Advances of Hydroxyapatite Hybrid Organic Composite Used as Drug or Protein Carriers for Biomedical Applications: A Review

Fabrication and characterization of 3D-printed polymeric-based scaffold coated with bioceramic and naringin for a potential use in dental pulp regeneration (in vitro study)

AIM

3D-printed scaffolds loaded with healing directed agents could be employed for better treatment outcome in regenerative dentistry. The aim of this study was to fabricate and characterize simple 3D-printed poly lactic acid (PLA) scaffolds coated with nanoHydroxyapatite (nHA), Naringin (NAR), or their combination, and testing their morphological, chemical, mechanical, antibacterial, biocompatible and bioactive properties.

METHODOLOGY

Two variants pore sizes, 300 and 700 μm, of 3D-printed PLA disc scaffolds measuring (10 × 1 mm) were fabricated. These scaffolds were dip-coated with nHA, NAR, or both (nHA/NAR). Field emission scanning electron microscopy (FeSEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared (FTIR), compressive and flexural strength testing was employed for optimizing pore size. Then, antibacterial activity against isolated Streptococcus mutans and Enterococcus faecalis, and cytotoxicity against normal human fibroblast were assessed. Additionally, appetite formation on scaffold surfaces was assessed after storage in simulated body fluid (SBF) for 14 days by further using FeSEM, EDX and XRD.

RESULTS

FeSEM showed uniform structure for 3D-printed scaffolds in both pore size designs, and a consistent surface coating with nHA and NAR, which were further confirmed by EDX and FTIR. However, mechanical testing revealed statistical significant higher compressive and flexural strengths (p < .000) for 300 μm pore size scaffolds. Statistical significant antibacterial activities (p < .05) were also found with PLA/NAR, and PLA/nHA /NAR scaffolds in comparison with neat. The MTT assay revealed biocompatibility of PLA, nHA and NAR, with the combinations of the latter two working synergistically. Lastly, the formation of a calcium-phosphate appetite layer was recognized on the surface of PLA/nHA, PLA/nHA/NAR scaffold after being stored in SBF.

CONCLUSIONS

3D-printed, 300 μm pore size, PLA scaffold coated with a combination of nHA and NAR showed the best surface characteristics and improved mechanical, antibacterial and biocompatible properties for further investigation in regenerative studies.

Advances of Hydroxyapatite Nanoparticles in Dental Implant Applications

Hydroxyapatite nanoparticles (HANPs) are becoming increasingly crucial in dental implant applications as they are highly compatible with biological systems, actively support biological processes, and closely resemble bone minerals. This review covers the latest progress in how HANPs are made, studied, and used in dentistry. It looks at critical methods for creating HANPs, such as sol-gel, microwave hydrothermal synthesis, and biomimetic approaches, and how they affect the particles' size, structure, and activity. The green synthesis method illustrated a new door to synthesize HAp for maintaining biocompatibilityand increasing antibacterial properties. The review also explores how HANPs improve the integration of implants with bone, support bone growth, and help treat sensitive teeth based on various laboratory and clinical studies. The usage of HAp in dentin and enamel shows higher potentiality through FTIR, XPS, XRD, EDS, etc., for mechanical stability and biological balance compared to natural teeth. Additionally, the use of HANPs in dental products like toothpaste and mouthwash is discussed, highlighting its potential to help rebuild tooth enamel and fight bacteria. There are some challenges for long-term usage against oral bacteria, but doping with inorganic materials, like Zn, has already solved this periodontal problem. Much more research is still essential to estimate the fabrication variation based on patient problems and characteristics. Still, it has favorable outcomes regarding its bioactive nature and antimicrobial properties. Due to their compatibility with biological tissues and ability to support bone growth, HANPs hold great promise for advancing dental materials and implant technology, potentially leading to better dental care and patient outcomes.

Synthesis and characterization of cellulose fibers modified zinc phosphate/hydroxyapatite core-shell as enhanced carrier of cisplatin: Loading, release, and cytotoxicity

The uncontrolled administration of the cisplatin drug (CPTN) resulted in numerous drawbacks. Therefore, effective, affordable, and biocompatible delivery systems were suggested to regulate the loading, release, and therapeutic effect of CPTN. Zinc phosphate/hydroxyapatite hybrid form (ZP/HP) and core-shell nano-rod morphology, as well as its functionalized derivative with cellulose (CF@ZP/HP), were synthesized by the facile dissolution precipitation method followed by mixing with cellulose fibers, respectively. The developed CF@ZP/HP displayed remarkable enhanced CPTN loading properties (418.2 mg/g) as compared to ZP/HP (259.8 mg/g). The CPTN loading behaviors into CF@ZP/HP follow the Langmuir isotherm properties (R2 > 0.98) in addition to the kinetic activities of the pseudo-first-order model (R2 > 0.96). The steric assessment validates the notable increase in the existing loading receptors after the functionalization of ZP/HP with CF from 57.7 mg/g (ZP/HP) to 90.5 mg/g. The functionalization also impacted the capacity of each existing receptor to be able to ensure 5 CPTN molecules. This, in addition to the loading energies (<40 kJ/mol), donates the loading of CPTN by physical multi-molecular processes and in vertical orientation. The CPTN releasing patterns of CF@ZP/HP exhibit slow and controlled properties (95.7 % after 200 h at pH 7.4 and 100 % after 120 h at pH 5.5), but faster than the properties of ZP/HP. The kinetic modeling of the release activities together with the diffusion exponent (>0.45) reflected the release of CPTN according to both erosion and diffusion mechanisms. The loading of CPTN into both ZP/HP and CF@ZP/HP also resulted in a marked enhancement in the anticancer activity of CPTN against human cervical epithelial malignancies (HeLa) (cell viability = 5.6 % (CPTN), 3.2 % (CPTN loaded ZP/HP), and 1.12 % (CPTN loaded CF@ZP/HP)).

Insight into the integration effect of chitosan and β-cyclodextrin on the properties of zinc-phosphate/hydroxyapatite hybrid as delivery structures for 5-fluorouracil: loading and release profiles

Zinc-phosphate/hydroxyapatite hybrid form (ZP/HP) in core-shell nanostructure was developed and functionalized with both chitosan (CS@ZP/HP) and β-cyclodextrin (CD@ZP/HP) as bio-composite of enhanced physicochemical and biological properties. These structures were assessed as potential deliveries of 5-fluorouracil, exhibiting enhanced loading, release, and anti-cancer behaviors. The functionalization strongly prompted the loading effectiveness to be 301.3 mg/g (CS@ZP/HP) and 342.8 mg/g (CD@ZP/HP) instead of 238.9 mg/g for ZP/HP. The loading activities were assessed based on the hypotheses of traditional kinetic and isotherm models, alongside the computational variables of the monolayer model with a single energetic site as an advanced isotherm model. The functionalized versions exhibit much greater loading efficacy compared to ZP/HP as a result of the increment in the density of the existing loading sites [Nm(5-Fu) = 78.85 mg/g (ZP/HP), 93.87 mg/g (CS@ZP/HP), and 117.8 mg/g (CD@ZP/HP)]. Furthermore, the loading energies of approximately 40 kJ/mol, together with the loading potential of each receptor (n > 1) and Gaussian energies of approximately 8 kJ/mol, indicate the physical entrapment of 5-Fu molecules according to a vertical orientation. The materials mentioned verify long-term and continuous release characteristics. Following the modification processes, this behavior became faster as both CS@ZP/HP and CD@ZP/HP displayed complete release within 120 h at pH 1.2. The kinetic studies and diffusing exponent (>0.45) indicate that release characteristics are controlled by both diffusion and erosion processes. These carriers also markedly increase the cytotoxicity of 5-Fu against HCT-116 colorectal cancer cell lines: 5-Fu-ZP/HP (3.2% cell viability), 5-Fu-CS@ZP/HP (1.12% cell viability), and 5-Fu-CD@ZP/HP (0.63% cell viability).

Nano-ZnO-modified hydroxyapatite whiskers with enhanced osteoinductivity for bone defect repair

Hydroxyapatite (HA) whisker (HAw) represents a distinct form of HA characterized by its high aspect ratio, offering significant potential for enhancing the mechanical properties of bone tissue engineering scaffolds. However, the limited osteoinductivity of HAw hampers its widespread application. In this investigation, we observed HAw-punctured osteoblast membranes and infiltrated the cell body, resulting in mechanical damage to cells that adversely impacted osteoblast proliferation and differentiation. To address this challenge, we developed nano-zinc oxide particle-modified HAw (nano-ZnO/HAw). Acting as a reinforcing and toughening agent, nano-ZnO/HAw augmented the compressive strength and ductility of the matrix materials. At the same time, the surface modification with nano-ZnO particles improved osteoblast differentiation by reducing the mechanical damage from HAw to cells and releasing zinc ion, the two aspects collectively promoted the osteoinductivity of HAw. Encouragingly, the osteoinductive potential of 5% nano-ZnO/HAw and 10% nano-ZnO/HAw was validated in relevant rat models, demonstrating the efficacy of this approach in promoting new bone formation in vivo. Our findings underscore the role of nano-ZnO particle surface modification in enhancing the osteoinductivity of HAw from a physical standpoint, offering valuable insights into the development of bone substitutes with favorable osteoinductive properties while simultaneously bolstering matrix material strength and toughness.

Steric and energetic studies on the influence of cellulose on the adsorption effectiveness of Mg trapped hydroxyapatite for enhanced remediation of chlorpyrifos and omethoate pesticides

Magnesium-trapped hydroxyapatite (Mg.HP) was hybridized with cellulose fiber to produce a bio-composite (CLF/HP) with enhanced adsorption affinities for two types of toxic pesticides (chlorpyrifos (CF) and omethoate (OM)). The enhancement influence of the hybridized cellulose on the adsorption performances of Mg.HP was illustrated based on the determined steric and energetic factors. The computed CF and OM adsorption performances of CLF/HP during the saturation phases are 279.8 mg/g and 317.9 mg/g, respectively, which are significantly higher than the determined values using Mg/HP (143.4 mg/g (CF) and 145.3 mg/g (OM)). The steric analysis demonstrates a strong impact of the hybridization process on the reactivity of the surface of the composite. While CLF/HP reflects effective uptake site densities (Nm) of 93.3 mg/g (CF) and 135.3 mg/g (OM), the estimated values for Mg.HP are 51.2 mg/g (CF) and 46.11 mg/g (OM), which explain the reported enhancement in the adsorption performances of the composite. The capacity of each uptake site to be occupied with more than one molecule (n (CF) = 3-3.74 and n (OM) = 2.35-3.54) suggests multimolecular uptake. The energetic factors suggested physical mechanistic processes of spontaneous and exothermic behaviors either during the uptake of CF or OM.

Potentiality of chitosan hybridized magnesium doped-hydroxyapatite (CH/Mg·HAP) for enhanced carrying of oxaliplatin: loading, release, kinetics, and cytotoxicity

Magnesium-enriched hydroxyapatite was synthesized and integrated with chitosan, forming a bio-compatible biocomposite (CH/Mg·HAP) to be applied as a carrier of oxaliplatin (OXN) with enhanced loading, release, and therapeutic activities.

Synthesis and characterization of chitosan hybridized zinc phosphate/hydroxyapatite core shell nanostructure and its potentiality as delivery system of oxaliplatin drug

An advanced form of zinc phosphate/hydroxyapatite nanorods with a core-shell structure (ZPh/HPANRs) was made and then hybridized with chitosan polymeric chains to make a safe biocomposite (CH@ZPh/HPANRs) that improves the delivery structure of traditional oxaliplatin (OXPN) chemotherapy during the treatment of colorectal cancer cells. The qualifications of CH@ZPh/HPANRs in comparison with ZPh/HPANRs as a carrier for OXPN were followed based on loading, release, and cytotoxicity. CH@ZPh/HPANRs composite exhibits a notably higher OXPN loading capacity (321.75 mg/g) than ZPh/HPANRs (127.2 mg/g). The OXPN encapsulation processes into CH@ZPh/HPANRs display the isotherm behavior of the Langmuir model (R2 = 0.99) and the kinetic assumptions of pseudo-first-order kinetics (R2 > 0.89). The steric studies reflect a strong increment in the quantities of the free sites after the chitosan hybridization steps (Nm = 34.6 mg/g) as compared to pure ZPh/HPANRs (Nm = 18.7 mg/g). Also, the capacity of each site was enhanced to be loaded by 10 OXPN molecules (n = 9.3) in a vertical orientation. The OXPN loading energy into CH@ZPh/HPANRs (<40 KJ/mol) reflects physical loading reactions involving van der Waals forces and hydrogen bonding. The OXPN release profiles of CH@ZPh/HPANRs exhibit slow and controlled properties for about 140 h at pH 7.4 and 80 h at pH 5.5. The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and a complex erosion/diffusion release mechanism. The free CH@ZPh/HPANRs particles display a considerable cytotoxic effect on the HCT-116 cancer cells (9.53 % cell viability), and their OXPN-loaded product shows a strong cytotoxic effect (1.83 % cell viability).

3D-Printed Multifunctional Ag/CeO2/ZnO Reinforced Hydroxyapatite-Based Scaffolds with Effective Antibacterial and Mechanical Properties

Conventional three-dimensional (3D)-printed hydroxyapatite (HA)-based constructs have limited utility in bone tissue engineering due to their poor mechanical properties, elevated risk of microbial infection, and limited pore interconnectivity. 3D printing of complex multiple components to fabricate fully interconnected scaffolds is a challenging task; here, in this work, we have developed a procedure for fabrication of printable ink for complex systems containing multinanomaterials, i.e., HAACZ (containing 1 wt % Ag, 4 wt % CeO2, and 6 wt % ZnO) with better shear thinning and shape retention properties. Moreover, 3D-printed HAACZ scaffolds showed a modulus of 143.8 GPa, a hardness of 10.8 GPa, a porosity of 59.6%, effective antibacterial properties, and a fully interconnected pore network to be an ideal construct for bone healing. Macropores with an average size of ∼469 and ∼433 μm within the scaffolds of HA and HAACZ and micropores with an average size of ∼0.6 and ∼0.5 μm within the strut of HA and HAACZ were developed. The distribution of fully interconnected micropores was confirmed using computerized tomography, whereas the distribution of micropores within the strut was visualized using Voronoi tessellation. The water contact angle studies revealed the most suitable hydrophilic range of water contact angles of ∼71.7 and ∼76.6° for HA and HAACZ, respectively. HAACZ scaffolds showed comparable apatite formation and cytocompatibility as that of HA. Antibacterial studies revealed effective antibacterial properties for the HAACZ scaffold as compared to HA. There was a decrease in bacterial cell density for HAACZ from 1 × 105 to 1.2 × 103 cells/mm2 against Gram-negative (Escherichia coli) and from 1.9 × 105 to 5.6 × 103 bacterial cells/mm2 against Gram-positive (Staphylococcus aureus). Overall, the 3D-printed HAACZ scaffold resulted in mechanical properties, comparable to those of the cancellous bone, interconnected macro- and microporosities, and excellent antibacterial properties, which could be utilized for bone healing.

Photothermal Conversion Efficiency of Silver and Gold Incorporated Nanosized Apatites for Biomedical Applications

The aim of this research was to investigate the photothermal ability of nanocrystalline hydroxyapatite (nHAp) incorporated with silver and gold. It was studied by using a recently developed technique evaluating the photothermal conversion efficiency. The heating performance of aqueous dispersions was examined under 445 and 532 nm excitation. The largest increase in temperature was found for the 2% Ag-nHAp and reached above 2 °C per mg/mL of sample (445 nm) under 90 mW laser continuous irradiation and an external light-to-heat conversion efficiency of 0.11 L/g cm. The obtained results have shown a new functionality of nanosized apatites that has not been considered before. The studied materials have also been characterized by XRPD, TEM, BET, and UV-Vis techniques. Finally, in this work, a new idea for their application was proposed: photothermal therapy.

Gallium-Doped Hydroxyapatite: Shape Transformation and Osteogenesis Activity

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells.

Synthesis and characterization of Mg-hydroxyapatite and its cellulose hybridized structure as enhanced bio-carrier of oxaliplatin drug; equilibrium and release kinetics

An advanced form of magnesium-doped hydroxyapatite (Mg HAP) was synthesized and hybridized with cellulose fibers, producing a safe biocomposite (CF/Mg HAP) as an enhanced delivery structure of traditional oxaliplatin (OXPN) chemotherapy drug during the treatment stages of colorectal cancer. The qualifications of CF/Mg HAP as a carrier for OXPN were followed based on loading, release, and cytotoxicity as compared to Mg HAP. The CF/Mg HAP composite exhibits a notably higher OXPN encapsulation capacity (256.2 mg g-1) than the Mg HAP phase (148.9 mg g-1). The OXPN encapsulation process into CF/Mg HAP displays the isotherm behavior of the Langmuir model (R2 = 0.99) and the kinetic assumptions of pseudo-first-order kinetics (R2 > 0.95). The steric studies reflect a strong increment in the quantities of the free sites after the cellulose hybridization steps (Nm = 178.58 mg g-1) as compared to pure Mg HAP (Nm = 69.39 mg g-1). Also, the capacity of each site was enhanced to be loaded by 2 OXPN molecules (n = 1.43) in a vertical orientation. The OXPN encapsulation energy into CF/Mg HAP (<40 kJ mol-1) reflects physical encapsulation reactions involving van der Waals forces and hydrogen bonding. The OXPN release profiles of CF/Mg HAP exhibit slow and controlled properties for about 100 h, either at pH 5.5 or pH 7.4. The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and a complex erosion/diffusion release mechanism. The free CF/Mg HAP particles display a considerable cytotoxic effect on the HCT-116 cancer cells (21.82% cell viability), and their OXPN-loaded product shows a strong cytotoxic effect (1.85% cell viability).

Synthesis and Characterization of Mg-Hydroxyapatite and Its β-Cyclodextrin Composite as Enhanced Bio-Carrier of 5-Fluorouracil Drug; Equilibrium and Release Kinetics

An advanced form of magnesium-doped hydroxyapatite (Mg·HAP) was integrated in composite with β-cyclodextrin producing a safe biocomposite (β-CD/HAP) as an enhanced delivery structure of traditional 5-fluorouracil (5-FU) chemotherapy during the treatment stages of colorectal cancer cells. The qualifications of β-CD/HAP as a carrier for 5-FU were followed based on the loading, release, and cytotoxicity as compared to Mg·HAP. β-CD/HAP composite exhibits notably higher 5-FU encapsulation capacity (272.3 mg/g) than Mg·HAP phase (164.9 mg/g). The 5-FU encapsulation processes into β-CD/HAP display the isotherm behavior of the Freundlich model (R2 = 0.99) and kinetic assumptions of pseudo-first order kinetic (R2 > 0.95). The steric studies reflect a strong increment in the quantities of the free sites after the β-CD integration steps (Nm = 61.2 mg/g) as compared to pure Mg·HAP (Nm = 42.4 mg/g). Also, the capacity of each site was enhanced to be loaded by 5 of 5-FU molecules (n = 4.45) in a vertical orientation. The 5-FU encapsulation energy into β-CD/HAP (<40 kJ/mol) reflects physical encapsulation reactions involving van der Waals forces and hydrogen bonding. The 5-FU release profiles of β-CD/HAP exhibit slow and controlled properties for about 80 h either in gastric fluid (pH 1.2) or in intestinal fluid (pH 7.4). The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and complex erosion/diffusion release mechanism. The free β-CD/HAP particles display a considerable cytotoxic effect on the HCT-116 cancer cells (33.62% cell viability) and its 5-FU-loaded product shows a strong cytotoxic effect (2.91% cell viability).

Synergistic effect of drug/antibiotic-impregnated micro/nanohybrid mesoporous bioactive glass/calcium phosphate composite bone cement on antibacterial and osteoconductive activities

Calcium phosphate bone cements (CPC) can be used in minimally invasive surgery because of their injectability, and they can also be used to repair small and irregular bone defects. This study aimed to release the antibiotic gentamicin sulfate (Genta) to reduce tissue inflammation and prevent infection in the early stages of bone recovery. Subsequently, the sustained release of the bone-promoting drug ferulic acid (FA) mimicked the response of osteoprogenitor D1 cells interaction, thereby accelerating the healing process of the overall bone repair. Accordingly, the different particle properties of micro-nano hybrid mesoporous bioactive glass (MBG), namely, micro-sized MBG (mMBG) and nano-sized MBG (nMBG), were explored separately to generate different dose releases in MBG/CPC composite bone cement. Results show that nMBG had better sustained-release ability than mMBG when impregnated with the same dose. When 10 wt% of mMBG hybrid nMBG and composite CPC were used, the amount of MBG slightly shortened the working/setting time and lowered the strength but did not hinder the biocompatibility, injectability, anti-disintegration, and phase transformation of the composite bone cement. Furthermore, compared with 2.5wt%Genta@mMBG/7.5 wt% FA@nMBG/CPC, 5wt.%Genta@mMBG/5wt.%FA@nMBG/CPC exhibited better antibacterial activity, better compressive strength, stronger mineralization of osteoprogenitor cell, and similar 14-day slow-release trend of FA. The MBG/CPC composite bone cement developed can be used in clinical surgery to achieve the synergistic sustained release of antibacterial and osteoconductive activities.

In vitro and in vivo Evaluation of Folic Acid Modified DOX-Loaded 32P-nHA Nanoparticles in Prostate Cancer Therapy

Background

Prostate cancer (PCa) ranks second in the incidence of all malignancies in male worldwide. The presence of multi-organ metastases and tumor heterogeneity often leads to unsatisfactory outcomes of conventional radiotherapy treatments. This study aimed to develop a novel folate-targeted nanohydroxyapatite (nHA) coupling to deliver adriamycin (Doxorubicin, DOX), ³²P, and ^99mTc simultaneously for the diagnosis and treatment of prostate-specific membrane antigen (PSMA) positive prostate cancer.

Methods

The spherical nHA was prepared by the biomimetic method and characterized. Folic acid (FA) was coupled to nHA with polyethylene glycol (PEG), and the grafting ratio of PEG-nHA and FA-PEG-nHA was determined by the thermogravimetric analysis (TGA) method. In addition, ³²P, ^99mTc, and DOX were loaded on nHA by physisorption. And the labeling rate and stability of radionuclides were measured by a γ-counter. The loading and release of DOX at different pH were determined by the dialysis method. Targeting of FA-PEG-nHA loaded with ^99mTc was verified by in vivo SPECT imaging. In vitro anti-tumor effect of ³²P/DOX-FA-PEG-nHA was assessed with apoptosis assay. The safety of the nano-drugs was verified by histopathological analysis.

Results

The SEM images showed that the synthesized nHA was spherical with uniform particle size (average diameter of about 100nm). The grafting ratio is about 10% for PEG and about 20% for FA. The drug loading and the delayed release of DOX at different pH confirmed its long-term therapeutic ability. The labeling of ³²P and ^99mTc was stable and the labeling rate was great. SPECT showed that FA-PEG-nHA showed well in vivo tumor targeting and less damage to normal tissues.

Conclusion

FA-targeted nHA loaded with ³²P, ^99mTc, and DOX may be a new diagnostic and therapeutic strategy for targeting PSMA-positive prostate cancer tumors, which may achieve better therapeutic results while circumventing the severe toxic side effects of conventional chemotherapeutic agents.

Modulated Laser Cladding of Implant-Type Coatings by Bovine-Bone-Derived Hydroxyapatite Powder Injection on Ti6Al4V Substrates-Part I: Fabrication and Physico-Chemical Characterization

The surface physico-chemistry of metallic implants governs their successful long-term functionality for orthopedic and dentistry applications. Here, we investigated the feasibility of harmoniously combining two of the star materials currently employed in bone treatment/restoration, namely, calcium-phosphate-based bioceramics (in the form of coatings that have the capacity to enhance osseointegration) and titanium alloys (used as bulk implant materials due to their mechanical performance and lack of systemic toxicity). For the first time, bovine-bone-derived hydroxyapatite (BHA) was layered on top of Ti6Al4V substrates using powder injection laser cladding technology, and then subjected, in this first stage of the research, to an array of physical-chemical analyses. The laser processing set-up involved the conjoined modulation of the BHA-to-Ti ratio (100 wt.% and 50 wt.%) and beam power range (500-1000 W). As such, on each metallic substrate, several overlapped strips were produced and the external surface of the cladded coatings was further investigated. The morphological and compositional (SEM/EDS) evaluations exposed fully covered metallic surfaces with ceramic-based materials, without any fragmentation and with a strong metallurgical bond. The structural (XRD, micro-Raman) analyses showed the formation of calcium titanate as the main phase up to maximum 800 W, accompanied by partial BHA decomposition and the consequential advent of tetracalcium phosphate (markedly above 600 W), independent of the BHA ratio. In addition, the hydrophilic behavior of the coatings was outlined, being linked to the varied surface textures and phase dynamism that emerged due to laser power increment for both of the employed BHA ratios. Hence, this research delineates a series of optimal laser cladding technological parameters for the adequate deposition of bioceramic layers with customized functionality.

Low Concentrations of Silver Nanoparticles Inhibit Spore Germination and Disturb Gender Differentiation of Ceratopteris thalictroides (L.) Brongn

Because of their excellent antibacterial properties, silver nanoparticles (AgNPs) are widely used in all walks of life, which has caused them to be discharged into aquatic environments with possible negative effects on aquatic plants. In the present study, we used an aquatic fern, Ceratopteris thalictroides, as a model to investigate the effects of AgNPs on its spore germination, gametophytes, sex differentiation, and growth. The results demonstrated that AgNPs significantly inhibited spore germination of C. thalictroides at a AgNP concentration higher than 0.02 mg/L. Additionally, we found sex-dependent effects of AgNPs on the development and growth of the gametophyte of C. thalictroides. The proportion of hermaphrodites in the gametophytes and the area of gametophytes significantly decreased under AgNP treatment, while no significant effect was observed in the male gametophytes. Using the AgNP filtrate (without nanoparticles) and AgNPs plus cysteine (Ag⁺ chelator), we found that the release of Ag⁺ from nanoparticles was not the cause of the toxicity of AgNPs on C. thalictroides. The EC₅₀ of AgNPs on spore germination was 0.0492 mg/L, thus indicating an ecological risk of AgNPs on this species even at concentrations lower than the Ag element concentration of the WHO guidelines for drinking-water quality.

ZnO/Ag Nanocomposites with Enhanced Antimicrobial Activity

In this study, ZnO/Ag nanocomposites were synthesized using a facile chemical route involving metallic precursors of zinc acetate dehydrate and silver acetate, and dissolving the two metallic precursors in EtOH. The final concentration of the solution was 0.4 M. The different nanocomposites were synthesized using different atomic percentages of silver to compare the amount of silver nanoparticles with the bactericidal power of the nanocomposites. They were prepared at concentrations of 0, 1, 3, 5, 7, and 10 at%. The as-prepared nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) to study their structural and morphological properties. SEM showed that there is a clear effect of Ag on the size of the ZnO particles, since when silver percentages of 1 at% are included, the grain size obtained is much smaller than that of the ZnO synthesis. The effect is maintained for 3, 5, 7, and 10 at% silver. Transmission electron microscopy (TEM) compositional mapping confirms the presence of spherical nanoparticles in the synthesized samples. The size of the nanoparticles ranges from about 10 to about 30 nm. In addition, UV-Vis and Raman spectroscopy were performed to obtain structural details. The different samples show an increase in the absorption in the visible range due to the incorporation of the silver NPs. Measurement of the antimicrobial activity was tested against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) It is shown that zinc oxide has bactericidal power for these two groups of bacteria and also that when it is used together with silver NP, this effect improves, eliminating more than 90% of inoculated bacteria.

Enhancement of Anticorrosive Performance of Cardanol Based Polyurethane Coatings by Incorporating Magnetic Hydroxyapatite Nanoparticles

The present investigation demonstrates renewable cardanol-based polyol for the formulation of nanocomposite polyurethane (PU) coatings. The functional and structural features of cardanol polyol and nanoparticles were studied using FT-IR and 1H NMR spectroscopic techniques. The magnetic hydroxyapatite nanoparticles (MHAPs) were dispersed 1–5% in PU formulations to develop nanocomposite anticorrosive coatings. An increase in the strength of MHAP increased the anticorrosive performance as examined by immersion and electrochemical methods. The nanocomposite PU coatings showed good coating properties, viz., gloss, pencil hardness, flexibility, cross-cut adhesion, and chemical resistance. Additionally, the coatings were also studied for surface morphology, wetting, and thermal properties by scanning electron microscope (SEM), contact angle, and thermogravimetric analysis (TGA), respectively. The hydrophobic nature of PU coatings increased by the addition of MHAP, and an optimum result (105°) was observed in 3% loading. The developed coatings revealed its hydrophobic nature with excellent anticorrosive performance.