Extraction of natural hydroxyapatite for biomedical applications—A review

Novel Applications of Natural Biomaterials in Dentistry-Properties, Uses, and Development Perspectives

Natural biomaterials have gained significant attention in modern dentistry due to their biocompatibility, biodegradability, and low immunogenicity. These materials, including alginate, cellulose, chitosan, collagen, and hydroxyapatite, have been widely explored for their applications in stomatology. They play a crucial role in periodontal disease treatment, caries prevention, and implantology, providing an alternative to synthetic materials. Natural polymers such as chitosan and cellulose are utilized in drug delivery systems and tissue regeneration, while hydroxyapatite serves as a bone substitute due to its osteoconductive properties. Collagen-based scaffolds and coatings enhance periodontal and bone tissue regeneration. Additionally, bioengineered and chemically modified biomaterials offer improved mechanical and biological characteristics, expanding their clinical applications. This review aims to provide a comprehensive analysis of the biological properties, advantages, and limitations of selected natural biomaterials in dentistry. It explores their applications in various aspects of stomatology, including periodontal disease prevention and regeneration, dental caries prevention, bone substitutes in implantology, and dental implant coating. Although natural biomaterials exhibit promising properties, further research is necessary to refine their performance, enhance stability, and ensure long-term safety. Advancements in nanotechnology and bioengineering continue to drive the development of innovative natural biomaterials, paving the way for more effective and biocompatible dental therapies.

Antibacterial property of hydroxyapatite extracted from biological sources and doped with Cu2+ and Ag+ by Sol-gels method

Hydroxyapatite is used in dental materials such as fillings, veneers, and implants due to its biocompatibility and similarity to the natural tooth structure. Goat teeth contain a high amount of hydroxyapatite, the primary mineral component of tooth enamel. Hydroxyapatite in goat tooth enamel ranges from 70 to 90%, sheep teeth from 75 to 85%, and cow teeth from 60 to 75% by weight. Sheep and Cow teeth have slightly lower hydroxyapatite content compared to goats, which is due to slight differences in their species. Hydroxyapatite can be modified or combined with other compounds (metals) to become a compound with high antibacterial properties, which have various applications in dentistry and medicine. This study aims to extract HA particles from the teeth of domestic animals (goats, sheep, and cows), especially goats (higher hydroxyapatite) in a shorter period, purer and with a simpler and more economical method and without adding chemical compounds containing Phosphate was compared to other methods and HA extracted from goat teeth ash was doped with copper and silver metal ions (HA-Doped Cu2+-Ag+) and showed high antibacterial properties. The ideal temperature for calcining HA is 1150 °C for 2 h. The physical properties of extracted HA and HA-Doped Cu2+-Ag+ were investigated using X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR). It was observed in SEM that the distribution of diameter and size is different depending on the molar ratio of Cu2+ and Ag+. According to the XRD report, copper metals entered the network and silver metal was placed around the hydroxyapatite. Antibacterial activity was effective using agar and tube diffusion methods. Minimum inhibitory concentration (MIC) and minimum antibacterial concentration (MBC) were determined. HA doped with copper and silver is an effective antibacterial agent. It proves to be the most effective antibacterial agent in biomedical applications and is compatible with all bacterial strains.

Comparative study of bovine and synthetic hydroxyapatite in micro- and nanosized on osteoblasts action and bone growth

Hydroxyapatite (HA) is widely used as a bone graft. However, information on the head-to-head osteoinductivity and in vivo performance of micro- and nanosized natural and synthetic HA is still lacking. Here, we fabricated nanosized bovine HA (nanoBHA) by using a wet ball milling method and compared its in vitro and in vivo performance with microsized BHA, nanosized synthetic HA (nanoHA), and microsized synthetic HA (HA). The results showed that the wet ball milling method successfully reduced the particle size of BHA to 40 nm without changing its natural characteristics. NanoBHA was able to maintain cell viability and induce cell proliferation and calcium deposits. NanoBHA promoted osteogenic differentiation via OPN as a specific regulator, with a 13-fold greater expression level. NanoBHA and HA also activated ERK1/2 indicated corresponding to the proliferation-differentiation and death of cells, respectively. The calvarial bone defect model showed that nanoBHA induced bone growth based on CT images, which is in line with the histological results showing the presence of bone cells and connective tissue at the nanoBHA implantation site. In conclusion, natural HA outperformed synthetic HA. Our findings will attract interest in further research into nanomaterials and their mechanism of action in bone remodeling.

3D scaffold of hydroxyapatite/β tricalcium phosphate from mussel shells: Synthesis, characterization and cytotoxicity

Bone tissue substitutes are increasing in importance. Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) act as a cell matrix and improve its mechanical properties. One of their raw materials is marine-origin by-products.

OBJECTIVES

To synthesize, characterize, and evaluate the cellular cytotoxicity of a 3D biomaterial based on HA and β-TCP from mussel shells.

METHODS

We prepared pellets with 150, 200, and 250 mg and evaluated them through sintering, XRD, FTIR, ICP-OES, Scanning Electron Microscopic (SEM), and immunocytochemical tests. The Alamar Blue method was applied to the Balb-T3T cell line within 72 h to evaluate cytotoxicity.

RESULTS

Our biomaterials presented a smooth surface with slight irregularity and porosities presenting different diameters and morphologies and showed chemical, morphological, and ultrastructural similarity to bone hydroxyapatite, mainly the 150 and 200 mg pellets.

SIGNIFICANCE

We produced promising HA/β-TCP bioceramics with characteristics that allowed cell culture, promoting adhesion, spreading, and proliferation.

Waste-to-resource: Extraction and transformation of aquatic biomaterials for regenerative medicine

The fisheries and aquaculture industry are known for generating substantial waste or by-products, often underutilized, or relegated to low-value purposes. However, this overlooked segment harbors a rich repository of valuable bioactive materials of which have a broad-spectrum of high-value applications. As the blue economy gains momentum and fisheries expand, sustainable exploitation of these aquatic resources is increasingly prioritized. In this review, we present a comprehensive overview of technology-enabled methods for extracting and transforming aquatic waste into valuable biomaterials and their recent advances in regenerative medicine applications, focusing on marine collagen, chitin/chitosan, calcium phosphate and bioactive-peptides. We discuss the inherent bioactive qualities of these "waste-to-resource" aquatic biomaterials and identify opportunities for their use in regenerative medicine to advance healthcare while achieving the Sustainable Development Goals.

Calcination-based direct extraction of hydroxyapatite from bovine bone waste

The main chemical components of waste cow bones are apatite minerals, especially those containing calcium and phosphorus. This study investigated whether this bone could produce extracted hydroxyapatite through calcining at 900° C for different holding times (1-6 h). An average mass loss of 45% occurred in this experiment during the preparation of bone powders, which involved crushing and further calcining at this temperature. The quantitative XRD analysis showed that 99.97 wt.% hydroxyapatite and over 0.3 wt.% calcite were present in the raw and as-calcined bone powders, with trace amounts of CaFe3O5 (calcium ferrite) phases appearing in the calcined product. Depending on the holding calcining times, SEM images of the calcined bovine powders revealed aggregate sizes ranging from 0.5-3 µm and crystallite (grain) sizes ranging from 70 to 340 nm in all calcium-phosphate powder products. Following EDX analysis of all sample surfaces, possible calcium-deficient hydroxyapatite instead of hydroxyapatite formed, as evidenced by the calcined product's Ca/P ratio exceeding 1.67. Additionally, calcining cow bones for 5-6 h at 900° C yielded a high-purity nano-crystalline hydroxyapatite powder precursor in biomedical applications.

Sustainable Polymeric Biomaterials from Alternative Feedstocks

As materials engineered to interact with biological systems for medical purposes, polymeric biomedical materials have revolutionized and are indispensable in modern healthcare. However, aging populations and improving healthcare standards worldwide have resulted in ever-increasing demands for such biomaterials. Currently, many clinically used polymers are derived from nonrenewable petroleum resources, thus spurring the need for exploring alternatives for the next generation of sustainable biomaterials. Other than biomass, this Perspective also spotlights carbon dioxide and postuse plastics as viable resources potentially suitable for biomaterial production. For each alternative feedstock, key recent developments and practical considerations are discussed, including emerging biomaterial applications, possible feedstock sources, and hindrances toward translation and practical adoption. Other than replacements for petroleum-derived polymers, we explore how utilization of these alternatives capitalizes on their intrinsic physiochemical and material properties to achieve their desired therapeutic effects. We hope that this Perspective can stimulate further development in sustainable biomaterials to achieve practical therapeutic benefits as part of a circular materials economy with minimal environmental impact.

Biochemical, toxicological, and microbiological assessment of calcined poultry manure for potential use as bone scaffold material

The biosafety of thermally calcined poultry manure as a hydroxyapatite source for potential use as bone-making material was investigated in this study. In vitro assays were used to determine the sensitivity of the antioxidant properties to the thermal calcination temperature used to process the poultry manure (750, 800, and 850 °C ). The effect of the extract of both calcined poultry manure (local) and analytical grade hydroxyapatite (foreign) at various concentrations of 100%-25 % inclusion at (100 mg/kg) body weight intubation for 21 days on kidney, liver, and serum of animal model used was assessed. The results show that the thermally calcined poultry manure-derived hydroxyapatite generally possessed good antioxidant properties with the poultry manure treated at 750 °C having the most promising antioxidant properties compared to those treated at 800 and 850 °C , and hence a more likely improved anti-toxicity potential. The various blends of the analytical high-grade hydroxyapatite and thermally calcined poultry manure hydroxyapatite samples are safe compared to the normal control rats with regards hepatic function and renal function parameters with the equal blend of analytical high grade and thermally calcined poultry manure-derived hydroxyapatite (1:1) possessing the lowest activity concentrations. In addition, the enzymatic (glutathione peroxidase) and non-enzymatic (reduced glutathione) antioxidant concentrations of the experimental animals administered the varied compositions of the analytical high grade and thermally calcined poultry manure-derived hydroxyapatite, were lower when compared to normal control rats. The microbiological evaluation suggests that the calcined poultry manure inclusion at various concentrations could not pose a negative effect on various pathology in the liver, kidney, and blood.

Electrospun polyvinyl alcohol nanofiber scaffolds incorporated strontium-substituted hydroxyapatite from sand lobster shells: synthesis, characterization, and in vitro biological properties

The paper describes the synthesis of hydroxyapatite (HAp) and strontium-substituted hydroxyapatite (SrHAp) from sand lobster shells by a hydrothermal method. The HAp and SrHAp were incorporated into the polyvinyl alcohol (PVA) nanofiber scaffold through the eletrospinning method. The scaffolds were incorporated with 5wt% of hydroxyapatite (HAp), 5wt%, 10wt%, and 15% of SrHAp. The physicochemical, mechanical, and in vitro biological properties of the scaffold were evaluated. The incorporation of HAp or SrHAp was evidenced by the diffraction patterns and the phosphate functional groups related to HAp. The morphological results showed the decrement of fiber diameter in line with the increased SrHAp concentration. A tensile test was conducted to investigate the mechanical properties of the scaffolds, and the results showed that the scaffolds perform poorly at a higher SrHAp concentration because of exceeding agglomeration levels. The PVA/SrHAp15 performed the best antibacterial activity against E. coli and S. aureus with an inhibition zone of (15.2 ± 0.2) and (14.5 ± 0.8), respectively. The apatite formation was more abundant in PVA/SrHAp10 after immersion in a simulated body fluid (SBF). Cell viability results showed that the scaffold enabled the osteoblast cells to grow and proliferate. The biocompatibility of HAp and SrHAp resulted in the enhancement of cell adhesion. Based on all tests, the PVA/SrHAp 10 scaffold shows a strong candidate for further in vivo studies.

Hydroxyapatite-Based Natural Biopolymer Composite for Tissue Regeneration

Hydroxyapatite (HAp) polymer composites have gained significant attention due to their applications in bone regeneration and tooth implants. This review examines the synthesis, properties, and applications of Hap, highlighting various manufacturing methods, including wet, dry, hydrothermal, and sol-gel processes. The properties of HAp are influenced by precursor materials and are commonly obtained from natural calcium-rich sources like eggshells, seashells, and fish scales. Composite materials, such as cellulose-hydroxyapatite and gelatin-hydroxyapatite, exhibit promising strength and biocompatibility for bone and tissue replacement. Metallic implants and scaffolds enhance stability, including well-known titanium-based and stainless steel-based implants and ceramic body implants. Biopolymers, like chitosan and alginate, combined with Hap, offer chemical stability and strength for tissue engineering. Collagen, fibrin, and gelatin play crucial roles in mimicking natural bone composition. Various synthesis methods like sol-gel, hydrothermal, and solution casting produce HAp crystals, with potential applications in bone repair and regeneration. Additionally, the use of biowaste materials, like eggshells and snails or seashells, not only supports sustainable HAp production but also reduces environmental impact. This review emphasizes the significance of understanding the properties of calcium-phosphate (Ca-P) compounds and processing methods for scaffold generation, highlighting novel characteristics and mechanisms of biomaterials in bone healing. Comparative studies of these methods in specific applications underscore the versatility and potential of HAp composites in biomedical engineering. Overall, HAp composites offer promising solutions for improving patient outcomes in bone replacement and tissue engineering and advancing medical practices.

Synthetic or Natural (Bio-Based) Hydroxyapatite? A Systematic Comparison between Biomimetic Nanostructured Coatings Produced by Ionized Jet Deposition

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue.

3D printing of fish-scale derived hydroxyapatite/chitosan/PCL scaffold for bone tissue engineering

In the field of bone tissue repair, the treatment of bone defects has always posed a significant challenge. In recent years, the advancement of bone tissue engineering and regenerative medicine has sparked great interest in the development of innovative bone grafting materials. In this study, a novel hydroxyapatite (HA) material was successfully prepared and comprehensively characterized. Antimicrobial experiments and biological evaluations were conducted to determine its efficacy. Based on the aforementioned research findings, 3D printing technology was employed to fabricate HA/chitosan (CS)/ polycaprolactone (PCL) scaffolds. The composition of the scaffold materials was confirmed through X-ray diffractometer (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) tests, while the influence of different HA ratios on the scaffold surface morphology was observed. Additionally, antimicrobial experiments demonstrated the favorable antimicrobial activity of the scaffolds containing 30%HA + 5%CS + PCL. Furthermore, the water contact angle measurements confirmed the superhydrophilicity of the scaffolds. Finally, the excellent bioactivity and ability to promote tissue regeneration of the scaffolds were further confirmed by in vitro and in vivo experiments. This study provides new options for future repair and regeneration of bone tissue and clinical applications.

Potential use of a bone tissue engineering scaffold based on electrospun poly (ɛ-caprolactone) - Poly (vinyl alcohol) hybrid nanofibers containing modified cockle shell nanopowder

Today, the construction of scaffolds promoting the differentiation of stem cells is an intelligent innovation that accelerates the differentiation toward the target tissue. The use of calcium and phosphate compounds is capable of elevating the precision and efficiency of the osteogenic differentiation of stem cells. In this research, osteoconductive electrospun poly (ɛ-caprolactone) (PCL) - poly (vinyl alcohol) (PVA) hybrid nanofibrous scaffolds containing modified cockle shell (CS) nanopowder were prepared and investigated. In this regard, the modified CS nanopowder was prepared by grinding and modifying with phosphoric acid, and it was then added to PVA nanofibers at different weight percentages. Based on the SEM images, the optimum content of the modified CS nanopowder was set at 7 wt %, since reaching the threshold of agglomeration restricted this incorporation. In the second step, the PVA-CS7 nanofibrous sample was hybridized with different PCL ratios. Concerning the hydrophilicity and mechanical strength, the sample named PCL50-PVA50-CS7 was ultimately selected as the optimized and suitable candidate scaffold for bone tissue application. The accelerated hydrolytic degradation of the sample was also studied by FTIR and SEM analyses, and the results confirmed that the mineral deposits of CS are available approximately 7 days for mesenchymal stem cells. Moreover, Alizarin red staining illustrated that the presence of CS in the PCL50-PVA50-CS7 hybrid nanofibrous scaffold may potentially lead to an increase in calcium deposits with high precipitates, authenticating the differentiation of stem cells towards osteogenic cells.

Biocompatibility and Osteogenic Activity of Samarium-Doped Hydroxyapatite-Biomimetic Nanoceramics for Bone Regeneration Applications

In this study, we report on the development of hydroxyapatite (HAp) and samarium-doped hydroxyapatite (SmHAp) nanoparticles using a cost-effective method and their biological effects on a bone-derived cell line MC3T3-E1. The physicochemical and biological features of HAp and SmHAp nanoparticles are explored. The X-ray diffraction (XRD) studies revealed that no additional peaks were observed after the integration of samarium (Sm) ions into the HAp structure. Valuable information regarding the molecular structure and morphological features of nanoparticles were obtained by using Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The elemental composition obtained by using energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of the HAp constituent elements, Ca, O, and P, as well as the presence and uniform distribution of Sm3+ ions. Both HAp and SmHAp nanoparticles demonstrated biocompatibility at concentrations below 25 μg/mL and 50 μg/mL, respectively, for up to 72 h of exposure. Cell membrane integrity was preserved following treatment with concentrations up to 100 μg/mL HAp and 400 μg/mL SmHAp, confirming the role of Sm3+ ions in enhancing the cytocompatibility of HAp. Furthermore, our findings reveal a positive, albeit limited, effect of SmHAp nanoparticles on the actin dynamics, osteogenesis, and cell migration compared to HAp nanoparticles. Importantly, the biological results highlight the potential role of Sm3+ ions in maintaining cellular balance by mitigating disruptions in Ca2+ homeostasis induced by HAp nanoparticles. Therefore, our study represents a significant contribution to the safety assessment of both HAp and SmHAp nanoparticles for biomedical applications focused on bone regeneration.

PMMA bone cement with L-arginine/nano fish bone nanocomplex for apatite formation

Bone cement is one of the materials used in orthopaedics that serves various functions, such as binding bone implants, replacing damaged bones and filling spaces within bones. Various materials have been used to synthesize bone cement, and one promising material for further research is fish bone waste-based bone cement. This study investigates the potential of fish bone waste-based bone cement by incorporating nano fish bone (NFB) and L-arginine (L-Arg) protein into polymethyl methacrylate (PMMA) to examine apatite growth. NFB derived from the Salmo salar fish positively influences osteoblast cell proliferation and differentiation, while L-Arg enhances biocompatibility and antibiotic properties. The NFB/L-Arg combination holds promise in accelerating new bone formation and cell growth, both of which are crucial for fracture healing and bone remodelling. Tensile strength tests reveal the superior performance of BC-PMMA-1-NFB/L-Arg (36.11 MPa) compared with commercial PMMA (32 MPa). Immersion tests with simulated body fluid (SBF) solution for 7 days reveal accelerated apatite layer formation, emphasizing the potential benefits of NFB/L-Arg in bone cement applications.

Hydrothermal extraction and physicochemical characterization of biogenic hydroxyapatite nanoparticles from buffalo waste bones for in vivo xenograft in experimental rats

Hydroxyapatite (HA) can be used in odontology and orthopedic grafts to restore damaged bone due to its stable chemical characteristics, composition, and crystal structural affinity for human bone. A three-step hydrothermal method was used for the extraction of biogenic calcined HA from the buffalo waste bones at 700 °C (HA-700) and 1000 °C (HA-1000). Extracts were analyzed by thermogravimetric analysis, differential scanning calorimetry, X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and in vivo examination of HA xenografts for femoral lesions in experimental rats. Crystallinity, purity, and morphology patterns showed that the HA main phase purity was 84.68% for HA-700 and 88.99% for HA-1000. Spherical HA nanoparticles were present for calcined HA-700 samples in the range 57-423 nm. Rats with critical bone lesions of 3 mm in diameter in the left femur treated with calcined HA-700 nanoparticles healed significantly (p < 0.001) faster than rats treated with HA-1000 or negative controls. These findings showed that spherical biogenic HA-700 NPs with a bud-like structure have the potential to stimulate both osteoconduction and bone remodeling, leading to greater bone formation potential in vivo. Thus, the calcined biogenic HA generated from buffalo waste bones may be a practical tool for biomedical applications.

Enhanced Release of Calcium Ions from Hydroxyapatite Nanoparticles with an Increase in Their Specific Surface Area

Synthetic calcium phosphates, e.g., hydroxyapatite (HAP) and tricalcium phosphate (TCP), are the most commonly used bone-graft materials due to their high chemical similarity to the natural hydroxyapatite-the inorganic component of bones. Calcium in the form of a free ion or bound complexes plays a key role in many biological functions, including bone regeneration. This paper explores the possibility of increasing the Ca2+-ion release from HAP nanoparticles (NPs) by reducing their size. Hydroxyapatite nanoparticles were obtained through microwave hydrothermal synthesis. Particles with a specific surface area ranging from 51 m2/g to 240 m2/g and with sizes of 39, 29, 19, 11, 10, and 9 nm were used in the experiment. The structure of the nanomaterial was also studied by means of helium pycnometry, X-ray diffraction (XRD), and transmission-electron microscopy (TEM). The calcium-ion release into phosphate-buffered saline (PBS) was studied. The highest release of Ca2+ ions, i.e., 18 mg/L, was observed in HAP with a specific surface area 240 m2/g and an average nanoparticle size of 9 nm. A significant increase in Ca2+-ion release was also observed with specific surface areas of 183 m2/g and above, and with nanoparticle sizes of 11 nm and below. No substantial size dependence was observed for the larger particle sizes.

Latest Research of Doped Hydroxyapatite for Bone Tissue Engineering

Bone tissue engineering has attracted great interest in the last few years, as the frequency of tissue-damaging or degenerative diseases has increased exponentially. To obtain an ideal treatment solution, researchers have focused on the development of optimum biomaterials to be applied for the enhancement of bioactivity and the regeneration process, which are necessary to support the proper healing process of osseous tissues. In this regard, hydroxyapatite (HA) has been the most widely used material in the biomedical field due to its great biocompatibility and similarity with the native apatite from the human bone. However, HA still presents some deficiencies related to its mechanical properties, which are essential for HA to be applied in load-bearing applications. Bioactivity is another vital property of HA and is necessary to further improve regeneration and antibacterial activity. These drawbacks can be solved by doping the material with trace elements, adapting the properties of the material, and, finally, sustaining bone regeneration without the occurrence of implant failure. Considering these aspects, in this review, we have presented some general information about HA properties, synthesis methods, applications, and the necessity for the addition of doping ions into its structure. Also, we have presented their influence on the properties of HA, as well as the latest applications of doped materials in the biomedical field.

Production of Nano Hydroxyapatite and Mg-Whitlockite from Biowaste-Derived products via Continuous Flow Hydrothermal Synthesis: A Step towards Circular Economy

Biowastes from agriculture, sewage, household wastes, and industries comprise promising resources to produce biomaterials while reducing adverse environmental effects. This study focused on utilising waste-derived materials (i.e., eggshells as a calcium source, struvite as a phosphate source, and CH₃COOH as dissolution media) to produce value-added products (i.e., calcium phosphates (CaPs) derived from biomaterials) using a continuous flow hydrothermal synthesis route. The prepared materials were characterised via XRD, FEG-SEM, EDX, FTIR, and TEM analysis. Magnesium whitlockite (Mg-WH) and hydroxyapatite (HA) were produced by single-phase or biphasic CaPs by reacting struvite with either calcium nitrate tetrahydrate or an eggshell solution at 200 °C and 350 °C. Rhombohedral-shaped Mg-WH (23-720 nm) along with tube (50-290 nm diameter, 20-71 nm thickness) and/or ellipsoidal morphologies of HA (273-522 nm width) were observed at 350 °C using HNO₃ or CH₃COOH to prepare the eggshell and struvite solutions, and NH₄OH was used as the pH buffer. The Ca/P (atomic%) ratios obtained ranged between 1.3 and 1.7, indicating the formation of Mg-WH and HA. This study showed that eggshells and struvite usage, along with CH₃COOH, are promising resources as potential sustainable precursors and dissolution media, respectively, to produce CaPs with varying morphologies.

Antibiotic-loaded hydroxyapatite scaffolds fabricated from Nile tilapia bones for orthopaedics

This work aimed to develop new antibiotic-coated/ antibiotic-loaded hydroxyapatite (HAp) scaffolds for orthopaedic trauma, specifically to treat the infection after fixation of skeletal fracture. The HAp scaffolds were fabricated from the Nile tilapia (Oreochromis niloticus) bones and fully characterized. The HAp scaffolds were coated with 12 formulations of poly (lactic-co-glycolic acid) (PLGA) or poly (lactic acid) (PLA), blended with vancomycin. The vancomycin release, surface morphology, antibacterial properties, and the cytocompatibility of the scaffolds were conducted. The HAp powder contains elements identical to those found in human bones. This HAp powder is suitable as a starting material to build scaffolds. After the scaffold fabrication, The ratio of HAp to β-TCP changed, and the phase transformation of β-TCP to α-TCP was observed. All antibiotic-coated/ antibiotic-loaded HAp scaffolds can release vancomycin into the phosphate-buffered saline (PBS) solution. PLGA-coated scaffolds obtained faster drug release profiles than PLA-coated scaffolds. The low polymer concentration in the coating solutions (20%w/v) gave a faster drug release profile than the high polymer concentration (40%w/v). All groups showed a trace of surface erosion after being submerged in PBS for 14 days. Most of the extracts can inhibit Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA). The extracts not only caused no cytotoxicity to Saos-2 bone cells but also can increase cell growth. This study demonstrates that it is possible to use these antibiotic-coated/ antibiotic-loaded scaffolds in the clinic as an antibiotic bead replacement.

Behavior of Calcium Phosphate-Chitosan-Collagen Composite Coating on AISI 304 for Orthopedic Applications

Calcium phosphate/chitosan/collagen composite coating on AISI 304 stainless steel was investigated. Coatings were realized by galvanic coupling that occurs without an external power supply because it begins with the coupling between two metals with different standard electrochemical potentials. The process consists of the co-deposition of the three components with the calcium phosphate crystals incorporated into the polymeric composite of chitosan and collagen. Physical-chemical characterizations of the samples were executed to evaluate morphology and chemical composition. Morphological analyses have shown that the surface of the stainless steel is covered by the deposit, which has a very rough surface. XRD, Raman, and FTIR characterizations highlighted the presence of both calcium phosphate compounds and polymers. The coatings undergo a profound variation after aging in simulated body fluid, both in terms of composition and structure. The tests, carried out in simulated body fluid to scrutinize the corrosion resistance, have shown the protective behavior of the coating. In particular, the corrosion potential moved toward higher values with respect to uncoated steel, while the corrosion current density decreased. This good behavior was further confirmed by the very low quantification of the metal ions (practically absent) released in simulated body fluid during aging. Cytotoxicity tests using a pre-osteoblasts MC3T3-E1 cell line were also performed that attest the biocompatibility of the coating.