3D bioactive composite scaffolds for bone tissue engineering.

One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.

On the Mechanistic Origins of Toughness in Bone

The Guided Bone Regeneration (GBR) treatment concept advocates that regeneration of osseous defects is predictably attainable via the application of occlusive membranes, which mechanically exclude non-osteogenic cell populations from the surrounding soft tissues, thereby allowing osteogenic cell populations originating from the parent bone to inhabit the osseous wound. The present review discusses the evolution of the GBR biological rationale and therapeutic concept over the last two decades. Further, an overview of the GBR research history is provided with specific focus on the evidence available on its effectiveness and predictability in promoting the regeneration of critical size cranio-maxillo-facial defects, the neo-osteogenesis potential and the reconstruction of atrophic alveolar ridges before, or in conjunction with, the placement of dental implants. The authors conclude that future research should focus on (a) the investigation of the molecular mechanisms underlying the wound healing process following GBR application; (b) the identification of site and patient related factors which impact on the effectiveness and predictability of GBR therapy and (c) the evaluation of the pathophysiology of the GBR healing process in the presence of systemic conditions potentially affecting the skeletal system.To cite this article:Retzepi M, Donos N. Guided Bone Regeneration: biological principle and therapeutic applications.Clin. Oral Impl. Res. 21, 2010; 567-576.doi: 10.1111/j.1600-0501.2010.01922.x.

Guided Bone Regeneration: biological principle and therapeutic applications

Collagen, the most abundant extracellular matrix protein in animal kingdom belongs to a family of fibrous proteins, which transfer load in tissues and which provide a highly biocompatible environment for cells. This high biocompatibility makes collagen a perfect biomaterial for implantable medical products and scaffolds for in vitro testing systems. To manufacture collagen based solutions, porous sponges, membranes and threads for surgical and dental purposes or cell culture matrices, collagen rich tissues as skin and tendon of mammals are intensively processed by physical and chemical means. Other tissues such as pericardium and intestine are more gently decellularized while maintaining their complex collagenous architectures. Tissue processing technologies are organized as a series of steps, which are combined in different ways to manufacture structurally versatile materials with varying properties in strength, stability against temperature and enzymatic degradation and cellular response. Complex structures are achieved by combined technologies. Different drying techniques are performed with sterilisation steps and the preparation of porous structures simultaneously. Chemical crosslinking is combined with casting steps as spinning, moulding or additive manufacturing techniques. Important progress is expected by using collagen based bio-inks, which can be formed into 3D structures and combined with live cells. This review will give an overview of the technological principles of processing collagen rich tissues down to collagen hydrolysates and the methods to rebuild differently shaped products. The effects of the processing steps on the final materials properties are discussed especially with regard to the thermal and the physical properties and the susceptibility to enzymatic degradation. These properties are key features for biological and clinical application, handling and metabolization.

/pdf/processing-of-collagen-based-biomaterials-and-the-resulting-jzd4h0f0ve.pdf

Processing of collagen based biomaterials and the resulting materials properties.

Graphene, graphene oxide, and reduced graphene oxide have been widely considered as promising candidates for industrial and biomedical applications due to their exceptionally high mechanical stiffness and strength, excellent electrical conductivity, high optical transparency, and good biocompatibility. In this article, we reviewed several techniques that are available for the synthesis of graphene-based nanomaterials, and discussed the biocompatibility and toxicity of such nanomaterials upon exposure to mammalian cells under in vitro and in vivo conditions. Various synthesis strategies have been developed for their fabrication, generating graphene nanomaterials with different chemical and physical properties. As such, their interactions with cells and organs are altered accordingly. Conflicting results relating biocompatibility and cytotoxicity induced by graphene nanomaterials have been reported in the literature. In particular, graphene nanomaterials that are used for in vitro cell culture and in vivo animal models may contain toxic chemical residuals, thereby interfering graphene-cell interactions and complicating interpretation of experimental results. Synthesized techniques, such as liquid phase exfoliation and wet chemical oxidation, often required toxic organic solvents, surfactants, strong acids, and oxidants for exfoliating graphite flakes. Those organic molecules and inorganic impurities that are retained in final graphene products can interact with biological cells and tissues, inducing toxicity or causing cell death eventually. The residual contaminants can cause a higher risk of graphene-induced toxicity in biological cells. This adverse effect may be partly responsible for the discrepancies between various studies in the literature.

https://www.mdpi.com/1422-0067/19/11/3564/pdf

Graphene Nanomaterials: Synthesis, Biocompatibility, and Cytotoxicity.

Polymer membranes have been widely used in guided tissue regeneration (GTR) and guided bone regeneration (GBR). In this review, various commercially available membranes are described. Much attention is paid to the recent development of biodegradable polymers applied in GTR and GBR, and the important issues of biodegradable polymeric membranes, including their classification, latest experimental research and clinical applications, as well as their main challenges are addressed. Herein, natural polymers, synthetic polymers and their blends are all introduced. Pure polymer membranes are biodegradable and biocompatible, but they lack special properties such as antibacterial properties, osteoconductivity, and thus polymer membranes loaded with functional materials such as antibacterial agents and growth factors show many more advantages and have also been introduced in this review. Despite there still being complaints about polymer membranes, such as their low mechanical properties, uncontrollable degradation speed and some other drawbacks, these problems will undoubtedly be conquered and biodegradable polymers will have more applications in GTR and GBR.

Biodegradable Polymer Membranes Applied in Guided Bone/Tissue Regeneration: A Review.

The application of polydopamine (PDA)-modified titanium dioxide nanoparticles (nano-TiO2@PDA) as a new blue-light-activated tooth whitening material was discussed for the first time. Compared with the classical clinical whitening agent (peroxide, hydrogen peroxide, and carbamide peroxide), nano-TiO2@PDA-based treatment not only had a similar whitening effect but also showed remarkably less damage on the enamel structure. Essentially, a highly effective and nondestructive tooth whitening treatment could thus be realized accordingly. The toxicity and antibacterial properties of this material were also evaluated systematically.

Blue-Light -Activated Nano-TiO2@PDA for Highly Effective and Nondestructive Tooth Whitening.

BACKGROUND MicroRNAs (miRNAs) are small, non-coding RNAs that may function as oncogenes or tumor suppressors. Previous studies have shown that the expression level of miR-1246 was enhanced in multiple types of cancers. However, the expression of miR-1246 in human oral squamous cell carcinoma (OSCC) and its prognostic values remain unclear. MATERIAL AND METHODS Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was used to analyze the expression of miR-1246 in 106 pairs of matched normal and tumor tissue samples. The chi-square test was used to examine the associations between miR-1246 expression and the clinicopathological characters. The survival curves were constructed by the Kaplan-Meier method. The influence of each clinical variable on survival was examined by the Cox multivariate regression analysis. RESULTS The expression level of miR-1246 was significantly higher in tumor tissues and oral cancer cell lines than in normal controls (p<0.01). High expression of miR-1246 was found to significantly correlate with nodal status (p=0.015), TNM stage (p=0.005), and tumor grade (p=0.002). Enhanced miR-1246 correlated significantly with patient survival (p<0.01). In multivariate analysis, we found that miR-1246 expression was an independent prognostic factor of poor patient survival (p= 0.036; HR=2.82; 95% CI=1.07-7.43). CONCLUSIONS High miR-1246 expression is associated with poor prognosis in OSCC and may serve as a novel prognostic marker in OSCC.

Expression and clinical significance of microRNA-1246 in human oral squamous cell carcinoma.

Bacterial infection has been a critic problem for implant infections. Poly(L-lactide) (PLLA) membrane has great potential for Guided bone regeneration (GBR), however, PLLA lack antibacterial property and thus may face bacterial infections. In this work, a mussel inspired method was used to treat PLLA membrane with dopamine and formed polydopamine (PDA) coated PLLA (PLLA@PDA), and then silver Nanoparticles (AgNPs) was immobilized on the surface of PLLA via the reduction effect of PDA. The XPS results showed that the silver element contents may be tuned from 1.6% to 15.4%. The AgNPs coated PLLA (PLLA@Ag) showed good antibacterial property (98.3% bactericidal efficiency may be obtained) and good biocompatibility, implying that the PLLA@Ag membrane have potential application as antibacterial GBR membrane, which may enhance the application of PLLA.

Jiaolong Wang

Papers

Biodegradable Polymer Membranes Applied in Guided Bone/Tissue Regeneration: A Review.

Blue-Light -Activated Nano-TiO2@PDA for Highly Effective and Nondestructive Tooth Whitening.

Expression and clinical significance of microRNA-1246 in human oral squamous cell carcinoma.

Silver Nanoparticles Coated Poly(L-Lactide) Electrospun Membrane for Implant Associated Infections Prevention.

L-cysteine modified ZnO: Small change while great progress