In vitro proliferation and differentiation of human bone marrow mesenchymal stem cells into osteoblasts on nanocomposite scaffolds based on bioactive glass (64SiO2-31CaO-5P2O5)-poly-l-lactic acid nanofibers fabricated by electrospinning method

Modification of titanium orthopedic implants with bioactive glass: a systematic review of in vivo and in vitro studies

Bioactive glasses (BGs) are ideal biomaterials in the field of bio-restoration due to their excellent biocompatibility. Titanium alloys are widely used as a bone graft substitute material because of their excellent corrosion resistance and mechanical properties; however, their biological inertness makes them prone to clinical failure. Surface modification of titanium alloys with bioactive glass can effectively combine the superior mechanical properties of the substrate with the biological properties of the coating material. In this review, the relevant articles published from 2013 to the present were searched in four databases, namely, Web of Science, PubMed, Embase, and Scopus, and after screening, 49 studies were included. We systematically reviewed the basic information and the study types of the included studies, which comprise in vitro experiments, animal tests, and clinical trials. In addition, we summarized the applied coating technologies, which include pulsed laser deposition (PLD), electrophoretic deposition, dip coating, and magnetron sputtering deposition. The superior biocompatibility of the materials in terms of cytotoxicity, cell activity, hemocompatibility, anti-inflammatory properties, bioactivity, and their good bioactivity in terms of osseointegration, osteogenesis, angiogenesis, and soft tissue adhesion are discussed. We also analyzed the advantages of the existing materials and the prospects for further research. Even though the current research status is not extensive enough, it is still believed that BG-coated Ti implants have great clinical application prospects.

Design and Manufacture of Bone Cements Based on Calcium Sulfate Hemihydrate and Mg, Sr-Doped Bioactive Glass

In the present study, a novel composite bone cement based on calcium sulfate hemihydrate (CSH) and Mg, Sr-containing bioactive glass (BG) as solid phase, and solution of chitosan as liquid phase were developed. The phase composition, morphology, setting time, injectability, viscosity, and cellular responses of the composites with various contents of BG (0, 10, 20, and 30 wt.%) were investigated. The pure calcium sulfate cement was set at approximately 180 min, whereas the setting time was drastically decreased to 6 min by replacing 30 wt.% glass powder for CSH in the cement solid phase. BG changed the microscopic morphology of the set cement and decreased the size and compaction of the precipitated gypsum phase. Replacing the CSH phase with BG increased injection force of the produced cement; however, all the cements were injected at a nearly constant force, lower than 20 N. The viscosity measurements in oscillatory mode determined the shear-thinning behavior of the pastes. Although the viscosity of the pastes increased with increasing BG content, it was influenced by the frequency extent. Pure calcium sulfate cement exhibited some transient cytotoxicity on human-derived bone mesenchymal stem cells and it was compensated by introducing BG phase. Moreover, BG improved the cell proliferation and mineralization of extracellular matrix as shown by calcein measurements. The results indicate the injectable composite cement comprising 70 wt.% CSH and 30 wt.% Mg, Sr-doped BG has better setting, mechanical and cellular behaviors and hence, is a potential candidate for bone repair, however more animal and human clinical evaluations are essential.

Fabrication of a gradient AZ91-bioactive glass composite with good biodegradability

This study used friction stir-back extrusion to fabricate the AZ91 + 3 wt% bioactive glass gradient composite wire. The microstructure, mechanical properties, and corrosion resistance of a material in a simulated body fluid were investigated. Three 2-mm diameter holes with varying hole patterns were drilled in the cross-section of the AZ91 rod to apply 3 wt % bioactive glass to the AZ91 matrix. The results demonstrated that the hole pattern strongly influenced the material's flow in the extruded wire's cross-section. By increasing the distance between the center of the initial rod and the center of the holes, a higher temperature and more uniform distribution of plastic strain are formed during friction stir back extrusion, resulting in uniform distribution of bioactive glass particles and α + β eutectic structure near the surface of composite wires. Introducing bioactive glass particles into the zone near the surface of the AZ91 rod results in the formation of a uniform distribution of bioactive glass particles near the surface and their absence in the central zone of the composite wire. A higher amount of discontinuous β-Mg17Al12 phase and α + β eutectic formed at the grain boundaries by increasing the temperature and plastic strain during friction stir-back extrusion. The crystallographic texture of the AZ91 rod changed from prismatic to basal and pyramidal due to the friction stir-back extrusion method. A gradient AZ91-bioactive glass composite wire with ultimate tensile strength, yield strength, elongation, and corrosion resistance 58, 64, 62, and 34%, respectively, greater than AZ91 as-cat rod can be produced by inserting bioactive glass powder using a hole drilling method and applying a friction stir back extrusion process.

Development of Photoluminescent and Photochromic Polyester Nanocomposite Reinforced with Electrospun Glass Nanofibers

A polyester resin was strengthened with electrospun glass nanofibers to create long-lasting photochromic and photoluminescent products, such as smart windows and concrete, as well as anti-counterfeiting patterns. A transparent glass@polyester (GLS@PET) sheet was created by physically immobilizing lanthanide-doped aluminate (LA) nanoparticles (NPs). The spectral analysis using the CIE Lab and luminescence revealed that the transparent GLS@PET samples turned green under ultraviolet light and greenish-yellow in the dark. The detected photochromism can be quickly reversed in the photoluminescent GLS@PET hybrids at low concentrations of LANPs. Conversely, the GLS@PET substrates with the highest phosphor concentrations exhibited sustained luminosity with slow reversibility. Transmission electron microscopic analysis (TEM) and scanning electron microscopy (SEM) were utilized to examine the morphological features of lanthanide-doped aluminate nanoparticles (LANPs) and glass nanofibers to display diameters of 7-15 nm and 90-140 nm, respectively. SEM, energy-dispersive X-ray spectroscopy (EDXA), and X-ray fluorescence (XRF) were used to analyze the luminous GLS@PET substrates for their morphology and elemental composition. The glass nanofibers were reinforced into the polyester resin as a roughening agent to improve its mechanical properties. Scratch resistance was found to be significantly increased in the created photoluminescent GLS@PET substrates when compared with the LANPs-free substrate. When excited at 368 nm, the observed photoluminescence spectra showed an emission peak at 518 nm. The results demonstrated improved hydrophobicity and UV blocking properties in the luminescent colorless GLS@PET hybrids.

A new hydrogel with fluorapatite nanoparticles for osteogenic differentiation of human adipose-derived stem cells in tissue engineering field

Since scaffolds are engineered to support functional tissue formation, their design and materials play an essential role in medical fields by providing different mechanical function. The aim of this study was to investigate the synthesis and structural characterization of collagen-gelatin (COL-GEL) composite scaffolds containing fluorapatite (FA) nanoparticles as well as evaluation of the osteogenic differentiation of human adipose-derived stem cells (hADSCs). First, the composite scaffolds were evaluated using Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The cytotoxicity of scaffolds and various concentrations of FA nanoparticles was studied through MTT assay and acridine orange/ethidium bromide staining. Next, the differentiated hADSCs were analyzed using Alizarin red and von Kossa staining, calcium content assay, alkaline phosphatase (ALP) activity, real-time RT-PCR, and immunocytochemical analyses. According to the characterization analyses, the composite scaffolds were properly integrated. The results also illustrated that COL-GEL composite scaffolds in the presence of FA nanoparticles not only showed no cytotoxicity but also increased ALP activity and calcium deposition as well as the expression of osteogenic genes, including Runx2, Col-I, ALP, and osteocalcin and the synthesis of proteins such as osteocalcin and osteopontin in vitro. The obtained data were confirmed by Alizarin red and von Kossa staining. These results are very promising for further tissue engineering experiments, in which FA nanoparticle incorporation into COL-GEL composite scaffolds is a novel approach that improves the surface COL-GEL composite scaffolds for tissue engineering application in vitro.

Effect of glutaraldehyde and calcium chloride as different crosslinking agents on the characteristics of chitosan/cellulose nanocrystals scaffold

The effect of glutaraldehyde and calcium cations as covalent and ionic crosslinkers was investigated on the main characteristics of scaffolds based on chitosan and cellulose nanocrystals. Therefore, four different scaffolds based on chitosan/cellulose nanocrystals with different crosslinking methods were fabricated using the freeze-drying method for potential use in bone tissue engineering. The structural and chemical features of prepared scaffolds were studied by the FTIR technique. FESEM images revealed that all scaffold samples are porous three-dimensional networks in which the pores are connected. TGA analysis showed that the thermal stability of scaffolds based on chitosan/cellulose nanocrystals has not been changed significantly by using different crosslinking methods. The chitosan/cellulose nanocrystals scaffold crosslinked by glutaraldehyde represented the highest compressive strength and the uncrosslinked scaffold showed the highest swelling ratio in comparison to the other scaffolds. The fastest degradation rate belonged to the scaffold crosslinked by calcium cations. FESEM images and EDX analysis confirmed that fabricated scaffolds have good biomineralization ability. The cell viability and cell attachment results indicated that all four scaffolds support cell proliferation and cell adhesion. However, the viability of NIH3T3 fibroblast cells in the presence of glutaraldehyde-containing scaffolds was lower than that of other scaffolds.

3D direct printing of composite bone scaffolds containing polylactic acid and spray dried mesoporous bioactive glass-ceramic microparticles

In this study, a three-dimensional composite scaffold is proposed consisting of polylactic acid and spray dried glass-ceramic microparticles (SGCMs). The compositional and structural characterization showed that the obtained spray dried powder formed as glass-ceramic (GC) with a completely interconnected porosity structure. Before direct printing of scaffolds, the rheological behavior of polylactic acid (PLA) and PLA-GC (PLA matrix containing SGCMs) inks were investigated. The PLA-GC composite ink represents sharper shear-thinning behavior and higher loss and storage modulus comparable to that of pure PLA. Microscopic observations and elemental mapping elements showed that 3D scaffolds had well-defined interconnected porosity and uniform distribution of the glass-ceramic particles. Mechanical tests indicated that compression strength is dependent on the scaffold porosity and the presence of SGCMs. Apatite formation evaluation besides ion release study showed better biomineralization capacity of PLA-GC scaffolds, as larger and denser sediments formed on the PLA-GC scaffolds after 7- and 14-day soaking. The preliminary cell response was studied with primary human mesenchymal stem cells (hMSCs) and revealed that SGCMs improved cell adhesion and viability and ALP activity. The appropriate combination of the biomaterials/methods to fabricate 3D porous constructs and their available bioactivity and biocompatibility, both being important characteristics for bone tissue engineering applications.

Enhancing glass ionomer cement features by using the calcium phosphate nanocomposite

This study showed the synthesis of Glass ionomer cements (GIC) modified with calcium phosphate nanoparticles (nCaP). The nCaP/GIC were submitted to mechanical compression and diametral tensile tests. The biocomposite were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Cytotoxicity and cell viability tests were performed on the human bone marrow mesenchymal stem cells using a 3-(4,5-dimethylthiazol-2yl)2,5-diphenyl- tetrazolium-bromide assay and LIVE/DEAD assays. Statistically significant differences were observed for mechanical properties (Kruskal-Wallis, p<0.001), nCaP/GIC showed higher resistance to compression and diametral traction. The SEM analyses revealed a uniform distribution nCaP in the ionomer matrix. The EDX and XRD results indicated that hydroxyapatite and calcium β-triphosphate phases. The FTIR spectra revealed the asymmetric band of ν3PO43- between 1100-1030cm-1 and the vibration band associated with ν1PO43- in 963cm-1 associated with nCaP. The nCaP/GIC presented response to adequate cell viability and non-cytotoxic behavior. Therefore, the new nCaP/GIC composite showed great mechanical properties, non-cytotoxic behavior, and adequate response to cell viability with promising dental applications.

A Comprehensive Review of the Development of Carbohydrate Macromolecules and Copper Oxide Nanocomposite Films in Food Nanopackaging

Background. Food nanopackaging helps maintain food quality against physical, chemical, and storage instability factors. Copper oxide nanoparticles (CuONPs) can improve biopolymers’ mechanical features and barrier properties. This will lead to antimicrobial and antioxidant activities in food packaging to extend the shelf life. Scope and Approach. Edible coatings based on carbohydrate biopolymers have improved the quality of packaging. Several studies have addressed the role of carbohydrate biopolymers and incorporated nanoparticles to enhance food packets’ quality as active nanopackaging. Combined with nanoparticles, these biopolymers create film coatings with an excellent barrier property against transmissions of gases such as O2 and CO2. Key Findings and Conclusions. This review describes the CuO-biopolymer composites, including chitosan, agar, cellulose, carboxymethylcellulose, cellulose nanowhiskers, carrageenan, alginate, starch, and polylactic acid, as food packaging films. Here, we reviewed different fabrication techniques of CuO biocomposites and the impact of CuONPs on the physical, mechanical, barrier, thermal stability, antioxidant, and antimicrobial properties of carbohydrate-based films.

Sol-Gel Synthesis, in vitro Behavior, and Human Bone Marrow-Derived Mesenchymal Stem Cell Differentiation and Proliferation of Bioactive Glass 58S

Background:

Bioactive glasses 58S, are silicate-based materials containing calcium and phosphate, which dissolved in body fluid and bond to the bone tissue. This type of bioactive glass is highly biocompatible and has a wide range of clinical applications.

Methods:

The 58S glass powders were synthesized via sol-gel methods, using tetraethyl orthosilicate, triethyl phosphate, and calcium nitrate, as precursors. Upon the analyses of phase and chemical structures of bioactive glass in different gelation times (12, 48, and 100 h), the appropriate heat treatment (at 525, 575, and 625 °C) was performed to eliminate nitrate compounds and stabilize the glass powder samples. The in vitro assay in SBF solution revealed the bioactivity of the synthesized 58S glass through the morphological (SEM), chemical structure (FTIR), release of calcium, phosphorous and silicon elements, pH variations, and weight loss measurements. The behavior of MSCs in the presence of bioactive glass powders was studied by MTT cytotoxicity, cell staining, ALP activity and biomineralization tests, as well as by the evaluation of ALP, osteocalcin, osteonectin, collagenI, and RUNX2 gene expression.

Results:

The results confirmed a gelation time of 100 h and a calcination temperature of 575 °C at optimal conditions for the synthesis of nitrate-free bioactive glass powders.

Conclusion:

The glass spherical nanoparticles in the range of 20-30 nm possess the improved bioactivity and osteogenic properties as demanded for bone tissue engineering.

Sol-Gel Synthesis, in vitro Behavior, and Human Bone Marrow-Derived Mesenchymal Stem Cell Differentiation and Proliferation of Bioactive Glass 58S

Background

Bioactive glasses 58S, are silicate-based materials containing calcium and phosphate, which dissolved in body fluid and bond to the bone tissue. This type of bioactive glass is highly biocompatible and has a wide range of clinical applications.

Methods

The 58S glass powders were synthesized via sol-gel methods, using tetraethyl orthosilicate, triethyl phosphate, and calcium nitrate, as precursors. Upon the analyses of phase and chemical structures of bioactive glass in different gelation times (12, 48, and 100 h), the appropriate heat treatment (at 525, 575, and 625 °C) was performed to eliminate nitrate compounds and stabilize the glass powder samples. The in vitro assay in SBF solution revealed the bioactivity of the synthesized 58S glass through the morphological (SEM), chemical structure (FTIR), release of calcium, phosphorous and silicon elements, pH variations, and weight loss measurements. The behavior of MSCs in the presence of bioactive glass powders was studied by MTT cytotoxicity, cell staining, ALP activity and biomineralization tests, as well as by the evaluation of ALP, osteocalcin, osteonectin, collagen I, and RUNX2 gene expression.

Results

The results confirmed a gelation time of 100 h and a calcination temperature of 575 °C at optimal conditions for the synthesis of nitrate-free bioactive glass powders.

Conclusion

The glass spherical nanoparticles in the range of 20-30 nm possess the improved bioactivity and osteogenic properties as demanded for bone tissue engineering.

Electrospinning of in situ synthesized silica-based and calcium phosphate bioceramics for applications in bone tissue engineering: A review

The field of bone tissue engineering (BTE) focuses on the repair of bone defects that are too large to be restored by the natural healing process. To that purpose, synthetic materials mimicking the natural bone extracellular matrix (ECM) are widely studied and many combinations of compositions and architectures are possible. In particular, the electrospinning process can reproduce the fibrillar structure of bone ECM by stretching a viscoelastic solution under an electrical field. With this method, nano/micrometer-sized fibres can be produced, with an adjustable chemical composition. Therefore, by shaping bioactive ceramics such as silica, bioactive glasses and calcium phosphates through electrospinning, promising properties for their use in BTE can be obtained. This review focuses on the in situ synthesis and simultaneous electrospinning of bioceramic-based fibres while the reasons for using each material are correlated with its bioactivity. Theoretical and practical considerations for the synthesis and electrospinning of these materials are developed. Finally, investigations into the in vitro and in vivo bioactivity of different systems using such inorganic fibres are exposed.

A comparative study of hBM-MSCs' differentiation toward osteogenic lineage in the presence of progesterone and estrogen hormones separately and concurrently in vitro

Promising cell sources for tissue engineering comprise bone marrow derived-mesenchymal stem cells (BM-MSCs) that have multiple differentiation potentials. Also, sex hormones act as important elements in bone development and maintenance, and the roles of two female sex steroid hormones known as estrogen (17-β estradiol) and progesterone in osteogenic differentiation of human BM-MSCs (hBM-MSCs) are studied. For this purpose, hBM-MSCs were treated with a 1 × 10^-6  M concentration of 17-β estradiol and progesterone separately and simultaneously while the optimum concentrations were obtained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Osteogenic differentiation tests including measurement of alkaline phosphatase (ALP) enzyme activity, the content of total mineral calcium, mineralized matrix staining by Alizarin Red and Von Kossa solutions, real-time reverse transcription polymerase chain reaction (RT-PCR), and immunofluorescence staining were carried out on Days 7 and 14 of differentiation. To exhibit the morphology of the cells, the BM-MSCs were stained with acridine orange (AO) solution. In this study, the results of ALP activity assay, calcium content and real-time RT-PCR assay and also all tests of differentiation staining have shown that 17-β estradiol has been recognized as an enhancing factor of osteogenic differentiation. Furthermore, MTT assay and AO staining revealed progesterone as a factor that seriously improved the proliferation of hBM-MSCs. Generally, the 17-β estradiol individually or in the presence of progesterone has more effects on BM-MSCs' osteogenic differentiation compared to progesterone alone. In this study, it is indicated that the effect of the 17-β estradiol and progesterone concurrently was the same as individual 17-β estradiol on the differentiation of hBM-MSCs.

The synergistic effects of SrF2 nanoparticles, YSZ nanoparticles, and poly-ε-l-lysin on physicomechanical, ion release, and antibacterial-cellular behavior of the flowable dental composites

Resin-based pit-and-fissure sealants (flowable resin composites) were formulated using bisphenol-A-glycerolatedimethacrylate (Bis-GMA)-triethylene glycol dimethacrylate-(TEGDMA)-diurethanedimethacrylate (UDMA) mixed monomers and multiple fillers, including synthetic strontium fluoride (SrF₂) nanoparticles as a fluoride-releasing and antibacterial agent, yttria-stabilized zirconia (YSZ) nanoparticles as an auxiliary filler, and poly-ε-l-lysin (ε-PL) as an auxiliary antibacterial agent. Based on the physical, mechanical and initial antibacterial properties, the formulated nano-sealant containing 5 wt% SrF₂, 5 wt% YSZ and 0.5 wt% ε-PL was selected as the optimal specimen and examined for ion release and cytotoxicity. The results showed an average release rate of 0.87 μg·cm^-2·day^-1 in the aqueous medium (pH 6.9) and 1.58 μg·cm^-2·day^-1 in acidic medium (pH 4.0). The maximum cytotoxicity of 20% toward human bone marrow mesenchymal stem cells (hMSCs) was observed according to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) cytotoxicity assay and acridine orange staining test. A synergy between SrF₂ nanoparticles and ε-PL exhibited a better antibacterial activity in terms of colony reduction compared to the other samples. However, the inclusion of SrF₂ and ε-PL caused mechanically weakening of the sealants that was partly compensated by incorporation of YSZ nanoparticles (up to 10 wt%).

Recent trends in the application of widely used natural and synthetic polymer nanocomposites in bone tissue regeneration

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Nanocomposite biomaterials are a relatively new class of materials that incorporate a biopolymeric and biodegradable matrix structure with bioactive and easily resorbable fillers which are nano-sized. This article is a review of a few polymeric nanocomposite biomaterials which are potential candidates for bone tissue regeneration. These nanocomposites have been broadly classified into two groups viz. natural and synthetic polymer based. Natural polymer-based nanocomposites include materials fabricated through reinforcement of nanoparticles and/or nanofibers in a natural polymer matrix. Several widely used natural biopolymers, such as chitosan (CS), collagen (Col), cellulose, silk fibroin (SF), alginate, and fucoidan, have been reviewed regarding their present investigation on the incorporation of nanomaterial, biocompatibility, and tissue regeneration. Synthetic polymer-based nanocomposites that have been covered in this review include polycaprolactone (PCL), poly (lactic-co-glycolic) acid (PLGA), polyethylene glycol (PEG), poly (lactic acid) (PLA), and polyurethane (PU) based nanocomposites. An array of nanofillers, such as nano hydroxyapatite (nHA), nano zirconia (nZr), nano silica (nSi), silver nano particles (AgNPs), nano titanium dioxide (nTiO₂), graphene oxide (GO), that is used widely across the bone tissue regeneration research platform are included in this review with respect to their incorporation into a natural and/or synthetic polymer matrix. The influence of nanofillers on cell viability, both in vitro and in vivo, along with cytocompatibility and new tissue generation has been encompassed in this review. Moreover, nanocomposite material characterization using some commonly used analytical techniques, such as electron microscopy, spectroscopy, diffraction patterns etc., has been highlighted in this review. Biomaterial physical properties, such as pore size, porosity, particle size, and mechanical strength which strongly influences cell attachment, proliferation, and subsequent tissue growth has been covered in this review. This review has been sculptured around a case by case basis of current research that is being undertaken in the field of bone regeneration engineering. The nanofillers induced into the polymeric matrix render important properties, such as large surface area, improved mechanical strength as well as stability, improved cell adhesion, proliferation, and cell differentiation. The selection of nanocomposites is thus crucial in the analysis of viable treatment strategies for bone tissue regeneration for specific bone defects such as craniofacial defects. The effects of growth factor incorporation on the nanocomposite for controlling new bone generation are also important during the biomaterial design phase.

In-vivo performance of plasma-sprayed CaO-MgO-SiO2-based bioactive glass-ceramic coating on Ti-6Al-4V alloy for bone regeneration

The CaO-MgO-SiO₂-based bioactive glass-ceramic coating (named M2) on Ti-6Al-4V alloy has been proven to behave well in vitro. But how to make full sense of its performances in terms of osteogenesis and osseointegration in vivo matters very much. For this, the M2-coated Ti-6Al-4V cylinders were prepared by atmospheric plasma spraying (APS) and implanted into New Zealand rabbit for 1, 2 and 3 months, respectively, by setting commercial HA-coated Ti-6Al-4V as the control. It is encouraging that, the two groups bonded with the surrounding tissues stably and newly formed bone grew towards or around the implants after 3-month implantation according to radiographic images. From the histological sections, it is obvious that, compared to the control, the M2-coated implant was more favorable for the osteogenesis and neo-vascularisation in the whole experimental process and demonstrated a better osseointegration with the host bone, indicating the former possessed better osteoconductivity, osteoinductivity and osteogenic ability. The study indicated that the M2-coated Ti-6Al-4V implant exerted a great potential to substitute the commercial HA-coated Ti-6Al-4V implant in repairing load-bearing bone defects.

Nanomaterials for bone tissue regeneration: updates and future perspectives

Joint replacement and bone reconstructive surgeries are on the rise globally. Current strategies for implants and bone regeneration are associated with poor integration and healing resulting in repeated surgeries. A multidisciplinary approach involving basic biological sciences, tissue engineering, regenerative medicine and clinical research is required to overcome this problem. Considering the nanostructured nature of bone, expertise and resources available through recent advancements in nanobiotechnology enable researchers to design and fabricate devices and drug delivery systems at the nanoscale to be more compatible with the bone tissue environment. The focus of this review is to present the recent progress made in the rationale and design of nanomaterials for tissue engineering and drug delivery relevant to bone regeneration.

Preparation and characterization of semi-IPNs of polycaprolactone/poly (acrylic acid)/cellulosic nanowhisker as artificial articular cartilage

Cartilage is a semi-solid resilient and smooth elastic connective tissue and upon damage, its repair is almost impossible or occurs with a very slow recovery process. Polycaprolactone (PCL), used as a biocompatible polymer, withholds all required mechanical properties, except suitable cell adhesion due to its hydrophobicity. In order to resolve this issue, we sought to introduce appropriate semi-IPNs into the system to regain its hydrophilicity base on increasing of the hydrophilic polymer. PCL and Cellulose nanowhiskers (CNWs) were entrapped in a network of poly (acrylic acid) that had been crosslinked via a novel acrylic-urethane crosslinker. The influential synthetic parameters on the preparation of artificial articular cartilages were investigated based on the Taguchi test design. The prepared CNW, acrylic-urethane crosslinker and semi-IPNs were studied via ¹H NMR, FTIR, SEM, TEM, TGA, water swelling, water contact angle, tensile, and MTT analyses. According to the results, the optimal amount of monomer was about 46%. Incorporation of an optimized amount of CNW, which was 0.5%, improved the mechanical properties of artificial cartilage. After a 30 h time period, semi-IPNs showed the water absorption of about 30%. MTT on days 1, 3 and 5, as well as cell attachment, confirmed the biocompatibility of the semi-IPNs.

Osteogenic differentiation of hMSCs on semi-interpenetrating polymer networks of polyurethane/poly(2‑hydroxyethyl methacrylate)/cellulose nanowhisker scaffolds

Poly (2‑hydroxyethyl methacrylate) (PHEMA) was crosslinked in the presence of biocompatible and biodegradable poly(caprolactone) (PCL) based polyurethanes (PUs) and cellulose nanowhiskers (CNWs). The CNWs were obtained from wastepaper. In order to crosslink PHEMA (10 wt%), a novel acrylic-urethane cross-linker was produced by a condensation reaction of PHEMA and hexamethylene diisocyanate (HDI). The PU-PHEMA-CNWs scaffolds were prepared by solvent casting/particulate leaching method in different weight percentages of CNWs (i.e., 0, 0.1, 0.5, and 1 wt%). The structural, mechanical, and in vitro biological properties of bio-nanocomposites were evaluated via FTIR, SEM, tensile, and MTT assay. The tensile strength of PU-PHEMA-0, PU-PHEMA-0.1, PU-PHEMA-0.5, and PU-PHEMA-1 were 76.2, 95.8, 98.1, and 89.8 kPa, respectively. Incorporation of CNWs also resulted in improved cell proliferation on PU-PHEMA-CNWs scaffolds. The bone marrow derived human mesenchymal stem cells (hMSCs) were seeded on the prepared porous scaffolds and incubated in osteogenic medium. Based on the results including calcium content assay, alkaline phosphatase assay, and mineralization staining, PU-PHEMA-CNW scaffolds were introduced as a suitable election for imitating the behavior of cellular niche. Bone mineralization and osteogenesis differentiation of hMSCs on PU-PHEMA-CNW scaffolds were significantly more than control after 14 days.

Human mesenchymal stem cells differentiate into an osteogenic lineage in presence of strontium containing bioactive glass nanoparticles

While bioactive glass and ions released during its dissolution are known to stimulate osteoblast cells, the effect bioactive glass has on human stem cells is not clear. Here, we show that spherical monodispersed strontium containing bioactive nanoparticles (Sr-BGNPs) of composition 90.6 mol% SiO₂, 5.0 mol% CaO, 4.4% mol% SrO (4.4%Sr-BGNPs) and 88.8 mol% SiO₂, 1.8 mol% CaO, and 9.4 mol% SrO (9.4%Sr-BGNPs) stimulate bone marrow derived human stem cell (hMSC) differentiation down an osteogenic pathway without osteogenic supplements. The particles were synthesised using a modified Stӧber process and had diameters of 90 ± 10 nm. Previous work on similar particles that did not contain Sr (80 mol% SiO₂, 20 mol% CaO) showed stem cells did not differentiate when exposed to the particles. Here, both compositions of the Sr-BGNPs (up to concentration of 250 μg/mL) stimulated the early-, mid-, and late-stage markers of osteogenic differentiation and accelerated mineralisation in the absence of osteogenic supplements. Sr ions play a key role in osteogenic stem cell differentiation. Sr-BGNP dissolution products did not adversely affect hMSC viability and no significant differences in viability were measured between each particle composition. Confocal and transmission electron microscopy (TEM) demonstrated that monodispersed Sr-BGNPs were internalised and localised within vesicles in the cytoplasm of hMSCs. Degradation of particles inside the cells was observed, whilst maintaining effective cations (Ca and Sr) in their silica network after 24 h in culture. The uptake of Sr-BGNPs by hMSCs was reduced by inhibitors of specific routes of endocytosis, indicating that the Sr-BGNPs uptake by hMSCs was probably via mixed endocytosis mechanisms. Sr-BGNPs have potential as injectable therapeutic devices for bone regeneration or treatment of conditions such as osteoporosis, because of their ability deliver a sustained release of osteogenic inorganic cations, e.g. calcium (Ca) or and strontium (Sr), through particle degradation locally to cells. STATEMENT OF SIGNIFICANCE: Here, we show that 90 nm spherical strontium containing bioactive nanoparticles of stimulate bone marrow derived human stem cell (hMSC) differentiation down an osteogenic pathway without the use of osteogenic supplements. While bioactive glass and its dissolution products are known to promote excellent bone regeneration in vivo and to stimulate osteoblast cells to produce bone matrix in vitro, their effect on human stem cells is not clear. Previously our nanoparticles that contained only SiO₂ and CaO did not provoke human bone marrow or adipose derived stem cell differentiation.

Differentiation Capacity of Monocyte-Derived Multipotential Cells on Nanocomposite Poly(e-caprolactone)-Based Thin Films

Background

Μonocyte-derived multipotential cells (MOMCs) include progenitors capable of differentiation into multiple cell lineages and thus represent an ideal autologous transplantable cell source for regenerative medicine. In this study, we cultured MOMCs, generated from mononuclear cells of peripheral blood, on the surface of nanocomposite thin films.

Methods

For this purpose, nanocomposite Poly(e-caprolactone) (PCL)-based thin films containing either 2.5 wt% silica nanotubes (SiO2ntbs) or strontium hydroxyapatite nanorods (SrHAnrds), were prepared using the spin-coating method. The induced differentiation capacity of MOMCs, towards bone and endothelium, was estimated using flow cytometry, real-time polymerase chain reaction, scanning electron microscopy and fluorescence microscopy after cells' genetic modification using the Sleeping Beauty Transposon System aiming their observation onto the scaffolds. Moreover, Wharton's Jelly Mesenchymal Stromal Cells were cultivated as a control cell line, while Human Umbilical Vein Endothelial Cells were used to strengthen and accelerate the differentiation procedure in semi-permeable culture systems. Finally, the cytotoxicity of the studied materials was checked with MTT assay.

Results

The highest differentiation capacity of MOMCs was observed on PCL/SiO2ntbs 2.5 wt% nanocomposite film, as they progressively lost their native markers and gained endothelial lineage, in both protein and transcriptional level. In addition, the presence of SrHAnrds in the PCL matrix triggered processes related to osteoblast bone formation.

Conclusion

To conclude, the differentiation of MOMCs was selectively guided by incorporating SiO2ntbs or SrHAnrds into a polymeric matrix, for the first time.

Evaluation of physicochemical, mechanical and biological properties of chitosan/carboxymethyl cellulose reinforced with multiphasic calcium phosphate whisker-like fibers for bone tissue engineering

In this study porous scaffolds of chitosan (CS) and carboxymethyl cellulose (CMC) reinforced with whisker-like biphasic and triphasic calcium phosphate fibers were fabricated by freeze drying method. The effect of addition of CMC, fiber type and content on the mechanical, physicochemical and biological properties of the composite scaffolds was evaluated. The fibers were synthesized by homogenous precipitation method and were characterized. Biphasic fibers contained two phases of hydroxyapatite (HA) and monetite, and triphasic fibers consisted of HA, β-tricalcium phosphate and calcium pyrophosphate and were 20-270 μm and 20-145 μm in length, respectively. The composite scaffolds exhibited desirable microstructures with high porosity (61-75%) and interconnected pores in range of 35-200 μm. Addition of CMC to CS led to a significant improvement in the mechanical properties (up to 150%) but did not affect the water uptake ability and biocompatibility. Both fibers improved the in vitro proliferation, attachment and mineralization of MG63 cells on scaffolds as evidenced by MTT assay, DAPI staining, SEM and Alizarin red staining. Triphasic fibers were more effective in reinforcing the scaffolds and resulted in higher cell viability. Composite scaffolds of CS and CMC reinforced with 50 wt% triphasic fibers were superior in terms of mechanical and biological properties and showed compressive strength and modulus of 150 kPa and 3.08 MPa, respectively, which is up to 300% greater than pure CS scaffolds. The findings indicate that the developed composite scaffolds are potential candidates for bone tissue engineering although they need further enhancement in mechanical properties.

Evaluation of hMSCs Response to Sodium Alginate / Bioactive Glass Composite Paste: Effect of CaO/P2O5, Sodium Alginate Concentration and P/L Ratios

Background:

Bioactive glasses with different compositions have been extensively used as bone tissue engineering. Preparation, development and characterization of alginate pastes containing bioglass for bone repair applications were the purposes of this study.

Objective:

The injectable bone pastes were produced from sol-gel derived bioactive glass nanoparticles with various CaO/P2O5 ratios of 19, 9.5 and 4.75 and sodium alginate solutions with different concentrations of 1, 2 and 4 wt.%. The effect of CaO/P2O5 and powder to liquid (P/L) ratios and alginate concentration on injectability, biodegradation, rheological properties, bioactivity and cellular behavior of the pastes have been studied. The behavior of human mesenchymal stem cells (hMSCs) in the presence of the pastes was assessed by MTT assay, biomineralization assay, ALP activity, Acridine orange staining and Alizarin red staining tests.

Results:

By adding sodium alginate, the pastes exhibited a thixotropy behavior. The storage modulus of all pastes was larger than the loss modulus in the frequency range of 0.1-100 s-1. Cytotoxicity evaluation results revealed that there was a critical amount of bioactive glass in pastes which are above the limit; the viability of hMSCs will be at risk. The pastes made of bioactive glass nanoparticles with CaO/P2O5 = 9.5 and sodium alginate 1% with P/L ratio of 0.8 showed optimum behavior in terms of mineral carrying capacity, injectability characteristics, accellular bioactivity in SBF, loss weight and wash out behavior, proliferation and differentiation of hMSCs.

Conclusion:

According to the results, the pastes prepared with sodium alginate solution and bioactive glass nanoparticles can be beneficial in bone tissue engineering.

A pH probe inhibits senescence in mesenchymal stem cells

BACKGROUND

Bone marrow-derived mesenchymal stem cells (BMSCs) are gradually getting attention because of its multi-directional differentiation potential, hematopoietic support, and promotion of stem cell implantation. However, cultured BMSCs in vitro possess a very limited proliferation potential, and the presence of stem cell aging has substantially restricted the effect together with the efficiency in clinical treatment. Recently, increasing attention has been paid to the connection between cellular aging and lysosomal acidification as new reports indicated that vacuolar H⁺-ATPase (v-ATPase) activity was altered and lysosomal pH was dysregulated in the process of cellular aging. Therefore, promoting lysosomal acidification might contribute to inhibition of cell senescence. Our previous studies showed that a novel small molecule, 3-butyl-1-chloro imidazo [1, 5-a] pyridine-7-carboxylic acid (SGJ), could selectively and sensitively respond to acidic pH with fast response (within 3 min), but whether SGJ can promote lysosomal acidification and inhibit senescence in BMSCs is unknown.

METHODS

Rat BMSCs were cultured based on our system that had been already documented. BMSCs were treated with SGJ and/or Bafilomycin-A1 (Baf-A1). The co-localization between SGJ and lysosomes was assessed by a confocal microscope. Acridine orange (AO) staining and the Lysosensor™ Green DND-189 reagents were used for indicating changes in lysosomal concentration of H⁺. Changes of senescence were detected by immunoblotting of p21 and senescence-associated beta-galactosidase (SA-β-gal) staining as well as immunofluorescence assay of senescence-associated heterochromatin foci (SAHF). Changes of autophagy were detected by immunoblotting of MAP1LC3 (LC3B) and SQSTM1 (p62). Cell proliferation was determined by flow cytometry. Cell viability was calculated by sulforhodamine B assay (SRB). The V0 proton channel of v-ATPase was knocked down by transfecting with its small interfering RNA (si-ATP6V0C).

RESULTS

Our work showed that SGJ can promote lysosomal acidification and inhibit senescence in BMSCs. Firstly, SGJ and lysosomes were well co-located in senescent BMSCs with the co-localization coefficient of 0.94. Secondly, SGJ increased the concentration of H⁺ and the protein expression of lysosome-associated membrane protein 1 (LAMP1) and lysosome-associated membrane protein 2 (LAMP2). Thirdly, SGJ suppressed the expression of p21 in the senescent BMSCs and reduced SA-β-gal positive cells. Fourthly, SGJ promoted senescent BMSCs' proliferation and protein level of LC3B but reduced the p62/SQSTM1 protein level. Furthermore, experimental group pretreated with 20 μM SGJ showed a stronger red fluorescent intensity, thinner cell morphology, less SA-β-gal positive cell, and less p21 protein level as well as higher cell viability in the presence of Baf-A1. Notably, ATP6V0C knockdown decreased the activity of v-ATPase and SGJ increased the concentration of H⁺.

CONCLUSION

Our work showed that SGJ could inhibit senescence in BMSCs and protect lysosomes by promoting expression of LAMP1 and LAMP2. Meanwhile, SGJ could promote autophagy. Furthermore, our study also suggested that SGJ was a new Baf-A1 antagonist because SGJ could target and occupy the V0 proton channel of v-ATPase.

Bone tissue engineering: Scaffold preparation using chitosan and other biomaterials with different design and fabrication techniques

In the recent years, a paradigm shift is taking place where metallic/synthetic implants and tissue grafts are being replaced by tissue engineering approach. A well designed three-dimensional scaffold is one of the fundamental tools to guide tissue formation in vitro and in vivo. Bone is a highly dynamic and an integrative tissue, and thus enormous efforts have been invested in bone tissue engineering to design a highly porous scaffold which plays a critical role in guiding bone growth and regeneration. Numerous techniques have been developed to fabricate highly interconnected, porous scaffold for bone tissue engineering applications with the help of biomolecules such as chitosan, collagen, gelatin, silk, etc. We aim, in this review, to provide an overview of different types of fabrication techniques for scaffold preparation in bone tissue engineering using biological macromolecules.