Preparation and characterization of amine functional nano-hydroxyapatite/chitosan bionanocomposite for bone tissue engineering applications

Fabrication and properties of hydroxyapatite/chitosan composite scaffolds loaded with periostin for bone regeneration

This paper reports a facile fabrication method of hydroxyapatite/chitosan (HAp/CS) composite scaffold with 3D porous structure without using any chemical cross-linkers. The HAp particles had an urchin-like hollow microstructure and high surface area, which was uniformly dispersed into the pore walls of the HAp/CS scaffold. The addition of HAp can efficiently enhance the mechanical properties and bioactivity of the HAp/CS scaffold. Moreover, periostin was successfully loaded onto the HAp/CS scaffold. When applied to the repair of bone defect in a rat mandibular model, the HAp/CS scaffold loaded with periostin can enhance osteointegration and accelerate bone regeneration. Our research combines periostin with the HAp/CS composite material, which provides a novel strategy to improve bone regeneration and has great application prospect in bone repair fields.

Eco-friendly synthesis of mesoporous bioactive glass ceramics and functionalization for drug delivery and hard tissue engineering applications

Hard tissue regenerative mesoporous bioactive glass (MBG) has traditionally been synthesized using costly and toxic alkoxysilane agents and harsh conditions. In this study, MBG was synthesized using the cheaper reagent SiO2by using a co-precipitation approach. The surface properties of MBG ceramic were tailored by functionalizing with amino and carboxylic groups, aiming to develop an efficient drug delivery system for treating bone infections occurring during or after reconstruction surgeries. The amino groups were introduced through a salinization reaction, while the carboxylate groups were added via a chain elongation reaction. The MBG, MBG-NH2, and MBG-NH-COOH were analyzed by using various techniques: x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy and energy-dispersive x-ray spectroscopy. The XRD results confirmed the successful preparation of MBG, and the FTIR results indicated successful functionalization. BET analysis revealed that the prepared samples were mesoporous, and functionalization tuned their surface area and surface properties. Cefixime, an antibiotic, was loaded onto MBG, MBG-NH2, and MBG-NH-COOH to test their drug-carrying capacity. Comparatively, MBG-NH-COOH showed good drug loading and sustained release behavior. The release of the drug followed the Fickian diffusion mechanism. All prepared samples displayed favorable biocompatibility at higher concentration in the Alamar blue assay with MC3T3 cells and exhibited the good potential for hard tissue regeneration, as carbonated hydroxyapatite formed on their surfaces in simulated body fluid.

An osteoporosis bone defect regeneration strategy via three-dimension short fibers loaded with alendronate modified hydroxyapatite

Osteoporotic bone defect has become clinic challenge due to its morbid bone microenvironment. Overactive bone resorption and limited bone formation lead to unstable combination between bone tissue and scaffolds. Electrospinning has been widely used in guide tissue membrane, but its barrier property results in limited application. In order to optimize the structure and add anti-bone resorption function of electrospinning fibers, we exploited the application of short fibers generated by homogenization at osteoporotic tibial bone defect. The modified nano-hydroxyapatite (m-HA) was loaded with alendronate. It overcame the problem that hydrophilic drugs were difficult to distribute uniformly in hydrophobic fibers. We confirmed that m-HA was loaded into polycaprolactone (PCL) short fibers. PCL short fibers with m-HA (PCL/m-HA) continuously released ALN, provided stable structure and showed good cytocompatibility. In vitro, PCL/m-HA increased the activity of alkaline phosphatase (ALP), promoted extracellular matrix mineralization and upregulated the expression of osteogenesis-related genes, Col 1, Alp, osteopontin (Opn) and runt-related transcription factor 2 (Runx2). In vivo, PCL/m-HA short fibers accelerated the new bone formation, inhibited the bone resorption and rebalanced the bone microenvironment through regulating osteoprotegerin (OPG) /receptor activator of NF-kB (RANKL) ratio. The above results confirmed that the PCL/m-HA short fibers achieved the application of three-dimension osteoporotic bone defect and had potential prospects in bone tissue scaffolds.

Nanomaterials-incorporated hydrogels for 3D bioprinting technology

In the field of tissue engineering and regenerative medicine, various hydrogels derived from the extracellular matrix have been utilized for creating engineered tissues and implantable scaffolds. While these hydrogels hold immense promise in the healthcare landscape, conventional bioinks based on ECM hydrogels face several challenges, particularly in terms of lacking the necessary mechanical properties required for 3D bioprinting process. To address these limitations, researchers are actively exploring novel nanomaterial-reinforced ECM hydrogels for both mechanical and functional aspects. In this review, we focused on discussing recent advancements in the fabrication of engineered tissues and monitoring systems using nanobioinks and nanomaterials via 3D bioprinting technology. We highlighted the synergistic benefits of combining numerous nanomaterials into ECM hydrogels and imposing geometrical effects by 3D bioprinting technology. Furthermore, we also elaborated on critical issues remaining at the moment, such as the inhomogeneous dispersion of nanomaterials and consequent technical and practical issues, in the fabrication of complex 3D structures with nanobioinks and nanomaterials. Finally, we elaborated on plausible outlooks for facilitating the use of nanomaterials in biofabrication and advancing the function of engineered tissues.

Viability of Collagen Matrix Grafts Associated with Nanohydroxyapatite and Elastin in Bone Repair in the Experimental Condition of Ovariectomy

Bone lesions have the capacity for regeneration under normal conditions of the bone metabolism process. However, due to the increasing incidence of major traumas and diseases that cause bone-mineral deficiency, such as osteoporosis, scaffolds are needed that can assist in the bone regeneration process. Currently, natural polymeric scaffolds and bioactive nanoparticles stand out. Therefore, the objective of the study was to evaluate the osteoregenerative potential in tibiae of healthy and ovariectomized rats using mineralized collagen and nanohydroxyapatite (nHA) scaffolds associated with elastin. The in-vivo experimental study was performed with 60 20-week-old Wistar rats, distributed into non-ovariectomized (NO) and ovariectomized (O) groups, as follows: Controls (G1-NO-C and G4-O-C); Collagen with nHA scaffold (G2-NO-MSH and G5-O-MSH); and Collagen with nHA and elastin scaffold (G3-NO-MSHC and G6-O-MSHC). The animals were euthanized 6 weeks after surgery and the samples were analyzed by macroscopy, radiology, and histomorphometry. ANOVA and Tukey tests were performed with a 95% CI and a significance index of p < 0.05. In the histological analyses, it was possible to observe new bone formed with an organized and compact morphology that was rich in osteocytes and with maturity characteristics. This is compatible with osteoconductivity in both matrices (MSH and MSHC) in rats with normal conditions of bone metabolism and with gonadal deficiency. Furthermore, they demonstrated superior osteogenic potential when compared to control groups. There was no significant difference in the rate of new bone formation between the scaffolds. Ovariectomy did not exacerbate the immune response but negatively influenced the bone-defect repair process.

β-Tricalcium Phosphate-Loaded Chitosan-Based Thermosensitive Hydrogel for Periodontal Regeneration

The current treatment for periodontitis is aimed at resolving gingival inflammation, whilst complete periodontal tissue regeneration is not predictable, and it represents a therapeutic challenge. Injectable biomaterials hold tremendous potential in dental tissue regeneration. This study aimed to investigate the ability of an injectable thermosensitive β-tricalcium phosphate (β-TCP) and chitosan-based hydrogel to carry cells and promote periodontal tissue regeneration. In this study, different concentrations of β-TCP-loaded chitosan hydrogels were prepared (0%, 2%, 4%, or 6% β-TCP, 10% β-glycerol phosphate, and 1.5% chitosan). The characteristics of the hydrogels were tested using rheology, a scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), degradation, and biological analyses. The new biomaterial showed a sol-gel transformation ability at body temperature and exhibited excellent chemical and physical characteristics, whilst the existence of β-TCP enhanced the structure and the properties of the hydrogels. The SEM confirmed the three-dimensional networks of the hydrogels, and the typical rheological properties of strong gel were observed. The EDX and XRD validated the successful incorporation of β-TCP, and similar patterns between different groups were found in terms of the FTIR spectra. The stable structure of the hydrogels under 100 °C was confirmed via DSC. Biological tests such as Alamar Blue assay and Live/Dead staining confirmed the remarkable biocompatibility of the hydrogels with pre-osteoblast MC3T3-E1 and human gingival fibroblast (HGF) cells for 14 days, and the results were validated with confocal imaging. This preliminary study shows great promise for the application of the β-TCP-loaded thermosensitive chitosan hydrogels as a scaffold in periodontal bone and soft tissue repair.

Nanostructured 3D-Printed Hybrid Scaffold Accelerates Bone Regeneration by Photointegrating Nanohydroxyapatite

Nanostructured biomaterials that replicate natural bone architecture are expected to facilitate bone regeneration. Here, nanohydroxyapatite (nHAp) with vinyl surface modification is acquired by silicon-based coupling agent and photointegrated with methacrylic anhydride-modified gelatin to manufacture a chemically integrated 3D-printed hybrid bone scaffold (75.6 wt% solid content). This nanostructured procedure significantly increases its storage modulus by 19.43-fold (79.2 kPa) to construct a more stable mechanical structure. Furthermore, biofunctional hydrogel with biomimetic extracellular matrix is anchored onto the filament of 3D-printed hybrid scaffold (HGel-g-nHAp) by polyphenol-mediated multiple chemical reactions, which contributes to initiate early osteogenesis and angiogenesis by recruiting endogenous stem cells in situ. Significant ectopic mineral deposition is also observed in subcutaneously implanted nude mice with storage modulus enhancement of 25.3-fold after 30 days. Meanwhile, HGel-g-nHAp realizes substantial bone reconstruction in the rabbit cranial defect model, achieving 61.3% breaking load strength and 73.1% bone volume fractions in comparison to natural cranium 15 weeks after implantation. This optical integration strategy of vinyl modified nHAp provides a prospective structural design for regenerative 3D-printed bone scaffold.

Nano-Hydroxyapatite Composite Scaffolds Loaded with Bioactive Factors and Drugs for Bone Tissue Engineering

Nano-hydroxyapatite (n-HAp) is similar to human bone mineral in structure and biochemistry and is, therefore, widely used as bone biomaterial and a drug carrier. Further, n-HAp composite scaffolds have a great potential role in bone regeneration. Loading bioactive factors and drugs onto n-HAp composites has emerged as a promising strategy for bone defect repair in bone tissue engineering. With local delivery of bioactive agents and drugs, biological materials may be provided with the biological activity they lack to improve bone regeneration. This review summarizes classification of n-HAp composites, application of n-HAp composite scaffolds loaded with bioactive factors and drugs in bone tissue engineering and the drug loading methods of n-HAp composite scaffolds, and the research direction of n-HAp composite scaffolds in the future is prospected.

Advances in osseointegration of biomimetic mineralized collagen and inorganic metal elements of natural bone for bone repair

At this stage, bone defects caused by trauma, infection, tumor, or congenital diseases are generally filled with autologous bone or allogeneic bone transplantation, but this treatment method has limited sources, potential disease transmission and other problems. Ideal bone-graft materials remain continuously explored, and bone defect reconstruction remains a significant challenge. Mineralized collagen prepared by bionic mineralization combining organic polymer collagen with inorganic mineral calcium phosphate can effectively imitate the composition and hierarchical structure of natural bone and has good application value in bone repair materials. Magnesium, strontium, zinc and other inorganic components not only can activate relevant signaling pathways to induce differentiation of osteogenic precursor cells but also stimulate other core biological processes of bone tissue growth and play an important role in natural bone growth, and bone repair and reconstruction. This study reviewed the advances in hydroxyapatite/collagen composite scaffolds and osseointegration with natural bone inorganic components, such as magnesium, strontium and zinc.

Synthetic biodegradable polymer materials in the repair of tumor-associated bone defects

The repair and reconstruction of bone defects and the inhibition of local tumor recurrence are two common problems in bone surgery. The rapid development of biomedicine, clinical medicine, and material science has promoted the research and development of synthetic degradable polymer anti-tumor bone repair materials. Compared with natural polymer materials, synthetic polymer materials have machinable mechanical properties, highly controllable degradation properties, and uniform structure, which has attracted more attention from researchers. In addition, adopting new technologies is an effective strategy for developing new bone repair materials. The application of nanotechnology, 3D printing technology, and genetic engineering technology is beneficial to modify the performance of materials. Photothermal therapy, magnetothermal therapy, and anti-tumor drug delivery may provide new directions for the research and development of anti-tumor bone repair materials. This review focuses on recent advances in synthetic biodegradable polymer bone repair materials and their antitumor properties.

Zinc substituted hydroxyapatite/silk fiber/methylcellulose nanocomposite for bone tissue engineering applications

Fibrous bio-composite based on silk fiber (SF), methylcellulose (MC) and zinc substituted hydroxyapatite (Zn_xCa_5-x (PO₄)₃(OH) (x = 0.1, 0.2, 0.5 and 1.0)) were obtained with the use of electrospinning (E-Spin) method. XRD, FTIR, SEM-EDAX, swelling, porosity and mechanical properties of the composites were analyzed. The elongation at break (%) (20.97-317.20 %) and tensile strength (29.85-110.92 MPa) of nanocomposites was increased with an increase in the wt% of Zn-HAP in SF/MC. An increase in the zone of inhibition with an increase in the wt% of Zn-HAP into the SF/MC was observed against E. coli (34 ± 0.33 to 47 ± 1.15), S. aureus (28 ± 0.24 to 38 ± 1.32) and C. albicans (24 ± 0.36 to 39 ± 2.36). The in-vitro biomineralization study using SBF (simulated body fluid) showed apatite layer formation on the nano-composite. In addition, the optimized (20 wt % of Zn₁.₀Ca_4.0(PO₄)₃(OH)/SF/MC) nano-composite showed good cell viability against human bone osteosarcoma (MG-63) cells.

Chitosan-CaP microflowers and metronidazole loaded calcium alginate sponges with enhanced antibacterial, hemostatic and osteogenic properties for the prevention of dry socket after tooth removal

Tooth removal, particularly for patients with severe periodontitis, can frequently cause massive bleeding, postoperative infection, and bone resorption, resulting in a dry socket. Thus, developing bio-multifunctional materials with excellent antibacterial, hemostatic, and osteogenic characteristics for the prevention of dry sockets after tooth removal is highly desirable in clinical applications. Herein, chitosan-CaP microflowers (CM) and metronidazole (MD) loaded calcium alginate (CA) sponges (CA@CM/MD) with enhanced antibacterial, hemostatic, and osteogenic properties were developed via Ca²⁺ crosslinking, lyophilization, and electrostatic interaction for the prevention of dry socket after tooth removal. The fabricated CM particles display 3-dimensional, relatively homogeneous, and flower-shaped architectures. The CA@CM/MD composite sponges were facilely shaped into the tooth root as well as exhibit interconnected porous and lamellar structures with remarkable porosity, suitable maximum swelling ratio, as well as excellent compressive and hemostatic performance. Besides, the in vitro cellular assessment demonstrates that the prepared CA@CM/MD composite sponges possess satisfactory cytocompatibility. Importantly, the designed sponges significantly suppress the growth of S. aureus and E. coli, as well as promote cellular osteogenic differentiation by upregulating the formation of alkaline phosphatase. Our findings indicate that the tooth root-shaped composite sponges hold great promise for wound management after tooth removal.

3D gel-printed porous magnesium scaffold coated with dibasic calcium phosphate dihydrate for bone repair in vivo

Background

/Objective: The treatment of bone defect has always been a difficult problem in orthopedic clinic. The search for alternative biodegradable implants is a hot topic. The development of biodegradable magnesium scaffolds for the treatment of bone defects has long been a goal of the public.

Methods

In this study, we proposed a porous magnesium scaffold prepared by 3D gel printing and surface modification with an additional calcium phosphate coating and use of its strength, degradability and slow degradation rate in a bone graft substitute material. The porous magnesium granular scaffold was prepared by 3D gel printing technology and modified by DCPD (Dibasic Calcium Phosphate Dihydrate) coating. The biocompatibility, degradation rate, and osteogenic ability of the scaffold were evaluated in vitro and in vivo.

Results

The biocompatibility, in vivo degradation and bone defect healing response of the implants were investigated. Porous magnesium scaffolds were successfully prepared, and the strength of sintered scaffolds reached 5.38 ​MPa. The degradation rates of scaffolds were significantly reduced after coating with DCPD. The cell compatibility evaluation showed that DCPD-coated Mg scaffold was suitable for cell proliferation. In vivo biosafety monitoring showed that scaffold implantation did not cause an increase in Mg ion concentration in vivo, and no toxic damage was detected in the liver or kidney. Micro-CT and pathological results showed that a large amount of new bone was formed at 6 weeks. At 12 weeks, approximately 52% of the scaffold volume remained. At 24 weeks, osteogenesis, which was stimulated by some residual scaffold, still can be observed. In summary, this study suggests that 3D gel-printed DCPD-coated porous magnesium scaffolds have great potential as bone graft alternatives.

Conclusion

In summary, this study suggests that 3D gel-printed DCPD-coated porous magnesium scaffolds have great potential as bone graft alternatives.

The Translational potential of this article

The translational potential of this article is to make use of the advantages of 3D gel printing technology with higher efficiency and lower cost compared with SLM and SLS technologies, and use pure magnesium powder as raw material to prepare degradable porous magnesium metal scaffolds, opening up a new technical route for the preparation of degradable porous magnesium scaffolds which are made for bone defect regeneration in the future.

Fabrication of Novel Chitosan–Hydroxyapatite Nanostructured Thin Films for Biomedical Applications

In this study, we develop chitosan–hydroxyapatite (CS–HAp) composite layers that were deposited on Si substrates in radio frequency (RF) magnetron sputtering discharge in argon gas. The composition and structure of CS–HAp composite layers were investigated by analytical techniques, such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), metallographic microscopy (MM), and atomic force microscopy (AFM). On the other hand, in the present study the second order derivative of FT-IR–ATR spectra, for compositional analyses of CS–HAp, were used. The SEM, MM, and AFM data have shown the formation of CS–HAp composite layers. The surface of CS–HAp composite layers showed uniform growth (at an Ar gas working pressure of p = 2 × 10−3 mbar). The surface of the CS–HAp composites coatings became more nanostructured, becoming granular as the gas pressure increased from 5 × 10−3 to 1.2 × 10−2 mbar. However, our studies revealed that the surface morphology of the CS–HAp composite layers varies with the Ar gas working pressure. At the same time, optical properties are slightly influenced by Ar pressure. Their unique physicochemical properties make them suitable for various applications in the biomedical field, if we consider the already proven antimicrobial properties of chitosan. The antifungal properties and the capacity of the CS–HAp composite layers to inhibit the development of fungal biofilms were also demonstrated using the Candida albicans ATCC 10231 (C. albicans) fungal strain.

Functionalized Porous Hydroxyapatite Scaffolds for Tissue Engineering Applications: A Focused Review

Biomaterials have been widely used in tissue engineering applications at an increasing rate in recent years. The increased clinical demand for safe scaffolds, as well as the diversity and availability of biomaterials, has sparked rapid interest in fabricating diverse scaffolds to make significant progress in tissue engineering. Hydroxyapatite (HAP) has drawn substantial attention in recent years owing to its excellent physical, chemical, and biological properties and facile adaptable surface functionalization with other innumerable essential materials. This focused review spotlights a brief introduction on HAP, scope, a historical outline, basic structural features/properties, various synthetic strategies, and their scientific applications concentrating on functionalized HAP in the diverse area of tissue engineering fields such as bone, skin, periodontal, bone tissue fixation, cartilage, blood vessel, liver, tendon/ligament, and corneal are emphasized. Besides clinical translation aspects, the future challenges and prospects of HAP based biomaterials involved in tissue engineering are also discussed. Furthermore, it is expected that researchers may find this review expedient in gaining an overall understanding of the latest advancement of HAP based biomaterials.

Fabrication and applications of bioactive chitosan-based organic-inorganic hybrid materials: A review

Organic-inorganic hybrid materials like bone, shells, and teeth can be found in nature, which are usually composed of biomacromolecules and nanoscale inorganic ingredients. Synergy of organic-inorganic components in hybrid materials render them outstanding and versatile performance. Chitosan is commonly used organic materials in bionic hybrid materials since its bioactive properties and could be controllable tailored by various means to meet complex conditions in different applications. Among these fabrication means, hybridization was favored for its convenience and efficiency. This review discusses three kinds of chitosan-based hybrid materials: hybridized with hydroxyapatite, calcium carbonate, and clay respectively, which are the representative of phosphate, carbonate, and hydrous aluminosilicates. Here, we reported the latest developments of the preparation methods, composition, structure and applications of these bioactive hybrid materials, especially in the biomedical field. Despite the great progress was made in bioactive organic-inorganic hybrid materials based on chitosan, some challenges and specific directions are still proposed for future development in this review.

Recent Trends in the Development of Bone Regenerative Biomaterials

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. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. 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. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

Constructing a biomimetic nanocomposite with the in situ deposition of spherical hydroxyapatite nanoparticles to induce bone regeneration

Inspired by the nanostructure of bone, biomimetic nanocomposites comprising natural polymers and inorganic nanoparticles have gained much attention for bone regenerative applications. However, the mechanical and biological performances of nanocomposites are largely limited by the inhomogeneous distribution, uncontrolled size and irregular morphology of inorganic nanoparticles at present. In this work, an innovative in situ precipitation method has been developed to construct a biomimetic nanocomposite which consists of spherical hydroxyapatite (HA) nanoparticles and gelatin (Gel). The homogeneous dispersion of HA nanoparticles in nHA-Gel endowed it with a low swelling ratio, enhanced mechanical properties and slow degradation. Moreover, strontium (Sr) was incorporated into HA nanoparticles to further enhance the bioactivity of nanocomposites. In vitro experiments suggested that nHA-Gel and Sr-nHA-Gel facilitated cell spreading and promoted osteogenic differentiation of bone-marrow-derived mesenchymal stem cells (BMSCs) as compared to pure Gel and mHA-Gel conventional composites developed by mechanical mixing. In vivo rat critical-sized calvarial defect repair further confirmed that nHA-Gel and Sr-nHA-Gel possessed relatively effective bone regenerative abilities among the four groups. Collectively, the biomimetic nanocomposites of nHA-Gel and Sr-nHA-Gel have good efficacy in inducing bone regeneration and would be a promising alternative to bone grafts for clinical applications.

Hyaluronic acid oligosaccharides modified mineralized collagen and chitosan with enhanced osteoinductive properties for bone tissue engineering

In this study, we prepared a biomimetic hyaluronic acid oligosaccharides (oHAs)-based composite scaffold to develop a bone tissue-engineered scaffold for stimulating osteogenesis and endothelialization. The functional oHAs products were firstly synthesized, namely collagen/hyaluronic acid oligosaccharides/hydroxyapatite (Col/oHAs/HAP), chitosan/hyaluronic acid oligosaccharides (CTS/oHAs), and then uniformly distributed in poly (lactic-co-glycolic acid) (PLGA) solution followed by freeze-drying to obtain three-dimensional interconnected scaffolds as temporary templates for bone regeneration. The morphology, physicochemical properties, compressive strength, and degradation behavior of the fabricated scaffolds, as well as in vitro cell responses seeded on these scaffolds and in vivo biocompatibility, were investigated to evaluate the potential for bone tissue engineering. The results indicated that the oHAs-based scaffolds can promote the attachment of endothelial cells, facilitate the osteogenic differentiation of MC3T3-E1 and BMSCs, and have ideal biocompatibility and tissue regenerative capacity, suggesting their potential to serve as alternative candidates for bone tissue engineering applications.

Recent Advances of Chitosan-Based Injectable Hydrogels for Bone and Dental Tissue Regeneration

Traditional strategies of bone repair include autografts, allografts and surgical reconstructions, but they may bring about potential hazard of donor site morbidity, rejection, risk of disease transmission and repetitive surgery. Bone tissue engineering (BTE) is a multidisciplinary field that offers promising substitutes in biopharmaceutical applications, and chitosan (CS)-based bone reconstructions can be a potential candidate in regenerative tissue fields owing to its low immunogenicity, biodegradability, bioresorbable features, low-cost and economic nature. Formulations of CS-based injectable hydrogels with thermo/pH-response are advantageous in terms of their high-water imbibing capability, minimal invasiveness, porous networks, and ability to mold perfectly into an irregular defect. Additionally, CS combined with other naturally-derived or synthetic polymers and bioactive agents has proven to be an effective alternative to autologous bone and dental grafts. In this review, we will highlight the current progress in the development of preparation methods, physicochemical properties and applications of CS-based injectable hydrogels and their perspectives in bone and dental regeneration. We believe this review is intended as starting point and inspiration for future research effort to develop the next generation of tissue-engineering scaffold materials.

Chemistry, Structures, and Advanced Applications of Nanocomposites from Biorenewable Resources

Researchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources.

A highly interweaved HA-SS-nHAp/collagen hybrid fibering hydrogel enhances osteoinductivity and mineralization

The combination of bioactive hydroxyapatite (HAp) with biomimetic bone matrix biomaterials as bone filling scaffolds is a promising strategy for bone regeneration, but the undesirable dispersion of HAp and its interfacial interaction result in inefficient mineralization, mechanical instability, incomplete osteointegration, and even repair failure. Herein, the size dispersion and stabilization of nano-hydroxyapatite (nHAp) in aqueous media were obviously improved by hydrophilic solubilisation and strong negatively charged thiolated hyaluronic acid (HA-SH). Furthermore, the highly interweaved HA-SS-nHAp/collagen hybrid fibering hydrogel exhibited significantly improved mechanical properties and structural stability due to its thickened and densified interweaved fiber network, which ensured the homogeneous dispersion of nHAp in the matrix materials and its integration with the hydrogel network structure completely by covalent self-crosslinking among the sulfhydryl groups derived from the free HA-SH polymer and the mercapto functional groups on the surface of nHAp. Compared with the physically combined micro-hydroxyapatite (μHAp) (d≤25 μm) and nHAp (∼530 nm) with injectable bionic HA-SH and collagen type I biopolymers, HA-SS-nHAp/collagen achieved the maximum efficiency in facilitating rabbit bone marrow stromal cell (rBMSC) adhesion, proliferation and osteogenic differentiation in vitro. The in vivo murine dorsal subcutaneous implantation results further confirmed that the interweaved fiber network structure in HA-SS-nHAp/collagen significantly promoted osteoinductivity and mineralization. This work provides novel insights for the development of new low invasive bone filling biomaterials.

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.

Preparation and properties of a highly dispersed nano-hydroxyapatite colloid used as a reinforcing filler for chitosan

Hydroxyapatite/chitosan (HAp/CS) composites have been widely studied and applied in tissue engineering fields due to their excellent biocompatibility and degradability. However, to improve the mechanical properties of CS, cross-linking agents are commonly added, which will seriously affect its biocompatibility and safety. In this study, the homogenously dispersed nano-hydroxyapatite (nHAp) colloidal solution was first synthesized using a co-precipitation method. The three-dimensional porous nano-hydroxyapatite/chitosan (nHAp/CS) composite scaffolds with different nHAp contents were then obtained through an environmentally friendly freeze-drying process without any cross-linking. The microstructure, porosity, phase composition, swelling ratio, mechanical properties, and biocompatibility of the nHAp/CS scaffolds were thoroughly investigated. The as-prepared nHAp/CS scaffolds exhibited a high porosity and excellent swelling performance. Compared with pure CS scaffolds, the nHAp/CS composite scaffolds not only showed higher compressive modulus but also exhibited better biocompatibility. This study provides a simple and environmentally friendly technique to construct three-dimensional porous nHAp/CS composite scaffolds, which demonstrate promising potential by being a scaffold material for bone tissue engineering.

Theory meets experiment for elucidating the structure and stability of non-covalent complexes: water–amine interaction as a proof of concept

A joint experimental-theoretical spectroscopic investigation has focused on a better understanding of the nature of weak, non-covalent interactions in amine-water model systems.

Injectable and thermosensitive nanofibrous hydrogel for bone tissue engineering

The use of injectable hydrogels is currently restricted by the challenge of achieving fast gelation, good mechanical strength, and cytocompatibility. Polymeric self-assembly is a potent tool for generating functional materials that combine multiple characteristics and can react to external factors. In this study, we have developed fiber-reinforced composite hydrogels that exhibits significantly enhanced mechanical strength, reduced gelling time, and excellent cytocompatibility. The practicability of developing a chitosan-based thermogelling solution using hydroxyapatite and polyelectrolyte complex (PEC) self-assembled fibers were evaluated. The effect of βGP concentration on gelation time was studied by varying the concentration of βGP added to the chitosan solution. Various combinations were tested to create a suitable hydrogel environment for cell encapsulation, growth, and proliferation at physiological pH and temperature. Determination of Young modulus revealed that PEC fibers reinforced hydrogel was three times stiffer than chitosan-βGP gels. The gelation time was reduced to 3 min, and the hydrogels had porous structures and gels at physiological pH, temperature, and showed >80% viability for MTT assay to MG63 cells. Moreover, confocal imaging of PEC fiber reinforced hydrogels showed noticeable viability and proliferation. The molecular interactions between gelling agents, polyelectrolytes, and hydroxyapatite were studied using FTIR. We investigated interfacial bonding between PEC fibers with βGP, NaHCO_3, and HAp. The combination of hydroxyapatite and polymer self-assembly technique improved the efficiency of injectable hydrogels that are helpful in minimally invasive applications.

Osteoblast studied on gelatin based biomaterials in rabbit Bone Bioengineering

The bone-derived-osteoblast seeded biomaterials scaffold in tissue engineering, have displayed prominence in the treatment of the osseous medical condition. In vitro osteogenesis of rabbit osteoblast cell (rOb) from bone tissue (rT) and MSC-derived rOb from bone marrow (rM) on Gelatin-Hydroxyapatite (HG) based biomaterials was investigated. In this work, lyophilized biomaterial was prepared by the addition of amorphous chitosan ('C') to 'H' dispersed in 'G' matrix, to find its role in biomaterials biocompatibility. Isolated rOb seeded biomaterials were studied using CLSM and flow cytometry for proliferation potential. The biomaterial's core and surface morphology was studied from SEM-EDX and AFM respectively. Upon co-culture with HCG, rT over rM showed rabbit bone extracellular matrix (ECM) mimicking properties both in in vitro studies and biomaterials micro architecture. The in vitro metabolic behaviour was studied by Alamar Blue (AB) assay, DNA content using Hoechst 33258, potency via the activity of Alkaline Phosphatase (ALP), Calcium's relative content by Alizarin Red S (ARS) assay. A novel combination of biomaterials-cell interaction was observed when rT was co-cultured with HCG and proved effective in osteogenesis with regard to Bone Bioengineering.

Presentation of Antibacterial and Therapeutic Anti-inflammatory Potentials to Hydroxyapatite via Biomimetic With Azadirachta indica: An in vitro Anti-inflammatory Assessment in Contradiction of LPS-Induced Stress in RAW 264.7 Cells

In the present study, for the first time, biomimetization of hydroxyapatite (HA) with Azadirachta indica (AI) was proposed and established its antioxidant, antibacterial, and anti-inflammatory potential on lipopolysaccharide (LPS). The ethanolic extract of AI was found rich with phenolics and flavonoids, and determined their concentration as 8.98 ± 1.41 mg gallic acid equivalents/g and 5.46 ± 0.84 mg catechin equivalents/g, respectively. The HA was prepared by sol-gel method from calcium nitrate tetrahydrate and orthophosphoric acid, and successfully biomimetization was performed with ethanolic extract of AI. The FTIR analysis settled that as-synthesized HA-AI composite was comprised of both HA and AI. The XRD pattern and Zeta potential revealed that the HA-AI composite was crystalline and negative in charge (-24.0 mV). The average-size distribution, shape, and size of the HA-AI composite was determined as 238.90 d.nm, spherical, and 117.90 nm from size distribution, SEM, and HR-TEM analysis, respectively. The SEM-EDX concluded that the HA-AI composite was comprised of elements of HA as well as AI. The HA-AI composite presented potential antioxidant activity and its EC50 values (dose required to inhibit about half of the radicals) for ABTS and DPPH assays were determined as 115.72 ± 2.33 and 128.51 ± 1.04 μg/ml, respectively. The HA-AI composite showed potent antibacterial activity, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) towards S. aureus (ATCC 700699) and E. coli (ATCC 10536) were correspondingly determined as 266.7 ± 28.87 and 600.0 ± 50.0 μg/ml, and 400.0 ± 86.6 and 816.7 ± 76.38 μg/ml. Most importantly, HA-AI composite presented the potential anti-inflammatory response toward lipopolysaccharide (LPS) in RAW 264.7 cells. The dose of 250 μg/ml of HA-AI composite has shown optimum protection against LPS-induced stress (1 μg/ml) by scavenging oxidants and regulating mitochondrial membrane potential (MMP), inflammatory and apoptotic factors. Thus, this study concluded that the impartation of potential biofunctional features to HA from plant sources through biomimetic approach is much beneficial and could find potential application in dentistry and orthopedic.

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications.

In vitro studies on gelatin/hydroxyapatite composite modified with osteoblast for bone bioengineering

A promising route towards bone tissue engineering is made by the raw materials of the composite which mimics properties of the extracellular matrix components. Herein, the favourable human origin bone cells were seeded on the scaffold types to investigate the best co-culture system. The same has been achieved after the synthesis and characterization of gelatin/hydroxyapatite composites infused with chitosan for their calcium to phosphate (Ca/P) ratio by SEM-EDX. Also, in vitro biodegradation and bio-mineralization determined after immersing in lysozyme and SBF respectively. Uni-axial Compressive Strength (UCS), porosity, qualitative to quantitative phase development by XRD and FTIR were evaluated. The human bone cell-seeded composite was tested by flow cytometry, CLSM, SEM and DSC. This study statistically signified the human mesenchymal stem cell (hM) derived bone cell as potential raw material for minor to severe bone related tissue regenerative studies.

In vitro and in vivo evaluation of rotary-jet-spun poly(ɛ-caprolactone) with high loading of nano-hydroxyapatite

Herein, poly(ɛ-caprolactone) (PCL) mats with different amounts of nanohydroxyapatite (nHAp) were produced using rotary-jet spinning (RJS) and evaluated in vitro and in vivo. The mean fiber diameters of the PCL, PCL/nHAp (3%), PCL/nHAp (5%), and PCL/nHAp (20%) scaffolds were 1847 ± 1039, 1817 ± 1044, 1294 ± 4274, and 845 ± 248 nm, respectively. Initially, all the scaffolds showed superhydrophobic behavior (contact angle around of 140^oC), but decreased to 80° after 30 min. All the produced scaffolds were bioactive after soaking in simulated body fluid, especially PCL/nHAp (20%). The crystallinity of the PCL scaffolds decreased progressively from 46 to 21% after incorporation of 20% nHAp. In vitro and in vivo cytotoxicity were investigated, as well as the mats' ability to reduce bacteria biofilm formation. In vitro cellular differentiation was evaluated by measuring alkaline phosphatase activity and mineralized nodule formation. Overall, we identified the total ideal amount of nHAp to incorporate in PCL mats, which did not show in vitro or in vivo cytotoxicity and promoted lamellar bone formation independently of the amounts of nHAp. The scaffolds with nHAp showed reduced bacterial proliferation. Alizarin red staining was higher in materials associated with nHAp than in those without nHAp. Overall, this study demonstrates that PCL with nHAp prepared by RJS merits further evaluation for orthopedic applications.

Synthesis and Evaluation of BMMSC-seeded BMP-6/nHAG/GMS Scaffolds for Bone Regeneration

Bioactive scaffolding materials and efficient osteoinductive factors are key factors for bone tissue engineering. The present study aimed to mimic the natural bone repair process using an osteoinductive bone morphogenetic protein (BMP)-6-loaded nano-hydroxyapatite (nHA)/gelatin (Gel)/gelatin microsphere (GMS) scaffold pre-seeded with bone marrow mesenchymal stem cells (BMMSCs). BMP-6-loaded GMSs were prepared by cross-linking and BMP-6/nHAG/GMS scaffolds were fabricated by a combination of blending and freeze-drying techniques. Scanning electron microscopy, confocal laser scanning microscopy, and CCK-8 assays were carried out to determine the biocompatibility of the composite scaffolds in vitro. Alkaline phosphatase (ALP) activity was measured to evaluate the osteoinductivity of the composite scaffolds. For in vivo examination, critical-sized calvarial bone defects in Sprague-Dawley rats were randomly implanted with BMMSC/nHAG/GMS and BMMSC/BMP-6/nHAG/GMS scaffolds, and compared with a control group with untreated empty defects. The BMP-6-loaded scaffolds showed cytocompatibility by favoring BMMSC attachment, proliferation, and osteogenic differentiation. In radiological and histological analyses, the BMMSC-seeded scaffolds, especially the BMMSC-seeded BMP-6/nHAG/GMS scaffolds, significantly accelerated new bone formation. It is concluded that the BMP-6/nHAG/GMS scaffold possesses excellent biocompatibility and good osteogenic induction activity in vitro and in vivo, and could be an ideal bioactive substitute for bone tissue engineering.

Hydroxyapatite from Fish for Bone Tissue Engineering: A Promising Approach

Natural or synthetic hydroxyapatite (HA) has been frequently used as implant materials for orthopaedic and dental applications, showing excellent bioactivity, adequate mechanical rigidity and structure, osteoconductivity and angiogenic properties, no toxicity, and absence of inflammatory or antigenic reactions. HA can be easily synthesized or extracted from natural sources, such as bovine bone. However, the manufacturing costs to obtain HA are high, restricting the therapy. Herein, much effort has been paid for obtaning alternative natural sources for HA. The potential of HA extracted from skeleton of animals has been investigated. The aim of this review is to exploit the potential of HA derived from fish to fulfill biological activities for bone tissue engineering. In particular, HA from fish is easy to be manufactured regarding the majority of protocols that are based on the calcination method. Furthermore, the composition and structure of HA from fish were evaluated; the biomaterial showed good biocompatibility as a result of non-cytotoxicity and handling properties, demonstrating advantages in comparison with synthetic ones. Interestingly, another huge benefit brought by HA from bone fish is its positive effect for environment since this technique considerably reduces waste. Certainly, the process of transforming fish into HA is an environmentally friendly process and stands as a good chance for reducing costs of treatment in bone repair or replacement with little impact into the environment.