The effectiveness of the controlled release of simvastatin from β-TCP macrosphere in the treatment of OVX mice

Efficacy of soluble lansoprazole-impregnated beta-tricalcium phosphate for bone regeneration

The proton pump inhibitor lansoprazole has been previously identified to upregulate the expression and transcriptional activity of runt-related transcription factor 2 (Runx2) that promotes lineage commitment and differentiation of osteoprogenitor cells. We could not elicit the expected efficacy of insoluble lansoprazole in enhancing osteogenesis when combined with beta-tricalcium phosphate (β-TCP) bone substitutes. This study aimed to evaluate the effects of soluble lansoprazole on in vitro osteoblastogenesis and new bone formation in vivo. Commercially available human mesenchymal stem cells or patient-derived bone marrow-derived stromal cells were treated with 20 µM of soluble lansoprazole at the beginning of osteogenic induction. Soluble lansoprazole-impregnated β-TCP materials were embedded in the cortical bone defect model of rabbits. Rabbits were sacrificed four weeks postoperatively and undecalcified bone specimens were prepared for evaluation of intra-material new bone formation. Only a 1-day treatment with soluble lansoprazole facilitated osteoblastic differentiation and matrix calcium deposition when added to undifferentiated human mesenchymal stromal cells at the beginning of the osteogenic differentiation. Soluble lansoprazole dose-dependently accelerated intra-material new bone formation when being impregnated with porous β-TCP artificial bones. Local use of soluble lansoprazole can be applicable for fracture and bone defect repair when combined with porous β-TCP scaffolds.

Amorphous calcium magnesium phosphate nanocomposites with superior osteogenic activity for bone regeneration

The seek of bioactive materials for promoting bone regeneration is a challenging and long-term task. Functionalization with inorganic metal ions or drug molecules is considered effective strategies to improve the bioactivity of various existing biomaterials. Herein, amorphous calcium magnesium phosphate (ACMP) nanoparticles and simvastatin (SIM)-loaded ACMP (ACMP/SIM) nanocomposites were developed via a simple co-precipitation strategy. The physiochemical property of ACMP/SIM was explored using transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) and high-performance liquid chromatograph (HPLC), and the role of Mg²⁺ in the formation of ACMP/SIM was revealed using X-ray absorption near-edge structure (XANES). After that, the transformation process of ACMP/SIM in simulated body fluid (SBF) was also tracked to simulate and explore the in vivo mineralization performance of materials. We find that ACMP/SIM releases ions of Ca²⁺, Mg²⁺ and PO43−, when it is immersed in SBF at 37°C, and a phase transformation occurred during which the initially amorphous ACMP turns into self-assembled hydroxyapatite (HAP). Furthermore, ACMP/SIM displays high cytocompatibility and promotes the proliferation and osteogenic differentiation of MC3T3-E1 cells. For the in vivo studies, lamellar ACMP/SIM/Collagen scaffolds with aligned pore structures were prepared and used to repair a rat defect model in calvaria. ACMP/SIM/Collagen scaffolds show a positive effect in promoting the regeneration of calvaria defect after 12 weeks. The bioactive ACMP/SIM nanocomposites are promising as bone repair materials. Considering the facile preparation process and superior in vitro/vivo bioactivity, the as-prepared ACMP/SIM would be a potential candidate for bone related biomedical applications.

Simvastatin-Incorporated Drug Delivery Systems for Bone Regeneration

Local drug delivery systems composed of biomaterials and osteogenic substances provide promising strategies for the reconstruction of large bone defects. In recent years, simvastatin has been studied extensively for its pleiotropic effects other than lowering of cholesterol, including its ability to induce osteogenesis and angiogenesis. Accordingly, several studies of simvastatin incorporated drug delivery systems have been performed to demonstrate the feasibility of such systems in enhancing bone regeneration. Therefore, this review explores the molecular mechanisms by which simvastatin affects bone metabolism and angiogenesis. The simvastatin concentrations that promote osteogenic differentiation are analyzed. Furthermore, we summarize and discuss a variety of simvastatin-loaded drug delivery systems that use different loading methods and materials. Finally, current shortcomings of and future development directions for simvastatin-loaded drug delivery systems are summarized. This review provides various advanced design strategies for simvastatin-incorporated drug delivery systems that can enhance bone regeneration.

Simvastatin loaded chitosan guided bone regeneration membranes stimulate bone healing

BACKGROUND AND OBJECTIVE

Electrospun chitosan membranes (ESCM) modified with short-chain fatty acids have the ability to control the release of simvastatin (SMV), an anti-cholesterol drug with osteogenic potential, for guided bone regeneration (GBR) applications. This study evaluated in vivo osteogenic effects of rapid short release of SMV (4 weeks) vs long sustained release (8 weeks) from acetic anhydride (AA)-and hexanoic anhydride (HA)-modified ESCMs, respectively.

METHODS

AA ESCMs loaded with 10 or 50 µg SMV and HA ESCMs loaded with 50 µg SMV were evaluated for biocompatibility and bone formation at 4 and 8 weeks, in 5 mm critical size rat calvarial defects, using histological evaluation and micro-CT analysis.

RESULTS

No severe inflammatory response was noticed around the ESCMs. Less hydrophobic AA membranes showed signs of resorption by week 4 and were almost completely resorbed by week 8 whereas the more hydrophobic HA membranes resorbed slowly, remaining intact over 8 weeks. In micro-CT analysis, 10 µg SMV-loaded AA membranes did not show significant bone formation as compared to non-loaded AA membranes at either evaluation time points. 50 µg SMV-loaded AA membranes stimulated significantly more bone formation than non-loaded AA membranes by week 4 (%bone = 31.0 ± 5.9% (AA50) vs 18.5 ± 13.7% (AA0)) but showed no difference at week 8. HA membranes with 50 µg SMV showed significantly more bone formation as compared to corresponding non-loaded membranes by week 8 (%bone = 61.7 ± 8.9% (HA50) vs 33.9 ± 29.7% (HA0)), though such an effect was not significant at week 4.

CONCLUSION

These results indicate that modified ESCMs may be used to control the release of SMV and promote bone healing in GBR applications.

Keratocyte biology

The study of corneal stromal keratocytes is motivated by its strong association with corneal health and visual function. They play a dominant role in the maintenance of corneal homeostasis and transparency through the production of collagens, proteoglycans and corneal crystallins. Trauma-induced apoptosis of keratocytes and replacement by fibroblasts and myofibroblasts disrupt the stromal matrix organization, resulting in corneal haze formation and vision loss. It is, therefore, important to understand the biology and behaviours of keratocytes and the associated stromal cell types (like fibroblasts, myofibroblasts, stromal stem cells) in wound healing, corneal pathologies (including keratoconus, keratitis, endothelial disorders) as well as different ophthalmic situations (such as collagen crosslinking/photodynamic treatment, keratoplasty and refractive surgery, and topical medications). The recent development of ex vivo propagation of keratocytes and stromal stem cells, and their translational applications, either via stromal injection or incorporated in bioscaffold, have been shown to restore the corneal transparency and regenerate native stromal tissue in animal models of corneal haze and other disorders.

Bone Diseases: Current Approach and Future Perspectives in Drug Delivery Systems for Bone Targeted Therapeutics

Bone diseases include a wide group of skeletal-related disorders that cause mobility limitations and mortality. In some cases, e.g., in osteosarcoma (OS) and metastatic bone cancer, current treatments are not fully effective, mainly due to low patient compliance and to adverse side effects. To overcome these drawbacks, nanotechnology is currently under study as a potential strategy allowing specific drug release kinetics and enhancing bone regeneration. Polymers, ceramics, semiconductors, metals, and self-assembled molecular complexes are some of the most used nanoscale materials, although in most cases their surface properties need to be tuned by chemical or physical reactions. Among all, scaffolds, nanoparticles (NPs), cements, and hydrogels exhibit more advantages than drawbacks when compared to other nanosystems and are therefore the object of several studies. The aim of this review is to provide information about the current therapies of different bone diseases focusing the attention on new discoveries in the field of targeted delivery systems. The authors hope that this paper could help to pursue further directions about bone targeted nanosystems and their application for bone diseases and bone regeneration.

Injectable calcium phosphate foams for the delivery of Pitavastatin as osteogenic and angiogenic agent

Apatitic bone cements have been used as a clinical bone substitutes and drug delivery vehicles for therapeutic agents in orthopedic applications. This has led to their combination with different drugs with known ability to foster bone formation. Recent studies have evaluated Simvastatin for its role in enhanced bone regeneration, but its lipophilicity hampers incorporation and release to and from the bone graft. In this study, injectable calcium phosphate foams (i-CPF) based on α-tricalcium phosphate were loaded for the first time with Pitavastatin. The stability of the drug in different conditions relevant to this study, the effect of the drug on the i-CPFs properties, the release profile, and the in vitro biological performance with regard to mineralization and vascularization were investigated. Pitavastatin did not cause any changes in neither the micro nor the macro structure of the i-CPFs, which retained their biomimetic features. PITA-loaded i-CPFs showed a dose-dependent drug release, with early stage release kinetics clearly affected by the evolving microstructure due to the setting of cement. in vitro studies showed dose-dependent enhancement of mineralization and vascularization. Our findings contribute towards the design of controlled release with low drug dosing bone grafts: i-CPFs loaded with PITA as osteogenic and angiogenic agent.

Calcareous Foraminiferal Shells as a Template for the Formation of Hierarchal Structures of Inorganic Nanomaterials

A microorganism template approach has been explored for the fabrication of various well-defined three-dimensional (3D) structures. However, most of these templates suffer from small size (few μm), difficulty to remove the template, or low surface area, which affect their potential use in different applications or makes industrial scale-up difficult. Conversely, foraminifer's microorganisms are large (up to 200 mm), consist of CaCO₃ (easy to dissolve in mild acid), and have a relatively high surface area (≈5 m² g^-1). Herein, we demonstrate the formation of hierarchical structures of inorganic materials using calcareous foraminiferal shells such as Sorites, Globigerinella siphonifera, Lox-ostomina amygdaleformis, Calcarina baculatus or hispida, and Peneroplis planatus. Several techniques, such as thermal decomposition of single-source precursors of metal oxides or sulfides, reduction of metal salts directly on the surfaces, and redox reactions, were used for coating of different shell materials and several hybrid compositions, which possess nanofeatures. Finally, we examined the role of the prepared 3D structures on the reduction of 4-nitrophenol (4-NP), ethanol electrooxidation, and water purification. A remarkable performance was achieved in each application. The hierarchical structure leads to the reduction of 4-NP within several minutes, a 27 mA cm^-2 current density peak was obtained for ethanol electrooxidation, and more than 95% of the organic dye contaminants were successfully removed. These results show that using foraminiferal shells offers a new way for designing complex hierarchical structures with unique properties.

Bioinspired Hierarchical Porous Structures for Engineering Advanced Functional Inorganic Materials

Tremendous efforts have been directed at designing functional and well-defined 3D structures in recent decades. Many approaches have been devised and are currently used to create 3D structures, including lithography, 3D printing, assembly, and template-mediated (natural or synthetic) methods. Natural scaffolds offer some unique traits, as compared to their artificial counterparts, presenting highly ordered, porous, identical, abundant, and diverse structures. Various organisms, such as viruses, bacteria, diatoms, foraminifera, and others, are used as templates to form 3D structures. Herein, advancements made in using the shell of marine microorganisms, diatoms, and foraminifera, as scaffolds for designing functional 3D structures are reported. Furthermore, a succinct overview of various synthetic methods used to coat these scaffolds with inorganic materials (i.e., metals, metal oxides, and metal sulfides) is provided. Finally, the use of such fabricated functional 3D structures in a wide range of applications, such as catalysis, sensing, drug delivery, photo-electrochemical uses, batteries, and others, is considered.

Role of Simvastatin on fracture healing and osteoporosis: a systematic review on in vivo investigations

Simvastatin is a lipid lowering drug whose beneficial role on bone metabolism was discovered in 1999. Several in vivo studies evaluated its role on osteoporosis and fracture healing, however, controversial results are seen in the literature. For this reason, Simvastatin has not been the focus of any clinical trials as yet. This systematic review clears the mechanisms of action of Simvastatin on bone metabolism and focuses on in vivo investigations that have evaluated its role on osteoporosis and fracture repair to find out (i) whether Simvastatin is effective on treatment of osteoporosis and fracture repair, and (ii) which of the many available protocols may have the ability to be translated in the clinical setting. Simvastatin induces osteoinduction by increasing osteoblast activity and differentiation and inhibiting their apoptosis. It also reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts and their differentiation. Controversial results between the in vivo studies are mostly due to the differences in the route of administration, dose, dosage and carrier type. Local delivery of Simvastatin through controlled drug delivery systems with much lower doses and dosages than the systemic route seems to be the most valuable option in fracture healing. However, systemic delivery of Simvastatin with much higher doses and dosages than the clinical ones seems to be effective in managing osteoporosis. Simvastatin, in a particular range of doses and dosages, may be beneficial in managing osteoporosis and fracture injuries. This review showed that Simvastatin is effective in the treatment of osteoporosis and fracture healing.

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

Evolving marine biomimetics for regenerative dentistry

New products that help make human tissue and organ regeneration more effective are in high demand and include materials, structures and substrates that drive cell-to-tissue transformations, orchestrate anatomical assembly and tissue integration with biology. Marine organisms are exemplary bioresources that have extensive possibilities in supporting and facilitating development of human tissue substitutes. Such organisms represent a deep and diverse reserve of materials, substrates and structures that can facilitate tissue reconstruction within lab-based cultures. The reason is that they possess sophisticated structures, architectures and biomaterial designs that are still difficult to replicate using synthetic processes, so far. These products offer tantalizing pre-made options that are versatile, adaptable and have many functions for current tissue engineers seeking fresh solutions to the deficiencies in existing dental biomaterials, which lack the intrinsic elements of biofunctioning, structural and mechanical design to regenerate anatomically correct dental tissues both in the culture dish and in vivo.

Bone regeneration of calvarial defect using marine calcareous-derived beta-tricalcium phosphate macrospheres

The aim of this study was to examine the bone regeneration properties of beta-tricalcium phosphate hydrothermally converted from foraminifera carbonate exoskeleton in the repair of rat calvarial defect. These natural materials possess unique interconnected porous network with uniform pore size distribution, which can be potentially advantageous. In total, 20 adult male Wistar rats received full-thickness calvarial defect with a diameter of 5 mm. The rate of newly formed bone was measured radiologically by X-ray and micro-computed tomography and by histologic examination. After 2 weeks, the beta-tricalcium phosphate group exhibited full closure of the defect site, while control group remained unrestored at the end of the 6-week experimentation. It was observed that the newly regenerated bone thickened over the course of the experiment in the beta-tricalcium phosphate group. No soft tissue reaction was observed around the beta-tricalcium phosphate implant and the rats remained healthy. These results showed that repair of the calvarial defect can be achieved by biomimetic beta-tricalcium phosphate macrospheres, which hold potential for application as bone grafts for bone augmentation surgeries.

Bone regeneration of rat tibial defect by zinc-tricalcium phosphate (Zn-TCP) synthesized from porous Foraminifera carbonate macrospheres

Foraminifera carbonate exoskeleton was hydrothermally converted to biocompatible and biodegradable zinc-tricalcium phosphate (Zn-TCP) as an alternative biomimetic material for bone fracture repair. Zn-TCP samples implanted in a rat tibial defect model for eight weeks were compared with unfilled defect and beta-tricalcium phosphate showing accelerated bone regeneration compared with the control groups, with statistically significant bone mineral density and bone mineral content growth. CT images of the defect showed restoration of cancellous bone in Zn-TCP and only minimal growth in control group. Histological slices reveal bone in-growth within the pores and porous chamber of the material detailing good bone-material integration with the presence of blood vessels. These results exhibit the future potential of biomimetic Zn-TCP as bone grafts for bone fracture repair.