One-step fabrication of apatite-chitosan scaffold as a potential injectable construct for bone tissue engineering

Application of Bioactive Materials for Osteogenic Function in Bone Tissue Engineering

Bone tissue defects present a major challenge in orthopedic surgery. Bone tissue engineering using multiple versatile bioactive materials is a potential strategy for bone-defect repair and regeneration. Due to their unique physicochemical and mechanical properties, biofunctional materials can enhance cellular adhesion, proliferation, and osteogenic differentiation, thereby supporting and stimulating the formation of new bone tissue. 3D bioprinting and physical stimuli-responsive strategies have been employed in various studies on bone regeneration for the fabrication of desired multifunctional biomaterials with integrated bone tissue repair and regeneration properties. In this review, biomaterials applied to bone tissue engineering, emerging 3D bioprinting techniques, and physical stimuli-responsive strategies for the rational manufacturing of novel biomaterials with bone therapeutic and regenerative functions are summarized. Furthermore, the impact of biomaterials on the osteogenic differentiation of stem cells and the potential pathways associated with biomaterial-induced osteogenesis are discussed.

The Diamond Concept Enigma: Recent Trends of Its Implementation in Cross-linked Chitosan-Based Scaffolds for Bone Tissue Engineering

An increasing number of publications over the past ten years have focused on the development of chitosan-based cross-linked scaffolds to regenerate bone tissue. The design of biomaterials for bone tissue engineering applications relies heavily on the ideals set forth by a polytherapy approach called the "Diamond Concept". This methodology takes into consideration the mechanical environment, scaffold properties, osteogenic and angiogenic potential of cells, and benefits of osteoinductive mediator encapsulation. The following review presents a comprehensive summarization of recent trends in chitosan-based cross-linked scaffold development within the scope of the Diamond Concept, particularly for nonload-bearing bone repair. A standardized methodology for material characterization, along with assessment of in vitro and in vivo potential for bone regeneration, is presented based on approaches in the literature, and future directions of the field are discussed.

Chitosomes Loaded with Docetaxel as a Promising Drug Delivery System to Laryngeal Cancer Cells: An In Vitro Cytotoxic Study

Current delivery of chemotherapy, either intra-venous or intra-arterial, remains suboptimal for patients with head and neck tumors. The free form of chemotherapy drugs, such as docetaxel, has non-specific tissue targeting and poor solubility in blood that deters treatment efficacy. Upon reaching the tumors, these drugs can also be easily washed away by the interstitial fluids. Liposomes have been used as nanocarriers to enhance docetaxel bioavailability. However, they are affected by potential interstitial dislodging due to insufficient intratumoral permeability and retention capabilities. Here, we developed and characterized docetaxel-loaded anionic nanoliposomes coated with a layer of mucoadhesive chitosan (chitosomes) for the application of chemotherapy drug delivery. The anionic liposomes were 99.4 ± 1.5 nm in diameter with a zeta potential of -26 ± 2.0 mV. The chitosan coating increased the liposome size to 120 ± 2.2 nm and the surface charge to 24.8 ± 2.6 mV. Chitosome formation was confirmed via FTIR spectroscopy and mucoadhesive analysis with anionic mucin dispersions. Blank liposomes and chitosomes showed no cytotoxic effect on human laryngeal stromal and cancer cells. Chitosomes were also internalized into the cytoplasm of human laryngeal cancer cells, indicating effective nanocarrier delivery. A higher cytotoxicity (p < 0.05) of docetaxel-loaded chitosomes towards human laryngeal cancer cells was observed compared to human stromal cells and control treatments. No hemolytic effect was observed on human red blood cells after a 3 h exposure, proving the proposed intra-arterial administration. Our in vitro results supported the potential of docetaxel-loaded chitosomes for locoregional chemotherapy delivery to laryngeal cancer cells.

A 6-bromoindirubin-3'-oxime incorporated chitosan-based hydrogel scaffold for potential osteogenic differentiation: Investigation of material properties in vitro

Effective treatments for critical size bone defects remain challenging. 6-Bromoindirubin-3'-Oxime (BIO), a glycogen synthase kinase 3β inhibitor, is a promising alternative for treatment of these defects since it aids in promoting osteogenic differentiation. In this study, BIO is incorporated into a new formulation of the guanosine diphosphate cross-linked chitosan scaffold to promote osteogenic differentiation. BIO incorporation was confirmed with ¹³C NMR through a novel concentration dependent peak around 41 ppm. The rapid gelation rate was maintained along with the internal structure's stability. The 10 μM BIO dose supported the control scaffold's microstructure demonstrating a suitable porosity and a low closed pore percentage. While pore sizes of BIO incorporated scaffolds were slightly smaller, pore heterogeneity was maintained. A proof-of-concept study with C2C12 cells suggested a dose-dependent response of BIO on early stages of osteogenic differentiation within the scaffold. These results support future work to examine BIO's role on osteogenic differentiation and biomineralization of encapsulated cells in the scaffold for bone regeneration.

Bone Scaffolds: An Incorporation of Biomaterials, Cells, and Biofactors

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

Encapsulation and differentiation of adipose-derived mesenchymal stem cells in a biomimetic purine cross-linked chitosan sponge

Mesenchymal stem cells derived from adipose tissue have become a widely investigated cell source to use in tissue engineering applications. However, an optimal delivery scaffold for these cells is still needed. A rapidly gelling, injectable chitosan sponge was proposed in this study as a potential candidate for a suitable delivery scaffold. The results demonstrated the ability to encapsulate the stem cells at a 97.6% encapsulation efficiency and that the cells maintain their viability within the sponge. With the potential of using this scaffold for bone tissue engineering, ALP activity assay and fluorescent imaging for osteocalcin proved the ability to differentiate the encapsulated cells into the osteogenic lineage. Furthermore, co-encapsulation of pyrophosphatase within the sponge was investigated as a method to overcome the inhibitory effects that the sponge degradation by-products have on mineralization. Alizarin Red S staining demonstrated the beneficial effects of adding pyrophosphatase, where a significant increase in mineralization levels was achieved.

Synthesis and characterization of an experimental primer containing chitosan nanoparticles - Effect on the inactivation of metalloproteinases, antimicrobial activity and adhesive strength

OBJECTIVE

The aim of this study was to synthesize and characterize an experimental primer containing cationic lipid nanoparticles (NPL-chitosan) and to evaluate its properties.

DESIGN

The NPL-chitosan were synthesized by emulsion and sonication method. The experimental primers were applied in dentin surface of fifty human molars. The experimental groups were: 1) application of commercial primer; 2) Primer containing 2% of Chlorhexidine (CHX) 3); Primer with 2% NPL-chitosan 4); Primer with 0.6 % of NPL-chitosan 5); Primer with 0.4 % of NPL-chitosan. A composite resin plateau was used for the analysis, where sections were made for making the dentin beams. The effect of experimental primer with cationic nanoparticles in the inhibition of matrix metalloproteinase (MMP) activity was carrying out by in situ zymography. For the Resin-Dentin Adhesive Strength and in situ Zymography analysis, was used the One-way analysis of variance (ANOVA) with significance level of 95 %.

RESULTS

Spherical NPL-chitosan presented size below 220 nm, polydispersity index of 0.179 and zeta potential positive and was stable over 75 days. These nanoparticles showed antibacterial activity agsainst S. mutans with MIC of the 0.4 % and MBC of 0.67 %. In the Microtensile Strength, no statistical difference was observed between the experimental groups (p = 0.9054). The in situ zymography assay showed that the group with 2% of NPL-chitosan presented higher inactivation activity of MMPs compared to the other groups (p < 0.05).

CONCLUSION

The experimental primer containing NPL-chitosan has antimicrobial activity, does not alter the adhesive resistance and inactivates MMPs present in dentin.

Chitosan grafted/cross-linked with biodegradable polymers: A review

Public perception of polymers has been drastically changed with the improved plastic management at the end of their life. However, it is widely recognised the need of developing biodegradable polymers, as an alternative to traditional petrochemical polymers. Chitosan (CH), a biodegradable biopolymer with excellent physiological and structural properties, together with its immunostimulatory and antibacterial activity, is a good candidate to replace other polymers, mainly in biomedical applications. However, CH has also several drawbacks, which can be solved by chemical modifications to improve some of its characteristics such as solubility, biological activity, and mechanical properties. Many chemical modifications have been studied in the last decade to improve the properties of CH. This review focussed on a critical analysis of the state of the art of chemical modifications by cross-linking and graft polymerization, between CH or CH derivatives and other biodegradable polymers (polysaccharides or proteins, obtained from microorganisms, synthetized from biomonomers, or from petrochemical products). Both techniques offer the option of including a wide variety of functional groups into the CH chain. Thus, enhanced and new properties can be obtained in accordance with the requirements for different applications, such as the release of drugs, the improvement of antimicrobial properties of fabrics, the removal of dyes, or as scaffolds to develop bone tissues.

A core-shell guanosine diphosphate crosslinked chitosan scaffold as a potential co-encapsulation platform

Recent engineering strategies to better mimic native tissue architecture involve co-encapsulation of cell lineages and/or growth factors in multi-compartmental scaffolds. This study introduces a core-shell platform based on a rapidly gelling guanosine diphosphate cross-linked chitosan scaffold for co-culture. The core-shell sponge is fabricated through combination of chitosan and guanosine diphosphate in 3 steps with each shell layer deposited around the previous layer. Co-encapsulation of pre-osteoblastic MC-3T3 cells and growth factors in the core-shell sponge showed similar microstructure to the standard sponge with high pore connectivity and low closed porosity (<0.4 %). A viable cell population was maintained over time with enhanced cellular functionality when ascorbic acid was added in the same compartment. Co-culture was explored with a proof-of-concept study shown for MC-3T3 and endothelial cells showing homogeneous distribution of cells in their intended compartment. Overall, this core-shell scaffold shows potential as a platform for the regeneration of multiple tissues.

A Review on Chitosan's Uses as Biomaterial: Tissue Engineering, Drug Delivery Systems and Cancer Treatment

Chitosan, derived from chitin, is a biopolymer consisting of arbitrarily distributed β-(1-4)-linked D-glucosamine and N-acetyl-D-glucosamine that exhibits outstanding properties- biocompatibility, biodegradability, non-toxicity, antibacterial activity, the capacity to form films, and chelating of metal ions. Most of these peculiar properties are attributed to the presence of free protonable amino groups along the chitosan backbone, which also gives it solubility in acidic conditions. Moreover, this biopolymer can also be physically modified, thereby presenting a variety of forms to be developed. Consequently, this polysaccharide is used in various fields, such as tissue engineering, drug delivery systems, and cancer treatment. In this sense, this review aims to gather the state-of-the-art concerning this polysaccharide when used as a biomaterial, providing information about its characteristics, chemical modifications, and applications. We present the most relevant and new information about this polysaccharide-based biomaterial's applications in distinct fields and also the ability of chitosan and its various derivatives to selectively permeate through the cancer cell membranes and exhibit anticancer activity, and the possibility of adding several therapeutic metal ions as a strategy to improve the therapeutic potential of this polymer.

Synthesis of Injectable Shear-Thinning Biomaterials of Various Compositions of Gelatin and Synthetic Silicate Nanoplatelet

Injectable shear-thinning biomaterials (iSTBs) have great potential for in situ tissue regeneration through minimally invasive therapeutics. Previously, an iSTB was developed by combining gelatin with synthetic silicate nanoplatelets (SNPs) for potential application to hemostasis and endovascular embolization. Hence, iSTBs are synthesized by varying compositions of gelatin and SNPs to navigate their material, mechanical, rheological, and bioactive properties. All compositions (each component percentage; 1.5-4.5%/total solid ranges; 3-9%) tested are injectable through both 5 Fr general catheter and 2.4 Fr microcatheter by manual pressure. In the results, an increase in gelatin contents causes decrease in swellability, increase in freeze-dried hydrogel scaffold porosity, increase in degradability and injection force during iSTB fabrication. Meanwhile, the amount of SNPs in composite hydrogels is mainly required to decrease degradability and increase shear thinning properties of iSTB. Finally, in vitro and in vivo biocompatibility tests show that the 1.5-4.5% range gelatin-SNP iSTBs are not toxic to the cells and animals. All results demonstrate that the iSTB can be modulated with specific properties for unmet clinical needs. Understanding of mechanical and biological consequences of the changing gelatin-SNP ratios through this study will shed light on the biomedical applications of iSTB on specific diseases.

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.

Synthesis and properties of porous piezoelectric BT/PHBV composite scaffold

The biodegradable material poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffold has good biodegradability, but poor biocompatibility limits its application in the biological field. And it can effectively improve its biological activity by compounding with the bone conduction activity material of Barium titanate (BT). The PHBV and piezoelectric material BT were prepared into porous composite scaffolds with porosity of 45-50%. The mechanical properties and electrical properties of BT/PHBV scaffolds were systematically studied. The results showed that the piezoelectric coefficient d₃₃ was 0.2-1.5 pC/N. Moreover, the compressive strength and elastic modulus were 1.0-2.0 MPa and 100-200 MPa, respectively. The results of degradation and mineralization showed that BT/PHBV scaffolds had good degradation and mineralization performance which was indicated that the materials had good biological activity.

Characterizations and interfacial reinforcement mechanisms of multicomponent biopolymer based scaffold

It is difficult for a single component biopolymer to meet the requirements of scaffold at present. The development of multicomponent biopolymer based scaffold provides an effective method to solve the issue based on the advantages of each kind of the biomaterials. However, the compatibility between different components might be very poor due to the difficulties in forming strong interfacial bonding, and thereby significantly degrading the integrated mechanical properties of the scaffold. In recent years, interface phase introduction, surface modification and in situ growth have been the major strategies for enhancing interfacial bonding. This article presents a comprehensive overview on the research in the area of constructing multicomponent biopolymer based scaffold and reinforcing their interfacial properties, and more importantly, the interfacial bonding mechanisms are systematically summarized. Detailly, interface phase introduction can build a bridge between biopolymer and other components to form strong interface bonding with the two phases under the action of interface phase. Surface modification can graft organic molecules or polymers containing functional groups onto other components to crosslink with biopolymer. In situ growth can directly in situ synthesize other components with the action of nucleating agent serving as an adherent platform for the nucleation and growth of other components to biopolymer surface by chemical bonding. In addition, the mechanical properties (including strength and modulus) and biological properties (including bioactivity, cytocompatibility and biosensing in vitro, and tissue compatibility, bone regeneration capacity in vivo) of multicomponent biopolymer based scaffold after interfacial reinforcing are also reviewed and discussed. Finally, suggestions for further research are given with highlighting the need for specific investigations to assess the interface formation, structure, properties, and more in vivo studies of scaffold before applications.