Femtosecond Laser-Processing of Pre-Anodized Ti-Based Bone Implants for Cell-Repellent Functionalization

Abstract

Microstructures and nanostructures can be used to reduce the adhesion of the cells on the auxiliary material. Therefore, the aim of our work was to fabricate laser-induced hierarchical microstructures and nanostructures by femtosecond laser-treatment (wavelength 1040 nm, pulse length 350 fs, repetition rates in the kHz range) to reduce the cell adhesion. Additionally, surface chemistry modification by optimized electrochemical anodization was used to further reduce the cell adhesion. For testing, flat plates and bone screws made of Ti-6Al-4V were used. Bone-forming cells (human osteoblasts from the cell line SAOS-2) were grown on the bone implants and additional test samples for two to three weeks. After the growth period, the cells were characterized by scanning electron microscopy (SEM). While earlier experiments with fibroblasts had shown that femtosecond laser-processing followed by electrochemical anodization had a significant impact on cell adhesion reduction, for osteoblasts the same conditions resulted in an activation of the cells with increased production of extracellular matrix material. Significant reduction of cell adhesion for osteoblasts was only obtained at pre-anodized surfaces. It could be demonstrated that this functionalization by means of femtosecond laser-processing can result in bone screws that hinder the adhesion of osteoblasts.

Laser Direct Writing of Dual-Scale 3D Structures for Cell Repelling at High Cellular Density

“…Dual-scale structures for repelling cells have been previously developed. Muck M et al [ 60 ] obtained micro/nanostructured surfaces by the femtosecond laser writing in ASTM F136 Ti-6Al-4V, followed by anodization treatment. This resulted in the obtaining of a modified cell-repellent surface with hundred-nanometer morphological elements.…”

Laser-Induced µ-Rooms for Osteocytes on Implant Surface: An In Vivo Study

“…Within the micro-grid patterns, the cells seemed to be less mobile; they were found to attach to the tops of the bumps with relatively no alignment effects and to spread minimal distances from wherever they first landed. Cells’ guidance for human mesenchymal stem cells (hMSCs) and human osteoblasts has been confirmed in several works [ 29 , 36 , 39 ]. Groove dimensions (depth, width, and period) also affect cells’ guidance [ 45 , 46 ].…”

“…In recent studies on laser surface treatment of materials, it has been shown that the geometric shape of the surface, the size of pattern elements, and surface oxides affect adhesion [ 36 , 37 , 38 ], orientation angle [ 29 , 39 , 40 ], and differentiation and proliferation [ 37 , 41 , 42 , 43 , 44 ] of various types of cells. For example, it was shown during experiments on human osteosarcoma (HOS) cells [ 40 ] that a polished surface and a rough surface with non-periodic relief contribute to random orientation of cells, and it was found that cell spreading decreases with the increase of surface roughness.…”

Fabrication of Biomimetic 2D Nanostructures through Irradiation of Stainless Steel Surfaces with Double Femtosecond Pulses

“…Given the capability to fabricate an abundance of patterns of enhanced complexity, laser induced topographies have been broadly used as platforms to control cell behavior, as the fabrication of nano-scale patterns can differentially influence cellular adhesion and proliferation. Commonly used metallic implant materials include Ti and Ti-based alloys, which have been extensively explored [27][28][29][30] and stainless steel, which has yet to be fully investigated [31,32]. Ti is relatively well integrated into medical applications, while stainless steel can still display biocompatibility issues, mainly related to infections and osseointegration.…”

“…However, as the two materials offer different mechanical properties, they are constantly being assessed for applications in different anatomic locations. Results in previous studies indicate that by fabricating different surface structures on metal surfaces, cellular adhesion and morphology can be tailored; however, this functionality is dependent on the types of cells used for testing [30].…”