In vitro surface reaction layer formation and dissolution of calcium phosphate cement-bioactive glass composites

Bioactive Glasses Enriched with Strontium or Zinc with Different Degrees of Structural Order as Components of Chitosan-Based Composite Scaffolds for Bone Tissue Engineering

The development of innovative biomaterials with improved integration with bone tissue and stimulating regeneration processes is necessary. Here, we evaluate the usefulness of bioactive glasses from the SiO2-P2O5-CaO system enriched with 2 wt.% SrO or ZnO in the manufacturing of chitosan-based scaffolds. Bioglasses produced using the sol-gel method were subjected to thermal treatment in different regimes. Chitosan/bioglass composites were produced with a weight ratio. Bioglasses were evaluated via TG-DTA, FTIR, and SEM-EDS before and after incubation in simulated body fluid (SBF). The release of ions was tested. The cytocompatibility of the composites in contact with MG63 osteoblast-like cells was evaluated. The results showed that the presence of the crystalline phase decreased from 41.2-44.8% for nonmodified bioglasses to 24.2-24.3% for those modified with ZnO and 22.0-24.2% for those modified with SrO. The samples released Ca2+, Zn2+, and/or Sr2+ ions and were bioactive according to the SBF test. The highest cytocompatibility was observed for the composites containing nonmodified bioglasses, followed by those enriched with SrO bioglasses. The least cytocompatible were the composites containing ZnO bioglasses that released the highest amount of Zn2+ ions (0.58 ± 0.07 mL/g); however, those that released 0.38 ± 0.04 mL/g were characterised by acceptable cytocompatibility. The study confirmed that it is feasible to control the biological performance of chitosan/bioglass composites by adjusting the composition and heat treatment parameters of bioglasses.

Bioactive Glass Modified Calcium Phosphate Cement with Improved Bioactive Properties: A Potential Material for Dental Pulp-Capping Approaches

Direct pulp capping (DPC) is one of the treatment plans for deep caries with mechanical pulp exposure that can replace invasive treatments. This study aimed to assess the apatite-forming ability and solubility of a calcium phosphate cement (CPC) modified with bioactive glass (BG) as a potential bioactive material for DPC.Three different biomaterials including CPC, BG, and CPC/BG composite were used in this study. For bioactivity evaluation, specimens were immersed in simulated body fluid (SBF) for 5 time periods (3, 7, 14, 21 and 28 days). The samples were analyzed by SEM, EDS and XRD to confirm the formation of hydroxyapatite. The solubility was calculated by measuring the initial and final mass according to the ISO 6876 specifications.According to the results of this study, SEM observations and XRD analysis revealed higher formation of hydroxyapatite crystals in the CPC/BG Group and also at the shorter time than those in the CPC and BG groups. Concerning solubility, the CPC group showed the most solubility after 7 days and the BG group showed the lowest one. At this time the difference between CPC and BG groups was statistically meaningful (p value=0.003). After 30 days the CPC/BG group exhibited the lowest solubility value. At the day 30, the CPC and BG groups showed significant difference in their solubility (p value=0.04).).Based on the results, addition of BG to CPC improved bioactivity properties of CPC material and did not affect its solubility adversely. The CPC/BG composite seems to be a promising material for DPC. Further in vivo studies are needed to prove its clinical success.

Angiogenic and osteogenic regeneration in rats via calcium phosphate scaffold and endothelial cell co-culture with human bone marrow mesenchymal stem cells (MSCs), human umbilical cord MSCs, human induced pluripotent stem cell-derived MSCs and human embryonic stem cell-derived MSCs

Angiogenesis is a limiting factor in regenerating large bone defects. The objective of this study was to investigate angiogenic and osteogenic effects of co-culture on calcium phosphate cement (CPC) scaffold using human umbilical vein endothelial cells (hUVECs) and mesenchymal stem cells (MSCs) from different origins for the first time. hUVECs were co-cultured with four types of cell: human umbilical cord MSCs (hUCMSCs), human bone marrow MSCs (hBMSCs) and MSCs from induced pluripotent stem cells (hiPSC-MSCs) and embryonic stem cells (hESC-MSCs). Constructs were implanted in 8 mm cranial defects of rats for 12 weeks. CPC without cells served as control 1. CPC with hBMSCs served as control 2. Microcapillary-like structures were successfully formed on CPC in vitro in all four co-cultured groups. Microcapillary lengths increased with time (p < 0.05). Osteogenic and angiogenic gene expressions were highly elevated and mineralization by co-cultured cells increased with time (p < 0.05). New bone amount and blood vessel density of co-cultured groups were much greater than controls (p < 0.05) in an animal study. hUVECs co-cultured with hUCMSCs, hiPSC-MSCs and hESC-MSCs achieved new bone and vessel density similar to hUVECs co-cultured with hBMSCs (p > 0.1). Therefore, hUCMSCs, hiPSC-MSCs and hESC-MSCs could serve as alternative cell sources to hBMSCs, which require an invasive procedure to harvest. In conclusion, this study showed for the first time that co-cultures of hUVECs with hUCMSCs, hiPSC-MSCs, hESC-MSCs and hBMSCs delivered via CPC scaffold achieved excellent osteogenic and angiogenic capabilities in vivo. The novel co-culture constructs are promising for bone reconstruction with improved angiogenesis for craniofacial/orthopaedic applications. Copyright © 2017 John Wiley & Sons, Ltd.

Properties of CaO-SiO2-P2O5 reinforced calcium phosphate cements and in vitro osteoblast response

Non-cytotoxic and bioactive tetracalcium phosphate/nanomonetite/calcium silicate-phosphate cements were prepared by simple mechanical mixing of starting powder precursors based on acid or basic tetracalcium phosphate/nanomonetite mixtures with 1 or 5 wt% addition of precititated amorphous or crystalline calcium silicate phosphate phases. The small additions (1-2 wt%) of crystalline CaSiP phase caused about a two-fold rise in the compressive strength of cements (up to 70 MPa) with simultaneous preservation of short setting time (around 5 min) and refinement of nanohydroxyapatite particles in microstructure. The results verified a close pH to body fluids and enhanced steady state concentrations of Ca²⁺, silicate and phosphate ions during the soaking of acid than the basic composite mixtures in physiological solution. No cytotoxicity or suppressing in proliferation activity of osteoblasts were revealed after the addition of CaSiP phases to cement powder mixtures. The ALP activity of osteoblasts during the first two days of culture on all composite systems was significantly higher than on pure tetracalcium phosphate/nanomonetite substrates. The superior enhancing in ALP osteoblast activity was found on cements with amorphous CaSiP glass component (even at low contents), which confirms excellent in vitro osteoblast activity on composites and their possible utilization as bone cements in reconstruction medicine.

Injectable Pore-Forming Hydrogel Scaffolds for Complex Wound Tissue Engineering: Designing and Controlling Their Porosity and Mechanical Properties

Traumatic soft tissue wounds present a significant reconstructive challenge. The adoption of closed-circuit negative pressure wound therapy (NPWT) has enabled surgeons to temporize these wounds before reconstruction. Such systems use porous synthetic foam scaffolds as wound fillers at the interface between the negative pressure system and the wound bed. The idea of using a bespoke porous biomaterial that enhances wound healing, as filler for an NPWT system, is attractive as it circumvents concerns regarding reconstructive delay and the need for dressing changes that are features of the current systems. Porous foam biomaterials are mechanically robust and able to synthesize in situ. Hence, they exhibit potential to fulfill the niche for such a functionalized injectable material. Injectable scaffolds are currently in use for minimally invasive surgery, but the design parameters for large-volume expansive foams remain unclear. Potential platforms include hydrogel systems, (particularly superabsorbent, superporous, and nanocomposite systems), polyurethane-based moisture-cured foams, and high internal phase emulsion polymer systems. The aim of this review is to discuss the design parameters for such future biomaterials and review potential candidate materials for further research into this up and coming field.

Antimicrobial activity and resistance selection of different bioglass S53P4 formulations against multidrug resistant strains

AIMS

This study aimed to evaluate the antimicrobial activity of two different formulations of bioglass BAG-S53P4 against multiresistant microorganisms involved in bone infections, and the capability of bioglass to select for resistance.

METHODS

Antibacterial activity was evaluated by means of killing curves. The ability to select for resistant bacteria was evaluated by subculturing microorganisms in serial dilutions of bioglass. Scanning electron microscope acquisitions were conducted to evaluate bioglass-induced morphology changes.

RESULTS

BAG-S53P4 formulations display a high antimicrobial activity and do not seem to select for resistance. Scanning electron microscopy analysis showed cell shrinkage and membrane damage after exposure to bioglass.

CONCLUSIONS

BAG-S53P4 has a significant potential as bone substitute for the treatment of infections caused by multiresistant microorganisms.

Novel bioactive nanocomposite cement formulations with potential properties: incorporation of the nanoparticle form of mesoporous bioactive glass into calcium phosphate cements

Novel calcium phosphate cements incorporated with bioactive glass nanoparticles demonstrate excellent properties for bone injectables.

Self-setting calcium orthophosphate formulations

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes, which set and harden forming either a non-stoichiometric calcium deficient hydroxyapatite or brushite. Since both of them are remarkably biocompartible, bioresorbable and osteoconductive, self-setting calcium orthophosphate formulations appear to be promising bioceramics for bone grafting. Furthermore, such formulations possess excellent molding capabilities, easy manipulation and nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation. In addition, reinforced formulations have been introduced, which might be described as calcium orthophosphate concretes. The discovery of self-setting properties opened up a new era in the medical application of calcium orthophosphates and many commercial trademarks have been introduced as a result. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as pourability and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules and even cells for tissue engineering purposes. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.

A comparative assessment of synthetic ceramic bone substitutes with different composition and microstructure in rabbit femoral condyle model

Various bone substitutes with improved biocompatibility have been developed. Because these products vary in composition and microstructure, it is difficult to understand each feature and make an appropriate selection. Three recently developed highly porous ceramic bone substitutes were evaluated, including two made of hydroxyapatite with different structures (Apaceram-AX: 85%-porosity with micropores, NEOBONE: 75%-porosity without micropores) and one composed of beta-tricalcium phosphate (OSferion: 75%-porosity with micropores) in a rabbit model. Apaceram-AX showed gradual degradation, while NEOBONE remaining intact. OSferion was almost completely degraded at 24 weeks. Numerous osteoclasts were detected in materials with micropores, whether Apaceram-AX or OSferion, but not in NEOBONE. These differences of biodegradability seemed to be related to the presence of micropores. The compressive strength of OSferion increased for several weeks and decreased at a level of cancellous bone. The strength of NEOBONE gradually increased and remained at the highest level among three. The strength of Apaceram-AX increased two to three times that of cancellous bone. Surprisingly, the strength of all materials declined during the initial 1 week, suggesting that great care should be taken in the early period after implantation. These findings may help surgeons to select an appropriate porous substitute based on understanding of their features.

Calcium Orthophosphate Cements and Concretes

In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone), calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.