Synthesis of bone-like nanocomposites using multiphosphorylated peptides

Research progress of biomimetic materials in oral medicine

Biomimetic materials are able to mimic the structure and functional properties of native tissues especially natural oral tissues. They have attracted growing attention for their potential to achieve configurable and functional reconstruction in oral medicine. Though tremendous progress has been made regarding biomimetic materials, significant challenges still remain in terms of controversy on the mechanism of tooth tissue regeneration, lack of options for manufacturing such materials and insufficiency of in vivo experimental tests in related fields. In this review, the biomimetic materials used in oral medicine are summarized systematically, including tooth defect, tooth loss, periodontal diseases and maxillofacial bone defect. Various theoretical foundations of biomimetic materials research are reviewed, introducing the current and pertinent results. The benefits and limitations of these materials are summed up at the same time. Finally, challenges and potential of this field are discussed. This review provides the framework and support for further research in addition to giving a generally novel and fundamental basis for the utilization of biomimetic materials in the future.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Topographically guided hierarchical mineralization

Material platforms based on interaction between organic and inorganic phases offer enormous potential to develop materials that can recreate the structural and functional properties of biological systems. However, the capability of organic-mediated mineralizing strategies to guide mineralization with spatial control remains a major limitation. Here, we report on the integration of a protein-based mineralizing matrix with surface topographies to grow spatially guided mineralized structures. We reveal how well-defined geometrical spaces defined within the organic matrix by the surface topographies can trigger subtle changes in single nanocrystal co-alignment, which are then translated to drastic changes in mineralization at the microscale and macroscale. Furthermore, through systematic modifications of the surface topographies, we demonstrate the possibility of selectively guiding the growth of hierarchically mineralized structures. We foresee that the capacity to direct the anisotropic growth of such structures would have important implications in the design of biomineralizing synthetic materials to repair or regenerate hard tissues.

Novel nanomaterial-organism hybrids with biomedical potential

Instinctive hierarchically biomineralized structures of various organisms, such as eggs, algae, and magnetotactic bacteria, afford extra protection and distinct performance, which endow fragile organisms with a tenacious ability to adapt and survive. However, spontaneous formation of hybrid materials is difficult for most organisms in nature. Rapid development of chemistry and materials science successfully obtained the combinations of organisms with nanomaterials by biomimetic mineralization thus demonstrating the reproduction of the structures and functions and generation of novel functions that organisms do not possess. The rational design of biomaterial-organism hybridization can control biological recognition, interactions, and metabolism of the organisms. Thus, nanomaterial-organism hybrids represent a next generation of organism engineering with great potential biomedical applications. This review summarizes recent advances in material-directed organism engineering and is mainly focused on biomimetic mineralization technologies and their outstanding biomedical applications. Three representative types of biomimetic mineralization are systematically introduced, including external mineralization, internal mineralization, and genetic engineering mineralization. The methods involving hybridization of nanomaterials and organisms based on biomimetic mineralization strategies are described. These strategies resulted in applications of various nanomaterial-organism hybrids with multiplex functions in cell engineering, cancer treatment, and vaccine improvement. Unlike classical biological approaches, this material-based bioregulation is universal, effective, and inexpensive. In particular, instead of traditional medical solutions, the integration of nanomaterials and organisms may exploit novel strategies to solve current biomedical problems. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

A novel amphiphilic oligopeptide induced the intrafibrillar mineralisation via interacting with collagen and minerals

Mineralised collagen fibrils constitute the basic building blocks of bone, dentin and cementum. Noncollagenous proteins (NCPs) that are indispensable for collagen biomineralisation are not commercially available, and the mechanism of intrafibrillar mineralisation remains debatable. Herein, synthetic biomimetic molecules are regarded as alternative candidates for NCPs, and more convenient in revealing the mechanism of intrafibrillar mineralisation in vitro. Here, we fabricated a novel amphiphilic oligopeptide imitating a natural NCP. We aimed to investigate the effectiveness of the oligopeptide in intrafibrillar mineralisation and partially reveal the corresponding mechanism in vitro. The effectiveness of the oligopeptide in intrafibrillar mineralisation was characterised from the following aspects: (1) mineral interaction, (2) collagen binding and (3) induction of intrafibrillar mineralisation. Results indicated that the self-assembled oligopeptide could attract calcium ions inducing the formation of amorphous precursors; and bind onto the surface of collagen fibrils. These processes were mainly driven by the electrostatic attraction and hydrogen bonds. The self-assembled oligopeptide induced the intrafibrillar mineralisation of reconstituted collagen fibrils, in which the c-axis of apatite crystallites was roughly parallel to the long axis of the fibrils. The collagen mineralisation was achieved by binding with the self-assembled oligopeptide to increase the pool of mineralization precursors available for intrafibrillar mineralisation. In addition, the self-assembled oligopeptide induced dentin collagen remineralisation and formed a 30 μm-thick remineralised layer within 96 h. Our work sheds light on the fabrication of a novel biomimetic molecule for collagen mineralisation. The results should serve as a reference for understanding the mechanism of intrafibrillar mineralisation.

Natural protein bioinspired materials for regeneration of hard tissues

This review describes the protein bioinspired materials for the repair of hard tissues such as enamel, dentin and bone.

Biomineralization-Inspired Material Design for Bone Regeneration

Synthetic substitutes of bone grafts, such as calcium phosphate-based ceramics, have shown some good clinical successes in the regeneration of large bone defects and are currently extensively used. In the past decade, the field of biomineralization has delivered important new fundamental knowledge and techniques to better understand this fascinating phenomenon. This knowledge is also applied in the field of biomaterials, with the aim of bringing the composition and structure, and hence the performance, of synthetic bone graft substitutes even closer to those of the extracellular matrix of bone. The purpose of this progress report is to critically review advances in mimicking the extracellular matrix of bone as a strategy for development of new materials for bone regeneration. Lab-made biomimicking or bioinspired materials are discussed against the background of the natural extracellular matrix, starting from basic organic and inorganic components, and progressing into the building block of bone, the mineralized collagen fibril, and finally larger, 2D and 3D constructs. Moreover, bioactivity studies on state-of-the-art biomimicking materials are discussed. By addressing these different topics, an overview is given of how far the field has advanced toward a true bone-mimicking material, and some suggestions are offered for bridging current knowledge and technical gaps.

Biomineralization-related specialization of hemocytes and mantle tissues of the Pacific oyster Crassostrea gigas

The molluscan exoskeleton (shell) plays multiple important roles including structural support, protection from predators and stressors, and physiological homeostasis. Shell formation is a tightly regulated biological process that allows molluscs to build their shells even in environments unfavorable for mineral precipitation. Outer mantle edge epithelial cells (OME) and hemocytes were implicated in this process; however, the exact functions of these cell types in biomineralization are not clear. Pacific oysters (Crassostrea gigas) were used to study differences in the expression profiles of selected biomineralization-related genes in hemocytes and mantle cells, and the functional characteristics of hemocytes such as adhesion, motility and phagocytosis. The specialized role of OME in shell formation was supported by high expression levels of the extracellular matrix (ECM) related and cell-cell interaction genes. Density gradient separation of hemocytes revealed distinct phenotypes based on the cell morphology, gene expression patterns, motility and adhesion characteristics. These hemocyte fractions can be categorized into two functional groups, i.e. biomineralization and immune response cells. Gene expression profiles of the putative biomineralizing hemocytes indicate that in addition to their proposed role in mineral transport, hemocytes also contribute to the formation of the ECM, thus challenging the current paradigm of the mantle as the sole source of the ECM for shell formation. Our findings corroborate the specialized roles of hemocytes and the OME in biomineralization and emphasize complexity of the biological controls over shell formation in bivalves.

The Mineral-Collagen Interface in Bone

The interface between collagen and the mineral reinforcement phase, carbonated hydroxyapatite (cAp), is essential for bone's remarkable functionality as a biological composite material. The very small dimensions of the cAp phase and the disparate natures of the reinforcement and matrix are essential to the material's performance but also complicate study of this interface. This article summarizes what is known about the cAp-collagen interface in bone and begins with descriptions of the matrix and reinforcement roles in composites, of the phases bounding the interface, of growth of cAp growing within the collagen matrix, and of the effect of intra- and extrafibrilar mineral on determinations of interfacial properties. Different observed interfacial interactions with cAp (collagen, water, non-collagenous proteins) are reviewed; experimental results on interface interactions during loading are reported as are their influence on macroscopic mechanical properties; conclusions of numerical modeling of interfacial interactions are also presented. The data suggest interfacial interlocking (bending of collagen molecules around cAp nanoplatelets) and water-mediated bonding between collagen and cAp are essential to load transfer. The review concludes with descriptions of areas where new research is needed to improve understanding of how the interface functions.

A review of the biology of calcium phosphate sequestration with special reference to milk

In milk, a stable fluid is formed in which sequestered nanoclusters of calcium phosphate are substructures in casein micelles. As a result, calcium and phosphate concentrations in milk can be far in excess of their solubility. Variations of calcium, phosphate and casein concentrations in milks, both within and among species, are mainly due to the formation of the nanocluster complexes. Caseins evolved from tooth and bone proteins well before the evolution of lactation. It has therefore been suggested that the role of caseins in milk is an adaptation of an antecedent function in the control of some aspect of biomineralisation. There is new evidence that nanocluster-type complexes are also present in blood serum and, by implication, in many other closely related biofluids. Because such fluids are stable but nevertheless supersaturated with respect to the bone and tooth mineral hydroxyapatite, they allow soft and mineralised tissues to co-exist in the same organism with relative ease. An appreciable concentration of nanocluster complexes exists in fresh saliva. Such saliva may stabilise tooth mineral and help to repair demineralised lesions. In the extracellular matrix of bone, nanocluster complexes may be involved in directing the amorphous calcium phosphate to intrafibrillar spaces in collagen where they can mature into oriented apatite crystals. Thus, evidence is accumulating that calcium phosphate sequestration by phosphopeptides to form equilibrium complexes, first observed in milk, is more generally important in the control of physiological calcification.