Design strategies and applications of nacre-based biomaterials

In vivo study on osteogenic efficiency of nHA/ gel porous scaffold with nacre water-soluble matrix

BACKGROUND/PURPOSE

Nano-hydroxyapatite (nHA)/ gel porous scaffolds loaded with WSM carriers are promising bone replacement materials that can improve osseointegration ability. This investigation aimed to evaluate the osteoinductive activity by implanting the composition of nano-hydroxyapatite (nHA)/ Gel porous scaffolds as a carrier of WSM via an animal model.

MATERIALS AND METHODS

WSM was extracted and nHA was added to the matrix to construct porous composite scaffolds. The dose-effect curve of WSM concentration and alkaline phosphatase (ALP) activity was made by culturing rat osteoblasts and examining the absorbance. Three different materials were implanted into critical size defects (CSD) in the skulls of rats, which were further divided into four groups: WSM nHA /Gel group, n-WSM nHA /Gel group, HA powder group, and control group.

RESULTS

WSM (150 μg/mL-250μg/mL) effectively improved the activity of ALP in rat osteoblasts. All rats in each group had normal healing. WSM-loaded nHA /Gel group showed better performance on newly-formed bone tissue of rat skull and back at 4th week and 8th week, respectively. At the 4th week, the network of woven bone formed in the WSM-loaded nHA/Gel scaffold material. At 8th week, the reticular trabecular bone in the WSM-loaded scaffold material became dense lamellar bone, and the defect was mature lamellar bone. In the subcutaneous implantation experiment, WSM-loaded nHA/Gel scaffold material showed a better performance of heterotopic ossification than the pure nHA/Gel scaffold material.

CONCLUSION

WSM promotes osteoblast differentiation and bone mineralization. The results confirm that the nHA/ Gel Porous Scaffold with Nacre Water-Soluble Matrix has a significant bone promoting effect and can be used as a choice for tissue engineering to repair bone defects.

Exploring the potential of chitosan/aragonite biocomposite derived from cuttlebone waste: Elaboration, physicochemical properties and in vitro bioactivity

Cuttlefish bone biowaste is a potential source of a composite matrix based on chitin and aragonite. In the present work, we propose for the first time the elaboration of biocomposites based on chitosan and aragonite through the valorization of bone waste. The composition of the ventral and dorsal surfaces of bone is well studied by ICP-OES. An extraction process has been applied to the dorsal surface to extract β-chitin and chitosan with controlled physico-chemical characteristics. In parallel, aragonite isolation was carried out on the ventral side. The freeze-drying method was used to incorporate aragonite into the chitosan polymer to form CHS/ArgS biocomposites. Physicochemical characterizations were performed by FT-IR, SEM, XRD, 1H NMR, TGA/DSC, potentiometry and viscometry. The ICP-OES method was used to evaluate in vitro the bioactivity level of biocomposite in simulated human plasma (SBF), enabling analysis of the interactions between the material and SBF. The results obtained indicate that the CHS/ArgS biocomposite derived from cuttlefish bone exhibits bioactivity, and that chitosan enhances the bioactivity of aragonite. The CHS/ArgS biocomposite showed excellent ability to form an apatite layer on its surface. After three days' immersion, FTIR and SEM analyses confirmed the formation of this layer.

3D printing nacre powder/sodium alginate scaffold loaded with PRF promotes bone tissue repair and regeneration

Bone defects are a common complication of bone diseases, which often affect the quality of life and mental health of patients. The use of biomimetic bone scaffolds loaded with bioactive substances has become a focal point in the research on bone defect repair. In this study, composite scaffolds resembling bone tissue were created using nacre powder (NP) and sodium alginate (SA) through 3D printing. These scaffolds exhibit several physiological structural and mechanical characteristics of bone tissue, such as suitable porosity, an appropriate pore size, applicable degradation performance and satisfying the mechanical requirements of cancellous bone, etc. Then, platelet-rich fibrin (PRF), containing a mass of growth factors, was loaded on the NP/SA scaffolds. This was aimed to fully maximize the synergistic effect with NP, thereby accelerating bone tissue regeneration. Overall, this study marks the first instance of preparing a bionic bone structure scaffold containing NP by 3D printing technology, which is combined with PRF to further accelerate bone regeneration. These findings offer a new treatment strategy for bone tissue regeneration in clinical applications.

Nacre-Mimetic Structure Multifunctional Ion-Conductive Hydrogel Strain Sensors with Ultrastretchability, High Sensitivity, and Excellent Adhesive Properties

Recently, conductive hydrogels have emerged as promising materials for smart, wearable devices. However, limited mechanical properties and low sensitivity greatly restrict their lifespan. Based on the design of biomimetic-layered structure, the conductive hydrogels with nacre-mimetic structure were prepared by using layered acrylic bentonite (AABT) and phytic acid (PA) as multifunctional "brick" and "mortar" units. Among them, the unique rigid cyclic multihydroxyl structure of the "organic mortar" PA preserves both ultrastretchability (4050.02%) and high stress (563.20 kPa) of the hydrogel, which far exceeds most of the reported articles. Because of the synergistic effect of AABT and PA, the hydrogel exhibits an excellent adhesive strength (87.74 kPa). The role of AABT in the adhesive properties of hydrogels is proposed for the first time, and a general strategy for improving the adhesive properties of hydrogels by using AABT is demonstrated. Furthermore, AABT provides ion channels and PA ionizes abundant H+, conferring a high gauge factor (GF = 14.95) and excellent antimicrobial properties to the hydrogel. Also, inspired by fruit batteries, simple self-powered flexible sensors were developed. Consequently, this study provides knowledge for functional bentonite filler modified hydrogel, and the prepared multifunctional ionic conductive hydrogel shows great application potential in the field of intelligent wearable devices.

A Novel Kunitz-Type Serine Protease Inhibitor (HcKuSPI) is Involved in Antibacterial Defense in Innate Immunity and Participates in Shell Formation of Hyriopsis cumingii

Serine protease inhibitors (SPIs) are abundantly reported for its inhibition against specific proteases involved in the immune responses, but SPI data related to calcareous shells are scarce. Previously, our research group has reported the proteome analysis of non-nucleated pearl powder, and a candidate matrix protein containing two Kunitz domains in the acid soluble fraction caught our attention. In the present study, the full-length cDNA sequence of HcKuSPI was obtained from Hyriopsis cumingii. HcKuSPI was specifically expressed in the mantle, with hybridization signals mainly concentrated to dorsal epithelial cells at the mantle edge and weak signals at the mantle pallium, suggesting HcKuSPI was involved in shell formation. HcKuSPI expression in the mantle was upregulated after Aeromonas hydrophila and Staphylococcus aureus challenge to extrapallial fluids (EPFs). A glutathione S transferase (GST)-HcKuSPI recombinant protein showed strong inhibitory activity against the proteases, trypsin and chymotrypsin. Moreover, HcKuSPI expression in an experimental group was significantly higher when compared with a control group during pellicle growth and crystal deposition in shell regeneration processes, while the organic shell framework of newborn prisms and nacre tablets was completely destroyed after HcKuSPI RNA interference (RNAi). Therefore, HcKuSPI secreted by the mantle may effectively neutralize excess proteases and bacterial proteases in the EPF during bacterial infection and could prevent matrix protein extracellular degradation by suppressing protease proteolytic activity, thereby ensuring a smooth shell biomineralization. In addition, GST-HcKuSPI was also crucial for crystal morphology regulation. These results have important implications for our understanding of the potential roles of SPIs during shell biomineralization.

In Vitro Osteogenesis Study of Shell Nacre Cement with Older and Young Donor Bone Marrow Mesenchymal Stem/Stromal Cells

Bone void-filling cements are one of the preferred materials for managing irregular bone voids, particularly in the geriatric population who undergo many orthopedic surgeries. However, bone marrow mesenchymal stem/stromal cells (BM-MSCs) of older-age donors often exhibit reduced osteogenic capacity. Hence, it is crucial to evaluate candidate bone substitute materials with BM-MSCs from the geriatric population to determine the true osteogenic potential, thus simulating the clinical situation. With this concept, we investigated the osteogenic potential of shell nacre cement (SNC), a bone void-filling cement based on shell nacre powder and ladder-structured siloxane methacrylate, using older donor BM-MSCs (age > 55 years) and young donor BM-MSCs (age < 30 years). Direct and indirect cytotoxicity studies conducted with human BM-MSCs confirmed the non-cytotoxic nature of SNC. The standard colony-forming unit-fibroblast (CFU-F) assay and population doubling (PD) time assays revealed a significant reduction in the proliferation potential (p < 0.0001, p < 0.05) in older donor BM-MSCs compared to young donor BM-MSCs. Correspondingly, older donor BM-MSCs contained higher proportions of senescent, β-galactosidase (SA-β gal)-positive cells (nearly 2-fold, p < 0.001). In contrast, the proliferation capacity of older donor BM-MSCs, measured as the area density of CellTrackerTM green positive cells, was similar to that of young donor BM-MSCs following a 7-day culture on SNC. Furthermore, after 14 days of osteoinduction on SNC, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) showed that the amount of calcium and phosphorus deposited by young and older donor BM-MSCs on SNC was comparable. A similar trend was observed in the expression of the osteogenesis-related genes BMP2, RUNX2, ALP, COL1A1, OMD and SPARC. Overall, the results of this study indicated that SNC would be a promising candidate for managing bone voids in all age groups.

Intrafibrillar mineralization of type I collagen with calcium carbonate and strontium carbonate induced by polyelectrolyte-cation complexes

Calcium carbonate (CaCO3), possessing excellent biocompatibility, bioactivity, osteoconductivity and superior biodegradability, may serve as an alternative to hydroxyapatite (HAp), the natural inorganic component of bone and dentin. Intrafibrillar mineralization of collagen with CaCO3 was achieved through the polymer-induced liquid precursor (PILP) process for at least 2 days. This study aims to propose a novel pathway for rapid intrafibrillar mineralization with CaCO3 by sequential application of the carbonate-bicarbonate buffer and polyaspartic acid (pAsp)-Ca suspension. Fourier transform infrared (FTIR) spectroscopy, zeta potential measurements, atomic force microscopy/Kelvin probe force microscopy (AFM/KPFM), and three-dimensional stochastic optical reconstruction microscopy (3D STORM) demonstrated that the carbonate-bicarbonate buffer significantly decreased the surface potential of collagen and CO32-/HCO3- ions could attach to collagen fibrils via hydrogen bonds. The electropositive pAsp-Ca complexes and free Ca2+ ions are attracted to and interact with CO32-/HCO3- ions through electrostatic attractions to form amorphous calcium carbonate that crystallizes gradually. Moreover, like CaCO3, strontium carbonate (SrCO3) can deposit inside the collagen fibrils through this pathway. The CaCO3-mineralized collagen gels exhibited better biocompatibility and cell proliferation ability than SrCO3. This study provides a feasible strategy for rapid collagen mineralization with CaCO3 and SrCO3, as well as elucidating the tissue engineering of CaCO3-based biomineralized materials.

Graphene: A Multifaceted Carbon-Based Material for Bone Tissue Engineering Applications

Tissue engineering is an emerging technological field that aims to restore and replace human tissues. A significant number of individuals require bone replacement annually as a result of skeletal abnormalities or accidents. In recent decades, notable progress has been made in the field of biomedical research, specifically in the realm of sophisticated and biocompatible materials. The purpose of these biomaterials is to facilitate bone tissue regeneration. Carbon nanomaterial-based scaffolds are particularly notable due to their accessibility, mechanical durability, and biofunctionality. The scaffolds exhibit the capacity to enhance cellular proliferation, mitigate cell damage, induce bone tissue growth, and maintain biological compatibility. Therefore, they play a crucial role in the development of the bone matrix and the necessary cellular interactions required for bone tissue restoration. The attachment, growth, and specialization of osteogenic stem cells on biomaterial scaffolds play critical roles in bone tissue engineering. The optimal biomaterial should facilitate the development of bone tissue in a manner that closely resembles that of human bone. This comprehensive review encompasses the examination of graphene oxide (GO), carbon nanotubes (CNTs), fullerenes, carbon dots (CDs), nanodiamonds, and their respective derivatives. The biomaterial frameworks possess the ability to replicate the intricate characteristics of the bone microenvironment, thereby rendering them suitable for utilization in tissue engineering endeavors.

The Use of Shells of Marine Molluscs in Spanish Ethnomedicine: A Historical Approach and Present and Future Perspectives

Since ancient times, the shells of marine molluscs have been used as a therapeutic and/or prophylactic resource. In Spain, they were part of practical guides for doctors or pharmacists until the 19th century. In general, seashells were prepared by dissolving in vinegar and were part of plasters or powders used as toothpaste, or to treat dyspepsia, heartburn and leprosy. Thus, the nacre or mother-of-pearl of various molluscs was regularly used in the Royal Colleges of Surgery and in hospitals during the times of the Cortes of Cadiz, as a medicine in galenic preparations based on powders. In contemporary Spanish ethnomedicine, seashells, with a high symbolic value, have been used as an amulet to prevent cracks in the breasts and promote their development during lactation, to avoid teething pain in young children, to eliminate stains on the face or to cure erysipelas. But, as in other countries, products derived from seashells have also been empirically applied. The two resources used traditionally have been the cuttlebone, the internal shell of cuttlefish and the nacre obtained from the external shells of some species. Cuttlebone, dried and pulverised, has been applied externally to cure corneal leukoma and in dental hygiene. In the case of nacre, a distinction must be made between chemical and physical remedies. Certain seashells, macerated in lemon juice, were used in coastal areas to remove spots on the face during postpartum. However, the most common practice in Spain mainland was to dissolve mother-of-pearl buttons in lemon juice (or vinegar). The substance thus obtained has been used to treat different dermatological conditions of the face (chloasma, acne), as well as to eliminate freckles. For the extraction of foreign bodies in the eyes, a very widespread traditional remedy has been to introduce small mother-of-pearl buttons under the lid. These popular remedies and practices are compared with those collected in classic works of medicine throughout history, and data on the pharmacological activity and pharmaceutical applications of the products used are provided. The use of cuttlebone powders is supported by different works on anti-inflammatory, immune-modulatory and/or wound healing properties. Nacre powder has been used in traditional medicines to treat palpitations, convulsions or epilepsy. As sedation and a tranquilisation agent, nacre is an interesting source for further drug development. Likewise, nacre is a biomaterial for orthopaedic and other tissue bioengineering applications. This article is a historical, cultural and anthropological view that can open new epistemological paths in marine-derived product research.

Inhibitory Effect of Adsorption of Streptococcus mutans onto Scallop-Derived Hydroxyapatite

Hydroxyapatite adsorbs various substances, but little is known about the effects on oral bacteria of adsorption onto hydroxyapatite derived from scallop shells. In the present study, we analyzed the effects of adsorption of Streptococcus mutans onto scallop-derived hydroxyapatite. When scallop-derived hydroxyapatite was mixed with S. mutans, a high proportion of the bacterial cells adsorbed onto the hydroxyapatite in a time-dependent manner. An RNA sequencing analysis of S. mutans adsorbed onto hydroxyapatite showed that the upregulation of genes resulted in abnormalities in pathways involved in glycogen and histidine metabolism and biosynthesis compared with cells in the absence of hydroxyapatite. S. mutans adsorbed onto hydroxyapatite was not killed, but the growth of the bacteria was inhibited. Electron microscopy showed morphological changes in S. mutans cells adsorbed onto hydroxyapatite. Our results suggest that hydroxyapatite derived from scallop shells showed a high adsorption ability for S. mutans. This hydroxyapatite also caused changes in gene expression related to the metabolic and biosynthetic processes, including the glycogen and histidine of S. mutans, which may result in a morphological change in the surface layer and the inhibition of the growth of the bacteria.

Novel Bone Void Filling Cement Compositions Based on Shell Nacre and Siloxane Methacrylate Resin: Development and Characterization

Shell nacre from Pinctada species has been extensively researched for managing bone defects. However, there is a gap in the research regarding using shell nacre powder as a cement with improved biological and physicochemical properties. To address this, bone void filling cement was formulated by incorporating shell nacre powder and an organically modified ceramic resin (ormocer). The shell nacre powder was specifically processed from the shells of Pinctada fucata and analysed using thermogravimetric analysis (TGA), X-ray diffraction spectroscopy, Fourier transform infrared (FTIR), and Raman spectroscopy, confirming the presence of organic constituents and inorganic aragonite. Trace element analysis confirmed the eligibility of shell nacre powder for biomedical applications. Next, the ormocer SNLSM2 was synthesized through a modified sol-gel method. FTIR, Raman, TGA, and transmission electron microscopy studies revealed the presence of a ladder-structured siloxane backbone and methacrylate side chain. To develop chemical curable composite shell nacre cement (SNC), different amounts of shell nacre (24%, 48%, and 72%) were added to the SNLSM2 resin, and the impact on the physicochemical properties of the cement was studied. Among the compositions, SNC 72 exhibited significantly lower linear polymerization shrinkage (0.4%) and higher compressive (>100 MPa) and flexural strength (>35 MPa). SNC 72 was radiopaque, and the exotherm generated during the cement curing was minimal. Cytotoxicity studies with L929 cells revealed the non-cytotoxic nature of the cement. Overall, the findings of this study prove that the shell nacre cement is a promising candidate for managing bone voids.

Overview of structure, function and integrated utilization of marine shell

Marine shell resources have received great attention from researchers owing to their unique merits such as high hardness, good toughness, corrosion resistance, high adsorption, and bioactivity. Restricted by the level of comprehensive utilization technology, the utilization rate of shells is extremely low, resulting in serious waste and pollution. The research shows that the unique brick-mud structure of shells makes them have diverse and good functional characteristics, which guides them to have great utilization potential in different fields. Hence, this review highlights the constitutive relationship between microstructure-function-application of shells (e.g., gastropods, cephalopods, and amniotes), and the comprehensive applications and development ideas in the fields of biomedicine, adsorption enrichment, pHotocatalysis, marine carbon sink, and environmental deicer. It is worth mentioning that marine shells are currently well developed in three areas: bone repair, health care and medicinal value, and drug carrier, which together promote the progress of biomedical field. In addition, an in-depth summary of the application of marine shells in the adsorption and purification of various impurities such as crude oil, heavy metal ions and dyes at low-cost and high efficiency is presented. Finally, by integrating thoughts and approaches from different applications, we are committed to providing new pathways for the excavation and future high-value of shell resources, clarifying the existing development stages and bottlenecks, promoting the development of related technology industries, and achieving the synergistic win-win situation of economic and environmental benefits.

On the physicochemical properties, setting chemical reaction, and in vitro bioactivity of aragonite–chitosan composite cement as a bone substitute

A chitosan gel additive modulates the initial vaterite dissolution–recrystallisation in injectable aragonite-based composite cement and promotes its in vitro bioactivity.

Mechanical and Recyclable Properties of Polyimine Enhanced by Biomimetic Modification of Graphene Oxide Sheets/Silicon Carbide Nano-Whiskers

Inspired by the mineral bridge between hard phase layers of natural nacre, the biomimetic modified silicon carbide nano-whiskers (MSiCw)/graphene oxide sheets (MGO) reinforced polyimine (PI) composites (MSiCw-MGO-PI) were successfully prepared by heat-pressing at room temperature, which confirmed by FTIR, XPS, and XRD tests. According to the results of mechanical tests, the composites with filling weights of MSiCw and MGO, which were found to be 1% and 0.3%, presented tensile strength of 94.27 MPa, which was 32% higher than the matrix. With the additional weights amount of 1%MSiCw and 0.2%MGO, the impact strength of the composites reached 17.46 KJ/m², which was increased by 81% compared with the matrix. In addition, the reinforcing mechanisms, such as the bridging principle and mechanism of whiskers pulling out, were investigated by analyzing the fracture surface of MSiCw-MGO-PI composites. The results showed that MSiCw and MGO can synergistically improve the mechanical properties of the composites. In addition, the recyclability of the composites valued by the mechanical properties of the composites from regrinding and heat pressing showed that three generations of MSiCw-MGO-PI composites can still maintain high mechanical properties on account of the better dispersion of the reinforcing phases in the matrix from regrinding.

Organic Matrix and Secondary Metabolites in Nacre

Nacre, also called mother-of-pearl, is a naturally occurring biomineral, largely studied by chemists, structural biologists, and physicists to understand its outstanding and diverse properties. Nacre is constituted of aragonite nanograins surrounded by organic matrix, and it has been established that the organic matrix is responsible for initiating and guiding the biomineralization process. The first challenge to study the organic matrix of nacre lays in its separation from the biomineral. Several extraction methods have been developed so far. They are categorized as either strong (e.g., decalcification) or soft (e.g., water, ethanol) and they allow specific extractions of targeted compounds. The structure of the nacreous organic matrix is complex, and it provides interesting clues to describe the mineralization process. Proteins, sugars, lipids, peptides, and other molecules have been identified and their role in mineralization investigated. Moreover, the organic matrix of nacre has shown interesting properties for human health. Several studies are investigating its activity on bone mineralization and its properties for skin care. In this review, we focus on the organic constituents, as lipids, sugars, and small metabolites which are less studied since present in small quantities.

Preclinical safety study of nacre powder in an intraosseous sheep model

Objectives

The purpose of this preclinical study was to evaluate the safety, the local tissue effects and bone healing performance (osteoconduction, osseointegration) of nacre powder in a sheep intraosseous implantation model. This represents the first preclinical study to assess nacre safety and efficacy in supporting new bone formation in accordance with the ISO 10993 standard for biomedical devices.

Methods

The local tissue effects and the material performance were evaluated 8 weeks after implantation by qualitative macroscopic observation and qualitative as well as semiquantitative microscopic analyses of the bone sites. Histopathological characterisations were run to assess local tissue effects. In addition, microarchitectural, histomorphometric and histological characterisations were used to evaluate the effects of the implanted material.

Results

Nacre powder was shown to cause a moderate inflammatory response in the site where it was implanted compared with the sites left empty. The biomaterial implanted within the generated defects was almost entirely degraded over the investigated time span and resulted in the formation of new bone with a seamless connection with the surrounding tissue. On the contrary, in the empty defects, the formation of a thick compact band of sclerotic bone was observed by both microarchitectural and histological characterisation.

Conclusions

Nacre powder was confirmed to be a safe biomaterial for bone regeneration applications in vivo, while supporting bone formation.

The proteomics of the freshwater pearl powder: Insights from biomineralization to biomedical application

The freshwater pearl is one kind of valuable organic jewelry and traditional Chinese medicine (TCM). However, the molecular basis of matrix protein in pearl biomineralization and biomedical applications are largely unknown to date. In this study, the matrix proteins of water-soluble matrix, acid-soluble matrix and acid-insoluble matrix from the freshwater seedless pearl powder were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS) respectively, and identified against the transcriptomic database of the pearl sac. The results showed that a total of 190 proteins were identified in pearl proteomics, which was divided into eight categories by their potential biomineralization functions. The composition of pearl matrix proteins and the high frequency conserved domains like carbonic anhydrase, von Willebrand factor type A, tyrosinase and chitin binding 2 in protein sequences, implying that the "chitin-silk fibroin gel proteins-acidic macromolecules" model was suitable for description the pearl biomineralization process. Meanwhile, ninety-one of pearl matrix proteins could be classified into seven categories by their potential medical functions including wound healing, osteogenic property, antioxidant activity, neuro-regulation effects, skin lightening effect, anti-inflammatory and anti-apoptotic effects and other immunomodulatory property. In general, these results provided valuable new insights into not only the diversity of pearl matrix protein for mollusc biomineralization, but the molecular basis of pearl matrix proteins responsible for their diverse biological properties in TCM application. SIGNIFICANCE: The significance of this study included the following points.

Pearl-inspired graphene oxide-collagen microgel with multi-layer mineralization through microarray chips for bone defect repair

Biomineralization of natural polymers in simulated body fluid (SBF) can significantly improve its biocompatibility, osteoconductivity, and osteoinductivity because of the hydroxyapatite (HAp) deposition. Nevertheless, the superficial HAp crystal deposition hamper the deep inorganic ions exchange in porous microgels, thus gradually leading to a nonuniform regeneration effect. Inspired by the pearl forming process, this article uses the microarray chips to fabricate the multi-layer mineralized graphene oxide (GO)-collagen (Col)-hydroxyapatite (HAp) microgel, denoted as MMGCH. These fabricated MMGCH microgels exhibit porous structure and uniform HAp distribution. Furthermore, the suitable microenvironment offered by microgel promotes the time-dependent proliferation and osteogenic differentiation of stem cells, which resulted in upregulated osteogenesis-related genes and proteins, such as alkaline phosphatase, osteocalcin, and collagen-1. Finally, the MMGCH microgels possess favorable bone regeneration capacities both in cranial bone defects and mandibular bone defects via providing a suitable microenvironment for host-derived cells to form new bone tissues. This work presents a biomimetic means aiming to achieve full-thickness and uniform HAp deposition in hydrogel for bone defect repair.

Protective effect on bone of nacre supplementation in ovariectomized rats

Nacre has emerged as a beneficial natural product for bone cells and tissues, but its effect was only studied by gavage in the ovariectomized mouse model. We sought to assess the antiosteoporotic effect of nacre through a nutritional supplementation in the ovariectomized rat model. Sixteen‐week‐old female Wistar rats were either Sham‐operated or bilateral ovariectomized (OVX) and then fed with standard diet (Sham and OVX groups) or standard diet supplemented with either 0.25% CaCO₃ or nacre (OVX CaCO₃ and OVX Nacre group, respectively) for 28 days (n = 10/group). The bone microarchitecture was assessed at appendicular and axial bones by micro‐computed tomography (μCT). Histomorphometric analysis was performed to determine cellular and dynamic bone parameters. Bone metabolism was also evaluated by biochemical markers and gene expression levels. Nacre‐based diet prevented the OVX‐induced bone loss better than that of the CaCO₃ supplement, given the significant changes in trabecular bone volume fraction (BV/TV) both at the femoral distal metaphysis (difference, 35%; p = 0.004) and at the second lumbar spine (difference, 11%; p = 0.01). Trabecular osteoclast surfaces (Oc.S/BS) were also 1.5‐fold lower at the tibial proximal metaphysis in OVX Nacre group compared with OVX CaCO₃ group (p = 0.02)_. By principal component analysis (PCA), OVX Nacre group formed a cluster away from OVX group and with a trend closest to Sham group. These data were consistent with biological measurements demonstrating a positive profile related to nacre supplementation, which blunted an increase in serum CTX level and enhanced serum P1NP secretion 14 days post‐OVX compared with CaCO₃ supplementation. Bmp2 mRNA expression in OVX Nacre group was +1.76‐fold (p = 0.004) and +1.30‐fold (p = 0.20) compared with OVX and OVX CaCO₃ groups, respectively. We conclude that supplementation with nacre could effectively limit bone loss induced by estrogen deficiency just after OVX in rats by modulating the negative imbalance of bone turnover. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

A sustainable single-component "Silk nacre"

Synthetic composite materials constructed by hybridizing multiple components are typically unsustainable due to inadequate recyclability and incomplete degradation. In contrast, biological materials like silk and bamboo assemble pure polymeric components into sophisticated multiscale architectures, achieving both excellent performance and full degradability. Learning from these natural examples of bio-based "single-component" composites will stimulate the development of sustainable materials. Here, we report a single-component "Silk nacre," where nacre's typical "brick-and-mortar" structure has been replicated with silk fibroin only and by a facile procedure combining bidirectional freezing, water vapor annealing, and densification. The biomimetic design endows the Silk nacre with mechanical properties superior to those of homogeneous silk material, as well as to many frequently used polymers. In addition, the Silk nacre shows controllable plasticity and complete biodegradability, representing an alternative substitute to conventional composite materials.

Induction of Osseointegration by Nacre in Pigs

Nacre is a biomaterial that has shown osteoinductive and osteoconductive properties in vitro and in vivo. These properties make nacre a material of interest for inducing bone regeneration. However, information is very limited regarding the introduction of nacre to dental implant surgery for promoting osteogenesis. This study investigated the potential of nacre powder for peri-implant bone regeneration in a porcine model. Ninety-six dental implants were placed into the tibia of twelve male domestic pigs. The dental implants were coated with nacre powder from the giant oyster before implantation. Implantations without nacre powder were used as control groups. Euthanization took place at 2, 4 and 6 weeks after implantation, after which we measured bone-to-implant contact (BIC) and bone volume density (BVD) of the implanted bone samples using micro-computed tomography (micro-CT), and examined the histology of the surrounding bone using histological sections stained with Stevenel’s blue and Alizarin red S. The micro-CT analyses showed that the BIC of dental implantations with nacre powder were significantly higher than those without nacre powder, by 7.60%. BVD of implantations with nacre powder were significantly higher than those without nacre powder, by 12.48% to 13.66% in cortical bone, and by 3.37% to 6.11% in spongy bone. Histological study revealed more peri-implant bone regeneration toward the surface of the dental implants after implantation with nacre powder. This was consistent with the micro-CT results. This study demonstrates the feasibility of using nacre to promote peri-implant bone regeneration in dental implantation.

Silk-based bioinspired structural and functional materials

Natural biological materials provide a rich source of inspiration for building high-performance materials with extensive applications. By mimicking their chemical compositions and hierarchical architectures, the past decades have witnessed the rapid development of bioinspired materials. As a very promising biosourced raw material, silk is drawing increasing attention due to excellent mechanical properties, favorable versatility, and good biocompatibility. In this review, we provide an overview of the recent progress in silk-based bioinspired structural and functional materials. We first give a brief introduction of silk, covering its sources, features, extraction, and forms. We then summarize the preparation and application of silk-based materials mimicking four typical biological materials including bone, nacre, skin, and polar bear hair. Finally, we discuss the current challenges and future prospects of this field.

Pinctada Maxima Pearl Shells as a Promising Bone Graft Material in the World of Dentistry

BACKGROUND: Pinctada maxima pearl shell contains inorganic and organic materials that have a bone-like basic structure that facilitates bone remodeling. AIM: This study aimed to describe the effectiveness of Pinctada maxima pearl shells as bone graft material in the world of dentistry using an animal model. METHODS: Research uses Pinctada maxima pearl shell that was processed into hydroxyapatite Pinctada maxima (HPM) powder. Chemical and surface characteristics of HPM were performed with X-ray fluorescence (XRF), Fourier transform infra-red (FTIR), and X-ray diffraction (XRD), respectively. Thirty male guinea pigs were randomly assigned into three groups: Negative control (NC), positive control, and HPM. After 14–21 days of observation, guinea pigs were sacrificed. Bone formation was seen through immunohistochemical examination of osteoprotegerin (OPG) and bone morphogenetic protein (BMP2) expression. Data were analyzed through Shapiro wills and analysis of variance with a significance level of 5%. RESULTS: There was a high expression of OPG and BMP2 on days 14–21 in the HPM group when compared to the NC group with a significance level of 5%. CONCLUSION: HPM powder can be used as a promising bone graft material in the world of dentistry.

Corrosion Behavior and Biocompatibility of Na2EDTA-Induced Nacre Coatings on AZ91D Alloys Prepared via Hydrothermal Treatment

An effective method for controlling the corrosion rate of Mg-based implants must be urgently developed to meet the requirements of clinical applications. As a naturally occurring osteoid material, nacre offers a strategy to endow biomedical Mg alloys with excellent biocompatibility, and corrosion resistance. In this study, pearl powder and NaH2PO4 were used as precursors to deposit coatings on AZ91D alloy substrates hydrothermally based on Na2EDTA-assisted induction. Na2EDTA-induced nacre coatings were fabricated at various pH values, and its chemical composition and microstructure were analyzed via energy-dispersive X-ray, scanning electron microscopy, and X-ray diffraction spectroscopy. The corrosion-resistant performance and cytocompatibility of the samples were evaluated via electrochemical measurements and in vitro cell experiments. Results showed that the samples hydrothermally treated under faint acid conditions present excellent corrosion resistance, whereas the samples treated under slight alkaline conditions demonstrate improved biocompatibility due to high Ca and P content and large Ca/P atomic ratio. This study provides substantial evidence of the potential value of nacre coatings in expanding the biological applications of implanted biomaterials.

Natural Biomaterials from Biodiversity for Healthcare Applications

Natural biomaterials originating during the growth cycles of all living organisms have been used for many applications. They span from bioinert to bioactive materials including bioinspired ones. As they exhibit an increasing degree of sophistication, natural biomaterials have proven suitable to address the needs of the healthcare sector. Here the different natural healthcare biomaterials, their biodiversity sources, properties, and promising healthcare applications are reviewed. The variability of their properties as a result of considered species and their habitat is also discussed. Finally, some limitations of natural biomaterials are discussed and possible future developments are provided as more natural biomaterials are yet to be discovered and studied.

Biocompatibility pathways and mechanisms for bioactive materials: The bioactivity zone

This essay analyzes the scientific evidence that forms the basis of bioactive materials, covering the fundamental understanding of bioactivity phenomena and correlation with the mechanisms of biocompatibility of biomaterials. This is a detailed assessment of performance in areas such as bone-induction, cell adhesion, immunomodulation, thrombogenicity and antimicrobial behavior. Bioactivity is the modulation of biological activity by characteristics of the interfacial region that incorporates the material surface and the immediate local host tissue. Although the term ‘bioactive material’ is widely used and has a well understood general meaning, it would be useful now to concentrate on this interfacial region, considered as ‘the bioactivity zone’. Bioactivity phenomena are either due to topographical/micromechanical characteristics, or to biologically active species that are presented in the bioactivity zone. Examples of topographical/micromechanical effects are the modulation of the osteoblast – osteoclast balance, nanotopographical regulation of cell adhesion, and bactericidal nanostructures. Regulation of bioactivity by biologically active species include their influence, especially of metal ions, on signaling pathways in bone formation, the role of cell adhesion molecules and bioactive peptides in cell attachment, macrophage polarization by immunoregulatory molecules and antimicrobial peptides. While much experimental data exists to demonstrate the potential of such phenomena, there are considerable barriers to their effective clinical translation. This essay shows that there is solid scientific evidence of the existence of bioactivity mechanisms that are associated with some types of biomaterials, especially when the material is modified in a manner designed to specifically induce that activity.

Pearl Powder-An Emerging Material for Biomedical Applications: A Review

Pearl powder is a well-known traditional Chinese medicine for a variety of indications from beauty care to healthcare. While used for over a thousand years, there has yet to be an in-depth understanding and review in this area. The use of pearl powder is particularly growing in the biomedical area with various benefits reported due to the active ingredients within the pearl matrix itself. In this review, we focus on the emerging biomedical applications of pearl powder, touching on applications of pearl powder in wound healing, bone repairing, treatment of skin conditions, and other health indications.

Extraction, Purification, Bioactivities and Application of Matrix Proteins From Pearl Powder and Nacre Powder: A Review

Natural pearls are formed when sand or parasites (irritants) accidentally enter into the oyster body and form pearls under the cover of the nacre layer. Pearl powder is a powdery substance by grinding pearls into small grains, however, the nacre powder is the inner layer of outer corner layer and middle prism layer. Pearl medicine in China has a history of more than 2,000 years, pearl has the effects of calming the mind, clearing the eyes, detoxifying the muscle and so on. In this paper, the researches on the extraction of pearl powder and nacre powder, the isolation and purification of matrix protein and the various biological activities (osteogenic activity, antioxidant, anti-inflammatory, anti-apoptotic, promoting the migration of fibroblasts, and so on) are reviewed in detail. To provide readers with a faster understanding, the method of extraction and purification and the application of nacre powder and pearl powder are clearly presented in the form of figures and tables. In line with the concept of waste or by-product, there are more reports of nacre extract than pearl extract, due to the expensive and limited in origin of pearls. Mainly on the direct use of nacre powder and pearl powder or on the use of extracts (mainly water soluble proteins) through experiments in vivo or in vitro, and shows whether it is effective through the results of various indexes. There is no further study on substances other than extracts, and the structural analysis of extracts needs further exploration.

[Experimental study on repairing rabbit skull defect with bone morphogenetic protein 2 peptide/functionalized carbon nanotube composite]

Objective

To observe and compare the effects of peptides on the repair of rabbit skull defects through two different binding modes of non-covalent and covalent, and the combination of carboxyl (-COOH) and amino (-NH ₂) groups with materials.

Methods

Twenty-one 3-month-old male ordinary New Zealand white rabbits were numbered 1 to 42 on the left and right parietal bones. They were divided into 5 groups using a random number table, the control group (group A, 6 sides) and the material group 1, 2, 3, 4 (respectively group B, C, D, E, 9 sides in each group). All animals were prepared with 12-mm-diameter skull defect models, and bone morphogenetic protein 2 (BMP-2) non-covalently bound multiwalled carbon nanotubes (MWCNT)-COOH+poly ( L-lactide) (PLLA), BMP-2 non-covalently bound MWCNT-NH ₂+PLLA, BMP-2 covalently bound MWCNT-COOH+PLLA, and BMP-2 covalently bound MWCNT-NH ₂+PLLA were implanted into the defects of groups B, C, D, and E, respectively. At 4, 8, and 12 weeks after operation, the samples were taken for CT scanning and three-dimensional reconstruction, the ratio of bone tissue regeneration volume to total volume and bone mineral density were measured, and the histological observation of HE staining and Masson trichrome staining were performed to quantitatively analyze the volume ratio of new bone tissue.

Results

CT scanning and three-dimensional reconstruction showed that with the extension of time, the defects in groups A-E were filled gradually, and the defect in group E was completely filled at 12 weeks after operation. HE staining and Masson trichrome staining showed that the volume of new bone tissue in each group gradually increased with time, and regenerated mature bone tissue appeared in groups D and E at 12 weeks after operation. Quantitative analysis showed that at 4, 8, and 12 weeks after operation, the ratio of bone tissue regeneration volume to total volume, bone mineral density, and the volume ratio of new bone tissue increased gradually over time; and at each time point, the above indexes increased gradually from group A to group E, and the differences between groups were significant ( P<0.05).

Conclusion

Through covalent binding and using -NH ₂ to bound peptides with materials, the best bone repair effect can be achieved.

Hierarchical Assembly of Atomically Precise Metal Clusters as a Luminescent Strain Sensor

We demonstrate the formation of a versatile luminescent organo-inorganic layered hybrid material, composed of bovine serum albumin (BSA)-protected Au₃₀ clusters and aminoclay sheets. X-ray diffraction revealed the intercalation of Au₃₀@BSA in the layered superstructure of aminoclay sheets. Coulombic attraction of the clusters and the clay initiates the interaction, and the appropriate size of the clusters allowed them to intercalate within the lamellar aminoclay galleries. Electron microscopy measurements confirmed the hierarchical structure of the material and also showed the cluster-attached clay sheets. Zeta potential measurement and dynamic light scattering probed the gradual formation of the ordered aggregates in solution. The hybrid material could be stretched up to 300% without fracture. The emergence of a new peak in the luminescence spectrum was observed during the course of mechanical stretching. This peak increased in intensity gradually with the degree of elongation or strain of the material. A mechanochromic luminescence response was further demonstrated with a writing experiment on a luminescent mat of the material, made by electrospinning.

Co-inspired hydroxyapatite-based scaffolds for vascularized bone regeneration

Hydroxyapatite (HA) is the main inorganic component of human bone. Inspired by nacre and cortical bone, hydroxyapatite-based coil scaffolds were successfully prepared. The scaffolds presented "brick and mortar" multi-layered structure of nacre and multi-layered concentric circular structure of cortical bone. Because of bioactive components and hierarchical structure, the scaffolds possessed good compressive strength (≈95 MPa), flexural strength (≈161 MPa) and toughness (≈1.1 MJ/m³). In addition, they showed improved angiogenesis and osteogenesis in rat and rabbit critical sized bone defect models. By mimicking co-biological systems, this work provided a feasible strategy to optimize the properties of traditional tissue engineering biological materials for vascularized bone regeneration.

A comparative study on the mechanical and structural design of nacre in gastropod and bivalve molluscs

The lesson learnt from nature is presented through the examination of shells from four mollusc species (two gastropods and two bivalves). Individual aragonite tablets together with the organic network have been studied in terms of tablet dimensions, tablet stacking sequence, texture and the weight fraction of the organic present in these bio-composite shells. Mechanical properties viz. elastic modulus and hardness at the macro (bulk), micro (tablet) and nano (aragonite nanograins) levels have been determined using the experimental technique of nanoindentation together with the theoretical formulations offered by the Mori-Tanaka method and other such mechanical models for composites. XRD studies confirm the strong c-axis crystallographic orientation - aligned parallel to the direction of growth and crystallization of nacreous tablets, and fractography performed on the shell specimens suggests a difference in the stacking of individual aragonite layers for the gastropod and bivalve molluscan class, respectively. DSC and TG-DTA data helped in characterizing the organic material present in the shell specimens and in calculating the organic weight and volume fractions across species. Further to this, the DSC data revealed that the nature of the organic in the brick and mortar assembly of nacre, was similar in nature across the two molluscan classes reported in this study. EBSD studies performed on our system revealed a difference in crystallographic texture for the two different tablet stacking (columnar and sheet nacre). It has been shown experimentally that the shells of gastropods (columnar nacre) are orthotropic in nature, while the bivalve mollusc shells (sheet nacre) are anisotropic in nature.

Progress in Modern Marine Biomaterials Research

The growing demand for new, sophisticated, multifunctional materials has brought natural structural composites into focus, since they underwent a substantial optimization during long evolutionary selection pressure and adaptation processes. Marine biological materials are the most important sources of both inspiration for biomimetics and of raw materials for practical applications in technology and biomedicine. The use of marine natural products as multifunctional biomaterials is currently undergoing a renaissance in the modern materials science. The diversity of marine biomaterials, their forms and fields of application are highlighted in this review. We will discuss the challenges, solutions, and future directions of modern marine biomaterialogy using a thorough analysis of scientific sources over the past ten years.

Progress in Bioinspired Dry and Wet Gradient Materials from Design Principles to Engineering Applications

Nature does nothing in vain. Through millions of years of revolution, living organisms have evolved hierarchical and anisotropic structures to maximize their survival in complex and dynamic environments. Many of these structures are intrinsically heterogeneous and often with functional gradient distributions. Understanding the convergent and divergent gradient designs in the natural material systems may lead to a new paradigm shift in the development of next-generation high-performance bio-/nano-materials and devices that are critically needed in energy, environmental remediation, and biomedical fields. Herein, we review the basic design principles and highlight some of the prominent examples of gradient biological materials/structures discovered over the past few decades. Interestingly, despite the anisotropic features in one direction (i.e., in terms of gradient compositions and properties), these natural structures retain certain levels of symmetry, including point symmetry, axial symmetry, mirror symmetry, and 3D symmetry. We further demonstrate the state-of-the-art fabrication techniques and procedures in making the biomimetic counterparts. Some prototypes showcase optimized properties surpassing those seen in the biological model systems. Finally, we summarize the latest applications of these synthetic functional gradient materials and structures in robotics, biomedical, energy, and environmental fields, along with their future perspectives. This review may stimulate scientists, engineers, and inventors to explore this emerging and disruptive research methodology and endeavors.

The effects of oyster shell/alpha-calcium sulfate hemihydrate/platelet-rich plasma/bone mesenchymal stem cells bioengineering scaffold on rat critical-sized calvarial defects

Engineering scaffolds combining natural biomineral and artificially synthesized material hold promising potential for bone tissue regeneration. We fabricated a bioengineering scaffold, oyster shell (OS) and alpha-calcium sulfate hemihydrate (α-CSH) as scaffold, platelet-rich plasma (PRP) as provider of growth factors and bone mesenchymal stem cells (BMSCs) as seed cells, and determined it could be applied as a new type of bone graft substitutes by rat calvarial defects repairing experiment in vitro and in vivo. SEM showed that the mean diameter of the pores was about 150 μm with a range of 50-200 μm, and scaffold's porosity was ~27.4% by Archimedes' Principle. In vitro, Scaffold + BMSCs + PRP group presented a higher ALP activity compared with other groups by ELISA (P < 0.05). But the expression of OC was not detectable on day 4 or 8. The MTT assay showed that the relative cell number of BMSCs+PRP group increased significantly (P < 0.05). In vivo, the smallest defect area of skull and highest volume of regenerated new bone were observed in Scaffold + PRP + BMSCs group by X-ray and Micro-CT analysis (P < 0.05). And the similar results also were observed in HE and Masson staining. The immunohistochemistry staining for osteogenic marker proteins ALP and OC showed that the most obvious positive staining was observed in Scaffold + PRP + BMSCs group (P < 0.05). The expression of inflammatory markers IL-6 and TNF-α was the lowest in control group (P < 0.05). In conclusion, a bioengineering scaffold based on OS, created by simply combining α-CSH and PRP and implanting with BMSCs, could be clinically useful and has marked advantages as a targeted, off-the-shelf, cell-loaded treatment option for the bone healing of critical-size calvarial defects.

Effects of the Sintering Process on Nacre-Derived Hydroxyapatite Scaffolds for Bone Engineering

A hydroxyapatite scaffold is a suitable biomaterial for bone tissue engineering due to its chemical component which mimics native bone. Electronic states which present on the surface of hydroxyapatite have the potential to be used to promote the adsorption or transduction of biomolecules such as protein or DNA. This study aimed to compare the morphology and bioactivity of sinter and nonsinter marine-based hydroxyapatite scaffolds. Field emission scanning electron microscopy (FESEM) and micro-computed tomography (microCT) were used to characterize the morphology of both scaffolds. Scaffolds were co-cultured with 5 × 104/cm2 of MC3T3-E1 preosteoblast cells for 7, 14, and 21 days. FESEM was used to observe the cell morphology, and MTT and alkaline phosphatase (ALP) assays were conducted to determine the cell viability and differentiation capacity of cells on both scaffolds. Real-time polymerase chain reaction (rtPCR) was used to identify the expression of osteoblast markers. The sinter scaffold had a porous microstructure with the presence of interconnected pores as compared with the nonsinter scaffold. This sinter scaffold also significantly supported viability and differentiation of the MC3T3-E1 preosteoblast cells (p < 0.05). The marked expression of Col1α1 and osteocalcin (OCN) osteoblast markers were also observed after 14 days of incubation (p < 0.05). The sinter scaffold supported attachment, viability, and differentiation of preosteoblast cells. Hence, sinter hydroxyapatite scaffold from nacreous layer is a promising biomaterial for bone tissue engineering.

Comparing the regeneration potential between PLLA/Aragonite and PLLA/Vaterite pearl composite scaffolds in rabbit radius segmental bone defects

Mussel-derived nacre and pearl, which are natural composites composed CaCO₃ platelets and interplatelet organic matrix, have recently gained interest due to their osteogenic potential. The crystal form of CaCO₃ could be either aragonite or vaterite depending on the characteristics of mineralization template within pearls. So far, little attention has been paid on the different osteogenic capacities between aragonite and vaterite pearl. In the current work, aragonite or vaterite pearl powders were incorporated into poly-l-lactic acid (PLLA) scaffold as bio-functional fillers for enhanced osteogenesis. In intro results revealed that PLLA/aragonite scaffold possessed stronger stimulatory effect on SaOS-2 cell proliferation and differentiation, evidenced by the enhanced cell viability, alkaline phosphatase activity, collagen synthesis and gene expressions of osteogenic markers including osteocalcin, osteopotin and bone sialoprotein. The bone regeneration potential of various scaffolds was evaluated in vivo employing a rabbit critical-sized radial bone defect model. The X-ray and micro-CT results showed that significant bone regeneration and bridging were achieved in defects implanted with composite scaffolds, while less bone formation and non-bridging were found for pure PLLA group. Histological evaluation using Masson's trichrome and hematoxylin/eosin (H&E) staining indicated a typical endochondral bone formation process conducted at defect sites treated with composite scaffolds. Through three-point bending test, the limbs implanted with PLLA/aragonite scaffold were found to bear significantly higher bending load compared to other two groups. Together, it is suggested that aragonite pearl has superior osteogenic capacity over vaterite pearl and PLLA/aragonite scaffold can be employed as a potential bone graft for bone regeneration.

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PLLA/pearl powder composite scaffolds with interconnected pores were fabricated.

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PLLA/aragonite scaffold stimulated SaOS-2 cell proliferation and differentiation.

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PLLA/aragonite scaffold promoted bone regeneration in vivo.

The Role of Marine Organic Extract in Bone Regeneration: A Pilot Study

Novel biomaterials capable of accelerating the healing process of skeletal tissues are urgently needed in dentistry. The present in vivo study assessed the osteoconductive and osteoinductive properties of experimental biphasic bioceramics (HA-TCP) modified or not by a nacre extract (marine organic extract, MOE) in a sheep model. Fabrication of MOE involved mixing ground nacre (0.05 g, particle sizes < 0.1 mm) with glacial ethanoic acid (5 mL, pH 7) for 72 hours using external magnetic stirring (25°C). Nonreactive carriers (sterile polythene tubes; 3/animal, radius: 2.5 mm, length: 10.0 mm) pertaining to the control (empty) or experimental groups (HA-TCP or MOE-modified HA-TCP) were implanted intramuscularly into the abdominal segment of the torso in sheep (n = 8, age: 2 years, weight: 45 kg). Euthanization of animals was performed at 3 and 6 months after surgery. Tissues harvested were subjected to macroscopic and radiographic assessments. Specimens were then stained for histological analysis. Both control and experimental animals were capable of inducing the neoformation of fibrous connective tissue at both time points where superior amounts of tissue formation and mineralization were detected for experimental groups (unaltered (at 3 and 6 mos) and MOE-modified HA-TCP (at 3 mos)). Histological results, however, revealed that mature bone formation was only observed for specimens fabricated with MOE-modified HA-TCP in a time-dependent manner. The present study has successfully demonstrated the in vivo utility of experimental biphasic bioceramics modified by MOE in an ectopic grafting sheep model. Promising osteoconductive and osteoinductive properties must be further developed and confirmed by subsequent research.

Pires R, Botelho G, Reis RL, Alves NM. Spin-Coated Polysaccharide-Based Multilayered Freestanding Films with Adhesive and Bioactive Moieties

Freestanding films based on catechol functionalized chitosan (CHI), hyaluronic acid (HA), and bioglass nanoparticles (BGNPs) were developed by spin-coating layer-by-layer assembly (SA-LbL). The catechol groups of 3,4-dihydroxy-l-phenylalanine (DOPA) present in the marine mussels adhesive proteins (MAPs) are the main factors responsible for their characteristic strong wet adhesion. Then, the produced films were cross-linked with genipin to improve their stability in wet state. Overall, the incorporation of BGNPs resulted in thicker and bioactive films, hydrophilic and rougher surfaces, reduced swelling, higher weight loss, and lower stiffness. The incorporation of catechol groups onto the films showed a significant increase in the films' adhesion and stiffness, lower swelling, and weight loss. Interestingly, a synergetic effect on the stiffness increase was observed upon the combined incorporation of BGNPs with catechol-modified polymers, given that such films were the stiffest. Regarding the biological assays, the films exhibited no negative effects on cellular viability, adhesion, and proliferation, and the BGNPs seemed to promote higher cellular metabolic activity. These bioactive LbL freestanding films combine enhanced adhesion with improved mechanical properties and could find applications in the biomedical field, such as guided hard tissue regeneration membranes.

Pisidium coreanum Inhibits Multinucleated Osteoclast Formation and Prevents Estrogen-Deficient Osteoporosis

Mollusks have served as important sources of human food and medicine for a long time. Raw Pisidium coreanum, a freshwater bivalve of the phylum Mollusca, is used in traditional therapies in parts of Asia. However, the therapeutic effects of Pisidium coreanum on bone diseases are not known. We investigated the functional roles of Pisidium coreanum in osteoporotic bone diseases. Pisidium coreanum inhibited the differentiation of bone marrow-derived monocytic cells into mature osteoclasts in vitro. The ovariectomized mice that received oral administration of Pisidium coreanum showed improvements in both trabecular and cortical bones. This preventive activity of Pisidium coreanum against bone loss was due to limited osteoclast maturation with reduced osteoclast surface extent in trabecular bone tissue. The formation of large multinucleated osteoclasts in vitro was significantly decreased in response to Pisidium coreanum, consistent with the reduced expression levels of osteoclast markers and fusion-related genes, such as NFATc1, p65, integrinαvβ3, DC-STAMP, OC-STAMP, Atp6v0d2, FAK, CD44, and MFR. These data suggest that Pisidium coreanum inhibits osteoclast differentiation by negatively regulating the fusion of mononuclear osteoclast precursors. Thus, our data demonstrate the ability of Pisidium coreanum to effectively prevent estrogen-deficient osteoporosis through inhibition of multinucleated osteoclast formation.

Interlock or Chemical Bond: Investigation on the Interface of Graphene Oxide and Styrenic Block Copolymers as Layer-by-Layer Films

In the paper, graphene oxide (GO) and two kinds of styrenic resins, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and maleic anhydride (MA) grafted SEBS (MA-g-SEBS), were utilized to explore the interfacial interaction of carbon-based materials and block copolymers as layer-by-layer (LBL) assembly films. The details of the interlayer interaction of the two kinds of composite films were investigated through the analysis of the mechanical properties and internal structure of the composites. For the SEBS/GO composite film, the "interlock" structure tended to form between the GO sheets and SEBS resin, and the physical "interlocking effect" could make full use of the excellent mechanical properties of GO nanosheets. As a result, both failure strength and elongation at break of the SEBS/GO composite film were enhanced by 50 and 25%, respectively. On the other hand, some different structures were found in the MA-g-SEBS/GO composite film, where the GO sheets stacked onto the resin closely because of the chemical interaction between them and no obvious "interlocks" was found within the interface, and the chemical interface interaction was strong enough to prevent the slide of GO nanosheets under tension after the graphene sheets were highly oxidized, so the mechanical properties of the MA-g-SEBS/GO composite film could be also enhanced. Based on an overall consideration of the research results of these LBL assembled composites, choosing more perfect materials and structures is needed, which should use physical and chemical interfacial interactions more efficiently, to obtain better mechanical properties of inorganic carbon-organic resin composites.

Preparation, Characterization and In Vitro Biological Evaluation of a Novel Pearl Powder/Poly-Amino Acid Composite as a Potential Substitute for Bone Repair and Reconstruction

Many studies about fabricating organic-inorganic composite materials have been carried out in order to mimic the natural structure of bone. Pearl, which has a special block-and-mortar hierarchical structure, is a superior bone repair material with high osteogenic activity, but it shows few applications in the clinical bone repair and reconstruction because of its brittle and uneasily shaped properties. In this work, pearl powder (P)/poly (amino acid) (PAA) composites were successfully prepared by a method of in situ melting polycondensation to combine the high osteogenic activity of the pearl and the pliability of the PAA. The mechanical properties, in vitro bioactivity and biocompatibility as well as osteogenic activity of the composites were investigated. The results showed that P/PAA composites have both good mechanical properties and bioactivity. The compressive strength, bending strength and tensile strength of the composites reached a maximum of 161 MPa, 50 MPa and 42 MPa, respectively; in addition, apatite particles successfully deposited on the composites surface after immersion in simulated body fluid (SBF) for 7 days indicated that P/PAA composites showed an enhanced mineralization capacity and bioactivity due to incorporation of pearl powder and PAA. The cell culture results revealed that higher cell proliferation and better adhesion morphology of mouse bone marrow mesenchymal stem cells (MSCs) appeared on the composite surface. Moreover, cells growing on the surface of the composites exhibited higher alkaline phosphatase (ALP) activity, more calcium nodule-formation, and higher expression levels of osteogenic differentiation-related genes (COL 1, RunX2, OCN, and OPN) than cells grown on PAA surface. The P/PAA composites exhibited both superior mechanical properties to the pearl powder, higher bioactivity and osteogenic capability compared with those of PAA.

From the raw bar to the bench: Bivalves as models for human health

Bivalves, from raw oysters to steamed clams, are popular choices among seafood lovers and once limited to the coastal areas. The rapid growth of the aquaculture industry and improvement in the preservation and transport of seafood have enabled them to be readily available anywhere in the world. Over the years, oysters, mussels, scallops, and clams have been the focus of research for improving the production, managing resources, and investigating basic biological and ecological questions. During this decade, an impressive amount of information using high-throughput genomic, transcriptomic and proteomic technologies has been produced in various classes of the Mollusca group, and it is anticipated that basic and applied research will significantly benefit from this resource. One aspect that is also taking momentum is the use of bivalves as a model system for human health. In this review, we highlight some of the aspects of the biology of bivalves that have direct implications in human health including the shell formation, stem cells and cell differentiation, the ability to fight opportunistic and specific pathogens in the absence of adaptive immunity, as source of alternative drugs, mucosal immunity and, microbiome turnover, toxicology, and cancer research. There is still a long way to go; however, the next time you order a dozen oysters at your favorite raw bar, think about a tasty model organism that will not only please your palate but also help unlock multiple aspects of molluscan biology and improve human health.

The effect of nacre extract on cord blood-derived endothelial progenitor cells: A natural stimulus to promote angiogenesis?

Angiogenesis is a critical parameter to consider for the development of tissue-engineered bone substitutes. The challenge is to promote sufficient vascularization in the bone substitute to prevent cell death and to allow its efficient integration. The capacity of nacre extract to restore the osteogenic activity of osteoarthritis osteoblasts has already been demonstrated. However, their angiogenic potential on endothelial progenitor cells (EPCs) was not yet explored. Therefore, the current study aimed at investigating if nacreous molecules affect EPC behavior. The gene and protein expression levels of endothelial cell (EC)-specific markers were determined in EPCs cultivated in presence of a nacre extract (ethanol soluble matrix [ESM] at two concentrations: 100 μg/mL and 200 μg/mL (respectively abbreviated ESM100 and ESM200)). Cell functionality was explored by proangiogenic factors production and in vitro tube formation assay. ESM200 increased the expression of some EC-specific genes. The in vitro tube formation assay demonstrated that ESM200 stimulated tubulogenesis affecting angiogenic parameters. We demonstrated that a stimulation with 200 μg/mL of ESM increased angiogenesis key elements. This in vitro study strongly highlights the proangiogenic effect of ESM. Due to its osteogenic properties, previously demonstrated, ESM could constitute the key element to develop an ideal prevascularized bone substitute. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

In vivo regeneration functionalities of experimental organo-biomaterials containing water-soluble nacre extract

Background

Novel multifunctional biomaterials were recently designed to allow for an optimized tissue regeneration process.

Purpose

To comprehensively assess (photographic, radiographic and histological) the in vivo functionality of demineralized bovine bone matrix (DBM) associated with an experimental marine organic extract (MOE) from nacre in a sheep ectopic grafting model.

Materials and methods

Synthesis of MOE was based on mixing powdered nacre (0.05 g, particles average size <0.1 mm) with acetic acid (5 mL, pH 7) under constant stirring for 72 hours (25 °C). Polyethylene tubes (3/animal, n = 4, diameter: 5.0 mm × length: 10.0 mm) from the control (empty) or experimental groups (DBM or DBM + MOE) were then intramuscularly implanted into the lumbar regions of sheep (n = 8, 2-years old, ≈45 kg). Animals were euthanized at 3 and 6 months to allow for the collection of tissue samples. Tissue samples were fixed in formalin 10% (buffered, 7 days) in preparation for photographic, radiographic and histological assessments. Acquired images were then analyzed using digital image analysis software to quantify the amount of neoformed tissues, whereas radiographic and histological analyses were performed to determine radiopacity and classification of tissues deposited inside of the tubes.

Results

Photographic and radiographic analyses have shown that both pure (unaltered) and MOE-modified DBM were capable of depositing neoformed tissues (at 3 and 6 months), where higher levels of deposition and radiopacity were observed on groups treated with experimental materials. Histological results, however, demonstrated that tissues formed from both unaltered and MOE-modified DBM were only fibrous connective in origin.

Conclusions

As an ectopic grafting in sheep, the experimental organo-biomaterial association applied did not reveal any osteoinductive property but led to a fibrous tissue repair only.

Bone substitute made from a Brazilian oyster shell functions as a fast stimulator for bone-forming cells in an animal model

Despite their demonstrated biocompatibility and osteogenic properties, oyster shells have been reported as a potential alternative to other commonly used materials for bone substitution. This study evaluated whether an experimental bone substitute (EBS) made from a typical oyster shell of Northeastern Brazil (Crassostrea rhizophora) has effects on bone development using an animal model. Oysters were collected from a biologically assisted vivarium, and their inner layer was used for preparing an EBS. Chemical and surface characterization of EBS was performed using Individually Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Scanning Electron Microscope (SEM), respectively. Seventy-two rats were randomly assigned to groups according to the treatment of bone defects created in the submandibular area: Negative Control (-C), Positive Control (+C; Bio-Oss®) and EBS. Euthanasia occurred at 7, 21, 42 and 56 days postoperatively. The bone pieces were stained with hematoxylin and eosin (H&E). The formation of bone tissue was evaluated histologically and histomorphometrically. Data were analyzed through the Kruskal-Wallis test and ANOVA considering a significant level of 5%. The main element found in EBS was calcium (71.68%), and it presented heterogeneity in the particle size and a porosity aspect at SEM analysis. Histological results revealed the absence of inflammatory cells in all groups, being that EBS presented the most accelerated process of bone formation with a statistically significant difference between this group and the +C and -C groups in the 21-day time-point (p < 0.05). After 21 days, the bone formation process was similar between all groups (p > 0.05), showing an immature lamellar bone pattern after 56 days of experimentation (p > 0.05). Within the limitations of this study, it was possible to conclude that EBS presented good biocompatibility and promoted fast stimulation for bone-forming cells in an animal model.