Controlling Enamel Remineralization by Amyloid-Like Amelogenin Mimics

Next-Generation Strategies for Enamel Repair and Regeneration: Advances in Biomaterials and Translational Challenges

BACKGROUND

Enamel regeneration and remineralization are critical for restoring enamel integrity, as natural enamel lacks the ability to regenerate due to the absence of ameloblasts. The increasing prevalence of dental caries and the irreversible nature of enamel damage highlight the need for advanced repair strategies.

METHODS

This review examines the latest advancements in enamel regeneration and remineralization, focusing on biomaterials, nanotechnology-based approaches, and bioengineering strategies. Google Scholar, Scopus (Elsevier), and PubMed databases were used for the selection of literature. The search included key terms such as "enamel regeneration," "biomimetic enamel repair," "stem cell-based enamel regeneration," "nanotechnology in enamel repair," "hydroxyapatite enamel remineralization," and "biomaterials for enamel remineralization."

RESULTS

Various strategies have been explored for enamel remineralization, including self-assembling peptides, dendrimers, hydrogels, and electrospun mats, each demonstrating varying success in laboratory and preclinical studies. While casein-phosphopeptide-stabilized amorphous calcium phosphate (CPP-ACP) combined with fluoride remains a widely used clinical remineralization agent, integrating CPP-ACP with nanotechnology is an emerging area requiring further research. Enamel bioengineering approaches utilizing stem/progenitor cells offer potential, though challenges remain in achieving clinical translation.

CONCLUSION

Despite advancements, replicating the hierarchical structure and mechanical properties of natural enamel remains challenging. Nanotechnology-driven approaches, bioengineered scaffolds, and interdisciplinary collaboration hold promise for optimizing enamel regeneration techniques. Further research is necessary to enhance clinical applicability and develop scalable, effective treatments for enamel restoration.

Antimicrobial, remineralization, and infiltration: advanced strategies for interrupting dental caries

Dental caries, driven by plaque biofilm, poses a major oral health challenge due to imbalance in mineralization and demineralization. The primary objective in caries management is to maintain biofilm homeostasis while facilitating the repair and regeneration of dental hard tissues, thus restoring both structural integrity and functionality of affected teeth. Though antimicrobial and remineralization approaches haven shown promise, their standalone utilization without concurrent bacterial control or rebalancing lacks an integrated strategy to effectively arrest caries progression. Furthermore, according to the principles of minimally invasive dentistry, treatment materials should exhibit high permeability to ensure optimal sealing of demineralized tooth surfaces. The concept of interrupting dental caries (IDC) has emerged as a holistic approach, drawing upon extensive research encompassing three pivotal techniques: antibacterial strategies, remineralization therapies, and infiltration mechanisms, all of which are indispensable components in combating the progression of dental caries. In this review, we provide a comprehensive overview of the mechanisms and applications of antibacterial, remineralization, and infiltration technologies within the context of caries management. Additionally, we summarize advanced materials that align with the IDC concept, aiming to offer valuable insights for designing next-generation materials adept at preventing or halting caries progression efficiently.

The Phase-Transited Lysozyme Coating Modified Small Intestinal Submucosa Membrane Loaded with Calcium and Zinc Ions for Enhanced Bone Regeneration

Bone defects caused by severe trauma, tumors, infections and diseases remain a global challenge due to limited natural regeneration capacity of bone tissue in large-scale or complex injuries. Guided bone regeneration (GBR) has emerged as a pivotal technique in addressing these issues, relying on barrier membranes to facilitate osteoprogenitor cell infiltration. Current clinical GBR membranes function solely as physical barriers, lacking antibacterial and osteoinductive properties, which underscores the need for advanced alternatives. This study focuses on resorbable GBR membranes made from small intestinal submucosa (SIS), known for biocompatibility and tissue regeneration but hindered by low mechanical strength and rapid degradation. In addition, SIS lacks both antibacterial properties and strong osteogenic capabilities. Enhancements involve crosslinking treatment and dual incorporation of calcium (Ca2+) and zinc (Zn2+), which address the physical property shortcomings and synergistically boost osteoinductivity by activating osteogenic signaling pathways. Additionally, phase-transited lysozyme (PTL) nanofilm technique enables efficient ion loading and controlled release, while offering antibacterial properties. In this study, a multifunctional SIS membrane is constructed by PTL-ions layers, providing a potential solution to the challenge of clinical bone defects.

Preparation of barium sulfate/polymer hybrid nanoparticles from Bunte salt precursors

Barium sulfate suspensions are commonly used as contrast agents for improving the resolution of X-ray imaging. However, current limitations are rapid contrast washout and low stability in water. Polymer nanoparticles are synthesized by copolymerizing vinyl benzyl thiosulfate with methyl methacrylate in a miniemulsion by free-radical polymerization. BaSO4 is then formed by the hydrolysis of thiosulfate-functionalized nanoparticles, leading to the production of sulfate ions, which react subsequently with Ba2+ in dispersion.

Mesoscale orchestration of collagen-based hierarchical mineralization

Mesoscale building blocks are instrumental in bridging multilevel hierarchical mineralization, endowing macroscale entities with remarkable functionality and mechanical properties. However, the mechanism orchestrating the homogeneous morphology of mesoscale mineralized motifs in collagen-based hard tissues remains unknown. Here, utilizing avian tendons as a mineralization model, we reveal a robust correlation between the mesoscale mineralized spherules and the presence of phosvitin. By designing a phosvitin-stabilized biomineral cluster medium, we replicate the well-defined mesoscale spherical structure within collagen matrix in vitro and ex vivo. In-depth studies reveal that phosvitin undergoes a conformational transition in the presence of biominerals at physiological concentrations, and self-assembles into mineral-dense amyloid-like aggregates. The spatial binding of these mineral-dense aggregates to collagen serves as a template for guiding the formation of mineralized spherules on the mesoscale. On the nanoscale, this binding facilitates mineral precursor release and diffusion into the fibrils for intrafibrillar mineralization. This discovery underscores the pivotal role of phosvitin-biomineral aggregates in templating hierarchical mineralization from the mesoscale to the nanoscale. This study not only elucidates the intricate mechanism underlying the collagen-based mineralization hierarchy but also promotes a cutting-edge advance in highly biomimetic material design and regenerative medicine.

Evaluation of bacterial anti-adhesion and sustained antimicrobial abilities of chlorhexidine gluconate-loaded phase-transited lysozyme nanoparticle suspension on dentine: An ex vivo study

AIM

To evaluate the effect of chlorhexidine gluconate-loaded phase-transited lysozyme (CHG@PTL) coating on inhibiting bacterial adhesion and biofilm formation in an ex vivo root canal dentine model.

METHODOLOGY

The physicochemical and structural characteristics of CHG@PTL nanoparticle suspension and its coating formed on the dentine surface were analysed by thioflavin T fluorescence assay, transmission electron microscopy and confocal laser scanning microscopy (CLSM). The sustained chlorhexidine release profile of the CHG@PTL coating on the dentine surface was compared with that of the 2% CHG solution. By comparing with phosphate-buffered saline, 1% sodium hypochlorite and 2% CHG solutions, the sustained antibacterial ability of the CHG@PTL coating and its effects on adhesion and biofilm formation of three types of bacteria (E. faecalis, S. mutans, and A. viscous) were analysed in ex vivo root canal dentine models using the serial plate transfer test (SPTT) and CLSM with live/dead bacterial staining, respectively.

RESULTS

CHG promoted the lysozyme protein to form a higher proportion of β-sheet structure during phase transition. In the CHG@PTL nanoparticle suspension, characteristic drug-loaded nanospheres with a high concentration of CHG molecules inside and an outer PTL nanofilm were observed, and they formed a thinner and tighter coating on the dentine surface. The CHG@PTL coating on the dentine surface showed a significantly higher cumulative release amount of chlorhexidine than that of 2% CHG (p < .05). The results of SPTT showed that the CHG@PTL coating had a longer antibacterial duration than the control groups. After 12 h of incubation, a higher number of bacteria were agglutinated on the CHG@PTL coating surface compared to the control groups (p < .05). After 7 days of incubation, the number of agglutinated bacteria significantly decreased. At two time points, the percentage of dead bacteria on the CHG@PTL coating surface was the highest among all experimental groups based on CLSM observation (over 99.9% for all three bacteria, p < .001).

CONCLUSIONS

CHG@PTL nanoparticle suspension could form an antimicrobial coating on the surface of dentine with a novel 'agglutinating bacteria and sterilizing' mode.

Biomimetic Janus Particles Induced In Situ Interfacial Remineralization for Dentin Hypersensitivity

Dentin hypersensitivity (DH), caused by the exposure of dentin tubules, is a common complaint of dental patients. Although occlusion of the exposed tubules is the primary treatment approach, the complex oral environment, and multiple simultaneous requirements often hinder its implementation. In this study, strawberry‐shaped hemispheric Janus particles (JPs) are synthesized, and their use in the treatment of DH is evaluated in vitro and in an animal model. The hemispheric side of the JPs is modified with polymers of quaternary ammonium salts (QASs) to form a superhydrophobic coating with antibiofilm properties, while the flat side is modified with catechol groups able to form strong bonds with dentin. Even after 1 h of ultrasonication or 1000 rounds of thermal cycling, the dentin tubules are completely occluded by the JPs. Moreover, biofilm formation is not observed, and the area of living bacteria is less than 1% compared to the blank control and sodium fluoride (NaF)‐treated groups. In a rat model, the dentin tubules in the fixed specimens are completely occluded at day 3, much earlier than the occlusion obtained with commonly used NaF. These results demonstrate that JPs can provide a novel approach to the treatment of DH.

Preparation of CMC/ACP/PHMB nanocomposites and preliminary study on their antibacterial and remineralization functions

Caries is a chronic oral disease causing a series of complications. This study aims to develop a material that could remineralize demineralized enamel and simultaneously exert antibacterial effects. A carboxymethyl chitosan (CMC)/amorphous calcium phosphate (ACP)/polyhexamethylene biguanide hydrochloride (PHMB) nanocomposite was synthesized for the first time, and its stability, remineralization ability, and antibacterial properties were investigated in this study. PHMB has excellent antibacterial properties, was used as an additive to stabilize ACP. The enamel surface covered with CMC/ACP/PHMB showed a uniform layer with a similar elemental ratio to that of natural hydroxyapatite and the ratio of crystal diffraction peaks was close to that of natural enamel. The mechanical properties, including hardness and elastic modulus, of the enamel in all experimental groups were restored. The antibacterial effect of 240 mg/L CMC/ACP/PHMB was comparable to that of 0.12% CMC/ACP/chlorhexidine. This study provides a theoretical and experimental basis for the development of novel dual-function anticaries agent.

Nanomaterial-based synergistic strategies for combating dental caries: progress and perspectives

Dental caries, as the predominant global oral disease, remains a critical public health issue worldwide, particularly in socioeconomically disadvantaged communities. However, common caries prevention approaches (e.g., oral health education, mechanical plaque removal, and delivery of fluoride agents) are still insufficient for optimal caries management, and therefore, alternative regimens that can supplement existing strategies are highly warranted. Nanomaterials exhibit considerable potential in combating cariogenic pathogens and biofilms owing to their promising antimicrobial capacity, improved penetration into biofilms, targeted precision delivery, and versatile physicochemical properties. As unifunctional materials are limited in caries management, this review underscores the latest advancement in multifunctional anti-caries nanomaterials/nanomedicines. It highlights the cutting-edge materials developed or engineered to (i) incorporate diagnostic capabilities to prevent caries at an early stage, thus enhancing treatment efficiency, (ii) integrate mechanical "brushing" with anti-caries approaches to mechanochemically eradicate biofilms, (iii) exert antimicrobial/antibiofilm effects while preserving dental hard tissue. The current work also outlines future directions for optimizing nanosystems in the management of dental caries while emphasizing the need for innovative solutions to improve preventive and therapeutic efficacies.

The glycerol stabilized calcium phosphate cluster for rapid remineralization of tooth enamel by a water-triggered transformation

Remineralization is a common strategy for the repair of early demineralized tooth enamels, but the harsh dynamic oral environment often hampers its efficacy. Rapid remineralization is expected to address this challenge, however, the stabilizers of remineralization materials often resist their transformation required for repair. Here, by dissolving the ions of calcium and phosphate in glycerol-dominant solvents, we obtain the calcium phosphate clusters (1-2 nm), which are stabilized by glycerol (with high viscosity and affinity to clusters), but can perform a fast enamel repair via the water-triggered transformation in both static and dynamic environments. Upon the in vitro and in vivo (female Sprague-Dawley rats) studies, the clusters swiftly enter the nano-/micro-sized enamel defect sites, then form a compact hydroxyapatite repair layer within a short time (30 min, much faster than the conventional materials), and significantly recovers mechanical properties. This material is promising for large-scale preparation and applications in dental remineralization.

Unraveling the hidden complexity: Exploring dental tissues through single-cell transcriptional profiling

Understanding the composition and function of cells constituting tissues and organs is vital for unraveling biological processes. Single-cell analysis has allowed us to move beyond traditional methods of categorizing cell types. This innovative technology allows the transcriptional and epigenetic profiling of numerous individual cells, leading to significant insights into the development, homeostasis, and pathology of various organs and tissues in both animal models and human samples. In this review, we delve into the outcomes of major investigations using single-cell transcriptomics to decipher the cellular composition of mammalian teeth and periodontal tissues. The recent single-cell transcriptome-based studies have traced in detail the dental epithelium-ameloblast lineage and dental mesenchyme lineages in the mouse incisors and the tooth germ of both mice and humans; unraveled the microenvironment, the identity of niche cells, and cellular intricacies in the dental pulp; shed light on the molecular mechanisms orchestrating root formation; and characterized cellular dynamics of the periodontal ligament. Additionally, cellular components in dental pulps were compared between healthy and carious teeth at a single-cell level. Each section of this review contributes to a comprehensive understanding of tooth biology, offering valuable insights into developmental processes, niche cell identification, and the molecular secrets of the dental environment.

Hierarchically mimicking outer tooth enamel for restorative mechanical compatibility

Tooth enamel, and especially the outer tooth enamel, is a load-resistant shell that benefits mastication but is easily damaged, driving the need for enamel-restorative materials with comparable properties to restore the mastication function and protect the teeth. Synthesizing an enamel analog that mimics the components and hierarchical structure of natural tooth enamel is a promising way to achieve these comparable mechanical properties, but it is still challenging to realize. Herein, we fabricate a hierarchical enamel analog with comparable stiffness, hardness, and viscoelasticity as natural enamel by incorporating three hierarchies of outer tooth enamel based on hierarchical assembly of enamel-like hydroxyapatite hybrid nanowires with polyvinyl alcohol as a matrix. This enamel analog possesses enamel-similar inorganic components and a nanowire-microbundle-macroarray hierarchical structure. It exhibits toughness of 19.80 MPa m1/2, which is 3.4 times higher than natural tooth enamel, giving it long-term fatigue durability. This hierarchical design is promising for scalable production of enamel-restorative materials and for optimizing the mechanical performance of engineering composites.

Seriation of Enzyme-Functionalized Multilayers for the Design of Scalable Biomimetic Mineralized Structures

Biomimetic hydroxyapatites are widely explored for their potential applications in the repair of mineralized tissues, particularly dental enamel, which is acellular and, thus, not naturally reformed after damage. Enamel is formed with a highly-controlled hierarchical structure, which is difficult to replicate up to the macroscale. A biomimetic approach is thus warranted, based on the same principles that drive biomineralization in vivo. Herein, a strategy for the design of enamel-like architectures is described, utilizing enzymes embedded in polyelectrolyte multilayers to generate inorganic phosphate locally, and provide a favorable chemical environment for the nucleation and growth of minerals. Moreover, a method is proposed to build up seriated mineral layers with scalable thicknesses, continuous mineral growth, and tunable morphology. Results show the outstanding growth of cohesive mineral layers, yielding macroscopic standalone fluoride and/or carbonate-substituted hydroxyapatite materials with comparable crystal structure and composition to native human mineralized tissues. This strategy presents a promising path forward for the biomimetic design of biomineral materials, particularly relevant for restorative applications, with an exquisite level of synthetic control over multiple orders of magnitude.

Mineralized aggregates based on native protein phase transition for non-destructive diagnosis of seborrheic skin by surface-enhanced Raman spectroscopy

The non-homeostasis of sebum secretion by the sebaceous glands in a complicated microenvironment dramatically impacts the skin health of many people in the world. However, the complexity and hydrophobicity of sebum mean a lack of diagnostic tools, which makes it challenging to determine the reason behind cortical imbalances. Herein, a biomimetic mineralized aggregates (PTL@Au and PTB@Au) strategy has been proposed, which could obtain molecular information about sebum by surface-enhanced Raman spectroscopy (SERS). The breaking of disulfide bonds leads to changes in hydrogen bonding, which transform the natural protein into amyloid-like phase transition protein with β-sheets. It provides sites for the nucleation and crystallization of gold nanocrystals to build mineralized aggregates. The mineralized aggregates show robust adhesion stability at the interfaces of different materials through hydrogen bonding and electrostatic interactions. The stabilization, hydrophobicity (contact angle: 134°), and optical transmission (75%) of the structure could result in superior SERS performance for sebum analysis. It should be noted that this enables the sebum detection of clinical samples while ensuring safety. Such generalized bionic mineralization construction and diagnosis methods also serve as an advanced paradigm for a range of biomedical applications.

Unraveling Nanomaterials in Biomimetic Mineralization of Dental Hard Tissue: Focusing on Advantages, Mechanisms, and Prospects

The demineralization of dental hard tissue imposes considerable health and economic burdens worldwide, but an optimal method that can repair both the chemical composition and complex structures has not been developed. The continuous development of nanotechnology has created new opportunities for the regeneration and repair of dental hard tissue. Increasingly studies have reported that nanomaterials (NMs) can induce and regulate the biomimetic mineralization of dental hard tissue, but few studies have examined how they are involved in the different stages, let alone the relevant mechanisms of action. Besides their nanoscale dimensions and excellent designability, NMs play a corresponding role in the function of the raw materials for mineralization, mineralized microenvironment, mineralization guidance, and the function of mineralized products. This review comprehensively summarizes the advantages of NMs and examines the specific mineralization mechanisms. Design strategies to promote regeneration and repair are summarized according to the application purpose of NMs in the oral cavity, and limitations and development directions in dental hard tissue remineralization are proposed. This review can provide a theoretical basis to understand the interaction between NMs and the remineralization of dental hard tissue, thereby optimizing design strategy, rational development, and clinical application of NMs in the field of remineralization.

Cdc42 deletion yielded enamel defects by disrupting mitochondria and producing reactive oxygen species in dental epithelium

Developmental defects of enamel are common due to genetic and environmental factors before and after birth. Cdc42, a Rho family small GTPase, regulates prenatal tooth development in mice. However, its role in postnatal tooth development, especially enamel formation, remains elusive. Here, we investigated Cdc42 functions in mouse enamel development and tooth repair after birth. Cdc42 showed highly dynamic temporospatial patterns in the developing incisors, with robust expression in ameloblast and odontoblast layers. Strikingly, epithelium-specific Cdc42 deletion resulted in enamel defects in incisors. Ameloblast differentiation was inhibited, and hypomineralization of enamel was observed upon epithelial Cdc42 deletion. Proteomic analysis showed that abnormal mitochondrial components, phosphotransferase activity, and ion channel regulator activity occurred in the Cdc42 mutant dental epithelium. Reactive oxygen species accumulation was detected in the mutant mice, suggesting that abnormal oxidative stress occurred after Cdc42 depletion. Moreover, Cdc42 mutant mice showed delayed tooth repair and generated less calcified enamel. Mitochondrial dysfunction and abnormal oxygen consumption were evidenced by reduced Apool and Timm8a1 expression, increased Atp5j2 levels, and reactive oxygen species overproduction in the mutant repair epithelium. Epithelium-specific Cdc42 deletion attenuated ERK1/2 signaling in the labial cervical loop. Aberrant Sox2 expression in the mutant labial cervical loop after clipping might lead to delayed tooth repair. These findings suggested that mitochondrial dysfunction, up-regulated oxidative stress, and abnormal ion channel activity may be among multiple factors responsible for the observed enamel defects in Cdc42 mutant incisors. Overall, Cdc42 exerts multidimensional and pivotal roles in enamel development and is particularly required for ameloblast differentiation and enamel matrix formation.

Application of a calcium and phosphorus biomineralization strategy in tooth repair: a systematic review

Biomineralization is a natural process in which organisms regulate the growth of inorganic minerals to form biominerals with unique layered structures, such as bones and teeth, primarily composed of calcium and phosphorus. Tooth decay significantly impacts our daily lives, and the key to tooth regeneration lies in restoring teeth through biomimetic approaches, utilizing mineralization strategies or materials that mimic natural processes. This review delves into the types, properties, and transformations of calcium and phosphorus minerals, followed by an exploration of the mechanisms behind physiological and pathological mineralization in living organisms. It summarizes the mechanisms and commonalities of biomineralization and discusses the advancements in dental biomineralization research, guided by insights into calcium and phosphorus mineral biomineralization. This review concludes by addressing the current challenges and future directions in the field of dental biomimetic mineralization.

Self-assembled branched polypeptides as amelogenin mimics for enamel repair

The regeneration of demineralized enamel holds great significance in the treatment of dental caries. Amelogenin (Ame), an essential protein for mediating natural enamel growth, is no longer secreted after enamel has fully matured in childhood. Although biomimetic mineralization based on peptides or proteins has made significant progress, easily accessible, low-cost, biocompatible and highly effective Ame mimics are still lacking. Herein, we construct a series of amphiphilic branched polypeptides (CAMPs) by facile coupling of the Ame's C-terminal segment and poly(γ-benzyl-L-glutamate), which serves to simulate the Ame's hydrophobic N-terminal segment. Among them, CAMP15 is the best biomimetic mineralization template with great self-assembly performance to guide the oriented crystallization of hydroxyapatite and is capable of inhibiting the adhesion of Streptococcus mutans and Staphylococcus aureus on the enamel surfaces. This work highlights the potential application of amphiphilic branched polypeptide as Ame mimics in repairing defected enamel, providing a promising strategy for prevention and treatment of dental caries.

Recent Advances in Functional Hydrogels for Treating Dental Hard Tissue and Endodontic Diseases

Oral health is the basis of human health, and almost everyone has been affected by oral diseases. Among them, endodontic disease is one of the most common oral diseases. Limited by the characteristics of oral biomaterials, clinical methods for endodontic disease treatment still face large challenges in terms of reliability and stability. The hydrogel is a kind of good biomaterial with an adjustable 3D network structure, excellent mechanical properties, and biocompatibility and is widely used in the basic and clinical research of endodontic disease. This Review discusses the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment. The emphasis is on the working principles and therapeutic effects of treating different diseases with functional hydrogels. Finally, the challenges and opportunities of hydrogels in oral clinical applications are discussed and proposed. Some viewpoints about the possible development direction of functional hydrogels for oral health in the future are also put forward. Through systematic analysis and conclusion of the recent advances in functional hydrogels for dental hard tissue and endodontic disease treatment, this Review may provide significant guidance and inspiration for oral disease and health in the future.

Guidelines derived from biomineralized tissues for design and construction of high-performance biomimetic materials: from weak to strong

Living organisms in nature have undergone continuous evolution over billions of years, resulting in the formation of high-performance fracture-resistant biomineralized tissues such as bones and teeth to fulfill mechanical and biological functions, despite the fact that most inorganic biominerals that constitute biomineralized tissues are weak and brittle. During the long-period evolution process, nature has evolved a number of highly effective and smart strategies to design chemical compositions and structures of biomineralized tissues to enable superior properties and to adapt to surrounding environments. Most biomineralized tissues have hierarchically ordered structures consisting of very small building blocks on the nanometer scale (nanoparticles, nanofibers or nanoflakes) to reduce the inherent weaknesses and brittleness of corresponding inorganic biominerals, to prevent crack initiation and propagation, and to allow high defect tolerance. The bioinspired principles derived from biomineralized tissues are indispensable for designing and constructing high-performance biomimetic materials. In recent years, a large number of high-performance biomimetic materials have been prepared based on these bioinspired principles with a large volume of literature covering this topic. Therefore, a timely and comprehensive review on this hot topic is highly important and contributes to the future development of this rapidly evolving research field. This review article aims to be comprehensive, authoritative, and critical with wide general interest to the science community, summarizing recent advances in revealing the formation processes, composition, and structures of biomineralized tissues, providing in-depth insights into guidelines derived from biomineralized tissues for the design and construction of high-performance biomimetic materials, and discussing recent progress, current research trends, key problems, future main research directions and challenges, and future perspectives in this exciting and rapidly evolving research field.

Biomimetic Self-Maturation Mineralization System for Enamel Repair

Enamel repair is crucial for restoring tooth function and halting dental caries. However, contemporary research often overlooks the retention of organic residues within the repair layer, which hinders the growth of dense crystals and compromises the properties of the repaired enamel. During the maturation of natural enamel, the organic matrix undergoes enzymatic processing to facilitate further crystal growth, resulting in a highly mineralized tissue. Inspired by this process, a biomimetic self-maturation mineralization system is developed, comprising ribonucleic acid-stabilized amorphous calcium phosphate (RNA-ACP) and ribonuclease (RNase). The RNA-ACP induces initial mineralization in the form of epitaxial crystal growth, while the RNase present in saliva automatically triggers a biomimetic self-maturation process. The mechanistic study further indicates that RNA degradation prompts conformational rearrangement of the RNA-ACP, effectively excluding the organic matter introduced earlier. This exclusion process promotes lateral crystal growth, resulting in the generation of denser enamel-like apatite crystals that are devoid of organic residues. This strategy of eliminating organic residues from enamel crystals enhances the mechanical and physiochemical properties of the repaired enamel. The present study introduces a conceptual biomimetic mineralization strategy for effective enamel repair in clinical practice and offers potential insights into the mechanisms of biomineral formation.

Tubular Nanoclay-Enhanced Calcium Phosphate Mineralization and Assembly to Impart High Stiffness and Antimicrobial Properties

Achieving superior mechanical properties of composite materials in artificially engineered materials is a great challenge due to technical bottlenecks in the size and morphological modulation of inorganic nanominerals. Hence, a "bioprocess-inspired fabrication" is proposed to create multilayered organic-inorganic columnar structures. The sequential assembly of halloysite nanotubes (HNTs), polyelectrolytes (PAAs), and calcium phosphates (CaPs) results in organic-inorganic structures. PAA plays a crucial role in controlling the formation of CaP, guiding it into amorphous particles with smaller nanosizes. The introduction of HNT induces the assembly and maturation of CaP-PAA, leading to the formation of a highly crystalline hydroxyapatite. Poly(vinyl alcohol) was then woven into HNT-encapsulated hydroxyapatite nanorods, resulting in composite materials with basic hierarchical structures across multiple scales. The fabricated composite exhibits exceptional hardness (4.27 ± 0.33 GPa) and flexural strength (101.25 ± 1.72 MPa), surpassing those of most previously developed biological hard tissue materials. Additionally, the composite demonstrates effective antibacterial properties and corrosion resistance, attributed to the dense crystalline phase of CaP. This innovative approach showcases the potential of clay minerals, particularly HNT, in the advancement of biomaterial design. The outstanding mechanical and antimicrobial properties of clay-based composites make them a promising candidate for applications in hard tissue repair, offering versatility in biomedicine and engineering.

Protein-based bioactive coatings: from nanoarchitectonics to applications

Protein-based bioactive coatings have emerged as a versatile and promising strategy for enhancing the performance and biocompatibility of diverse biomedical materials and devices. Through surface modification, these coatings confer novel biofunctional attributes, rendering the material highly bioactive. Their widespread adoption across various domains in recent years underscores their importance. This review systematically elucidates the behavior of protein-based bioactive coatings in organisms and expounds on their underlying mechanisms. Furthermore, it highlights notable advancements in artificial synthesis methodologies and their functional applications in vitro. A focal point is the delineation of assembly strategies employed in crafting protein-based bioactive coatings, which provides a guide for their expansion and sustained implementation. Finally, the current trends, challenges, and future directions of protein-based bioactive coatings are discussed.

Synthesis and functionalization of scalable and versatile 2D protein films via amyloid-like aggregation

Two-dimensional (2D) protein films can be used to modify the properties of surfaces, and find applications predominantly in the fields of biomaterials, lithography, optics and electronics. However, it is difficult to produce scalable homogeneous and robust protein films with an easy, low-cost, green and efficient method. Further challenges include encapsulating and releasing functional building blocks in the film without inactivating them, and maintaining or improving the bioactivities of proteins used for the formation of the films. Here we detail the process to prepare large 2D protein films with user-defined features and structures via the amyloid-like aggregation of commonly synthesized proteins. These films can be synthesized at meter scales, have high interface adhesion, high functional expansibility and tunable functional properties, obtained by controlling the position of the disulfide bond breakage. For example, we can retain or even enhance the natural antibacterial, biomineralization and antifouling activity of proteins involved in film formation, and the properties can also be expanded through the physical blending or chemical grafting of additional functional blocks on the surface of the film. A 2D protein film can be prepared in ~3 h using four alternative coating techniques: immersion, transfer, hydrogel stamping and spraying. The characterization process of the film requires ~5 d. The procedure can be carried out by users with basic expertise in materials science.

Bioinspired Multiscale Mineralization: From Fundamentals to Potential Applications

The wondrous and imaginative designs of nature have always been an inexhaustible treasure trove for material scientists. Throughout the long evolutionary process, biominerals with hierarchical structures possess some specific advantages such as outstanding mechanical properties, biological functions, and sensing performances, the formation of which (biomineralization) is delicately regulated by organic component. Provoked by the subtle structures and profound principles of nature, bioinspired functional minerals can be designed with the participation of organic molecules. Because of the designable morphology and functions, multiscale mineralization has attracted more and more attention in the areas of medicine, chemistry, biology, and material science. This review provides a summary of current advancements in this extending topic. The mechanisms underlying mineralization is first concisely elucidated. Next, several types of minerals are categorized according to their structural characteristic, as well as the different potential applications of these materials. At last, a comprehensive overview of future developments for bioinspired multiscale mineralization is given. Concentrating on the mechanism of fabrication and broad application prospects of multiscale mineralization, the hope is to provide inspirations for the design of other functional materials.

Engineering Immunomodulatory Stents Using Zinc Ion-Lysozyme Nanoparticle Platform for Vascular Remodeling

Rapid endothelialization of cardiovascular materials can enhance the vascular remodeling performance. In this work, we developed a strategy for amyloid-like protein-assembly-mediated interfacial engineering to functionalize a biomimetic nanoparticle coating (BMC). Various groups (e.g., hydroxyl and carboxyl) on the BMC are responsible for chelating Zn2+ ions at the stent interface, similar to the glutathione peroxidase-like enzymes found in vivo. This design could reproduce the release of therapeutic nitric oxide gas (NO) and an aligned microenvironment nearly identical with that of natural vessels. In a rabbit abdominal aorta model, BMC-coated stents promoted vascular healing through rapid endothelialization and the inhibition of intimal hyperplasia in the placement sites at 4, 12, and 24 weeks. Additionally, better anticoagulant activity and immunomodulation in the BMC stents were also confirmed, and vascular healing was mainly dependent on cell signaling through the cyclic guanosine monophosphate-protein kinase G (cGMP-PKG) cascade. Overall, a metal-polypeptide-coated stent was developed on the basis of its detailed molecular mechanism of action in vascular remodeling.

Physicochemical understanding of biomineralization by molecular vibrational spectroscopy: From mechanism to nature

The process and mechanism of biomineralization and relevant physicochemical properties of mineral crystals are remarkably sophisticated multidisciplinary fields that include biology, chemistry, physics, and materials science. The components of the organic matter, structural construction of minerals, and related mechanical interaction, etc., could help to reveal the unique nature of the special mineralization process. Herein, the paper provides an overview of the biomineralization process from the perspective of molecular vibrational spectroscopy, including the physicochemical properties of biomineralized tissues, from physiological to applied mineralization. These physicochemical characteristics closely to the hierarchical mineralization process include biological crystal defects, chemical bonding, atomic doping, structural changes, and content changes in organic matter, along with the interface between biocrystals and organic matter as well as the specific mechanical effects for hardness and toughness. Based on those observations, the special physiological properties of mineralization for enamel and bone, as well as the possible mechanism of pathological mineralization and calcification such as atherosclerosis, tumor micro mineralization, and urolithiasis are also reviewed and discussed. Indeed, the clearly defined physicochemical properties of mineral crystals could pave the way for studies on the mechanisms and applications.

Functional Covalent Organic Framework (COF) Nanoparticles for Biomimic Mineralization and Bacteria Inhabitation

Biomimic mineralization of hard tissues with hierarchical structures is a challenging task, while designing multifunctional materials possessing both the ability of biomimic mineralization and drug delivery is even more difficult. Herein, inspired by the multilevel structure and mineralization ability of amelogenin, a novel carboxyl-functionalized covalent organic framework (COF) nanosphere material was designed and synthesized, which exhibited a significant biomimetic remineralization ability as demonstrated on SiO2 glass, Ti6Al4V, and an acid-etched enamel surface. Furthermore, the nanoporous structure also enables the COF nanospheres to serve as a drug delivery system for the controlled release of antibacterial drugs. This work provides a promising strategy for the design of multifunctional biomimic materials.

A Remineralizing and Antibacterial Coating for Arresting Caries

Dental caries is a dynamic disease induced by the unbalance between demineralization of dental hard tissues caused by biofilm and remineralization of them; however, although various effective remineralization methods have been well documented, it is a challenge to reestablish the balance by enhancing remineralization alone while ignoring the antibacterial therapy. Therefore, the integration of remineralizing and antibacterial technologies offers a promising strategy to halt natural caries progression in clinical practice. Here, the conception of interrupting dental caries (IDC) was proposed based on the development of dual-functional coating with remineralizing and antibacterial properties. In this study, bovine serum albumin (BSA) loaded octenidine (OCT) successfully to form a BSA-OCT composite. Subsequently, through fast amyloid-like aggregation, the phase-transited BSA-OCT (PTB-OCT) coating can be covered on teeth, resin composite, or sealant surfaces in 30 min by a simple smearing process. The PTB-OCT coating showed satisfactory effects in promoting the remineralization of demineralized enamel and dentin in vitro. Moreover, this coating also exerted significant acid-resistance stability and anti-biofilm properties. Equally importantly, this coating exhibited promising abilities in reducing the microleakage between the tooth and resin composite in vitro and preventing primary and secondary caries in vivo. In conclusion, this novel dual-functional PTB-OCT coating could reestablish the balance between demineralization and remineralization in the process of caries, thereby potentially preventing or arresting caries.

Rational Designs of Biomaterials for Combating Oral Biofilm Infections

Oral biofilms, which are also known as dental plaque, are the culprit of a wide range of oral diseases and systemic diseases, thus contributing to serious health risks. The manner of how to achieve good control of oral biofilms has been an increasing public concern. Novel antimicrobial biomaterials with highly controllable fabrication and functionalization have been proven to be promising candidates. However, previous reviews have generally emphasized the physicochemical properties, action mode, and application effectiveness of those biomaterials, whereas insufficient attention has been given to the design rationales tailored to different infection types and application scenarios. To offer guidance for better diversification and functionalization of anti-oral-biofilm biomaterials, this review details the up-to-date design rationales in three aspects: the core strategies in combating oral biofilm, as well as the biomaterials with advanced antibiofilm capacity and multiple functions based on the improvement or combination of the abovementioned antimicrobial strategies. Thereafter, insights on the existing challenges and future improvement of biomaterial-assisted oral biofilm treatments are proposed, hoping to provide a theoretical basis and reference for the subsequent design and application of antibiofilm biomaterials.

An epigallocatechin gallate-amorphous calcium phosphate nanocomposite for caries prevention and demineralized enamel restoration

Biomineralization with amorphous calcium phosphate (ACP) is a highly effective strategy for caries prevention and defect restoration. The identification and interruption of cariogenic biofilm formation during remineralization remains a challenge in current practice. In this study, an epigallocatechin gallate (EGCG)-ACP functional nanocomposite was developed to prevent and restore demineralization by integrating the antibacterial property of EGCG and the remineralization effect of ACP. The synthesized EGCG-ACP showed good biocompatibility with L-929 ​cells and human gingival fibroblasts. Under neutral conditions, the sustained release of ACP from EGCG-ACP restored the microstructure and mechanical properties of demineralized enamel. Under acidic conditions, protonated EGCG released from EGCG-ACP exerted a strong antibacterial effect, and the ACP release rate doubled within 4 ​h, resulting in the prevention of demineralization in the presence of cariogenic bacteria. The pH-responsive features of EGCG-ACP to promote the protonation of EGCG and ACP release facilitated its performance in remineralization effect to overcome the difficulty of restoring demineralized enamel in a cariogenic acidic environment, which was evidenced by the in vivo experiment carried out in a rat oral cariogenic environment. The results of this study indicate the potential of EGCG-ACP for the prevention of enamel demineralization and provide a theoretical basis its application in populations with high caries risk.

Cementum is key to periodontal tissue regeneration: A review on apatite microstructures for creation of novel cementum-based dental implants

The cementum is the outermost layer of hard tissue covering the dentin within the root portion of the teeth. It is the only hard tissue with a specialized structure and function that forms a part of both the teeth and periodontal tissue. As such, cementum is believed to be critical for periodontal tissue regeneration. In this review, we discuss the function and histological structure of the cementum to promote crystal engineering with a biochemical approach in cementum regenerative medicine. We review the microstructure of enamel and bone while discussing the mechanism underlying apatite crystal formation to infer the morphology of cementum apatite crystals and their complex structure with collagen fibers. Finally, the limitations of the current dental implant treatments in clinical practice are explored from the perspective of periodontal tissue regeneration. We anticipate the possibility of advancing periodontal tissue regenerative medicine via cementum regeneration using a combination of material science and biochemical methods.

Synthetic extracellular matrices with function-encoding peptides

The communication of cells with their surroundings is mostly encoded in the epitopes of structural and signalling proteins present in the extracellular matrix (ECM). These peptide epitopes can be incorporated in biomaterials to serve as function-encoding molecules to modulate cell-cell and cell-ECM interactions. In this Review, we discuss natural and synthetic peptide epitopes as molecular tools to bioengineer bioactive hydrogel materials. We present a library of functional peptide sequences that selectively communicate with cells and the ECM to coordinate biological processes, including epitopes that directly signal to cells, that bind ECM components that subsequently signal to cells, and that regulate ECM turnover. We highlight how these epitopes can be incorporated in different biomaterials as individual or multiple signals, working synergistically or additively. This molecular toolbox can be applied in the design of biomaterials aimed at regulating or controlling cellular and tissue function, repair and regeneration.

Mussel-Inspired Caries Management Strategy: Constructing a Tribioactive Tooth Surface with Remineralization, Antibiofilm, and Anti-inflammation Activity

Dental caries is a common chronic oral disease in humans resulting from tooth demineralization caused by acid production of bacterial plaque, which leads to the destruction of enamel and dentin and oral inflammation. However, it is still a challenge that the function of natural active ingredients in currently available oral care products is not comprehensive, especially the lack of remineralization. Here, inspired by the strong biological adhesion ability of mussels and ancient oral disease plant therapy, a multifunctional strategy is proposed to construct a bioactive tooth surface to treat dental caries. It has been demonstrated that the Turkish gall extract (TGE) can inhibit adhesion of cariogenic bacteria Streptococcus mutans and Actinomyces viscosus and destroy biofilms on the tooth surface. Meanwhile, TGE can reduce the expression of inflammatory factors. Notably, the TGE coating can induce the growth of hydroxyapatite (HAP) crystals in vivo and in vitro, recovering the enamel mechanical properties under normal oral conditions. MD simulations interpreted the adsorption mechanism by which the hydroxyl groups in TGE bind to phosphate group (PO₄^3-) on the tooth surface, attracting calcium ions (Ca²⁺) as nucleation sites for remineralization. This work underlines the importance of TGE coating in remineralization, antibiofilm, and anti-inflammation activity as a promising strategy for dental caries.

A near-infrared probe for detecting and interposing amyloid beta oligomerization in early Alzheimer's disease

BACKGROUND

The misfolding and deposition of amyloid beta (Aβ) in human brain is the main hallmark of Alzheimer's disease (AD) pathology. One of the drivers of Alzheimer´s pathogenesis is the production of soluble oligomeric Aβ, which could potentially serve as a biomarker of AD.

METHODS

Given that the diphenylalanine (FF) at the C-terminus of Aβ fragments plays a key role in inducing the AD pathology, based on the hydrophobic structure of FF, we synthesized a near-infrared BF2-dipyrrolmethane fluorescent imaging probe (NB) to detect both soluble and insoluble Aβ.

RESULTS

We found that NB not only binds Aβ, particularly oligomeric Aβ, but also interposes self-assembly of Aβ through π-π interaction between NB and FF.

CONCLUSION

This work holds great promise in the early detection of AD and may also provide an innovative approach to decelerate and even halt AD onset and progression.

Recombinant amelogenin peptide TRAP promoting remineralization of early enamel caries: An in vitro study

Objective: To explore the regulatory effect of recombinant amelogenin peptide TRAP on the remineralization of early enamel carious lesions. Methods: Forty-eight bovine enamel blocks that prepared initial lesions in vitro were split at random into four groups for immersion treatment for 12 days: 1) remineralizing medium; 2) studied peptide 1 (consisting of the N- and C-termini of porcine amelogenin) + remineralizing medium; 3) studied peptide 2 (TRAP) + remineralizing medium; 4) fluoride + remineralizing medium. After demineralization and remineralization immersion, each specimen's mean mineral loss and lesion depth were measured using micro-computed tomography (micro-CT). The changes in lesion depth (∆LD) and mineral gain (∆Z) were computed following remineralization. The enamel samples were then cut into sections and examined with polarized light microscopy (PLM). The cross-section morphology was observed by scanning electron microscopy (SEM). The crystal phase was analyzed by an X-ray micro-diffractometer (XRD). The calcium-binding properties were determined using isothermal titration calorimetry (ITC). Results: Micro-CT analysis revealed a significant reduction in mineral loss in the four groups following the remineralization treatment (p < 0.05). The treatment with fluoride resulted in the greatest ∆Z and ∆LD, whereas the treatment with a remineralizing medium showed the least ∆Z and ∆LD among all groups. The ∆Z and ∆LD of the studied peptide 1 and studied peptide 2 groups were greater than those of the remineralizing medium group. However, there was no significant difference between the studied peptide 1 and studied peptide 2 groups (p > 0.05). All of the samples that the PLM analyzed had a thickening of the surface layer. A negative birefringent band changed in the lesion's body. The SEM displayed that minerals were formed in all four groups of samples. The XRD results indicated that the products of remineralization of the studied peptide were hydroxyapatite crystals (HA). ITC showed that there were two binding modes between the calcium and peptide TRAP. Conclusion: This study confirmed the potential of the recombinant amelogenin peptide TRAP as a key functional motif of amelogenin protein for enamel remineralization and provided a promising biomaterial for remineralization in initial enamel carious lesion treatment.

Tooth Diversity Underpins Future Biomimetic Replications

Although the evolution of tooth structure seems highly conserved, remarkable diversity exists among species due to different living environments and survival requirements. Along with the conservation, this diversity of evolution allows for the optimized structures and functions of teeth under various service conditions, providing valuable resources for the rational design of biomimetic materials. In this review, we survey the current knowledge about teeth from representative mammals and aquatic animals, including human teeth, herbivore and carnivore teeth, shark teeth, calcite teeth in sea urchins, magnetite teeth in chitons, and transparent teeth in dragonfish, to name a few. The highlight of tooth diversity in terms of compositions, structures, properties, and functions may stimulate further efforts in the synthesis of tooth-inspired materials with enhanced mechanical performance and broader property sets. The state-of-the-art syntheses of enamel mimetics and their properties are briefly covered. We envision that future development in this field will need to take the advantage of both conservation and diversity of teeth. Our own view on the opportunities and key challenges in this pathway is presented with a focus on the hierarchical and gradient structures, multifunctional design, and precise and scalable synthesis.

Advanced materials and technologies for oral diseases

Oral disease, as a class of diseases with very high morbidity, brings great physical and mental damage to people worldwide. The increasing burden and strain on individuals and society make oral diseases an urgent global health problem. Since the treatment of almost all oral diseases relies on materials, the rapid development of advanced materials and technologies has also promoted innovations in the treatment methods and strategies of oral diseases. In this review, we systematically summarized the application strategies in advanced materials and technologies for oral diseases according to the etiology of the diseases and the comparison of new and old materials. Finally, the challenges and directions of future development for advanced materials and technologies in the treatment of oral diseases were refined. This review will guide the fundamental research and clinical translation of oral diseases for practitioners of oral medicine.

Synthesis of Micro-/Nanohydroxyapatite Assisted by the Taylor-Couette Flow Reactor

Hydroxyapatite (HAP) has received increasing attention as an essential chemical product with good biocompatibility and adsorption properties. Generally, amorphous calcium phosphate (ACP) was generated first in the reactor and transformed into HAP after a period of crystallization. In this work, a series of Taylor-Couette flow reactors with different inner diameters were designed to assist in synthesizing HAP micro-/nanocrystals. ACP was obtained in a Taylor-Couette flow reactor at Re = 247 and successfully transformed into needle-like HAP crystals with a length of about 200 nm and a uniform particle size distribution after crystallization transformation. The yield of a single reactor can reach 2.16 kg per day. The finite element analysis results and time-space diagram of flow pattern variation showed that the Taylor-Couette flow reactor could improve the mixing behavior and the flow field distribution. The Taylor-Couette flow reactor provides a valuable reference for synthesizing inorganic micro-/nanomaterials.

Fast Construction of Biomimetic Organic-Inorganic Interface by Crosslinking of Calcium Phosphate Oligomers: A Strategy for Instant Regeneration of Hard Tissue

The organic-inorganic structure in biological hard tissues ensures their marvelous characteristics but these hybrids are easily destroyed by the demineralization of inorganic components, e.g., the damage of dentin. Current clinical materials for hard tissue regeneration commonly act as "fillers" and their therapeutic effect is limited by the failures of biological-linked organic-inorganic interface reconstruction. Herein, a fast in situ crosslinking of calcium phosphate oligomers (CPOs) on collagen matrixes for efficient organic-inorganic interface re-construction, which can result in a biomimetic hybrid, is demonstrated. By using damaged dentin as an example, the inorganic ionic crosslinking can instantly infiltrate into the dentin matrix to rebuild a dense and continuous calcium phosphate-collagen hybrid within only 5 min, where the structurally integrated organic-inorganic interface is identical to natural dentin. As a result, the damaged dentin can be fully recovered to a healthy one, which is superior to any current dentin treatments. The fast construction of biomimetic hybrid by inorganic ionic crosslinking provides a promising strategy for hard tissue repair and follows great potentials of CPOs as advanced biomedical materials in future.

Caries Management with Non-Metallic Nanomaterials: A Systematic Review

BACKGROUND

Non-metallic nanomaterials do not stain enamel or dentin. Most have better biocompatibility than metallic nanomaterials do for management of dental caries.

OBJECTIVE

The objective of this study is to review the types, properties and potential uses of non-metallic nanomaterials systematically for managing dental caries.

METHODS

Two researchers independently performed a literature search of publications in English using PubMed, Scopus and Web of Science. The keywords used were (nanoparticles OR nanocomposites OR nanomaterials) AND (caries OR tooth decay). They screened the titles and abstracts to identify potentially eligible publications of original research reporting non-metallic nanomaterials for caries management. Then, they retrieved and studied the full text of the identified publications for inclusion in this study.

RESULTS

Out of 2497 resulting publications, this study included 75 of those. The non-metallic nanomaterials used in these publications were categorized as biological organic nanomaterials (n=45), synthetic organic nanomaterials (n=15), carbon-based nanomaterials (n=13) and selenium nanomaterials (n=2). They inhibited bacteria growth and/or promoted remineralization. They could be incorporated in topical agents (29/75, 39%), dental adhesives (11/75, 15%), restorative fillers (4/75, 5%), dental sealant (3/75, 4%), oral drugs (3/75, 4%), toothpastes (2/75, 3%) and functional candies (1/75, 1%). Other publications (22/75, 29%) do not mention specific applications. However, most publications (67/75, 89%) were in vitro studies. Six publications (6/75, 8%) were animal studies, and only two publications (2/75, 3%) were clinical studies.

CONCLUSION

The literature showed non-metallic nanomaterials have antibacterial and/or remineralising properties. The most common type of non-metallic nanomaterials for caries management is organic nanomaterials. Non-metallic nanomaterials can be incorporated into dental sealants, toothpaste, dental adhesives, topical agents and even candies and drugs. However, the majority of the publications are in vitro studies, and only two publications are clinical studies.

Role of Inorganic Amorphous Constituents in Highly Mineralized Biomaterials and Their Imitations

A highly mineralized biomaterial is one kind of biomaterial that usually possesses a high content of crystal minerals and hierarchical microstructure, exhibiting excellent mechanical properties to support the living body. Recent studies have revealed the presence of inorganic amorphous constituents (IAC) either during the biomineralization process or in some mature bodies, which heavily affects the formation and performance of highly mineralized biomaterials. These results are surprising given the preceding intensive research into the microstructure design of these materials. Herein, we highlight the role of IAC in highly mineralized biomaterials. We focused on summarizing works demonstrating the presence or phase transformation of IAC and discussed in detail how IAC affects the formation and performance of highly mineralized biomaterials. Furthermore, we described some imitations of highly mineralized biomaterials that use IAC as the synthetic precursor or final strengthening phase. Finally, we briefly summarized the role of IAC in biomaterials and provided an outlook on the challenges and opportunities for future IAC and IAC-containing bioinspired materials researches.

Bioinspired Anti-demineralization Enamel Coating for Orthodontics

White spot lesions and enamel cracks are the 2 most prominent diseases that occur after orthodontic treatment and are caused by enamel demineralization from accumulated bacterial biofilms and/or enamel damage caused by the removal of residual adhesive after bracket debonding. Inspired by the self-assembled amelogenin nanoribbons in enamel, we developed an enamel coating with a self-assembling antimicrobial peptide, D-GL13K, to simultaneously reduce demineralization and residual adhesive. The self-assembled amphiphilic nanoribbons significantly increased the hydrophobicity of the etched enamel, which reduced the permeability of the coated enamel surfaces as desired. The antimicrobial activity of this coating was evaluated against Streptococcus mutans by colony-forming unit counting and live/dead assays. The anti-demineralization effect was demonstrated by the reduced demineralization depth analyzed by optical coherence tomography and the increased Vickers hardness. The coatings did not reduce the shear bond strength but significantly reduced the adhesive remnant index score. This bioinspired enamel coating may provide a new strategy for preventing white spot lesions and enamel cracks after orthodontic treatment.

Amyloid-Mediated Remineralization in Pit and Fissure for Caries Preventive Therapy

The pits and fissures of teeth have high caries susceptibility, and sealing these areas is considered as an effective method to prevent caries. However, long-term caries prophylaxis cannot be maintained because of the negative effects derived from the technical sensitivity and disadvantages of sealing materials. Herein, a new strategy is proposed to occlude fossae by amyloid-mediated biomimetic remineralization. In contrast to conventional inward blocking from the outside of fossae, amyloid-mediated biomimetic mineralization delivers an amyloid-like protein nanofilm into the deepest zone of the fossae and induces the formation of remineralized enamel inside. Such assembly from lysozyme conjugated with poly (ethylene glycol) enriches the interface with strongly bonded ionsand directs in situ nucleation to achieve enamel epitaxial growth. Not only is the structure of the enamel-like crystalline hydroxyapatite layer but also its mechanical stability is similar to that of natural enamel. Furthermore, the layer shows good biocompatibility and antibacterial properties. On the basis of the findings, it is demonstrated that amyloid-like protein aggregation may provide an enamel remineralization strategy to modify the current clinically available methods of pit and fissure sealing and shows great promise in preventing caries.

Advanced materials for enamel remineralization

Dental caries, a chronic and irreversible disease caused by caries-causing bacteria, has been listed as one of the three major human diseases to be prevented and treated. Therefore, it is critical to effectively stop the development of enamel caries. Remineralization treatment can control the progression of caries by inhibiting and reversing enamel demineralization at an early stage. In this process, functional materials guide the deposition of minerals on the damaged enamel, and the structure and hardness of the enamel are then restored. These remineralization materials have great potential for clinical application. In this review, advanced materials for enamel remineralization were briefly summarized, furthermore, an outlook on the perspective of remineralization materials were addressed.

Zwitterionic/phosphonate copolymer coatings endow excellent antifouling properties and robust re-mineralization ability of dentine substrates

Inhibition of biofilm formation and induction of the re-mineralization of damaged dental tissues are two major strategies to combat dental hypersensitivity (DH). However, single component synthetic materials normally cannot fulfil these two functions during the repairing of damaged dental tissues. Here, we report zwitterionic phosphorylcholine based polymers to be a new type of dual functional coating for the repairing of DH. Zwitterionic/phosphonate copolymers, p(DEMMP-co-MPC), bearing varied zwitterionic contents (95 and 75 mol%) were prepared through conventional radical copolymerization. ¹H NMR spectroscopy clearly indicated the precise preparation of the copolymers. The copolymers can be easily coated on dentine substrates based on the high affinity between the phosphonate group and the calcium phosphate minerals of the dentine substrates, as evidenced by XPS and water contact angle measurements. Antifouling evaluations indicated that zwitterionic coating can efficiently inhibit protein adsorption (BSA, egg white, and milk, by 85%) and bacterial adhesion (by 97.1%) on dentine substrates. Furthermore, in vitro and in vivo experiments consistently indicated that the zwitterionic coating could not only induce the robust re-mineralization of dentine surfaces, but also template the extensive re-mineralization of dentine tubules to a similar level of pristine dentine. Both the antifouling properties and the re-mineralization potency are positively correlated with the content of zwitterionic pMPC in the coating copolymer. These findings may provide the zwitterionic phosphorylcholine based materials to be a promising candidate to treat dental hypersensitivity and other related dental diseases.

Engineering DNA-Guided Hydroxyapatite Bulk Materials with High Stiffness and Outstanding Antimicrobial Ability for Dental Inlay Applications

Programmable base pair interactions at the nanoscale make DNA an attractive scaffold for forming hydroxyapatite (HAP) nanostructures. However, engineering macroscale HAP mineralization guided by DNA molecules remains challenging. To overcome this issue, a facile strategy is developed for the fabrication of ultrastiff DNA-HAP bulk composites. The electrostatic complexation of DNA and a surfactant with a quaternary ammonium salt group enables the formation of long-range ordered scaffolds using electrospinning. The growth of 1D and 2D HAP minerals is thus realized by this DNA template at a macroscale. Remarkably, the as-prepared DNA-HAP composites exhibit an ultrahigh Young's modulus of ≈25 GPa, which is comparable to natural HAP and superior to most artificial mineralized composites. Furthermore, a new type of dental inlay with outstanding antibacterial properties is developed using the stiff DNA-HAP. The encapsulated quaternary ammonium group within the dense HAP endows the composite with long-lasting and local antibacterial activity. Therefore, this new type of super-stiff biomaterial holds great potential for oral prosthetic applications.

An amelogenin-based peptide hydrogel promoted the odontogenic differentiation of human dental pulp cells

Amelogenin can induce odontogenic differentiation of human dental pulp cells (HDPCs), which has great potential and advantages in dentine-pulp complex regeneration. However, the unstability of amelogenin limits its further application. This study constructed amelogenin self-assembling peptide hydrogels (L-gel or D-gel) by heating-cooling technique, investigated the effects of these hydrogels on the odontogenic differentiation of HDPCs and explored the underneath mechanism. The critical aggregation concentration, conformation, morphology, mechanical property and biological stability of the hydrogels were characterized, respectively. The effects of the hydrogels on the odontogenic differentiation of HDPCs were evaluated via alkaline phosphatase activity measurement, quantitative reverse transcription polymerase chain reaction, western blot, Alizarin red staining and scanning electron microscope. The mechanism was explored via signaling pathway experiments. Results showed that both the L-gel and D-gel stimulated the odontogenic differentiation of HDPCs on both Day 7 and Day 14, while the D-gel showed the highest enhancement effects. Meanwhile, the D-gel promoted calcium accumulation and mineralized matrix deposition on Day 21. The D-gel activated MAPK-ERK1/2 pathways in HDPCs and induced the odontogenic differentiation via ERK1/2 and transforming growth factor/smad pathways. Overall, our study demonstrated that the amelogenin peptide hydrogel stimulated the odontogenic differentiation and enhanced mineralization, which held big potential in the dentine-pulp complex regeneration.

Application of Amorphous Calcium Phosphate Agents in the Prevention and Treatment of Enamel Demineralization

Enamel demineralization, as a type of frequently-occurring dental problem that affects both the health and aesthetics of patients, is a concern for both dental professionals and patients. The main chemical composition of the enamel, hydroxyapatite, is easy to be dissolved under acid attack, resulting in the occurrence of enamel demineralization. Among agents for the preventing or treatment of enamel demineralization, amorphous calcium phosphate (ACP) has gradually become a focus of research. Based on the nonclassical crystallization theory, ACP can induce the formation of enamel-like hydroxyapatite and thereby achieve enamel remineralization. However, ACP has poor stability and tends to turn into hydroxyapatite in an aqueous solution resulting in the loss of remineralization ability. Therefore, ACP needs to be stabilized in an amorphous state before application. Herein, ACP stabilizers, including amelogenin and its analogs, casein phosphopeptides, polymers like chitosan derivatives, carboxymethylated PAMAM and polyelectrolytes, together with their mechanisms for stabilizing ACP are briefly reviewed. Scientific evidence supporting the remineralization ability of these ACP agents are introduced. Limitations of existing research and further prospects of ACP agents for clinical translation are also discussed.