A spatially varying charge model for regulating site-selective protein adsorption and cell behaviors

Surface characteristics and in vitro biocompatibility of titanium preserved in a vitamin C-containing saline storage solution

The purpose of this study is to explore a storage solution for titanium implants and investigate its osteogenic properties. The commercial pure titanium (cp-Ti) surface and double-etched (SLA) titanium surface specimens were preserved in air, saline, 10 mM Vitamin C (VitC)-containing saline and 100 mM VitC-containing saline storage solutions for 2 weeks. The surface microtopography of titanium was observed by scanning electron microscopy (SEM), the surface elemental compositions of the specimens were analyzed by Raman and X-ray photoelectron spectroscopy (XPS), and water contact angle and surface roughness of the specimens were tested. The protein adsorption capacity of two titanium surfaces after storage in different media was examined by BCA kit. The MC3T3-E1 osteoblasts were cultured on two titanium surfaces after storage in different media, and the proliferation, adhesion and osteogenic differentiation activity of osteoblasts were detected by CCK-8, laser confocal microscope (CLSM) and Western blot. The SEM results indicated that the titanium surfaces of the air group were relatively clean while scattered sodium chloride or VitC crystals were seen on the titanium surfaces of the other three groups. There were no significant differences in the micromorphology of the titanium surfaces among the four groups. Raman spectroscopy detected VitC crystals on the titanium surfaces of two experimental groups. The XPS, water contact angle and surface roughness results suggested that cp-Ti and SLA-Ti stored in 0.9% NaCl and two VitC-containing saline storage solutions possessed less carbon contamination and higher surface hydrophilicity. Moreover, the protein adsorption potentials of cp-Ti and SLA-Ti surfaces were significantly improved under preservation in two VitC-containing saline storage solutions. The results of in vitro study showed that the preservation of two titanium surfaces in 100 mM VitC-containing saline storage solution upregulated the cell adhesion, proliferation, osteogenic related protein expressions of MC3T3-E1 osteoblasts. In conclusion, preservation of cp-Ti and SLA-Ti in 100 mM VitC-containing saline storage solution could effectively reduce carbon contamination and enhance surface hydrophilicity, which was conducive to osteogenic differentiation of osteoblasts.

Electrostatic Analysis of Bioactivity of Ti-6Al-4V Hydrophilic Surface with Laser Textured Micro-Square Convexes

At solid-liquid interfaces, charged particles within the electric double layer (EDL) are acted on by the electrostatic force, which may affect cell absorption and surface wettability. In this study, a model of the electrostatic force and surface tension of textured surfaces was presented. Then, the growth and adhesion of Murine osteoblasts (MC3T3-E1) cells on laser-ablated micro-square-textured Ti-6Al-4V surfaces were studied to demonstrate the use of a laser-processed texture to effectively improve bioactivity. Three different micro-square-textured hydrophilic surfaces, presenting lower contact angles of 19°, 22.5°, and 31.75° compared with that of a smooth surface (56.5°), were fabricated using a fiber-optic laser. Cellular morphology and initial cell attachment were analyzed by field emission scanning electron microscopy (SEM) and fluorescence microscopy, respectively. The results show that the electrostatic force not only made the textured surface more hydrophilic but also made the cells tend to adhere to the edges and corners of the protruding convexes. Cell morphology analysis also showed that cells would prefer to grow at the edges and corners of each micro-square convex protrusion. The laser-treated surfaces were more conducive to rapid cell growth and adhesion, and cells were preferentially attached on the hydrophilic-textured surfaces. Electrostatic force may be an important factor in effectively improving the bioactivity of Ti-6Al-4V surfaces, and the presence of more surface grooves would be more conducive to improving the bioactivity of cells.

Nanostructured Titanium Implant Surface Facilitating Osseointegration from Protein Adsorption to Osteogenesis: The Example of TiO2 NTAs

Titanium implants have been widely applied in dentistry and orthopedics due to their biocompatibility and resistance to mechanical fatigue. TiO₂ nanotube arrays (TiO₂ NTAs) on titanium implant surfaces have exhibited excellent biocompatibility, bioactivity, and adjustability, which can significantly promote osseointegration and participate in its entire path. In this review, to give a comprehensive understanding of the osseointegration process, four stages have been divided according to pivotal biological processes, including protein adsorption, inflammatory cell adhesion/inflammatory response, additional relevant cell adhesion and angiogenesis/osteogenesis. The impact of TiO₂ NTAs on osseointegration is clarified in detail from the four stages. The nanotubular layer can manipulate the quantity, the species and the conformation of adsorbed protein. For inflammatory cells adhesion and inflammatory response, TiO₂ NTAs improve macrophage adhesion on the surface and induce M2-polarization. TiO₂ NTAs also facilitate the repairment-related cells adhesion and filopodia formation for additional relevant cells adhesion. In the angiogenesis and osteogenesis stage, TiO₂ NTAs show the ability to induce osteogenic differentiation and the potential for blood vessel formation. In the end, we propose the multi-dimensional regulation of TiO₂ NTAs on titanium implants to achieve highly efficient manipulation of osseointegration, which may provide views on the rational design and development of titanium implants.

Biomedical Implants with Charge-Transfer Monitoring and Regulating Abilities

Transmembrane charge (ion/electron) transfer is essential for maintaining cellular homeostasis and is involved in many biological processes, from protein synthesis to embryonic development in organisms. Designing implant devices that can detect or regulate cellular transmembrane charge transfer is expected to sense and modulate the behaviors of host cells and tissues. Thus, charge transfer can be regarded as a bridge connecting living systems and human-made implantable devices. This review describes the mode and mechanism of charge transfer between organisms and nonliving materials, and summarizes the strategies to endow implants with charge-transfer regulating or monitoring abilities. Furthermore, three major charge-transfer controlling systems, including wired, self-activated, and stimuli-responsive biomedical implants, as well as the design principles and pivotal materials are systematically elaborated. The clinical challenges and the prospects for future development of these implant devices are also discussed.

Influence of the second phase on protein adsorption on biodegradable Mg alloys' surfaces: Comparative experimental and molecular dynamics simulation studies

The effect of the second phase on the mechanical properties and corrosion resistance of Mg alloys has been systematically studied. However, there is limited information on the effect of the second phase on protein adsorption behavior. In the present study, the effect of the second phase on protein adsorption on the surfaces of biodegradable Mg alloys was investigated using experimental methods and molecular dynamics (MD) simulations. The experimental results showed that the effect of the second phase on fibrinogen adsorption was type-dependent. Fibrinogen preferentially adsorbed on Y-, Ce-, or Nd-involved second phases, while the second phase containing Zn inhibited its adsorption. MD simulations revealed the mechanism of the second phase that influenced protein adsorption in terms of charge distribution, surface-protein interaction energy, and water molecule distribution. Our studies proposed a deep understanding of the design of Mg-based biomaterials with superior biocompatibility. STATEMENT OF SIGNIFICANCE: Mechanical properties, uniform degradation, and biocompatibility must be considered while designing biomedical Mg alloys. To improve the mechanical properties and corrosion resistance of Mg alloys, the second phase is usually required. However, the effects of the second phase on biocompatibility of Mg alloys have been rarely reported. Here, the influence of the second phase on protein adsorption was experimentally studied by designing Mg alloys with different types of second phase. The first principle calculation and MD simulation were used to reveal the mechanism by which the second phase influences protein adsorption. This work could be used to better elucidate the protein adsorption mechanisms and design principles to improve the biocompatibility of Mg alloys.

Wireless Electrochemotherapy by Selenium-Doped Piezoelectric Biomaterials to Enhance Cancer Cell Apoptosis

Cancer residues around the surgical site remain a significant cause of treatment failure with cancer recurrence. To prevent cancer recurrence and simultaneously repair surgery-caused defects, it is urgent to develop implantable biomaterials with anticancer ability and good biological activity. In this work, a functionalized implant is successfully fabricated by doping the effective anticancer element selenium (Se) into the potassium-sodium niobate piezoceramic, which realizes the wireless combination of electrotherapy and chemotherapy. Herein, we demonstrate that the Se-doped piezoelectric implant can cause mitochondrial damage by increasing intracellular reactive oxygen species levels and then trigger the caspase-3 pathway to significantly promote apoptosis of osteosarcoma cells in vitro. Meanwhile, its good biocompatibility has been verified. These results are of great importance for future deployment of wireless electro- and chemostimulation to modulate biological process around the defective tissue.

Is selective protein adsorption on biomaterials a viable option to promote periodontal regeneration?

Periodontitis is an inflammatory condition that can induce significant destruction of the periodontium, the set of specialized tissues that provide nourishment and support to the teeth. According to the guided tissue regeneration principles, the periodontium can be regenerated if the spatiotemporal control of wound healing is obtained, namely the tune control of cell response. After material implantation, protein adsorption at the interface is the first occurring biological event, which influences subsequent cell response. With the regard of this, we hypothesize that the control of selective adsorption of biological cues from the surrounding milieu may be a key-point to control selective cell colonization of scaffolds for periodontal tissue regeneration.