Long-term clinical study and multiscale analysis of in vivo biodegradation mechanism of Mg alloy.

There has been a tremendous amount of research in the past decade to optimize the mechanical properties and degradation behavior of the biodegradable Mg alloy for orthopedic implant. Despite the feasibility of degrading implant, the lack of fundamental understanding about biocompatibility and underlying bone formation mechanism is currently limiting the use in clinical applications. Herein, we report the result of long-term clinical study and systematic investigation of bone formation mechanism of the biodegradable Mg-5wt%Ca-1wt%Zn alloy implant through simultaneous observation of changes in element composition and crystallinity within degrading interface at hierarchical levels. Controlled degradation of Mg-5wt%Ca-1wt%Zn alloy results in the formation of biomimicking calcification matrix at the degrading interface to initiate the bone formation process. This process facilitates early bone healing and allows the complete replacement of biodegradable Mg implant by the new bone within 1 y of implantation, as demonstrated in 53 cases of successful long-term clinical study.

Crystallographic orientation of the c-axis of biological apatite as a new index of the quality of subchondral bone in knee joint osteoarthritis.

The aim of the present study was to investigate the preferred orientation of biological apatite (BAp) as a new index of the quality of subchondral bone (SB) in knee joint osteoarthritis (OA). Ten OA and five normal knee joints were obtained. Thickness, quantity and bone mineral density (BMD) of SB were analyzed at the medial condyle of the femur in dry conditions by peripheral quantitative computed tomography. In addition, the preferred crystallographic orientation of the c-axis of BAp was evaluated as bone quality parameter using a microbeam X-ray diffractometer technique. BMD and thickness of SB were significantly increased in OA specimens compared to normal knee specimens (P < 0.01), and the preferred orientation of the c-axis of BAp along the normal direction of SB surface was significantly higher in OA specimens (P < 0.01), reflecting the change in stress of concentration in the pathological portion without cartilage. SB sclerosis in OA results in both proliferation of bone tissues and enhanced degree of preferential alignment of the c-axis of BAp. Our findings could have major implications for the diagnosis of clinical studies, including pathologic elucidation in OA.

Magnesium Corrosion Triggered Spontaneous Generation of H2O2 on Oxidized Titanium for Promoting Angiogenesis.

Although the use of reactive oxygen species (ROS) has been extensively studied, current systems employ external stimuli such as light or electrical energy to produce ROS, which limits their practical usage. In this report, biocompatible metals were used to construct a novel electrochemical system that can spontaneously generate H2O2 without any external light or voltage. The corrosion of Mg transfers electrons to Au-decorated oxidized Ti in an energetically favorable process, and the spontaneous generation of H2O2 in an oxygen reduction reaction was revealed to occur at titanium by combined spectroscopic and electrochemical analyses. The controlled release of H2O2 noticeably enhanced in vitro angiogenesis even in the absence of growth factors. Finally, a new titanium implant prototype was developed by Mg incorporation, and its potential for promoting angiogenesis was demonstrated.

Co-deteriorations of anisotropic extracellular matrix arrangement and intrinsic mechanical property in c-src deficient osteopetrotic mouse femur.

Osteopetrotic bone shows dissociation between bone mineral density (BMD) and bone strength. In this study, volumetric BMD; preferential orientation of the extracellular matrix (ECM), which is composed of collagen fibers and apatite crystals as bone material quality; and mechanical properties of the src-/- osteopetrotic and normal mouse femoral cortical bone were analyzed and compared with each other at a bone tissue level. The degree of preferential orientation of ECM along the femoral long axis was significantly decreased in the src-/- mice femur, suggesting deteriorated bone quality. Young's modulus, as a tissue-level mechanical property analyzed by nano-indentation technique along the long bone direction, also was decreased in the src-/- mice cortical femur, in spite of the similar volumetric cortical BMD. To the best of our knowledge, this is the first report to demonstrate the synchronous deterioration of Young's modulus and anisotropic ECM organization in the src-/- osteopetrotic mouse bone. These results indicate that the deterioration of the preferential ECM orientation is one major cause of the impaired mechanical property in the src-/- mouse bone.

Erratum: Direct and accurate measurement of size dependent wetting behaviors for sessile water droplets.

This corrects the article DOI: 10.1038/srep18150.

Comprehensive study on the roles of released ions from biodegradable Mg-5 wt% Ca-1 wt% Zn alloy in bone regeneration.

We report here the effect of micro-environmental changes from biodegradable magnesium alloys on the activities of cells - osteoblasts, osteoclasts and macrophages - which play critical roles in each phase of the bone-regeneration process. Despite positive bone formation effects from several in vivo studies, minimal progress has been made in identifying underlying mechanisms through in vitro studies, which are currently concentrated on osteoblastic activities. The observed in vitro and in vivo results indicated that alkaline pH and released magnesium and zinc ions derived from Mg-5 wt% Ca-1 wt% Zn alloy biodegradation promote the progress of bone formation. In contrast, alkaline pH and magnesium ions remarkably suppressed osteoclastic activities and pro-inflammatory cytokine production, closely related to osteolysis and prosthesis failure. Findings from the present study conclude that the degradation of Mg-5 wt% Ca-1 wt% Zn alloys can promote new bone formation by simultaneously affecting the complex combination of variable cellular activities and phases. Copyright © 2016 John Wiley & Sons, Ltd.

Induction of Biological Apatite Orientation as a Bone Quality Parameter in Bone Regeneration Using Hydroxyapatite/Poly ɛ-Caprolactone Composite Scaffolds.

Changes in the biological apatite (BAp) c-axis orientation were investigated as a bone quality parameter in bone regeneration using hydroxyapatite/poly ɛ-caprolactone (HA/PCL) composite scaffolds. Three-dimensional (3D) HA/PCL composite scaffolds were fabricated using a layer manufacturing process in three grid sizes (200-, 600-, and 1000 µm) and grafted into the forearm ulna of New Zealand white rabbits. The cross-sectional areas of the bones regenerated from the scaffolds with 600- and 1000-µm grid sizes were significantly larger than those from the scaffold with 200-µm grid sizes, whereas bone mineral density in the regenerated regions did not differ between the three grid sizes. Moreover, the BAp c-axis orientation in the bones regenerated from the scaffolds with grid sizes of 600- and 1000 µm was not significantly different; however, both scaffolds showed enhanced BAp orientation, although the degree of BAp orientation was lower than that in intact bones. In conclusion, HA/PCL composite 3D scaffolds with 600- and 1000-µm grid sizes induced BAp c-axis orientation and showed good bone regeneration behavior in vivo.

Detecting changes in arthritic fibroblast-like synoviocytes using atomic force microscopy.

The morphological and quantitative differences between arthritic fibroblast-like synoviocytes (FLS) and normal FLS were determined as an effective diagnostic tool for rheumatoid arthritis (RA), and confirmed using atomic force microscopy (AFM). Collagen-induced arthritic (CIA) mice and normal mice were prepared and FLS were isolated by enzymatic digestion from the synovial tissue of sacrificed mice at 5-week and 8-week pathogenesis periods. Analysis of cell morphology using AFM revealed that the surface roughness around the nucleus and around the branched cytoplasm was significantly higher in CIA FLS (P < 0.05) than that in normal FLS. In addition, the roughness of two different sites on the arthritic FLS increased with an increase in the duration of pathogenesis. These results strongly suggest that AFM can be widely used as a diagnostic tool in cytopathology to detect the early signs of RA and various others diseases at the intercellular level.

Direct and accurate measurement of size dependent wetting behaviors for sessile water droplets.

The size-dependent wettability of sessile water droplets is an important matter in wetting science. Although extensive studies have explored this problem, it has been difficult to obtain empirical data for microscale sessile droplets at a wide range of diameters because of the flaws resulting from evaporation and insufficient imaging resolution. Herein, we present the size-dependent quantitative change of wettability by directly visualizing the three phase interfaces of droplets using a cryogenic-focused ion beam milling and SEM-imaging technique. With the fundamental understanding of the formation pathway, evaporation, freezing, and contact angle hysteresis for sessile droplets, microdroplets with diameters spanning more than three orders of magnitude on various metal substrates were examined. Wetting nature can gradually change from hydrophobic at the hundreds-of-microns scale to super-hydrophobic at the sub-µm scale, and a nonlinear relationship between the cosine of the contact angle and contact line curvature in microscale water droplets was demonstrated. We also showed that the wettability could be further tuned in a size-dependent manner by introducing regular heterogeneities to the substrate.