Apatite minerals derived from collagen phosphorylation modification induce the hierarchical intrafibrillar mineralization of collagen fibers

Advancing dentin remineralization: Exploring amorphous calcium phosphate and its stabilizers in biomimetic approaches

OBJECTIVE

This review elucidates the mechanisms underpinning intrafibrillar mineralization, examines various amorphous calcium phosphate (ACP) stabilizers employed in dentin's intrafibrillar mineralization, and addresses the challenges encountered in clinical applications of ACP-based bioactive materials.

METHODS

The literature search for this review was conducted using three electronic databases: PubMed, Web of Science, and Google Scholar, with specific keywords. Articles were selected based on inclusion and exclusion criteria, allowing for a detailed examination and summary of current research on dentin remineralization facilitated by ACP under the influence of various types of stabilizers.

RESULTS

This review underscores the latest advancements in the role of ACP in promoting dentin remineralization, particularly intrafibrillar mineralization, under the regulation of various stabilizers. These stabilizers predominantly comprise non-collagenous proteins, their analogs, and polymers. Despite the diversity of stabilizers, the mechanisms they employ to enhance intrafibrillar remineralization are found to be interrelated, indicating multiple driving forces behind this process. However, challenges remain in effectively designing clinically viable products using stabilized ACP and maximizing intrafibrillar mineralization with limited materials in practical applications.

SIGNIFICANCE

The role of ACP in remineralization has gained significant attention in dental research, with substantial progress made in the study of dentin biomimetic mineralization. Given ACP's instability without additives, the presence of ACP stabilizers is crucial for achieving in vitro intrafibrillar mineralization. However, there is a lack of comprehensive and exhaustive reviews on ACP bioactive materials under the regulation of stabilizers. A detailed summary of these stabilizers is also instrumental in better understanding the complex process of intrafibrillar mineralization. Compared to traditional remineralization methods, bioactive materials capable of regulating ACP stability and controlling release demonstrate immense potential in enhancing clinical treatment standards.

Recent advances in the pathogenesis and prevention strategies of dental calculus

Dental calculus severely affects the oral health of humans and animal pets. Calculus deposition affects the gingival appearance and causes inflammation. Failure to remove dental calculus from the dentition results in oral diseases such as periodontitis. Apart from adversely affecting oral health, some systemic diseases are closely related to dental calculus deposition. Hence, identifying the mechanisms of dental calculus formation helps protect oral and systemic health. A plethora of biological and physicochemical factors contribute to the physiological equilibrium in the oral cavity. Bacteria are an important part of the equation. Calculus formation commences when the bacterial equilibrium is broken. Bacteria accumulate locally and form biofilms on the tooth surface. The bacteria promote increases in local calcium and phosphorus concentrations, which triggers biomineralization and the development of dental calculus. Current treatments only help to relieve the symptoms caused by calculus deposition. These symptoms are prone to relapse if calculus removal is not under control. There is a need for a treatment regime that combines short-term and long-term goals in addressing calculus formation. The present review introduces the mechanisms of dental calculus formation, influencing factors, and the relationship between dental calculus and several systemic diseases. This is followed by the presentation of a conceptual solution for improving existing treatment strategies and minimizing recurrence.

Promoting effect of phosvitin in the mineralization of eggshell inner membrane with the application in osteogenic induction scaffold

Exploring affordable and easily prepared inorganic-organic hybrid membrane materials has attracted a great interest in the bone repair field. This study is based on biomimetic mineralization technique to study the role of phosvitin (PV) in the mineralized process of eggshell inner membrane. Results showed that PV promoted the formation of hydroxyapatite on the eggshell inner membrane surface, and the phosvitin content in the simulated body fluid was decreased during the mineralization process. Besides, in vitro preosteoblast experiments indicated that mineralized membrane with PV exhibited more conducive to cell proliferation and differentiation than that mineralized membrane without PV. Interestingly, with the increase of mineralization time, the stimulating ability of mineralized membranes with PV on adhesion, proliferation, alkaline phosphatase activity and collagen type I content gradually improved. In summary, the eggshell inner membrane composites mineralized with PV obtained by biomimetic mineralization might be potential scaffold materials for bone repair.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Phosphoproteomic insight into the changes in structural proteins of muscle architecture associated with texture softening of grass carp (Ctenopharyngodon idella) fillets during chilling storage

Texture is an important sensory attribute of fish affected by modifications of structural proteins in muscle architecture. To investigate the changes in protein phosphorylation during texture softening of fish, the proteins of grass carp muscle after chilling storage of 0 day and 6 days were compared by phosphoproteomics, and their association with texture was analyzed. Totally 1026 unique phosphopeptides on 656 phosphoproteins were identified as differential. They were mainly classified as intracellular myofibril and cytoskeleton, and extracellular matrix, of which the molecular function and biological process were binding into supramolecular assembly and myofilament contraction. The concomitant dephosphorylation of kinases and assembly regulators indicated dephosphorylation and disassembly tendency of sarcomeric architecture. Correlation analysis defined the relation between texture and dephosphorylation of myosin light chain, actin, collagen and cytoskeleton. This study revealed that protein phosphorylation may affect the texture of fish muscle through regulating sarcomeric assembly of structural proteins in muscle architecture.

Osteogenic differentiation of human adipose-derived mesenchymal stem cells in a bisphosphonate-functionalized polycaprolactone/gelatin scaffold

Recent trends in bone tissue engineering have focused on the development of biomimetic constructs with appropriate mechanical and physiochemical properties. Here, we report the fabrication of an innovative biomaterial scaffold based on a new bisphosphonate-containing synthetic polymer combined with gelatin. To this end, zoledronate (ZA)-functionalized polycaprolactone (PCL-ZA) was synthesized by a chemical grafting reaction. After adding gelatin to the PCL-ZA polymer solution, the porous PCL-ZA/gelatin scaffold was fabricated by the freeze-casting method. A scaffold with aligned pores and a porosity of 82.04 % was obtained. During in vitro biodegradability test, 49 % of its initial weight lost after 5 weeks. The elastic modulus of the PCL-ZA/gelatin scaffold was 31.4 MPa, and its tensile strength was 4.2 MPa. Based on the results of MTT assay, the scaffold had good cytocompatibility with human Adipose-Derived Mesenchymal Stem Cells (hADMSCs). Furthermore, cells grown in PCL-ZA/gelatin scaffold showed the highest mineralization and ALP activity compared to other test groups. Results of the RT-PCR test revealed that RUNX2, COL 1A1, and OCN genes were expressed in PCL-ZA/gelatin scaffold at the highest level, suggesting its good osteoinductive capacity. These results revealed that PCL-ZA/gelatin scaffold could be considered a proper biomimetic platform for bone tissue engineering.

Biomechanical Characteristics and Analysis Approaches of Bone and Bone Substitute Materials

Bone has a special structure that is both stiff and elastic, and the composition of bone confers it with an exceptional mechanical property. However, bone substitute materials that are made of the same hydroxyapatite (HA) and collagen do not offer the same mechanical properties. It is important for bionic bone preparation to understand the structure of bone and the mineralization process and factors. In this paper, the research on the mineralization of collagen is reviewed in terms of the mechanical properties in recent years. Firstly, the structure and mechanical properties of bone are analyzed, and the differences of bone in different parts are described. Then, different scaffolds for bone repair are suggested considering bone repair sites. Mineralized collagen seems to be a better option for new composite scaffolds. Last, the paper introduces the most common method to prepare mineralized collagen and summarizes the factors influencing collagen mineralization and methods to analyze its mechanical properties. In conclusion, mineralized collagen is thought to be an ideal bone substitute material because it promotes faster development. Among the factors that promote collagen mineralization, more attention should be given to the mechanical loading factors of bone.

Poly(acrylic acid)-Assisted Intrafibrillar Mineralization of Type I Collagen: A Review

The mineralization of type I collagen is a biological process occurring in vertebrates by which some hard tissues such as bone and dentin are constructed. Due to the extensive clinical needs for bone defect repair and remineralization of mineral-depleted dentin, biomimetic mineralization of collagen is attracting more and more interests. Synthetic analogs of noncollagenous proteins are necessary for directing the in vitro mineralization. In this paper, the function and mechanism of poly(acrylic acid) (PAA) in regulating the mineralization, especially intrafibrillar mineralization (IM) of collagen are reviewed. As two mineralization patterns (extrafibrillar and intrafibrillar) co-exist in natural hard tissues, differences between them in terms of microstructure, biodegradation, cytocompatibility, osteoinduction in vitro, and performance in vivo are systematically compared. Then the roles of PAA in biomimetic collagen IM within one-analog and two-analog systems are discussed, respectively. Moreover, mineralization of some self-mineralizable collagen matrices is described. Due to the interactions between collagen and PAA play a crucial role in the processes of collagen mineralization, some reference researches are also provided involving the collagen/PAA interactions in some other fields. Finally, this review is ended with an outlook for future potential improvements based on the collection of existing bottlenecks in this field.

Effects of Mangosteen Peel Phenolic Compounds on Tilapia Skin Collagen-Based Mineralized Scaffold Properties

A proper valorization of biological waste sources for an effective conversion into composites for tissue engineering is discussed in this study. Hence, the collagen and the phenolic compound applied in this investigation were extracted from waste sources, respectively, fish industry rejects and the peels of the mangosteen fruit. Porous scaffolds were prepared by combining both components at different compositions and mineralized at different temperatures to evaluate the modifications in the biomimetic formation of apatite. The inclusion of mangosteen extract showed the advantage of increasing the collagen denaturation temperature, improving the stability of its triple helix. Moreover, the extract provided antioxidant activity due to its phenolic composition, as confirmed by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assays. Mineralization was successfully achieved as indicated by thermogravimetry and scanning electron microscopy. A higher temperature and a lower extract concentration reduced the calcium phosphate deposits. The extract also affected the pore size, particularly at a lower concentration. The X-ray diffraction pattern identified a low degree of crystallization. A high mineralization temperature induced the formation of smaller crystallites ranging from 18.9 to 25.4 nm. Although the deposited hydroxyapatite showed low crystallinity, the scaffolds are suitable for bone tissue applications and may be effective in controlling the resorbability rate in tissue regeneration.

In-situ mineralized homogeneous collagen-based scaffolds for potential guided bone regeneration

For guided bone regeneration (GBR) in clinical orthopedics, the importance of a suitable scaffold which can provide the space needed for bone regeneration and simultaneously promotes the new bone formation cannot be overemphasized. Due to its excellent biocompatibility, mechanical strength, and similarity in structure and composition to natural bone, the mineralized collagen-based scaffolds have been increasingly considered as promising GBR scaffolds. Herein, we propose a novel method to fabricate an in-situ mineralized homogeneous collagen-based scaffold (IMHCS) with excellent osteogenic capability for GBR by electrospinning the collagen solution in combination with essential mineral ions. The IMHCS exhibited homogeneous distribution of apatite crystals in electrospun fibers, which helped to achieve a significantly higher tensile strength than the pure collagen scaffold (CS) and the scaffold with directly added nano-hydroxyapatite particles (HAS). Furthermore, the IMHCS had significantly better cell compatibility, cell migration ratio, and osteogenic differentiation property than the HAS and CS. Therefore, the IMHCS not only retains traditional function of inhibiting fibroblast invasion, but also possesses excellent osteogenic differentiation property, indicating a robust alternative for GBR applications.

Biomechanics and mechanobiology of the bone matrix

The bone matrix plays an indispensable role in the human body, and its unique biomechanical and mechanobiological properties have received much attention. The bone matrix has unique mechanical anisotropy and exhibits both strong toughness and high strength. These mechanical properties are closely associated with human life activities and correspond to the function of bone in the human body. None of the mechanical properties exhibited by the bone matrix is independent of its composition and structure. Studies on the biomechanics of the bone matrix can provide a reference for the preparation of more applicable bone substitute implants, bone biomimetic materials and scaffolds for bone tissue repair in humans, as well as for biomimetic applications in other fields. In providing mechanical support to the human body, bone is constantly exposed to mechanical stimuli. Through the study of the mechanobiology of the bone matrix, the response mechanism of the bone matrix to its surrounding mechanical environment can be elucidated and used for the health maintenance of bone tissue and defect regeneration. This paper summarizes the biomechanical properties of the bone matrix and their biological significance, discusses the compositional and structural basis by which the bone matrix is capable of exhibiting these mechanical properties, and studies the effects of mechanical stimuli, especially fluid shear stress, on the components of the bone matrix, cells and their interactions. The problems that occur with regard to the biomechanics and mechanobiology of the bone matrix and the corresponding challenges that may need to be faced in the future are also described.

Physical and Chemical Characterization of Biomineralized Collagen with Different Microstructures

Mineralized collagen is the basic unit in hierarchically organized natural bone with different structures. Polyacrylic acid (PAA) and periodic fluid shear stress (FSS) are the most common chemical and physical means to induce intrafibrillar mineralization. In the present study, non-mineralized collagen, extrafibrillar mineralized (EM) collagen, intrafibrillar mineralized (IM) collagen, and hierarchical intrafibrillar mineralized (HIM) collagen induced by PAA and FSS were prepared, respectively. The physical and chemical properties of these mineralized collagens with different microstructures were systematically investigated afterwards. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that mineralized collagen with different microstructures was prepared successfully. The pore density of the mineralized collagen scaffold is higher under the action of periodic FSS. Fourier transform infrared spectroscopy (FTIR) analysis showed the formation of the hydroxyapatite (HA) crystal. A significant improvement in the pore density, hydrophilicity, enzymatic stability, and thermal stability of the mineralized collagen indicated that the IM collagen under the action of periodic FSS was beneficial for maintaining collagen activity. HIM collagen fibers, which are prepared under the co-action of periodic FSS and sodium tripolyphosphate (TPP), may pave the way for new bone substitute material applications.

Dual Functions of MDP Monomer with De- and Remineralizing Ability

Methacryloyloxydecyl dihydrogen phosphate (MDP) has been speculated to induce mineralization, but there has been no convincing evidence of its ability to induce intrafibrillar mineralization. Polymers play a critical role in biomimetic mineralization as stabilizers/inducers of amorphous precursors. Hence, MDP-induced biomimetic mineralization without polymer additives has not been fully verified or elucidated. By combining 3-dimensional stochastic optical reconstruction microscopy, surface zeta potentials, contact angle measurements, inductively coupled plasma-optical emission spectroscopy, transmission electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy with circular dichroism, we show that amphiphilic MDP can not only demineralize dentin by releasing protons as an acidic functional monomer but also infiltrate collagen fibrils (including dentin collagen), unwind the triple helical structure by breaking hydrogen bonds, and finally immobilize within collagen. MDP-bound collagen functions as a huge collagenous phosphoprotein (HCPP), in contrast to chemical phosphorylation modifications. HCPP can induce biomimetic mineralization itself without polymer additives by alternatively attracting calcium and phosphate through electrostatic attraction. Therefore, we herein propose the dual functions of amphiphilic MDP monomer with de- and remineralizing ability. MDP in the free state can demineralize dentin substrates by releasing protons, whereas MDP in the collagen-bound state as HCPP can induce intrafibrillar mineralization. The dual functions of MDP monomer with de- and remineralization properties might create a new epoch in adhesive dentistry and preventive dentistry.

Novel pulp capping material based on sodium trimetaphosphate: synthesis, characterization, and antimicrobial properties

OBJECTIVES

To evaluate the mechanical, physicochemical, and antimicrobial properties of four different formulations containing micro- or nanoparticles of sodium trimetaphosphate (mTMP and nTMP, respectively).

METHODOLOGY

Four experimental groups were used in this investigation: two mTMP groups and two nTMP groups, each containing zirconium oxide (ZrO2), and solution containing either chitosan or titanium oxide (TiO2) nanoparticles (NPs). Setting time, compression resistance, and radiopacity were estimated. The agar diffusion test was used to assess the antimicrobial activity of the formulations against five different microbial strains: Streptococcus mutans, Lactobacillus casei, Actinomyces israelii, Candida albicans, and Enterococcus faecalis. Parametric and nonparametric tests were performed after evaluating homoscedasticity data (p<0.05).

RESULTS

From the properties evaluated, nTMP cements required less setting time and showed greater resistance to compression. Cements containing TiO2 showed greater radiopacity for both nTMP and mTMP. All four cement formulations showed antimicrobial activity against S. mutans and L. casei.

CONCLUSION

Formulations containing nTMP have shorter setting times and higher compressive strength, and those with TiO2 nanoparticles showed antimicrobial activities. Clinical relevance: The cement containing nTMP, ZrO2, and TiO2 could be an alternative material for protecting the pulp complex.

Orthophosphate and alkaline phosphatase induced the formation of apatite with different multilayered structures and mineralization balance

Mineralized collagen is a natural organic-inorganic composite. The combination of organic collagen and inorganic apatite to form different nanostructures is the key to producing bone substitutes with biomechanical properties that are as identical to normal bone as possible. However, the formation of apatite with different nanostructures during collagen mineralization is unexplored. Here, pyrophosphate (Pyro-P), as an important hydrolysate of adenosine triphosphate in the body, was introduced to prepare mineralized collagen under the regulation of alkaline phosphatase (ALP) and orthophosphate (Ortho-P). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed that mineralized collagen, which combined with different crystallinities and multilayered structured apatite, was successfully prepared. A combination of ion chromatography (IC), Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD), and thermogravimetry (TG) analyses revealed the crucial role of Ortho-P in the formation of multilayered flower-shaped apatite with different crystallinities and in the maintenance of mineralization balance. Mineralization balance is of great significance for maintaining normal bone morphology during bone regeneration. Overall, our results provide a promising method to produce new bone substitute materials for the repair of large bone defects and a deeper insight into the mechanisms of biomineralization.

Diffusion-Controlled Crystallization of Calcium Phosphate in a Hydrogel toward a Homogeneous Octacalcium Phosphate/Agarose Composite

Diffusion-controlled crystallization in a hydrogel has been investigated to synthesize organic/inorganic hybrid composites and obtain a fundamental understanding of the detailed mechanism of biomineralization. Although calcium phosphate/hydrogel composites have been intensively studied and developed for the application of bone substitutes, the synthesis of homogeneous and integrated composites remains challenging. In this work, diffusion-controlled systems were optimized by manipulating the calcium ion flux at the interface, concentration gradient, and diffusion coefficient to synthesize homogeneous octacalcium phosphate/hydrogel composites with respect to the crystal morphology and density. The ion flux and local pH play an important role in determining the morphology, density, and phase of the crystals. This study suggests a model system that can reveal the relation between local conditions and the resulting crystal phase in diffusion-limited systems and provides a synthetic method for homogeneously organized organic/inorganic composites.

Biofunctional phosphorylated magnetic scaffold for bone tissue engineering

The development of highly bioactive engineered scaffolds is required to promote bone regeneration and the success of bone tissue engineering treatment approaches. This study attempts to fabricate a biofunctional magnetic scaffold based on new phosphorylated polycaprolactone combined with gelatin (MNPs-PCL-P/gelatin). Phosphorylated polymer and magnetic nanoparticles (MNPs) were synthesized and characterized by NMR, FT-IR, TEM, and DLS instruments. The synthetic polymer, MNPs, and biopolymer were mixed then freeze-dried to prepare a porous scaffold. Physiochemical assessments showed that a scaffold with well-developed porous morphology, and stable structure was obtained. MNPs-PCL-P/gelatin scaffold had no toxicity on human dental pulp stem cells (hDPSCs). The use of phosphorous-containing polymer resulted in improvement of the scaffold's osteoconductivity to support proper cell attachment and promote cell proliferation. Phosphate group by mimicking function of bone phosphate groups stimulate bone mineralization that reflected by alizarin red S staining assay. The presence of MNPs resulted in higher ALP activity and increased expression level of RUNX2, BMP2 osteogenic biomarkers. Also, phosphorylation enhanced osteoinductivity of scaffold and upregulate RUNX2, BMP2, COL1A1, and OCN genes in phosphors-containing scaffold test groups. It seems that biocompatible MNPs-PCL-P/gelatin scaffold possesses the potential of applications in bone tissue engineering.

Mineralization of Phosphorylated Fish Skin Collagen/Mangosteen Scaffolds as Potential Materials for Bone Tissue Regeneration

In this study, a potential hard tissue substitute was mimicked using collagen/mangosteen porous scaffolds. Collagen was extracted from Tilapia fish skin and mangosteen from the waste peel of the respective fruit. Sodium trimetaphosphate was used for the phosphorylation of these scaffolds to improve the nucleation sites for the mineralization process. Phosphate groups were incorporated in the collagen structure as confirmed by their attenuated total reflection Fourier transform infrared (ATR-FTIR) bands. The phosphorylation and mangosteen addition increased the thermal stability of the collagen triple helix structure, as demonstrated by differential scanning calorimetry (DSC) and thermogravimetry (TGA) characterizations. Mineralization was successfully achieved, and the presence of calcium phosphate was visualized by scanning electron microscopy (SEM). Nevertheless, the porous structure was maintained, which is an essential characteristic for the desired application. The deposited mineral was amorphous calcium phosphate, as confirmed by energy dispersive X-ray spectroscopy (EDX) results.

Highly aligned hierarchical intrafibrillar mineralization of collagen induced by periodic fluid shear stress

Periodic fluid shear stress (FSS) is one of the main mechanical microenvironments in mineralization of bone matrix. To elucidate the mechanism of periodic FSS in collagen mineralization, a mechanical loading induced mineralization system is developed and compared with traditional polyacrylic acid (PAA) induced mineralization. Fourier transform infrared (FTIR) spectroscopy, calcium-to-phosphorus molar ratio and transmission electron microscopy (TEM) demonstrate that both periodic FSS and PAA can control the size of amorphous calcium phosphate (ACP) to avoid aggregation and help the formation of intrafibrillar mineralization. Differently, periodic FSS under a proper cycle and range can accelerate the conversion of ACP to apatite crystals and alleviate the reduced transformation caused by PAA. Under the action of template analogues, periodic FSS can also promote the formation of highly oriented hierarchical intrafibrillar mineralized (HIM) collagen. These findings are helpful for understanding the mechanism of collagen mineralization in natural bone matrix and contribute to the design of novel bone substitute materials with hierarchical structures.

Biomineralization of Collagen-Based Materials for Hard Tissue Repair

Hydroxyapatite (HA) reinforced collagen fibrils serve as the basic building blocks of natural bone and dentin. Mineralization of collagen fibrils play an essential role in ensuring the structural and mechanical functionalities of hard tissues such as bone and dentin. Biomineralization of collagen can be divided into intrafibrillar and extrafibrillar mineralization in terms of HA distribution relative to collagen fibrils. Intrafibrillar mineralization is termed when HA minerals are incorporated within the gap zone of collagen fibrils, while extrafibrillar mineralization refers to the minerals that are formed on the surface of collagen fibrils. However, the mechanisms resulting in these two types of mineralization still remain debatable. In this review, the evolution of both classical and non-classical biomineralization theories is summarized. Different intrafibrillar mineralization mechanisms, including polymer induced liquid precursor (PILP), capillary action, electrostatic attraction, size exclusion, Gibbs-Donnan equilibrium, and interfacial energy guided theories, are discussed. Exemplary strategies to induce biomimetic intrafibrillar mineralization using non-collagenous proteins (NCPs), polymer analogs, small molecules, and fluidic shear stress are discussed, and recent applications of mineralized collagen fibers for bone regeneration and dentin repair are included. Finally, conclusions are drawn on these proposed mechanisms, and the future trend of collagen-based materials for bone regeneration and tooth repair is speculated.

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.