TiO2 Nanotopography-Driven Osteoblast Adhesion through Coulomb's Force Evolution

Synergistic Amelioration of Osseointegration and Osteoimmunomodulation with a Microarc Oxidation-Treated Three-Dimensionally Printed Ti-24Nb-4Zr-8Sn Scaffold via Surface Activity and Low Elastic Modulus

Biomaterial scaffolds, including bone substitutes, have evolved from being primarily a biologically passive structural element to one in which material properties such as surface topography and chemistry actively direct bone regeneration by influencing stem cells and the immune microenvironment. Ti-6Al-4V(Ti6Al4V) implants, with a significantly higher elastic modulus than human bone, may lead to stress shielding, necessitating improved stability at the bone-titanium alloy implant interface. Ti-24Nb-4Zr-8Sn (Ti2448), a low elastic modulus β-type titanium alloy devoid of potentially toxic elements, was utilized in this study. We employed 3D printing technology to fabricate a porous scaffold structure to further decrease the structural stiffness of the implant to approximate that of cancellous bone. Microarc oxidation (MAO) surface modification technology is then employed to create a microporous structure and a hydrophilic oxide ceramic layer on the surface and interior of the scaffold. In vitro studies demonstrated that MAO treatment enhances the proliferation, adhesion, and osteogenesis capabilities on the scaffold surface. The chemical composition of the MAO-Ti2448 oxide layer is found to enhance the transcription and expression of osteogenic genes in bone mesenchymal stem cells (BMSCs), potentially related to the enrichment of Nb2O5 and SnO2 in the oxide layer. The MAO-Ti2448 scaffold, with its synergistic surface activity and low stiffness, significantly activates the anti-inflammatory macrophage phenotype, creating an immune microenvironment that promotes the osteogenic differentiation of BMSCs. In vivo experiments in a rabbit model demonstrated a significant improvement in the quantity and quality of the newly formed bone trabeculae within the scaffold under the contact osteogenesis pattern with a matched elastic modulus. These trabeculae exhibit robust connections to the external structure of the scaffold, accelerating the formation of an interlocking structure between the bone and implant and providing higher implantation stability. These findings suggest that the MAO-Ti2448 scaffold has significant potential as a bone defect repair material by regulating osteoimmunomodulation and osteogenesis to enhance osseointegration. This study demonstrates an optional strategy that combines the mechanism of reducing the elastic modulus with surface modification treatment, thereby extending the application scope of β-type titanium alloy.

Theoretical modeling approach for adsorption of fibronectin on the nanotopographical implants

The success of orthopedic implants depends on the sufficient integration between tissue and implant, which is influenced by the cellular responses to their microenvironment. The conformation of adsorbed extracellular matrix is crucial for cellular behavior instruction via manipulating the physiochemical features of materials. To investigate the electrostatic adsorption mechanism of fibronectin on nanotopographies, a theoretical model was established to determine surface charge density and Coulomb's force of nanotopography - fibronectin interactions using a Laplace equation satisfying the boundary conditions. Surface charge density distribution of nanotopographies with multiple random fibronectin was simulated based on random number and Monte Carlo hypothesis. The surface charge density on the nanotopographies was compared to the experimental measurements, to verify the effectiveness of the theoretical model. The model was implemented to calculate the Coulomb force generated by nanotopographies to compare the fibronectin adsorption. This model has revealed the multiple random quantitative fibronectin electrostatic adsorption to the nanotopographies, which is beneficial for orthopedic implant surface design.Significance: The conformation and distribution of adsorbed extracellular matrix on biomedical implants are crucial for directing cellular behaviors. However, the Ti nanotopography-ECM interaction mechanism remains largely unknown. This is mostly because of the interactions that are driven by electrostatic force, and any experimental probe could interfere with the electric field between the charged protein and Ti surface. A theoretical model is hereby proposed to simulate the adsorption between nanotopographies and fibronectin. Random number and Monte Carlo hypothesis were applied for multiple random fibronectin simulation, and the Coulomb's force between nanoconvex and nanoconcave structures was comparatively analyzed.

Promoted Abutment-Soft Tissue Integration Around Self-Glazed Zirconia Surfaces with Nanotopography Fabricated by Additive 3D Gel Deposition

Introduction

Improving the biological sealing around dental abutments could promote the long-term success of implants. Although titanium abutments have a wide range of clinical applications, they incur esthetic risks due to their color, especially in the esthetic zone. Currently, zirconia has been applied as an esthetic alternative material for implant abutments; however, zirconia is purported to be an inert biomaterial. How to improve the biological activities of zirconia has thus become a popular research topic. In this study, we presented a novel self-glazed zirconia (SZ) surface with nanotopography fabricated by additive 3D gel deposition and investigated its soft tissue integration capability compared to that of clinically used titanium and polished conventional zirconia surfaces.

Materials and Methods

Three groups of disc samples were prepared for in vitro study and the three groups of abutment samples were prepared for in vivo study. The surface topography, roughness, wettability and chemical composition of the samples were examined. Moreover, we analyzed the effect of the three groups of samples on protein adsorption and on the biological behavior of human gingival keratinocytes (HGKs) and human gingival fibroblasts (HGFs). Furthermore, we conducted an in vivo study in which the bilateral mandibular anterior teeth of rabbits were extracted and replaced with implants and corresponding abutments.

Results

The surface of SZ showed a unique nanotopography with nm range roughness and a greater ability to absorb protein. The promoted expression of adhesion molecules in both HGKs and HGFs was observed on the SZ surface compared to the surfaces of Ti and PCZ, while the cell viability and proliferation of HGKs and the number of HGFs adhesion were not significant among all groups. In vivo results showed that the SZ abutment formed strong biological sealing at the abutment-soft tissue interface and exhibited markedly more hemidesmosomes when observed with a transmission electron microscope.

Conclusion

These results demonstrated that the novel SZ surface with nanotopography promoted soft tissue integration, suggesting its promising application as a zirconia surface for the dental abutment.

Construction of a Localized and Long-Acting CCN2 Delivery System on Percutaneous Ti Implant Surfaces for Enhanced Soft-Tissue Integration

Soft-tissue integration (STI) plays an essential role in the long-term success of percutaneous Ti implants since it acts as a biological barrier that protects the soft and hard tissue around implants. Surface modification of Ti implants with drug-release properties to achieve soft-tissue regeneration has been proven to be effective in STI. However, the short-acting effect caused by the uncontrolled drug release of the topical delivery system limits long-term STI enhancement. Herein, a long-acting protein delivery system for Ti implants that involved micro-arc oxidation of Ti surfaces (MAO-Ti) and localized immobilization of cellular communication network factor 2 (CCN2) bearing mesoporous silica nanoparticles (MSNs) on MAO-Ti was prepared, namely, CCN2@MSNs-Ti. The CCN2 release study of CCN2@MSNs-Ti demonstrated a sustained-release profile for 21 days, which was able to maintain long-term stable STI. In addition, in vitro cell behavior evaluation results indicated that CCN2@MSNs-Ti could promote the STI-related biological response of human dermal fibroblasts via the FAK-MAPK pathway. More importantly, the system could effectively enhance STI after 4 weeks and proinflammatory factors in the soft tissue decreased significantly in a rat model of implantation. These results denote that CCN2@MSNs-Ti showed an appealing application prospect for enhanced STI around transcutaneous Ti implants, which would ultimately result in an increased success rate of percutaneous Ti implants.