Structural Characterization and Antifungal Studies of Zinc-Doped Hydroxyapatite Coatings

Microstructural, biocompatibility and mechanical investigation of MgHAp and AgHAp: Comparative report

It is imperative to investigate the effect of addition of different size metallic ions in HAp and study the changes in biocompatibility and mechanical properties. Silver and magnesium ions are two vital ions needed in our body. Silver ions are known to inhibit the microbes, while magnesium ions are known to increase the mechanical properties. The present study reports the comparative properties of MgHAp and AgHAp synthesised by sol-gel wet chemical method. Changes in the morphology, phase analysis, corrosion resistance, dielectric properties, hardness and the thrombus behaviour of HAp doped Ag and Mg ions has been investigated. In this work, we have presented a comparative study of both the metal doped ionsto find which of the ions and which weight percent of the ions can be best suited to be incorporated into the HAp matrix for hard tissue implants. All wt% AgHAp showed the better corrosion resistance than all the MgHAp samples. However, MgHAp showed higher value of hardness in comparison to AgHAp samples. The mechanical strength was found to increase with the increase in Mg wt% in MgHAp but for AgHAp the hardness value decreased with increase in the concentration. The impedance and dielectric loss decreased with increasing frequency for both the samples. Both the ion doped hydroxyapatite showed moderate clotting behaviour as compared to pure HAp. But 2 wt% MgHAp and 4 wt% AgHAp showed better thrombogenic behaviour. It is imperative to investigate the effect of addition of different size metallic ions in HAp and study the changes in biocompatibility and mechanical properties. Silver and magnesium ions are two vital ions needed in our body. Silver ions are known to inhibit the microbes, while magnesium ions are known to increase the mechanical properties. The present study reports the comparative properties of MgHAp and AgHAp synthesised by sol-gel wet chemical method. Changes in the morphology, phase analysis, corrosion resistance, dielectric properties, hardness and the thrombus behaviour of HAp doped Ag and Mg ions has been investigated. In this work we have presented a comparative study of both the metal doped ions to find which of the ions and which weight percent of the ions can be best suited to be incorporated into the HAp matrix for hard tissue implants. All wt% AgHAp showed the better corrosion resistance than all the MgHAp samples. However, MgHAp showed higher value of hardness in comparison to AgHAp samples. The mechanical strength was found to increase with the increase in Mg wt% in MgHAp but for AgHAp the hardness value decreased with increase in the concentration. The impedance and dielectric loss decreased with increasing frequency for both the samples. Both the ion doped hydroxyapatite showed moderate clotting behaviour as compared to pure HAp. But 2 wt% MgHAp and 4 wt% AgHAp showed better thrombogenic behaviour.

Physicochemical Characterization of Europium-Doped Hydroxyapatite Thin Films with Antifungal Activity

Owing to its unique biological and physicochemical properties, hydroxyapatite (HAp) represents one of the most extensively studied biomaterials for biomedical applications. It is well known that Candida is currently one of the fungi frequently involved in the onset and development of post-implant infections and, owing to the appearance of antifungal resistance, it is quite difficult to treat despite all the tremendous efforts made in this regard by the scientific world. Therefore, in this context, we report for the first time in this paper, the development and characterization of europium-doped thin films (5EuHAp, xEu = 0.05) on a Si substrate by a spin-coating method. The results of ultrasound (US), zeta (ζ) potential, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) studies are presented. The XRD studies conducted on 5EuHAp suspension revealed the nanometric dimensions of the particles and sample purity. In addition, a moderate stability of the 5EuHAp suspension was observed. XPS measurements revealed the presence of Eu 3d in the 5EuHAp thin films. In the SEM micrographs, the surface uniformity and the absence of the surface defects could be observed. Moreover, the results of the FTIR studies showed the presence of the vibrational bands specific to the HAp structure in the studied sample. The antifungal activity of the HAp and 5EuHAp suspensions and coatings was evaluated using the Candida albicans ATCC 10231 (C. albicans) fungal strain. The qualitative assays of the antifungal properties of HAp and 5EuHAp coatings were also visualized by SEM and CLSM. The antifungal studies revealed that both 5EuHAp suspensions and coatings exhibited noticeable antifungal activity against C. albicans cells.

Electrochemical Surface Biofunctionalization of Titanium through Growth of TiO2 Nanotubes and Deposition of Zn Doped Hydroxyapatite

The current research aim is to biofunctionalize pure titanium (Ti, grade IV) substrate with titania nanotubes and Zn doped hydroxyapatite-based coatings by applying a duplex electrochemical treatment, and to evaluate the influence of Zn content on the physico-chemical properties of hydroxyapatite (HAp). The obtained nanostructured surfaces were covered with HAp-based coatings doped with Zn in different concentrations by electrochemical deposition in pulsed galvanostatic mode. The obtained surfaces were characterized in terms of morphology, elemental and phasic composition, chemical bonds, roughness, and adhesion. The nanostructured surface consisted of titania nanotubes (NT), aligned, vertically oriented, and hollow, with an inner diameter of ~70 nm. X-ray Diffraction (XRD) analysis showed that the nanostructured surface consists of an anatase phase and some rutile peaks as a secondary phase. The morphology of all coatings consisted of ribbon like-crystals, and by increasing the Zn content the coating became denser due to the decrement of the crystals’ dimensions. The elemental and phase compositions evidenced that HAp was successfully doped with Zn through the pulsed galvanostatic method on the Ti nanostructured surfaces. Fourier Transform Infrared spectroscopy (FTIR) and XRD analysis confirmed the presence of HAp in all coatings, while the adhesion test showed that the addition of a high quantity leads to some delamination. Based on the obtained results, it can be said that the addition of Zn enhances the properties of HAp, and through proper experimental design, the concentration of Zn can be modulated to achieve coatings with tunable features.

Bioactive Surface Modifications through Thermally Sprayed Hydroxyapatite Composite Coatings: A Review over Selective Reinforcements

Hydroxyapatite (HA) has been an excellent replacement for the natural bone in orthopedic applications, owing to its close resemblance; however, it is brittle and has low strength. Surface modification techniques...

Fabrication of Novel Chitosan–Hydroxyapatite Nanostructured Thin Films for Biomedical Applications

In this study, we develop chitosan–hydroxyapatite (CS–HAp) composite layers that were deposited on Si substrates in radio frequency (RF) magnetron sputtering discharge in argon gas. The composition and structure of CS–HAp composite layers were investigated by analytical techniques, such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), metallographic microscopy (MM), and atomic force microscopy (AFM). On the other hand, in the present study the second order derivative of FT-IR–ATR spectra, for compositional analyses of CS–HAp, were used. The SEM, MM, and AFM data have shown the formation of CS–HAp composite layers. The surface of CS–HAp composite layers showed uniform growth (at an Ar gas working pressure of p = 2 × 10−3 mbar). The surface of the CS–HAp composites coatings became more nanostructured, becoming granular as the gas pressure increased from 5 × 10−3 to 1.2 × 10−2 mbar. However, our studies revealed that the surface morphology of the CS–HAp composite layers varies with the Ar gas working pressure. At the same time, optical properties are slightly influenced by Ar pressure. Their unique physicochemical properties make them suitable for various applications in the biomedical field, if we consider the already proven antimicrobial properties of chitosan. The antifungal properties and the capacity of the CS–HAp composite layers to inhibit the development of fungal biofilms were also demonstrated using the Candida albicans ATCC 10231 (C. albicans) fungal strain.

Development of an Immunochromatographic Strip Using Conjugated Gold Nanoparticles for the Rapid Detection of Klebsiella pneumoniae Causing Neonatal Sepsis

Neonatal sepsis is a leading cause of death among newborns and infants, especially in the developing world. The problem is compounded by the delays in pinpointing the causative agent of the infection. This is reflected in increasing mortality associated with these cases and the spread of multi-drug-resistant bacteria. In this work, we deployed bioinformatics and proteomics analyses to determine a promising target that could be used for the identification of a major neonatal sepsis causative agent, Klebsiella pneumoniae. A 19 amino acid peptide from a hypothetical outer membrane was found to be very specific to the species, well conserved among its strains, surface exposed, and expressed in conditions simulating infection. Antibodies against the selected peptide were conjugated to gold nanoparticles and incorporated into an immunochromatographic strip. The developed strip was able to detect as low as 10⁵ CFU/mL of K. pneumoniae. Regarding specificity, it showed negative results with both Escherichia coli and Enterobacter cloacae. More importantly, in a pilot study using neonatal sepsis cases blood specimens, the developed strip selectively gave positive results within 20 min with those infected with K. pneumoniae without prior sample processing. However, it gave negative results in cases infected with other bacterial species.

Nigella Sativa-Coated Hydroxyapatite Scaffolds: Synergetic Cues to Stimulate Myoblasts Differentiation and Offset Infections

BACKGROUND

At present osteoporosis has come into view as a major health concern. Skeletal diseases typified by weak and fragile bones have imposed threats of fissure. Hydroxyapatite (HAP) is known to induce osteoblast like differentiation and provide mechanical strength, hence, used in bone tissue engineering; whereas, Nigella sativa has also demonstrated potential to treat bone and muscle diseases. This study was aimed to develop potential orthopedic scaffold exploiting natural resources of Saudi Arabia which can be used as prospective tissue engineering implant.

METHODS

The bone scaffold was developed by grafting biogenic HAP with N. sativa essential oil. N. sativa was applied for boosting osteogenesis and to stimulate antimicrobial potential. Antimicrobial potential was investigated utilizing S. aureus bacteria. Spectroscopic and surface characters of N. sativa grafted HAP scaffolds were analyzed using Fourier-transform infrared spectroscopy, X-ray crystallography and Scanning electron microscopy. To ensure biocompatibility of scaffolds; we selected C2C12 cell-lines; best model to study mechanistic pathways related to osteoblasts and myoblasts differentiation.

RESULTS

Grafting of HAP with N. sativa did not affect typical spherical silhouette of nanoparticles. Characteristically; protein loaded polynucleated myotubes are result of in vitro myogenesis of C2C12 myoblasts in squat serum environment.

CONCLUSION

It is first study of unique combination of N. sativa and HAP scaffold as a possible candidate of implantation for skeletal muscles regeneration. Outcome of this finding revealed N. sativa grafted HAP enhance differentiation significantly over that of HAP. The proposed scaffold will be an economical natural material for hard and soft tissue engineering and will aid in curing skeletal muscle diseases. Our findings have implications for treatment of muscular/bone diseases.

Structure-Activity Relationship of Lanthanide-Incorporated Nano-Hydroxyapatite for the Adsorption of Fluoride and Lead

The growing demand for water purification provided the initial momentum to produce lanthanide-incorporated nano-hydroxyapatite (HAP) such as HAP·CeO2, HAP·CeO2·La(OH)3 (2:1), and HAP·CeO2·La(OH)3 (3:2). These materials open avenues to remove fluoride and lead ions from contaminated water bodies effectively. Composites of HAP containing CeO2 and La(OH)3 were prepared using in situ wet precipitation of HAP, followed by the addition of Ce(SO4)2 and La(NO3)3 into the same reaction mixture. The resultant solids were tested for the removal of fluoride and lead ions from contaminated water. It was found that the composite HAP·CeO2 shows fluoride and lead ion removal capacities of 185 and 416 mg/g, respectively. The fluoride removal capacity of the composite was improved when La(OH)3 was incorporated and it was observed that the composite HAP·CeO2·La(OH)3 (3:2) has the highest recorded fluoride removal capacity of 625 mg/g. The materials were characterized using scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) spectrometry, Fourier transform infrared (FT-IR) spectrometry, X-ray powder diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area analysis. Analysis of results showed that Ce and La are incorporated in the HAP matrix. Results of kinetic and leaching analyses indicated a chemisorptive behavior during fluoride and lead ion adsorption by the composites; meanwhile, the thermodynamic profile shows a high degree of feasibility for fluoride and lead adsorption.

Investigation of Spin Coating Cerium-Doped Hydroxyapatite Thin Films with Antifungal Properties

In this study, the cerium-doped hydroxyapatite (Ca10−xCex(PO4)6(OH)2 with xCe = 0.1, 10Ce-HAp) coatings obtained by the spin coating method were presented for the first time. The stability of the 10Ce-HAp suspension particles used in the preparation of coatings was evaluated by ultrasonic studies, transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The surface morphology of the 10Ce-HAp coating was studied by SEM and atomic force microscopy (AFM) techniques. The obtained 10Ce-HAp coatings were uniform and without cracks or unevenness. Glow discharge optical emission spectroscopy (GDOES) and X-ray photoelectron spectroscopy (XPS) were used for the investigation of fine chemical depth profiling. The antifungal properties of the HAp and 10Ce-HAp suspensions and coatings were assessed using Candida albicans ATCC 10231 (C. albicans) fungal strain. The quantitative antifungal assays demonstrated that both 10Ce-HAp suspensions and coatings exhibited strong antifungal properties and that they successfully inhibited the development and adherence of C. albicans fungal cells for all the tested time intervals. The scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) visualization of the C. albicans fungal cells adherence to the 10Ce-HAp surface also demonstrated their strong inhibitory effects. In addition, the qualitative assays also suggested that the 10Ce-HAp coatings successfully stopped the biofilm formation.

Role of Zinc-Doped Bioactive Glass Encapsulated with Microspherical Gelatin in Localized Supplementation for Tissue Regeneration: A Contemporary Review

Gelatin, a natural polymer, provides excellent tissue compatibility for use in tissue rehabilitation. Bioactive glasses (BAG) offer superior capacity in stimulating a bioactive response but show high variability in uptake and solubility. To tackle these drawbacks, a combination of gelatin with BAG is proposed to form composites, which then offer a synergistic response. The cross-linked gelatin structure's mechanical properties are enhanced by the incorporation of the inorganic BAG, and the rate of BAG ionic supplementation responsible for bioactivity and regenerative potential is better controlled by a protective gelatin layer. Several studies have demonstrated the cellular benefits of these composites in different forms of functional modification such as doping with zinc or incorporation of zinc such as ions directly into the BAG matrix. This review presents a comprehensive perspective on the individual characteristics of BAG and gelatin, including the synthesis and mechanism of action. Further, adaptation of the composite into various applications for bone tissue engineering is discussed and future challenges are highlighted.

Physico-Chemical Properties and In Vitro Antifungal Evaluation of Samarium Doped Hydroxyapatite Coatings

Hydroxyapatite (HAp) and samarium doped hydroxyapatite, Ca10−xSmx(PO4)6(OH)2, xSm = 0.05, (5SmHAp), coatings were prepared by sol-gel process using the dip coating method. The stability of 5SmHAp suspension was evaluated by ultrasound measurements. Fourier transform infrared spectroscopy (FTIR) was used to examine the optical characteristics of HAp and 5SmHAp nanoparticles in suspension and coatings. The FTIR analysis revealed the presence of the functional groups specific to the structure of hydroxyapatite in the 5SmHAp suspensions and coatings. The morphology of 5SmHAp nanoparticles in suspension was evaluated by transmission electron microscopy (TEM). Moreover, scanning electron microscope (SEM) was used to evaluate the morphology of nanoparticle in suspension and the morphology of the surface on the coating. The SEM and TEM studies on 5SmHAp nanoparticles in suspension showed that our samples consist of nanometric particles with elongated morphology. The SEM micrographs of HAp and 5SmHAp coatings pointed out that the coatings are continuous and homogeneous. The surface morphology of the 5SmHAp coatings was also assessed by Atomic Force Microscopy (AFM) studies. The AFM results emphasized that the coatings presented the morphology of a uniformly deposited layer with no cracks and fissures. The crystal structure of 5SmHAp coating was characterized by X-ray diffraction (XRD). The surface composition of 5SmHAp coating was analyzed by X-ray photoelectron spectroscopy (XPS). The XRD and XPS analysis shown that the Sm3+ ions have been incorporated into the 5SmHAp synthesized material. The antifungal properties of the 5SmHAp suspensions and coatings were studied using Candida albicans ATCC 10231 (C. albicans) fungal strains. The quantitative results of the antifungal assay showed that colony forming unity development was inhibited from the early phase of adherence in the case of both suspensions and coatings. Furthermore, the adhesion, cell proliferation and biofilm formation of the C. albicans were also investigated by AFM, SEM and Confocal Laser Scanning Microscopy (CLSM) techniques. The results highlighted that the C. albicans adhesion and cell development was inhibited by the 5SmHAp coatings. Moreover, the data also revealed that the 5SmHAp coatings were effective in stopping the biofilm formation on their surface. The toxicity of the 5SmHap was also investigated in vitro using HeLa cell line.

Obtaining and Characterizing Thin Layers of Magnesium Doped Hydroxyapatite by Dip Coating Procedure

A simple dip coating procedure was used to prepare the magnesium doped hydroxyapatite coatings. An adapted co-precipitation method was used in order to obtain a Ca25−xMgx(PO4)6(OH)2, 25MgHAp (xMg = 0.25) suspension for preparing the coatings. The stabilities of 25MgHAp suspensions were evaluated using ultrasound measurements, zeta potential (ZP), and dynamic light scattering (DLS). Using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) information at nanometric resolution regarding the shape and distribution of the 25MgHAp particles in suspension was obtained. The surfaces of obtained layers were evaluated using SEM and atomic force microscopy (AFM) analysis. The antimicrobial evaluation of 25MgHAp suspensions and coatings on various bacterial strains and fungus were realized. The present study presents important results regarding the physico-chemical and antimicrobial studies of the magnesium doped hydroxyapatite suspensions, as well as the coatings. The studies have shown that magnesium doped hydroxyapatite suspensions prepared with xMg = 0.25 presented a good stability and relevant antimicrobial properties. The coatings made using 25MgHAp suspension were homogeneous and showed remarkable antimicrobial properties. Also, it was observed that the layer realized has antimicrobial properties very close to those of the suspension. Both samples of the 25MgHAp suspensions and coatings have very good biocompatible properties.

Synthesis and Properties of Zinc-Modified Hydroxyapatite

Hydroxyapatites modified with metal ions are the main inorganic components of bone tissue and are approved for use as components for biocomposites and coatings for surgical implants. This study examined prototypes of functional materials for bone implants based on hydroxyapatite modified with zinc ions. Zinc-modified hydroxyapatite was composed and synthesized. Using the XRD method, the phase composition was established. Using SEM, EPMA, and low-temperature nitrogen adsorption (BET) methods, surface properties were investigated. Antibacterial activity and biocompatibility have been established. The studied materials have antimicrobial activity; the samples did not cause significant changes in either the internal organs or the general condition of laboratory animals during the entire experiment.

Peppermint Essential Oil-Doped Hydroxyapatite Nanoparticles with Antimicrobial Properties

This study aimed at developing an antimicrobial material based on hydroxyapatite (HAp) and peppermint essential oil (P-EO) in order to stimulate the antimicrobial activity of hydroxyapatite. The molecular spectral features and morphology of the P-EO, HAp and hydroxyapatite coated with peppermint essential oil (HAp-P) were analyzed using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The coating of the HAp with the P-EO did not affect the ellipsoidal shape of the nanoparticles. The overlapping of IR bands of P-EO and HAp in the HAp-P spectrum determined the formation of the broad molecular bands that were observed in the spectral regions of 400-1000 cm-1 and 1000-1200 cm-1. The antibacterial activity of the P-EO, HAp and HAp-P were also tested against different Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) 388, S. aureus ATCC 25923, S. aureus ATCC 6538, E. faecium DSM 13590), Gram-negative bacteria (Escherichia coli ATCC 25922, E. coli C5, P. aeruginosa ATCC 27853, P. aeruginosa ATCC 9027) and a fungal strain of Candida parapsilosis. The results of the present study revealed that the antimicrobial activity of HAp-P increased significantly over that of HAp.

The Fate of Osteoblast-Like MG-63 Cells on Pre-Infected Bactericidal Nanostructured Titanium Surfaces

Biomaterials that have been newly implanted inside the body are the substratum targets for a "race for the surface", in which bacterial cells compete against eukaryotic cells for the opportunity to colonize the surface. A victory by the former often results in biomaterial-associated infections, which can be a serious threat to patient health and can undermine the function and performance of the implant. Moreover, bacteria can often have a 'head start' if implant contamination has taken place either prior to or during the surgery. Current prevention and treatment strategies often rely on systemic antibiotic therapies, which are becoming increasingly ineffective due to a growing prevalence of antibiotic-resistant bacteria. Nanostructured surfaces that kill bacteria by physically rupturing bacterial cells upon contact have recently emerged as a promising solution for the mitigation of bacterial colonization of implants. Furthermore, these nanoscale features have been shown to enhance the adhesion and proliferation of eukaryotic cells, which is a key to, for example, the successful osseointegration of load-bearing titanium implants. The bactericidal activity and biocompatibility of such nanostructured surfaces are often, however, examined separately, and it is not clear to what extent bacterial cell-surface interactions would affect the subsequent outcomes of host-cell attachment and osseointegration processes. In this study, we investigated the ability of bactericidal nanostructured titanium surfaces to support the attachment and growth of osteoblast-like MG-63 human osteosarcoma cells, despite them having been pre-infected with pathogenic bacteria. MG-63 is a commonly used osteoblastic model to study bone cell viability, adhesion, and proliferation on the surfaces of load-bearing biomaterials, such as titanium. The nanostructured titanium surfaces used here were observed to kill the pathogenic bacteria, whilst simultaneously enhancing the growth of MG-63 cells in vitro when compared to that occurring on sterile, flat titanium surfaces. These results provide further evidence in support of nanostructured bactericidal surfaces being used as a strategy to help eukaryotic cells win the "race for the surface" against bacterial cells on implant materials.

Evaluation of Antibacterial Activity of Zinc-Doped Hydroxyapatite Colloids and Dispersion Stability Using Ultrasounds

This study proves that the new developed zinc-doped hydroxyapatite (ZnHAp) colloids by an adapted sol-gel method can be widely used in the pharmaceutical, medical, and environmental industries. ZnHAp nanoparticles were stabilized in an aqueous solution, and their colloidal dispersions have been characterized by different techniques. Scanning Electron Microscopy (SEM) was used to get information on the morphology and composition of the investigated samples. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the elemental compositions of ZnHAp colloidal dispersions. The homogeneous and uniform distribution of constituent elements (zinc, calcium, phosphorus, oxygen) was highlighted by the obtained elemental mapping results. The X-ray diffraction (XRD) results of the obtained samples showed a single phase corresponding to the hexagonal hydroxyapatite. The characteristic bands of the hydroxyapatite structure were also evidenced by Fourier-transform infrared spectroscopy (FTIR) analysis. For a stability assessment of the colloidal system, ζ-potential for the ZnHAp dispersions was estimated. Dynamic light scattering (DLS) was used to determine particles dispersion and hydrodynamic diameter (DHYD). The goal of this study was to provide for the first time information on the stability of ZnHAp particles in solutions evaluated by non-destructive ultrasound-based technique. In this work, the influence of the ZnHAp colloidal solutions stability on the development of bacteria, such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), was also established for the first time. The antimicrobial activity of ZnHAp solutions was strongly influenced by both the stability of the solutions and the amount of Zn.

Zinc Doped Hydroxyapatite Thin Films Prepared by Sol–Gel Spin Coating Procedure

In this study, ZnHAp layers deposited on a Si substrate were obtained by a sol–gel spin-coating procedure. The ZnHAp solutions used to obtain the ZnHAp coatings were investigated by dynamic light scattering (DLS) analysis, ζ-potential, ultrasound measurements, and flame atomic absorption spectrometry (AAS). The average measured hydrodynamic diameter from the DLS analysis, ζ-potential, and ultrasound measurements were analyzed so as to characterize and estimate the stability of the ZnHAp nanoparticles. The AAS results confirmed the presence of zinc in the gels used in the preparation of the ZnHAp layers. The layers were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed the diffraction peaks of the hexagonal hydroxyapatite in all of the investigated samples. The morphology of the ZnHAp coatings annealed at 500 °C (ZnHAp-500) and 700 °C (ZnHAp-700), which evidenced that no fissures or cracks formed on the surface of the coatings. The biocompatibility assays indicated that the ZnHAp coatings did not present any toxicity towards the HeLa cells. Furthermore, the study regarding the cytotoxicity of the ZnHAp layers against microorganisms emphasized that ZnHAp coatings exhibited an inhibitory effect towards S. aureus bacterial cells and also towards C. albicans fungal cells.

The effect of applied voltages on the structure, apatite-inducing ability and antibacterial ability of micro arc oxidation coating formed on titanium surface

The micro arc oxidation (MAO) coatings with different concentrations of Ca, P and Zn elements are successfully formed on the titanium substrate at the different applied voltages. After MAO treatment, the MAO coating exhibits the porous surface structure and composed of anatase and rutile TiO2 phases. Meanwhile, the average size and density of micro-pores on the MAO coatings have been modified via the adjusting the applied voltages. In addition, the contents of the incorporated elements such as Zn, Ca and P elements in the MAO coatings have been optimized. The bonding strength test results reveal that the MAO coating shows higher bonding strength, which is up to 45 ± 5 MPa. Compared to the pure Ti plate, the MAO coating formed at 350 and 400 V show good apatite-inducing ability. Meanwhile, the MAO coating containing Zn, Ca and P elements have better antibacterial ability for E.coli and S.aureus. Thus, the incorporation of Zn, Ca and P elements was an effective method to improve the antibacterial ability. Moreover, the concentrations of Zn, Ca and P elements could be adjusted with the changing of the applied voltages. As a result, the enhancement of the antibacterial ability on the MAO coating surfaces was depended on the comprehensive effect of the incorporated elements and the surface property of MAO coatings.

Development of Zinc-Doped Hydroxyapatite by Sol-Gel Method for Medical Applications

Zinc- (Zn) doped hydroxyapatite (HAp) were prepared by sol-gel method. Zinc-doped hydroxyapatite (ZnHAp) and HAp were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Rietveld analysis revealed that the HAp and 7ZnHAp powders obtained by sol-gel method have a monophasic hydroxyapatite structure belonging to the P63/m spatial group. The results obtained from the ultrasound characterization of HAp and ZnHAp are also presented in this study. The effect of zinc concentration on properties that were deduced from ultrasonic measurements are studied in the case of a significant zinc concentration (xZn = 0.07). From the values of the ultrasonic waves velocities were determined by the pairs of elastic coefficients of the suspensions (Young modulus E, Poisson coefficient ν), which have proven to be similar to those determined by other authors.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Bioceramic Layers with Antifungal Properties

The sol-gel method was used to synthesize the silver doped hydroxyapatite (Ag:HAp) gels in order to produce the antifungal composite layers. The pure Ti disks were used as the substrate for the composite layers. Important information about suspensions used to make Ag:HAp composite layers were obtained from an ultrasonic technique. The identification of the phase composition of the Ag:HAp composite layers was accomplished X-ray diffraction (XRD). The morphology and the thickness of the layers was evaluated using scanning electron microscopy (SEM). The uniform distribution of the constituent elements (Ag, Ca, P, and O) in both analyzed samples was observed. The antifungal activity of the samples against Candida albicans ATCC 10231 microbial strain were investigated immediately after their preparation and six months later. SEM and confocal laser scanning microscopy (CLSM) images showed that the composite layers at the two time intervals exhibited a strong antifungal activity against Candida albicans ATCC 10231 and completely inhibited the biofilm formation.

Antimicrobial Activity of New Materials Based on Lavender and Basil Essential Oils and Hydroxyapatite

This study presents, for the first-time, the results of a study on the hydrodynamic diameter of essential oils (EOs) of basil and lavender in water, and solutions of EOs of basil (B) and lavender (L) and hydroxyapatite (HAp). The possible influence of basil and lavender EOs on the size of hydroxyapatite nanoparticles was analyzed by Scanning Electron Microscopy (SEM). We also investigated the in vitro antimicrobial activity of plant EOs and plant EOs hydroxyapatite respectively, against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus1144 (MRSA 1144) and S. aureus 1426) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Escherichia coli ESBL 4493). From the autocorrelation function, obtained by Dynamic Light Scattering (DLS) measurements it was observed that basil yielded one peak at an average hydrodynamic diameter of 354.16 nm, while lavender yielded one peak at an average hydrodynamic diameter of 259.76 nm. In the case of HAp nanoparticles coated with basil (HApB) and lavender (HApL) essential oil, the aggregation was minimal. We found that the lavender EO exhibited a very good inhibitory growth activity (MIC values ranging from <0.1% for E. coli reference strain to 0.78% for S. aureus strains). The biological studies indicated that HapL material displayed an enhanced antimicrobial activity, indicating the potential use of HAp as vehicle for low concentrations of lavender EO with antibacterial properties. Flow cytometry analysis (FCM) allowed us to determine some of the potential mechanisms of the antimicrobial activities of EOs, suggesting that lavender EO was active against E. coli by interfering with membrane potential, the membrane depolarization effect being increased by incorporation of the EOs into the microporous structure of HAp. These findings could contribute to the development of new antimicrobial agents that are urgently needed for combating the antibiotic resistance phenomena.

Properties of Basil and Lavender Essential Oils Adsorbed on the Surface of Hydroxyapatite

The research conducted in this study presented for the first time results of physico-chemical properties and in vitro antimicrobial activity of hydroxyapatite plant essential oil against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus 0364) and Gram-negative bacteria (Escherichia coli ATCC 25922). The samples were studied by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to determine the morphology and structure of the nanocomposites of hydroxyapatite coated with basil (HAp-B) and lavender (HAp-L) essential oils (EOs). The values of the BET specific surface area (SBET), total pore volume (VP) and pore size (DP) were determined. The results for the physico-chemical properties of HAp-L and HAp-B revealed that lavender EOs were well adsorbed on the surface of hydroxyapatite, whereas basil EOs showed a poor adsorption on the surface of hydroxyapatite. We found that the lavender EOs hydroxyapatite (HAp-L) exhibited a very good inhibitory growth activity. The value of the minimum inhibitory concentration (MIC) related to growth bacteria was 0.039 mg/mL for MRSA, 0.02 mg/mL for S. aureus and 0.039 mg/mL E. coli ATCC 25922. The basil EO hydroxyapatite (HAp-B) showed poor inhibition of bacterial cell growth. The MIC value was 0.625 mg/mL for the HAp-B sample in the presence of the MRSA bacteria, 0.313 mg/mL in the presence of S. aureus and 0.078 mg/mL for E. coli ATCC 25922.

The Effect of UV Aging on Antimicrobial and Mechanical Properties of PLA Films with Incorporated Zinc Oxide Nanoparticles

The aim of this study was to examine the influence of accelerated UV-aging on the activity against chosen microorganisms and the mechanical properties of poly-lactic acid (PLA) films enhanced with ZnO nanoparticles. The pure PLA films and tri-layered PLAZnO1%/PLA/PLAZnO1% films of 150 &micro;m thickness were extruded. The samples were treated with UV-A and Q-SUN irradiation. After irradiation the antimicrobial activity and mechanical properties of the films were analyzed. The results of the study demonstrated that PLA films did not inhibit the growth of Staphylococcus aureus, Bacillus cereus, Escherichia coli, Bacillus atrophaeus, and Candida albicans cells. PLA films with incorporated zinc oxide nanoparticles decreased the number of analyzed microorganisms. Accelerated UV aging had no negative effect on the activity of the film containing nano-ZnO against Gram-positive bacteria, but it influenced the activity against Gram-negative cells and C. albicans. Q-SUN irradiation decreased the antimicrobial effect of films with incorporated nanoparticles against B. cereus. UV-A and Q-UV irradiation did not influence the mechanical properties of PLA films containing incorporated ZnO nanoparticles.

The Influence of Accelerated UV-A and Q-SUN Irradiation on the Antimicrobial Properties of Coatings Containing ZnO Nanoparticles

The influence of accelerated UV-A and Q-SUN irradiation on the antimicrobial properties of coatings containing ZnO nanoparticles was investigated using a polyethylene (PE) film covering. The results of the study showed that Methyl Hydroxypropyl Celluloses (MHPC) coatings did not influence the growth of S. aureus, B. cereus, E. coli, P. aeruginosa or C. albicans cells. MHPC coatings containing ZnO nanoparticles inhibited the growth of bacterial strains and reduced the number of C. albicans strains. Accelerated Q-SUN and UV-A irradiation had no influence on the antimicrobial effect of nano ZnO coatings against S. aureus, B. cereus and E. coli. Q-SUN irradiation decreased the activity of MHPC coatings containing nanoparticles against P. aeruginosa and C. albicans. An FT-IR analysis clearly showed that ZnO nanoparticles shielded the MHPC coating during Q-SUN irradiation.