Silicon effect on the composition and structure of nanocalcium phosphates: In vitro biocompatibility to human osteoblasts

Remineralization Induced by Biomimetic Hydroxyapatite Toothpastes on Human Enamel

This work aimed to compare the effect of four new toothpastes (P1-P4) based on pure and biomimetic substituted nano-hydroxyapatites (HAPs) on remineralization of human enamel. Artificially demineralized enamel slices were daily treated for ten days with different toothpastes according to the experimental design. Tooth enamel surfaces were investigated using atomic force microscope (AFM) images and surface roughness (Ra) determined before and after treatment. The surface roughness of enamel slices was statistically analyzed by one-way ANOVA and Bonferroni's multiple comparison test. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) data revealed the HAP structure with crystal sizes between 28 and 33 nm and crystallinity between 29 and 37%. The average size of HAP particles was found to be between 30 and 40 nm. The Ra values indicated that P3 (HAP-Mg-Zn-Sr-Si) toothpaste was the most effective after 10 days of treatment, leading to the lowest mean roughness. The P3 and P2 (HAP) toothpastes were found to be effective in promoting remineralization. Specifically, their effectiveness can be ranked as follows: P3 = P2 > P4 (HAP-Mg-Zn-Si) > P1 (HAP-Zn), considering both the chemical composition and the size of their constitutive nanoparticles. The proposed toothpastes might be used successfully to treat early tooth decay.

Recent Trends in Hydroxyapatite Supplementation for Osteoregenerative Purposes

Bone regeneration has gained attention in the biomedical field, which has led to the development of materials and synthesis methods meant to improve osseointegration and cellular bone activity. The properties of hydroxyapatite, a type of calcium phosphate, have been researched to determine its advantages for bone tissue engineering, particularly its biocompatibility and ability to interact with bone cells. Recently, the advantages of utilizing nanomolecules of hydroxyapatite, combined with various substances, in order to enhance and combine their characteristics, have been reported in the literature. This review will outline the cellular and molecular roles of hydroxypatite, its interactions with bone cells, and its nano-combinations with various ions and natural products and their effects on bone growth, development, and bone repair.

From Basic Science to Clinical Perfection: What Defines the Orthopedic Biocompatible Implant?

The general improvement in life expectancy and standard of living makes it easier for patients to get access to routine medical exams and is anticipated to increase the prevalence of several degenerative joint illnesses. In addition, it is anticipated that their incidence will increase both nationally and internationally, which will raise the demand for novel and long-lasting implantable devices in the field of orthopedics. The current review’s goals are to define what constitutes a biocompatible orthopedic implant in terms of in vitro biocompatibility testing and to clarify important concepts and definitions that are already in use. The demand for materials and implants made of various tissues is now increasing, and the ongoing advancement of in vitro cell culture studies is a reliable practical tool for examining the biocompatibility of potential implantable materials. In vitro biocompatibility research has been reduced and, in most cases, diminished to laboratory studies that no longer or drastically reduce animal sacrifice as a response to the well-known three “Rs” (“reduction”, “refinement”, and “replacement”) introduced to literature by English academics in the 1960s. As technology advances at an astounding rate, a new generation of gene-activating biomaterials tailored for specific people and disease conditions might emerge in the near future.

Biomimetic Composite Coatings for Activation of Titanium Implant Surfaces: Methodological Approach and In Vivo Enhanced Osseointegration

Innovative nanomaterials are required for the coatings of titanium (Ti) implants to ensure the activation of Ti surfaces for improved osseointegration, enhanced bone fracture healing and bone regeneration. This paper presents a systematic investigation of biomimetic composite (BC) coatings on Ti implant surfaces in a rat model of a diaphyseal femoral fracture. Methodological approaches of surface modification of the Ti implants via the usual joining methods (e.g., grit blasting and acid etching) and advanced physicochemical coating via a self-assembled dip-coating method were used. The biomimetic procedure used multi-substituted hydroxyapatite (ms-HAP) HAP-1.5 wt% Mg-0.2 wt% Zn-0.2 wt% Si nanoparticles (NPs), which were functionalized using collagen type 1 molecules (COL), resulting in ms-HAP/COL (core/shell) NPs that were embedded into a polylactic acid (PLA) matrix and finally covered with COL layers, obtaining the ms-HAP/COL@PLA/COL composite. To assess the osseointegration issue, first, the thickness, surface morphology and roughness of the BC coating on the Ti implants were determined using AFM and SEM. The BC-coated Ti implants and uncoated Ti implants were then used in Wistar albino rats with a diaphyseal femoral fracture, both in the absence and the presence of high-frequency pulsed electromagnetic shortwave (HF-PESW) stimulation. This study was performed using a bone marker serum concentration and histological and computer tomography (micro-CT) analysis at 2 and 8 weeks after surgical implantation. The implant osseointegration was evaluated through the bone–implant contact (BIC). The bone–implant interface was investigated using FE-SEM images and EDX spectra of the retrieved surgical implants at 8 weeks in the four animal groups. The obtained results showed significantly higher bone–implants contact and bone volume per tissue volume, as well as a greater amount of newly formed bone, in the BC-coated Ti implants than in the uncoated Ti implants. Direct bone–implant contact was also confirmed via histological examination. The results of this study confirmed that these biomimetic composite coatings on Ti implants were essential for a significant enhancement of osseointegration of BC-coated Ti implants and bone regeneration. This research provides a novel strategy for the treatment of bone fractures with possible orthopedic applications.

Hydroxyapatite-collagen nanoparticles reinforced polyanhydride based injectable paste for bone substitution: effect of dopant addition in vitro

The present study focuses on the synthesis and characterization of hydroxyapatite-collagen nanoparticles incorporated polyanhydride paste and investigating its bone regeneration capacity in vitro. Photocrosslinkable polyanhydride paste was prepared after synthesizing methacrylate derivatives of 1,6-bis(p-carboxyphenoxy)hexane (MCPH) and sebacic acid dimethacrylate (MSA). These multifunctional monomers, namely 45 wt% MSA, 45 wt% MCPH in addition to 10 wt% poly(ethylene glycol)diacrylate (PEGDA) were photopolymerized under ultraviolet light (365 nm) to produce highly crosslinked polyanhydride networks using camphroquinone (CQ)/ethyl 4-(dimethylamino)benzoate [4-EDMAB] for light initiated crosslinking and benzoyl peroxide (BPO)/dimethyl toludine (DMT) for chemically initiated crosslinking. Separately, using the co-precipitation process, (1 wt%) Si, (1 wt%) Sr, and (0.5 + 0.5) wt% Si/Sr was doped into hydroxyapatite-collagen nanoparticles in size range between 50 and 70 nm. Si, Sr, and both Si/Sr doped hydroxyapatite-collagen nanoparticles to the extent 10 wt% were added to polyanhydride monomer mixture containing 40 wt% MSA, 40 wt% MCPH and 10 wt% PEGDA and subsequently photopolymerized as previously mentioned. Incorporation of hydroxyapatite-collagen nanoparticles to the extent of 10 wt% into polyanhydride matrix enhanced compressive strength of the hardened paste from 30 to 49 MPa. Mesenchymal stem cells obtained from the human umbilical cord were cultured onto pure polyanhydride and hydroxyapatite-collagen added scaffold to assess their cellular proliferation and differentiation capacity to bone cell. MTT assay showed that mesenchymal stem cell proliferation was significantly higher in Si/Sr binary doped hydroxyapatite-collagen-polyanhydride sample as compared to other samples. Again from immunocytochemistry study using confocal images suggested that expression of osteocalcin, a marker indicating differentiation into osteoblast, was the highest in Si/Sr binary doped hydroxyapatite-collagen-polyanhydride sample against the other samples studied in this case. This study thus summarizes the development of photocurable biocomposites containing polyanhydride and Si, Sr doped hydroxyapatite-collagen nanoparticles that exhibited tremendous promise to regenerate bone tissues in complex-shaped musculoskeletal defect sites.

Ion release from hydroxyapatite and substituted hydroxyapatites in different immersion liquids: in vitro experiments and theoretical modelling study

Multi-substituted hydroxyapatites (ms-HAPs) are currently gaining more consideration owing to their multifunctional properties and biomimetic structure, owning thus an enhanced biological potential in orthopaedic and dental applications. In this study, nano-hydroxyapatite (HAP) substituted with multiple cations (Sr2+, Mg2+ and Zn2+) for Ca2+ and anion ( Si O 4 4 - ) for P O 4 3 - and OH-, specifically HAPc-5%Sr and HAPc-10%Sr (where HAPc is HAP-1.5%Mg-0.2%Zn-0.2%Si), both lyophilized non-calcined and lyophilized calcined, were evaluated for their in vitro ions release. These nanomaterials were characterized by scanning electron microscopy, field emission-scanning electron microscopy and energy-dispersive X-ray, as well as by atomic force microscope images and by surface specific areas and porosity. Further, the release of cations and of phosphate anions were assessed from nano-HAP and ms-HAPs, both in water and in simulated body fluid, in static and simulated dynamic conditions, using inductively coupled plasma optical emission spectrometry. The release profiles were analysed and the influence of experimental conditions was determined for each of the six nanomaterials and for various periods of time. The pH of the samples soaked in the immersion liquids was also measured. The ion release mechanism was theoretically investigated using the Korsmeyer-Peppas model. The results indicated a mechanism principally based on diffusion and dissolution, with possible contribution of ion exchange. The surface of ms-HAP nanoparticles is more susceptible to dissolution into immersion liquids owing to the lattice strain provoked by simultaneous multi-substitution in HAP structure. According to the findings, it is rational to suggest that both materials HAPc-5%Sr and HAPc-10%Sr are bioactive and can be potential candidates in bone tissue regeneration.

Physiological silicon incorporation into bone mineral requires orthosilicic acid metabolism to SiO44

Under physiological conditions, the predominant form of bioavailable silicon (Si) is orthosilicic acid (OSA). In this study, given Si's recognized positive effect on bone growth and integrity, we examined the chemical form and position of this natural Si source in the inorganic bone mineral hydroxyapatite (HA). X-ray diffraction (XRD) of rat tibia bone mineral showed that the mineral phase was similar to that of phase-pure HA. However, theoretical XRD patterns revealed that at the levels found in bone, the 'Si effect' would be virtually undetectable. Thus we used first principles density functional theory calculations to explore the energetic and geometric consequences of substituting OSA into a large HA model. Formation energy analysis revealed that OSA is not favourable as a neutral interstitial substitution but can be incorporated as a silicate ion substituting for a phosphate ion, suggesting that incorporation will only occur under specific conditions at the bone-remodelling interface and that dietary forms of Si will be metabolized to simpler chemical forms, specifically [Formula: see text]. Furthermore, we show that this substitution, at the low silicate concentrations found in the biological environment, is likely to be a driver of calcium phosphate crystallization from an amorphous to a fully mineralized state.

Advanced Mg, Zn, Sr, Si Multi-Substituted Hydroxyapatites for Bone Regeneration

Purpose

Compositional tailoring is gaining more attention in the development of advanced biomimetic nanomaterials. In this study, we aimed to prepare advanced multi-substituted hydroxyapatites (ms-HAPs), which show similarity with the inorganic phase of bones and might have therapeutic potential for bone regeneration.

Materials

Novel nano hydroxyapatites substituted simultaneously with divalent cations: Mg²⁺ (1.5%), Zn²⁺ (0.2%), Sr²⁺ (5% and 10%), and Si (0.2%) as orthosilicate (SiO₄^4-) were designed and successfully synthesized for the first time.

Methods

The ms-HAPs were obtained via a wet-chemistry precipitation route without the use of surfactants, which is a safe and ecologically friendly method. The composition of synthesized materials was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The materials were characterized by X-ray powder diffraction (XRD), FT-IR and FT-Raman spectroscopy, BET measurements and by imaging techniques using high-resolution TEM (HR-TEM), FE-SEM coupled with EDX, and atomic force microscopy (AFM). The ion release was measured in water and in simulated body fluid (SBF).

Results

Characterization methods confirmed the presence of the unique phase of pure stoichiometric HAP structure and high compositional purity of all synthesized nanomaterials. The doping elements influenced the crystallite size, the crystallinity, lattice parameters, morphology, particle size and shape, specific surface area, and porosity. Results showed a decrease in both nanoparticle size and crystallinity degree, coupled with an increase in specific surface area of these advanced ms-HAP materials, in comparison with pure stoichiometric HAP. The release of biologically important ions was confirmed in different liquid media, both in static and simulated dynamic conditions.

Conclusion

The incorporation of the four substituting elements into the HAP structure is demonstrated. Synthesized nanostructured ms-HAP materials might inherit the in vivo effects of substituting functional elements and properties of hydroxyapatite for bone healing and regeneration. Results revealed a rational tailoring approach for the design of a next generation of bioactive ms-HAPs as promising candidates for bone regeneration.

Elaboration and Biocompatibility of an Eggshell-Derived Hydroxyapatite Material Modified with Si/PLGA for Bone Regeneration in Dentistry

Hydroxyapatite (HAp) is the most commonly used biomaterial in modern bone regeneration studies because of its chemical similarity to bone, biocompatibility with different polymers, osteoconductivity, low cost, and lack of immune response. However, to overcome the disadvantages of HAp, which include fragility and low mechanical strength, current studies typically focus on property modification through the addition of other materials. Objective. To develop and evaluate the biocompatibility of a HAp material extracted from eggshells and modified with silicon (Si) and poly(lactic-co-glycolic) acid (PLGA). Materials and Methods. An in vitro experimental study in which a HAp material prepared from eggshells was synthesized by wet chemical and conventional chemical precipitation. Subsequently, this material was reinforced with Si/PLGA using the freezing/lyophilization method, and then osteoblast cells were seeded on the experimental material (HAp/Si/PLGA). To analyse the biocompatibility of this composite material, scanning electron microscopy (SEM) and fluorescence confocal microscopy (FCM) techniques were used. PLGA, bovine bone/PLGA (BB/PLGA), and HAp/PLGA were used as controls. Results. A cellular viability of 96% was observed for the experimental HAp/Si/PLGA material as well as for the PLGA. The viability for the BB/PLGA material was 90%, and the viability for the HAp/PLGA was 86%. Cell adhesion was observed on the exterior surface of all materials. However, a continuous monolayer and the presence of filopodia were observed over both external and internal surface of the experimental materials. Conclusions. The HAp/Si/PLGA material is highly biocompatible with osteoblastic cells and can be considered promising for the construction of three-dimensional scaffolds for bone regeneration in dentistry.

Enhancement of bone consolidation using high-frequency pulsed electromagnetic short-waves and titanium implants coated with biomimetic composite embedded into PLA matrix: in vivo evaluation

Purpose

Bone consolidation after severe trauma is the most challenging task in orthopedic surgery. This study aimed to develop biomimetic composite for coating Ti implants. Afterwards, these implants were tested in vivo to assess bone consolidation in the absence or the presence of high-frequency pulsed electromagnetic short-waves (HF-PESW).

Materials

Biomimetic coating was successfully developed using multi-substituted hydroxyapatite (ms-HAP) functionalized with collagen (ms-HAP/COL), embedded into poly-lactic acid (PLA) matrix (ms-HAP/COL@PLA), and subsequently covered with self-assembled COL layer (ms-HAP/COL@PLA/COL, named HAPc).

Methods

For in vivo evaluation, 32 Wistar albino rats were used in four groups: control group (CG) with Ti implant; PESW group with Ti implant+HF-PESW; HAPc group with Ti implant coated with HAPc; HAPc+PESW group with Ti implant coated with HAPc+HF-PESW. Left femoral diaphysis was fractured and fixed intramedullary. From the first post-operative day, PESW and HAPc+PESW groups underwent HF-PESW stimulation for 14 consecutive days. Biomimetic coating was characterized by XRD, HR-TEM, SEM, EDX and AFM.

Results

Osteogenic markers (ALP and osteocalcin) and micro-computed tomography (CT) analysis (especially bone volume/tissue volume ratio results) indicated at 2 weeks the following group order: HAPc+PESW>HAPc≈PESW (P>0.05) and HAPc+PESW>control (P<0.05), indicating the higher values in HAPc+PESW group compared to CG. The fracture-site bone strength showed, at 2 weeks, the highest average value in HAPc+PESW group. Moreover, histological analysis revealed the most abundant COL fibers assembled in dense bundles in HAPc-PESW group. At 8 weeks, micro-CT indicated higher values only in HAPc+PESW group vs CG (P<0.05), and histological results showed a complete-healed fracture in groups: HAPc+PESW, HAPc and PESW, but with more advanced bone remodeling in HAPc+PESW group.

Conclusion

Using Ti implants coated by HAPc jointly with HF-PESW stimulation positively influenced the bone consolidation process, especially in its early phase, thus potentially providing a superior strategy for clinical applications.

Scaffolding Strategies for Tissue Engineering and Regenerative Medicine Applications

During the past two decades, tissue engineering and the regenerative medicine field have invested in the regeneration and reconstruction of pathologically altered tissues, such as cartilage, bone, skin, heart valves, nerves and tendons, and many others. The 3D structured scaffolds and hydrogels alone or combined with bioactive molecules or genes and cells are able to guide the development of functional engineered tissues, and provide mechanical support during in vivo implantation. Naturally derived and synthetic polymers, bioresorbable inorganic materials, and respective hybrids, and decellularized tissue have been considered as scaffolding biomaterials, owing to their boosted structural, mechanical, and biological properties. A diversity of biomaterials, current treatment strategies, and emergent technologies used for 3D scaffolds and hydrogel processing, and the tissue-specific considerations for scaffolding for Tissue engineering (TE) purposes are herein highlighted and discussed in depth. The newest procedures focusing on the 3D behavior and multi-cellular interactions of native tissues for further use for in vitro model processing are also outlined. Completed and ongoing preclinical research trials for TE applications using scaffolds and hydrogels, challenges, and future prospects of research in the regenerative medicine field are also presented.

Structural and crystal-chemical characteristics of the apatite deposits from human aortic walls

Thermal behavior of biological apatite is the object of several studies. Crystal size, carbonate content, phase composition, and other parameters change during annealing up to 900 °C in biological minerals with apatite structure. The way these parameters change reflects the specific properties of the initial bioapatite. This work presents data on thermal transformations of pathological bioapatite from the human cardiovascular system, namely aortic wall deposits. Some minor elements, foreign to calcium hydroxyapatite (e.g., Na and Mg), can be both incorporated in the apatite structure and localized in the surface layers of crystals, modifying functions of the mineral. A new approach was proposed to determine the predominant location of minor elements, such as Mg, Na, and K, in the mineral of pathological deposits. Mg and Na in pathological apatite can be in both structurally bound (substituting calcium in lattice) and labile (localized on the crystal surface) states, while K is not able to join the apatite structure in significant amount or be chemically bound to it. This approach, based on atomic spectrometry, can be used effectively in combination with a set of traditional techniques, such as like EDS, IRS, and XRD.

Ultralong Hydroxyapatite Nanowires-Based Paper Co-Loaded with Silver Nanoparticles and Antibiotic for Long-Term Antibacterial Benefit

Hydroxyapatite is a kind of biocompatible, environmentally friendly, and versatile inorganic biomaterial. Herein, the preparation of ultralong hydroxyapatite nanowires (HAPNWs)-based antibacterial paper co-loaded with silver nanoparticles (AgNPs) and antibiotic is reported. HAPNWs are used to prepare AgNPs in situ using an aqueous solution containing AgNO₃ under the sunlight without added reducing agent at room temperature. Subsequently, ciprofloxacin (CIP) as an antibiotic is loaded on the HAPNWs@AgNPs. The resultant HAPNWs@AgNPs-CIP paper possesses several unique properties, including high flexibility, high Brunauer-Emmett-Teller (BET) specific surface area (47.9 m² g^-1), high drug loading capacity (447.4 mg g^-1), good biocompatibility, sustained and pH-responsive drug release behavior (5.40-6.75% of Ag⁺ ions and 37.7-76.4% of CIP molecules at pH values of 7.4-4.5 at day 8, respectively), and reusable recycling. In the antibacterial tests against Escherichia coli and Staphylococcus aureus, the HAPNWs@AgNPs-CIP paper exhibits large diameters of inhibition zones and low minimum inhibitory concentrations (30 and 40 μg mL^-1), revealing the high antibacterial activity. Besides, the consecutive agar diffusion tests (8 cycles), long-term stability tests (over 56 days), and continuous contamination tests (5 cycles) demonstrate the excellent recycling performance and long-term antibacterial activity of the HAPNWs@AgNPs-CIP paper. These results indicate a promising potential of the HAPNWs@AgNPs-CIP bactericidal paper for tackling public health issues related to bacterial infections.

Properties of CaO-SiO2-P2O5 reinforced calcium phosphate cements and in vitro osteoblast response

Non-cytotoxic and bioactive tetracalcium phosphate/nanomonetite/calcium silicate-phosphate cements were prepared by simple mechanical mixing of starting powder precursors based on acid or basic tetracalcium phosphate/nanomonetite mixtures with 1 or 5 wt% addition of precititated amorphous or crystalline calcium silicate phosphate phases. The small additions (1-2 wt%) of crystalline CaSiP phase caused about a two-fold rise in the compressive strength of cements (up to 70 MPa) with simultaneous preservation of short setting time (around 5 min) and refinement of nanohydroxyapatite particles in microstructure. The results verified a close pH to body fluids and enhanced steady state concentrations of Ca²⁺, silicate and phosphate ions during the soaking of acid than the basic composite mixtures in physiological solution. No cytotoxicity or suppressing in proliferation activity of osteoblasts were revealed after the addition of CaSiP phases to cement powder mixtures. The ALP activity of osteoblasts during the first two days of culture on all composite systems was significantly higher than on pure tetracalcium phosphate/nanomonetite substrates. The superior enhancing in ALP osteoblast activity was found on cements with amorphous CaSiP glass component (even at low contents), which confirms excellent in vitro osteoblast activity on composites and their possible utilization as bone cements in reconstruction medicine.

Synthesis of trace element Si and Sr codoping hydroxyapatite with non-cytotoxicity and enhanced cell proliferation and differentiation

The main inorganic minerals in natural bones are non-stoichiometric hydroxyapatite (HA, Ca₁₀[PO₄]₆[OH]₂) doped with various trace elements, which may possess important biochemical effects. To investigate the functions of Sr and Si elements in human hard tissues, non-doped HA, trace Si doped HA, Si and Sr codoped HA with the concentration of natural bones are synthesized by hydrothermal method in this study. The samples are characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The biological activities are evaluated via cytotoxicity study, adhesion and proliferation of osteoblast measurement, and alkaline phosphatase (ALP) assay. All the synthesized materials are HA phase, which have hierarchical structures with oriented HA nanorods assembled into the platy particles. These materials are non-cytotoxic against L929 cells line even at 400 μg/ml powder suspension. The results clearly indicate that the proliferation of L929 cells increases with trace elements doping from trace Si-HA to Si + Sr-HA. The adhesion and proliferation of osteoblast measurement illustrates that proliferation of osteoblasts advances about 1.3 times for Si-HA and about 1.8 times for Si + Sr-HA compared with undoped HA. In general, Si-HA with trace Si element shows enhanced cell differentiation, and Si + Sr-HA dual-doped with Si and Sr elements presents increased biological activity compared with Si-HA.

Stimulation of osteogenesis and angiogenesis of hBMSCs by delivering Si ions and functional drug from mesoporous silica nanospheres

Multifunctional bioactive materials with the ability to stimulate osteogenesis and angiogenesis of stem cells play an important role in the regeneration of bone defects. However, how to develop such biomaterials remains a significant challenge. In this study, we prepared mesoporous silica nanospheres (MSNs) with uniform sphere size (∼90 nm) and mesopores (∼2.7 nm), which could release silicon ions (Si) to stimulate the osteogenic differentiation of human bone marrow stromal cells (hBMSCs) via activating their ALP activity, bone-related gene and protein (OCN, RUNX2 and OPN) expression. Hypoxia-inducing therapeutic drug, dimethyloxaloylglycine (DMOG), was effectively loaded in the mesopores of MSNs (D-MSNs). The sustained release of DMOG from D-MSNs could stabilize HIF-1α and further stimulated the angiogenic differentiation of hBMSCs as indicated by the enhanced VEGF secretion and protein expression. Our study revealed that D-MSNs could combine the stimulatory effect on both osteogenic and angiogenic activity of hBMSCs. The potential mechanism of D-MSN-stimulated osteogenesis and angiogenesis was further elucidated by the supplementation of cell culture medium with pure Si ions and DMOG. Considering the easy handling characteristics of nanospheres, the prepared D-MSNs may be applied in the forms of injectable spheres for minimally invasive surgery, or MSNs/polymer composite scaffolds for bone defect repair. The concept of delivering both stimulatory ions and functional drugs may offer a new strategy to construct a multifunctional biomaterial system for bone tissue regeneration.

Natural-based nanocomposites for bone tissue engineering and regenerative medicine: a review

Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional substitutes aimed to repair and regenerate damaged tissues and organs. Inspired by the hierarchical nature of bone, nanostructured biomaterials are gaining a singular attention for tissue engineering, owing their ability to promote cell adhesion and proliferation, and hence new bone growth, compared with conventional microsized materials. Of particular interest are nanocomposites involving biopolymeric matrices and bioactive nanosized fillers. Biodegradability, high mechanical strength, and osteointegration and formation of ligamentous tissue are properties required for such materials. Biopolymers are advantageous due to their similarities with extracellular matrices, specific degradation rates, and good biological performance. By its turn, calcium phosphates possess favorable osteoconductivity, resorbability, and biocompatibility. Herein, an overview on the available natural polymer/calcium phosphate nanocomposite materials, their design, and properties is presented. Scaffolds, hydrogels, and fibers as biomimetic strategies for tissue engineering, and processing methodologies are described. The specific biological properties of the nanocomposites, as well as their interaction with cells, including the use of bioactive molecules, are highlighted. Nanocomposites in vivo studies using animal models are also reviewed and discussed.

Incorporation of silica particles into decellularized tissue biomaterial and its effect on macrophage activation

Secretion of signaling molecules by macrophages is induced by silica particles deposited onto decellularized tissue derived biomaterials.