Strontium ranelate improves the interaction of osteoblastic cells with titanium substrates: Increase in cell proliferation, differentiation and matrix mineralization

Characterisation of Sr2+ mobility in osteoporotic rat bone marrow by cryo-ToF-SIMS and cryo-OrbiSIMS

Mass spectrometric imaging approach for ex vivo monitoring of drug transport in bone sections. Cryo-ToF-SIMS depth profiling and high-resolution imaging as well as OrbiSIMS analysis revealed inhomogeneous Sr2+ transport in rat bone marrow.

Nutrient alloying elements in biodegradable metals: a review

As a new generation of biomedical metallic materials, biodegradable metals have become a hot research topic in recent years because they can completely degrade in the human body, thus preventing secondary surgery, and reducing the pain and economic burden for patients. Clinical applications require biodegradable metals with adequate mechanical properties, corrosion resistance, and biocompatibility. Alloying is an important method to create biodegradable metals with required and comprehensive performances. Since nutrient elements already have important effects on various physiological functions of the human body, the alloying of nutrient elements with biodegradable metals has attracted much attention. The present review summarizes and discusses the effects of nutrient alloying elements on the mechanical properties, biodegradation behavior, and biocompatibility of biodegradable metals. Moreover, future research directions of biodegradable metals with nutrient alloying elements are suggested.

Biofunctional Elements Incorporated Nano/Microstructured Coatings on Titanium Implants with Enhanced Osteogenic and Antibacterial Performance

Bone fracture is prevalent among athletes and senior citizens and may require surgical insertion of bone implants. Titanium (Ti) and its alloys are widely used in orthopedics due to its high corrosion resistance, good biocompatibility, and modulus compatible with natural bone tissues. However, bone repair and regrowth are impeded by the insufficient intrinsic osteogenetic capability of Ti and Ti alloys and potential bacterial infection. The physicochemical properties of the materials and nano/microstructures on the implant surface are crucial for clinical success and loading with biofunctional elements such as Sr, Zn, Cu, Si, and Ag into nano/microstructured TiO2 coating has been demonstrated to enhance bone repair/regeneration and bacterial resistance of Ti implants. In this review, recent advances in biofunctional element-incorporated nano/microstructured coatings on Ti and Ti alloy implants are described and the prospects and limitations are discussed.

New insights into ToF-SIMS imaging in osteoporotic bone research

The present work focuses on the application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in osteoporotic bone research. In order to demonstrate the benefit, the authors present concrete application examples of ToF-SIMS in three different areas of bone research. ToF-SIMS as a mass spectrometric imaging technique allows simultaneous visualization of mineralized and nonmineralized bone tissue as well as implanted biomaterials and bone implant interphases. In the first example, the authors show that it is possible to study the incorporation and distribution of different components released from bone filler materials into bone with a single mass spectrometric measurement. This not only enables imaging of nonstained bone cross sections but also provides further insights beyond histologically obtained information. Furthermore, they successfully identified several mass fragments as markers for newly formed cartilage tissue and growth joint in bone. Different modes of ToF-SIMS as well as different SIMS instruments (IONTOF's TOF.SIMS 5 and M6 Hybrid SIMS, Ionoptika's J105) were used to identify these mass signals and highlight the high versatility of this method. In the third part, bone structure of cortical rat bone was investigated from bone sections embedded in technovit (polymethyl methacrylate, PMMA) and compared to cryosections. In cortical bone, they were able to image different morphological features, e.g., concentric arrangement of collagen fibers in so-called osteons as well as Haversian canals and osteocytes. In summary, the study provides examples of application and shows the strength of ToF-SIMS as a promising analytical method in the field of osteoporotic bone research.

Effect of SrR delivery in the biomarkers of bone regeneration during the in vitro degradation of HNT/GN coatings prepared by EPD

Among strontium-based drugs, the Strontium ranelate (SrR) is a divalent strontium salt of ranelic acid which has an overall effect over the bone microarchitecture improvement. However, some findings reveal that the SrR affects in an opposite manner to the cell proliferation and osteoblastic differentiation, based on its concentration. Consequently, its release should be controlled. The incorporation of Halloysite nanotubes (HNT) as nanocarriers of SrR, into gelatine (GN) coatings, tailors the release of this anabolic bone-forming and anti-catabolic agent to stimulate bone growth. In fact, as-prepared GN/HNT-SrR coatings release 100 % SrR in phosphate buffered saline (PBS) within 21 days, and cellular studies of the nanocomposite coatings (MTT, Alkaline Phosphatase activity (ALP) and Calcium deposition assay) confirm the valuable bio-performance of these composite coatings to enhanced bone regeneration. In the present manuscript, suspensions with HNT/GN weight ratio of 0.5 are formulated to coat AISI 316 L stainless steel foils by Electrophoretic Deposition (EPD). Zeta potential determination is used to stablish the drug loading (HNT-SrR) by electrostatic interaction, as well as to optimize the dispersion of bare HNT and HNT SrR-loaded in a GN aqueous solution. Polyethilenimnine (PEI) is used as stabilizer to buffer the suspension media, assure cargo-drug dispersion and sequential release, while the thermal gelling of the suspension controls and step up the coating formation during EPD.

Strontium promotes osteogenic differentiation by activating autophagy via the the AMPK/mTOR signaling pathway in MC3T3‑E1 cells

Strontium (Sr) is an alkaline earth metal that exerts the dual effect of improving bone formation and suppressing bone resorption, resulting in increased bone apposition rates and bone mineral density. However, the mechanisms through which Sr exerts these beneficial effects on bone have yet to be fully elucidated. The present study aimed to reveal the underlying molecular mechanisms associated with Sr‑induced osteogenic differentiation. The effects of Sr on cell proliferation and osteogenic differentiation were analyzed by MTT assay, RT‑qPCR, western blot analysis, alkaline phosphatase (ALP) and Alizarin red staining assays. The extent of autophagy was determined by monodansylcadaverine (MDC) staining and western blot analysis of two markers of cellular autophagic activity, the steatosis‑associated protein, sequestosome‑1 (SQSTM1/p62), and the two isoforms of microtubule‑associated protein 1 light chain 3 (LC3), LC‑3‑I/II. The expression levels of AMP‑activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) were also detected by western blot analysis. Sr at a concentration of 3 mM exerted the most pronounced effect on osteogenic differentiation, without any apparent cell toxicity. At the same time, cellular autophagy was active during this process. Subsequently, autophagy was blocked by 3‑methyladenine, and the enhancement of osteogenic differentiation in response to Sr was abrogated. Additionally, the phosphorylation level of AMPK was significantly increased, whereas that of mTOR was significantly decreased, in the Sr‑treated group. Taken together, the findings of the present study demonstrate that Sr stimulates AMPK‑activated autophagy to induce the osteogenic differentiation of MC3T3‑E1 cells.

Investigation of strontium transport and strontium quantification in cortical rat bone by time-of-flight secondary ion mass spectrometry

Next-generation bone implants will be functionalized with drugs for stimulating bone growth. Modelling of drug release by such functionalized biomaterials and drug dispersion into bone can be used as predicting tool for biomaterials testing in future. Therefore, the determination of experimental parameters to describe and simulate drug release in bone is essential. Here, we focus on Sr2+ transport and quantification in cortical rat bone. Sr2+ dose-dependently stimulates bone-building osteoblasts and inhibits bone-resorbing osteoclasts. It should be preferentially applied in the case of bone fracture in the context of osteoporotic bone status. Transport properties of cortical rat bone were investigated by dipping experiments of bone sections in aqueous Sr2+ solution followed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling. Data evaluation was carried out by fitting a suitable mathematical diffusion equation to the experimental data. An average diffusion coefficient of D = (1.68 ± 0.57) · 10-13 cm2 s-1 for healthy cortical bone was obtained. This value differed only slightly from the value of D = (4.30 ± 1.43) · 10-13 cm2 s-1 for osteoporotic cortical bone. Transmission electron microscopy investigations revealed a comparable nano- and ultrastructure for both types of bone status. Additionally, Sr2+-enriched mineralized collagen standards were prepared for ToF-SIMS quantification of Sr2+ content. The obtained calibration curve was used for Sr2+ quantification in cortical and trabecular bone in real bone sections. The results allow important insights regarding the Sr2+ transport properties in healthy and osteoporotic bone and can ultimately be used to perform a simulation of drug release and mobility in bone.

Osteoinductivity and Antibacterial Properties of Strontium Ranelate-Loaded Poly(Lactic-co-Glycolic Acid) Microspheres With Assembled Silver and Hydroxyapatite Nanoparticles

Bone-related infection rates are 4–64% in long open bone fractures and nearly 1% in joint-related surgeries. Treating bone infections and infection-related bone loss is very important. The present study prepared strontium ranelate (SR)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres (PM) with assembled silver nanoparticles (AgNPs) and hydroxyapatite nanoparticles (HANPs) (SR-PM-Ag-HA) through a novel solid-in-oil nanosuspension (S/O/N) method to achieve osteoinductivity and antibacterial properties. We evaluated the microstructure, drug release, biocompatibility, osteoinductivity, and antibacterial activity in vitro. The microspheres showed a stable shape and size. The cumulative drug release reached a maximum of ∼90% after 22 days. All groups loaded with SR enhanced MC3T3-E1 cell proliferation to a greater degree than pure PM. The osteoinductivity behavior was investigated by ALP staining and real-time PCR of osteogenic differentiation marker genes. The antibacterial activity was evaluated using antibacterial ability and biofilm formation assays. SR-PM-Ag-HA greatly enhanced osteogenic differentiation and showed excellent antibacterial properties. These results indicated that SR-PM-Ag-HA could be biocompatible and suitable for drug delivery, osteoinduction, and antibiosis, and therefore, have potential applications in the treatment of bone-related infections and promotion of bone formation at infected sites.

Effects of strontium ranelate treatment on osteoblasts cultivated onto scaffolds of trabeculae bovine bone

Blocks of Bovine bone have shown promising results as implantable scaffolds to promote bone regeneration. Strontium ranelate (SrR) is both an antiresorptive and an anabolic drug that has been indicated for oral administration to treat osteoporosis. Few studies, however, have investigated the local effects of SrR and its use in association with biomaterials thus far. In this work, we investigated SrR effects in cultures of primary osteoblasts (PO, from Wistar rats calvaria) and immortalized osteoblasts (IO, from MC3T3-E1 cell line) cultivated as a monolayer or in association with scaffolds of bovine bone in mineralized (MBB) and demineralized (DBB) forms. The optimum dose to induce SrR effects on cell viability was established as 0.1 mM. Our results suggested that the local administration of SrR is biocompatible and non-cytotoxic. In addition, SrR appeared to accelerate primary osteoblast cell differentiation by enhancing alkaline phosphatase activity, the expression of osteogenic differentiation markers, the synthesis of the organic matrix, and a decrease of Ca²⁺ ions in mineralized nodules. DBB was found to be a better scaffold material to promote PO and IO cell proliferation. Exposing the proteins of the demineralized bone matrix might improve scaffold osteoconductive properties. Our results indicated the importance of further investigation of the administration of SrR at sites of bone repair. The association of SrR and bone grafts suggests the possibility of using SrR as a co-adjuvant for bone tissue bioengineering and in bone regeneration therapies.

Vibrational spectroscopy and imaging: applications for tissue engineering

Tissue engineering (TE) approaches strive to regenerate or replace an organ or tissue. The successful development and subsequent integration of a TE construct is contingent on a series of in vitro and in vivo events that result in an optimal construct for implantation. Current widely used methods for evaluation of constructs are incapable of providing an accurate compositional assessment without destruction of the construct. In this review, we discuss the contributions of vibrational spectroscopic assessment for evaluation of tissue engineered construct composition, both during development and post-implantation. Fourier transform infrared (FTIR) spectroscopy in the mid and near-infrared range, as well as Raman spectroscopy, are intrinsically label free, can be non-destructive, and provide specific information on the chemical composition of tissues. Overall, we examine the contribution that vibrational spectroscopy via fiber optics and imaging have to tissue engineering approaches.

Local delivery of strontium ranelate promotes regeneration of critical size bone defects filled with collagen sponge

The effect of local delivery of strontium ranelate (SR) on bone regeneration of critical size bone defects filled with collagen sponge was evaluated. Bone defects of 5 mm diameter created in rat calvaria were filled with collagen sponge (C); collagen sponge with 5 mM Sr²⁺ SR (C5SR) or collagen sponge with 50 mM Sr²⁺ SR (C50SR). After 2, 4, and 6 weeks, bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) were evaluated by computed microtomography. At 6 weeks, histological analysis was performed. Intragroup comparisons were made by the Friedman test, while comparisons between groups were made by Kruskal-Wallis test (α = 5%). All groups showed increased BV, BS, Tb.Th, and Tb.N over time, but only C50SR promoted the reduction of Tb.Sp (p < 0.05). No significant differences between groups were detected at weeks 2 and 4. However, C50SR showed the highest values of BV, BS, and Tb.Th at 6 weeks (p < 0.05). Histological analysis revealed connective tissue in C and C5SR and immature bone tissue in C50SR. Local delivery of SR 50 mM Sr²⁺ associated with collagen sponge increased and accelerated bone regeneration in critical bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 333-341, 2018.

Does Local Application of Strontium Increase Osteogenesis and Biomaterial Osteointegration in Osteoporotic and Other Bone Tissue Conditions: Review of Literature

Osteoporosis and other pathological bone conditions can impair bone regeneration properties, consuming in increased morbidity and decreased quality of life. Changes of bone healing can result in poor osteointegration and surgical failures if implants are used. To overcome and facilitate bone regeneration, more attempts are made to develop an ideal synthetic scaffold with better biocompatibility, osteoconductivity, bioactivity, osteoinductivity and interconnected porosity. It is considered that strontium, being similar to calcium, can be incorporated into the mineral phase of the bone remodeling. This quality had led strontium to be used as an osteoporotic medication to improve quality of bone and to reduce the risk of bone fractures. Also local application of strontium has been widely used within different biomaterials in tissue engineering researches.

In this review authors wanted to provide an overview about strontium, its mechanisms of action in bone tissue and initiated changes of bone remodeling within biomaterials.

Strontium ranelate-loaded PLGA porous microspheres enhancing the osteogenesis of MC3T3-E1 cells

Biodegradable poly lactic-co-glycolic acid (PLGA) has been used as a tissue engineering scaffold as well as a carrier for the delivery of proteins, drugs, and other macromolecules.

The effects of strontium on bone mineral: A review on current knowledge and microanalytical approaches

The interest in effects of strontium (Sr) on bone has greatly increased in the last decade due to the development of the promising drug strontium ranelate. This drug is used for treating osteoporosis, a major bone disease affecting hundreds of millions of people worldwide, especially postmenopausal women. The novelty of strontium ranelate compared to other treatments for osteoporosis is its unique effect on bone: it simultaneously promotes bone formation by osteoblasts and inhibits bone resorption by osteoclasts. Besides affecting bone cells, treatment with strontium ranelate also has a direct effect on the mineralized bone matrix. Due to the chemical similarities between Sr and Ca, a topic that has long been of particular interest is the incorporation of Sr into bones replacing Ca from the mineral phase, which is composed by carbonated hydroxyapatite nanocrystals. Several groups have analyzed the mineral produced during treatment; however, most analysis were done with relatively large samples containing numerous nanocrystals, resulting thus on data that represents an average of many crystalline domains. The nanoscale analysis of the bone apatite crystals containing Sr has only been described in a few studies. In this study, we review the current knowledge on the effects of Sr on bone mineral and discuss the methodological approaches that have been used in the field. In particular, we focus on the great potential that advanced microscopy and microanalytical techniques may have on the detailed analysis of the nanostructure and composition of bone apatite nanocrystals produced during treatment with strontium ranelate.