Evaluation of the potential of chitosan/ β -1,3-glucan/hydroxyapatite material as a scaffold for living bone graft production in vitro by comparison of ADSC and BMDSC behaviour on its surface

Titanium-Doped Diamond-like Carbon Layers as a Promising Coating for Joint Replacements Supporting Osteogenic Differentiation of Mesenchymal Stem Cells

Diamond-like carbon (DLC) layers are known for their high corrosion and wear resistance, low friction, and high biocompatibility. However, it is often necessary to dope DLC layers with additional chemical elements to strengthen their adhesion to the substrate. Ti-DLC layers (doped with 0.4, 2.1, 3.7, 6.6, and 12.8 at.% of Ti) were prepared by dual pulsed laser deposition, and pure DLC, glass, and polystyrene (PS) were used as controls. In vitro cell-material interactions were investigated with an emphasis on cell adhesion, proliferation, and osteogenic differentiation. We observed slightly increasing roughness and contact angle and decreasing surface free energy on Ti-DLC layers with increasing Ti content. Three-week biological experiments were performed using adipose tissue-derived stem cells (ADSCs) and bone marrow mesenchymal stem cells (bmMSCs) in vitro. The cell proliferation activity was similar or slightly higher on the Ti-doped materials than on glass and PS. Osteogenic cell differentiation on all materials was proved by collagen and osteocalcin production, ALP activity, and Ca deposition. The bmMSCs exhibited greater initial proliferation potential and an earlier onset of osteogenic differentiation than the ADSCs. The ADSCs showed a slightly higher formation of focal adhesions, higher metabolic activity, and Ca deposition with increasing Ti content.

Biomaterials combined with ADSCs for bone tissue engineering: current advances and applications

In recent decades, bone tissue engineering, which is supported by scaffold, seed cells and bioactive molecules (BMs), has provided new hope and direction for treating bone defects. In terms of seed cells, compared to bone marrow mesenchymal stem cells, which were widely utilized in previous years, adipose-derived stem cells (ADSCs) are becoming increasingly favored by researchers due to their abundant sources, easy availability and multi-differentiation potentials. However, there is no systematic theoretical basis for selecting appropriate biomaterials loaded with ADSCs. In this review, the regulatory effects of various biomaterials on the behavior of ADSCs are summarized from four perspectives, including biocompatibility, inflammation regulation, angiogenesis and osteogenesis, to illustrate the potential of combining various materials with ADSCs for the treatment of bone defects. In addition, we conclude the influence of additional application of various BMs on the bone repair effect of ADSCs, in order to provide more evidences and support for the selection or preparation of suitable biomaterials and BMs to work with ADSCs. More importantly, the associated clinical case reports and experiments are generalized to provide additional ideas for the clinical transformation and application of bone tissue engineering loaded with ADSCs.

Biomimetic biphasic curdlan-based scaffold for osteochondral tissue engineering applications - Characterization and preliminary evaluation of mesenchymal stem cell response in vitro

Osteochondral defects remain a huge problem in medicine today. Biomimetic bi- or multi-phasic scaffolds constitute a very promising alternative to osteochondral autografts and allografts. In this study, a new curdlan-based scaffold was designed for osteochondral tissue engineering applications. To achieve biomimetic properties, it was enriched with a protein component - whey protein isolate as well as a ceramic ingredient - hydroxyapatite granules. The scaffold was fabricated via a simple and cost-efficient method, which represents a significant advantage. Importantly, this technique allowed generation of a scaffold with two distinct, but integrated phases. Scanning electron microcopy and optical profilometry observations demonstrated that phases of biomaterial possessed different structural properties. The top layer of the biomaterial (mimicking the cartilage) was smoother than the bottom one (mimicking the subchondral bone), which is beneficial from a biological point of view because unlike bone, cartilage is a smooth tissue. Moreover, mechanical testing showed that the top layer of the biomaterial had mechanical properties close to those of natural cartilage. Although the mechanical properties of the bottom layer of scaffold were lower than those of the subchondral bone, it was still higher than in many analogous systems. Most importantly, cell culture experiments indicated that the biomaterial possessed high cytocompatibility towards adipose tissue-derived mesenchymal stem cells and bone marrow-derived mesenchymal stem cells in vitro. Both phases of the scaffold enhanced cell adhesion, proliferation, and chondrogenic differentiation of stem cells (revealing its chondroinductive properties in vitro) as well as osteogenic differentiation of these cells (revealing its osteoinductive properties in vitro). Given all features of the novel curdlan-based scaffold, it is worth noting that it may be considered as promising candidate for osteochondral tissue engineering applications.

Influence of Human Jaw Periosteal Cells Seeded β-Tricalcium Phosphate Scaffolds on Blood Coagulation

Tissue engineering offers auspicious opportunities in oral and maxillofacial surgery to heal bone defects. For this purpose, the combination of cells with stability-providing scaffolds is required. Jaw periosteal cells (JPCs) are well suited for regenerative therapies, as they are easily accessible and show strong osteogenic potential. In this study, we analyzed the influence of uncoated and polylactic-co-glycolic acid (PLGA)-coated β-tricalcium phosphate (β-TCP) scaffolds on JPC colonization and subsequent osteogenic differentiation. Furthermore, interaction with the human blood was investigated. This study demonstrated that PLGA-coated and uncoated β-TCP scaffolds can be colonized with JPCs and further differentiated into osteogenic cells. On day 15, after cell seeding, JPCs with and without osteogenic differentiation were incubated with fresh human whole blood under dynamic conditions. The activation of coagulation, complement system, inflammation, and blood cells were analyzed using ELISA and scanning electron microscopy (SEM). JPC-seeded scaffolds showed a dense cell layer and osteogenic differentiation capacity on both PLGA-coated and uncoated β-TCP scaffolds. SEM analyses showed no relevant blood cell attachment and ELISA results revealed no significant increase in most of the analyzed cell activation markers (β-thromboglobulin, Sc5B-9, polymorphonuclear (PMN)-elastase). However, a notable increase in thrombin-antithrombin III (TAT) complex levels, as well as fibrin fiber accumulation on JPC-seeded β-TCP scaffolds, was detected compared to the scaffolds without JPCs. Thus, this study demonstrated that besides the scaffold material the cells colonizing the scaffolds can also influence hemostasis, which can influence the regeneration of bone tissue.

Combination of optimized tissue engineering bone implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits

In this study, effects of combining optimized tissue engineering bone (TEB) implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits were investigated. Physiological characteristics of bone marrow mesenchymal stem cells (BMMSCs), compact bone cells (CBCs), and bone marrow and compact bone coculture cells (BMMSC-CBCs) were compared to select the optimal seed cells for optimized TEB construction. Rabbits with segmental bone defects were treated in different ways (cancellous bone scaffold for group A, cancellous bone scaffold and mechanical loading for group B, optimized TEB for group C, optimized TEB and mechanical loading for group D, n = 4), and the bone repair were compared. BMMSC-CBCs showed better proliferation capacity than CBCs (p < 0.01) and stronger osteogenic differentiation ability than BMMSCs (p < 0.05). Heel-strike like mechanical loading improved proliferation and osteogenic differentiation ability and expression levels of TGFβ1 as well as BMP2 of seed cells in vitro (p < 0.05). At week 12 post-operation, group D showed the best bone repair, followed by groups B and C, while group A finished last (p < 0.05). During week 4 to 12 post-operation, group D peaked in terms of expression levels of TGFβ1, BMP2, and OCN, followed by groups B and C, while group A finished last (p < 0.05). Thus, BMMSC-CBCs showed good proliferation and osteogenic differentiation ability, and they were thought to be better as seed cells than BMMSCs and CBCs. The optimized TEB implantation combined with heel-strike like mechanical loading had a synergistic effect on bone defect healing, and enhanced expression of TGFβ1 and BMP2 played an important role in this process.

Physicochemical changes of the chitosan/β-1,3-glucan/hydroxyapatite biocomposite caused by mesenchymal stem cells cultured on its surface in vitro

In the present study structural characteristics and physicochemical properties of tri-component biomaterial (consisting of chitosan, β-1,3-glucan and hydroxyapatite) seeded with mesenchymal stem cells were investigated with the use of diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). In this study we use non-conventional approach of DRIFT spectroscopy for investigating biomaterial changes under simulated physiological conditions. Particular cell-induced changes were intended to be properly evaluated with analytical methods. Abovementioned techniques allowed to precisely assess the changes on the surface of the biomaterial caused by two kinds of stem cells (ADSCs - Adipose tissue-Derived Stem Cells and BMDSCs - Bone Marrow-Derived Stem Cells) cultured directly on the surface of bioceramic-based biomaterial. The bioactivity and biocompatibility of designed bone biomaterial were demonstrated and hence it seems to be a promising scaffold used in tissue engineering. Designed chitosan, β-1,3-glucan, and hydroxyapatite biomaterial was proven to be non-toxic, surgically handy with cellular compatibility. The obtained results are interesting and promising in terms of spectroscopic methods suitability for qualitative assessment of material-cell interactions.

Accelerated in vitro recellularization of decellularized porcine pericardium for cardiovascular grafts

An ideal decellularized allogenic or xenogeneic cardiovascular graft should be capable of preventing thrombus formation after implantation. The antithrombogenicity of the graft is ensured by a confluent endothelial cell layer formed on its surface. Later repopulation and remodeling of the scaffold by the patient's cells should result in the formation of living autologous tissue. In the work presented here, decellularized porcine pericardium scaffolds were modified by growing a fibrin mesh on the surface and inside the scaffolds, and by attaching heparin and human vascular endothelial growth factor (VEGF) to this mesh. Then the scaffolds were seeded with human adipose tissue-derived stem cells (ASCs). While the ASCs grew only on the surface of the decellularized pericardium, the fibrin-modified scaffolds were entirely repopulated in 28 d, and the scaffolds modified with fibrin, heparin and VEGF were already repopulated within 6 d. Label free mass spectrometry revealed fibronectin, collagens, and other extracellular matrix proteins produced by ASCs during recellularization. Thin layers of human umbilical endothelial cells were formed within 4 d after the cells were seeded on the surfaces of the scaffold, which had previously been seeded with ASCs. The results indicate that an artificial tissue prepared by in vitro recellularization and remodeling of decellularized non-autologous pericardium with autologous ASCs seems to be a promising candidate for cardiovascular grafts capable of accelerating in situ endothelialization. ASCs resemble the valve interstitial cells present in heart valves. An advantage of this approach is that ASCs can easily be collected from the patient by liposuction.

Differentiation of adipose tissue-derived stem cells towards vascular smooth muscle cells on modified poly(L-lactide) foils

The aim of our research was to study the behaviour of adipose tissue-derived stem cells (ADSCs) and vascular smooth muscle cells (VSMCs) on variously modified poly(L-lactide) (PLLA) foils, namely on pristine PLLA, plasma-treated PLLA, PLLA grafted with polyethylene glycol (PEG), PLLA grafted with dextran (Dex), and the tissue culture polystyrene (PS) control. On these materials, the ADSCs were biochemically differentiated towards VSMCs by a medium supplemented with TGFβ1, BMP4 and ascorbic acid (i.e. differentiation medium). ADSCs cultured in a non-differentiation medium were used as a negative control. Mature VSMCs cultured in both types of medium were used as a positive control. The impact of the variously modified PLLA foils and/or differences in the composition of the medium were studied with reference to cell adhesion, growth and differentiation. We observed similar adhesion and growth of ADSCs on all PLLA samples when they were cultured in the non-differentiation medium. The differentiation medium supported the expression of specific early, mid-term and/or late markers of differentiation (i.e. type I collagen, αSMA, calponin, smoothelin, and smooth muscle myosin heavy chain) in ADSCs on all tested samples. Moreover, ADSCs cultured in the differentiation medium revealed significant differences in cell growth among the samples that were similar to the differences observed in the cultures of VSMCs. The round morphology of the VSMCs indicated worse adhesion to pristine PLLA, and this sample was also characterized by the lowest cell proliferation. Culturing VSMCs in the differentiation medium inhibited their metabolic activity and reduced the cell numbers. Both cell types formed the most stable monolayer on plasma-treated PLLA and on the PS control. The behaviour of ADSCs and VSMCs on the tested PLLA foils differed according to the specific cell type and culture conditions. The suitable biocompatibility of both cell types on the tested PLLA foils seems to be favourable for vascular tissue engineering purposes.

Growth Factors VEGF-A165 and FGF-2 as Multifunctional Biomolecules Governing Cell Adhesion and Proliferation

Vascular endothelial growth factor-A165 (VEGF-A165) and fibroblast growth factor-2 (FGF-2) are currently used for the functionalization of biomaterials designed for tissue engineering. We have developed a new simple method for heterologous expression and purification of VEGF-A165 and FGF-2 in the yeast expression system of Pichia pastoris. The biological activity of the growth factors was assessed in cultures of human and porcine adipose tissue-derived stem cells (ADSCs) and human umbilical vein endothelial cells (HUVECs). When added into the culture medium, VEGF-A165 stimulated proliferation only in HUVECs, while FGF-2 stimulated the proliferation of both cell types. A similar effect was achieved when the growth factors were pre-adsorbed to polystyrene wells. The effect of our recombinant growth factors was slightly lower than that of commercially available factors, which was attributed to the presence of some impurities. The stimulatory effect of the VEGF-A165 on cell adhesion was rather weak, especially in ADSCs. FGF-2 was a potent stimulator of the adhesion of ADSCs but had no to negative effect on the adhesion of HUVECs. In sum, FGF-2 and VEGF-A165 have diverse effects on the behavior of different cell types, which maybe utilized in tissue engineering.

Application of Raman Spectroscopic Imaging to Assess the Structural Changes at Cell-Scaffold Interface

Raman spectroscopic imaging and mapping were applied to characterise three-compound ceramic composite biomaterial consisting of chitosan, β-1,3-d-glucan (curdlan) and hydroxyapatite (HA) developed as a bone tissue engineering product (TEP). In this rapidly advancing domain of medical science, the urge for quick, reliable and specific method for products evaluation and tissue–implant interaction, in this case bone formation process, is constantly present. Two types of stem cells, adipose-derived stem cells (ADSCs) and bone marrow-derived stem cells (BMDSCs), were cultured on composite surface. Raman spectroscopic imaging provided advantageous information on molecular differences and spatial distribution of compounds within and between the cell-seeded and untreated samples at a microscopic level. With the use of this, it was possible to confirm composite biocompatibility and bioactivity in vitro. Deposition of HA and changes in its crystallinity along with protein adsorption proved new bone tissue formation in both mesenchymal stem cell samples, where the cells proliferated, differentiated and produced biomineralised extracellular matrix (ECM). The usefulness of spectroscopic Raman imaging was confirmed in tissue engineering in terms of both the organic and inorganic components considering composite–cells interaction.

Collagen maturity and mineralization in mesenchymal stem cells cultured on the hydroxyapatite-based bone scaffold analyzed by ATR-FTIR spectroscopic imaging

Modern bone tissue engineering is based on the use of implants in the form of biomaterials, which are used as scaffolds for osteoprogenitor or stem cells. The task of the scaffolds is to temporarily sustain the function, proliferation and differentiation of bone tissue to enable its regeneration. The aim of this work is to use the macro ATR-FTIR spectroscopic imaging for analysis of the ceramic-based biomaterial (chitosan/β-1,3-glucan/hydroxyapatite). Specifically, during long-term culture of mesenchymal cells derived from adipose tissue (ADSCs) and bone marrow (BMDSCs) on the surface of scaffold. Infrared spectroscopy allows the acquisition of information on both the organic and inorganic parts of the tested composite. This innovative spectroscopic approach proved to be very suitable for studying the formation of new bone tissue and ECM components, sample staining and demineralization are not required and consequently the approach is rapid and cost-effective. The novelty of this study focuses on the innovatory use of ATR-FTIR imaging to evaluate the molecular structure and maturity of collagen as well as mineral matrix formation and crystallization in the context of bone regenerative medicine. Our research has shown that the biomaterial investigated on this work facilitates the formation of valid bone ECM of the stem cells types studied, as a result of the synthesis of type I collagen and mineral content deposition. Nevertheless, ADSC cells have been proven to produce a greater amount of collagen with a lower content of helical secondary structures, at the same time showing a higher mineralization intensity compared to BMDSC cells. Considering the above results, it could be stated that the developed scaffold is a promising material for biomedical applications, including modification of bone implants to increase their biocompatibility.

Ex vivo determination of chitosan/curdlan/hydroxyapatite biomaterial osseointegration with the use of human trabecular bone explant: New method for biocompatibility testing of bone implants reducing animal tests

Permanent orthopedic/dental implants should reveal good osseointegration, which is defined as an ability of the biomaterial to form a direct connection with the surrounding host bone tissue after its implantation into the living organism. Currently, biomaterial osseointegration is confirmed exclusively with the use of in vivo animal tests. This study presents for the first time ex vivo determination of osseointegration process using human trabecular bone explant that was drilled and filled with the chitosan/curdlan/hydroxyapatite biomaterial, followed by its long-term culture under in vitro conditions. Within this study, it was clearly proved that tested biomaterial allows for the formation of the connection with bone explant since osteoblasts, having ability to produce bone extracellular matrix (type I collagen, fibronectin), were detected at a bone-implant interface by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Importantly, in this research it was demonstrated by Live/Dead staining and CLSM imaging that human bone explants may stay alive for a long period of time (at least approx. 50 days) during their culture under in vitro conditions. Therefore, ex vivo bone explant, which is a heterogeneous tissue containing many different cell types, may serve as an excellent model to test biomaterial osseointegration during comparative and preliminary studies, reducing animal tests which is compatible with the principles of '3Rs', aiming to Replace, Reduce and Refine the use of animals wherever possible.

Biomimetic cues from poly(lactic-co-glycolic acid)/hydroxyapatite nano-fibrous scaffolds drive osteogenic commitment in human mesenchymal stem cells in the absence of osteogenic factor supplements

Mimicking the complex hierarchical architecture of the 'osteon', the functional unit of cortical bone, from the bottom-up offers the possibility of generating mature bone tissue in tissue engineered bone substitutes. In this work, a modular 'bottom-up' approach has been developed to assemble bone niche-mimicking nanocomposite scaffolds composed of aligned electrospun nanofibers of poly(lactic-co-glycolic acid) (PLGA) encapsulating aligned rod-shape nano-sized hydroxyapatite (nHA). By encoding axial orientation of the nHA within these aligned nanocomposite fibers, significant improvements in mechanical properties, surface roughness, hydrophilicity and in vitro simulated body fluid (SBF) mineral deposition were achieved. Moreover, these hierarchical scaffolds induced robust formation of bone hydroxyapatite and osteoblastic maturation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in growth media that was absent of any soluble osteogenic differentiation factors. The results of this investigation confirm that these tailored, aligned nanocomposite fibers, in the absence of media-bone inductive factors, offer the requisite biophysical and biochemical cues to hBMSCs to promote and support their differentiation into mature osteoblast cells and form early bone-like tissue in vitro.

The Effect of Various Surface Treatments of Ti6Al4V on the Growth and Osteogenic Differentiation of Adipose Tissue-Derived Stem Cells

The physical and chemical properties of the material surface, especially its roughness and wettability, have a crucial effect on the adhesion, proliferation, and differentiation of cells. The aim of this study is to select the most appropriate surface modifications of Ti6Al4V implants for pre-colonization of the implants with adipose tissue-derived stem cells (ASCs) in order to improve their osseointegration. We compared the adhesion, growth, and osteogenic differentiation of rat ASCs on Ti6Al4V samples modified by methods commonly used for preparing clinically used titanium-based implants, namely polishing (PL), coating with diamond-like carbon (DLC), brushing (BR), anodizing (AND), and blasting (BL). The material surface roughness, measured by the Ra and Rq parameters, increased in the following order: PL < DLC ˂ BR ˂ AND ˂ BL. The water drop contact angle was in the range of 60–74°, with the exception of the DLC-coated samples, where it was only 38°. The cell number, morphology, mitochondrial activity, relative fluorescence intensity of osteogenic markers RUNX2, type 1 collagen, and osteopontin, the calcium consumption by the cells and the alkaline phosphatase activity depended on the surface roughness rather than on the surface wettability of the materials. Materials with a surface roughness of several tens of nanometers (Ra 60–70 nm), i.e., the BR and AND samples, supported a satisfactory level of cell proliferation. At the same time, they achieved the highest level of osteogenic cell differentiation. These surface modifications therefore seem to be most suitable for pre-colonization of Ti6Al4V implants with stem cells pre-differentiated toward osteoblasts, and then for implanting them into the bone tissue.

Cellular Response to Vitamin C-Enriched Chitosan/Agarose Film with Potential Application as Artificial Skin Substitute for Chronic Wound Treatment

The treatment of chronic wounds is still a meaningful challenge to physicians. The aim of this work was to produce vitamin C-enriched chitosan/agarose (CHN/A) film that could serve as potential artificial skin substitute for chronic wound treatment. The biomaterial was fabricated by a newly developed and simplified method via mixing acidic chitosan solution with alkaline agarose solution that allowed to obtain slightly acidic pH (5.97) of the resultant material, which is known to support skin regeneration. Vitamin C was immobilized within the matrix of the film by entrapment method during production process. Produced films (CHN/A and CHN/A + vit C) were subjected to comprehensive evaluation of cellular response with the use of human skin fibroblasts, epidermal keratinocytes, and macrophages. It was demonstrated that novel biomaterials support adhesion and growth of human skin fibroblasts and keratinocytes, have ability to slightly reduce transforming growth factor-beta 1 (TGF-β1) (known to be present at augmented levels in the epidermis of chronic wounds), and increase platelet-derived growth factor-BB (PDGF-BB) secretion by the cells. Nevertheless, addition of vitamin C to the biomaterial formulation does not significantly improve its biological properties due to burst vitamin release profile. Obtained results clearly demonstrated that produced CHN/A film has great potential to be used as cellular dermal, epidermal, or dermo-epidermal graft pre-seeded with human skin cells for chronic wound treatment.

The Influence of Negative Pressure and of the Harvesting Site on the Characteristics of Human Adipose Tissue-Derived Stromal Cells from Lipoaspirates

Background

Adipose tissue-derived stromal cells (ADSCs) have great potential for cell-based therapies, including tissue engineering. However, various factors can influence the characteristics of isolated ADSCs.

Methods

We studied the influence of the harvesting site, i.e., inner thigh (n = 3), outer thigh (n = 3), outer thigh (n = 3), outer thigh (

Results

We revealed higher initial cell yields from the outer thigh region than from the abdomen region. Negative pressure did not influence the cell yields from the outer thigh region, whereas the yields from the abdomen region were higher under high negative pressure than under low negative pressure. In the subsequent passage, in general, no significant relationship was identified between the different negative pressure and ADSC characteristics. No significant difference was observed in the characteristics of thigh ADSCs and abdomen ADSCs. Only on day 1, the diameter was significantly bigger in outer thigh ADSCs than in abdomen ADSCs. Moreover, we noted a tendency of thigh ADSCs (i.e., inner thigh+outer thigh) to reach a higher cell number on day 7. Discussion. The harvesting site and negative pressure can potentially influence initial cell yields from lipoaspirates. However, for subsequent in vitro culturing and for use in tissue engineering, it seems that the harvesting site and the level of negative pressure do not have a crucial or limiting effect on basic ADSC characteristics.in vitro culturing and for use in tissue engineering, it seems that the harvesting site and the level of negative pressure do not have a crucial or limiting effect on basic ADSC characteristics.

Applications of Nanocellulose/Nanocarbon Composites: Focus on Biotechnology and Medicine

Nanocellulose/nanocarbon composites are newly emerging smart hybrid materials containing cellulose nanoparticles, such as nanofibrils and nanocrystals, and carbon nanoparticles, such as "classical" carbon allotropes (fullerenes, graphene, nanotubes and nanodiamonds), or other carbon nanostructures (carbon nanofibers, carbon quantum dots, activated carbon and carbon black). The nanocellulose component acts as a dispersing agent and homogeneously distributes the carbon nanoparticles in an aqueous environment. Nanocellulose/nanocarbon composites can be prepared with many advantageous properties, such as high mechanical strength, flexibility, stretchability, tunable thermal and electrical conductivity, tunable optical transparency, photodynamic and photothermal activity, nanoporous character and high adsorption capacity. They are therefore promising for a wide range of industrial applications, such as energy generation, storage and conversion, water purification, food packaging, construction of fire retardants and shape memory devices. They also hold great promise for biomedical applications, such as radical scavenging, photodynamic and photothermal therapy of tumors and microbial infections, drug delivery, biosensorics, isolation of various biomolecules, electrical stimulation of damaged tissues (e.g., cardiac, neural), neural and bone tissue engineering, engineering of blood vessels and advanced wound dressing, e.g., with antimicrobial and antitumor activity. However, the potential cytotoxicity and immunogenicity of the composites and their components must also be taken into account.

Polysaccharide-Based Systems for Targeted Stem Cell Differentiation and Bone Regeneration

Bone tissue engineering is an ever-changing, rapidly evolving, and highly interdisciplinary field of study, where scientists try to mimic natural bone structure as closely as possible in order to facilitate bone healing. New insights from cell biology, specifically from mesenchymal stem cell differentiation and signaling, lead to new approaches in bone regeneration. Novel scaffold and drug release materials based on polysaccharides gain increasing attention due to their wide availability and good biocompatibility to be used as hydrogels and/or hybrid components for drug release and tissue engineering. This article reviews the current state of the art, recent developments, and future perspectives in polysaccharide-based systems used for bone regeneration.

Development and Optimization of the Novel Fabrication Method of Highly Macroporous Chitosan/Agarose/Nanohydroxyapatite Bone Scaffold for Potential Regenerative Medicine Applications

Bone scaffolds mimicking the three-dimensional bone structure are of essential importance for bone regeneration. The aim of this study was to develop and optimize the production method of highly macroporous bone scaffold composed of polysaccharide matrix (chitosan-agarose) reinforced with nanohydroxyapatite. The highly macroporous structure was obtained by the simultaneous application of a gas-foaming agent and freeze-drying technique. Fabricated variants of biomaterials (produced using different gas-foaming agent and solvent concentrations) were subjected to porosity evaluation and compression test in order to select the scaffold with the best properties. Then, bioactivity, cytotoxicity, and cell growth on the surface of the selected biomaterial were assessed. The obtained results showed that the simultaneous application of gas-foaming and freeze-drying methods allows for the production of biomaterials characterized by high total and open porosity. It was proved that the best porosity is obtained when solvent (CH3COOH) and foaming agent (NaHCO3) are applied at ratio 1:1. Nevertheless, the high porosity of novel biomaterial decreases its mechanical strength as determined by compression test. Importantly, novel scaffold is non-toxic to osteoblasts and favors cell attachment and growth on its surface. All mentioned properties make the novel biomaterial a promising candidate to be used in regenerative medicine in non-load bearing implantation sites.

Novel chitosan/agarose/hydroxyapatite nanocomposite scaffold for bone tissue engineering applications: comprehensive evaluation of biocompatibility and osteoinductivity with the use of osteoblasts and mesenchymal stem cells

Background

Nanocomposites produced by reinforcement of polysaccharide matrix with nanoparticles are widely used in engineering of biomaterials. However, clinical applications of developed novel biomaterials are often limited due to their poor biocompatibility.

Purpose

The aim of this work was to comprehensively assess biocompatibility of highly macroporous chitosan/agarose/nanohydroxyapatite bone scaffolds produced by a novel method combining freeze-drying with a foaming agent. Within these studies, blood plasma protein adsorption, osteoblast (MC3T3-E1 Subclone 4 and hFOB 1.19) adhesion and proliferation, and osteogenic differentiation of mesenchymal stem cells derived from bone marrow and adipose tissue were determined. The obtained results were also correlated with materials' surface chemistry and wettability to explain the observed protein and cellular response.

Results

Obtained results clearly showed that the developed nanocomposite scaffolds were characterized by high biocompatibility and osteoconductivity. Importantly, the scaffolds also revealed osteoinductive properties since they have the ability to induce osteogenic differentiation (Runx2 synthesis) in undifferentiated mesenchymal stem cells. The surface of biomaterials is extremely hydrophilic, prone to protein adsorption with the highest affinity toward fibronectin binding, which allows for good osteoblast adhesion, spreading, and proliferation.

Conclusion

Produced by a novel method, macroporous nanocomposite biomaterials have great potential to be used in regenerative medicine for acceleration of the bone healing process.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Current Trends in Fabrication of Biomaterials for Bone and Cartilage Regeneration: Materials Modifications and Biophysical Stimulations

The aim of engineering of biomaterials is to fabricate implantable biocompatible scaffold that would accelerate regeneration of the tissue and ideally protect the wound against biodevice-related infections, which may cause prolonged inflammation and biomaterial failure. To obtain antimicrobial and highly biocompatible scaffolds promoting cell adhesion and growth, materials scientists are still searching for novel modifications of biomaterials. This review presents current trends in the field of engineering of biomaterials concerning application of various modifications and biophysical stimulation of scaffolds to obtain implants allowing for fast regeneration process of bone and cartilage as well as providing long-lasting antimicrobial protection at the site of injury. The article describes metal ion and plasma modifications of biomaterials as well as post-surgery external stimulations of implants with ultrasound and magnetic field, providing accelerated regeneration process. Finally, the review summarizes recent findings concerning the use of piezoelectric biomaterials in regenerative medicine.

The summary of the most important cell-biomaterial interactions that need to be considered during in vitro biocompatibility testing of bone scaffolds for tissue engineering applications

Tissue engineered products (TEPs), which mean biomaterials containing either cells or growth factors or both cells and growth factors, may be used as an alternative to the autografts taken directly from the bone of the patients. Nevertheless, the use of TEPs needs much more understanding of biointeractions between biomaterials and eukaryotic cells. Despite the possibility of the use of in vitro cellular models for initial evaluation of the host response to the implanted biomaterial, it is observed that most researchers use cell cultures only for the evaluation of cytotoxicity and cell proliferation on the biomaterial surface, and then they proceed to animal models and in vivo testing of bone implants without fully utilizing the scientific potential of in vitro models. In this review, the most important biointeractions between eukaryotic cells and biomaterials were discussed, indicating molecular mechanisms of cell adhesion, proliferation, and biomaterial-induced activation of immune cells. The article also describes types of cellular models which are commonly used for biomaterial testing and highlights the possibilities and drawbacks of in vitro tests for biocompatibility evaluation of novel scaffolds. Finally, the review summarizes recent findings concerning the use of adult mesenchymal stem cells for TEP generation and compares the potential of bone marrow- and adipose tissue-derived stem cells in regenerative medicine applications.

Application of adult mesenchymal stem cells in bone and vascular tissue engineering

Tissue engineering is a very promising field of regenerative medicine. Life expectancy has been increasing, and tissue replacement is increasingly needed in patients suffering from various degenerative disorders of the organs. The use of adult mesenchymal stem cells (e.g. from adipose tissue or from bone marrow) in tissue engineering seems to be a promising approach for tissue replacements. Clinical applications can make direct use of the large secretome of these cells, which can have a positive influence on other cells around. Another advantage of adult mesenchymal stem cells is the possibility to differentiate them into various mature cells via appropriate culture conditions (i.e. medium composition, biomaterial properties, and dynamic conditions). This review is focused on current and future ways to carry out tissue replacement of damaged bones and blood vessels, especially with the use of suitable adult mesenchymal stem cells as a potential source of differentiated mature cells that can later be used for tissue replacement. The advantages and disadvantages of different stem cell sources are discussed, with a main focus on adipose-derived stem cells. Patient factors that can influence later clinical applications are taken into account.

Journey into Bone Models: A Review

Bone is a complex tissue with a variety of functions, such as providing mechanical stability for locomotion, protection of the inner organs, mineral homeostasis and haematopoiesis. To fulfil these diverse roles in the human body, bone consists of a multitude of different cells and an extracellular matrix that is mechanically stable, yet flexible at the same time. Unlike most tissues, bone is under constant renewal facilitated by a coordinated interaction of bone-forming and bone-resorbing cells. It is thus challenging to recreate bone in its complexity in vitro and most current models rather focus on certain aspects of bone biology that are of relevance for the research question addressed. In addition, animal models are still regarded as the gold-standard in the context of bone biology and pathology, especially for the development of novel treatment strategies. However, species-specific differences impede the translation of findings from animal models to humans. The current review summarizes and discusses the latest developments in bone tissue engineering and organoid culture including suitable cell sources, extracellular matrices and microfluidic bioreactor systems. With available technology in mind, a best possible bone model will be hypothesized. Furthermore, the future need and application of such a complex model will be discussed.

Stem cells: their source, potency and use in regenerative therapies with focus on adipose-derived stem cells - a review

Stem cells can be defined as units of biological organization that are responsible for the development and the regeneration of organ and tissue systems. They are able to renew their populations and to differentiate into multiple cell lineages. Therefore, these cells have great potential in advanced tissue engineering and cell therapies. When seeded on synthetic or nature-derived scaffolds in vitro, stem cells can be differentiated towards the desired phenotype by an appropriate composition, by an appropriate architecture, and by appropriate physicochemical and mechanical properties of the scaffolds, particularly if the scaffold properties are combined with a suitable composition of cell culture media, and with suitable mechanical, electrical or magnetic stimulation. For cell therapy, stem cells can be injected directly into damaged tissues and organs in vivo. Since the regenerative effect of stem cells is based mainly on the autocrine production of growth factors, immunomodulators and other bioactive molecules stored in extracellular vesicles, these structures can be isolated and used instead of cells for a novel therapeutic approach called "stem cell-based cell-free therapy". There are four main sources of stem cells, i.e. embryonic tissues, fetal tissues, adult tissues and differentiated somatic cells after they have been genetically reprogrammed, which are referred to as induced pluripotent stem cells (iPSCs). Although adult stem cells have lower potency than the other three stem cell types, i.e. they are capable of differentiating into only a limited quantity of specific cell types, these cells are able to overcome the ethical and legal issues accompanying the application of embryonic and fetal stem cells and the mutational effects associated with iPSCs. Moreover, adult stem cells can be used in autogenous form. These cells are present in practically all tissues in the organism. However, adipose tissue seems to be the most advantageous tissue from which to isolate them, because of its abundancy, its subcutaneous location, and the need for less invasive techniques. Adipose tissue-derived stem cells (ASCs) are therefore considered highly promising in present-day regenerative medicine.

Human adipose-derived mesenchymal stem cells seeded into a collagen-hydroxyapatite scaffold promote bone augmentation after implantation in the mouse

Traumatic injury or surgical excision of diseased bone tissue usually require the reconstruction of large bone defects unable to heal spontaneously, especially in older individuals. This is a big challenge requiring the development of biomaterials mimicking the bone structure and capable of inducing the right commitment of cells seeded within the scaffold. In particular, given their properties and large availability, the human adipose-derived stem cells are considered as the better candidate for autologous cell transplantation. In order to evaluate the regenerative potential of these cells along with an osteoinductive biomaterial, we have used collagen/hydroxyapatite scaffolds to test ectopic bone formation after subcutaneous implantation in mice. The process was analysed both in vivo, by Fluorescent Molecular Tomography (FMT), and ex vivo, to evaluate the formation of bone and vascular structures. The results have shown that the biomaterial could itself be able of promoting differentiation of host cells and bone formation, probably by means of its intrinsic chemical and structural properties, namely the microenvironment. However, when charged with human mesenchymal stem cells, the ectopic bone formation within the scaffold was increased. We believe that these results represent an important advancement in the field of bone physiology, as well as in regenerative medicine.

Bone marrow-derived stem/stromal cells and adipose tissue-derived stem/stromal cells: Their comparative efficacies and synergistic effects

Mesenchymal stem cells (MSCs) are heterogeneous cell populations that serve as reserves for tissue regeneration in the presence of disease or injury. Although MSCs are found in various tissues, bone marrow-derived stem/stromal cells (BMSCs) and adipose tissue-derived stem/stromal cells (ADSCs) have been most thoroughly investigated. Furthermore, ADSCs have recently emerged as an attractive source of MSCs due to their abundance and availability. BMSCs and ADSCs demonstrate similar morphological characteristics, but their in vitro characteristics and differentiation abilities appear to differ. In this review, the author summarizes and compares current knowledge on BMSCs and ADSCs with particular emphasis on in vitro expansion and osteogenic/angiogenic potential, and reviews knowledge of their synergistic effects when co-applied. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2640-2648, 2017.