Initial biocompatibility and enhanced osteoblast response of Si doping in a porous BCP bone graft substitute

Fabrication and biological evaluation of three-dimensional (3D) Mg substituted bi-phasic calcium phosphate porous scaffolds for hard tissue engineering

This work reports on the fabrication of three-dimensional (3D) magnesium substituted bi-phasic calcium phosphate (Mg-BCP) scaffolds by gel-casting, their structural and physico-chemical characterization, and on the assessment of their in vitro and in vivo performances. The crystalline phase assemblage, chemical functional groups and porous morphology features of the scaffolds were evaluated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy (FE-SEM), respectively. The sintered scaffolds revealed an interconnected porosity with pore sizes ranging from 4.3 to 7.28 μm. The scaffolds exhibited good biomineralization activity upon immersion in simulated body fluid (SBF), while an in vitro study using MG-63 cell line cultures confirmed their improved biocompatibility, cell proliferation and bioactivity. Bone grafting of 3D scaffolds was performed in non-load bearing bone defects surgically created in tibia of rabbits, used as animal model. Histological and radiological observations indicated the successful restoration of bone defects. The overall results confirmed the suitability of the scaffolds to be further tested as synthetic bone grafts in bone regeneration surgeries and in bone tissue engineering applications.

Bone Regeneration by Multichannel Cylindrical Granular Bone Substitute for Regeneration of Bone in Cases of Tumor, Fracture, and Arthroplasty

In orthopedics, a number of synthetic bone substitutes are being used for the repair and regeneration of damaged or diseased bone. The nature of the bone substitutes determines the clinical outcome and its application for a range of orthopedic clinical conditions. In this study, we aimed to demonstrate the possible applications of multichannel granular bone substitutes in different types of orthopedic clinical conditions, including bone tumor, fracture, and bone defect with arthroplasty. A clinical investigation on a single patient for every specific type of disease was performed, and patient outcome was evaluated by physical and radiographic observation. Brief physical characterization of the granular bone substitute and in vivo animal model investigation were presented for a comprehensive understanding of the physical characteristics of the granules and of the performance of the bone substitute in a physiological environment, respectively. In all cases, the bone substitute stabilized the bone defect without any complications, and the defect regenerated slowly during the postoperative period. Gradual filling of the defect with the newly regenerated bone was confirmed by radiographic findings, and no adverse effects, such as osteolysis, graft dispersion, and non-union, were observed. Homogeneous bone formation was observed throughout the defect area, showing a three-dimensional bone regeneration. High-strength multichannel granules could be employed as versatile bone substitutes for the treatment of a wide range of orthopedic conditions.

Silicon bioceramic loaded with vancomycin stimulates bone tissue regeneration

Porous ceramics doped with silicon and pure β-TCP were analyzed in terms of internal microstructure, cell behavior, and the percentage of newly formed bone. Additionally the materials were tested to determine which of the two had better properties to load and release vancomycin hydrochloride. Internal pore distribution and porosity were determined through high pressure mercury porosimetry and the specific surface area was measured by the Brunauer Emmet-Teller method. The proliferation and viability of the human osteoblast-like cell line MG-63 was studied to validate both materials. The materials were tested on eight New Zealand rabbits which created defects, 10 mm in diameter, in the calvaria bone. After 8 and 12 weeks a histological and histomorphometric analysis was performed. Si-β-TCP showed a higher porosity and specific surface area. The cytocompatibility test revealed acceptable results in terms of proliferation and viability whereas the percentage of new bone was higher in Si-β-TCP with a two-time study being statistically significant with 12 weeks of healing (p < 0.05).The vancomycin loaded within the ceramic scaffolds were burst released and the material had the ability to inhibit bacterial growth. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2307-2315, 2018.

Incorporation of BMP-2 loaded collagen conjugated BCP granules in calcium phosphate cement based injectable bone substitutes for improved bone regeneration

The objective of the present study was to incorporate surface modified porous multichannel BCP granule into CPC to enhance its in vivo biodegradation and bone tissue growth. The multichannel BCP granule (15wt%) was first coated with collagen subsequent to BMP-2 loading (ccMCG-B). It was then embedded into CPC to form CPC-ccMCG-B system. The newly developed CPC-ccMCG-B system was then examined for SEM, EDX, XRD, setting time, compressive strength, injectability, pH change, BMP-2 release, in vitro as well as in vivo studies and further compared with CPC. Optimized CPC (0.45mL/g) was found based on setting time and compressive strength studies. In vivo studies exhibited improved new bone formation and better degradation of CPC after 2 and 4weeks of implantation as compared to CPC as resulted from effective BMP-2 signaling. Our results suggest that CPC-ccMCG-B system might be used as a promising injectable bone substitutes in clinical applications.

Effect of physicochemical properties of a cement based on silicocarnotite/calcium silicate on in vitro cell adhesion and in vivo cement degradation

A silicon calcium phosphate cement (Si-CPC) was developed to produce a composite of calcium phosphate and calcium silicate. The silicon cements prepared with low silicon (Si) content were composed of crystalline phases of brushite and silicocarnotite. However, the cements prepared with high Si content were mainly composed of amorphous phases of silicocarnotite, hydroxyapatite and calcium silicate. The cement porosity was about 40% with a shift of the average pore diameter to the nanometric range with increasing Si content. Interestingly, this new cement system provides a matrix with a high specific surface area of up to 29 m(2) g(-1). The cytocompatibility of the new Si-doped cements was tested with a human osteoblast-like cell line (MG-63) showing an enhancement of cell proliferation (up to threefold) when compared with unsubstituted material. Cements with a high silica content also improved the cell attachment. The in vivo results indicated that Si-CPCs induce the formation of new bone tissue, and modify cement resorption. We conclude that this cement provides an optimal environment to enhance osteoblast growth and proliferation that could be of interest in bone engineering.

Biocompatibility evaluation of dicalcium phosphate/calcium sulfate/poly (amino acid) composite for orthopedic tissue engineering in vitro and in vivo

In vitro cytocompatibility of ternary biocomposite of dicalcium phosphate (DCP) and calcium sulfate (CS) containing 40 wt% poly (amino acid) (PAA) was evaluated using L929 fibroblasts and MG-63 osteoblast-like cells. Thereafter, the biocompatibility of biocomposite in vivo was investigated using an implantation in muscle and bone model. In vitro L929 and MG-63 cell culture experiments showed that the composite and PAA polymer were noncytotoxic and allowed cells to adhere and proliferate. The scanning electron microscope (SEM) confirmed that two kinds of cells maintained their phenotype on all of samples surfaces. Moreover, the DCP/CS/PAA composite showed higher cellular viability than that of PAA; meanwhile, the cell proliferation and ALP activity were much higher when DCP/CS had added into PAA. After implanted in muscle of rabbits for 12 weeks, the histological evaluation indicated that the composite exhibited excellent biocompatibility and no inflammatory responses were found. When implanted into bone defects of femoral condyle of rabbits, the composite was combined directly with the host bone tissue without fibrous capsule tissue, which shown good biocompatibility and osteoconductivity. Thus, this novel composite may have potential application in the clinical setting.

Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility

Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance and biocompatibility, low elastic modulus and moderate strength. Metastable beta-Ti alloys can be hardened via precipitation of the alpha phase; however, this has an adverse effect on the elastic modulus. Small amounts of Fe (0-2 wt.%) and Si (0-1 wt.%) were added to Ti-35Nb-7Zr-6Ta (TNZT) biocompatible alloy to increase its strength in beta solution treated condition. Fe and Si additions were shown to cause a significant increase in tensile strength and also in the elastic modulus (from 65 GPa to 85 GPa). However, the elastic modulus of TNZT alloy with Fe and Si additions is still much lower than that of widely used Ti-6Al-4V alloy (115 GPa), and thus closer to that of the bone (10-30 GPa). Si decreases the elongation to failure, whereas Fe increases the uniform elongation thanks to increased work hardening. Primary human osteoblasts cultivated for 21 days on TNZT with 0.5Si+2Fe (wt.%) reached a significantly higher cell population density and significantly higher collagen I production than cells cultured on the standard Ti-6Al-4V alloy. In conclusion, the Ti-35Nb-7Zr-6Ta-2Fe-0.5Si alloy proves to be the best combination of elastic modulus, strength and also biological properties, which makes it a viable candidate for use in load-bearing implants.

Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration

In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation.

Hard tissue regeneration using bone substitutes: an update on innovations in materials

Bone is a unique organ composed of mineralized hard tissue, unlike any other body part. The unique manner in which bone can constantly undergo self-remodeling has created interesting clinical approaches to the healing of damaged bone. Healing of large bone defects is achieved using implant materials that gradually integrate with the body after healing is completed. Such strategies require a multidisciplinary approach by material scientists, biological scientists, and clinicians. Development of materials for bone healing and exploration of the interactions thereof with the body are active research areas. In this review, we explore ongoing developments in the creation of materials for regenerating hard tissues.

The effects of dimethyl 3,3'-dithiobispropionimidate di-hydrochloride cross-linking of collagen and gelatin coating on porous spherical biphasic calcium phosphate granules

Collagen- and gelatin-coated porous spherical granule was prepared by slurry dripping process using biphasic calcium phosphate powder. The coating was stabilized by cross-linking with dimethyl 3,3'-dithiobispropionimidate di-hydrogenchloride (DTBP). Afer DTBP cross-linking, the nanostructure of collagen- and gelatin-coated surfaces was changed from smooth to fibrous and net-like structure. Excellent cross-linking of the coating was seen as indicated by the differential scanning calorimetry thermogram and the Fourier transform infrared spectroscopy spectra. After cross-linking the relative intensities of the Fourier transform infrared spectroscopy peaks were decreased and amide bands were shifted to the left. The interaction of gelatin with DTBP cross-linking agent was stronger than that with collagen according to differential scanning calorimetry and Fourier transform infrared spectroscopy results. The compressive strength of the granular bone substitutes increased significantly after the coating process and gelatin coated biphasic calcium phosphate granules showed highest value at 3.68 MPa after cross-linking. Porosity was greater than 63% and did not change significantly with coating. Biocompatibility investigation by in vitro and in vivo showed that the coating improved the cell proliferation marginally. However, the cross-linking process did not jeopardize the excellent biocompatibility of collagen and gelatin. The in vivo study confirms better bone formation behavior of the cross-linked gelatin and collagen coated samples investigated for 8 weeks in vivo.

A novel silicon-based electrochemical treatment to improve osteointegration of titanium implants

BACKGROUND

Titanium and its alloy represent the most commonly used biomaterials worldwide designed for bone-contact under-load applications, which often require specific mechanical properties. In particular, a large number of different biomimetic surface treatments have been developed to speed up the osteointegration process, which facilitates a reduction in recovery time.

PURPOSE

The aim of this work is to investigate the physical-chemical, mechanical and bioactivity properties of an innovative biomimetic treatment on titanium performed using Anodic Spark Deposition (ASD) electrochemical treatment.

METHODS

The proposed ASD treatment was obtained in an electrochemical solution containing silicon, calcium, phosphorous and sodium followed by an alkali etching. Surface morphology was characterized using SEM and laser profilometry. Chemical and structural composition was assessed by EDS, ICP/OES and XRD analysis. Vickers micro hardness and static contact angle measurements were performed to assess the surface mechanical properties and wettability.

RESULTS

The proposed anodization treatment was capable of providing a chemical and morphologic modified titanium oxide layer, adherent and characterized by superhydrophilic properties. The microporous morphology was enriched by calcium, silicon, sodium and phosphorous.After incubation in Kokubo's Simulated Body Fluid (SBF) the treatment showed very high mineralization potential compared to the reference surfaces, accounting for a deposited hydroxyapatite layer as thick as 12 μm after 14 days of SBF incubation.

CONCLUSIONS

On the basis of the results obtained in this study, we believe that the novel silicon-based ASD biomimetic treatment represents a promising treatment capable of enhancing the osteointegration of titanium for dental and orthopedic applications.

A novel antibacterial modification treatment of titanium capable to improve osseointegration

BACKGROUND

Among the different causes of orthopedic and dental implant failure, infection remains the most serious and devastating complication associated with biomaterial devices.

PURPOSE

The aim of this study was to develop an innovative osteointegrative and antibacterial biomimetic coating on titanium and to perform a chemical-physical and in vitro biological characterization of the coating using the SAOS-2 cell line. We also studied the antibacterial properties of the coating against both Gram-positive and Gram-negative bacteria strains.

METHODS

An electrochemical solution containing silicon, calcium, phosphorous, sodium, and silver nanoparticles was used to obtain the antibacterial by Anodic Spark Deposition (ASD) treatment. Surface morphology was characterized using SEM and laser profilometry. A qualitative analysis of the chemical composition of the coating was assessed by EDS. The adhesion properties of the coating to the titanium bulk were performed with a 3-point bending test. SAOS-2 osteoblastic cell line spreading and morphology and viability were investigated. The bacterial adhesion and the antibacterial properties were investigated after 3 h and 24 h of incubation with Streptococcus mutans, Streptococcus epidermidis, and Escherichia coli bacterial strains.

RESULTS

The proposed anodization treatment created a chemically and morphologically modified, adherent titanium oxide layer, characterized by a microporous morphology enriched by calcium, silicon, phosphorous, and silver. The preliminary biological characterization showed optimal SAOS-2 cell adhesion and proliferation as well as a strong antibacterial effect.

CONCLUSIONS

Based on the results of this study, we believe that this novel biomimetic and antibacterial treatment hold promise for enhancing osteointegration while conferring strong antibacterial properties to titanium.