Self-Assembling Peptide Amphiphile Nanofibers as a Scaffold for Dental Stem Cells

Recent advancements in hydrogels as novel tissue engineering scaffolds for dental pulp regeneration

Although conventional root canal treatment offers an effective therapeutic solution, it negatively affects the viability of the affected tooth. In recent years, pulp regeneration technology has emerged as a novel method for treating irreversible pulpitis due to its ability to maintain tooth vitality. The successful implementation of this technique depends on scaffolds and transplantation of exogenous stem cells or recruitment of endogenous stem cells. Accordingly, the three-dimensional structure and viscoelastic characteristics of hydrogel scaffolds, which parallel those of the extracellular matrix, have generated considerable interest. Furthermore, hydrogels support the controlled release of regenerative drugs and to load a wide variety of bioactive molecules. By integrating antibacterial agents into the hydrogel matrix and stimulating an immune response, root canal disinfection can be significantly improved and the rate of pulp regeneration can be accelerated. This review aims to provide an overview of the clinical applications of hydrogels that have been reported in the last 5 years, and offer a comprehensive summary of the different approaches that have been utilized for the optimization of hydrogel scaffolds for pulp regeneration. Advancements and challenges in pulp regeneration using hydrogels treating aged teeth are discussed.

Macro, Micro, and Nano-Inspired Bioactive Polymeric Biomaterials in Therapeutic, and Regenerative Orofacial Applications

Introducing dental polymers has accelerated biotechnological research, advancing tissue engineering, biomaterials development, and drug delivery. Polymers have been utilized effectively in dentistry to build dentures and orthodontic equipment and are key components in the composition of numerous restorative materials. Furthermore, dental polymers have the potential to be employed for medication administration and tissue regeneration. To analyze the influence of polymer-based investigations on practical medical trials, it is required to evaluate the research undertaken in this sector. The present review aims to gather evidence on polymer applications in dental, oral, and maxillofacial reconstruction.

Elucidating the cell penetrating properties of self-assembling β-peptides

Self-assembling lipopeptide hydrogels have been widely developed for the delivery of therapeutics due to their rapid gelation, injectability, and highly controlled physicochemical properties. Lipopeptides are also known for their membrane-associating and cell penetrating properties, which may impact on their application in cell-encapsulation. Self-assembling lipidated-β3-peptide materials developed in our laboratory have previously been used in cell culture as 2D substrates, thus as a continuation of this work we aimed to encapsulate cells in 3D by forming a hydrogel. We therefore assessed the self-assembling lipidated-β3-peptides for cell-penetrating properties in mesenchymal stems cells (MSC) using fluorescence microscopy and membrane association with surface plasmon resonance spectroscopy (SPR). The results demonstrated that lipidated β3-peptides penetrate the MSC plasma membrane and localise to the mitochondrial network. While self-assembling lipopeptide hydrogels have shown tremendous potential for delivery of therapeutics, further optimisation may be required to minimise the membrane uptake of the lipidated-β3-peptides for cell encapsulation applications.

Hopes and opportunities of stem cells from human exfoliated deciduous teeth (SHED) in cartilage tissue regeneration

Cartilage lesions are common conditions, affecting elderly and non-athletic populations. Despite recent advances, cartilage regeneration remains a major challenge today. The absence of an inflammatory response following damage and the inability of stem cells to penetrate into the healing site due to the absence of blood and lymph vessels are assumed to hinder joint repair. Stem cell-based regeneration and tissue engineering have opened new horizons for treatment. With advances in biological sciences, especially stem cell research, the function of various growth factors in the regulation of cell proliferation and differentiation has been established. Mesenchymal stem cells (MSCs) isolated from different tissues have been shown to increase into therapeutically relevant cell numbers and differentiate into mature chondrocytes. As MSCs can differentiate and become engrafted inside the host, they are considered suitable candidates for cartilage regeneration. Stem cells from human exfoliated deciduous teeth (SHED) provide a novel and non-invasive source of MSCs. Due to their simple isolation, chondrogenic differentiation potential, and minimal immunogenicity, they can be an interesting option for cartilage regeneration. Recent studies have reported that SHED-derived secretome contains biomolecules and compounds that efficiently promote regeneration in damaged tissues, including cartilage. Overall, this review highlighted the advances and challenges of cartilage regeneration using stem cell-based therapies by focusing on SHED.

Nanofibrous scaffolds for regenerative endodontics treatment

Untreated dental caries, tooth trauma and dental anatomical variations such as dens invaginatus can result in pulpitis. However, standard root canal therapy cannot treat immature permanent teeth due to an open apical foramen and thin dentinal walls. Thus, regenerative endodontics treatment (RET) following a disinfection step with pulp regeneration has been developed. Pulp connective-tissue, dentin formation, revascularization and reinnervation can occur in this procedure which should be supplemented with intelligent biomaterials to improve repeatability and support well-coordinated regeneration. Furthermore, nanofibrous scaffolds, as one of the most commonly used materials, show promise. The purpose of this article is to highlight the advantages of nanofibrous scaffolds and discuss the future modification and application of them.

Role of Nanoparticles in Environmental Remediation: An Insight into Heavy Metal Pollution from Dentistry

Environmental damage is without a doubt one of the most serious issues confronting society today. As dental professionals, we must recognize that some of the procedures and techniques we have been using may pose environmental risks. The usage and discharge of heavy metals from dental set-ups pollute the environment and pose a serious threat to the ecosystem. Due to the exclusive properties of nanosized particles, nanotechnology is a booming field that is being extensively studied for the remediation of pollutants. Given that the nanoparticles have a high surface area to volume ratio and significantly greater reactivity, they have been greatly considered for environmental remediation. This review aims at identifying the heavy metal sources and their environmental impact in dentistry and provides insights into the usage of nanoparticles in environmental remediation. Although the literature on various functions of inorganic nanoparticles in environmental remediation was reviewed, the research is still confined to laboratory set-ups and there is a need for more studies on the usage of nanoparticles in environmental remediation.

Recent advances in design and applications of biomimetic self-assembled peptide hydrogels for hard tissue regeneration

Abstract

The development of natural biomaterials applied for hard tissue repair and regeneration is of great importance, especially in societies with a large elderly population. Self-assembled peptide hydrogels are a new generation of biomaterials that provide excellent biocompatibility, tunable mechanical stability, injectability, trigger capability, lack of immunogenic reactions, and the ability to load cells and active pharmaceutical agents for tissue regeneration. Peptide-based hydrogels are ideal templates for the deposition of hydroxyapatite crystals, which can mimic the extracellular matrix. Thus, peptide-based hydrogels enhance hard tissue repair and regeneration compared to conventional methods. This review presents three major self-assembled peptide hydrogels with potential application for bone and dental tissue regeneration, including ionic self-complementary peptides, amphiphilic (surfactant-like) peptides, and triple-helix (collagen-like) peptides. Special attention is given to the main bioactive peptides, the role and importance of self-assembled peptide hydrogels, and a brief overview on molecular simulation of self-assembled peptide hydrogels applied for bone and dental tissue engineering and regeneration.

Graphic abstract

Which experimental models and explorations to use in regenerative endodontics? A comprehensive review on standard practices

Since the discovery of dental pulp stem cells, a lot of teams have expressed an interest in dental pulp regeneration. Many approaches, experimental models and biological explorations have been developed, each including the use of stem cells and scaffolds with the final goal being clinical application in humans. In this review, the authors' objective was to compare the experimental models and strategies used for the development of biomaterials for tissue engineering of dental pulp with stem cells. Electronic queries were conducted on PubMed using the following terms: pulp regeneration, scaffold, stem cells, tissue engineering and biomaterial. The extracted data included the following information: the strategy envisaged, the type of stem cells, the experimental models, the exploration or analysis methods, the cytotoxicity or viability or proliferation cellular tests, the tests of scaffold antibacterial properties and take into account the vascularization of the regenerated dental pulp. From the 71 selected articles, 59% focused on the "cell-transplantation" strategy, 82% used in vitro experimentation, 58% in vivo animal models and only one described an in vivo in situ human clinical study. 87% used dental pulp stem cells. A majority of the studies reported histology (75%) and immunohistochemistry explorations (66%). 73% mentioned the use of cytotoxicity, proliferation or viability tests. 48% took vascularization into account but only 6% studied the antibacterial properties of the scaffolds. This article gives an overview of the methods used to regenerate dental pulp from stem cells and should help researchers create the best development strategies for research in this field.

Applications of Biomaterials in 3D Cell Culture and Contributions of 3D Cell Culture to Drug Development and Basic Biomedical Research

The process of evaluating the efficacy and toxicity of drugs is important in the production of new drugs to treat diseases. Testing in humans is the most accurate method, but there are technical and ethical limitations. To overcome these limitations, various models have been developed in which responses to various external stimuli can be observed to help guide future trials. In particular, three-dimensional (3D) cell culture has a great advantage in simulating the physical and biological functions of tissues in the human body. This article reviews the biomaterials currently used to improve cellular functions in 3D culture and the contributions of 3D culture to cancer research, stem cell culture and drug and toxicity screening.

Hydrogels and Dentin-Pulp Complex Regeneration: From the Benchtop to Clinical Translation

Dentin-pulp complex is a term which refers to the dental pulp (DP) surrounded by dentin along its peripheries. Dentin and dental pulp are highly specialized tissues, which can be affected by various insults, primarily by dental caries. Regeneration of the dentin-pulp complex is of paramount importance to regain tooth vitality. The regenerative endodontic procedure (REP) is a relatively current approach, which aims to regenerate the dentin-pulp complex through stimulating the differentiation of resident or transplanted stem/progenitor cells. Hydrogel-based scaffolds are a unique category of three dimensional polymeric networks with high water content. They are hydrophilic, biocompatible, with tunable degradation patterns and mechanical properties, in addition to the ability to be loaded with various bioactive molecules. Furthermore, hydrogels have a considerable degree of flexibility and elasticity, mimicking the cell extracellular matrix (ECM), particularly that of the DP. The current review presents how for dentin-pulp complex regeneration, the application of injectable hydrogels combined with stem/progenitor cells could represent a promising approach. According to the source of the polymeric chain forming the hydrogel, they can be classified into natural, synthetic or hybrid hydrogels, combining natural and synthetic ones. Natural polymers are bioactive, highly biocompatible, and biodegradable by naturally occurring enzymes or via hydrolysis. On the other hand, synthetic polymers offer tunable mechanical properties, thermostability and durability as compared to natural hydrogels. Hybrid hydrogels combine the benefits of synthetic and natural polymers. Hydrogels can be biofunctionalized with cell-binding sequences as arginine-glycine-aspartic acid (RGD), can be used for local delivery of bioactive molecules and cellularized with stem cells for dentin-pulp regeneration. Formulating a hydrogel scaffold material fulfilling the required criteria in regenerative endodontics is still an area of active research, which shows promising potential for replacing conventional endodontic treatments in the near future.

STRO-1 positive cell expansion during osteogenic differentiation: A comparative study of three mesenchymal stem cell types of dental origin

OBJECTIVE

Although the osteogenic differentiation potential of mesenchymal stem cells of dental origin is well established, the roles of different marker proteins in this process remain to be clarified. Our aim was to compare the cellular and molecular changes, focusing in particular on mesenchymal stem cell markers, during in vitro osteogenesis in three dental stem cell types: dental follicle stem cells (DFSCs), periodontal ligament stem cells (PDLSCs) and dental pulp stem cells (DPSCs).

DESIGN

Human DFSCs, PDLSCs and DPSCs were isolated, cultured and their osteogenic differentiation was induced for 3 weeks. Mineralization was assessed by von Kossa staining and calcium concentration measurements. The expression of mesenchymal and osteogenic markers was studied by immunocytochemistry and qPCR techniques. Alkaline phosphatase (ALP) activity and the frequency of STRO-1 positive cells were also quantified.

RESULTS

The three cultures all showed abundant mineralization, with high calcium content by day 21. The expression of vimentin and nestin was sustained after osteogenic induction. The osteogenic medium induced a considerable elevation of STRO-1 positive cells. By day 7, the ALP mRNA level had increased more than 100-fold in DFSCs, PDLSCs, and DPSCs. Quantitative PCR results indicated dissimilarities of osteoblastic marker levels in the three dental stem cell cultures.

CONCLUSIONS

DFSCs, PDLSCs and DPSCs have similar functional osteogenic differentiation capacities although their expressional profiles of key osteogenic markers show considerable variations. The STRO-1 positive cell fraction expands during osteogenic differentiation while vimentin and nestin expression remain high. For identification of stemness, functional studies rather than marker expressions are needed.

Dental pulp stem cells response on the nanotopography of scaffold to regenerate dentin-pulp complex tissue

The study of regenerative dentistry receives a fast growing interest. The potential ability of the dentin-pulp complex to regenerate is both promising and perplexing. To answer the challenging nature of the dental environment, scientists have developed various combinations of biomaterial scaffolds, stem cells, and incorporation of several growth factors. One of the crucial elements of this tissue engineering plan is the selection and fabrication of scaffolds. However, further findings suggest that cell behavior hugely depends on mechanical signaling. Nanotopography modifies scaffolds to alter cell migration and differentiation. However, to the best of the author's knowledge, there are very few studies addressing the correlation between nanotopography and dentin-pulp complex regeneration. Therefore, this article presents a comprehensive review of these studies and suggests a direction for future developments, particularly in the incorporation of nanotopography design for dentin-pulp complex regeneration.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.

Natural Antimicrobials in the Dental Pulp

INTRODUCTION

Like many tissues, the dental pulp is equipped with innate and adaptive immune responses, designed to defend against infection and limit its spread. The pulp's innate immune response includes the synthesis and release of antimicrobial peptides by several dental pulp cell types. These naturally-occurring antimicrobial peptides have broad spectrum activity against bacteria, fungi and viruses. There is a resurgence of interest in the bioactivities of naturally-occurring antimicrobial peptides, largely driven by the need to develop alternatives to antibiotics.

METHODS

This narrative review focused on the general properties of antimicrobial peptides, providing an overview of their sources and actions within the dental pulp.

RESULTS

We summarized the relevance of antimicrobial peptides in defending the dental pulp, highlighting the potential for many of these antimicrobials to be modified or mimicked for prospective therapeutic use.

CONCLUSION

Antimicrobial peptides and novel peptide-based therapeutics are particularly attractive as emerging treatments for polymicrobial infections, such as endodontic infections, because of their broad activity against a range of pathogens.

Biomimetic Aspects of Restorative Dentistry Biomaterials

Biomimetic has emerged as a multi-disciplinary science in several biomedical subjects in recent decades, including biomaterials and dentistry. In restorative dentistry, biomimetic approaches have been applied for a range of applications, such as restoring tooth defects using bioinspired peptides to achieve remineralization, bioactive and biomimetic biomaterials, and tissue engineering for regeneration. Advancements in the modern adhesive restorative materials, understanding of biomaterial-tissue interaction at the nano and microscale further enhanced the restorative materials' properties (such as color, morphology, and strength) to mimic natural teeth. In addition, the tissue-engineering approaches resulted in regeneration of lost or damaged dental tissues mimicking their natural counterpart. The aim of the present article is to review various biomimetic approaches used to replace lost or damaged dental tissues using restorative biomaterials and tissue-engineering techniques. In addition, tooth structure, and various biomimetic properties of dental restorative materials and tissue-engineering scaffold materials, are discussed.

Then and Now-A Look Inside the Lives of 11 Women Presidents of the IADR

Extraordinary women scientists-past, current, and elected presidents of the International Association for Dental Research (IADR)-showcase pathways for success and leadership. In this series of autobiographical essays, these women of various cultural backgrounds with diverse areas of research describe their journeys in the passionate pursuit of excellence, despite the frequent obstacles and challenges. Through interviews and in their own words, we recap highlights of their dental research journeys and inspirations, their career trajectories toward the IADR presidency, and the benefits and challenges that they faced in their careers and personal lives. The purpose of this special issue is to honor these women, their life journeys, and how they have contributed to oral health research.

Pulp-Dentin Tissue Healing Response: A Discussion of Current Biomedical Approaches

Dental pulp tissue exposed to mechanical trauma or cariogenic process results in root canal and/or periapical infections, and conventionally treated with root canal procedures. The more recent regenerative endodontic procedure intends to achieve effective root canal disinfection and adequate pulp–dentin tissue regeneration; however, numerous limitations are reported. Because tooth is composed of vital soft pulp enclosed by the mineralized hard tissue in a highly organized structure, complete pulp–dentin tissue regeneration has been challenging to achieve. In consideration of the limitations and unique dental anatomy, it is important to understand the healing and repair processes through inflammatory-proliferative-remodeling phase transformations of pulp–dentin tissue. Upon cause by infectious and mechanical stimuli, the innate defense mechanism is initiated by resident pulp cells including immune cells through chemical signaling. After the expansion of infection and damage to resident pulp–dentin cells, consequent chemical signaling induces pluripotent mesenchymal stem cells (MSCs) to migrate to the injury site to perform the tissue regeneration process. Additionally, innovative biomaterials are necessary to facilitate the immune response and pulp–dentin tissue regeneration roles of MSCs. This review highlights current approaches of pulp–dentin tissue healing process and suggests potential biomedical perspective of the pulp–dentin tissue regeneration.

Polymeric scaffolds for dental pulp tissue engineering: A review

OBJECTIVES

The purpose of this review is to describe recent developments in pulp tissue engineering using scaffolds and/or stem cells. It is crucial to understand how this approach can revitalize damaged dentin-pulp tissue. Widespread scaffold materials, both natural and synthetic, and their fabrication methods, and stem-progenitor cells with the potential of pulp regeneration will be discussed.

DATA AND SOURCES

A review of literature was conducted through online databases, including MEDLINE by using the PubMed search engine, Scopus, and the Cochrane Library.

STUDY SELECTION

Studies were selected based on relevance, with a preference given to recent research, particularly from the past decade.

CONCLUSIONS

The use of biomaterial scaffolds and stem cells can be safe and potent for the regeneration of pulp tissue and re-establishment of tooth vitality. Natural and synthetic polymers have distinct advantages and limitations and in vitro and in vivo testing have produced positive results for cell attachment, proliferation, and angiogenesis. The type of biomaterial used for scaffold fabrication also facilitates stem cell differentiation into odontoblasts and the resulting biochemistry of tissue repair for each polymer and cell type was discussed. Multiple methods of scaffold design exist for pulp tissue engineering, which demonstrates the variability in tissue engineering applications in endodontics. This review explains the potential of evidence-based tissue engineering strategies and outcomes in pulp regeneration.

Comparative characterization of mesenchymal stem cells from human dental pulp and adipose tissue for bone regeneration potential

Bone tissue engineering is an area of regenerative medicine that attempts to repair bone defects. Seed cells such as dental pulp stem cells (DPSCs) and adipose tissue-derived stem cells (ADSCs) are two of the most well-characterized cells for bone regeneration because their use involves few ethical constraints and they have the ability to differentiate into multiple cell types, secreting growth factors and depositing mineral. However, bone regeneration ability of these cells remains unclear. This study aimed to compare the bone formation capacity of DPSCs and ADSCs in vitro and in vivo. Studies revealed that DPSCs had enhanced colony-forming ability, higher proliferative ability, stronger migration ability and higher expression of angiogenesis-related genes. They also secreted more vascular endothelial growth factor compared to ADSCs. In contrast, ADSCs grew more slowly compared to DPSCs but exhibited greater osteogenic differentiation potential, higher expression of osteoblast marker genes, and greater mineral deposition. Furthermore, after DPSCs and ADSCs were implanted into a mandibular defect of a rat for 6 weeks, ADSCs showed visible bone tissue as early as week 1 and promoted faster and greater bone regeneration compared to the DPSC group. These results suggest that ADSCs might be more useful than DPSCs for bone regeneration.

Polymer-Based Instructive Scaffolds for Endodontic Regeneration

The challenge of endodontic regeneration is modulated by clinical conditions which determine five kinds of tissue requirements: pulp connective-tissue formation, dentin formation, revascularization, reinnervation and radicular edification. Polymer scaffolds constitute keystone of the different endodontic regenerative strategies. Indeed, scaffolds are crucial for carrying active molecules and competent cells which optimize the regeneration. Hydrogels are very beneficial for controlling viscosity and porosity of endodontic scaffolds. The nanofibrous and microporous scaffolds mimicking extracellular matrix are also of great interest for promoting dentin-pulp formation. Two main types of polymer scaffolds are highlighted: collagen and fibrin. Collagen scaffolds which are similar to native pulp tissue, are adequate for pulp connective tissue formation. Functionnalization by active biomolecules as BMP, SDF-1, G-CSF enhances their properties. Fibrin or PRF scaffolds present the advantage of promoting stem cell differentiation and concomitant revascularisation. The choice of the type of polymers (polypeptide, PCL, chitosan) can depend on its ability to deliver the active biomolecule or to build as suitable hydrogel as possible. Since 2010s, proposals to associate different types of polymers in a same scaffold have emerged for adding advantages or for offsetting a disadvantage of a polymer. Further works would study the synergetic effects of different innovative polymers composition.

A Versatile Biocompatible Antibiotic Delivery System Based on Self-Assembling Peptides with Antimicrobial and Regenerative Potential

Periodontitis is a chronic inflammatory and tissue-destructive disease. Since the polymicrobiome in the oral cavity makes it difficult to treat, novel therapeutic strategies are required. Hydrogels based on self-assembling peptides (SAP) can be suitable candidates for periodontal therapy due to their injectability, biocompatibility, cargo-loading capacity, and tunable physicochemical and mechanical properties. In this study, two SAP hydrogels (P11-4 and P11-28/29) are examined for their intrinsic antimicrobial activity, regenerative potential, and antibiotic delivery capacity. A significant antibacterial effect of P11-28/29 hydrogels on the periodontal pathogen Porphyromonas gingivalis and a less pronounced effect for P11-4 hydrogels is demonstrated. The metabolic activity rates of human dental follicle stem cells (DFSCs), which reflect cell viability and may thus indicate the regenerative capacity, are similar on tissue culture polystyrene (TCPS) and on P11-4 hydrogels after 14 days of culture. Noticeably, both SAP hydrogels strengthen the osteogenic differentiation of DFSCs compared with TCPS. The incorporation of tetracycline, ciprofloxacin, and doxycycline does not affect fibril formation of either SAP hydrogel and results in favorable release kinetics up to 120 h. In summary, this study reveals that P11-SAP hydrogels combine many favorable properties required to make them applicable as prospective novel treatment strategy for periodontal therapy.

Self-Healing Supramolecular Hydrogels for Tissue Engineering Applications

Self-healing supramolecular hydrogels have emerged as a novel class of biomaterials that combine hydrogels with supramolecular chemistry to develop highly functional biomaterials with advantages including native tissue mimicry, biocompatibility, and injectability. These properties are endowed by the reversibly cross-linked polymer network of the hydrogel. These hydrogels have great potential for realizing yet to be clinically translated tissue engineering therapies. This review presents methods of self-healing supramolecular hydrogel formation and their uses in tissue engineering as well as future perspectives.

Cancer nanomedicine: focus on recent developments and self-assembled peptide nanocarriers

The applications of nanoparticulate drug delivery have received abundant interest in the field of cancer diagnosis and treatment.

Present and future of tissue engineering scaffolds for dentin-pulp complex regeneration

More than two thirds of the global population suffers from tooth decay, which results in cavities with various levels of lesion severity. Clinical interventions to treat tooth decay range from simple coronal fillings to invasive root canal treatment. Pulp capping is the only available clinical option to maintain the pulp vitality in deep lesions, but irreversible pulp inflammation and reinfection are frequent outcomes for this treatment. When affected pulp involvement is beyond repair, the dentist has to perform endodontic therapy leaving the tooth non-vital and brittle. On-going research strategies have failed to overcome the limitations of existing pulp capping materials so that healthy and progressive regeneration of the injured tissues is attained. Preserving pulp vitality is crucial for tooth homeostasis and durability, and thus, there is a critical need for clinical interventions that enable regeneration of the dentin-pulp complex to rescue millions of teeth annually. The identification and development of appropriate biomaterials for dentin-pulp scaffolds are necessary to optimize clinical approaches to regenerate these hybrid dental tissues. Likewise, a deep understanding of the interactions between the micro-environment, growth factors, and progenitor cells will provide design basis for the most fitting scaffolds for this purpose. In this review, we first introduce the long-lasting clinical dental problem of rescuing diseased tooth vitality, the limitations of current clinical therapies and interventions to restore the damaged tissues, and the need for new strategies to fully revitalize the tooth. Then, we comprehensively report on the characteristics of the main materials of naturally-derived and synthetically-engineered polymers, ceramics, and composite scaffolds as well as their use in dentin-pulp complex regeneration strategies. Finally, we present a series of innovative smart polymeric biomaterials with potential to overcome dentin-pulp complex regeneration challenges.

Effects of the nitric oxide releasing biomimetic nanomatrix gel on pulp-dentin regeneration: Pilot study

Successful disinfection alongside complete endodontic tissue regeneration and revascularization are the most desired clinical outcomes of regenerative endodontics. Despite reported clinical successes, significant limitations to the current regenerative endodontic procedure (REP) have been elucidated. To improve the current REP, an antibiotics and nitric oxide (NO) releasing biomimetic nanomatrix gel was developed. The study evaluates antibacterial effects of an antibiotics and NO releasing biomimetic nanomatrix gel on multispecies endodontic bacteria. Antibiotics, ciprofloxacin (CF) and metronidazole (MN) were mixed and encapsulated within the NO releasing biomimetic nanomatrix gel. The gel was synthesized and self-assembled from peptide amphiphiles containing various functional groups. Antibacterial effects of the antibiotics and NO releasing biomimetic nanomatrix gel were evaluated using bacterial viability assays involving endodontic microorganisms including clinical samples. Pulp-dentin regeneration was evaluated via animal-model experiments. The antibiotics and NO releasing biomimetic nanomatrix gel demonstrated a concentration dependent antibacterial effect. In addition, NO alone demonstrated a concentration dependent antibacterial effect on endodontic microorganism. An in vivo analysis demonstrated the antibiotics and NO releasing biomimetic nanomatrix gel promoted tooth revascularization with maturation of root canals. An optimal concentration of and NO releasing nanomatrix gel is suggested for its potential as a root treatment material for REP and an appropriate protocol for human trials. Further investigation is required to obtain a larger sample size and decide upon ideal growth factor incorporation.

A novel hydrogel scaffold for periodontal ligament stem cells

Periodontal ligament stem cells (PDLSCs) possess extensive regeneration potential. However, their therapeutic application demands a scaffold with appropriate properties. HydroMatrix (HydM) is a novel injectable peptide nanofiber hydrogel developed recently for cell culture. Our aim was to test whether HydM would be a suitable scaffold for proliferation and osteogenic differentiation of PDLSCs. PDLSCs were seeded on non-coated or HydM-coated surfaces. Both real-time impedance analysis and cell viability assay documented cell growth on HydM. PDLSCs showed healthy, fibroblast-like morphology on the hydrogel. After a 3-week-long culture in osteogenic medium, mineralization was much more intense in HydM cultures compared to control. Alkaline phosphatase activity of the cells grown on the gels reached the non-coated control levels. Our data provided evidence that PDLSCs can adhere, survive, migrate, and proliferate on HydM and this gel also supports their osteogenic differentiation. We first applied impedimetry for dental stem cells cultured on a scaffold. HydM is ideal for in vitro studies of PDLSCs. It may also serve not only as a reference material but also in the future as a promising biocompatible scaffold for preclinical studies.

Pulp Regeneration Concepts for Nonvital Teeth: From Tissue Engineering to Clinical Approaches

Following the basis of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontic has emerged as a new concept of dental treatment. Clinical procedures have been proposed by endodontic practitioners willing to promote regenerative therapy. Preserving pulp vitality was a first approach. Later procedures aimed to regenerate a vascularized pulp in necrotic root canals. However, there is still no protocol allowing an effective regeneration of necrotic pulp tissue either in immature or mature teeth. This review explores in vitro and preclinical concepts developed during the last decade, especially the potential use of stem cells, bioactive molecules, and scaffolds, and makes a comparison with the goals achieved so far in clinical practice. Regeneration of pulp-like tissue has been shown in various experimental conditions. However, the appropriate techniques are currently in a developmental stage. The ideal combination of scaffolds and growth factors to obtain a complete regeneration of the pulp-dentin complex is still unknown. The use of stem cells, especially from pulp origin, sounds promising for pulp regeneration therapy, but it has not been applied so far for clinical endodontics, in case of necrotic teeth. The gap observed between the hope raised from in vitro experiments and the reality of endodontic treatments suggests that clinical success may be achieved without external stem cell application. Therefore, procedures using the concept of cell homing, through evoked bleeding that permit to recreate a living tissue that mimics the original pulp has been proposed. Perspectives for pulp tissue engineering in the near future include a better control of clinical parameters and pragmatic approach of the experimental results (autologous stem cells from cell homing, controlled release of growth factors). In the coming years, this therapeutic strategy will probably become a clinical reality, even for mature necrotic teeth.

Glucosamine-Based Supramolecular Nanotubes for Human Mesenchymal Cell Therapy

Herein, we demonstrate an example of glucosamine-based supramolecular hydrogels that can be used for human mesenchymal cell therapy. We designed and synthesized a series of amino acid derivatives based on a strategy of capping d-glucosamine moiety at the C-terminus and fluorinated benzyl group at the N-terminus. From a systematic study on chemical structures, we discovered that the glucosamine-based supramolecular hydrogel [pentafluorobenzyl (PFB)-F-Glu] self-assembled with one-dimensional nanotubular structures at physiological pH. The self-assembly of a newly discovered PFB-F-Glu motif is attributed to the synergistic effect of π-π stacking and extensive intermolecular hydrogen bonding network in aqueous medium. Notably, PFB-F-Glu nanotubes are proven to be nontoxic to human mesenchymal stem cells (hMSCs) and have been shown to enhance hMSC proliferation while maintaining their pluripotency. Retaining of pluripotency capabilities provides potentially unlimited source of undifferentiated cells for the treatment of future cell therapies. Furthermore, hMSCs cultured on PFB-F-Glu are able to secrete paracrine factors that downregulate profibrotic gene expression in lipopolysaccharide-treated human skin fibroblasts, which demonstrates that PFB-F-Glu nanotubes have the potential to be used for wound healing applications. Overall, this article addresses the importance of chemical design to generate supramolecular biomaterials for stem cell therapy.

Injectable network biomaterials via molecular or colloidal self-assembly

Self-assembly is a powerful tool to create functional materials. A specific application for which self-assembled materials are ideally suited is in creating injectable biomaterials. Contrasting with traditional biomaterials that are implanted through surgical means, injecting biomaterials through the skin offers numerous advantages, expanding the scope and impact for biomaterials in medicine. In particular, self-assembled biomaterials prepared from molecular or colloidal interactions have been frequently explored. The strategies to create these materials are varied, taking advantage of engineered oligopeptides, proteins, and nanoparticles as well as affinity-mediated crosslinking of synthetic precursors. Self-assembled materials typically facilitate injectability through two different mechanisms: i) in situ self-assembly, whereby materials would be administered in a monomeric or oligomeric form and self-assemble in response to some physiologic stimulus, or ii) self-assembled materials that, by virtue of their dynamic, non-covalent interactions, shear-thin to facilitate flow within a syringe and subsequently self-heal into its reassembled material form at the injection site. Indeed, many classes of materials are capable of being injected using a combination of these two mechanisms. Particular utility has been noted for self-assembled biomaterials in the context of tissue engineering, regenerative medicine, drug delivery, and immunoengineering. Given the controlled and multifunctional nature of many self-assembled materials demonstrated to date, we project a future where injectable self-assembled biomaterials afford improved practice in advancing healthcare.

Nanotechnology in dentistry: Unleashing the hidden gems

Nanotechnology in dentistry refers to new generation research carried out to develop newer technologies, restorative materials and drugs of Nano dimensions. The word “Nano” refers to Nanoscale particles. Although the science of nanotechnology in dentistry is recent and less developed, but still has vast potential to show advancement and improvement in the field of dentistry. As nanotechnology is making firm grip in other fields such as drug delivery system and reducing toxicity by the emergence of more biocompatible materials. Clinicians, researchers, and manufacturers are taking keen interest and participation in the advancement of this field. This paper is an attempt in unleashing the hidden gems of nanotechnology-focusing latest developments in field restorative and surgical dentistry to enhance the quality and biocompatibility of newer generation dental materials and technology. This paper will also focus on potential hurdles encountered in the development of newer materials by utilizing the science of nanotechnology and their potential safety issues concern.

Advances and perspectives in tooth tissue engineering

Bio-engineered teeth that can grow and remodel in a manner similar to that of natural teeth have the potential to serve as permanent replacements to the currently used prosthetic teeth, such as dental implants. A major challenge in designing functional bio-engineered teeth is to mimic both the structural and anisotropic mechanical characteristics of the native tooth. Therefore, the field of dental and whole tooth regeneration has advanced towards the molecular and nanoscale design of bio-active, biomimetic systems, using biomaterials, drug delivery systems and stem cells. The focus of this review is to discuss recent advances in tooth tissue engineering, using biomimetic scaffolds that provide proper architectural cues, exhibit the capacity to support dental stem cell proliferation and differentiation and sequester and release bio-active agents, such as growth factors and nucleic acids, in a spatiotemporal controlled manner. Although many in vitro and in vivo studies on tooth regeneration appear promising, before tooth tissue engineering becomes a reality for humans, additional research is needed to perfect methods that use adult human dental stem cells, as opposed to embryonic dental stem cells, and to devise the means to generate bio-engineered teeth of predetermined size and shape. Copyright © 2016 John Wiley & Sons, Ltd.

Dental and orofacial mesenchymal stem cells in craniofacial regeneration: The prosthodontist's point of view

Of the available regenerative treatment options, craniofacial tissue regeneration using mesenchymal stem cells (MSCs) shows promise. The ability of stem cells to produce multiple specialized cell types along with their extensive distribution in many adult tissues have made them an attractive target for applications in tissue engineering. MSCs reside in a wide spectrum of postnatal tissue types and have been successfully isolated from orofacial tissues. These dental- or orofacial-derived MSCs possess self-renewal and multilineage differentiation capacities. The craniofacial system is composed of complex hard and soft tissues derived from sophisticated processes starting with embryonic development. Because of the complexity of the craniofacial tissues, the application of stem cells presents challenges in terms of the size, shape, and form of the engineered structures, the specialized final developed cells, and the modulation of timely blood supply while limiting inflammatory and immunological responses. The cell delivery vehicle has an important role in the in vivo performance of stem cells and could dictate the success of the regenerative therapy. Among the available hydrogel biomaterials for cell encapsulation, alginate-based hydrogels have shown promising results in biomedical applications. Alginate scaffolds encapsulating MSCs can provide a suitable microenvironment for cell viability and differentiation for tissue regeneration applications. This review aims to summarize current applications of dental-derived stem cell therapy and highlight the use of alginate-based hydrogels for applications in craniofacial tissue engineering.

Biocompatibility of biological material polylactic acid with stem cells from human exfoliated deciduous teeth

To investigate the biocompatibility of the biomaterial, polylactic acid (PLA) with stem cells from human exfoliated deciduous teeth (SHED) and its induction of mineralization as a type of scaffold material. To determine the impacts of biomaterial PLA on proliferation and mineralization of SHED, the expression of surface molecules of SHED isolated and cultured in vitro was detected by flow cytometry. In addition, cell proliferation was measured using MTT and Edu assays, and the evaluation of mineralized differentiation was performed using Alizarin Red S staining. In addition, the expression levels of osteogenic marker genes were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. SHED were successfully isolated and identified. The MTT and Edu results indicated that the proliferation of SHED cultured in PLA and normal medium was not significantly different. The Alizarin Red S staining demonstrated that the mineralization capability was significantly higher in the SHED that were cultured in PLA medium. Furthermore, RT-qPCR and western blot analyses indicated that the expression levels of osteogenic marker genes were higher in the SHED cultured in PLA medium. These results suggested that PLA possesses good biocompatibility with SHED and may effectively induce the mineralization of SHED and serve as a scaffold material.

Injectable scaffolds: Preparation and application in dental and craniofacial regeneration

Injectable scaffolds are appealing for tissue regeneration because they offer many advantages over pre-formed scaffolds. This article provides a comprehensive review of the injectable scaffolds currently being investigated for dental and craniofacial tissue regeneration. First, we provide an overview of injectable scaffolding materials, including natural, synthetic, and composite biomaterials. Next, we discuss a variety of characteristic parameters and gelation mechanisms of the injectable scaffolds. The advanced injectable scaffolding systems developed in recent years are then illustrated. Furthermore, we summarize the applications of the injectable scaffolds for the regeneration of dental and craniofacial tissues that include pulp, dentin, periodontal ligament, temporomandibular joint, and alveolar bone. Finally, our perspectives on the injectable scaffolds for dental and craniofacial tissue regeneration are offered as signposts for the future advancement of this field.

Presentation of functional groups on self-assembled supramolecular peptide nanofibers mimicking glycosaminoglycans for directed mesenchymal stem cell differentiation

Organizational complexity and functional diversity of the extracellular matrix regulate cellular behaviors.

Human Dental Pulp Stem Cells Suppress Alloantigen-induced Immunity by Stimulating T Cells to Release Transforming Growth Factor Beta

INTRODUCTION

Human dental pulp stem cells (hDPSCs) are ideal candidates for regenerating damaged dental tissue. To examine the possibility that hDPSCs may be used to regenerate pulp, we tested their in vitro effects on acute allogeneic immune responses.

METHODS

A peripheral blood mononuclear cell (PBMC) proliferation assay and immunoglobulin (Ig) production assay were performed to evaluate the immunosuppressive properties of hDPSCs.

RESULTS

The mixed lymphocyte reaction was suppressed by incubation with hDPSCs. Transforming growth factor beta (TGF-β) was the major soluble factor responsible for inhibiting the allogeneic proliferation of PBMCs. The production of IgM and IgG by allogeneic activation of responder B lymphocytes was also completely abrogated by TGF-β released from hDPSCs via interferon gamma in response to activation of the responder T lymphocytes.

CONCLUSIONS

hDPSCs inhibit acute allogeneic immune responses by their release of TGF-β as a result of allogeneic stimulation of T lymphocytes. This study provides an insight into the potential clinical use of hDPSCs for allogeneic transplantation.

Osteogenesis of peripheral blood mesenchymal stem cells in self assembling peptide nanofiber for healing critical size calvarial bony defect

Peripheral blood mesenchymal stem cells (PBMSCs) may be easily harvested from patients, permitting autologous grafts for bone tissue engineering in the future. However, the PBMSC’s capabilities of survival, osteogenesis and production of new bone matrix in the defect area are still unclear. Herein, PBMSCs were seeded into a nanofiber scaffold of self-assembling peptide (SAP) and cultured in osteogenic medium. The results indicated SAP can serve as a promising scaffold for PBMSCs survival and osteogenic differentiation in 3D conditions. Furthermore, the SAP seeded with the induced PBMSCs was splinted by two membranes of poly(lactic)-glycolic acid (PLGA) to fabricate a composited scaffold which was then used to repair a critical-size calvarial bone defect model in rat. Twelve weeks later the defect healing and mineralization were assessed by H&E staining and microcomputerized tomography (micro-CT). The osteogenesis and new bone formation of grafted cells in the scaffold were evaluated by immunohistochemistry. To our knowledge this is the first report with solid evidence demonstrating PBMSCs can survive in the bone defect area and directly contribute to new bone formation. Moreover, the present data also indicated the tissue engineering with PBMSCs/SAP/PLGA scaffold can serve as a novel prospective strategy for healing large size cranial defects.

Active Nanomaterials to Meet the Challenge of Dental Pulp Regeneration

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its regenerative potential. The regeneration of the pulp tissue is the dream of many generations of dental surgeons and will revolutionize clinical practices. Recently, the potential of the regenerative medicine field suggests that it would be possible to achieve such complex regeneration. Indeed, three crucial steps are needed: the control of infection and inflammation and the regeneration of lost pulp tissues. For regenerative medicine, in particular for dental pulp regeneration, the use of nano-structured biomaterials becomes decisive. Nano-designed materials allow the concentration of many different functions in a small volume, the increase in the quality of targeting, as well as the control of cost and delivery of active molecules. Nanomaterials based on extracellular mimetic nanostructure and functionalized with multi-active therapeutics appear essential to reverse infection and inflammation and concomitantly to orchestrate pulp cell colonization and differentiation. This novel generation of nanomaterials seems very promising to meet the challenge of the complex dental pulp regeneration.

Nanotechnology in dentistry: prevention, diagnosis, and therapy

Nanotechnology has rapidly expanded into all areas of science; it offers significant alternative ways to solve scientific and medical questions and problems. In dentistry, nanotechnology has been exploited in the development of restorative materials with some significant success. This review discusses nanointerfaces that could compromise the longevity of dental restorations, and how nanotechnolgy has been employed to modify them for providing long-term successful restorations. It also focuses on some challenging areas in dentistry, eg, oral biofilm and cancers, and how nanotechnology overcomes these challenges. The recent advances in nanodentistry and innovations in oral health-related diagnostic, preventive, and therapeutic methods required to maintain and obtain perfect oral health, have been discussed. The recent advances in nanotechnology could hold promise in bringing a paradigm shift in dental field. Although there are numerous complex therapies being developed to treat many diseases, their clinical use requires careful consideration of the expense of synthesis and implementation.

Peptide Amphiphiles in Corneal Tissue Engineering

The increasing interest in effort towards creating alternative therapies have led to exciting breakthroughs in the attempt to bio-fabricate and engineer live tissues. This has been particularly evident in the development of new approaches applied to reconstruct corneal tissue. The need for tissue-engineered corneas is largely a response to the shortage of donor tissue and the lack of suitable alternative biological scaffolds preventing the treatment of millions of blind people worldwide. This review is focused on recent developments in corneal tissue engineering, specifically on the use of self-assembling peptide amphiphiles for this purpose. Recently, peptide amphiphiles have generated great interest as therapeutic molecules, both in vitro and in vivo. Here we introduce this rapidly developing field, and examine innovative applications of peptide amphiphiles to create natural bio-prosthetic corneal tissue in vitro. The advantages of peptide amphiphiles over other biomaterials, namely their wide range of functions and applications, versatility, and transferability are also discussed to better understand how these fascinating molecules can help solve current challenges in corneal regeneration.

Stem cell-based pulp tissue engineering: variables enrolled in translation from the bench to the bedside, a systematic review of literature

Stem cell-based therapy (SC-BT) is emerging as an alternative for endodontic therapies. The interaction between stem cells and scaffolds plays a crucial role in the generation of a 'friendly cell' microenvironment. The aim of this systematic review was to explore techniques applied to regenerate the pulp-dentine complex tissue using SC-BT. An electronic search into the SciVerse Scopus (SS), ISI Web Science (IWS) and Entrez PubMed (EP) using specific keywords was performed. Specific inclusion and exclusion criteria were predetermined. The search yielded papers, out of which full-text papers were included in the final analyses. Data extraction pooled the results in four main topics: (a) influence of the chemical properties of the scaffolds over cell behaviour; (b) influence of the physical characteristics of scaffolds over cell behaviour; (c) strategies applied to improve the stem cell/scaffold interface; and (d) influence of cue microenvironment on stem cell differentiation towards odontoblast-like cells and pulp-like tissue formation. The relationship between the scaffolds, the environment and the growth factors released from dentine are critical for de novo pulp tissue regeneration. The preconditioning of dentine walls with ethylenediaminetetraacetic acid (EDTA) was imperative for successful pulp-dentine complex regeneration. An analyses of the grouped results revealed that pulp regeneration was an attainable goal.

Three-Dimensional Cell Entrapment as a Function of the Weight Percent of Peptide-Amphiphile Hydrogels

The design of scaffolds which mimic the stiffness, nanofiber structure, and biochemistry of the native extracellular matrix (ECM) has been a major objective for the tissue engineering field. Furthermore, mimicking the innate three-dimensional (3D) environment of the ECM has been shown to significantly altered cellular response compared to that of traditional two-dimensional (2D) culture. We report the development of a self-assembling, fibronectin-mimetic, peptide-amphiphile nanofiber scaffold for 3D cell culture. To form such a scaffold, 5 mol % of a bioactive PR_g fibronectin-mimetic peptide-amphiphile was mixed with 95 mol % of a diluent peptide-amphiphile (E2) whose purpose was to neutralize electrostatic interactions, increase the gelation kinetics, and promote cell survival. Atomic force microscopy verified the fibrilar structure of the gels, and the mechanical properties were characterized for various weight percent (wt %) formulations of the 5 mol % PR_g-95 mol % E2 peptide-amphiphile mixture. The 0.5 wt % formulations had an elastic modulus of 429.0 ± 21.3 Pa whereas the 1.0 wt % peptide-amphiphile hydrogels had an elastic modulus of 808.6 ± 38.1 Pa. The presence of entrapped cells in the gels decreased the elastic modulus, and the decrease was a function of cell loading. Although both formulations supported cell proliferation, the 0.5 wt % gels supported significantly greater NIH3T3/GFP fibroblast cell proliferation throughout the gels than the 1.0 wt % gels. However, compared to the 0.5 wt % formulations, the 1.0 wt % hydrogels promoted greater increases in mRNA expression and the production of fibronectin and type IV collagen ECM proteins. This study suggests that this fibronectin-mimetic scaffold holds great promise in the advancement of 3D culture applications and cell therapies.