Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca_10-xAg_x(PO₄)₆(OH)₂,x_Ag = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants ofa = b = 9.435 Å,c = 6.876 Å forx_Ag = 0.05,a = b = 9.443 Å,c = 6.875 Å forx_Ag = 0.2, anda = b = 9.445 Å,c = 6.877 Å forx_Ag = 0.3 are in good agreement with the standard ofa = b = 9.418 Å,c = 6.884 Å (space group P6₃/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity againstStaphylococcus aureus,Klebsiella pneumoniae,Providencia stuartii,Citrobacter freundiiandSerratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest againstS. aureus,K. pneumoniae, P. stuartii, andC. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity onP. stuartiiandC. freundii. The absorbance values measured at 490 nm of theP. stuartiiandC. freundiiin the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (x_Ag = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase ofx_Agin the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii).

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 (D_HYD). 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.

Obtaining nanoscale materials has allowed for the miniaturization of components, which has led to the possibility of achieving more efficient devices with faster functions and much lower costs. While hydroxyapatite [HAp, Ca₁₀(PO₄)₆(OH)₂] is considered the most widely used material for medical applications in orthopedics, dentistry, and general surgery, the magnesium (Mg) is viewed as a promising biodegradable and biocompatible implant material. Furthermore, Mg is regarded as a strong candidate for developing medical implants due to its biocompatibility and antimicrobial properties against gram-positive and gram-negative bacteria. For this study, magnesium-doped hydroxyapatite (Ca_10−xMg_x (PO₄)₆ (OH)₂, x_Mg = 0.1), 10MgHAp, suspensions were successfully obtained by an adapted and simple chemical co-precipitation method. The information regarding the stability of the nanosized 10MgHAp particles suspension obtained by ζ-potential analysis were confirmed for the first time by a non-destructive ultrasound-based technique. Structural and morphological studies of synthesized 10MgHAp were conducted by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode and scanning electron microscopy (SEM). The XRD analysis of the 10MgHAp samples confirmed that a single crystalline phase associated to HAp with an average grain size about 93.3 nm was obtained. The FTIR-ATR spectra revealed that the 10MgHAp sample presented broader IR bands with less visible peaks when compared to a well-crystallized pure HAp. The SEM results evidenced uniform MgHAp nanoparticles with spherical shape. The antimicrobial activity of the 10MgHAp suspension against gram-positive strains (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212), gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853), as well as a fungal strain (Candida albicans ATCC 90029) were evaluated.

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 P6_3/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 (x_Zn = 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.

The present work was focused on the synthesis and characterization of hydroxyapatite doped with low concentrations of zinc (Zn:HAp) (0.01 < x_Zn < 0.05). The incorporation of low concentrations of Zn²⁺ ions in the hydroxyapatite (HAp) structure was achieved by co-precipitation method. The physico-chemical properties of the samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), zeta-potential, and DLS and N₂-BET measurements. The results obtained by XRD and FTIR studies demonstrated that doping hydroxyapatite with low concentrations of zinc leads to the formation of a hexagonal structure with lattice parameters characteristic to hydroxyapatite. The XRD studies have also shown that the crystallite size and lattice parameters of the unit cell depend on the substitutions of Ca²⁺ with Zn²⁺ in the apatitic structure. Moreover, the FTIR analysis revealed that the water content increases with the increase of zinc concentration. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) and XPS analyses showed that the elements Ca, P, O, and Zn were found in all the Zn:HAp samples suggesting that the synthesized materials were zinc doped hydroxyapatite, Ca_10−xZn_x(PO₄)₆(OH), with 0.01 ≤ x_Zn ≤ 0.05. Antimicrobial assays on Staphylococcus aureus and Escherichia coli bacterial strains and HepG2 cell viability assay were carried out.

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.