotubes, 0.9-wt%-TSMPM-nanotubes, and 0.3-wt%-non-functionalized-nanoparticles.

CONCLUSION

The resin with 0.3-wt%-TSMPM-nanotubes showed higher DC after 24 h, while being the most stable material after the ethanol softening.

SIGNIFICANCE

The addition of functionalized TiO₂ nanostructures in resin-based materials may improve the properties of the material.

Biofunctionalization of titanium surfaces with alendronate and albumin modulates osteoblast performance

BACKGROUND

Biofunctionalization of titanium surfaces can improve host responses, especially considering the time for osteointegration and patient recovery. This prompted us to modify titanium surfaces with alendronate and albumin and to investigate the behavior of osteoblasts on these surfaces.

METHODS

The biofunctionalization of titanium surfaces was characterized using classical physicochemical approaches and later used to challenge pre-osteoblast cells up to 24 h. Then their viability and molecular behavior were investigated using mitochondrial dehydrogenase activity and RTq-PCR technologies, respectively. Potential stimulus of extracellular remodeling was also investigated by zymography.

RESULTS

Our data indicates a differential behavior of cells responding to the surfaces, considering the activity of mitochondrial dehydrogenases. Molecularly, the differential expression of genes related with cell adhesion highlighted the importance of Integrin-β1, Fak, and Src. These 3 genes were significantly decreased in response to titanium surfaces modified with alendronate, but this behavior was reverted when alendronate was associated with albumin. Alendronate-modified surfaces promoted a significant increase on ECM remodeling, as well as culminating with greater gene activity related to the osteogenic phenotype (Runx2, Alp, Bsp).

CONCLUSION

Altogether, our study found interesting osteogenic behavior of cells in response to alendronate and albumin surfaces, which indicates the need for in vivo analyses to better consider these surfaces before clinical trials within the biomedical field.