Visualizing bone mineralization and collagen fibril organization at intermediate scales between the nanometer and the hundreds of microns range, is still an important challenge. Similarly, visualizing cellular components which locally affect the tissue structure requires a precision of a few tens of nanometers at maximum while spanning several tens of micrometers. In the last decade, gallium focused ion beam (FIB) equipped with a scanning electron microscope (SEM) proved to be an extremely valuable structural tool to meet those ends. In this study, we assess the capability of a recent plasma FIB-SEM technology which provides up to 50x increase in measurement speed over gallium FIB-SEM, thus paving the way to larger volume analysis. Nanometer-scale layers of demineralized and mineralized unstained human femoral lamellar bone were sequentially sectioned over volumes of 6-16,000 μm 3. Analysis of mineralized tissue revealed prolate ellipsoidal mineral clusters measuring approximately 1.1 µm in length by 700 nm at their maximum diameter. Those features, suggested by others in high resolution studies, appear here as a ubiquitous motif in mineralized lamellar bone over thousands of microns cubed, suggesting a heterogeneous and yet regular pattern of mineral deposition past the single collagen fibril level. This large scale view retained sufficient resolution to visualize the collagen fibrils while also partly visualizing the lacuno-canalicular network in three-dimensions. These findings are strong evidence for suitability of PFIB as a bone analysis tool and the need to revisit bone mineralization over multi-length scales with mineralized tissue.

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Development of coatings with tailored surface properties that enhance bone growth is crucial to enhancing the life span of load bearing implants. Bioactive ceramic–polysaccharide hydrogel composite materials are attractive for this application due to their chemical similarity to human bone at the nanoscale. Equally important is the creation of advanced coating processing techniques that can be easily upscaled for mass manufacturing. Toward this aim, we developed an electrochemical fabrication technique for the simple and rapid processing of composite pectin hydrogels. This technique used polygalacturonic acid (PGA) combined with anodic electrophoretic deposition (EPD) to fabricate composite hydrogels, which contained bioactive particles such as TiO2, hydroxyapatite, and bioactive glass. Another key finding was the ability of PGA to facilitate rapid fabrication of antibacterial coatings for infection prevention using the antibiotic tetracycline. We proposed a mechanism of deposition and proved our hypothesis using Fourier transform infrared spectroscopy. To evaluate the suitability of our coatings for bone tissue repair, comprehensive surface characterization was conducted, including scanning electron microscopy, X-ray diffraction, water contact angle measurements, and cell metabolism assays. Surface characterization results revealed that our PGA composite films exhibit a desirable combination of surface chemistry and morphology, which was achieved in one processing step. Furthermore, PGA hydrogel coatings supported cell adhesion and proliferation, demonstrating that our technique is an attractive strategy for rapid surface modification of metallic implants.