Ascorbic Acid-Assisted Microwave Synthesis of Mesoporous Ag-Doped Hydroxyapatite Nanorods from Biowaste Seashells for Implant Applications

Melatonin-loaded mesoporous zinc- and gallium-doped hydroxyapatite nanoparticles to control infection and bone repair

Effective treatment of infected bone defects resulting from multi-drug resistant bacteria (MDR) has emerged as a significant clinical challenge, highlighting the pressing demand for potent antibacterial bone graft substitutes. Mesoporous nanoparticles have been introduced as a promising class of biomaterials offering significant properties for treating bone infections. Herein, we synthesize antibacterial mesoporous hydroxyapatite substituted with zinc and gallium (Zn-Ga:mHA) nanoparticles using a facile sol-gel method. The resulting mesoporous nanoparticles are applied for the controlled release of melatonin (Mel). Zn-Ga:mHA nanoparticles with an average particle size of 36 ± 3 nm and pore size of 10.6 ± 0.4 nm reveal a Mel loading efficiency of 58 ± 1%. Results show that 50% of Mel is released within 20 h and its long-term release is recorded up to 50 h. The Zn-Ga:mHA nanoparticles exhibit highly effective antibacterial performance as reflected by a 19 ± 1% and 8 ± 2% viability reduction in Escherichia coli and Staphylococcus bacteria, respectively. Noticeably, Mel-loaded Zn-Ga:mHA nanoparticles are also cytocompatible and stimulate in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs) without any osteoinductive factor. In vivo studies in a rabbit skull also show significant regeneration of bone during 14 days. In summary, Mel-loaded Zn-Ga:mHA nanoparticles provide great potential as an antibacterial and osteogenic component in bone substitutes like hydrogels, scaffolds, and coatings.

Silver-doped hydroxyapatite laden chitosan-gelatin nanocomposite scaffolds for bone tissue engineering: an in-vitro and in-ovo evaluation

Despite the advancements in bone tissue engineering, the majority of implant failures are caused due to microbial contamination. So, efforts are being made to develop biomaterial with antimicrobial property enhancing the regeneration of damaged bone tissue. In the present study, chitosan-gelatin (CG) scaffolds containing silver-doped hydroxyapatite (AgHAP) nanoparticles at 0.5%, 1.0% and 1.5% (w/v) were fabricated by lyophilization technique. The results confirmed the synthesis of AgHAP nanoparticles and showed interconnected porous structure of the nanocomposite scaffolds with 89%-75% porosity. Similarly, the swelling percentage, degradation behavior and compressive modulus of CG-AgHAP nanocomposite scaffolds were 1666%, 40% and 0.7 MPa, respectively. The developed nanocomposite scaffolds revealed better antimicrobial properties and bioactivity. The cell culture studies showed favorable viability of Wharton's jelly stem cells on CG-AgHAP nanocomposite scaffolds. CAM (chorioallantoic membrane) assay determined the angiogenic potential with better visualization of blood vessels in the CAM area. Hence, the obtained results confirmed that CG-AgHAP3 nanocomposite scaffold was the most suitable for bone tissue engineering applications among all scaffolds.

Synthesis of Biocompatible Silver-Doped Carbonate Hydroxyapatite Nanoparticles Using Microwave-Assisted Precipitation and In Vitro Studies for the Prevention of Peri-Implantitis

A carbonate-hydroxyapatite-based antibacterial implant material with low cytotoxicity was synthesized. The silver ion (Ag⁺) was incorporated into CHA material, resulting in silver-doped carbonate hydroxyapatite (CHA-Ag). The microwave-assisted precipitation method was used to synthesize the CHA-Ag material. The amount of Ag⁺ was varied at 0.005, 0.010, and 0.015 mol fractions (χAg). The XRD results showed that the diffractograms corresponded with hydroxyapatite (ICSD 98-05-1414), without any additional phase. The presence of carbonate ions was indicated by vibrations at wavenumber of 871, 1411, and 1466 cm^-1 in the infrared spectra. The CHA-Ag materials were agglomerates of nanosized particles with low crystallinity. The particle size and crystallinity of the materials decreased due to the incorporation of CO₃^2- and Ag⁺. The incorporated Ag⁺ successfully inhibited peri-implant-associated bacterial growth. The antibacterial ability increased alongside the increase in the Ag⁺ amount. The pre-osteoblast MC3T3E1 cell could grow up to >70% in the MTT assay, despite the use of Ag⁺ as a dopant. The cell viability was higher in the CHA-Ag-containing media than in the CHA-containing media. The MTT assay also revealed that the CHA-Ag cytotoxicity decreased even though the Ag⁺ amount increased. The CHA-Ag-15 had the lowest cytotoxicity and highest antibacterial activity. Therefore, the optimal amount of Ag⁺ in the CHA-Ag formulation was χAg = 0.015.

Electrospinning Inorganic Nanomaterials to Fabricate Bionanocomposites for Soft and Hard Tissue Repair

Tissue engineering (TE) has attracted the widespread attention of the research community as a method of producing patient-specific tissue constructs for the repair and replacement of injured tissues. To date, different types of scaffold materials have been developed for various tissues and organs. The choice of scaffold material should take into consideration whether the mechanical properties, biodegradability, biocompatibility, and bioresorbability meet the physiological properties of the tissues. Owing to their broad range of physico-chemical properties, inorganic materials can induce a series of biological responses as scaffold fillers, which render them a good alternative to scaffold materials for tissue engineering (TE). While it is of worth to further explore mechanistic insight into the use of inorganic nanomaterials for tissue repair, in this review, we mainly focused on the utilization forms and strategies for fabricating electrospun membranes containing inorganic components based on electrospinning technology. A particular emphasis has been placed on the biological advantages of incorporating inorganic materials along with organic materials as scaffold constituents for tissue repair. As well as widely exploited natural and synthetic polymers, inorganic nanomaterials offer an enticing platform to further modulate the properties of composite scaffolds, which may help further broaden the application prospect of scaffolds for TE.

Drug Molecular Immobilization and Photofunctionalization of Calcium Phosphates for Exploring Theranostic Functions

Theranostics (bifunction of therapeutics and diagnostics) has attracted increasing attention due to its efficiency that can reduce the physical and financial burden on patients. One of the promising materials for theranostics is calcium phosphate (CP) and it is biocompatible and can be functionalized not only with drug molecules but also with rare earth ions to show photoluminescence that is necessary for the diagnostic purpose. Such the CP-based hybrids are formed in vivo by interacting between functional groups of organic molecules and inorganic ions. It is of great importance to elucidate the interaction of CP with the photofunctional species and the drug molecules to clarify the relationship between the existing state and function. Well-designed photofunctional CPs will contribute to biomedical fields as highly-functional ormultifunctional theranostic materials at the nanoscales. In this review, we describe the hybridization between CPs and heterogeneous species, mainly focusing on europium(III) ion and methylene blue molecule as the representative photofunctional species for theranostics applications.

Citric Acid-Mediated Microwave-Hydrothermal Synthesis of Mesoporous F-Doped HAp Nanorods from Bio-Waste for Biocidal Implant Applications

In this current research, mesoporous nano-hydroxyapatite (HAp) and F-doped hydroxyapatite (FHAp) were effectively obtained through a citric acid-enabled microwave hydrothermal approach. Citric acid was used as a chelating and modifying agent for tuning the structure and porosity of the HAp structure. This is the first report to use citric acid as a modifier for producing mesoporous nano HAp and F-doped FHAp. The obtained samples were characterized by different analyses. The XRD data revealed that F is incorporated well into the HAp crystal structure. The crystallinity of HAp samples was improved and the unit cell volume was lowered with fluorine incorporation. Transmission electron microscopy (TEM) images of the obtained samples revealed that a nano rod-like shape was obtained. The mesoporous structures of the produced HAp samples were confirmed by Brunauer–Emmett–Teller (BET) analysis. In vivo studies performed using zebrafish and C. elegans prove the non-toxic behavior of the synthesized F doped HAp samples. The obtained samples are also analyzed for antimicrobial activity using Gram-negative and Gram-positive bacteria, which are majorly involved in implant failure. The F doped samples revealed excellent bactericidal activity. Hence, this study confirms that the non-toxic and excellent antibacterial mesoporous F doped HAp can be a useful candidate for biocidal implant application.

Hydroxyapatite as a bifunctional nanocatalyst for solventless Henry reaction: a demonstration of morphology-dependent catalysis

Hydroxyapatite nanorods are catalytically active while nanoplates are inactive towards Henry reaction due to the differences in the exposed surfaces.

A review on the synthesis and properties of hydroxyapatite for biomedical applications

Hydroxyapatite (HA or HAp) is one of the most preferred biomaterials, specifically for bone tissue engineering. HAp is available naturally and is also chemically synthesized. The properties, shape, size and crystalline structure and applications of HAp vary widely depending on the source and extraction methods used. In addition to conventional chemical approaches such as precipitation or sol-gel techniques, newer methods such as microwave synthesis and atomic-layer deposition provide an opportunity to generate HAp with desirable structure and properties. Various methods used for the synthesis of HAp have their own pros and cons. Hence, it is essential to understand the role of specific methods and conditions on the properties and structure of HAps in order to obtain HAp with properties suitable for specific applications. In addition to pure HAp, substantial efforts have been made to dope HAp with various minerals or bioentities to enhance their suitability for medical, environmental remediation and other approaches. In this review, we provide an overview of the various chemical methods used to produce HAp, properties of the HAp produced and its potential applications. Particular focus of this paper is on the co-relation between properties and processes used to synthesis HAp. This review will enable readers to quickly understand the importance of synthesis methods and conditions on the properties of HAp and choose appropriate means to generate HAp with desired properties for specific applications.

Nano-Hydroxyapatite vs. Xenografts: Synthesis, Characterization, and In Vitro Behavior

This research focused on the synthesis of apatite, starting from a natural biogenic calcium source (egg-shells) and its chemical and morpho-structural characterization in comparison with two commercial xenografts used as a bone substitute in dentistry. The synthesis route for the hydroxyapatite powder was the microwave-assisted hydrothermal technique, starting from annealed egg-shells as the precursor for lime and di-base ammonium phosphate as the phosphate precursor. The powders were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), X-ray fluorescence spectroscopy (XRF), and cytotoxicity assay in contact with amniotic fluid stem cell (AFSC) cultures. Compositional and structural similarities or differences between the powder synthesized from egg-shells (HA1) and the two commercial xenograft powders-Bio-Oss®, totally deproteinized cortical bovine bone, and Gen-Os®, partially deproteinized porcine bone-were revealed. The HA1 specimen presented a single mineral phase as polycrystalline apatite with a high crystallinity (Xc 0.92), a crystallite size of 43.73 nm, preferential growth under the c axes (002) direction, where it mineralizes in bone, a nano-rod particle morphology, and average lengths up to 77.29 nm and diameters up to 21.74 nm. The surface of the HA1 nanoparticles and internal mesopores (mean size of 3.3 ± 1.6 nm), acquired from high-pressure hydrothermal maturation, along with the precursor's nature, could be responsible for the improved biocompatibility, biomolecule adhesion, and osteoconductive abilities in bone substitute applications. The cytotoxicity assay showed a better AFSC cell viability for HA1 powder than the commercial xenografts did, similar oxidative stress to the control sample, and improved results compared with Gen-Os. The presented preliminary biocompatibility results are promising for bone tissue regeneration applications of HA1, and the study will continue with further tests on osteoblast differentiation and mineralization.

Synthesis and characterizations of natural limestone-derived nano-hydroxyapatite (HAp): a comparison study of different metals doped HAps on antibacterial activity

Earth-abundant mineral limestone obtained from North Sumatera, Indonesia, has been utilized to synthesize nano-hydroxyapatite (HAp). Although HAp is biocompatible to the human bone, its antibacterial activity is still very low. Herein, different metal ions (i.e., Ag, Cu, Zn, and Mg) were doped into HAp to improve the antibacterial activity. The as-synthesized HAp was characterized by X-ray ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy disperse spectroscopy (EDS), Fourier transmission infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The antibacterial test showed that the performance of HAp to inactivate bacterial growth was significantly improved after incorporating the metal ion dopants into HAp. Ag-HAp exhibited the highest activity toward E. coli and S. aureus with an antibacterial rate of 99.9 ± 0.1%, followed by Zn-HAp, Cu-HAp, and Mg-HAp.

Antibacterial activities of different metal ion doped HAp towards (a) E. coli and (b) S. aureus bacteria.

Induction of osteogenesis in bone tumour cells by purine-conjugated zinc-hydroxyapatite

This study aimed to improve the biocompatibility and osteogenic property of hydroxyapatite (HAP). So HAP nanoparticles were doped with zinc (Zn), and their surface was modified with a purine nucleotide, guanosine 5′-triphosphate (GTP). GTP-loaded nanoparticles (GTP@ZnHAP) were characterised by field emission scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis, zeta potential and ultraviolet–visible spectroscopy. Biological experiments revealed that GTP@ZnHAP nanoparticles were internalised by the cells, inhibiting tumour cell (osteoblast-like cells, Saos-2) expansion with an efficiency more than that observed for ZnHAP nanoparticles and GTP alone. Furthermore, Saos-2 cells were committed to differentiate into the normal osteoblast cells under the influence of GTP@ZnHAP nanoparticles demonstrated by the quantitative assessment of bone-related protein expression (Runx2 and osteocalcin) and cell morphological changes. Moreover, high-performance liquid chromatography analyses disclosed a significant enhancement of intracellular GTP content in GTP@ZnHAP-treated cells, proposing perturbation of intracellular nucleotide equilibrium during the process of osteogenesis induced by GTP@ZnHAP nanoparticles. Overall, GTP@ZnHAP exhibits a better synergistic effect on the modulation of cell growth and induction of osteogenic differentiation in osteosarcoma cells than ZnHAP nanoparticles and GTP alone do. Therefore, GTP@ZnHAP may be regarded as a promising biomaterial for the treatment of bone-related diseases.

Green synthesis of stable antioxidant, anticancer and photocatalytic activity of zinc oxide nanorods from Leea asiatica leaf

The present work reveals zinc oxide nanorods (ZnO NRs) obtained via green synthesis approach utilizing phytochemicals present in the Leea asiatica plant. The synthesized ZnO NRs was confirmed by various characterization methods like X-ray diffraction, FTIR, SEM-EDX, UV-vis, TEM and Raman spectra analysis. The obtained nanorods show less particle size with a distinctive high surface area. The photodegradation activity of obtained ZnO NRs shows 81.3 % of dye degradation at high concentration whereas 42.9 % in low concentration and also antioxidant test shows a better result for free radical scavenging. To understand the safety of the ZnO NRs zebrafish embryos was utilized as a model and found to be less toxic after assessment. Furthermore, to understand the anticancer activity of ZnO NRs it was assessed against breast cancer cell line through MTT, XTT, NRU, and LDH assay. The ZnO NRs exposed against breast cancer cell line (MCF-7) had resulted in necrosis and apoptosis which was further confirmed by genotoxicity assay. Also, the molecular mechanisms behind the necrosis and apoptosis are also discussed to show the involvement of ZnO NRs towards breast cancer cells (MCF-7). The present study on ZnO NRs gives a wide spectrum understanding of using ZnO NRs as a potential drug for human breast cancer by showing its physiological pathways as well as a novel way to synthesize ZnO NRs using Leea asiatica plant extract.

The preparation of calcium phosphate adsorbent from natural calcium resource and its application for copper ion removal

Using the hen eggshells (biowaste) as a source of calcium and an environmentally friendly approach, the nanopowder composed of 74% of hydroxyapatite (HA) and 26% of β-tricalcium phosphate (β-TCP) was obtained. Due to the maximum reduction of the stages associated with the use of chemicals and energy, this method can be considered as economically and environmentally friendly. A well-developed surface area and the negative zeta potential at pH above 3.5 indicate good adsorption properties of this material. The obtained material shows high adsorption capacity towards Cu²⁺ ions, i.e. 105.4 mg/g at pH 5. Good fit of the Langmuir adsorption model and the pseudo-second-order kinetic model may indicate chemical adsorption probably due to the electrostatic interactions between the Cu²⁺ cations and the negatively charged phosphate and hydroxyl groups on the material surface.

Tailoring Cu substituted hydroxyapatite/functionalized multiwalled carbon nanotube composite coating on 316L SS implant for enhanced corrosion resistance, antibacterial and bioactive properties

The aim of the present work is to study the potential change in the antibacterial properties of Cu-hydroxyapatite/functionalized multiwall carbon nanotube (HA/f-MWCNT) composite coated heterogeneous implant surfaces against Gram positive and Gram-negative microorganism and to reveal the possible contribution of surface corrosion effects arising in stimulated body fluid. Novel spray pyrolysis instrument designed with double nozzle was used for the fabrication of Cu-hydroxyapatite/f-MWCNT film on 316L stainless steel (SS). The Cu-hydroxyapatite/MWCNT coated bioimplant was characterized by a series of techniques to identify the crystallinity, chemical bonds, surface morphology and elemental composition. The results disclose that the coated implants exhibit highly crystalline nature with the space group of P6_3mc and spherical shaped morphology. The corrosion current density revealed a remarkable decrease from 6.8 to 3.8 μA suggesting that the Cu substituted hydroxyapatite/f-MWCNT composite coating provided higher barrier properties which is beneficial to achieve higher corrosion protection of 316L SS implant. The hybrid Cu-hydroxyapatite-MWCNT composite revealed better antibacterial ability than HA/MWCNT for both gram positive and gram-negative bacteria with a maximum inhibition zone of 13-17 mm, compared with hydroxyapatite/f-MWCNT. The antibacterial ability of the Cu-hydroxyapatite/f-MWCNT nanocomposites was effective against Escherichia coli compared with other microorganisms. The Cu-hydroxyapatite/f-MWCNT nanocomposite exhibited that the coated material is nontoxic, biocompatible and suitable for biomedical application.

Upgrading of marine (fish and crustaceans) biowaste for high added-value molecules and bio(nano)-materials

Currently, the Earth is subjected to environmental pressure of unprecedented proportions in the history of mankind. The inexorable growth of the global population and the establishment of large urban areas with increasingly higher expectations regarding the quality of life are issues demanding radically new strategies aimed to change the current model, which is still mostly based on linear economy approaches and fossil resources towards innovative standards, where both energy and daily use products and materials should be of renewable origin and 'made to be made again'. These concepts have inspired the circular economy vision, which redefines growth through the continuous valorisation of waste generated by any production or activity in a virtuous cycle. This not only has a positive impact on the environment, but builds long-term resilience, generating business, new technologies, livelihoods and jobs. In this scenario, among the discards of anthropogenic activities, biodegradable waste represents one of the largest and highly heterogeneous portions, which includes garden and park waste, food processing and kitchen waste from households, restaurants, caterers and retail premises, and food plants, domestic and sewage waste, manure, food waste, and residues from forestry, agriculture and fisheries. Thus, this review specifically aims to survey the processes and technologies for the recovery of fish waste and its sustainable conversion to high added-value molecules and bio(nano)materials.