Dextran-Thyme Magnesium-Doped Hydroxyapatite Composite Antimicrobial Coatings

Abstract

The dextran-thyme magnesium-doped hydroxyapatite (10MgHAp-Dex-thyme) composite layers were prepared by a dip-coating procedure from stable suspensions and further analyzed for the first time. Different characterization techniques were employed to explore the physical-chemical features of the 10MgHAp-Dex-thyme suspensions and derived coatings. Information regarding the 10MgHAp-Dex-thyme suspensions was extracted on the basis of dynamic light scattering, zeta potential, and ultrasound measurements. The crystalline quality of the biocomposite powders—resulting after the centrifugation of suspensions—and the layers deposited on glass was assessed by X-ray diffraction in symmetric and grazing incidence geometries, respectively. The chemical structure and presence of functional groups were evaluated for both powder and coating by Fourier transform infrared spectroscopy in attenuated total reflectance mode. The extent of the antimicrobial effect range of the biocomposite suspensions and coatings was tested against different Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa) and fungus (Candida albicans) strains with promising results.

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

“…Moreover, the data suggested that the samples started inhibiting the CFU development for all tested strains from 8 h of incubation. These results are in good agreement with our previous studies regarding the influence of magnesium doped hydroxyapatite suspensions and magnesium doped hydroxyapatite enhanced with thyme essential oil in dextran matrix solutions and composite layers on the development of microbial biofilms [24,30]. The results obtained in our previous reported studies [30] suggested that the 10MgHAp-Dex-thyme suspensions presented strong antimicrobial properties even after 24 h in the case of Gram-negative P. aeruginosa and Gram-positive S. aureus bacterial strains.…”

“…Besides, in our anterior study [24], we certified with ultrasound measurements that a value of −17 ± 3.4 mV of ζ-potential obtained for 10MgHAp in water indicates that the suspension is unstable. Moreover, in recent studies on "Dextran-thyme coated magnesium doped hydroxyapatite layers on glass substrate" [30], ultrasound measurements confirmed that, for a value of −37 mV of the ζ-potential, the suspension has a good stability.…”

“…We found that the results achieved in the case of the MgHAp nanoparticle suspensions in conjunction with a dextran and thyme suspensions showed that the suspension presented better antimicrobial properties than the anterior reported studies on 10MgHAp (x Mg = 0.1) solutions tested on the same microbial strains at the same time intervals [24]. The increase of antimicrobial activity for MgHAp-based samples in conjunction with a dextran and thyme solution was attributed to both the essential oil and the solution stability increase [30].…”

“…Therefore, the use of magnesium ions as dopants for hydroxyapatite would constitute the development of a new material with significantly increased biological (osteogenic, osteoconductive, and antimicrobial) and mechanical properties, having explicit influences on the mineral metabolism, on the dissolution rate of the crystals, and also on the biodegradation process [28,29]. Additionally, due to the fact that magnesium has been reported to exhibit antimicrobial properties as well as enhanced osteogenic and angiogenetic properties, the use of magnesium doped hydroxyapatite has been also expanded to the obtaining of biological coatings for dental and orthopedic implants [16,30].…”

“…In our previous studies, we reported the stabilities of suspensions based on magnesium doped hydroxyapatite (MgHAp, x Mg = 0.1), magnesium doped hydroxyapatite in the presence of thyme essential oil, and MgHAp nanoparticle suspensions in conjunction with a dextran and thyme solution [30]. We found that the results achieved in the case of the MgHAp nanoparticle suspensions in conjunction with a dextran and thyme suspensions showed that the suspension presented better antimicrobial properties than the anterior reported studies on 10MgHAp (x Mg = 0.1) solutions tested on the same microbial strains at the same time intervals [24].…”