Morphological and antibacterial effects of silver,magnesium,silicon and strontium modified calcium phosphate bone cements prepared by the sol

Abstract

In this study, the sol–gel method was used to add MgO and SrBr₂ to biografts containing Ca(NO₃)₂·4H₂O, SiO₂, P₂O₅, H₃BO₃ and AgNO₃. In addition, urea (15–35% by weight) was added to these biografts in different ratios. FTIR, XRD and SEM–EDX analyses were performed in order to observe the morphological effects. Antibacterial tests were carried out using S.aureus and E.coli bacteria. As a result of FTIR analysis, it was observed that H–OH, CO³⁻, , , Si–O and Si–O–Si compound structures were formed in the biografts. XRD analysis was found that HA (Hydroxyapatite), β-TCP, CaSiO₃, CaMgSi₂O₆, Ca₃MgSi₂O₈, CaMgSi₂O₆ and Mg₁₇Sr₂ compound structures were formed. Antibacterial analysis with E. coli showed that all biografts except the one that contained the highest amount of urea (35% by weight) yielded colony counting values close to the negative control. For S. aureus, the opposite result was observed.

Keywords

Bone grafts antibacterial effects

Introduction

Bioceramics play a large role in the repair of bone damage and infections in bone tissue engineering. Biosilicates, one of the well-known bioceramic materials, minimise the organ loss. They provide a positive human body response against negative immune. In addition, bioceramics, used as filling material, have a great effect in the repair of osteoporosis and periodontal diseases in bones and teeth [1].

Elements, such as Ca, Mg and Si, in the biosilicate structure play a vital role in bone formation in the body [2]. While Ca is the basic constituent element of the bones, teeth and skull, magnesium is essential for regulating bone growth, maintenance and repair [3,4]. Silicon, on the other hand, is an essential element for the development of the skeleton, and its deficiency causes skull deformation [3,4]. Silicate-based bioceramics such as wollastonite (CaSiO₃) [5,6], dicalcium silicate (Ca₂SiO₄) [7], bredigite (Ca₇MgSi₄O₁₆) [8] and akermanite (Ca₂MgSi₂O₇) [9], in particular, show excellent in vitro bioactivity, mechanical properties and biocompatibility.

Strontium (Sr) is a substitute material for bone in case of bone damage. Considering the beneficial effects of Sr in both normal and diseased bone tissues, strontium ranelate medication in newly developed osteoporosis drugs has the effect of reducing the risk of vertebral and hip fractures in osteoporosis in postmenopausal women [10 -12]. Furthermore, Sr-containing silicates such as Sr-doped CaSiO₃ [13], strontium silicate (SrSiO₃) [14] and Sr-containing bioactive glasses [15] show a stimulatory effect in osteogenesis. The changes in the structure of bioceramics are aimed at improving the performance of the biomaterials used in place of bone. Sr ions used in place of Ca in the calcium phosphate lattice structure are of great importance since they play an important role in the mineralisation of tissues [16]. Sr has a chemical structure similar to calcium and is found in bone mineral structures, especially in high metabolic turnover regions [17,18]. When the effects of Mg and Sr added to CaCO₃ and (NH₄)₂HPO₄ compounds were examined, it was found that it increased the biocompatibility of the Ca₂P₂O₇ (CPP) ceramics obtained and positively affected the phase transformation behaviour when sintered [19].

Although it has excellent antibacterial properties, Ag concentrations tend to cause very low toxicity in human cells beyond a certain threshold [20]. The Sr element present in bones has been shown to be an effective anti-osteoporosis drug due to its antiresorptive and bone-forming effect in in vitro and in vivo experiments [21 -24]. Therefore, Sr is a second promising chemical element to offset the negative effect of Ag [25]. In addition, Sr/Ag-containing CaP coatings show good biological activity and optimal antimicrobial properties [25].

Experimental procedure

Materials and production processes

In this study, biografts with weight percentage values given in Table 1 were produced by the sol–gel method. All materials except P₂O₅ were dissolved in ethanol and stirred with a magnetic stirrer at 400 rpm for 1 h at room temperature. This solution was then homogenised to achieve homogenous dispersion and gelation of the particles by stirring in an ultrasonic homogeniser at 37°C for 30 min at 35% amplitude. The P₂O₅ compound was dissolved in distilled water in a separate beaker and then added to the homogeniser to obtain a gel structure. After the pH values of all biografts were measured to be below 5, the pH was adjusted to 7.5 using an NaOH solution without changing the white gel structure of the solutions. The biografts were aged for 12 h at room temperature in standard atmosphere and then dried in an ash oven at 120°C for 24 h at standard atmosphere. After drying, the biografts were subjected to a sintering process where the temperature was increased to 1150°C at 5°C min⁻¹, kept at 1150°C for 2.5 h and then decreased to room temperature at 5°C min⁻¹.

Table 1

The weight percentage amounts of materials produced by the sol–gel method.

Materials	Ca(NO₃)₂·4H₂O	SiO₂	P₂O₅	H₃BO₃	MgO	AgNO₃	SrBr₂	Urea
CaSiAg	45	40	5	5	–	5	–	–
CaMgSr	35	30	5	5	5	5	15	–
CaMgSrU1	30	20	5	5	5	5	15	15
CaMgSrU2	20	20	5	5	5	5	15	25
CaMgSrU3	20	10	5	5	5	5	15	35

Characterisation

FTIR, XRD and SEM–EDX analyses were performed to examine the microstructure and chemical properties of all biografts that were produced by the sol–gel method. XRD analysis was conducted using the specimen holder and a Bruker D8 Advance (λ = 1.5406 Å) marked via fully automated diffractometer. The diagrams were produced by conducting the measurements recorded in the range of 2-theta = 10–85° at a scanning rate of 2°/min and 1 s at a constant time gap. FTIR (ALTI Unicam WATTSON 1000) analysis was performed to determine the structures of the synthesised samples. Fourier transform infrared spectroscopy operating at a wavelength from 650 to 4000 cm⁻¹ was used for FTIR analysis, and scanning electron microscopy or SEM (JEOL JSM-7001F) was used to investigate the morphological properties.

Testing the antibacterial effect of the composites

Bacterial strains

Two common bacteria (Escherichia coli and Staphylococcus aureus) were used to determine the antibacterial effects of the synthesised complexes. The in vitro antibacterial activity of complexes against Gram-negative E. coli (JM 103) and Gram-positive S. aureus (ATCC 25923) was evaluated by the plate-counting method. These bacteria were obtained from Mustafa Kemal University and tested with 10 different antibiotics (amikacin, aztreonam, cefazolin, cefoxitin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, colistin and gentamicin) in order to determine any resistance to antibiotics. It was found that E. coli and S. aureus had no resistance to any of the tested antibiotics (data not shown).

Colony counting

One colony of each bacteria was inoculated into 10 mL of Tryptic Soy Broth (TSB) and incubated overnight at 37°C. Tryptic Soy Agar (TSA) without any supplement was used for colony counting in order to determine the number of colony-forming units (CFU) within the stock solution. Fifty µL of each bacterium grown overnight was spread onto the TSA medium (3 plates for each bacterium) and incubated overnight at 37°C. The number of colonies was counted and divided into 3 and multiplied by 20 (CFU mL⁻¹ = (total number of colony/3) × 20) to assess the final number of CFU per mL. This method was also used to determine the effects of the synthesised complexes.

Determination of the antibacterial effects of the complexes

To test the antibacterial effects of the complexes, four concentrations (0.5, 1, 5 and 10 mg mL⁻¹) of each complex were prepared in TSA. TSA without any supplement was used as the negative control (NC). All concentrations were studied in triplicate. In this part of the study, 50 µL of each overnight grown bacterium was also spread onto TSA mediums that contained the 0.5, 1, 5 and 10 mg mL⁻¹ of complexes and incubated overnight at 37°C. After the incubation, colonies were counted and the number of viable cells was estimated as CFU mL⁻¹. Any significant reduction in the CFUs indicated the antibacterial effects of the complex dose.

Results

Fourier transform infrared spectroscopy

The results of the FTIR analysis of the biografts produced by the sol–gel method are given in Figures 1–3 over wavelengths from 650 to 3000 cm⁻¹. As a result of the investigations, while it was observed that all biografts yielded C = O, Si–O–Si and PO₄³-containing compounds, it was determined that SrBr₂, MgO and urea-containing biografts yielded H–OH, , Si–O and Mg–O compound structures as well.

The FTIR analysis of the CaSiAg biograft containing Ca(NO₃)₂·4H₂O, SiO₂, P₂O₅, H₃BO₃ and AgNO₃ is given in Figure 1. From the FTIR analysis, it is observed that the CaSiAg graft has a peak at 2161.5 cm⁻¹, a Si–O–Si peak at 1401.8 and 1075.3 cm⁻¹, and compound structures with peaks in a range from 989.62 to 702.76 cm⁻¹.

Figure 3 gives the FTIR analysis distribution of biografts (CaMgSr, CaMgSrU1, CaMgSrU2 and CaMgSrU3) containing 15% by weight of SrBr₂ and different ratios of urea (15–35% by weight). In Figure 2, it is observed that the CaMgSr biograft yields H–OH, and Si–O compounds, which is different from the CaSiAg biograft. The biografts in Figures 2 and 3 show H–OH in a range from 3661.3 to 2898.6 cm⁻¹, in the range from 1954.5–2163.5 cm⁻¹, Si–O–Si from 1473.8 to –1068 cm⁻¹, and also peaks at 909.34–704.92 cm⁻¹. Furthermore, it was determined in Figures 1 and 2 that the addition of SrBr₂, MgO and urea reduced the peak intensities.

X-ray diffraction analysis

The XRD analysis results of the CaSiAg and CaMgSr biografts are given in Figure 3(a,b). As a result of the investigations, it was observed from the XRD analysis given in Figure 3(a) that the CaSiAg biograft has a crystalline structure and contains HA, β-TCP and CaSiO₃ compounds. Furthermore, unlike the CaSiAg biograft, the CaMgSr biograft with SrBr₂ and MgO content contains akermanite (CaMgSi₂O₆), merwinite (Ca₃MgSi₂O₈), diopside (CaMgSi₂O₆) and Mg₁₇Sr₂ compounds (Figure 3(b)). It was observed from the XRD analysis of the CaMgSr biograft in Figure 4(b) that it has a crystal structure, due to its high peak intensity. However, since the peak intensity of the CaMgSr biograft is lower than that of the CaSiAg biograft, it was also seen in Figure 4(a,b) that its crystallinity is lower than that of the CaSiAg biograft.

According to the XRD analysis results of the CaMgSrU1, CaMgSrU2 and CaMgSrU3 biografts, all biografts contain akermanite (CaMgSi₂O₆), merwinite (Ca₃MgSi₂O₈), diopside (CaMgSi₂O₆) and Mg₁₇Sr₂ compounds (Figure 5(a–c)). When the crystallites were examined by considering their peak intensities, it was observed that all biografts had a crystalline structure. However, it was determined in Figure 5(a–c) that there was not much change in crystallinity as the amount of urea increased.

Scanning electron microscopy–energy-dispersive X-ray spectroscopy

The SEM–EDX analysis results of the CaSiAg biograft are given in Figure 6(a–c). As seen in the SEM image at 1000× magnification, the CaSiAg biograft produced an irregular grain distribution for the sol–gel production method. In addition, it was determined that the grain size distribution of the CaSiAg biograft was different, and between the large grains, regions of agglomerated small-grained structures had formed (Figure 6(a)). Along with the porous structure between the grains, the formation of white spherical-shaped structures with high Ag content on top of the grains was also seen in the SEM images, and the corresponding EDX analysis results are given in Figure 6(a,b), respectively. In the EDX results given in Figure 6(b,c), it was observed that generally, CaSiAg formed a chemical structure containing Ca, Si, P, Ag, N and O elements. The white spherical structures formed on the surface were shown to be generated from the phases with high Ag content (Figure 6(c)).

SEM images of the CaMgSr, CaMgSrU1 and CaMgSrU2 biografts at 1000× magnification are given in Figure 7(a–c). As a result of the SEM examination, it was determined that the grain size of the CaMgSr biograft was small, but the grains were distributed in the form of agglomerates (Figure 6(a)). Urea which melts at 133°C was used to alter the graft structure by forming cavities instead in the CaMgSrU1 and CaMgSrU2 and CaMgSrU3 biografts at high sintering temperatures. Therefore, it was observed in Figure 7(b,c) that a porous structure with different sizes was formed with liquid phase sintering in the urea-containing (15–25% by weight) CaMgSrU1 and CaMgSrU2 biografts. In addition, it was determined that as the amount of urea increased, the liquid phase sintering and pore sizes increased.

SEM–EDX results of the CaMgSrU3 biograft are given in Figure 8(a–c). A heterogeneous grain and pore distribution were observed in the SEM image of the CaMgSrU3 biograft. In addition, it was determined that the grain and pore size were variable, and the formation of white spherical structures was observed on the surface. As a result of the general EDX analysis, it was determined that Ca, Si, Mg, Ag, Sr and O-containing phases were formed throughout the biograft, whereas phases high in Ag levels were found to form in the white spherical structures (Figure 8(b,c)).

Antibacterial analysis

Antibacterial analyses on CaSiAg, CaMgSr, CaMgSrU1, CaMgSrU2 and CaMgSrU3 biografts were performed using E. coli and S. aureus bacteria in order to determine the effect of differences in concentration. An 0.5–10 mg mL⁻¹ amount of biograft was used during the analysis. Antibacterial analyses performed using E. coli are given in Figure 8, while analyses performed with S. aureus are given in Figure 9.

As a result of the antibacterial analysis performed with E. coli, it was observed in Figure 9 that all biografts gave colony counting values higher than or equal to the NC group, except for the CaMgSrU3 biograft, which had the highest concentration of urea at a concentration of 0.5 mg mL⁻¹. However, at a concentration of 0.5 mg mL⁻¹, the CaMgSrU3 biograft gave results close to the NC colony counting values as given in Figure 9. At a concentration of 1 mg mL⁻¹, the colony counting values were found to be increased for CaSiAg, CaMgSr and CaMgSrU1, whereas it was determined to be zero for CaMgSrU2 and CaMgSrU3 (Figure 9). It was observed that the colony counting values for CaSiAg, CaMgSr and CaMgSrU1 biografts at a concentration of 5–10 mg mL⁻¹ were reduced with respect to the values at a concentration of 0.5–1 mg mL⁻¹, while it was observed to be zero at a concentration of 1 mg mL⁻¹ for the CaMgSrU2 and CaMgSrU3 biografts (Figure 9). Thus, antibacterial test result with E. coli, all biografts except CaMgSrU2 and CaMgSrU3 gave the best colony counting value at a concentration of 1 mg mL⁻¹. CaMgSrU3 biograft with wt-% 35 urea content showed the highest colony counting value at a concentration of 0.5 mg mL⁻¹.

It was observed in Figure 10 that all biografts showed higher or close colony counting values to the NC group as a result of the antibacterial analysis performed using S. aureus at a concentration of 0.5 mg mL⁻¹. It was also determined that the highest colony counting value was obtained from the CaMgSrU3 biograft at a concentration of 0.5 mg mL⁻¹ (Figure 10). In the concentration range from 1 to 10 mg mL⁻¹, the colony counting values of CaSiAg, CaMgSr and CaMgSrU1 biografts were close to the NC. However, as the concentration amount increased, a decrease in these amounts occurred (Figure 10).

Discussion

Similar to HA, calcium phosphate salts – the main constituents of bone tissue and tooth – have excellent bioactivity, biocompatibility and osteoconductivity; thus, are widely used for biomedical applications [25]. In recent years, silicium-containing calcium phosphate compounds produced by the sol–gel production method – used for bone grafts – have a wide area of application [26,27]. Silicium-containing compounds affect the density of HA and also inhibit its grain growth [25,28,29]. Strontium or magnesium-containing compounds reduce bone loss and degradation while increasing bone formation and the mechanical properties of bone grafts [30 -32].

In this study, the effect of adding SrBr₂, MgO and urea to Ca(NO₃)₂·4H₂O, SiO₂, P₂O₅, H₃BO₃ and AgNO₃-containing biografts was investigated. Figures 1 and 3 give the FTIR analysis results from all biografts. peaks obtained in the range from 947 to 1118 cm⁻¹ corresponded to the compound obtained from β-TCP, the thermal decomposition phase of high-temperature HA [33]. The Si–O–Si structure obtained in the peak range of 685–800 cm⁻¹ indicated the formation of an amorphous silica phase in the silicon-containing calcium phosphate content [34 -37] and the possible formation of the Si–O stretching mode at 852–935 cm⁻¹ [38]. Thus, it was observed from the FTIR analysis that the CaSiAg graft yielded C = O, Si–O–Si, compound structures, unlike the CaSiAg biografts, SrBr₂, MgO and urea-containing biografts (CaMgSr, CaMgSrU1, CaMgSrU2 and CaMgSrU3) that yielded C = O, Si–O–Si and compound structures together with H–OH and peaks. Also, in Figures 1–3, it was determined that the peak intensity decreased by adding SrBr₂ and urea. The decrease in peak intensity indicated that the biografts were transformed from crystalline to amorphous structures by the addition of SrBr₂, MgO and urea. This reduction in peak intensities is due to the presence of metal ions which can occur during dehydoxylation [39].

When the bioactivity effects of synthesised eggshell-containing materials with calcium, magnesium, silicate and CaCO₃ as the main constituent structure (900°C, 1200°C) were evaluated at different sintering temperatures, it was determined that the biografts sintered above 900°C form the akermanite (CaMgSi₂O₆) basic phase together with merwinite (Ca₃MgSi₂O₈) and diopside (CaMgSi₂O₆) phases [38]. When the results of the XRD analysis of the CaSiAg and CaMgSr biografts given in Figure 4(a,b) were examined in this study, it was observed that the CaSiAg biograft contained HA, β-TCP and CaSiO₃ compounds, and the CaMgSr biograft produced akermanite (CaMgSi₂O₆), merwinite (Ca₃MgSi₂O₈) and diopside (CaMgSi₂O₆) phases. In addition, CaMgSrU1, CaMgSrU2 and CaMgSrU3 biografts formed Mg₁₇Sr₂ compounds different to the CaSiAg and CaMgSr biografts (Figure 5(a–c)). When the peak intensities were compared, it was observed that in addition to MgO and SrBr₂, urea also decreased the peak intensity of the CaSiAg biograft (Figures 4(a,b) and 5(a–c)). However, it was determined that the amount of urea did not affect the peak intensity much and, as the amount of urea increased, the peak intensities results were similar to each other (Figure 5(a–c)).

When SEM images of all biografts were examined, it was observed that CaSiAg gave a heterogeneous grain size distribution, and it was determined that white spherical structures with a high Ag content were formed on the surface (Figure 6(a)). When SrBr₂ and MgO were added to the biograft, it was observed in Figure 7(a) that grain sizes were reduced, agglomeration occurred and pore sizes between the grains increased. When the effect of the amount of urea on the biografts was examined, it was found that as the amount of urea increases, a liquid phase structure and pore structures of different sizes were formed, and the amount of pores increased (Figures 7(b,c) and 8(a)). In addition, it was observed that white spherical grain structures with high Ag content were formed on CaMgSrU1 and CaMgSrU3 biograft surfaces and the CaMgSrU3 biograft containing 35% by weight of urea had fewer of these spherical structures at smaller sizes (Figures 7(b) and 8(a))

Thus, it was determined that the addition of SrBr₂ and MgO to the biograft reduced the grain size. In addition, it was observed that urea caused the formation of a significant porous structure between the grains in the biografts and, as the amount of urea increased, the amount of different sized pores increased. From the EDX analysis results, it was determined that the CaSiAg biograft consisted of compounds containing Ca, Si, P, Ag, N and O (Figure 6(c)). In Figure 8(c), it was determined that the CaMgSrU3 biograft contained Mg and Sr-containing phases in addition to Ca, Si, Ag and O.

It has been determined that the carbonate and/or silicon added to the hydroxyapatite decreases the decomposition temperature together with its feature close to natural bone [40 -43]. In addition, adding Sr and Mg–Sr compounds to CaP compounds exhibited good corrosion resistance, improved biocompatibility/bioactivity and supported new bone formation [44].

According to Figures 9 and 10, the growth characteristics of both E. coli and S. aureus presented similar susceptibility behaviour in the same complexes. Complex type CaSiAg, CaMgSr and CaMgSrU1 did not have any effect on growth of either bacteria at any dose in comparison to the NC group.

Silver is known to be among alternative inorganic materials that have antibacterial properties [45 -47]. The results of the current study suggested that increases in the amount of AgNO₃ in all biografts inhibited bacterial growth. This result indicated that silver ions may have antibacterial effects on some bacteria. The results of this study are in agreement with Sun et al. [48].

In this study, the growth-inhibiting doses of different complexes were determined. However, further antimicrobial studies, such as determining the minimum inhibitory concentration (MIC) – according to Clinical & Laboratory Standards Institute (CLSI) standards – are required in order to ensure the lowest MIC of all synthesised complexes.

Conclusions

According to the results of the FTIR analysis of all biografts, it was observed that the CaSiAg biograft formed structures containing Si–O–Si, Si–O and , whereas it was determined that biografts containing MgO, SrBr₂ and urea formed similar structures together with phases containing H–OH, , and Si–O–Si compounds.

From the results of the FTIR analysis, it was determined that peak intensity decreased and amorphous structure increased with the addition of MgO, SrBr₂ and urea to the CaSiAg biograft. Thereby, the lowest peak intensity and the highest amorphous structure were observed in the CaMgSrU3 biograft because of dehydoxylation, which occurred due to the addition of metal ions to the biografts.

From the XRD analysis results, it was determined that the CaSiAg biograft contained HA, β-TCP and CaSiO₃ compounds, and the CaMgSr, CaMgSrU1, CaMgSrU2 and CaMgSrU3 biografts contained akermanite (CaMgSi₂O₆), merwinite (Ca₃MgSi₂O₈), diopside (CaMgSi₂O₆) and Mg₁₇Sr₂ compounds.

When the effect of SrBr₂ and urea compounds on the XRD peak intensity of the biografts was evaluated, it was observed that both compounds decreased the peak intensity. It was observed that SrBr₂ and urea significantly reduced the crystallinity.

It was determined from the SEM images that SrBr₂ and MgO reduced the grain size of the biograft, urea led to the formation of a porous structure in the biografts and, as the amount of urea increased, a larger quantity of pores formed in different sizes. From the EDX results, it was observed that the CaSiAg biograft contained Ca, Ag, Si, P and O whereas the other biografts contained Sr, Mg and C.

According to the antibacterial analysis performed with E. coli using a biograft concentration of 0.5–10 mg mL⁻¹, it was observed that colony counting values of all biografts except CaMgSrU3 gave results similar to the NC values. It was determined that the CaMgSrU3 biograft did not produce any value at any concentration except 0.5 mg mL⁻¹. When the highest colony counting value was evaluated in all concentrations of all biografts, it was determined that the CaMgSrU2 biograft gave the highest value at a concentration of 0.5 mg mL⁻¹.

In the antibacterial analysis performed with S. aureus, it was observed that the highest colony counting value was produced by the CaMgSrU3 biograft at a concentration of 0.5 mg mL⁻¹; however, concentrations of 1–10 mg mL⁻¹ did not give any colony counting values for the CaMgSrU3 biograft.

In the antibacterial tests performed in the 0.5–10 mg mL⁻¹ biograft concentration range, it was observed that the addition of SrBr₂ and MgO to the biografts containing Ca(NO₃)₂·4H₂O, SiO₂, P₂O₅, H₃BO₃ and AgNO₃ increased the colony counting values at biograft concentrations of 5–10 mg mL⁻¹ and exhibited good antibacterial properties.

Footnotes

Disclosure statement

No potential conflict of interest was reported by the author(s).

References

Rahaman

, Day

, Bal

, Bioactive glass in tissue engineering. Acta Biomater. 2011;7(6):2355–2373.

Choudhary

, Koppala

, Swamiappan

Bioactivity studies of calcium magnesium silicate prepared from eggshell waste by sol–gel combustion synthesis. J Asian Ceramic Soc. 2015;3(2):173–177.

Liu

CC.

Magnesium directly stimulates osteoblast proliferation. J. Bone Miner. Res. 1988;3:104.

Carlisle

EM.

Biochemical and morphological changes associated with long bone abnormalities in silicon deficiency. J Nutr. 1980;110(5):1046–1056.

Deaza

, Guitian

, Deaza

Bioactivity of wollastonite ceramics: in vitro evaluation. Scr. Metall. Mater. 1994;31:1001–1005.

Lin

, Zhai

, Ni

, Study of the mechanical property and in vitro biocompatibility of CaSiO3 ceramics. Ceram Int. 2005;31:323–326.

Gou

, Chang

, Zhai

WY.

Preparation and characterization of novel bioactive dicalcium silicate ceramics. J Eur Ceram Soc. 2005;25:1507–1514.

, Chang

, Wang

, Preparation and characteristics of a calcium magnesium silicate (bredigite) bioactive ceramic. Biomaterials. 2005;26:2925–2931.

, Chang

A novel akermanite bioceramic: preparation and characteristics. J. Biomater. Appl. 2006;21:119–129.

10.

Meunier

, Roux

, Seeman

, The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. N. Engl. J. Med. 2004;350:459–468.

11.

Fardellone

, Roux

, Fechtenbaum

, Strontium ranelate reduces the risk of vertebral fractures in osteoporotic postmenopausal women whatever the baseline vertebral fracture status. Bone. 2005;36:403.

12.

Reginster

, Seeman

, De Vernejoul

, Strontium ranelate reduces the risk of nonvertebral fractures in postmenopausal women with osteoporosis: treatment of peripheral osteoporosis (TROPOS) study. J. Clin. Endocrinol. Metab. 2005;90:2816–2822.

13.

, Ramaswamy

, Kwik

, The effect of strontium incorporation into CaSiO₃ ceramics on their physical and biological properties. Biomaterials. 2007;28:3171–3181.

14.

Zhang

, Zhai

, Lin

, Synthesis, in vitro hydroxyapatite forming ability, and cytocompatibility of strontium silicate powders. J Biomed Mater Res B: Appl Biomater. 2010;93B:252–257.

15.

Gentleman

, Fredholm

, Jell

, The effects of strontium-substituted bioactive glasses on osteoblasts and osteoclasts in vitro. Biomaterials. 2010;31:3949–3956.

16.

Kannan

, Goetz-Neunhoeffer

, Neubauer

, Synthesis and structural characterization of strontium – and magnesium-co-substituted β-tricalcium phosphate. Acta Biomater. 2010;6(2):571–576.

17.

Boanini

, Gazzano

, Bigi

Ionic substitutions in calcium phosphates synthesized at low temperature. Acta Biomater. 2010;6(6):1882–1894.

18.

Moreira

APD

, Sader

, Soares

GDDA

, Strontium incorporation on microspheres of alginate/β-tricalcium phosphate as delivery matrices. Mater Res. 2014;17(4):967–973.

19.

Kim

, An

, Cho

IS.

Effects of Mg and Sr co-addition on the densification and biocompatible properties of calcium pyrophosphate. Ceram Int. 2018;44(8):9689–9695.

20.

Gopi

, Shinyjoy

, Kavitha

Synthesis and spectral characterization of silver/magnesium co-substituted hydroxyapatite for biomedical applications. Spectrochim Acta A. 2014;127:286–291.

21.

Marie

, Ammann

, Boivin

, Mechanisms of action and therapeutic potential of strontium in bone. Calcif Tissue Int. 2001;69:121–129.

22.

Schumacher

, Lode

, Helth

, A novel strontium(II)-modified calcium phosphate bone cement stimulates human-bone-marrow-derived mesenchymal stem cell proliferation and osteogenic differentiation in vitro. Acta Biomater. 2013;9:9547–9557.

23.

Wong

, Wong

, Liu

, Mechanical properties and in vitro response of strontium-containing hydroxyapatite/polyetheretherketone composites. Biomaterials. 2009;30:3810–3817.

24.

Zhou

, Li

, Lu

, Regulation of osteoblast proliferation and differentiation by interrod spacing of Sr-HA nanorods on microporous titania coatings. ACS Appl Mater Interfaces. 2013;5:5358–5365.

25.

Geng

, Wang

, Zhuo

, Incorporation of silver and strontium in hydroxyapatite coating on titanium surface for enhanced antibacterial and biological properties. Mater Sci Eng C. 2017;71:852–861.

26.

Ravarian

, Moztarzadeh

, Solati-Hashjin

, Synthesis, characterization and bioactivity investigation of bioglass/hydroxyapatite composite. Ceram Int. 2010;36(1):291–297.

27.

Duan

, Congqin

, Tingting

Cytocompatibility and osteogenic activity of a novel calcium phosphate silicate bioceramic: silicocarnotite. J Biomed Mater Res A. 2013;101(7):1955–1961.

28.

Bang

, Kunio

, Othman

Effect of silicon and heat-treatment temperature on the morphology and mechanical properties of silicon-substituted hydroxyapatite. Ceram Int. 2011;37(8):3637–3642.

29.

Palard

, Combes

, Champion

, Effect of silicon content on the sintering and biological behaviour of Ca10 (PO4) 6-x (SiO4) x (OH) 2-x ceramics. Acta Biomater. 2009;5(4):1223–1232.

30.

Oudadesse

, Dietrich

, Bui

, Enhancement of cells proliferation and control of bioactivity of strontium doped glass. Appl Surf Sci. 2011;257(20):8587–8593.

31.

Guo

, Xu

, Zhao

, Development of a strontium-containing hydroxyapatite bone cement. Biomaterials. 2005;26(19):4073–4083.

32.

Pijocha

, Zima

, Paszkiewicz

, Physicochemical properties of the novel biphasic hydroxyapatite-magnesium phosphate biomaterial. Acta Bioeng Biomech. 2013;15(3):53–63.

33.

Dan-Jae

, Ming-Tzu

, Tzong-Ming

, In vitro antibacterial activity and cytocompatibility of bismuth doped micro-arc oxidized titanium. J Biomater Appl. 2013;27(5):553–563.

34.

Galeener

FL.

Band limits and the vibrational spectra of tetrahedral glasses. Phys Rev B. 1979;19(8):4292.

35.

Reid

W J

, Loughlin

, Sayer

, Synthesis and characterization of single-phase silicon-substituted α-tricalcium phosphate. Biomaterials. 2006;27(15):2916–2925.

36.

Vandiver

, Dean

, Patel

, Silicon addition to hydroxyapatite increases nanoscale electrostatic, van der Waals, and adhesive interactions. J Biomed Mater Res A. 2006;78(2):352–363.

37.

Marchat

, Zymelka

, Coelho

, Accurate characterization of pure silicon-substituted hydroxyapatite powders synthesized by a new precipitation route. Acta Biomater. 2013;9(6):6992–7004.

38.

Choudhary

, Sivasankar

, Sasikumar

Bioactivity studies of calcium magnesium silicate prepared from eggshell waste by sol–gel combustion synthesis. J Asian Ceramic Soc. 2015;3(2):173–177.

39.

Farzadi

, Bakhshi

, Solati-Hashjin

, Magnesium incorporated hydroxyapatite: synthesis and structural properties characterization. Ceram Int. 2014;40(4):6021–6029.

40.

Palard

, Champion

, Foucaud

Synthesis of silicated hydroxyapatite Ca10(PO4)6-x(SiO4)x(OH)2-x,”. J Solid State Chem. 2008;181(8):1950–1960.

41.

Lafon

, Champion

, Bernache-Assollant

Processing of AB-type carbonated hydroxyapatite Ca10-(PO₄)6-x(CO₃)x(OH)₂-x-2y(CO₃)y ceramics with controlled composition. J Eur Ceram Soc. 2008;28(1):139–147.

42.

Vallet-Regi

, Arcos

Silicon substituted hydroxyapatites. A method to upgrade calciumphosphate based implants. J Mater Chem. 2005;15(15):1509–1516.

43.

Bang

, Long

, Othman

Carbonate hydroxyapatite and silicon-substituted carbonate hydroxyapatite: synthesis, mechanical properties, and solubility evaluations. Sci World J. 2014; doi:10.1155/2014/969876.

44.

Junjie

, Wan

, Sun

, Fabrication and evaluation of a bioactive Sr–Ca–P contained micro-arc oxidation coating on magnesium strontium alloy for bone repair application. J Mater Sci Technol. 2016;32(3):233–244.

45.

Mahmoudi

, Serpooshan

Silver-coated engineered magnetic nanoparticles are promising for the success in the fight against antibacterial resistance threat. ACS Nano. 2012;6:2656–2664.

46.

Nel

, Mädler

, Velegol

, Understanding biophysicochemical interactions at the nano-bio interface. Nat. Mater. 2009;8:543–557.

47.

Stevanovic

, Uskokovic

, Filipovic

, Composite PLGA/AgNpPGA/AscH nanospheres with combined osteoinductive, antioxidative, and antimicrobial activities. ACS Appl Mater Interfaces. 2013;5:9034–9042.

48.

Sun

, Huang

, Zhou

HJ.

Synthesis, characterization and antibacterial activity of a new silver(I) complex based on a flexible dicarboxylic acid ligand. J Mol Struct. 2016;1107:116–120.

Morphological and antibacterial effects of silver,magnesium,silicon and strontium modified calcium phosphate bone cements prepared by the sol–gel method

Abstract

Keywords

Introduction

Experimental procedure

Materials and production processes

Characterisation

Testing the antibacterial effect of the composites

Bacterial strains

Colony counting

Determination of the antibacterial effects of the complexes

Results

Fourier transform infrared spectroscopy

X-ray diffraction analysis

Scanning electron microscopy–energy-dispersive X-ray spectroscopy

Antibacterial analysis

Discussion

Conclusions

Footnotes

References