Reinforcement of freeze-dried chitosan scaffolds with multiphasic calcium phosphate short fibers

Dual Modification of Porous Ca-P/PLA Composites with APTES and Alendronate Improves Their Mechanical Strength and Cytobiocompatibility towards Human Osteoblasts

Synthetic implants are used to treat large bone defects that are often unable to regenerate, for example those caused by osteoporosis. It is necessary that the materials used to manufacture them are biocompatible and resorbable. Polymer-ceramic composites, such as those based on poly(L-lactide) (PLLA) and calcium phosphate ceramics (Ca-P), are often used for these purposes. In this study, we attempted to investigate an innovative strategy for two-step (dual) modification of composites and their components to improve the compatibility of composite components and the adhesion between PLA and Ca-P whiskers, and to increase the mechanical strength of the composite, as well as improve osteological bioactivity and prevent bone resorption in composites intended for bone regeneration. In the first step, Ca-P whiskers were modified with a saturated fatty acid namely, lauric acid (LA), or a silane coupling agent γ-aminopropyltriethoxysilane (APTES). Then, the composite, characterized by the best mechanical properties, was modified in the second stage of the work with an active chemical compound used in medicine as a first-line drug in osteoporosis-sodium alendronate, belonging to the group of bisphosphonates (BP). As a result of the research covered in this work, the composite modified with APTES and alendronate was found to be a promising candidate for future biomedical engineering applications.

Nanoporous and nano thickness film-forming bioactive composition for biomedical applications

Unmanageable bleeding is one of the significant causes of mortality. Attaining rapid hemostasis ensures subject survivability as a first aid during combats, road accidents, surgeries that reduce mortality. Nanoporous fibers reinforced composite scaffold (NFRCS) developed by a simple hemostatic film-forming composition (HFFC) (as a continuous phase) can trigger and intensify hemostasis. NFRCS developed was based on the dragonfly wing structure's structural design. Dragonfly wing structure consists of cross-veins and longitudinal wing veins inter-connected with wing membrane to maintain the microstructural integrity. The HFFC uniformly surface coats the fibers with nano thickness film and interconnects the randomly distributed cotton gauge (Ct) (dispersed phase), resulting in the formation of a nanoporous structure. Integrating continuous and dispersed phases reduce the product cost by ten times that of marketed products. The modified NFRCS (tampon or wrist band) can be used for various biomedical applications. The in vivo studies conclude that the developed Cp NFRCS triggers and intensifies the coagulation process at the application site. The NFRCS could regulate the microenvironment and act at the cellular level due to its nanoporous structure, which resulted in better wound healing in the excision wound model.

Hydroxyapatite Based Materials for Bone Tissue Engineering: A Brief and Comprehensive Introduction

Hydroxyapatite (HA) is widely used in bone tissue engineering for its bioactivity and biocompatibility, and a growing number of researchers are exploring ways to improve the physical properties and biological functions of hydroxyapatite. Up to now, HA has been used as inorganic building blocks for tissue engineering or as nanofillers to blend with polymers, furthermore, various methods such as ion doping or surface modification have been also reported to prepare functionalized HA. In this review, we try to give a brief and comprehensive introduction about HA-based materials, including ion-doped HA, HA/polymer composites and surface modified HA and their applications in bone tissue engineering. In addition, the prospective of HA is also discussed. This review may be helpful for researchers to get a general understanding about the development of hydroxyapatite based materials.

Paramagnetic Functionalization of Biocompatible Scaffolds for Biomedical Applications: A Perspective

The burst of research papers focused on the tissue engineering and regeneration recorded in the last years is justified by the increased skills in the synthesis of nanostructures able to confer peculiar biological and mechanical features to the matrix where they are dispersed. Inorganic, organic and hybrid nanostructures are proposed in the literature depending on the characteristic that has to be tuned and on the effect that has to be induced. In the field of the inorganic nanoparticles used for decorating the bio-scaffolds, the most recent contributions about the paramagnetic and superparamagnetic nanoparticles use was evaluated in the present contribution. The intrinsic properties of the paramagnetic nanoparticles, the possibility to be triggered by the simple application of an external magnetic field, their biocompatibility and the easiness of the synthetic procedures for obtaining them proposed these nanostructures as ideal candidates for positively enhancing the tissue regeneration. Herein, we divided the discussion into two macro-topics: the use of magnetic nanoparticles in scaffolds used for hard tissue engineering for soft tissue regeneration.

Tissue engineering stent model with long fiber-reinforced thermoplastic technique

This study aims to construct tissue engineering stents by using the long fiber-reinforced thermoplastic (LFT) technique to develop artery stents. The experimental method combines fibers, the LFT technique, and electrospinning technique. First, the biodegradable polyvinyl alcohol yarns are twisted and coated in polycaprolactone/polyethylene glycol blends through the LFT technique. Next, the weft-knitting and heat treatment are used to establish the stent structure, after which poly(ethylene oxide) (PEO) is electrospun to coat the stents. The morphology, mechanical, and biological properties of tissue engineering stents are evaluated. The test results indicated that the use of the LFT technique retains the softness of filaments, which facilitates the subsequent weft-knitting process. The coating of blends and electrospinning of PEO have a positive influence on the tissue engineering stents, as demonstrated by the tensile strength of 59.93 N and compressive strength of 6.10 N. Moreover, the in vitro degradation of stents exhibits a stabilized process. The water contact angle is 20.33°, and the cell survival rate in 24 h is over 80%. The proposed tissue engineering stents are good candidates for artery stent structure.

Bioactive Glasses: A Promising Therapeutic Ion Release Strategy for Enhancing Wound Healing

The morbidity, mortality, and burden of burn victims and patients with severe diabetic wounds are still high, which leads to an extensively growing demand for novel treatments with high clinical efficacy. Biomaterial-based wound treatment approaches have progressed over time from simple cotton wool dressings to advanced skin substitutes containing cells and growth factors; however, no wound care approach is yet completely satisfying. Bioactive glasses are materials with potential in many areas that exhibit unique features in biomedical applications. Today, bioactive glasses are not only amorphous solid structures that can be used as a substitute in hard tissue but also are promising materials for soft tissue regeneration and wound healing applications. Biologically active elements such as Ag, B, Ca, Ce, Co, Cu, Ga, Mg, Se, Sr, and Zn can be incorporated in glass networks; hence, the superiority of these multifunctional materials over current materials results from their ability to release multiple therapeutic ions in the wound environment, which target different stages of the wound healing process. Bioactive glasses and their dissolution products have high potency for inducing angiogenesis and exerting several biological impacts on cell functions, which are involved in wound healing and some other features that are valuable in wound healing applications, namely hemostatic and antibacterial properties. In this review, we focus on skin structure, the dynamic process of wound healing in injured skin, and existing wound care approaches. The basic concepts of bioactive glasses are reviewed to better understand the relationship between glass structure and its properties. We illustrate the active role of bioactive glasses in wound repair and regeneration. Finally, research studies that have used bioactive glasses in wound healing applications are summarized and the future trends in this field are elaborated.

Development of osteogenic chitosan/alginate scaffolds reinforced with silicocarnotite containing apatitic fibers

Porous composite scaffolds of chitosan-alginate (CH-AL) reinforced by biphasic calcium phosphate fibers containing silicon (Si) were prepared using the freeze-drying method. The fibers were synthesized using a homogenous precipitation method with differing reaction times and were characterized by XRD, FTIR, SEM, and ICP-OES. Fibers produced with no Si incorporation using two different reaction times of 4 d and 8 d comprised two phases of hydroxyapatite (∼93-96 wt%) and β-tricalcium phosphate (β-TCP). No new phases were observed by adding 0.8 wt% of Si during 4 d of precipitation. However, the addition of Si to fibers synthesized within 8 d under reflux conditions produced biphasic fibers with 1.9 wt% Si which consisted of a new phase of silicocarnotite (∼94 wt%) associated with the β-TCP phase. The whisker-like fibers were 10-200 µm in length and 0.2-5 µm in width. The physicochemical, mechanical, and biological properties of composite scaffolds fabricated by adding different fiber contents and types were investigated. The scaffolds exhibited favorable microstructures with a high porosity (66-88%) and the interconnected pores varied in size between 40 and 250 µm. Scaffolds containing silicocarnotite showed a significant improvement in their mechanical properties and in vitro bioactivity (using SBF testing and characterization of the apatite layer by ATR-FTIR and SEM/EDS) as well as proliferation, mineralization and adhesion of MG63 cells, when evaluated by MTT assay, alkaline phosphatase, and SEM. Scaffolds reinforced with silicocarnotite fibers also exhibited better mechanical properties and water uptake, compared to ones containing incorporated fibers made of Si. Composite scaffolds reinforced by 50 wt% fibers precipitated after 8 d were superior in terms of their mechanical properties and achieved a compressive strength and modulus of 272 kPa and 4.9 MPa, respectively, which is 400% greater than CH-AL scaffolds. The results indicate that the addition of Si into biphasic fibers, leading to the formation of silicocarnotite, makes silicocarnotite a potential candidate for the bioactive reinforcement of composite scaffolds for bone tissue engineering.

In vitro and in vivo investigation of osteogenic properties of self-contained phosphate-releasing injectable purine-crosslinked chitosan-hydroxyapatite constructs

Bone fracture repair is a multifaceted, coordinated physiological process that requires new bone formation and resorption, eventually returning the fractured bone to its original state. Currently, a variety of different approaches are pursued to accelerate the repair of defective bones, which include the use of 'gold standard' autologous bone grafts. However, such grafts may not be readily available, and procedural complications may result in undesired outcomes. Considering the ease of use and tremendous customization potentials, synthetic materials may become a more suitable alternative of bone grafts. In this study, we examined the osteogenic potential of guanosine 5′-diphosphate-crosslinked chitosan scaffolds with the incorporation of hydroxyapatite, with or without pyrophosphatase activity, both in vitro and in vivo. First, scaffolds embedded with cells were characterized for cell morphology, viability, and attachment. The cell-laden scaffolds were found to significantly enhance proliferation for up to threefold, double alkaline phosphatase activity and osterix expression, and increase calcium phosphate deposits in vitro. Next, chitosan scaffolds were implanted at the fracture site in a mouse model of intramedullary rod-fixed tibial fracture. Our results showed increased callus formation at the fracture site with the scaffold carrying both hydroxyapatite and pyrophosphatase in comparison to the control scaffolds lacking both pyrophosphatase and hydroxyapatite, or pyrophosphatase alone. These results indicate that the pyrophosphatase-hydroxyapatite composite scaffold has a promising capacity to facilitate bone fracture healing.

Manufacture and characteristics of HA-Electrodeposited polylactic acid/polyvinyl alcohol biodegradable braided scaffolds

This study proposes the braided bone scaffolds. First, biologically degradable polylactic acid (PLA) filaments and polyvinyl alcohol (PVA) filaments are plied into composite yarns using a doubling and twisting machine. The composite yarns are tested to determine the optimal mechanical properties and a stabilized morphology. The PLA/PVA composite yarns are then braided into bone scaffolds, during which the optimal braiding process parameters and yarn ratio are determined. Based on the surface observation and tensile strength, a gear ratio of 45:45 provides the tubular braids with an optimal morphology and porosity that meet the biological requirements. When the PLA/PVA ratio is 3:1, the braids exhibit the maximum tensile properties and the most stable space structure. Furthermore, to make the braids a bioactive material with surface active sites, the braids are coated with hydroxyapatite (HA) by electrodeposition. The resulting HA-electrodeposited bone scaffolds are tested by in vitro biological experiments using a scanning electronic microscope (SEM), energy dispersive x-ray analysis(EDAX), X-ray Diffraction(XRD), and Fourier transform infrared spectroscopy(FT-IR), thereby examining their characteristics and microstructure. Results suggest that HA is electrodeposited over the bone scaffolds successfully. The immersion in simulated body fluid (SBF) is proven to contribute a good in vitro bioactivity to bone scaffolds. As a result, bone scaffolds are a good candidate for the application in the cancellous bone repairing field.

Aldehyde-conjugated chitosan-graphene oxide glucodynamers: Ternary cooperative assembly and controlled chemical release

Simultaneous condensation of aromatic aldehydes (Ar_xCHO; x = 1-4) on chitosan biopolymer (CS) affords, after water-evaporation, structurally-conjugated aryl-functionalized CS-Ar_x-f films. Similarly, cooperative assembly of two-dimensional nanometric graphene oxide (GO), aromatic aldehyde and chitosan provides transparent, flexible and crack-free aldehyde-functionalized, ternary-reinforced CS-Ar_x-GO-f nanocomposite films. Homogenous films were obtained using ortho-hydroxybenzaldehyde Ar₁ while the para-hydroxybenzaldehyde Ar₄ was prone to packing inside. Textural and mechanical properties were investigated and expectedly, significant improvement was found for CS-Ar₁-GO-f because of the great dispersion of the aromatic and the presence of the filler. The sensitivity of unsaturated CN imine bond to hydrolysis was explored for triggering controlled release of aromatics from the as-prepared films. All of them were found to induce a time-dependent aromatic release. It has been moreover observed that the release was significantly delayed in CS-Ar_x-GO-f compared to CS-Ar_x-f, a fact attributed to the interplay of the ring with the basal and edges of graphene oxide, through π-π stacking and additional hydrogen bonding interactions. This finding shows that beyond the conventional wisdom using fillers for improving thermal and mechanical properties, the tiny carbon sheets can act as a regulator for aldehyde release, thereby providing a way for more controlled chemical delivery from confined nanocomposites.

Development of chitosan/gelatin hydrogels incorporation of biphasic calcium phosphate nanoparticles for bone tissue engineering

The chitosan/gelatin hydrogel incorporated with biphasic calcium phosphate nanoparticles (BCP-NPs) as scaffold (CGB) for bone tissue engineering was reported in this article. Such nanocomposite hydrogels were fabricated by using cycled freeze-thawing method, of which physicochemical and biological properties were regulated by adjusting the weight ratio of chitosan/gelatin/BCP-NPs. The needle-like BCP-NPs were dispersed into composites uniformly, and physically cross-linked with chitosan and gelatin, which were identified via Scanning Electron Microscope (SEM) images and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The porosity, equilibrium swelling ratio, and compressive strength of CGB scaffolds were mainly influenced by the BCP-NPs concentration. In vitro degradation analysis in simulated body fluids (SBF) displayed that CGB scaffolds were degraded up to at least 30 wt% in one month. Also, CCK-8 analysis confirmed that the prepared scaffolds had a good cytocompatibility through in culturing with bone marrow mesenchymal stem cells (BMSCs). Finally, In vivo animal experiments revealed that new bone tissue was observed inside the scaffolds, and gradually increased with increasing months, when implanted CGB scaffolds into large necrotic lesions of rabbit femoral head. The above results suggested that prepared CGB nanocomposites had the potential to be applied in bone tissue engineering.

Using Chitosan Besides Nano Hydroxyapatite and Fluorohydroxyapatite Boost Dental Pulp Stem Cell Proliferation

The dental tissue scaffold must provide a favorable surface for dental pulp stem cell attachment and proliferation. Employing nanohydroxyapatite (HA) and nanofluorohydroxyapatite (FHA) beside synthetic and organic polymer in favor of scaffolds would be used in bone and dental tissue engineering. In this research, nanoHA and FHA/chitosan scaffolds were synthesized by freeze-drying technique. Surface morphology, chemical composition and hydrophilicity have a great impact on initial cell attachment which will further affect the cell viability and proliferation which evaluated by SEM, XRD and contact angle measurement. Bioactivity of scaffolds was investigated by immersion in simulated body fluid (SBF) and cell proliferation assay. In freeze-drying technique percentage usage of hydroxyapatite could be risen up to 40% and shown better macro-mechanical and physical properties and bioactivity. According to obtained results by adding chitosan, contact angle was decreased by %54 and %37 for polycaprolactone (PCL)/HA and PCL/FHA scaffolds. In addition, addition of chitosan causes significant increase in the cell proliferation for PCL/HA and PCL/FHA up to 81% and 164%, respectively. These results indicate that PCL/FHA/chitosan scaffold represent a big potential for dental tissue engineering.

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

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

Chitosan as a Coupling Agent for Phosphate Glass Fibre/Polycaprolactone Composites

This study shows that chitosan (CS) could be highly useful as a coupling agent in phosphate glass fibre/polycaprolactone (PGF/PCL) composites, as it improved the interfacial shear strength by up to 78%. PGFs of the composition 45P2O5–5B2O3–5Na2O–24CaO–10MgO–11Fe2O3 were dip-coated with CS (with a degree of deacetylation >80%) dissolved in acetic acid solution (2% v/v). Different CS concentrations (3–9 g L−1) and coating processes were investigated. Tensile and fragmentation tests were conducted to obtain the mechanical properties of the single fibres and interfacial properties of the PGF/PCL composites, respectively. It was observed that post-cleaning, the treated fibres had their tensile strength reduced by around 20%; however, the CS-coated fibres experienced strength increases of up to 1.1–11.5%. TGA and SEM analyses were used to confirm the presence of CS on the fibre surface. FTIR, Raman, and X-ray photoelectron spectroscopy (XPS) analyses further confirmed the presence of CS and indicated the protonation of CS amine groups. Moreover, the nitrogen spectrum of XPS demonstrated a minimum threshold of CS coating required to provide an improved interface.

Nanofibers and Microfibers for Osteochondral Tissue Engineering

The use of fibers into scaffolds is a way to mimic natural tissues, in which fibrils are embedded in a matrix. The use of fibers can improve the mechanical properties of the scaffolds and may act as structural support for cell growth. Also, as the morphology of fibrous scaffolds is similar to the natural extracellular matrix, cells cultured on these scaffolds tend to maintain their phenotypic shape. Different materials and techniques can be used to produce micrfibers- and nanofibers for scaffolds manufacturing; cells, in general, adhere and proliferate very well on PCL, chitosan, silk fibroin, and other nanofibers. One of the most important techniques to produce microfibers/nanofibers is electrospinning. Nanofibrous scaffolds are receiving increasing attention in bone tissue engineering, because they are able to offer a favorable microenvironment for cell attachment and growth. Different polymers can be electrospun, i.e., polyester, polyurethane, PLA, PCL, collagen, and silk. Other materials such as bioglass fibers, nanocellulose, and even carbon fiber and fabrics have been used to help increase bioactivity, mechanical properties of the scaffold, and cell proliferation. A compilation of mechanical properties and most common biological tests performed on fibrous scaffolds is included in this chapter.

HIGHLIGHTS

The use of microfibers and nanofibers allows for tailoring the scaffold properties. Electrospinning is one of the most important techniques nowadays to produce fibrous scaffolds. Microfibers and nanofibers use in scaffolds is a promising field to improve the behavior of scaffolds in osteochondral applications.

Effects of Fe2O3 addition and annealing on the mechanical and dissolution properties of MgO-and CaO-containing phosphate glass fibres for bio-applications

This paper investigated the preparation of phosphate glass fibres (PGFs) in the following systems: i) 45P2O5-5B2O3-5Na2O-(29-x)CaO-16MgO-(x)Fe2O3 and ii) 45P2O5-5B2O3-5Na2O-24CaO-(21-x)MgO-(x)Fe2O3 (where x = 5, 8 and 11 mol%) for biomedical applications. Continuous fibres of 23 ± 1 μm diameter were prepared via a meltdraw spinning process. Compositions with higher Fe2O3 content and higher MgO/CaO ratio required higher melting temperature and longer heating time to achieve glass melts for fibre pulling. The effects of Fe2O3 addition and annealing treatment on mechanical properties and degradation behaviours were also investigated. Adding Fe2O3 was found to increase the tensile strength from 523 ± 63 (Ca-Fe5) to 680 ± 75 MPa (Ca-Fe11), improve the tensile modulus from72 ± 4 (Ca-Fe5) to 78 ± 3 GPa (Ca-Fe11) and decrease the degradation rate from 4.0 (Mg-Fe5) to 1.9 × 10−6 kg m−2 s−1 (Mg-Fe11). The annealing process reduced the fibre tensile strength by 46% (Ca-Fe5), increased the modulus by 19.6%(Ca-Fe8) and decreased the degradation rate by 89.5% (Mg-Fe11) in comparison to the corresponding as drawn fibres. Additionally, the annealing process also impeded the formation of precipitate shells and revealed coexistence of the precipitation and the pitting corrosion as fibre degradation behaviours.

Micro and nanotechnologies for bone regeneration: Recent advances and emerging designs

Treatment of critical-size bone defects is a major medical challenge since neither the bone tissue can regenerate nor current regenerative approaches are effective. Emerging progresses in the field of nanotechnology have resulted in the development of new materials, scaffolds and drug delivery strategies to improve or restore the damaged tissues. The current article reviews promising nanomaterials and emerging micro/nano fabrication techniques for targeted delivery of biomolecules for bone tissue regeneration. In addition, recent advances in fabrication of bone graft substitutes with similar properties to normal tissue along with a brief summary of current commercialized bone grafts have been discussed.

Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide

Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil.