SR Release Research Articles

Strontium doped electrospinning fiber membrane with antibacterial and osteogenic properties prepared by pulse electrochemical method

• Composite fibers were prepared by electrostatic spinning and pulse electrochemical deposition. • PPy controls the slow release of Sr 2+ and Cu 2+ for a long time. • Good physiological stability and long-term antibacterial effect. • Fiber has good osteogenic and angiogenic properties. The osteogenic differentiation and new bone formation are commonly delayed by bacterial infection of orthopedic implants, which is urgent to be resolved quickly in the clinic. The current paper prepared a strontium-doped electrospinning fiber membrane with antibacterial and osteogenic properties by pulse electrochemical method. Polylactic acid/hydroxyapatite (PLLA/HA) composite fiber substrate was fabricated by electrospinning technology, and strontium doped SrHA/Cu/Polypyrrole (PPy) composite coating was constructed with pulse electrodeposition method on its surface. The strontium doping technique, degradation of Sr 2+ and Cu 2+ , cellular compatibility, and the antibacterial activity of the fiber membrane were examined. The results revealed that the deposition of phosphorus and calcium on composite fiber was the highest, indicating good biological activity. The release of Sr 2+ and Cu 2+ was stable and gradual due to the modulation of PPy. The composite fiber presented excellent antibacterial performance and the antibacterial rate was close to 100% against Staphylococcus aureus and Escherichia coli. Furthermore, it is conducive to the adhesion, spread, and proliferation of vascular endothelial cells and osteoblasts, namely outstanding osteogenesis and angiogenesis abilities. In conclusion, the multifunctional PLLA/HA@SrHA/Cu/PPy composite fiber membrane with good antibacterial and osteogenic activity by electrospinning technology and pulsed electrochemical deposition method provides an effective strategy for the poor bone healing of infected bone defects. Strontium doped antibacterial osteogenic PLLA/HA@SrHA/Cu/PPy composite fiber was constructed by electrostatic spinning and pulsed electrochemical deposition technology, which showed good antibacterial properties and had the ability to promote bone induction and angiogenesis.

Electron beam irradiation-triggered strontium delivery from a bioresorbable fracture fixation device

A fracture fixation device capable of stimulating bone formation and inhibiting bone resorption is desirable for treating osteoporotic fractures. Strontium (Sr) is known to have a dual effect on bone metabolism, but its use in fracture fixation devices is still limited to date as the regulation of Sr release remains difficult. In this work, a bioresorbable device with controlled Sr release capability is fabricated by incorporating strontium carbonate (SrCO3) into a poly (lactic-co-glycolic acid) (PLGA) filament followed by surface modification using electron beam (ebeam) near-surface irradiation. The presence of SrCO3 effectively retards autocatalytic polymer degradation and improves the mechanical durability of the device. The utilization of ebeam irradiation induces controlled surface degradation of the polymer matrix and triggers the release of Sr in a predictable manner. In vitro experiment results reveal that the ebeam irradiated PLGA-SrCO3 filaments have good biocompatibility and can promote the proliferation of human foetal osteoblasts (hFOBs), making it potentially useful for improving osteoporotic fracture fixation.

Physicochemical Properties and Inductive Effect of Calcium Strontium Silicate on the Differentiation of Human Dental Pulp Stem Cells for Vital Pulp Therapies: An In Vitro Study.

The development of biomaterials that exhibit profound bioactivity and stimulate stem cell differentiation is imperative for the success and prognosis of vital pulp therapies. The objectives were to (1) synthesize calcium strontium silicate (CSR) ceramic through the sol–gel process (2) investigate its physicochemical properties, bioactivity, cytocompatibility, and its stimulatory effect on the differentiation of human dental pulp stem cells (HDPSC). Calcium silicate (CS) and calcium strontium silicate (CSR) were synthesized by the sol–gel method and characterized by x-ray diffraction (XRD). Setting time, compressive strength, and pH were measured. The in vitro apatite formation was evaluated by SEM-EDX and FTIR. The NIH/3T3 cell viability was assessed using an MTT assay. The differentiation of HDPSC was evaluated using alkaline phosphatase activity (ALP), and Alizarin red staining (ARS). Ion release of Ca, Sr, and Si was measured using inductive coupled plasma optical emission spectroscopy (ICP-OES). XRD showed the synthesis of (CaSrSiO4). The initial and final setting times were significantly shorter in CSR (5 ± 0.75 min, 29 ± 1.9 min) than in CS (8 ± 0.77 min, 31 ± 1.39 min), respectively (p < 0.05). No significant difference in compressive strength was found between CS and CSR (p > 0.05). CSR demonstrated higher apatite formation and cell viability than CS. The ALP activity was significantly higher in CSR 1.16 ± 0.12 than CS 0.92 ± 0.15 after 14 d of culture (p < 0.05). ARS showed higher mineralization in CSR than CS after 14 and 21 d culture times. CSR revealed enhanced differentiation of HDPSC, physicochemical properties, and bioactivity compared to CS.

In vivo osteogenic evaluation of titanium implants with strontium loaded nanotubes

Objective: To evaluate the in vivo osteogenic activity of titanium implants with strontium loaded TiO2 nanotubes (NTSr). Methods: The strontium loaded titanium nanotubes were formed on pure titanium implants through anodization and hydrothermal treatment, and the unmodified titanium (Control) and sheer TiO2 nanotubes (NT) were set to be control groups and treatment group. Inductively coupled plasma mass spectrometry (ICP-MS) was used to evaluate the Sr release at 28 days. Field emission scanning electron microscopes (FE-SEM) was used to view the micro-topography, atomic force microscope was used to exam the surface roughness, and nano-indenter was used to evaluate the hardness of three groups (n=3). Three groups of implant samples were inserted into the distal femoral metaphysis of New Zealand rabbits (n=4 at each time point). After 4 weeks and 12 weeks, samples were harvested. Micro-CT scanning, immunofluorescent and histological examinations were carried out. Results: The strontium ions could be released slowly for at least 28 days [the Sr concentration at 28 Day was (2.6±1.5) ng/ml]. NTSr coating exhibited a nanoscale tube array (the diameter was about 70 nm), and the surface roughness of implant was increased with the nanobube coating [Control (34.8±5.3) nm, NT (66.2±4.3) nm, NTSr (85.7±10.6) nm, F=37.59, P<0.001]. The surface roughness (Ra) of NT and NTSr groups was higher than the control group (P<0.05). Comparing to Control implants, NTSr implants exhibited a better osteogenic ability [the bone volume/total volume (BV/TV) value was Control (24.7±1.1)% vs. NTSr (37.7±1.9)% at 4 weeks (P<0.05), and Control (40.7±0.9)% vs. NTSr (51.9±2.1)% at 12 weeks (P<0.05)]. The fluorescent examination revealed that NTSr coating can also accelerated the generation of new bone tissue (bone tissue area% labelled by alizarin red at day 7 was Control (19.2±2.9)% vs. NT (35.4±3.7)% vs. NTSr (40.9±0.9)% (F=42.74, P<0.01). The results in the NT and NTSr group were statistically higher than that in the control group (P<0.05). Conclusions: The strontium loaded TiO2 nanotubes can enhance new bone formation around titanium implants.

Strontium- and peptide-modified silicate nanostructures for dual osteogenic and antimicrobial activity.

Developing multifunctional nanostructures that promote bone repair while fighting infection is highly desirable in bone regenerative therapies. Previous efforts have focused on achieving one property or another by altering the chemical makeup of nanostructures or using growth factors or antibiotics. We present nanostructures with several simultaneous functional attributes including positive effects of strontium on bone formation and prevention of osteoclast differentiation along with incorporation of antimicrobial peptides (AMP) to prevent infection. To form these multifunctional nanostructures, mesoporous calcium silicate (CaMSN) was modified with high levels of strontium. For this, CaMSNs were either partially substituted (20wt% Ca) or completely replaced with strontium (Sr) to form Sr-CaMSN or SrMSN. The mesoporous nature of these bioactive silicate nanostructures rendered a configuration for substantial AMP loading as well as their effective delivery. The physico-chemical and structural characterization of synthesized MSNs confirmed the mesoporous nature of the synthesized MSNs and their total surface area, pore size, pore volume and SBF-mediated bioactivity remained unaltered with the incorporation of Sr. However, biological evaluation confirmed that synthesized SrMSN upregulated osteogenic differentiation of mesenchymal stromal cells and significantly downregulated osteoclast differentiation. Also, the AMP-loaded MSNs prevented formation and growth of methicillin resistant Staphylococcus aureus (MRSA) biofilms. Thus, high Sr-containing AMP-loaded SrMSNs may combat MRSA-associated infection while promoting bone regeneration. The controlled availability of therapeutic Sr and AMP release as SrMSN degrade enables its potential application in bone tissue regeneration.

Local Release of Strontium from Sputter-Deposited Coatings at Implants Increases the Strontium-to-Calcium Ratio in Peri-implant Bone.

It is well known that strontium (Sr) has a significant effect on peri-implant bone healing when administered systemically. Due to the risk of adverse effects of such treatments, new routes focusing on the local, sustained release of Sr from bone-implant contact surfaces have been explored, with success in in vivo experiments. However, the increase of Sr concentrations in the peri-implant bone has not been described in depth yet. Here, we show that a local, sustained Sr release from Ti-Sr-O physical vapor deposition (PVD) coatings by magnetron sputter coating increases the Sr/Ca ratio close to the implant in a rabbit model and that the Sr/Ca background level is reached approximately 500 μm from the implant.

Leachability of cement mortars containing sewage sludge ash

Currently, the use of wastes and by-products as cementitious additions has become a necessity in the cement production sector. Because of their technical benefits and low cost. However, because of the pollutant load of these materials, it is essential to study the environmental behavior and the leachability of these cement mixtures before their use into buildings.This paper investigates the leachability of cement-based mortars containing various percentages of the waste material obtained from the incineration of sewage sludge, i.e. sewage sludge ash (SSA). The SSA and SSA- mortars was characterized by classical, analytical and instrumental measurement. In addition, the leaching behavior of heavy metals in SSA and SSA- mortars were assessed using NF EN12457-2 and NF PX31-211 leaching tests. Results illustrate that the leaching behavior of SSA shows an important release of Cr, Mo, Ba, Sr, V, Zn and Al. While, the leaching behavior of mortars containing different amounts of SSA showed that heavy metals were successfully immobilized in cement matrix.

On leaching mechanisms of major and trace elements from concrete - Carbonation, exposure to deicing salt and external sulphates

Model simulations and tank leach tests are compared to investigate the surface release of major and trace elements from ordinary Portland cement concrete and how this is affected by carbonation, NaCl or Na2SO4 in the eluent. It is distinguished between surface dissolution processes and diffusion of species from inside the concrete. Whereas alkalis, Cr(VI) and Sr are mainly released by diffusion, Ca, SO42−, Al, V, Ba and Zn are primarily released by surface dissolution. Changes in the leaching of Cr(VI) and V from concrete exposed to carbonation, NaCl or Na2SO4 are explained by the solubility equilibria of ettringite in which SO42− is substituted by CrO42− or VO43−. Barite and strontianite control the release of Ba and Sr. It is likely that C–S–H with incorporated Zn controls the release of Zn.

Impact of CO2 leakage from sub-seabed carbon dioxide storage on sediment and porewater geochemistry

Sub-seabed geological CO2 storage is discussed as a climate mitigation strategy, but the impact of any leakage of stored CO2 into the marine environment is not well known. In this study, leakage from a CO2 storage reservoir through near-surface sediments was mimicked for low leakage rates in the North Sea. Field data were combined with laboratory experiments and transport-reaction modelling to estimate CO2 and mineral dissolution rates, and to assess the mobilization of metals in contact with CO2-rich fluids and their potential impact on the environment. We found that carbonate and silicate minerals reacted quickly with the dissolved CO2, increasing porewater alkalinity and neutralizing about 5% of the injected CO2. The release of Ca, Sr, Ba and Mn was mainly controlled by carbonate dissolution, while Fe, Li, B, Mg, and Si were released from silicate minerals, mainly from deeper sediment layers. No toxic metals were released from the sediments and overall the injected CO2 was only detected up to 1 m away from seabed CO2 bubble streams. Our results suggest that low leakage rates of CO2 over short timescales have minimal impact on the benthic environment. However, porewater composition and temperature are effective indicators for leakage detection, even at low CO2 leakage rates.

Fabrication of strontium and simvastatin loaded hydroxyapatite microspheres by one-step approach

The development of multi-functional strontium (Sr) and simvastatin (SIM) loaded biomaterials to promote angiogenesis and osteogenesis is a promising therapeutic strategy. In order to overcome the complex synthesis process, low drug loading and burst release of drug-loaded biomaterials, in this study, we developed a microwave-assisted hydrothermal one-step approach to prepare Sr- and SIM-loaded hydroxyapatite microspheres for achieving long-term sustained-release of Sr and SIM. The developed one-step preparation method can maintain the chemical structure of simvastatin, and the drug loading rate of simvastatin can reach more than 30 wt%. The prepared double-loaded hydroxyapatite microspheres could sustainable release Sr and SIM for more than 35 days. The prepared hydroxyapatite microspheres containing Sr and SIM have a good application prospect in promoting bone formation. This simple and feasible one-step method can also provide reference for the preparation of other drug-loading microspheres.

Discrete geochemical behavior of Sr and Ba in the groundwater of Southern Mor Range, Balochistan, a tracer for igneous and sedimentary rocks weathering and related environmental issues

A comparative study of Strontium (Sr) and Barium (Ba) along with associated major ions of groundwater was made from the Southern Mor Range, Balochistan, where both igneous and sedimentary rocks are exposed. In the studied samples, Sr2+ varies from 237 to 6,723 with a mean of 1,688 μg/l, while Ba2+ ranged from 40 to 1,332 μg/l with a mean of 207 μg/l. TDS and Sr2+ displayed moderate positive, while Ba2+ showed a slight negative relation. Majority (80.85%) of the samples have existed in the narrow pH range (7.5–8.5). The impact of water-rock interaction is evidenced from the Gibbs diagram; showed influence of igneous and sedimentary rocks on the release of Sr2+ and Ba2+. It is also evidenced from molar ratio of Sr2+/Ca2+, Mg2+/Ca2+, Na+/Cl−, Mg2+/Cl− of the groundwater. Strontium possessed fairly high relative mobility (RM, av. 0.349) and mobility index (MI, av. 4.38), while RM (av. 0.003) and MI (av. 0.04) of Ba2+ was very low. The saturation indices (SI) plots barite vs. celestite, showed saturation of Ba, while Sr2+ ions are unsaturated. The low Ba2+/Sr2+ (av. 0.208) indicated the existence of aquifer in low elevation areas and the HCO3−/Cl− ratio (>1) demonstrated a short flow path and speedy flow. The suitability of groundwater was assessed for drinking purpose as per World Health Organization (WHO) and Expanded Programme on Immunization (EPI) guidelines and possible environmental issues were discussed.

Effect of strontium substitution on structural, sinterability, physicomechanical and biological properties of akermanite ceramic

Despite the excellent in vitro and in vivo performance of akermanite ceramic, its poor toughness and strength limit the biomedical application, particularly under load. Herein, the incorporation of strontium enhanced the physicomechanical properties of akermanite and this is ascribed to the decrease in grain size and better sinterability. To investigate the biological performance, the bone-cell interaction with sintered pellets was assessed by in vitro biocompatibility with human fetal osteoblast cell (hFOB). The cell viability using MTT assay revealed that the Ca1.9Sr0.1MgSi2O7 pellets with finer grain size provided better interaction between the cells compared to the unsubstituted counterpart with larger grain size. Our findings highlighted that the synergistic effect of controlled degradation rate and release of Sr2+ into the medium enhanced the in vitro biological properties of akermanite-based materials.

Strontium-releasing sol–gel bioactive glass spheres and their ability to stimulate osteogenic differentiation in osteoporotic bone marrow mesenchymal stem cells

Osteoporosis is a metabolic disease that affects bone tissue and is highly associated with bone fractures. Due to the low bioavailability of conventional treatments for this disease, an alternative has been developed to project systems for the local release of therapeutic agents, such as bioactive glass (BG) containing therapeutic ions and molecules that are released during dissolution. In this study, submicron BG spheres derived from the sol–gel process containing Sr, a potential ion to prevent bone loss and increase bone formation, were evaluated. For the first time, the effect of these particles was investigated on the reduced osteogenic potential of bone marrow mesenchymal stem cells (BMMSCs) obtained from osteoporotic rats. The obtained submicron and spherical Sr-containing BG particles showed controlled ion release capacity, and osteogenic differentiation assays showed that these materials could stimulate the reduced differentiation potential of BMMSCs from osteoporotic rats due to Sr release.

Osteoinductive potential and antibacterial characteristics of collagen coated iron oxide nanosphere containing strontium and hydroxyapatite in long term bone fractures

Since osteoporosis and long-term bone fractures along with their possible infections after fractures and surgery is one of the most important challenges in bone repair, the subject of this study is the use of nanotechnology methods in drug delivery, infection control, stimulation of bone cells for proliferation and differentiation, and improving the mechanical strength during treatment. Iron oxide nanospheres-hydroxyapatite-strontium@collagen (IONSs-HA-SR@C) was synthesized by co-precipitation method and their physicochemical properties were investigated by FE-SEM, TEM, DLS, XRD, FT-IR, and atomic absorption methods. The effect of IONSs-HA-SR@C on MC3T3-E1 cell differentiation and proliferation and their morphological changes was determined by CCK-assay and H&E staining methods. Also, to evaluate the antibacterial activity, Aureus Rosenbach were used as a model and cultured with IONSs-HA-SR@C. Finally, PCR method was used to evaluate cell differentiation by BMP-2, ALP, OCN, RUNX-2 and COL1 genes markers. The results revealed that the IONSs-HA-SR@C have almost spherical shapes and have a uniform size with dimensions of 63.4 ± 2.78 nm. Likewise, XRD, FTIR, and atomic absorption results indicated HA and SR loading, and C coating on the IONSs. Also, the SR release rate reached 81% in 192 h with pH = 6, and the burst release was<40% in 24 h. Moreover, IONSs-HA-SR@C-treated MC3T3-E1 cells had higher proliferation than the control group and showed more favourable differentiation. H&E staining and real-time PCR of bone differentiation marker genes confirmed this claim. The IONSs-HA-SR@C antibacterial activity indicates a significant reduction in infection. Ultimately, the IONSs-HA-SR@C has excellent biocompatibility, ossification coefficient and antibacterial activity; hence it has great potential for repairing bone defects and preventing infection.

A Study Comparing Efficacy of Morning Dosage versus Evening Dosage of Oral Micronised Progesterone Sustained Release SR 300mg in Prevention of Preterm Labour

Objectives: To assess the efficacy of oral micronized progesterone SR 300 in preventing preterm labour after arresting it, with changes in dosage timing. The main purpose of this study is to find out whether there is a clinico pharmacological correlation if same drug is given at different timings Materials and Methods: Prospective randomized study was done at our institution. Total sample size of 130 women who came in preterm labour and process of preterm labour was arrested with Tocolytics were included in the study group. Sample was divided into 2 groups of 65 womens in each group in view of prevention of preterm labour. One group was given MNP SR 300 at 9am and 2nd group was given MNP SR 300 at 9pm by oral route. They were studied for the difference in maternal outcomes like prolongation of gestational age at delivery and neonatal outcome like birth weight, maturity, morbidity and mortality. Results: Both the group were comparable with respect to age and parity. Our study showed that there was no statistically significant difference with respect to maternal and fetal outcome with changes in timings to two groups who were given MNP SR 300 orally at 9am and 9pm. Conclusion: More studies on big samples are recommended to further analyse our results, since this the only study till date.

Basic properties of novel S-PRG filler-containing cement.

This study was aimed to evaluate the effect of a novel surface pre-reacted glass-ionomer (S-PRG) filler-containing cement for root caries. We prepared the cements using five different S-PRG filler amounts (0, 10, 20, 30, and 40 wt%). Compressive strength, ion release, acid buffering capacity, and microstructure of the as-prepared cements were evaluated. The compressive strength was statistically significant; it was highest for 0 wt% S-PRG cement. Ion release in 0 wt% S-PRG was highest for F- and Al, whereas in 40 wt% S-PRG it was highest for B. For 20, 30, and 40 wt% S-PRG cements, Na and Sr release was higher compared to the other ions. The acid buffering capacity was significantly higher in the 40 wt% S-PRG cement than in the others. In the microstructural analysis, no difference of surface structure was observed among each of the S-PRG filler contents (0-40 wt% S-PRG).

Strontium isotopes trace biological activity in the Critical Zone along a climate and vegetation gradient

Weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock (the “geogenic nutrient pathway”). However, the prominence of this link is dependent on the efficiency of nutrient recycling from plant litter (the “organic nutrient cycle”). Isotope ratios of strontium (Sr), an element that behaves similarly to Ca in ecosystems, confer two types of information: radiogenic Sr isotopes inform as to the sources of Sr and the degree of weathering, while stable Sr isotopes constrain partitioning between compartments of the Critical Zone (bedrock, water, secondary solids, and plants). To date, however, neither the reactions nor the mass balance between compartments that fractionate Sr isotopes, nor the fractionation factors involved, are well understood. Here, we present geochemical budgets of Sr (using radiogenic and stable Sr isotopes, and Ca/Sr ratios) at four sites along a substantial climate and primary production gradient in the coastal mountains of Chile. We found that Sr release through weathering is isotopically congruent, and released Sr is not strongly isotopically fractionated either during secondary mineral formation or transfer into the exchangeable pool. Despite this, the 88Sr/86Sr ratio of bio-available Sr, which should reflect the ratio of dissolved Sr, is higher than that of rock and regolith. We propose that this offset is caused by plants: while 88Sr/86Sr in plant organs at the four study sites systematically increased from roots towards their leaves, whole-plant Sr isotope compositions indicate preferential uptake of light Sr into plants (with a fractionation of up to −0.3‰ relative to the bio-available pool). Despite this strong biological fractionation, 88Sr/86Sr ratios in bio-available Sr do not covary with biomass production across our study sites, because with greater plant growth Sr is recycled more times after release by weathering – an isotope-neutral process. Rather, the loss of Sr from the ecosystem in solid organic material sets the isotope ratio of dissolved or bio-available Sr. Organic solids thus appear to constitute a significant export path of elements released during weathering, with the removal of solid plant debris reducing the recycling factor of Sr, and possibly that of other mineral nutrients too.

Incorporation of Sr2+ and Ag nanoparticles into TiO2 nanotubes to synergistically enhance osteogenic and antibacterial activities for bone repair

Osteogenic and antibacterial activities are two basic requirements for orthopedic implants. The present study mainly focused on the investigation of the osteoblast behaviors and antibacterial activities of Sr/Ag-incorporated titanium dioxide (TiO2) nanotube array (TNT) on the titanium surface. To this end, the Sr-incorporated TNT was firstly fabricated on the titanium surface by electrochemical anodization and hydrothermal treatment, and then Ag nanoparticles (AgNPs) were incorporated onto the nanotubes by reduction of the adsorbed Ag+ through ultraviolet (UV) irradiation. The TiO2 nanotubes had excellent hydrophilicity and Sr incorporation can further enhance the hydrophilicity; however, the AgNPs loading could slightly increase water contact angle. The release of Sr2+ can not only promote osteoblast adhesion, proliferation and mineralization, but also up-regulate the alkaline phosphatase (ALP) and osteocalcin (OCN) expression. The introduction of AgNPs on Sr-incorporated nanotubes did not significantly influence the osteoblast cell behaviors; however, it can effectively inhibit the adhesion and growth of Escherichia coli. Therefore, the method of the present study is expected to be suitable for surface modification of titanium surface to simultaneously enhance the osteo-bonding ability and antibacterial activities for bone repair.

Electrodeposition of Sr-substituted hydroxyapatite on low modulus beta-type Ti-45Nb and effect on in vitro Sr release and cell response.

Beta-type Ti-based alloys are promising new materials for bone implants owing to their excellent mechanical biofunctionality and biocompatibility. For treatment of fractures in case of systemic diseases like osteoporosis the generation of implant surfaces which actively support the problematic bone healing is a most important aspect. This work aimed at developing suitable approaches for electrodeposition of Sr-substituted hydroxyapatite (Srx-HAp) coatings onto Ti-45Nb. Potentiodynamic polarization measurements in electrolytes with 1.67 mmol/L Ca(NO3)2, which was substituted by 0, 10, 50 and 100% Sr(NO3)2, and 1 mmol/L NH4H2PO4 at 333 K revealed the basic reaction steps for OH- and PO43- formation needed for the chemical precipitation of Srx-HAp. Studies under potentiostatic control confirmed that partial or complete substitution of Ca2+- by Sr2+-ions in solution has a significant effect on the complex reaction process. High Sr2+-ion contents yield intermediate phases and a subsequent growth of more refined Srx-HAp coatings. Upon galvanostatic pulse-deposition higher reaction rates are controlled and in all electrolytes very fine needle-like crystalline coatings are obtained. With XRD the incorporation of Sr-species in the hexagonal HAp lattice is evidenced. Coatings formed in electrolytes with 10 and 50% Sr-nitrate were chemically analyzed with EDX mapping and GD-OES depth profiling. Only a fraction of the Sr-ions in solution is incorporated into the Srx-HAp coatings. Therein, the Sr-distribution is laterally homogeneous but non-homogeneous along the cross-section. Increasing Sr-content retards the coating thickness growth. Most promising coatings formed in the electrolyte with 10% Sr-nitrate were employed for Ca, P and Sr release analysis in Tris-Buffered Saline (150 mM NaCl, pH 7.6) at 310 K. At a sample surface: solution volume ratio of 1:200, after 24 h the amount of released Sr-ions was about 30-35% of that determined in the deposited Srx-HAp coating. In vitro studies with human bone marrow stromal cells (hBMSC) revealed that the released Sr-ions led to a significantly enhanced cell proliferation and osteogenic differentiation and that the Sr-HAp surface supported cell adhesion indicating its excellent cytocompatibility.

Fabrication and biological evaluation of the coating co‐doped strontium and zinc nanoparticles on porous pure titanium surface by hydrothermal method

Background For dental implants, early infection and peri-implantitis after implant restoration are major reasons for implant failure. Plaque biofilm formation is the initiator for implant-related infection. Therefore, it is urgent to develop a new antibacterial implant materials or treatment methods. Aim/Hypothesis In this study, Sr- and Zn- incorporated micro nano-structured titanium surface with nanorods (MNT-Sr Zn) was fabricated by a two-step hydrothermal process, aiming to improve osseointegration and reduce implant failure caused by implant-related infection and broaden new ideas for the future research Material and Methods The Mod Ti surfaces were used as a control. The characterization of different surfaces was detected by a field emission scanning electron microscope (FE-SEM) equipped with energy dispersive spectra (EDS) detector, x-ray diffractometer (XRD) and inductively coupled plasma mass spectroscopy (ICP-MS). Meanwhile, Staphylococcus aureus (S. aureus) was selected to evaluate antibacterial properties through Live Dead Staining and watching the adhesive bacterial morphology under FE-SEM. What's more, rat bone marrow-derived mesenchymal stem cells (rBMSCs) were cultured on the surfaces to detect their early osteogenic properties, like the alkaline phosphatase(ALP) activity and the expressions of osteogenesis related genes. Results The results confirmed that nanorod-like particles with a diameter of about 30-50 nm of MNT-Sr Zn composed of well-crystallized ZnO and SrTiO3 phases. In the EDS spectra, the elements of Zn and Sr were evenly distributed, and approximately 1.49 ± 0.16 wt% and 21.69 ± 2.74 wt% respectively. Besides, the release of Sr2+ and Zn2+ was a controlled and long-term process. More importantly, Zn-containing nanorod-like particles and the morphology could work together, slightly decreasing adhesion of S. aureus but increasing the proportion of dead cells, thus inhibiting subsequent biofilm formation, compared with the controlled group. In addition to this, MNT-Sr Zn could enhance the osteogenic differentiation via the upregulation of the transcription of osteogenic related genes and the expression of ALP in vitro. Conclusion and Clinical Implications This research provides a new surface modification method on titanium substrate for multi-functional implant material development. Due to the co-doping of Sr and Zn in the coating, biomechanical stability, antibacterial capability and early osteogenic inductive effect are enhanced, which has the potential to be applied in dental implantation in the future.