Dynamic competitive adsorption of bone-related proteins on calcium phosphate ceramic particles with different phase composition and microstructure

The genetic background determines material-induced bone formation through the macrophage-osteoclast axis

Osteoinductive materials are characterized by their ability to induce bone formation in ectopic sites. Thus, osteoinductive materials hold promising potential for repairing bone defects. However, the mechanism of material-induced bone formation remains unknown, which limits the design of highly potent osteoinductive materials. Here, we demonstrated a genetic background link among macrophage polarization, osteoclastogenesis and material-induced bone formation. The intramuscular implantation of an osteoinductive material in FVB/NCrl (FVB) mice resulted in more M2 macrophages at week 1, more osteoclasts at week 2 and increased bone formation after week 4 compared with the results obtained in C57BL/6JOlaHsd (C57) mice. Similarly, in vitro, with a greater potential to form M2 macrophages, monocytes derived from FVB mice formed more osteoclasts than those derived from C57 mice. A transcriptomic analysis identified Csf1, Cxcr4 and Tgfbr2 as the main genes controlling macrophage-osteoclast coupling, which were further confirmed by related inhibitors. With such coupling, macrophage polarization and osteoclast formation of monocytes in vitro successfully predicted in vivo bone formation in four other mouse strains. Considering material-induced bone formation as an example of acquired heterotopic bone formation, the current findings shed a light on precision medicine for both bone regeneration and the treatment of pathological heterotopic bone formation.

Study on the influence of scaffold morphology and structure on osteogenic performance

The number of patients with bone defects caused by various bone diseases is increasing yearly in the aging population, and people are paying increasing attention to bone tissue engineering research. Currently, the application of bone tissue engineering mainly focuses on promoting fracture healing by carrying cytokines. However, cytokines implanted into the body easily cause an immune response, and the cost is high; therefore, the clinical treatment effect is not outstanding. In recent years, some scholars have proposed the concept of tissue-induced biomaterials that can induce bone regeneration through a scaffold structure without adding cytokines. By optimizing the scaffold structure, the performance of tissue-engineered bone scaffolds is improved and the osteogenesis effect is promoted, which provides ideas for the design and improvement of tissue-engineered bones in the future. In this study, the current understanding of the bone tissue structure is summarized through the discussion of current bone tissue engineering, and the current research on micro-nano bionic structure scaffolds and their osteogenesis mechanism is analyzed and discussed.

Study on the biological behaviors of CaP coatings with different morphology on carbon/carbon composites

In this work, we designed and fabricated a CaP composite bio-coating with different surface morphologies on a carbon/carbon (C/C) matrix by means of hybrid supersonic atmospheric plasma spraying (SAPS) and microwave-hydrothermal (MH) technologies. We found that all studied coating materials can support mesenchymal stem cells (MSCs) proliferation with prolonged culture time (3 days and 7 days) in vitro. Furthermore, according to the (Confocal Laser Scanning Microscopy) CLSM results, the MSCs also showed good attachment and different spreading morphologies on SAPS/MH coatings. As such, C/C matrix, the MH treated coatings with needle-like and rod-like microstructures were chosen for further in vivo investigation. Considering the good bonding between host tissue and the studied materials, the in vivo morphology studies confirmed a good histocompatibility for all coating samples, as well as a decreasing expression for inflammatory factors in a physiological environment. The histological results around the implants indicated different cell aggregation and vascularization ability in the local micro-environment. In particular, based on the reduction of the C/C initial surface flaws (e.g. hydrophobicity, biological inertia and easily producing carbon fragments or particles), the MH treated coating with rod-like surface morphology with a specific surface area (~2.33 m²/g) and roughness (~13.80 μm), showed excellent performance as a promising implant in live tissue.

Bone regeneration of a polymeric sponge technique-Alloplastic bone substitute materials compared with a commercial synthetic bone material (MBCP+TM technology): A histomorphometric study in porcine skull

Background

Polymeric sponge technique is recommended for developing the desired porosity of Biphasic calcium phosphate (BCP) which may favor bone regeneration.

Purpose

To investigate the healing of BCP with ratio of HA30/β‐TCP70 (HA30) and HA70/β‐TCP30 (HA70) polymeric sponge preparation, compare to commercial BCP (MBCP+TM).

Materials and Methods

Materials were tested X‐ray diffraction (XRD) pattern and scanning electron microscope (SEM) analysis. In eight male pigs, six calvarial defects were created in each subject. The defects were the filled with 1 cc of autogenous bone, MBCP+TM (MBCP), HA30, HA70, and left empty (negative group). The new bone formations, residual material particles and bone‐to‐graft contacts were analyzed at 4, 8, 12 and 16 weeks.

Results

Fabricated BCP showed well‐distributed porosity. At 16 weeks, new bone formations were 45.26% (autogenous), 33.52% (MBCP), 24.34% (HA30), 19.43% (HA70) and 3.37% (negative). Residual material particles were 1.88% (autogenous), 17.58% (MBCP), 26.74% (HA30) and 37.03% (HA70). These values were not significant differences (Bonferroni correction <0.005). Bone‐to‐graft contacts were 73.68% (MBCP), which was significantly higher than 41.68% (HA30) and 14.32% (HA70; Bonferroni correction <0.017).

Conclusions

Polymeric sponge technique offers well‐distributed porosity. The new bone formation and residual material particles were comparable to MBCP+TM, but the bone‐to‐graft contact was lower than MBCP+TM.

Protein adsorption and bioactivity of functionalized electrospun membranes for bone regeneration

OBJECTIVES

To evaluate the adsorption of bone related proteins and bioactivity of experimental functionalized (carboxylated or aminated) polymeric membranes for bone regeneration.

METHODS

Polymethylmethacrylate-based membranes functionalized with carboxyl or amino radicals were tested. Membranes were zinc loaded and the adsorption isotherms of zinc were studied. Human plasma proteins, bovine serum albumin, fibrinogen and fibronectin adsorption were measured with a spectrophotometer applying an acid determination protocol. Biomimetic calcium phosphate precipitation on polymeric membranes was also assessed after simulated body fluid immersion. Scanning electron microscopy and elemental analysis by means of an energy dispersive system were used for mineral deposits identification. A commercially available polytetrafluoroethylene membrane was used as control.

RESULTS

Both experimental membranes produced higher protein adsorption than the commercial control that does not adsorb proteins. Carboxylated membranes adsorbed significantly more albumin than the aminated ones, the opposite occurred with fibrinogen. With plasma and fibronectin proteins both type of membranes performed similarly. Only carboxylated membranes were bioactive and precipitated calcium and phosphate on their surfaces.

CONCLUSIONS

The polymethylmethacrylate zinc-loaded membranes functionalized with carboxyl groups performed as high adsorbable membranes for bone regeneration related proteins. They also served as templates for mineralization of hydroxyapatite.

CLINICAL SIGNIFICANCE

Protein adsorption is the initial reaction after the implantation of a biomaterial into the body and will influence subsequent cell function. The adsorption of bone related proteins together with the observed biomimetic calcium deposition on the experimental carboxylated membranes could be associated with their ability to promote bone regeneration.

Design of hydroxyapatite bioceramics with micro-/nano-topographies to regulate the osteogenic activities of bone morphogenetic protein-2 and bone marrow stromal cells

Biomimicking the nanostructure of natural bone apatite to enhance the bioactivity of hydroxyapatite (HA) biomaterials is an eternal topic in the bone regeneration field. In the present study, we designed four kinds of HA bioceramics with micro- to nanosized grains and investigated the effects of bioceramic topographies on the structures of bone morphogenetic protein-2 (BMP-2) and the effects on the responses of bone marrow stromal cells (BMSCs). Compared to the samples with submicron-scale crystalline particles, HA bioceramics with grain sizes of 104.6 ± 27.8 nm exhibited increased roughness, improved hydrophilicity and enhanced mechanical properties. The synergistic effects of these surface characteristics could well maintain the conformation of BMP-2, facilitate cell adhesion and spreading, and activate the osteogenic differentiation of BMSCs. Furthermore, SBF immersion and in vivo canine intramuscular implantation confirmed that the HA bioceramics with nanotopography also processed excellent bone-like apatite forming ability and outstanding osteoinductivity. In summary, these findings suggest that the nanotopography of HA bioceramics is a critical factor to enhance their bioactivity and osteoinductivity.

The role of calcium phosphate surface structure in osteogenesis and the mechanisms involved

Calcium phosphate (CaP) ceramics have been widely used for bone regeneration because of their ability to induce osteogenesis. Surface properties, including chemical composition and surface structure, are known to play a crucial role in osteoconduction and osteoinduction. This review systematically analyzes the effects of surface properties, in particular the surface structure, of CaP scaffolds on cell behavior and new bone formation. We also summarize the possible signaling pathways involved in the osteogenic differentiation of bone-related cells when cultured on surfaces with various structures in vitro. The significant immune response initiated by surface structure involved in osteogenic differentiation of cells is also discussed in this review. Taken together, the new biological principle for advanced biomaterials is not only to directly stimulate osteogenic differentiation of bone-related cells but also to modulate the immune response in vivo. Although the reaction mechanism responsible for bone formation induced by CaP surface structure is not clear yet, the insights on surface structure-mediated osteogenic differentiation and osteoimmunomodulation could aid the optimization of CaP-based biomaterials for bone regeneration. STATEMENT OF SIGNIFICANCE: CaP ceramics have similar inorganic composition with natural bone, which have been widely used for bone tissue scaffolds. CaP themselves are not osteoinductive; however, osteoinductive properties could be introduced to CaP materials by surface engineering. This paper systematically summarizes the effects of surface properties, especially surface structure, of CaP scaffolds on bone formation. Additionally, increasing evidence has proved that the bone healing process is not only affected by the osteogenic differentiation of bone-related cells, but also relevant to the the cooperation of immune system. Thus, we further review the possible signaling pathways involved in the osteogenic differentiation and immune response of cells cultured on scaffold surface. These insights into surface structure-mediated osteogenic differentiation and osteoimmunomodulated-based strategy could aid the optimization of CaP-based biomaterials.

Effect of surface microstructure on the anti-fibrosis/adhesion of hydroxyapatite ceramics in spinal repair of rabbits

Epidural adhesion is a great clinical challenge after laminectomy. In the present study, two types of hydroxyapatite (HA) laminas with distinct surface microstructures were prepared by cold isostatic pressing (CIP) and slip casting (SC) techniques, and investigated to their anti-fibrosis/adhesion effects by in vitro and in vivo evaluations. In contrast with the dense HA-CIP, HA-SC had a large number of micropores on the surface. After cultured on both HA ceramics, human skin fibroblasts presented the obvious senescent feature, and CCN1 gene expression was significantly up-regulated. HA-SC induced higher CCN1 gene expression than HA-CIP. After used for closing the lost vertebral after laminectomy in rabbits, both HA laminas promoted the recovery of the bony structure as well as prevented the hyperplastic fibrous tissue from penetration into the spinal canal area and inhibited the formation of scar-like tissue in laminectomy sites to some extent. Besides, thinner layer of fibrous tissue and smaller gap between the implant surface and paravertebral muscles were found in HA-CIP than HA-SC. Therefore, HA ceramics could have good anti-fibrosis/adhesion effect when used in spinal repair, and the dense HA-CIP could be an ideal choice. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2629-2637, 2019.

Osteogenesis of 3D printed macro-pore size biphasic calcium phosphate scaffold in rabbit calvaria

To investigate the osteogenesis of macro-pore sized bone scaffolds, biphasic calcium phosphate scaffolds with accurately controlled macro-pore size (0.8, 1.2, and 1.6 mm) and identical porosity of 70% were fabricated by the 3D printing technology. Eight New Zealand rabbits were selected in the present study, while four 8-mm-diameter calvarial defects were created in each rabbit to place BCP scaffolds with different macro-pore size. The harvested specimens of four and eight weeks were used to evaluate the bone forming ability by micro CT and histological examination. All 3D-printed BCP scaffolds exhibited excellent mechanical properties and had better bone-forming ability than the control at both four and eight weeks. Among them, scaffold with 0.8 mm pore size was superior for initial bone formation and maturation, resulting in the highest value of total bone formation.

A serum protein adsorption profile on BCP ceramics and influence of the elevated adsorption of adhesive proteins on the behaviour of MSCs

Protein adsorption plays a key role in bone repair and regeneration by affecting cell behavior. In this study, a biphasic calcium phosphate (BCP) ceramic, with excellent osteoinductivity, was chosen to investigate its serum protein adsorption profile using isobaric tags for relative and absolute quantification (iTRAQ) proteomics technology. 281 differentially adsorbed serum proteins and the involved biological processes were confirmed by the combination of Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The differentially adsorbed adhesive proteins in the extracellular matrix (ECM)-receptor interaction pathway were further selected to investigate their roles in the behavior of mesenchymal stem cells (MSCs). Pre-coating and blockage experiments revealed that both adsorbed vitronectin (VN) and laminin (LN) could promote the attachment, proliferation and osteogenic differentiation of MSCs on the BCP ceramic by interacting with different integrin subunits. It is revealed that the up-regulated expressions of integrin α2, αv and β3, β5 could contribute to VN-mediated MSC functions, and the elevated gene expressions of α6 and β1, β4 could be related to the LN-participated process. The above results proved that the preferential protein adsorption on a biomaterial should be vital for modulating MSC functions in the course of material-mediated osteoinductivity.

Combined delivery of bone morphogenetic protein-2 and insulin-like growth factor-1 from nano-poly (γ-glutamic acid)/β-tricalcium phosphate-based calcium phosphate cement and its effect on bone regeneration in vitro

In this study, nano-doped calcium phosphate cement delivery systems (poly (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramics and nano (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramic) were fabricated, and low doses (10 µg/g) of two growth factors, insulin-like growth factor-1 and bone morphogenetic protein-2, were encapsulated then sequentially released. We characterized the delivery systems using Fourier transform infrared spectroscopy and X-ray diffraction and measured washout resistance and compressive strength, and thus optimized the most appropriate proportioning of delivery systems for the two growth factors. One of the growth factors was absorbed by the nano-poly (γ-glutamic acid)/β-tricalcium phosphate, which was then mixed into the calcium phosphate ceramic solid phase to create a new solid phase calcium phosphate ceramic. Nano-poly (γ-glutamic acid)/β-tricalcium phosphate/calcium phosphate ceramic carriers were then prepared by blending the new calcium phosphate ceramic solid phase powder with a solution of the remaining growth factor. The effects of different release patterns (studying sequential behavior) of insulin-like growth factor-1 and bone morphogenetic protein-2 on osteogenic proliferation and differentiation of the MC3t3-E1 mouse osteoblast cell were investigated. This combinational delivery system provided a controlled release of the two growth factors, in which nano-doping significantly affected their release kinetics. The incorporation of dual growth factors could potentially stimulate bone healing and promoting bone ingrowth processes at a low dose.

The directional migration and differentiation of mesenchymal stem cells toward vascular endothelial cells stimulated by biphasic calcium phosphate ceramic

Osteoinductivity of porous calcium phosphate (CaP) ceramics has been widely investigated and confirmed, and it might be attributed to the rapid formation of the vascular networks after in vivo implantation of the ceramics. In this study, to explore the vascularization mechanism within the CaP ceramics, the migration and differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) under the stimulation of porous biphasic calcium phosphate (BCP) ceramic with excellent osteoinductivity were systematically investigated. The results indicated that the directional migration of BMSCs toward BCP ceramic occurred when evaluated by using a transwell model, and the BMSCs migration was enhanced by the seeded macrophages on the ceramic in advance. Besides, by directly culturing BMSCs on BCP ceramic discs under both in vitro and in vivo physiological environment, it was found that the differentiation of BMSCs toward vascular endothelial cells (VECs) happened under the stimulation of BCP ceramic, as was confirmed by the up-regulated gene expressions and protein secretions of VECs-related characteristic factors, including kinase insert domain receptor, von willebrand factor, vascular cell adhesion molecule-1 and cadherin 5 in the BMSCs. This study offered a possibility for explaining the origin of VECs during the rapid vascularization process after in vivo implantation of porous CaP ceramics and could give some useful guidance to reveal the vascularization mechanism of the ceramics.

Guangxi cobra venom-derived NGF promotes the osteogenic and therapeutic effects of porous BCP ceramic

Neuro-osteological interactions have an important role in the regulation of bone metabolism and regeneration. Neuropeptides combined with porous biphasic calcium phosphates (BCP) using protein adsorption may contribute to the acceleration of bone formation. In the present study, we investigated the effect of BCP combined with nerve growth factor (NGF) on the growth of osteoblasts in vitro and the combinational therapeutic effect on the repair of calvarial defects in vivo. NGF was separated and purified from Chinese cobra venom using a simplified three-step chromatography method. BCP combined with NGF exerted a potent effect on osteoblast differentiation, as evidenced by enhanced cell proliferation, increased ALP activity and the up-regulated expression of osteogenesis-related genes and proteins. Further, combinational therapy with BCP and NGF improved calvarial regeneration, which was superior to treatment with therapy alone, as observed using imageological and morphological examination and histological and immunohistochemical staining. The results confirmed the effect of neuro-osteological interactions through combinatorial treatment with NGF and BCP to promote osteogenesis and bone formation, which may provide an effective and economical strategy for clinical application.

Linking the Transcriptional Landscape of Bone Induction to Biomaterial Design Parameters

New engineering possibilities allow biomaterials to serve as active orchestrators of the molecular and cellular events of tissue regeneration. Here, the molecular control of tissue regeneration for calcium phosphate (CaP)-based materials is established by defining the parameters critical for tissue induction and those are linked to the molecular circuitry controlling cell physiology. The material properties (microporosity, ion composition, protein adsorption) of a set of synthesized osteoinductive and noninductive CaP ceramics are parameterized and these properties are correlated to a transcriptomics profile of osteogenic cells grown on the materials in vitro. Using these data, a genetic network controlling biomaterial-induced bone formation is built. By isolating the complex material properties into single-parameter test conditions, it is verified that a subset of these genes is indeed controlled by surface topography and ions released from the ceramics, respectively. The gene network points to a decisive role for extracellular matrix deposition in osteoinduction by genes such as tenascin C and hyaluronic acid synthase 2, which are controlled by calcium and phosphate ions as well as surface topography. This work provides insight into the biomaterial composition and material engineering aspects of bone void filling and can be used as a strategy to explore the interface between biomaterials and tissue regeneration.

Scaffolds for hand tissue engineering: the importance of surface topography

Tissue engineering is believed to have great potential for the reconstruction of the hand after trauma, congenital absence and tumours. Due to the presence of multiple distinct tissue types, which together function in a precisely orchestrated fashion, the hand counts among the most complex structures to regenerate. As yet the achievements have been limited. More recently, the focus has shifted towards scaffolds, which provide a three-dimensional framework to mimic the natural extracellular environment for specific cell types. In particular their surface structures (or topographies) have become a key research focus to enhance tissue-specific cell attachment and growth into fully functioning units. This article reviews the current understanding in hand tissue engineering before focusing on the potential for scaffold topographical features on micro- and nanometre scales to achieve better functional regeneration of individual and composite tissues.

Effect of calcium phosphate coating and rhBMP-2 on bone regeneration in rabbit calvaria using poly(propylene fumarate) scaffolds

Various calcium phosphate based coatings have been evaluated for better bony integration of metallic implants and are currently being investigated to improve the surface bioactivity of polymeric scaffolds. The aim of this study was to evaluate the role of calcium phosphate coating and simultaneous delivery of recombinant human bone morphogenetic protein-2 (rhBMP-2) on the in vivo bone regeneration capacity of biodegradable, porous poly(propylene fumarate) (PPF) scaffolds. PPF scaffolds were coated with three different calcium phosphate formulations: magnesium-substituted β-tricalcium phosphate (β-TCMP), carbonated hydroxyapatite (synthetic bone mineral, SBM) and biphasic calcium phosphate (BCP). In vivo bone regeneration was evaluated by implantation of scaffolds in a critical-sized rabbit calvarial defect loaded with different doses of rhBMP-2. Our data demonstrated that scaffolds with each of the calcium phosphate coatings were capable of sustaining rhBMP-2 release and retained an open porous structure. After 6weeks of implantation, micro-computed tomography revealed that the rhBMP-2 dose had a significant effect on bone formation within the scaffolds and that the SBM-coated scaffolds regenerated significantly greater bone than BCP-coated scaffolds. Mechanical testing of the defects also indicated restoration of strength in the SBM and β-TCMP with rhBMP-2 delivery. Histology results demonstrated bone growth immediately adjacent to the scaffold surface, indicating good osteointegration and osteoconductivity for coated scaffolds. The results obtained in this study suggest that the coated scaffold platform demonstrated a synergistic effect between calcium phosphate coatings and rhBMP-2 delivery and may provide a promising platform for the functional restoration of large bone defects.

Bone regenerative efficacy of biphasic calcium phosphate collagen composite as a carrier of rhBMP-2

OBJECTIVES

This study compared the bone regenerative effects of a recombinant human bone morphogenetic protein 2 (rhBMP-2)-loaded collagen-based biphasic calcium phosphate composite (BCPC) and rhBMP-2-loaded biphasic calcium phosphate (BCP).

MATERIAL AND METHODS

The in vitro release profiles of rhBMP-2-loaded BCP and BCPC were measured. The animal surgery was performed on ten rabbits. Four 8-mm-diameter circular calvarial defects were made and filled with BCP, BCPC, rhBMP-2-loaded BCP (BMP + BCP) and rhBMP-2-loaded BCPC (BMP + BCPC). The animals were euthanized either 2 or 8 weeks after surgery.

RESULTS

The initial burst release of rhBMP-2 was greater for BCP than for BCPC, and both presented a slow release pattern thereafter. In rabbit calvarial defects, the space maintaining capability and graft resorption of all experimental groups did not show statistical differences at 2 and 8 weeks. New bone formation in the rhBMP-2-loaded groups was greater than in the non-loaded groups at both weeks, but the amount of new bone was comparable between both rhBMP-2-loaded groups at both weeks. There was a distinct histologic difference between the BMP + BCP and BMP + BCPC groups at 2 weeks; the new bone formation occurred more in the intergranular spaces and the BCP-to-bone contact was greater in the BMP + BCPC group, but these differences were no longer discernible at 8 weeks.

CONCLUSIONS

BCP- and BCPC-loaded rhBMP-2 significantly improved bone regeneration and BCPC led to a dense network of new bone and bone particles during the early healing period. BCPC can therefore be considered as a promising candidate for carrying rhBMP-2.

Vertical bone regeneration with deproteinised bovine bone mineral or biphasic calcium phosphate in the rabbit calvarium: effect of autologous platelet lysate

Although bone substitutes associated with platelet concentrates are widely used to vertically reconstruct alveolar ridges, their respective and specific contribution remain controversial. The aim of this study was to evaluate the benefit of using either biphasic calcium phosphate (BCP) or demineralised bovine bone mineral (DBBM) alone or with autologous platelet lysate (APL) in vertical bone regeneration. The study involved fourteen New Zealand rabbits. Autologous APL was prepared by freeze-thawing from a platelet suspension (10(9) platelets/ml). Four CP titanium (cpTi) cylinders were fixed to each calvarium; one cylinder was empty, one was filled with APL alone and the others were filled either with BCP or BCP + APL or DBBM or DBBM + APL. New bone formation and biomaterial resorption were evaluated using non-demineralised histology and histomorphometry. After 6 weeks, new bone formation was observed in all cylinders. The newly formed bone in the cylinders filled with APL alone, DBBM and BCP was significantly increased by (0.6-, 2.5- and 3.3-fold, respectively) (P < 0.0001) compared to results obtained with the empty cylinders. Vertical bone height in the cylinders filled with BCP was greater to that observed with DBBM. The residual material in the cylinders filled with BCP was significantly (P < 0.0001) lower (0.35-fold) than that with DBBM. Both newly formed bone and residual material in the cylinders filled with BCP + APL or DBBM + APL were similar to those filled with either BCP or DBBM, respectively. This study provided evidence that APL alone, as well as DBBM and BCP, have a beneficial effect on vertical bone formation and remodelling. APL associated with either DBBM or BCP did not provide additional benefits.

Biomaterials for in situ tissue regeneration: development and perspectives

Biomaterials are of fundamental importance to in situ tissue regeneration, which has emerged as a powerful method to treat tissue defects. The development and perspectives of biomaterials for in situ tissue regeneration were summarized.

Adsorption, aggregation, and desorption of proteins on smectite particles

We report on adsorption of lysozyme (LYS), ovalbumin (OVA), or ovotransferrin (OVT) on particles of a synthetic smectite (synthetic layered aluminosilicate). In our approach we used atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to study the protein-smectite systems in water solutions at pH ranging from 4 to 9. The AFM provided insights into the adhesion forces of protein molecules to the smectite particles, while the QCM measurements yielded information about the amounts of the adsorbed proteins, changes in their structure, and conditions of desorption. The binding of the proteins to the smectite surface was driven mainly by electrostatic interactions, and hence properties of the adsorbed layers were controlled by pH. At high pH values a change in orientation of the adsorbed LYS molecules and a collapse or desorption of OVA layer were observed. Lowering pH to the value ≤ 4 caused LYS to desorb and swelling the adsorbed OVA. The stability of OVT-smectite complexes was found the lowest. OVT revealed a tendency to desorb from the smectite surface at all investigated pH. The minimum desorption rate was observed at pH close to the isoelectric point of the protein, which suggests that nonspecific interactions between OVT and smectite particles significantly contribute to the stability of these complexes.

Chitosan-based scaffolds for bone tissue engineering

Bone defects requiring grafts to promote healing are frequently occurring and costly problems in health care. Chitosan, a biodegradable, naturally occurring polymer, has drawn considerable attention in recent years as scaffolding material in tissue engineering and regenerative medicine. Chitosan is especially attractive as a bone scaffold material because it supports the attachment and proliferation of osteoblast cells as well as formation of mineralized bone matrix. In this review, we discuss the fundamentals of bone tissue engineering and the unique properties of chitosan as a scaffolding material to treat bone defects for hard tissue regeneration. We present the common methods for fabrication and characterization of chitosan scaffolds, and discuss the influence of material preparation and addition of polymeric or ceramic components or biomolecules on chitosan scaffold properties such as mechanical strength, structural integrity, and functional bone regeneration. Finally, we highlight recent advances in development of chitosan-based scaffolds with enhanced bone regeneration capability.

Evaluation of the cytocompatibility hemocompatibility in vivo bone tissue regenerating capability of different PCL blends

In this study, the optimized formulations of polycaprolactone (PCL) combined with poly(lactic-co-glycolic acid) (PLGA), gelatin (GEL), and biphasic calcium phosphate (BCP) were analyzed in terms of cytocompatibility with bone-related cells, hemocompatibility, and in vivo bone-regenerating capacity to determine their potentials for bone tissue regeneration. Fiber morphology of PCL/GEL and PCL/BCP electrospun mats considerably differs from that of the PCL membrane. Based on the contact angle analyses, the addition of GEL and PLGA was shown to reduce the hydrophobicity of these membranes. The assessment of in vitro cytocompatibility using MC3T3-E1 cells indicated that all of the membranes were suitable for pre-osteoblast proliferation and adhesion, with PCL/BCP having a significantly higher reading after seven days of incubation. The results of the in vitro hemocompatibility of the different fibrous scaffolds suggest that coagulation and platelet adhesion were higher for hydrophobic membranes (PCL and PCL/PLGA), while hemolysis can be associated with fiber morphology. The potential of the membranes for bone regeneration was determined by analyzing the microCT data and tissue sections of samples implanted in 5 mm sized defects (one and two months). Although all of the membranes were suitable for pre-osteoblast proliferation, in vivo bone regeneration after two months was found to be significantly higher in PCL/BCP (p < 0.001).