Engineering High-Resolution Micropatterns Directly onto Titanium with Optimized Contact Guidance to Promote Osteogenic Differentiation and Bone Regeneration

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Abstract

Topographical cues play an important role in directing cell behavior, and thus, extensive research efforts have been devoted to fabrication of surface patterns and exploring the contact guidance effect. However, engineering high-resolution micropatterns directly onto metallic implants remains a grand challenge. Moreover, there still lacks evidence that allows translation of in vitro screening to in vivo tissue response. Herein, we demonstrate a fast, cost-effective, and feasible approach to the precise fabrication of shape- and size-controlled micropatterns on titanium substrates using a combination of photolithography and inductively coupled plasma-based dry etching. A titanium TopoChip containing 34 microgrooved patterns with varying geometry parameters and a flat surface as the control was designed for a high-throughput in vitro study of the contact guidance of osteoblasts. The correlation between the surface pattern dimensions, cell morphological characteristics, proliferation, and osteogenic marker expression was systematically investigated in vitro. Furthermore, the surface with the highest osteogenic potential in vitro along with representative controls was evaluated in rat cranial defect models. The results show that microgrooved pattern parameters have almost no effect on osteoblast proliferation but significantly regulate the cell morphology, orientation, focal adhesion (FA) formation, and osteogenic differentiation in vitro. In particular, a specific groove pattern with a ridge width of 3 μm, groove width of 7 μm, and depth of 2 μm can most effectively align the cells through regulating the distribution of FAs, resulting in an anisotropic actin cytoskeleton, and thereby promoting osteogenic differentiation. In vivo, microcomputed tomography and histological analyses show that the optimized pattern can apparently stimulate new bone formation. This study not only offers a microfabrication method that can be extended to fabricate various shape- and size-controlled micropatterns on titanium alloys but also provides insight into the surface structure design of orthopedic and dental implants for enhanced bone regeneration.

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