Synthesis of macro and micro porous hydroxyapatite (HA) structure from waste kina ( Evechinus chloroticus ) shells

Nano-Hydroxyapatite Isolation and Characterisation of Echinometra mathaei from the Persian Gulf

The study focuses on the preparation and characterisation (physicochemical and mechanical) of hydroxyapatite [Ca10(PO4)6(OH)2] (HA) from sea urchin, Echinometra mathaei. Therefore, nano-sized HA prepared from sea urchin shells were collected from beaches of the Persian Gulf in Iran. Sea urchin shells were found a source of calcium carbonate in the form of aragonite (calcite) that crystallised in an organic matrix. HA is one of the polymers used in coating the nanoparticles extracted from various sources. The calcined aragonite converted to nanosized hydroxyapatite powder by chemical reaction with orthophosphoric acid while maintaining stoichiometry, Ca/P = 1.667 at 80°C. To determine the purity of the nano-hydroxyapatite (nHA) numerous analytical procedures were used. Fourier transforms infrared spectroscopy (FTIR) confirmed the presence of the peak of 961 cm-1 is related to the symmetric tensile band of the P-O bond, and the peak of 1038 cm-1 and 1091 cm-1 is related to the tensile solid absorption of the PO4 as functional groups of nHA. The nanocrystalline HA can be observed from the SEM images. Thermogravimetric analysis (TGA-DTA) demonstrates the thermal stability of nHA powder. The results show successful isolation and characterisation study of this crucial nano-material shows it is valuable in biomedical applications, particularly in bone tissue engineering. Indeed, its fabrication is easy and economical.

Hydrothermal Synthesis of Biphasic Calcium Phosphate from Cuttlebone Assisted by the Biosurfactant L-rhamnose Monohydrate for Biomedical Materials

The motivation of this research work is to develop novel medical material from cuttlebone (calcium source) by L-rhamnose monohydrate (biosurfactant) for aged people. The process can be synthesized biphasic calcium phosphate which is eco-friendly to environment. One of the most important aspects for this work is to use cuttlebone as a naturally occurring calcium source from a local beach in Thailand. It usually contains 90% calcium carbonate. The objective of this research work is to synthesize the biphasic calcium phosphate by hydrothermal reaction. Critical micelle concentrations (CMCs) of 10, 20, 100, 500 and 1000 of L-rhamnose monohydrate were used to control particle size and shape. XRD revealed a mixture of β-tricalcium phosphate and hydroxyapatite powder. SEM reported that the size of particles can be effectively controlled by the addition of L-rhamnose monohydrate, and with the addition of surfactant, size uniformity was achieved. The cytotoxicity test was reported to be in the range of 70–75%. It was remarkable to note that biphasic calcium phosphate synthesized from cuttlebone with the aid of L-rhamnose monohydrate will be considered an excellent candidate as a scaffold material.

Hydroxyapatite in Oral Care Products-A Review

Calcium phosphate compounds form the inorganic phases of our mineralised tissues such as bone and teeth, playing an important role in hard tissue engineering and regenerative medicine. In dentistry and oral care products, hydroxyapatite (HA) is a stable and biocompatible calcium phosphate with low solubility being used for various applications such as tooth remineralisation, reduction of tooth sensitivity, oral biofilm control, and tooth whitening. Clinical data on these products is limited with varied results; additionally, the effectiveness of these apatite compounds versus fluoride, which has conventionally been used in toothpaste, has not been established. Therefore, this review critically evaluates current research on HA oral care, and discusses the role and mechanism of HA in remineralisation of both enamel and dentine and for suppressing dentine sensitivity. Furthermore, we position HA’s role in biofilm management and highlight the role of HA in dental applications by summarising the recent achievement and providing an overview of commercialised HA dental products. The review also indicates the existing limitations and provides direction for future research and commercialisation of apatite-based oral care products.

Bone Grafts and Substitutes in Dentistry: A Review of Current Trends and Developments

After tooth loss, bone resorption is irreversible, leaving the area without adequate bone volume for successful implant treatment. Bone grafting is the only solution to reverse dental bone loss and is a well-accepted procedure required in one in every four dental implants. Research and development in materials, design and fabrication technologies have expanded over the years to achieve successful and long-lasting dental implants for tooth substitution. This review will critically present the various dental bone graft and substitute materials that have been used to achieve a successful dental implant. The article also reviews the properties of dental bone grafts and various dental bone substitutes that have been studied or are currently available commercially. The various classifications of bone grafts and substitutes, including natural and synthetic materials, are critically presented, and available commercial products in each category are discussed. Different bone substitute materials, including metals, ceramics, polymers, or their combinations, and their chemical, physical, and biocompatibility properties are explored. Limitations of the available materials are presented, and areas which require further research and development are highlighted. Tissue engineering hybrid constructions with enhanced bone regeneration ability, such as cell-based or growth factor-based bone substitutes, are discussed as an emerging area of development.

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.

Naturally Derived a-Tricalcium Phosphate Based Porous Composite Bead Production

In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 composite beads via using bovine bone-derived hydroxyapatite, cerium oxide, and alumina ceramics. Bovine-bone derived hydroxyapatite was obtained via calcination of bones at 950°C for 3 hours. Hydroxyapatite is a thermally unstable biomaterial at high temperatures, and depending on its stoichiometry decomposes at 800-1200°C. Sodium alginate was successfully used as an in situ gelling templates for the production of the ceramic beads and starch, an environmentally friendly and economic pore-forming agent, is used to achieve interconnected, highly open porosity containing composite beads. Sintering of the ceramic−starch−alginate green composite beads at 1200°C for 1 hour resulted in the decomposition of the hydroxyapatite phase and formation of a-TCP. XRD analysis revealed that a-TCP-CeO2-Al2O3 composite beads were achieved. XRD analysis confirmed the formation of a-TCP phase in all composite compositions. SEM investigations of the produced composite beads revealed that bimodal pore size distribution, fine and coarse, was achieved.

The preparation of hydroxyapatite from unrefined calcite residues and its application for lead removal from aqueous solutions

Calcite originating from waste treatment technologies was utilised for the chemical precipitation of hydroxyapatite (HAP). The physicochemical properties of the as-synthesised-HAP was fully characterised using FT-IR, BET, SEM and TEM, confirming its crystal structure and formation of high purity HAP by XRD. The product was employed for removal of lead from aqueous media at pH 5.0, achieving almost 80% of the adsorption in the first 5 min and a maximum adsorption capacity for Pb²⁺ of 224.4 mg g⁻¹. A contact time of 40 min was required to achieve equilibrium with Pb²⁺ uptake of 98%. The kinetics of the cation exchange of HAP from calcite were predicted using integrated rate laws, revealing a pseudo-second order cation exchange process with a rate constant of 6.84 × 10⁻⁴ g (mg min)⁻¹. All obtained results are benchmarked against a control HAP sample simultaneously derived from eggshells, which were demonstrated to offer slower kinetics of cation exchange (4.82 × 10⁻⁴ g (mg min)⁻¹) and almost half the maximum adsorption capacity (129.1 mg g⁻¹). The results showed that hydroxyapatite synthesised from calcite waste represents a low-cost material for the adsorption of hazardous Pb²⁺ in contaminated waters and a promising alternative for heavy metals remediation in aquatic environments.

HAP is synthesized directly from waste calcite and is demonstrated to sequester lead at a quicker rate than comparable materials.

Naphthoquinones of the spinochrome class: occurrence, isolation, biosynthesis and biomedical applications

Quinones are widespread in nature and have been found in plants, fungi and bacteria, as well as in members of the animal kingdom. More than forty closely related naphthoquinones have been found in echinoderms, mainly in sea urchins but occasionally in brittle stars, sea stars and starfish. This review aims to examine controversial issues on the chemistry, biosynthesis, functions, stability and application aspects of the spinochrome class, a prominent group of secondary metabolites found in sea urchins. The emphasis of this review is on the isolation and structure of these compounds, together with evaluation of their relevant biological activities, source organisms, the location of origin and methods used for isolation and identification. In addition, the studies of their biosynthesis and ecological function, stability and chemical synthesis have been highlighted. This review aims to establish a focus for future spinochrome research and its potential for benefiting human health and well-being.