Development of monetite/phosphorylated chitosan composite bone cement

Fabrication of bioactive glass/phosphorylated chitosan composite scaffold and its effects on MC3T3-E1 cells

This study aimed to synthesize bioactive glass (BG) and phosphorylated chitosan (PCS), and fabricate a BG/PCS composite scaffold. The physical properties (mechanical strength, swelling degree, and degradation rate) of the BG/PCS scaffold were tested. Thein vitromineralization properties of composite scaffolds in simulated body fluid were investigated. MC3T3-E1 cell responses with the BG/PCS scaffold were investigated using live/dead cell staining, actin staining, alkaline phosphatase (ALP) activity, and Alizarin red staining. Our results showed that the scaffold had an inner porous structure, good swelling properties, and good degradation rate. After immersion in SBF, the scaffolds demonstrated high properties in inducing mineralization. Leaching solutions of the composite scaffolds exhibited good cytocompatibility. MC3T3-E1 cells adhered, spread, and proliferated on the scaffold. The BG/PCS composite scaffold showed osteo-inductive activity by increasing ALP activity and calcium deposition. Our results indicated that the BG/PCS scaffold had potential applications as a bone-defect repair biomaterial.

Magnesium (Mg2 +), Strontium (Sr2 +), and Zinc (Zn2 +) Co-substituted Bone Cements Based on Nano-hydroxyapatite/Monetite for Bone Regeneration

New bone cement type that combines Sr2 + /Mg2 + or Sr2 + /Zn2 + co-substituted nano-hydroxyapatite (n-HAs) with calcium phosphate dibasic and chitosan/gelatin polymers was developed to increase adhesion and cellular response. The cements were physicochemically described and tested in vitro using cell cultures. All cements exhibited quite hydrophilic and had high washout resistance. Cement releases Ca2 + , Mg2 + , Sr2 + , and Zn2 + in concentrations that are suitable for osteoblast proliferation and development. All of the cements stimulated cell proliferation in fibroblasts, endothelial cells, and osteoblasts, were non-cytotoxic, and produced apatite. Cements containing co-substituted n-HAs had excellent cytocompatibility, which improved osteoblast adhesion and cell proliferation. These cements had osteoinductive potential, stimulating extracellular matrix (ECM) mineralization and differentiation of MC3T3-E1 cells by increasing ALP and NO production. The ions Ca2 + , Mg2 + , Zn2 + , and Sr2 + appear to cooperate in promoting osteoblast function. The C3 cement (HA-SrMg5%), which was made up of n-HA co-substituted with 5 mol% Sr and 5 mol% Mg, showed exceptional osteoinductive capacity in terms of bone regeneration, indicating that this new bone cement could be a promising material for bone replacement.

Monetite, an important calcium phosphate compound-Its synthesis, properties and applications in orthopedics

This review recognizes a unique calcium phosphate (CaP) phase known as monetite or dicalcium phosphate anhydrous (DCPA, CaHPO₄), and presents an overview of its properties, processing, and applications in orthopedics. The motivation for the present effort is to highlight the state-of-the-art research and development of monetite and propel the research community to explore more of its potentials in orthopedics. After a brief introduction of monetite, we provide a summary of its various synthesis routes like dehydration, solvent-based, energy-assisted processes and also discuss the formation of different crystal structures with respect to the synthesis conditions. Subsequently, we discuss the material's noteworthy physico-chemical properties including the crystal structure, vibrational spectra, solubility, thermal decomposition, and conversion to other phases. Of note, we focus on the biological (in vitro and in vivo) properties of monetite, given its ever-increasing popularity as a biomaterial for medical implants. Appropriately, we discuss various orthopedic applications of monetite as bone cement, implant coatings, granules for defect fillers, and scaffolds. Many in vitro and in vivo studies confirmed the favorable osteointegration and osteoconduction properties of monetite products, along with a better balance between implant resorption and new bone formation as compared to other CaP phases. The review ends with translational aspects of monetite and presents thoughts about its possible future research directions. Further research may explore but not limited to improvements in mechanical strength of monetite-based scaffolds, using monetite particles as a therapeutic agent delivery, and tissue engineering strategies where monetite serves as the biomaterial. STATEMENT OF SIGNIFICANCE: This is the first review that focusses on the favorable potential of monetite for hard tissue repair and regeneration. The article accurately covers the "Synthesis-Structure-Property-Applications" correlations elaborating on monetite's diverse material properties. Special focus is put on the in vitro and in vivo properties of the material highlighting monetite as an orthopedic material-of-choice. The synthesis techniques are discussed which provide important information about the different fabrication routes for monetite. Most importantly, the review provides comprehensive knowledge about the diverse biomedical applications of monetite as granules, defect--specific scaffolds, bone cements and implant coatings. This review will help to highlight monetite's potential as an effective regenerative medicine and catalyze the continuing translation of this bioceramic from the laboratory to clinics.

Preparation of PBS/PLLA/HAP Composites by the Solution Casting Method: Mechanical Properties and Biocompatibility

The use of biodegradable polymeric scaffolds for tissue regeneration is becoming a common practice in the clinic. Therefore, an inclined trend is developing with regards to improving the mechanical properties of these scaffolds. Here, we aim to improve the mechanical properties of poly (butylene succinate) (PBS)/poly (l-lactic acid) (PLLA) blends by incorporating hydroxyapatite nanoparticles (HAP) in the blends to form composites. PBS/PLLA = 100/0, 95/5, 90/10, 85/15, and 0/100 wt% blends, along-with the loadings of a few mg of HAPs, were prepared using the solution casting method. A scanning electron microscope showed the voids and droplets, indicating the immiscibility of blends. Due to this immiscibility, the tensile strength values of the blends were found to be in between that of pure PBS (42.85 MPa) and pure PLLA (31.39 MPa). HAPs act as a compatibilizer by incorporating themselves in the voids and spaces caused by the immiscibility, thus increasing the overall tensile strength of the resulting composite to a certain extent, e.g., the tensile strength of PBS/PLLA = 95/5 loaded with 50 mg HAPs was found to be 51.16 MPa. The structural analysis employing the X-ray diffraction (XRD) patterns confirmed the formation of polymer blends and composites. The contact angle analysis showed that the addition of HAPs increased the hydrophilicity of the resulting composites. Selective samples were investigated based on mechanical properties to see if the blends and composites are biocompatible. The obtained results showed that all of the samples with better mechanical properties demonstrated good biocompatibility. This indicates the effectiveness of scaffolds for tissue regeneration.

Smart Injectable Self-Setting Monetite Based Bioceramics for Orthopedic Applications

The present study is the first of its kind dealing with the development of a specific bioceramic which qualifies as a potential material in hard-tissue replacements. Specifically, we report the synthesis and evaluation of smart injectable calcium phosphate bone cement (CPC) which we believe will be suitable for various kinds of orthopedic and spinal-fusion applications. The smart nature of this next generation orthopedic implant is attained by incorporating piezoelectric barium titanate (BT) particles into monetite-based (dicalcium phosphate anhydrous, DCPA) CPC composition. The main goal is to take advantage of the piezoelectric properties of BT, as electromechanical effect plays a vital role in fracture healing at the defect site and bone integration with the implant. Furthermore, radiopacity of BT would help in easy detection of the CPC presence at the fracture site during surgery. Results reveal that BT addition favors important properties of bone cement such as good compressive strength, injectability, bioactivity, biocompatibility, and even washout resistance. Most importantly, the self-setting nature of the bone cements are not compromised with BT incorporation. The in vitro results confirm that the developed bone-cement abides by the standard orthopedic requirements making it apt for real-time prosthetic materials.

Development of nanosilica bonded monetite cement from egg shells

This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5±1 min. The compressive strength after 24h of incubation was approximately 8.45±1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10±1 min) process by about 2.5 min and improve compressive strength (20.16±4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics.

Phosphorylation of bio-based compounds: the state of the art

The aim of this review is to present both fundamental and applied research on the phosphorylation of renewable resources, through reactions on naturally occurring functions, and their use in biobased polymer chemistry and applications.

Characterization of the modified chitosan membrane cross-linked with genipin for the cultured corneal epithelial cells

OBJECTIVES

To modify a chitosan membrane (CM) by cross-linking the chitosan with genipin, a naturally occurring cross-linker extracted from Gardenia jasminoides fructus, with the aim of developing a new cell culture support and to observe the phenotypes of cultured human corneal epithelial cells (HCECs) on genipin-cross-linked chitosan membrane (GCM).

METHODS

We tested the cross-linking characteristics and mechanical strength of the GCM. CMs modified by cross-linking with different concentrations of genipin were prepared to investigate the rate of membrane degradation. The biocompatibility of the GCMs was investigated by determining the viability of HCECs cultured on them in vitro. The morphology of the HCECs cultured on CM or GCM was analyzed by confocal microscopy and scanning electron microscopy (SEM). Immunocytochemical staining was conducted to determine the phenotypes of the cultured cells.

RESULTS

The fixation index of the GCM was 31 ± 3% after treatment of CM with 0.5mM genipin. A stress-strain test showed that the GCM could tolerate three times the mechanical force of noncross-linked CM. The biodegradation rate of GCM was much slower than for CM. A 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay showed that cell viability was not affected by cross-linking with 5.0mM genipin. SEM showed that the cultured HCECs adhered to and grew well on the surface of the GCM. Immunocytochemical staining showed keratin 3 (K3) and connexin 43 (Cx-43) immunoreactive HCECs on the GCM and their proliferative ability was not significantly affected by strong immunoreactivity of Ki-67 and p63 markers.

CONCLUSIONS

GCM has potential as a scaffold for corneal epithelium in ocular surface surgery and greater mechanical strength and slower degradation than unmodified CM.