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"Biomedical materials"
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Instructing cells with programmable peptide DNA hybrids
The native extracellular matrix is a space in which signals can be displayed dynamically and reversibly, positioned with nanoscale precision, and combined synergistically to control cell function. Here we describe a molecular system that can be programmed to control these three characteristics. In this approach we immobilize peptide-DNA (P-DNA) molecules on a surface through complementary DNA tethers directing cells to adhere and spread reversibly over multiple cycles. The DNA can also serve as a molecular ruler to control the distance-dependent synergy between two peptides. Finally, we use two orthogonal DNA handles to regulate two different bioactive signals, with the ability to independently up- or downregulate each over time. This enabled us to discover that neural stem cells, derived from the murine spinal cord and organized as neurospheres, can be triggered to migrate out in response to an exogenous signal but then regroup into a neurosphere as the signal is removed.
The extracellular matrix can affect cell behaviour both physically and biochemically. Here, the authors developed a substrate that is based on peptides and nucleic acids hybrids that can dynamically present signals upon demand which regulate cell adhesion and migration, thereby controlling cell organisation.
Journal Article
Gas formation and biological effects of biodegradable magnesium in a preclinical and clinical observation
Magnesium alloys are biodegradable metals receiving increasing attention, but the clinical applications of these materials are delayed by concerns over the rapid corrosion rate and gas formation. Unlike corrosion, which weakens mechanical properties, the gas formation issue has received little attention. Therefore, we evaluated the gas formation and biological effects for Mg implants through preclinical (immersed in Earle's balanced salt solution and in vivo) and clinical studies. The immersion test examined the gas volume and composition. The in vivo study also examined gas volume and histological analysis. The clinical study examined the gas volume and safety after Mg screw metatarsal fixation. Gas was mainly composed of H
2
, CO and CO
2
. Maximum volumes of gas formed after 5 days for in vivo and 7 days in clinical study. Within the clinical examination, two superficial wound complications healed with local wound care. Osteolytic lesions in the surrounding metaphysis of the Mg screw insertion developed in all cases and union occurred at 3 months. Mg implants released gas with variable volumes and composition (H
2
, CO, and CO
2
), with no long-term toxic effects on the surrounding tissue. The implants enabled bone healing, although complications of wound breakdown and osteolytic lesions developed.
Journal Article
Three dimensional printed macroporous polylactic acid/hydroxyapatite composite scaffolds for promoting bone formation in a critical-size rat calvarial defect model
We have explored the applicability of printed scaffold by comparing osteogenic ability and biodegradation property of three resorbable biomaterials. A polylactic acid/hydroxyapatite (PLA/HA) composite with a pore size of 500 μm and 60% porosity was fabricated by three-dimensional printing. Three-dimensional printed PLA/HA, β-tricalcium phosphate (β-TCP) and partially demineralized bone matrix (DBM) seeded with bone marrow stromal cells (BMSCs) were evaluated by cell adhesion, proliferation, alkaline phosphatase activity and osteogenic gene expression of osteopontin (OPN) and collagen type I (COL-1). Moreover, the biocompatibility, bone repairing capacity and degradation in three different bone substitute materials were estimated using a critical-size rat calvarial defect model in vivo. The defects were evaluated by micro-computed tomography and histological analysis at four and eight weeks after surgery, respectively. The results showed that each of the studied scaffolds had its own specific merits and drawbacks. Three-dimensional printed PLA/HA scaffolds possessed good biocompatibility and stimulated BMSC cell proliferation and differentiation to osteogenic cells. The outcomes in vivo revealed that 3D printed PLA/HA scaffolds had good osteogenic capability and biodegradation activity with no difference in inflammation reaction. Therefore, 3D printed PLA/HA scaffolds have potential applications in bone tissue engineering and may be used as graft substitutes in reconstructive surgery.
Journal Article
3D printed porous β-Ca2SiO4 scaffolds derived from preceramic resin and their physicochemical and biological properties
Silicate bioceramic scaffolds are of great interest in bone tissue engineering, but the fabrication of silicate bioceramic scaffolds with complex geometries is still challenging. In this study, three-dimensional (3D) porous β-Ca
2
SiO
4
scaffolds have been successfully fabricated from preceramic resin loaded with CaCO
3
active filler by 3D printing. The fabricated β-Ca
2
SiO
4
scaffolds had uniform interconnected macropores (ca. 400 μm), high porosity (>78%), enhanced mechanical strength (ca. 5.2 MPa), and excellent apatite mineralization ability. Importantly, the results showed that the increase of sintering temperature significantly enhanced the compressive strength and the scaffolds sintered at higher sintering temperature stimulated the adhesion, proliferation, alkaline phosphatase activity, and osteogenic-related gene expression of rat bone mesenchymal stem cells. Therefore, the 3D printed β-Ca
2
SiO
4
scaffolds derived from preceramic resin and CaCO
3
active fillers would be promising candidates for bone tissue engineering.
Journal Article
Tribology and sustainability
\"This book brings a vision of promoting greener, cleaner, and eco-friendly environment highlighting sustainable solutions in tribology via development of self-lubricating materials, green additives in lubricants, natural fiber reinforced materials and biomimetic approaches. Backed by supporting schematic diagrams, data tables and illustrations for easy understanding, it focusses on the recent advancements in tribology and sustainability. Global sustainability and regional requirements are addressed through chapters on natural composites, green lubricants, biomedical and wind energy systems with a dedicated chapter on Global Sustainability Scenario. Features: Highlights sustainability via new tribological approaches and how such methods are essential. Covers theoretical aspects of various tribological topics concerning mechanical and material designs for energy-efficient systems. Includes practical global sustainability based on the regional requirement of tribological research and sustainable impact. Reviews tribology of green lubricants, green additives, and lightweight materials. Discusses topics related to biomimetics and bio-tribology. This book aims at researchers, professionals and graduate students in Tribology, Surface Engineering, Mechanical Design, Materials Engineering, including Mechanical, Aerospace, Chemical and Environmental Engineering\"-- Provided by publisher.
Book
Biocompatibility of titanium from the viewpoint of its surface
Among metals, Ti and majority of its alloys exhibit excellent biocompatibility or tissue compatibility. Although their high corrosion resistance is a factor in the biocompatibility of Ti and Ti alloys, it is clear that other factors exist. In this review, the corrosion resistance and passive film of Ti are compared to those of other metallic biomaterials, and their band gap energies, E
g
s, are compared to discuss the role of E
g
in the reactivity with living tissues. From the perspective of the material's surface, it is possible to explain the excellent biocompatibility of Ti by considering the following factors: Ti ions are immediately stabilized not to show toxicity if it is released to body fluids; good balance of positive and negative charges by the dissociation of surface hydroxyl groups on the passive film; low electrostatic force of the passive film inducing a natural adsorption of proteins maintaining their natural conformation; strong property as n-type semiconductor; lower band gap energy of the passive film on Ti generating optimal reactivity; and calcium phosphate formation is caused by this reactivity. The results suggest that due to the passive oxide film, the optimal balance between high corrosion resistance and appropriate reactivity of Ti is the predominate solution for the excellent biocompatibility of Ti.
Journal Article