Conversion of bulk seashells to biocompatible hydroxyapatite for bone implants

Synthesis and characterization of hydroxyapatite self-assembled nanocomposites on graphene oxide sheets from seashell waste: A green process for regenerative medicine

Bone transplantation is the second most common transplantation surgery in the world. Therefore, there is an urgent need for artificial bone transplantation to repair bone defects. In bone tissue engineering, hydroxyapatite (HA) plays a major role in bone graft applications. This study deals with a facile method for synthesizing HA hexagonal nanorods from seashells by a solid-state hydrothermal transition process. The synthesized HA nanorods (∼2.29 nm) were reinforced with carbon nanotube and chitosan on graphene oxide sheets with polymeric support by in-situ synthetic approach. Among the synthesized nanocomposites viz., hydroxyapatite-graphene oxide (HA-GO), hydroxyapatite-graphene oxide-chitosan (HA-GO-CS), hydroxyapatite-graphene oxide-chitosan-carbon nanotube-polylactic acid (HA-GO-CS-CNT-PLA). Among them, the HA-GO-CS-CNT-PLA composite exhibits micro and macro porosity (∼200 to 600 μm), higher mechanical strength, (Hardness ∼90.5 ± 1.33 MPa; Tensile strength 25.62 MPa), and maximum cell viability in MG63 osteoblast-like cells (80%). The self-assembled hybrid-nanocomposite of HA-GO-CS-CNT-PLA is a promising material for bone filler application and could efficiently utilize seashell waste through the green process.

Biomimetic Use of Food-Waste Sources of Calcium Carbonate and Phosphate for Sustainable Materials-A Review

Natural and renewable sources of calcium carbonate (CaCO3), also referred to as "biogenic" sources, are being increasingly investigated, as they are generated from a number of waste sources, in particular those from the food industry. The first and obvious application of biogenic calcium carbonate is in the production of cement, where CaCO3 represents the raw material for clinker. Overtime, other more added-value applications have been developed in the filling and modification of the properties of polymer composites, or in the development of biomaterials, where it is possible to transform calcium carbonate into calcium phosphate for the substitution of natural hydroxyapatite. In the majority of cases, the biological structure that is used for obtaining calcium carbonate is reduced to a powder, in which instance the granulometry distribution and the shape of the fragments represent a factor capable of influencing the effect of addition. As a result of this consideration, a number of studies also reflect on the specific characteristics of the different sources of the calcium carbonate obtained, while also referring to the species-dependent biological self-assembly process, which can be defined as a more "biomimetic" approach. In particular, a number of case studies are investigated in more depth, more specifically those involving snail shells, clam shells, mussel shells, oyster shells, eggshells, and cuttlefish bones.

Hydroxyapatite: A journey from biomaterials to advanced functional materials

Hydroxyapatite (HAp), a well-known biomaterial, has witnessed a remarkable evolution over the years, transforming from a simple biocompatible substance to an advanced functional material with a wide range of applications. This abstract provides an overview of the significant advancements in the field of HAp and its journey towards becoming a multifunctional material. Initially recognized for its exceptional biocompatibility and bioactivity, HAp gained prominence in the field of bone tissue engineering and dental applications. Its ability to integrate with surrounding tissues, promote cellular adhesion, and facilitate osseointegration made it an ideal candidate for various biomedical implants and coatings. As the understanding of HAp grew, researchers explored its potential beyond traditional biomaterial applications. With advances in material synthesis and engineering, HAp began to exhibit unique properties that extended its utility to other disciplines. Researchers successfully tailored the composition, morphology, and surface characteristics of HAp, leading to enhanced mechanical strength, controlled drug release capabilities, and improved biodegradability. These modifications enabled the utilization of HAp in drug delivery systems, biosensors, tissue engineering scaffolds, and regenerative medicine applications. Moreover, the exceptional biomineralization properties of HAp allowed for the incorporation of functional ions and molecules during synthesis, leading to the development of bioactive coatings and composites with specific therapeutic functionalities. These functionalized HAp materials have demonstrated promising results in antimicrobial coatings, controlled release systems for growth factors and therapeutic agents, and even as catalysts in chemical reactions. In recent years, HAp nanoparticles and nanostructured materials have emerged as a focal point of research due to their unique physicochemical properties and potential for targeted drug delivery, imaging, and theranostic applications. The ability to manipulate the size, shape, and surface chemistry of HAp at the nanoscale has paved the way for innovative approaches in personalized medicine and regenerative therapies. This abstract highlights the exceptional evolution of HAp, from a traditional biomaterial to an advanced functional material. The exploration of novel synthesis methods, surface modifications, and nanoengineering techniques has expanded the horizon of HAp applications, enabling its integration into diverse fields ranging from biomedicine to catalysis. Additionally, this manuscript discusses the emerging prospects of HAp-based materials in photocatalysis, sensing, and energy storage, showcasing its potential as an advanced functional material beyond the realm of biomedical applications. As research in this field progresses, the future holds tremendous potential for HAp-based materials to revolutionize medical treatments and contribute to the advancement of science and technology.

Preparation and evaluation of stingray skin collagen/oyster osteoinductive composite scaffolds

The regeneration of bone defects is a major challenge for clinical orthopaedics. Herein, we designed and prepared a new type of bioactive material, using stingray skin collagen and oyster shell powder (OSP) as raw materials. A stingray skin collagen/oyster osteoinductive composite scaffold (Col-OSP) was prepared for the first time by genipin cross-linking, pore-forming and freeze-drying methods. These scaffolds were characterized by ATR-FTIR, SEM, compression, swelling, cell proliferation, cell adhesion, alkaline phosphatase activity, alizarin red staining and RT-PCR etc. The Col-OSP scaffold had an interconnected three-dimensional porous structure, and the mechanical properties of the Col-OSP composite scaffold were enhanced compared with Col, combining with the appropriate swelling rate and degradation rate, the scaffold was more in line with the requirements of bone tissue engineering scaffolds. The Col-OSP scaffold was non-toxic, promoted the proliferation, adhesion, and differentiation of MC3T3-E1 cells, and stimulated the osteogenesis-related genes expressions of osteocalcin (OCN), collagen type I (COL-I) and RUNX2 of MC3T3-E1 cells.

Characterization and tribological behaviour of Indian clam seashell-derived hydroxyapatite coating applied on titanium alloy by plasma spray technique

Various hydroxyapatite (HA) powders synthesized at different temperatures are deposited on titanium alloy by using an atmospheric plasma spray process. These different HA powders were synthesized from Indian clam seashells through the hydrothermal technique at varying temperatures from 700 to 1000 °C for a 2 h time duration in our previous study. The synthesized HA powders are spray-dried to obtain agglomerated powders suitable for spraying during the coating application. Crystallite size, Ca/P ratio, and crystallinity of agglomerated HA powders and their respective coatings are estimated by standard methods. The microstructure and phases of the feedstock and coating materials are investigated by using a field-emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD), respectively. Further, the HA coatings are characterized in terms of surface roughness, microhardness, porosity, adhesion strength, and wear resistance through the stylus profilometer, Vickers micro-hardness tester, image analysis technique, scratch tester, and ball-on-disc tribometer, respectively. The average surface roughness (R_a) and porosity of the coating are decreased with an increase in the synthesis temperature. The minimum R_a and porosity obtained for the 1000 °C coating sample suggest a high degree of melting of such powder particles. However, the highest adhesion strength noticed in the case of the 900 °C coating sample is due to the high compatibility of such coating material with Ti-alloy substrate in terms of thermal properties. The 900 °C coating sample has also shown the highest microhardness and wear-resistance properties due to its maximum crystallinity among all the HA coatings.

Rubbing-Assisted Approach for Fabricating Oriented Nanobiomaterials

The highly-oriented structures in biological tissues play an important role in determining the functions of the tissues. In order to artificially fabricate oriented nanostructures similar to biological tissues, it is necessary to understand the oriented mechanism and invent the techniques for controlling the oriented structure of nanobiomaterials. In this review, the oriented structures in biological tissues were reviewed and the techniques for producing highly-oriented nanobiomaterials by imitating the oriented organic/inorganic nanocomposite mechanism of the biological tissues were summarized. In particular, we introduce a fabrication technology for the highly-oriented structure of nanobiomaterials on the surface of a rubbed polyimide film that has physicochemical anisotropy in order to further form the highly-oriented organic/inorganic nanocomposite structures based on interface interaction. This is an effective technology to fabricate one-directional nanobiomaterials by a biomimetic process, indicating the potential for wide application in the biomedical field.

Extraction of natural hydroxyapatite for biomedical applications—A review

Hydroxyapatite has recently played a crucial role in the sustainable development of biomedical applications. Publications related to hydroxyapatite as filler for biopolymers have exhibited an increasing trend due to the expanding research output. Based on the latest publications, the authors reviewed the research trends regarding hydroxyapatite use in biomedical applications. Analysis of the Scopus database using the keywords ‘hydroxyapatite” and “biomedical applications” determined that 1,714 papers were produced between 2012 and 2021. The number of publications related to these keywords more than doubled between 2012 (99) and 2021 (247). The hydrothermal method, solid-state reactions, the sol-gel process, emulsion, micro-emulsion, and mostly chemical precipitation were used to produce synthetic hydroxyapatite. Meanwhile, calcination, alkaline hydrolysis, precipitation, hydrothermal, and a combination of these techniques were used in producing natural hydroxyapatite. Studies in the current literature reveal that shell-based animal sources have been frequently used as hydroxyapatite resources during investigations concerning biomedical applications, while calcination was the extraction method most often applied. Essential trace elements of fish bone, oyster shell, and eggshell were also found in hydroxyapatite powder. Abalone mussel shell and eggshell showed Ca/P ratios closer to the stoichiometric ratio due to the use of effective extraction methods such as manipulating aging time or stirring process parameters. This review should greatly assist by offering scientific insights to support all the recommended future research works, not only that associated with biomedical applications.

Economical and Environmentally Friendly Track of Biowaste Recycling of Scallop Shells to Calcium Lactate

The scallop shell waste (Pectinidae, one of saltwater clams) was used as a raw material (precursor) to prepare calcium lactate (Ca(C₂H₄OHCOO)₂), and the physicochemical properties of scallop-derived calcium lactate were then investigated. The scallop waste was first ground to obtain calcium carbonate (CaCO₃) powder, and the calcium lactate compounds were successfully synthesized by the reactions between shell-derived CaCO₃ and lactic acid (C₂H₄OHCOOH). The short preparation time, high percentage yield, and low-cost production are the preferred manners, and, in this research, it was the reaction of 70 wt % lactic acid and scallop-derived CaCO₃. The thermal decompositions of both CaCO₃ precursor and all prepared calcium lactates resulted in the formation of calcium oxide (CaO), which is widely used as a catalyst for biodiesel production. By comparing with the literature, the results obtained from the characterization instruments (infrared spectrophotometer, X-ray diffractometer, thermogravimetric analyzer, and scanning electron microscope) confirmed the formation and crystal structure of both CaCO₃ and its calcium lactate product. The morphologies of calcium lactate show different sizes depending on the acid concentration used in the reaction process. Consequently, this work reports an easy, uncomplicated, low-cost technique to change the cheap calcium compound product (scallop CaCO₃) derived from shellfish waste to the valuable compound (calcium lactate), which can be used in many industries.

Optimization of hydrothermal synthesis of hydroxyapatite from chicken eggshell waste for effective adsorption of aqueous Pb(II)

Proper disposal of the millions of tons of eggshell waste generated around the world every year is a significant environmental challenge. However, eggshell waste can be converted into new materials that may be useful for a wide range of applications. In this study, four methods, including the conventional subcritical hydrothermal method (CSHM), microwave-assisted subcritical hydrothermal method (MSHM), conventional low-temperature hydrothermal method (CLHM), and ultrasonic-assisted low-temperature hydrothermal method (ULHM) were used to convert eggshell waste into hydroxyapatite (HAP). For each hydrothermal method, increasing the reaction temperature increased production efficiency and improved the degree of crystallinity of HAP. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the preferred eggshell-derived HAP, which was produced by the MSHM at 180 °C in a period of only 1 h. For the MSHM, the HAP yield was 75.3%, the degree of HAP crystallinity was as high as 0.78, and pure, rod-like, nano-sized HAP particles with high specific surface area were produced. For the preferred HAP produced by the MSHM, the adsorption capacity of Pb²⁺and pH were positively related in the range of pH 1-6. Consequently, the HAP produced by the MSHM showed relatively high maximum adsorption (q_m= 505.05 mg/g) of Pb²⁺ in aqueous solution. The adsorption process followed a pseudo-second-order reaction model, and the equilibrium adsorption was well fit by the Langmuir model.

A New Design of Porosity Gradient Ti-6Al-4V Encapsulated Hydroxyapatite Dual Materials Composite Scaffold for Bone Defects

The tibia of New Zealand White rabbits was used as a model of critical bone defects to investigate a new design of composite scaffold for bone defects composed of dual materials. The all-in-one design of a titanium alloy (Ti-6Al-4V) scaffold comprised the structure of a bone plate and gradient porosity cage. Hydroxyapatite (HAp), a biodegradable material, was encapsulated in the center of the scaffold. The gradient pore structure was designed with 70%-65%-60%-55%-50% porosity, since the stresses could be distributed more uniformly when the all-in-one scaffold was placed on the bone contact surface. By covering the center of the scaffold with a low strength of HAp to contact the relatively low strength of bone marrow tissues, the excessive stiffness of the Ti-6Al-4V can be effectively reduced and further diminish the incidence of the stress shielding effect. The simulation results show that the optimized composite scaffold for the 3D model of tibia had a maximum stress value of 27.862 MPa and a maximum strain of 0.065%. The scaffold prepared by selective laser melting was annealed and found that the Young’s coefficient increased from 126.44 GPa to 131.46 GPa, the hardness increased from 3.9 GPa to 4.12 GPa, and the strain decreased from 2.27% to 1.13%. The result demonstrates that the removal of residual stress can lead to a more stable structural strength, which can be used as a reference for the design of future clinical tibial defect repair scaffolds.

Conversion of Bivalve Shells to Monocalcium and Tricalcium Phosphates: An Approach to Recycle Seafood Wastes

The search for sustainable resources remains a subject of global interest and the conversion of the abundantly available bivalve shell wastes to advanced materials is an intriguing method. By grinding, calcium carbonate (CaCO₃) powder was obtained from each shell of bivalves (cockle, mussel, and oyster) as revealed by FTIR and XRD results. Each individual shell powder was reacted with H₃PO₄ and H₂O to prepare Ca(H₂PO₄)₂·H₂O giving an anorthic crystal structure. The calcination of the mixture of each shell powder and its produced Ca(H₂PO₄)₂·H₂O, at 900 °C for 3 h, resulted in rhombohedral crystal β-Ca₃(PO₄)₂ powder. The FTIR and XRD data of the CaCO₃, Ca(H₂PO₄)₂·H₂O, and Ca₃(PO₄)₂ prepared from each shell powder are quite similar, showing no impurities. The thermal behaviors of CaCO₃ and Ca(H₂PO₄)₂·H₂O produced from each shell were slightly different. However, particle sizes and morphologies of the same products obtained from different shells were slightly different-but those are significantly different for the kind of the obtained products. Overall, the products (CaCO₃, Ca(H₂PO₄)₂·H₂O, and Ca₃(PO₄)₂) were obtained from the bivalve shell wastes by a rapidly simple, environmentally benign, and low-cost approach, which shows huge potential in many industries providing both economic and ecological benefits.

Composite Polymer for Hybrid Activity Protective Panel in Microwave Generation of Composite Polytetrafluoroethylene -Rapana Thomasiana

During the microwave sintering of a polymer-ceramic composite plasma discharge is experienced. The discharge could occur failure of the power source. The solution proposed by the paper is original, no similar solutions being presented by the literature. It consists of using a polymer-ceramic composite protective panel, to stop the plasma discharge to the entrance of the guiding tunnel. Six composites resulted by combining three polymers, Polytetrafluoroethylene (PTFE), STRATITEX composite and Polyvinylchloride (PVC) with two natural ceramics containing calcium carbonate: Rapana Thomasiana (RT) sea-shells and beach sand were used to build the protective panel.Theoretical balance of the power to the panel was analysed and the thermal field was determined. It was applied heating using 0.6-1.2-1.8-2.4-3.0 kW microwave beam power. The panels were subjected to heating with and without material to be sintered. It was analyzed: RT chemical (CaCO₃ as Calcite and Aragonite), burned area (range: 200–4000 mm²) and penetration (range: 1.6–5.5 mm), and thermal analysis of the burned areas comparing to the original data. PTFE-RT composite proved the lowest penetration to 0.6 and 1.2 kW. Other 1.2 kW all composites experienced vital failures. Transformation of the polymer matrix of composite consisted of slightly decreasing of the phase shifting temperature and of slightly increasing of the melting start and liquidus temperature.

Direct 3D Printing of Seashell Precursor toward Engineering a Multiphasic Calcium Phosphate Bone Graft

Multiphasic calcium phosphate (Ca-P) has widely been explored for bone graft replacement. This study represents a simple method of developing osteoinductive scaffolds by direct printing of seashell resources. The process demonstrates a coagulation-assisted extrusion-based three-dimensional (3D) printing process for rapid fabrication of multiphasic calcium phosphate-incorporated 3D scaffolds. These scaffolds demonstrated an interconnected open porous architecture with improved compressive strength and higher surface area. Multiphasic calcium phosphate (Ca-P) and hydroxyapatite present in the multi-scalar naturally resourced scaffold displayed differential protein adsorption, thus facilitating cell adhesion, migration, and differentiation, resulting in enhanced deposition of the extracellular matrix. The microstructural and physicochemical attributes of the scaffolds also lead to enhanced stem cell differentiation as witnessed from gene and protein expression analysis. Furthermore, the histological study of subcutaneous implantation evidently portrays promising biocompatibility without foreign body reaction. Neo-tissue in-growth was manifested with abundant blood vessels, thus indicative of excellent vascularization. Notably, cartilaginous and proteoglycan-rich tissue deposition indicated ectopic bone formation via an endochondral ossification pathway. The hierarchical interconnected porous architectural tribology accompanied with multiphasic calcium phosphate composition manifests its successful implication in enhancing stem cell differentiation and promoting excellent tissue in-growth, thus making it a plausible alternative in bone tissue engineering applications.

Speedy bioceramics: Rapid densification of tricalcium phosphate by ultrafast high-temperature sintering

Due to unique osteogenic properties, tricalcium phosphate (TCP) has gained relevance in the field of bone repair. The development of novel and rapid sintering routes is of particular interest since TCP undergoes to high-temperature phase transitions and is widely employed in osteoconductive coatings on thermally-sensitive metal substrates. In the present work, TCP bioceramics was innovatively obtained by Ultrafast High-temperature Sintering (UHS). Ca-deficient hydroxyapatite nano-powder produced by mechanochemical synthesis of mussel shell-derived calcium carbonate was used to prepare the green samples by uniaxial pressing. These were introduced within a graphite felt which was rapidly heated by an electrical current flow, reaching heating rates exceeding 1200 °C min^-1. Dense (> 93%) ceramics were manufactured in less than 3 min using currents between 25 and 30 A. Both β and α-TCP were detected in the sintered components with proportions depending on the applied current. Preliminary tests confirmed that the artifacts do not possess cytotoxic effects and possess mechanical properties similar to conventionally sintered materials. The overall results prove the applicability of UHS to bioceramics paving the way to new rapid processing routes for biomedical components.

Application of Nano-Hydroxyapatite Derived from Oyster Shell in Fabricating Superhydrophobic Sponge for Efficient Oil/Water Separation

The exploration of nonhazardous nanoparticles to fabricate a template-driven superhydrophobic surface is of great ecological importance for oil/water separation in practice. In this work, nano-hydroxyapatite (nano-HAp) with good biocompatibility was easily developed from discarded oyster shells and well incorporated with polydimethylsiloxane (PDMS) to create a superhydrophobic surface on a polyurethane (PU) sponge using a facile solution-immersion method. The obtained nano-HAp coated PU (nano-HAp/PU) sponge exhibited both excellent oil/water selectivity with water contact angles of over 150° and higher absorption capacity for various organic solvents and oils than the original PU sponge, which can be assigned to the nano-HAp coating surface with rough microstructures. Moreover, the superhydrophobic nano-HAp/PU sponge was found to be mechanically stable with no obvious decrease of oil recovery capacity from water in 10 cycles. This work presented that the oyster shell could be a promising alternative to superhydrophobic coatings, which was not only beneficial to oil-containing wastewater treatment, but also favorable for sustainable aquaculture.

Characterization of thermoluminescence kinetic parameters of beta irradiated B doped Ca5(PO4)3OH powder obtained from eggshell

In this study, we have synthesized B doped Ca5(PO4)3OH (HAP) by a sonication chemical method. The thermoluminescence (TL) properties of the family of synthesized samples (B doped Ca5(PO4)3OH (HAP) were investigated using an IRSL-TL 565 nm filter. This gave the highest TL intensity of each phosphor after 2 Gy β-irradiation. Three TL glow peaks of B doped Ca5(PO4)3OH (HAP) are centered at around 84, 208 and 324 °C (with a heating rate of 2 °Cs-1). The trapping parameters such as activation energy (E), order of kinetics (b), frequency factor (s) were calculated by using initial rise (IR), various heating rates (VHR) and computerized glow curve deconvolution (CGCD) method. The response of TL glow curves remained constant within ±5% deviation from the initial value after 9 cycles of reuse; but only at tenth cycle the deviation goes up to 6%.

Emerging marine derived nanohydroxyapatite and their composites for implant and biomedical applications

Implant materials must mimic natural human bones with biocompatibility, osteoconductivity and mechanical stability to successfully replace damaged or disease-affected bones. Synthetic hydroxyapatite was incorporated with bioglass to mimic natural bones for replacing conventional implant materials which has led to certain toxicity issues. Hence, hydroxyapatite (HAp) are recently gaining applicational importance as they are resembling the structure and function of natural bones. Further, nanosized HAp is under extensive research to utilize them as a potential replacement for traditional implants with several exclusive properties. However, chemical synthesis of nano-HAp exhibited toxicity towards normal and healthy cells. Recently, biogenic Hap synthesis from marine and animal sources are introduced as a next generation implant materials, due to their mineral ion and significant porous architecture mediated biocompatibility and bone bonding ability, compared to synthetic HAp. Thus, the purpose of the paper is to give a bird's eye view into the conventional approaches for fabricating nano-HAp, its limitations and the significance of using marine organisms and marine food wastes as a precursor for biogenic nano-Hap production. Moreover, in vivo and in vitro analyses of marine source derived nano-HAp and their potential biomedical applications were also discussed.

Calcium phosphate powders synthesized from CaCO3 and CaO of natural origin using mechanical activation in different media combined with solid-state interaction

The highly pure and crystalline calcium carbonate (CaCO₃) and calcium oxide (CaO) with small amounts of As, Cd, Hg, and Pb were prepared by calcinating shells of a golden apple snail. Solid-state reaction and mechanical activation between the CaCO₃ and CaO from calcined golden apple snail shells and dibasic calcium phosphate dihydrate (CaHPO₄•2H₂O, DCPD) were performed to develop calcium phosphate powders. The effects of the milling media used on the mechanical activation were examined. A solid-state reaction of manually mixed CaCO₃ or CaO with DCPD powders at a temperature of 1100 °C produced mostly β-tricalcium phosphate (β-TCP). Hydroxyapatite (HAp) with a small quantity of β-TCP could be produced from a mixed CaCO₃ + DCPD powder using dry and wet mechanical activations with distilled water, alcohol and acetone and from a mixed CaO + DCPD powder using dry mechanical activation combined with a solid-state reaction at a temperature of 1100 °C. A phase change of milled powders to β-TCP was clearly observed from a wet mechanical activation of CaO + DCPD powder with distilled water or alcohol in a solid-state reaction. The thermal instability of HAp powders from a combined mechanical activation with solid-state reaction of CaCO₃ or CaO and DCPD powders could result from two factors. The first is that the pollution was released from the balls and pot mill materials during the mechanical process. Another factor is a reduced level of calcium in the CaO + DCPD mixed powder due to a reaction between CaO and water or alcohol during mechanical milling.

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.

Mechanical Properties of Glass Ionomer Cements after Incorporation of Marine Derived Porous Cuttlefish Bone Hydroxyapatite

The purpose of this study was to evaluate the effects of the incorporation of hydroxyapatite (HA) derived from cuttlefish bone on the mechanical properties of glass ionomer cements (GIC). Fuji II LC and Fuji IX GP Extra (GC Corporation, Tokyo, Japan) were used in the study. There were four groups (n = 11–18) for each material: a group without the addition of HA particles and three groups modified by incorporation of 2, 5, and 10 wt% HA. The tests were performed on a universal testing machine (Shimadzu, Duisburg, Germany) and descriptive statistics, two-way analysis of variance (ANOVA) for the comparison of three mechanical properties, and one-way ANOVA for the comparison of different concentrations for each material were performed. Regarding the Fuji IX groups, compressive strength (CS) and flexural strength (FS) were highest in the group without HA particles added. The differences in CS between the Fuji IX group without HA particles and the Fuji IX groups with 2 wt% HA and 10 wt% HA were significant. The Fuji II 5 wt% HA group exhibited higher diametral tensile strength (DTS) and CS than other Fuji II groups, but not significantly. The Fuji II group, modified with 10 wt% HA, exhibited significantly higher FS than the Fuji II group without HA particles (p < 0.05). Porous HA incorporated into the Fuji IX groups had a significant impact on mechanical properties only in the Fuji IX 5 wt% HA group. Fuji II groups modified with 10 wt% HA showed the most favorable results with respect to FS.

Preparation and characterization of abalone shells derived biological mesoporous hydroxyapatite microspheres for drug delivery

The rapid growth of the abalone industry has brought a great burden to the environment because of their inedible shells. Aiming at environmental and resource sustainability, porous microspheres of carbonate-substituted hydroxyapatite (HAP) were prepared by a hydrothermal method using abalone shells; then, they were further used as a carrier for doxorubicin (DOX) in a drug delivery system. The porous HAP microspheres were approximately 6 μm in size with a considerable specific surface area and average pore size (128.6659 cm²/g and 9.064 nm, respectively), which ensured excellent drug-handling capacity (95.542%). In addition, the pH responsiveness of the drug release system was favorable for effective in vivo drug release in an acidic tumor microenvironment. Moreover, the drug-loaded microspheres could effectively induce apoptosis of MCF-7 cells but were less cytotoxic to MC3T3-E1 cells. Because of its good biocompatibility, high drug loading capacity and controlled drug release property, the porous microspheres prepared in this experiment have potential application value in drug delivery and tumor therapy; furthermore, they make full use of abalone shells, providing environmental sustainability.

Mini-review of waste shell-derived materials' applications

This mini-review reports curbing waste shells (i.e. seashells, eggshells, snail shells, etc.), environmental health issues and liabilities by using them as material for heterogenous catalysts, blended cement manufacture, concrete aggregate, ceramics and plastics additives, biofilter medium and biomedical applications. The traditional materials used in the manufacture of these products could be relatively cheap; however, there are considerable environmental issues (i.e., ecological damage, disruption of eco-system and air contamination) as well as intense energy consumption associated with the exploitation of depleting natural resources. Waste shells are a renewable and cheap alternative, and will simultaneously decrease manufacturing cost while reducing their burden on the environment. This paper emphasizes environmental sustainability by summarizing articles published on various applications of waste shell-derived biomaterials. The properties of waste shell-derived biomaterials are presented and discussed. The materials' properties suggest they are similar to limestone and their biological-natural origin and the high calcium carbonate content with a trace amount of other mineral elements makes them highly favorable for cement production, heterogenous catalysts and hydroxyapatite manufacture for biomedical and wastewater treatment applications. The purpose of this work is to offer new perspectives and direction for future research on waste shell-derived biomaterials while existing areas of applications demanding scale up are highlighted.

The osteoinductive effect of nano-nacre particles on MC-3T3 E1 preosteoblast through controlled release of water soluble matrix and calciumions

Prostheses and implants have been widely utilized in the orthopedic and dental fields. Nowadays, significant advances have been made in the structural and functional connection between living bone and prostheses, especially in the presence of compromised bone quantity/quality. Despite improvement in the treatment outcomes after augmentation, there are still challenges to meet the clinical demands due to limited materials available. In the current study, we investigated the effects of nano-nacre particles as an alternative material on stimulating bone cell differentiation and formation. Mouse osteoblastic cells (MC3T3-E1) were cultured on nano-nacre/type I collagen composite scaffold (NN-ICS) and type I collagen scaffold (ICS). Generated nano-nacre particles showed controlled release of protein and calcium for a period of 36 days. NN-ICS significantly contributed to the proliferation and differentiation of preosteoblasts compared to ICS controls. Our data showed that nano-nacre particles could serve as a candidate of bone substitution material, which potentially contributed to treatment outcomes in cases with compromised bone quality and/or quality.

Enhanced Osteogenesis by Molybdenum Disulfide Nanosheet Reinforced Hydroxyapatite Nanocomposite Scaffolds

The advances in the arena of biomedical engineering enable us to fabricate novel biomaterials that provide a suitable platform for rapid bone regeneration. Herein, we have investigated the in vitro and in vivo osteogenic differentiation, proliferation, and bone regeneration capability of molybdenum disulfide nanosheets (MoS₂NSs) reinforced HAP nanocomposite scaffolds. The MG-63 cells were incubated with HAP and HAP/MoS₂NSs nanocomposite and followed for various cellular activities. The cells incubated with HAP@2 shows higher cell adhesion, cell proliferation, and alkaline phosphatase activity (ALP) in contrast to HAP. The in vivo and in vitro results of the increased ALP level confirm that HAP@2 promotes osteogenic differentiation. This improved osteogenesis was validated with upregulation of osteogenic marker viz. transcription factor, RUNX-2 (∼34 fold), collagen-1 (∼15 fold), osteopontin (∼11 fold), osteocalcin (∼20 fold), and bone morphogenetic protein-2 (∼12 fold) after 12 week postimplantation in comparison to drilled. The X-ray imaging demonstrates that HAP@2 implants promote rapid osteogenesis and bioresorbability than HAP and drilled. The outcomes of the present study provide a promising tool for the regeneration of bone deformities, without using any external growth factor.

Strontium doped hydroxyapatite from Mercenaria clam shells: Synthesis, mechanical and bioactivity study

Synthesis of strontium-doped hydroxyapatite from Mercenaria clam shells has been carried out by hydrothermal method. The doping of bioceramic, processed from biogenic resources is mostly unexplored. The objective is to understand the effect of strontium (Sr) incorporation on phase stability, sintering behaviour, mechanical properties and cytotoxicity of hydroxyapatite (HAp) derived from clam shells. The different molar concentrations of Sr, varies from 10, 30, 50, 70% of Ca, were substituted into the HAp. The synthesized powders were sintered at 1200 °C in air. The as synthesized powders and sintered specimens were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy. The crystallite size and cell parameters of sintered specimens were analyzed from XRD. The XRD of hydrothermally synthesized powders mostly matched with HAp with slight shifting due to Sr doping. However, some distinct Sr based compounds were also observed where Sr substitution is more that 50% of Ca. The XRD of sintered specimen showed increasing β-tricalcium phosphate (β-TCP) phase with Sr substitution. The sintered density of solid samples gradually increased from 3.04 g/cc to 3.50 g/cc and surface energy decreased with increasing Sr substitution. Similarly, microhardness, fracture toughness and nanohardness of solid samples found to be enhanced with Sr substitution. The elastic modulus gradually increased from 130 to 137 GPa for HAp and Sr substituted HAp (70% of Ca). The in vitro cytotoxicity of sintered specimen against mouse osteoblast cell line showed that all the samples were nontoxic. However cell proliferation found low for the solid samples containing more than 50% Sr substitution.

A Review on the Use of Hydroxyapatite-Carbonaceous Structure Composites in Bone Replacement Materials for Strengthening Purposes

Biomedical materials constitute a vast scientific research field, which is devoted to producing medical devices which aid in enhancing human life. In this field, there is an enormous demand for long-lasting implants and bone substitutes that avoid rejection issues whilst providing favourable bioactivity, osteoconductivity and robust mechanical properties. Hydroxyapatite (HAp)-based biomaterials possess a close chemical resemblance to the mineral phase of bone, which give rise to their excellent biocompatibility, so allowing for them to serve the purpose of a bone-substituting and osteoconductive scaffold. The biodegradability of HAp is low (Ksp ≈ 6.62 × 10-126) as compared to other calcium phosphates materials, however they are known for their ability to develop bone-like apatite coatings on their surface for enhanced bone bonding. Despite its favourable bone regeneration properties, restrictions on the use of pure HAp ceramics in high load-bearing applications exist due to its inherently low mechanical properties (including low strength and fracture toughness, and poor wear resistance). Recent innovations in the field of bio-composites and nanoscience have reignited the investigation of utilising different carbonaceous materials for enhancing the mechanical properties of composites, including HAp-based bio-composites. Researchers have preferred carbonaceous materials with hydroxyapatite due to their inherent biocompatibility and good structural properties. It has been demonstrated that different structures of carbonaceous material can be used to improve the fracture toughness of HAp, as they can easily serve the purpose of being a second phase reinforcement, with the resulting composite still being a biocompatible material. Nanostructured carbonaceous structures, especially those in the form of fibres and sheets, were found to be very effective in increasing the fracture toughness values of HAp. Minor addition of CNTs (3 wt.%) has resulted in a more than 200% increase in fracture toughness of hydroxyapatite-nanorods/CNTs made using spark plasma sintering. This paper presents a current review of the research field of using different carbonaceous materials composited with hydroxyapatite with the intent being to produce high performance biomedically targeted materials.

Synthetic and Marine-Derived Porous Scaffolds for Bone Tissue Engineering

Bone is a vascularized and connective tissue. The cortical bone is the main part responsible for the support and protection of the remaining systems and organs of the body. The trabecular spongy bone serves as the storage of ions and bone marrow. As a dynamic tissue, bone is in a constant remodelling process to adapt to the mechanical demands and to repair small lesions that may occur. Nevertheless, due to the increased incidence of bone disorders, the need for bone grafts has been growing over the past decades and the development of an ideal bone graft with optimal properties remains a clinical challenge. This review addresses the bone properties (morphology, composition, and their repair and regeneration capacity) and puts the focus on the potential strategies for developing bone repair and regeneration materials. It describes the requirements for designing a suitable scaffold material, types of materials (polymers, ceramics, and composites), and techniques to obtain the porous structures (additive manufacturing techniques like robocasting or derived from marine skeletons) for bone tissue engineering applications. Overall, the main objective of this review is to gather the knowledge on the materials and methods used for the production of scaffolds for bone tissue engineering and to highlight the potential of natural porous structures such as marine skeletons as promising alternative bone graft substitute materials without any further mineralogical changes, or after partial or total transformation into calcium phosphate.

Osteoblast Cell Response to Naturally Derived Calcium Phosphate-Based Materials

The demand of calcium phosphate bioceramics for biomedical applications is constantly increasing. Efficient and cost-effective production can be achieved using naturally derived materials. In this work, calcium phosphate powders, obtained from dolomitic marble and Mytilus galloprovincialis seashells by a previously reported and improved Rathje method were used to fabricate microporous pellets through cold isostatic pressing followed by sintering at 1200 &deg;C. The interaction of the developed materials with MC3T3-E1 pre-osteoblasts was explored in terms of cell adhesion, morphology, viability, proliferation, and differentiation to evaluate their potential for bone regeneration. Results showed appropriate cell adhesion and high viability without distinguishable differences in the morphological features. Likewise, the pre-osteoblast proliferation overtime on both naturally derived calcium phosphate materials showed a statistically significant increase comparable to that of commercial hydroxyapatite, used as reference material. Furthermore, evaluation of the intracellular alkaline phosphatase activity and collagen synthesis and deposition, used as markers of the osteogenic ability of these bioceramics, revealed that all samples promoted pre-osteoblast differentiation. However, a seashell-derived ceramic demonstrated a higher efficacy in inducing cell differentiation, almost equivalent to that of the commercial hydroxyapatite. Therefore, data obtained demonstrate that this naturally sourced calcium-phosphate material holds promise for applications in bone tissue regeneration.

Natural calcium phosphates from fish bones and their potential biomedical applications

The treatment and recovery of bio-wastes have raised considerable attention both from the environmental and economic point of view. Every year, a remarkable amount of fish processing by-products are generated and dumped as waste from all over the world. Fish bones can serve as a raw material for the production of high value-added compounds that can be used in various sectors including agrochemical, biomedical, food and pharmaceutical industries. The calcination of fish bones results in a single phase (hydroxyapatite) or bi-phasic (hydroxyapatite-tricalcium phosphate) bioceramics depending on the processing conditions as well as the content of the fish bones. This review summarizes the literature on the production of hydroxyapatite from fish bones and discusses their potential applications in biomedical field. The effect of processing conditions on the properties of final products including Ca/P ratio, crystal structure, particle shape, particle size and biological properties are presented in the light of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric-differential thermal analysis, bioactivity and biocompatibility investigations.

Recent progress on fabrication and drug delivery applications of nanostructured hydroxyapatite

Through this brief review, we provide a comprehensive historical background of the development of nanostructured hydroxyapatite (nHAp), and its application potentials for controlled drug delivery, drug conjugation, and other biomedical treatments. Aspects associated with efficient utilization of hydroxyapatite (HAp) nanostructures such as their synthesis, interaction with drug molecules, and other concerns, which need to be resolved before they could be used as a potential drug carrier in body system, are discussed. This review focuses on the evolution of perceptions, practices, and accomplishments in providing improved delivery systems for drugs until date. The pioneering developments that have presaged today's fascinating state of the art drug delivery systems based on HAp and HAp-based composite nanostructures are also discussed. Special emphasis has been given to describe the application and effectiveness of modified HAp as drug carrier agent for different diseases such as bone-related disorders, carriers for antibiotics, anti-inflammatory, carcinogenic drugs, medical imaging, and protein delivery agents. As only a very few published works made comprehensive evaluation of HAp nanostructures for drug delivery applications, we try to cover the three major areas: concepts, practices and achievements, and applications, which have been consolidated and patented for their practical usage. The review covers a broad spectrum of nHAp and HAp modified inorganic drug carriers, emphasizing some of their specific aspects those needed to be considered for future drug delivery applications. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Nanotechnology Approaches to Biology > Cells at the Nanoscale.

Bioactivity and mineralization of natural hydroxyapatite from cuttlefish bone and Bioglass® co-sintered bioceramics

In this study, bioactive hydroxyapatite (HAP)-based bioceramics starting from cuttlefish bone powders have been prepared and characterized. In particular, fragmented cuttlefish bone was co-sintered with 30 wt% of Bioglass^® -45S5 to synthesize HAP-based powders with enhanced mechanical properties and bioactivity. Commercial synthetic HAP was treated following the same procedure and used as a reference. The structure and composition of the bioceramics formulations were characterized using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. After the thermal treatment of cuttlefish bone powder added with 30 wt% Bioglass, new phases with compositions of sodium calcium phosphate [Na₃ Ca₆ (PO₄ )₅ ], β-tricalcium phosphate [Ca₃ (PO₄ )] and amorphous silica were detected. In vitro cell culture studies were performed by evaluating proliferation, metabolic activity and differentiation of human osteoblast-like cells (MG63). Scaffolds made with cuttlefish bone powder exhibited increased apatite deposition, alkaline phosphatase activity and cell proliferation compared with commercial synthetic HAP. In addition, the ceramic compositions obtained after the combination with Bioglass^® further enhanced the metabolic activity of MG63 cell and promoted the formation of a well-developed apatite layer after 7 days of incubation in Dulbecco's modified Eagle's medium.

Hydroxyapatite-polymer biocomposites for bone regeneration: A review of current trends

Bone tissue engineering has emerged as one of the most indispensable approaches to address bone trauma in the past few decades. This approach offers an efficient and a risk-free alternative to autografts and allografts by employing a combination of biomaterials and cells to promote bone regeneration. Hydroxyapatite (HA) is a ceramic biomaterial that mimics the mineral composition of bones and teeth in vertebrates. HA, commonly produced via several synthetic routes over the years has been found to exhibit good bioactivity, biocompatibility, and osteoconductivity under both in vitro and in vivo conditions. However, the brittle nature of HA restricts its usage for load bearing applications. To address this problem, HA has been used in combination with several polymers in the form of biocomposite implants to primarily improve its mechanical properties and also enhance the implants' overall performance by simultaneously exploiting the positive effects of both HA and the polymer involved in making the biocomposite. This review article summarizes the past and recent developments in the evolution of HA-polymer biocomposite implants as an "ideal" biomaterial scaffold for bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2046-2057, 2018.

Design strategies and applications of nacre-based biomaterials

The field of tissue engineering and regenerative medicine relies heavily on materials capable of implantation without significant foreign body reactions and with the ability to promote tissue differentiation and regeneration. The field of bone tissue engineering in particular requires materials capable of providing enhanced mechanical properties and promoting osteogenic cell lineage commitment. While bone repair has long relied almost exclusively on inorganic, calcium phosphate ceramics such as hydroxyapatite and their composites or on non-degradable metals, the organically derived shell and pearl nacre generated by mollusks has emerged as a promising alternative. Nacre is a naturally occurring composite material composed of inorganic, calcium carbonate plates connected by a framework of organic molecules. Similar to mammalian bone, the highly organized microstructure of nacre endows the composite with superior mechanical properties while the organic phase contributes to significant bioactivity. Studies, both in vitro and in vivo, have demonstrated nacre's biocompatibility, biodegradability, and osteogenic potential, which are superior to pure inorganic minerals such as hydroxyapatite or non-degradable metals. Nacre can be used directly as a bulk implant or as part of a composite material when combined with polymers or other ceramics. While nacre has demonstrated its effectiveness in multiple cell culture and animal models, it remains a relatively underexplored biomaterial. This review introduces the formation, structure, and characteristics of nacre, and discusses the present and future uses of this biologically-derived material as a novel biomaterial for orthopedic and other tissue engineering applications.

STATEMENT OF SIGNIFICANCE

Mussel derived nacre, a biological composite composed of mineralized calcium carbonate platelets and interplatelet protein components, has recently gained interest as a potential alternative ceramic material in orthopedic biomaterials, combining the integration and mechanical capabilities of calcium phosphates with increased bioactivity derived from proteins and biomolecules; however, there is limited awareness of this material's potential. Herein, we present, to our knowledge, the first comprehensive review of nacre as a biomaterial. Nacre is a highly promising yet overlooked biomaterial for orthopedic tissue engineering with great potential in a wide variety of material systems. It is our hope that publication of this article will lead to increased community awareness of the potential of nacre as a versatile, bioactive ceramic capable of improving bone tissue regeneration and will elicit increased research effort and innovation utilizing nacre.

Physical versus Biological Control in Bivalve Calcite Prisms: Comparison of Euheterodonts and Pteriomorphs

Multiple groups of bivalve molluscs produce calcitic shell layers, many of these broadly classified as "prismatic." Various pteriomorphian bivalves (such as oysters, pterioids, and mussels) secrete prismatic microstructures with high organic content and clear, strong biological control. However, we present the results of a detailed analysis by scanning electron microscopy (SEM), thermogravimetric analysis, and electron backscatter diffraction to characterize the calcitic prisms in two different clades within the euheterodont bivalves: the extant Chama arcana and the extinct rudists. These results show that the form of prisms constructed is both closely similar between the two taxa and significantly different from those of the pteriomorph bivalves. Most notably, C. arcana and the extinct rudists lack the clear organic outer envelopes and uniform polygonal, cross-sectional appearance. Instead, they form interdigitating crystals of very varied diameters, with some crystals encapsulating others. We advocate retaining the term "fibrillar prisms" to classify these euheterodont microstructures. These fibrillar prisms are more closely similar to abiotic speleothem deposits than to the calcitic prisms of pteriomorph bivalves. We argue that calcite prism growth in euheterodonts is dominated by abiotic constraints whereas, in pteriomorphs (such as oysters, pterioids, and mussels), it is under strong biological control.

Characterization of mesoporous calcium phosphates from calcareous marine sediments containing Si, Sr and Zn for bone tissue engineering

Calcium phosphates (CAPs) can be produced from either biologically sourced materials or mineral deposits. The raw materials impart unique properties to the CAPs due to innate trace amounts of elements that affect the crystal structure, morphology and stoichiometry. Using calcium carbonate (CaCO₃) precursors derived from fossilized calcareous marine sediments (FCMSs), we have synthesized a novel class of CAP biomaterials, termed fm-CaPs, with defined Ca/P molar ratios of 1.4 and 1.7 using a wet synthesis method. Compared with commercially available CAP biomaterials, such as hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP), fm-CaP1.7 had a biphasic composition consisting of an HA phase (in a hexagonal system) and a β-TCP phase (in a rhombohedral crystalline system), which is desirable for the current design of bone substitutes, whereas fm-CaP1.4 consisted of an HA phase and a beta-dicalcium pyrophosphate phase (in a tetragonal system). These bioceramics exhibited a fringe structure of regular crystallographic orientation with well-ordered mesoporous channels. The FCMS raw material imparted trace amounts of silicon (Si), strontium (Sr) and zinc (Zn) to fm-CaPs; these are elements that are important for bone formation. The cyto-compatibility of these biomaterials and their effects on cellular activity were evaluated using osteoblast cells. Cell proliferation assays revealed no signs of cytotoxicity, whereas cells growth was equal to or better than HA and β-TCP controls. The SEM analysis of the cell and material interactions showed good cell spreading on the fm-CaP materials that was comparable to β-TCP and in vitro assays suggested robust osteogenic differentiation, as seen by increased mineralization (alizarin red) and upregulation of osteogenic gene expression. Our results indicate that fm-CaP1.7, in particular, has chemical, physical and morphological properties that make this material suitable for applications that promote bone tissue regeneration.

Electrical impedance spectroscopy - a potential method for the study and monitoring of a bone critical-size defect healing process treated with bone tissue engineering and regenerative medicine approaches

The development of strategies of bone tissue engineering and regenerative medicine has been drawing considerable attention to treat bone critical-size defects (CSDs). Notably, new strategies and/or treatment approaches always require appropriate tools to track the healing process so as to evaluate their success. In this paper, we present the development of a novel approach for the non-invasive, yet real-time, monitoring and assessment of bone CSDs treated with biomaterials and biomedical approaches. For this, we employed the technique of electrical impedance spectroscopy (EIS) to quantitatively monitor and assess the changes in electrical impedance, and thus the regeneration process. In our in vitro tests, we examined the biochemical changes of the fracture area and investigated the influence of collagen and hydroxyapatite on the changes in electrical impedance by EIS, thus inferring the changes in bone regeneration and structure. Based on this success, we further demonstrated, in real time, the process of regeneration of the traumatic area in an in vivo rabbit model. Our electrical-impedance data of the experiment groups, i.e., the ones treated with natural coral and bone morphogenetic protein-2 (BMP-2), revealed that each group has its unique impedance graph characteristics, which are directly associated with the degree of regeneration. For comparison, we also employed radiography, gross anatomy, and histological analyses in examination. Our results illustrate that EIS holds considerable potential as a non-invasive tool for monitoring, in real time, the healing of bone CSDs by allowing for quantitatively characterizing the changes of both hydroxyapatite and collagen.

Mesenchymal stem cell (MSC) viability on PVA and PCL polymer coated hydroxyapatite scaffolds derived from cuttlefish

In the present study, cuttlefish bones are used to prepare highly porous hydroxyapatite (HA) scaffolds via hydrothermal treatment at 200 °C.

Biomineralization on single crystalline rutile: the modulated growth of hydroxyapatite by fibronectin in a simulated body fluid

The aim of this study is to probe the complex interaction between surface bioactivity and protein adsorption on single crystalline rutile.