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(A) Representation of DVLO theory-forces are simplified to the sum of the attractive Van der Waals and repulsive EDL forces, (B) schematic of the EDL, consisting of an inner (Stern) layer where counter-ions are strongly bound, and an
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Calcium phosphate cements (CPC) have seen clinical success in many dental and orthopaedic applications in recent years. The properties of CPC essential for clinical success are reviewed in this article, which includes properties of the set cement (e.g. bioresorbability, biocompatibility, porosity and mechanical properties) and unset cement (e.g. se...
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... there may be several complex forces influencing the interaction of colloidal particles in aqueous environments [95], generally forces are simplified to the sum of the attractive Van der Waals and the repulsive electrical double layer (EDL), defined in the Derjaguin, Verway, Landau and Overbeek (DVLO) theory [96,97], Fig. 4A. The EDL is formed due to the charge at the particle surface-liquid interface. To maintain neutrality counter ions are attracted to the particle surface [98]. The counter ions form two layers, (i) the stern layer and (ii) diffuse layer Fig. 4B. If the EDL of two particles overlap a repulsive force between the particles ...
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... double layer (EDL), defined in the Derjaguin, Verway, Landau and Overbeek (DVLO) theory [96,97], Fig. 4A. The EDL is formed due to the charge at the particle surface-liquid interface. To maintain neutrality counter ions are attracted to the particle surface [98]. The counter ions form two layers, (i) the stern layer and (ii) diffuse layer Fig. 4B. If the EDL of two particles overlap a repulsive force between the particles ...
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... an increasing distance away from the particle surface, the potential decreases linearly through the stern layer and exponentially through the diffuse layer reaching zero at the bulk solution [99], Fig. 4B. A common laboratory measurement to estimate the magnitude of the surface potential is the zeta potential, ζP. The ζP is the potential at the slipping or shear plane, where counter ions within this boundary move with the particle, Fig. 4B. The greater the ζP the more stable the suspension, and with regards CPC pastes it has been ...
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... through the stern layer and exponentially through the diffuse layer reaching zero at the bulk solution [99], Fig. 4B. A common laboratory measurement to estimate the magnitude of the surface potential is the zeta potential, ζP. The ζP is the potential at the slipping or shear plane, where counter ions within this boundary move with the particle, Fig. 4B. The greater the ζP the more stable the suspension, and with regards CPC pastes it has been observed the greater the ζP the greater the injectability ...
Citations
... This layer attracts calcium and phosphate ions from the solution providing nucleation sites for apatite crystal formation. In the case of pure β-TCP, The Ca 2+ and PO 4 3− ions need to be supersaturated in surrounding solution in order for apatite to form, which needs more time to establish an apatite layer on the cement surface 48,49 . Moreover, BG incorporation into β-TCP forms a dense and homogeneous cement microstructure due to the mesoporous BG nanoparticles surrounding the TCP particles in a way that fills in cement matrix, which improves the composite's mechanical properties 3 . ...
... 2aand b, respectively. The spectrum of BG showed main bands at 465 cm −1 and 750 cm −1 attributed to Si-O-Si bending vibration for O-Si-O and bending of orthosilicate SiO4 4− , respectively. Strong and wide band in the range 800-1200 cm −1 was assigned to stretching vibration of silicate units in glass structure40 . ...
... This layer attracts calcium and phosphate ions from the solution providing nucleation sites for apatite crystal formation. In the case of pure β-TCP, The Ca 2+ and PO 4 3− ions need to be supersaturated in surrounding solution in order for apatite to form, which needs more time to establish an apatite layer on the cement surface 48,49 . Moreover, BG incorporation into β-TCP forms a dense and homogeneous cement microstructure due to the mesoporous BG nanoparticles surrounding the TCP particles in a way that fills in cement matrix, which improves the composite's mechanical properties 3 . ...
This work aimed at tailoring of different properties of antibacterial drug delivery Ca-phosphate cements by incorporation of bioactive glass (BG). The cements were prepared from beta-tricalcium phosphate cement (β-TCP) and BG based on 50 SiO2—20 CaO—15 Na2O—7 B2O3—4 P2O5—4 Al2O3 wt% with different percentages of BG [5, 10, 15, and 20% (w/w)]. The composite cements were characterized by XRD, FTIR, and TEM. Moreover, in vitro bioactivity and biodegradation were evaluated in the simulated body fluid (SBF) at 37 °C. In addition, physical properties and mechanical strength were determined. Also, the effect of glass addition on the drug release profile was examined using gentamicin. Finally, the antimicrobial activity was studied against Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumonia bacteria, one unicellular fungal strain (Candida albicans), and one multicellular fungal strain (Mucor racemosus). The results showed that after soaking in SBF, the compression strength values ranged from 14 to 36 MPa, the bulk densities and porosities were within 1.35 to 1.49 g/cm³ and 51.3 to 44.71%, respectively. Furthermore, gentamicin was released in a sustained manner, and BG decreased the released drug amount from ~ 80% (in pure β-TCP) to 47–53% in the composite cements. A drug release profile that is sustained by all samples was achieved. The antimicrobial test showed good activity of gentamicin-conjugated cements against bacteria and fungi used in this study. Additionally, cytotoxicity results proved that all samples were safe on MG-63 cells up to 50 µg/mL with no more than 7–12% dead cells. From the view of the physico-mechanical properties, bioactivity, biodegradation, and drug release rate, 20BG/β-TCP sample was nominated for practical bone grafting material, where it showed appropriate setting time and a relatively high mechanical strength suitable for cancellous bone.
... Common treatments of this problem that were developed empirically in the calcium phosphate literature include reducing particle size (Baroud et al., 2005), specific surface area (Montufar et al., 2013), broadening size distribution (Gouveia et al., 2015), increasing sphericity (Tadier et al., 2014) and surface modification (Wang et al., 2005) of the particles, reducing particle/binder ratio (Burguera et al., 2008), increasing binder viscosity by low temperatures (Yan, 2018), by hydrogel (Kulakoğlu et al., 2022) or plasticizer (Liu et al., 2013) incorporation, optimizing the extruder geometry (Habib et al., 2008), increasing extrusion rate (O'Neill et al., 2016), and vibration during extrusion (Baroud et al., 2003). Generally these strategies were useful to minimize liquid phase migration by strengthening the adhesion between the binder and the particles and/or weakening particle-particle interactions (O'Neill et al., 2017). ...
The major shortcoming of aqueous calcium phosphate suspensions used in biomedical applications is their unstable flow during delivery by mechanical means. In this study, microstructural changes and the resulting flow instabilities of aqueous β-TCP suspensions are demonstrated under both pressure-induced and drag-induced flow regimes and then remedied with the incorporation and subsequent gelling and preshearing of Carbopol 940, a biocompatible hydrogel. Mixing and dispersion of calcium phosphate particles into the hydrogel matrix was not efficient under simple agitation conditions. Swelling of the polymer chains was induced at approximately pH = 9.0 by water and particle intrusion within the opened-up coil structure due to deprotonation of the carboxylic acid groups by NaOH. As a result the composite material underwent a rapid viscoplastic transition into a doughy state which was not amenable to further processing without preshearing. Manual kneading converted the material into viscous state and enhanced the flow behavior significantly. Preshearing and probing the microstructure by mechanical spectrometer revealed multiple microstructural mechanisms responsible for the observed stable flow behavior, including improved dispersion of the particles, attrition of the poly-meric network into microgel domains, enhanced adhesion and lubrication between the solid and liquid phase, crosslinking of the polymeric network. The net effect of these probable mechanisms was stiffening of the composite matrix, mobilization of solid particles and a marked enhancement in the stability of pressure-induced flow. The resistance of the material to liquid phase migration and its ability to undergo wall-slip and relax under stress were confirmed by simultaneous capillary rheometry and thermogravimetric analyses. The processing method enables improvements in the delivery of this composite material for injection and direct ink writing of scaffolds.
... The use of citrus pectin allowed for su cient plasticisation of the paste improving its viscosity. In opposition to CPCs, which are usually non-injectable [40], obtained biomicroconcretes containing citrus pectin (MC2-MC4) were fully injectable and kept cohesion after being extruded into SBF. It was noticed that the force required to inject biomicroconcretes decreased with the increasing amount of citrus pectin. ...
In this work, the influence of the liquid phase composition on the physicochemical properties of double hybrid-type bone substitutes was investigated. The solid phase of obtained biomicroconcretes was composed of highly-reactive α-tricalcium phosphate powder (α-TCP) and hybrid hydroxyapatite/chitosan granules (HA/CTS). Various combinations of disodium phosphate (Na 2 HPO 4 ) solution and citrus pectin gel were used as liquid phases. The novelty of this study is the development of double-hybrid materials with a dual setting system. The double hybrid phenomenon is due to the interactions between polycationic polymer (chitosan in hybrid granules) and polyanionic polymer (citrus pectin). The chemical and phase composition (FTIR, XRD), setting times (Gillmore Needles), injectability, mechanical strength, microstructure (SEM) and chemical stability in vitro were studied. It has been showed that the properties of materials can be controlled by using the appropriate ratio of citrus pectin in the liquid phase.
... Higher solid contents help improving shape fidelity and avoid the buildup of internal mechanical stress during drying of solvent-based inks. The challenge www.nature.com/scientificreports/ is to maintain a printable viscosity and avoid clogging of the nozzle due to phase separation of the ink's liquid and solid components48,49 . ...
Emerging technologies such as smart packaging are shifting the requirements on electronic components, notably regarding service life, which counts in days instead of years. As a result, standard materials are often not adapted due to economic, environmental or manufacturing considerations. For instance, the use of metal conductive tracks in disposable electronics is a waste of valuable resources and their accumulation in landfills is an environmental concern. In this work, we report a conductive ink made of carbon particles dispersed in a solution of shellac. This natural and water-insoluble resin works as a binder, favourably replacing petroleum-derived polymers. The carbon particles provide electrical conductivity and act as a rheology modifier, creating a printable shear-thinning gel. The ink’s conductivity and sheet resistance are 1000 S m−1 and 15 Ω sq−1, respectively, and remain stable towards moisture. We show that the ink is compatible with several industry-relevant patterning methods such as screen-printing and robocasting, and demonstrate a minimum feature size of 200 μm. As a proof-of-concept, a resistor and a capacitor are printed and used as deformation and proximity sensors, respectively.
... Nevertheless, their mechanical properties and handling performance still need to be improved to satisfy clinical requirements. Indeed, enhancing their injectability can widen its application to minimally invasive surgical procedures [2]. This work aims to investigate the effect of the liquid phase amount and presence of hydroxypropyl methyl cellulose (HPMC) on the basic properties of a commercial CPC containing a polymeric adjuvant, chitosan (Chi). ...
Introduction
Calcium phosphate cements (CPCs) have been widely used for bone defect´s filling given their excellent biocompatibility, osteoconduction ability and ease of manipulation [1]. Nevertheless, their mechanical properties and handling performance still need to be improved to satisfy clinical requirements. Indeed, enhancing their injectability can widen its application to minimally invasive surgical procedures [2]. This work aims to investigate the effect of the liquid phase amount and presence of hydroxypropyl methyl cellulose (HPMC) on the basic properties of a commercial CPC containing a polymeric adjuvant, chitosan (Chi).
Materials and methods
Starting from the original formulation containing Chi, samples with different amounts of liquid phase (LP 30%, 38%, 42%, 50%) were prepared. Additionally, for LP 38% and 42% formulations, Chi was replaced by HPMC polymer. Setting times were measured using the Vicat apparatus. After 6 days of setting, mechanical properties were studied through compression assays and Vickers hardness was measured. Injectability experiments were done and the cytotoxicity of the commercial CPC was assessed using MG63 and NIH/3T3 cell lines following the ISO 10993-5 guidelines.
Results
As shown in Table 1, increasing the LP content from 30% to 50% increased the initial setting time from 6.5 min to 24 min, and the final setting time from 7.5 min to 32 min. Concerning the resistance to compression, it was lowered from 9.53 ± 1.00 MPa to 0.83 ± 0.20 MPa. Regarding materials’ hardness, it decreased by 77%. Injectability measurements showed that only 38% and 42%LP formulations could be injected. Nonetheless, while 38%LP formulation presented an injectability of 31 ± 2%, 42%LP formulation showed an injectability of 91 ± 1%. As for the addition of HPMC, for 38%LP formulation an initial setting time of 6.5 min and a final setting time of 10.5 min were measured, and for 42%LP formulation 12 min and 14.5 min, respectively. The mechanical properties presented similar values regardless the added polymer. Moreover, the formulations containing HPMC presented 69 ± 6% injectability for 38%LP and 94 ± 1% for 42%LP. Finally, when in contact with extracts of the commercial CPC for 24 h, the studied cell lines presented viability greater than 75% when compared to unexposed cells. Discussion and conclusions: Our study shows that LP content has a significant impact on the CPC studied properties. Effectively, for 38 and 42%LP the setting times, resistance to compression and hardness of the materials assume suitable values for their use as trabecular bone defect fillers. For the Chi CPC, 42%LP formulation is ∼200% more injectable than the 38%LP one. Even though the replacement of Chi by HPMC does not affect the mechanical properties significantly, HPMC itself seems to promote injectability, increasing it by 126%. Finally, the commercial CPC does not show a cytotoxic effect under the conditions of this assay.
Table 1.Effect of the LP content on the properties of the Chi containing CPC.
... It gives close adjustment to the encompassing bone, to irregularly shaped cavities. It also represents a special favourable position over conventional bioceramics, which are difficult to desktop and structure [2]. The putting response of the cement possibly the most necessary characteristic of DCP underneath the mild of the reality that it now not solely immediately controls cement solidifying time alongside with other setting properties, but additionally determines the nature of the product, and in this way it further controls most of the bodily and natural residences of the solidified bond [3].The chemical system atsomestagein the placing reaction includes dissolution and precipitation steps respectively. ...
... Numerous formulations of brushite cement suffer from phase separation upon injection, bringing about restricted injectability. Issues such as increasing the extrusion velocity and utilizing a little syring with a short canula can be modified to enhance the injectability of cement [2,30]. Aspects like reducing the powder to liquid proportion, increase in the viscosity of mixing liquid, broad processing of the cement powder, decrease in particle-particle interface by utilizing added substances (carboxylic acids) and by ion modification of cement reagent are known to increase the cement injectability [21,31]. ...
Calcium Phosphate Cements (CPC) are often preferred over the other calcium phosphate-based biomaterials in orthopedic surgeries due to its ability to be resorbed under physiological conditions. Current ways in developing orthophosphate cement are targeted on unmoved setting of the cements beneath physiological conditions with adequate mechanical properties. Fast setting and normally have poor injectability due to the liquid-solid phase separation, brushite and monetite cements has limited their clinical use. The presence of bound ions within the cement throughout the setting reaction will influence the setting reaction and thus the setting time and therefore cement. Cement injectability is extremely vital for minimally invasive surgical procedures that need injection of the cement into bone defects however, the key factors for the success of surgical interventions aimed at the implantation of prosthesis or osteoconductive materials is the prevention from postoperative bacterial infections. Incorporation of antimicrobial agents such as antibiotics or other antimicrobial agents in DCP cements can prevent post-surgical infections. This article provides an overview on the chemistry, mechanical, applications properties and biological in the drug delivery.
... Both micro-and macropores are important with regard to the biological activity of a CPC, yet both types reduce the mechanical strength of the material [105] . Therefore, one main strategy to increase the strength of a CPC is a reduction of the porosity, leading to a more dense cement matrix [12] . This is most commonly obtained via an increase of the PLR [ 34 , 51 ], a smaller particle size of the starting materials [108] , or by adding liquefiers, including glycolic acid [48] , citric acid [117] and sodium citrate [ 118 , 119 ]. ...
Calcium phosphate cements (CPCs) have been used to treat bone defects and support bone regeneration because of their good biocompatibility and osteointegrative behavior. Since their introduction in the 1980s, remarkable clinical success has been achieved with these biomaterials, because they offer the unique feature of being moldable and even injectable into implant sites, where they harden through a low-temperature setting reaction. However, despite decades of research efforts, two major limitations concerning their biological and mechanical performance hamper a broader clinical use. Firstly, achieving a degradation rate that is well adjusted to the dynamics of bone formation remains a challenging issue. While apatite-forming CPCs frequently remain for years at the implant site without major signs of degradation, brushite-forming CPCs are considered to degrade to a greater extent. However, the latter tend to convert into lower soluble phases under physiological conditions, which makes their degradation behavior rather unpredictable. Secondly, CPCs exhibit insufficient mechanical properties for load bearing applications because of their inherent brittleness. This review places an emphasis on these limitations and provides an overview of studies that have investigated the biological and biomechanical performance as well as the degradation characteristics of different CPCs after implantation into trabecular bone. We reviewed studies performed in large animals, because they mimic human bone physiology more closely in terms of bone metabolism and mechanical loading conditions compared with small laboratory animals. We compared the results of these studies with clinical trials that have dealt with the degradation behavior of CPCs after vertebroplasty and kyphoplasty.
... Esto significa que se podría sacrificar una correcta densificación, ya que a medida que se aumenta la cantidad de líquido es posible que las piezas finales tengan más porosidad, pero esto es algo que los investigadores y fabricantes buscan controlar, ya que si no tiene mucha fase líquida en la suspensión, el desmolde se puede tornar complicado [4]. En diversos estudios, se ha visto que se ve favorecido el proceso cuando se usan suspensiones con un comportamiento tixotrópico, ya que se favorece el flujo de la suspensión al interior del molde [2], [5][6][7], para esto se debe estudiar la cantidad adecuada de defloculante a usar y la interacciones que pueda tener la suspensión, lo que normalmente es evaluado mediante el potencial Z [8,9]. Por esto se han propuesto usar suspensiones con un porcentaje de sólidos en peso entre 60% y un 80%, con diferentes concentraciones de defloculante para así poder determinar el porcentaje óptimo para elaborar los crisoles [8]. ...
The crucibles were made using the casting technique, by using suspensions manufactured with alumina powders, which were characterized by scanning electron microscopy (SEM) and allowed to determine that a granulometric distribution d10 and d90 of 0.85 and 1.96 µm respectively, and that presented an irregular morphology. The chemical composition evaluated by X-ray Hernández R., J. F.; Corrales A., M. C.; López G., M. E. Revista Colombiana de Materiales, No 15, pp. 34-42, 2020. 35 fluorescence (XRF) was 99.81% (% by weight) of alumina Also it was found that the predominant crystalline phase is α-alumina and the remaining mostly corresponds to aluminum hydroxide as determined by by X-ray diffraction (XRD). The suspensions were elaborated using a design of experiments 3 2 , whose factors were the percentages of solids and deflocculant (mixture of polyacrylates, PA), from which the levels in which the suspension did not present adequate characteristics for the casting process were discarded. Subsequently, these samples were studied rheologically to see their thixotropy and/or reopexy coefficient, and thus associate it with their behavior in the casting to the gypsum mold. The suspensions with the best performance were analyzed to determine the storage and loss modules, thus verifying their stability. The crucibles were sintered at 1600°C for 3 h; the surface porosity and the internal porosity were measured to determine if they had a good sintering. The results indicate that the suspension with 80% solids and 0.1 of the polyacrylate mixture presented a higher thixotropy coefficient and a low porosity in the crucible cross section.
... By quantifying the force required for injection and correlating it to the ease of injection, early decisions about which biomaterial formulations, syringe, and needle sizes to take forward may be made early in the developmental process 8 . Such experiments may also quantify the effects of changing formulations on injectability 9 . ...
... Alternatively, comparing between samples allows for the quantification of changes to formulations on injectability. For example, in cements, changing the viscosity of the liquid phase, the particle size distribution, and adding additives such as citrate to alter the colloidal properties, can have large changes in injectability 9 . These tests may also inform formulation protocol for cements, for example mixing time, time to loading and time to application, for optimum injection and post-injection performance. ...
