Project Summary
In this Project, using a series of protocols, hydroxyapatite powders of biological origin (MdHA), derived from salmon fish bones (FB) and seashells (SS), were doped in different concentrations (i.e., of 0.5; 1 and 2%, respectively) with lithium phosphate, magnesium fluoride, and silver. The as-obtained powders were pressed in the form of pellets. The simple and doped FB and SS structures were synthesized by Pulsed laser deposition technique onto medical-grade Ti substrates, which were chemically etched for optimum roughness. After their synthesis, all structures were subjected to thermal treatments, in a water-vapor atmosphere. Firstly, the PLD films were investigated from the mechanical point of view, by pull-out adherence tests. The obtained results indicated adherent coatings, with values more than three times higher than those imposed by the international standard (> 15 MPa).
Next, the obtained structures were characterized from morphological, compositional, and structural points of view. SEM investigations indicated films with rough morphologies, made up of particulates (tens to hundreds of nm), which were reported to be a friendly medium for grown cells. XRD and FT-IR analyses demonstrated the synthesis of coatings with varying degrees of crystallinity, generally influenced by the nature of the dopant/concentration and the source material. Contact angle measurements showed surfaces with strong hydrophilic behavior in the case of simple and doped FB and SS structures.
Considering the mechanical, morphological, structural, compositional, and wettability results, we decided to continue testing the biocompatibility and antimicrobial effect on FB and SS structures, simple and doped with an optimal concentration of 0.5%.
To evaluate the resistance to degradation and to explore the biomineralization capacity, the simple and doped FB and SS structures were subjected to preliminary tests in vitro, by immersion in physiological synthetic fluids. SEM images revealed important morphological changes of the investigated MdHA surfaces, after only 3 days of immersion in SBF, the particles on the surface being uniformly covered by acicular formations. FT-IR investigations indicated also a change in the spectrum, by narrowing the absorption bands, which was correlated with an improvement in the crystallinity of the investigated structures. The results of immersion in DMEM suggested that the simple and doped FB and SS structures were dominated by the CaP precipitation phenomenon, which was more pronounced in the case of films with a higher content of the bioactive HA phase, known to possess an improved biomineralization capacity.
The biocompatibility of simple and doped FB and SS structures was tested on three cell lines (osteoblasts, fibroblasts, and epithelial cells). The best cytocompatibility, characterized by increased values of the MTT test, correlated with low values of the LDH level, was obtained in the case of FB (osteoblast cells) and FB:LiP (fibroblast and epithelial cells) structures. None of the films was cytotoxic, as indicated by the LDH test. Also, compared to Ti, all simple and doped FB and SS structures, stimulated the secretion of alkaline phosphatase after 48 h of incubation.
The investigation of the antimicrobial activity of simple and doped FB and SS structures was carried out on standard strains (i.e., S. aureus, E. faecalis, E. coli, P. aeruginosa, and C. albicans). All tested materials showed antimicrobial activity, the most intense effect being observed in the case of FB:Ag structures.
The obtaining of competitive metal implant coatings, using renewable resources (i.e., HA derived from fish bones and seashells), with high functionality, represents an important step forward in the progress of biomedical field research, with an emphasis on the development of a new generation of orthopedic and dental implants that will contribute, among others, to reducing the population health problems.
Other results
(*) During Project implementation, the Project Leader and his team have established numerous scientific collaborations with prestigious Universities and Research Institutes, both from Romania and abroad: (i) "Stefan cel Mare" University, "Multifunctional advanced materials" laboratory, Suceava, Romania (Prof. Aurelian Rotaru, Prof. Diaconu Andrei); (ii) U.M.F., Faculty of Pharmacy, Craiova, Romania (Prof. Univ. Johny Neamtu); (iii) "Western Kentucky" University, SUA (Prof. Ali Oguz Er, Dr. Salizhan Kylychbekov); (iv) "Marmara" University, "Center for Nanotechnology & Biomaterials Applications and Research", Istanbul, Turkey (Prof. Faik N. Oktar, Prof. Oguzhan Gunduz); (v) "University of Technology Sydney", Faculty of Science, Australia (Prof. Ben-Nissan); (vi) "Arel" University, Istanbul, Turkey (Prof. Yesim Muge Sahin); (vii) "Technic" University, Istanbul, Turkey (Dr. Orhun Bastekeli). Within these collaborations, MdHA layers were synthesized by PLD and characterized using complementary techniques. The obtained results will represent the subjects of at least two manuscripts that will be sent for publication in ISI-rated journals.
(**) The project leader together with two team members and another two collaborators are are co-guest invited Editors of four Special Issues for International Journals: "Frontiers in Bioengineering and Biotechnology", "Coatings" (MDPI), and "Metals" (MDPI), with the titles "Calcium phosphates of synthetic and natural origin: current status and future challanges", "Synthetic and Biological-Derived Hydroxyapatite Implant Coatings", "Advances and challanges in Pulsed Laser Deposition for Complex Material Applications" and "Laser-Assisted Processing of Metals and Alloys". The thematics of these Special Issues are dedicated to (i) the obtaining and characterization techniques of synthetic and natural-origin hydroxyapatite, with various applications in the biomedical field, (ii) thin films and nanoparticles synthesis by Pulsed laser deposition, and (ii) laser processing of metallic materials.
More details on these projects can be obtained by accesing the links:
https://www.mdpi.com/journal/coatings/special_issues/hydroxyapatite,
https://www.mdpi.com/journal/coatings/special_issues/GRKZQJ0UI1,
and https://www.mdpi.com/journal/metals/special_issues/Laser_Processing_Metals.
(***) During the implementation period of the Project, the two PhD students successfully defended their theses (Oana Gherasim, "Multifunctional bionanostructured materials", Summa cum laude qualification, and Diana Chiobasu, „Medical devices made of Titanium alloys obtained by Addiditve fabrication techniques”), receiving the title of doctor.