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Herein, the tribological behavior of 316L stainless steel (SS) fabricated using metal extrusion additive manufacturing (MEAM) is investigated both under dry and simulated body fluid (SBF)‐lubricated conditions. The results and mechanisms are compared with those of 316L SS fabricated via selective laser melting (SLM) and hot rolling (HR). Under dry‐friction conditions, the 316L SS fabricated via MEAM shows inferior tribological performance compared with those fabricated via SLM and HR, primarily because of its lower initial hardness and better plasticity, which increase both abrasive and adhesive wear. Under SBF‐lubricated conditions, the tribological performance of the 316L SS fabricated via MEAM is comparable to that fabricated via HR and superior to that fabricated via SLM. The wear rate of the MEAM‐fabricated 316L SS is 16.8% and 3.2% lower than SLM‐ and HR‐fabricated, respectively. The numerous pores on 316L SS serve as traps for wear particles, which contribute to the reduction of three‐body wear. In terms of wear under SBF‐lubricated conditions, MEAM technology appears to be a promising method for the fabrication of customized 316L orthopedic implants. [ABSTRACT FROM AUTHOR]

AZ80 magnesium alloy was surface treated by micro‐arc oxidation (MAO) and composite of laser shock penning (LSP) and MAO techniques. Untreated and treated specimens were pre‐corroded in simulated body fluids (SBF) with different pH values (pH 4, 7.4, and 9). The ratcheting behavior of all test specimens was experimentally investigated under stress‐controlled loading. The positive or negative value of the ratcheting strain reflects the mechanism of cyclic deformation. The ratcheting strain with negative values is associated with the cyclic deformation being dominated by twinning–detwinning, while the ratcheting strain with positive values is due to dislocation slip playing a dominant role in the cyclic deformation. A higher absolute value of the ratcheting strain means a lower the ratcheting life. Single MAO coating is not conducive to the fatigue life of magnesium alloy in acidic SBF environment, while LSP/MAO composite coating can improve the fatigue life of magnesium alloy under various loading conditions and different pH environment. Highlights: Two modified layers were prepared on the surface of AZ80 magnesium alloys.Modified layers and pH values on effect of ratcheting deformation was investigated.Four deformation mechanisms were used to evaluate the ratcheting behavior. [ABSTRACT FROM AUTHOR]

Aerogels are fascinating solid materials known for their highly porous nanostructure and exceptional physical, chemical, and mechanical properties. They show great promise in various technological and biomedical applications, including tissue engineering, and bone and cartilage substitution. To evaluate the bioactivity of bone substitutes, researchers typically conduct in vitro tests using simulated body fluids and specific cell lines, while in vivo testing involves the study of materials in different animal species. In this context, our primary focus is to investigate the applications of different types of aerogels, considering their specific materials, microstructure, and porosity in the field of bone and cartilage tissue engineering. From clinically approved materials to experimental aerogels, we present a comprehensive list and summary of various aerogel building blocks and their biological activities. Additionally, we explore how the complexity of aerogel scaffolds influences their in vivo performance, ranging from simple single-component or hybrid aerogels to more intricate and organized structures. We also discuss commonly used formulation and drying methods in aerogel chemistry, including molding, freeze casting, supercritical foaming, freeze drying, subcritical, and supercritical drying techniques. These techniques play a crucial role in shaping aerogels for specific applications. Alongside the progress made, we acknowledge the challenges ahead and assess the near and far future of aerogel-based hard tissue engineering materials, as well as their potential connection with emerging healing techniques. [ABSTRACT FROM AUTHOR]

In addition to transmitting and carrying genetic information, RNA plays an important abiotic role in the world of nanomaterials. RNA is a natural polyanionic biomacromolecule, and its ability to promote osteogenesis by binding with other inorganic materials as an osteogenic induction agent was discovered only recently. However, whether it can promote osseointegration on implants has not been reported. Here, we investigated the effect of the RNA-containing coating materials on peri-implant osseointegration. Total RNA extracted from rat muscle tissue was used as an osteogenic induction agent, and hyaluronic acid (HA) was used to maintain its negative charge. In simulated body fluids (SBF), in vitro studies demonstrated that the resulting material encouraged calcium salt deposition. Cytological experiments showed that the RNA-containing coating induced greater cell adhesion and osteogenic differentiation in comparison to the control. The results of animal experiments showed that the RNA-containing coating had osteoinductive and bone conduction activities, which are beneficial for bone formation and osseointegration. Therefore, the RNA-containing coatings are useful for the surface modification of titanium implants to promote osseointegration.

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Quantification of Cd2+ release from Cd-containing quantum dots (QDs) is of fundamental importance to elucidate its toxicity to organisms, but remains a great challenge due to the lack of appropriate analytical method. Herein, a facile method based on size exclusion chromatography (SEC) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for separating and quantifying the QDs and counterpart ions. By using the mixture of sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid tetrasodium salt (EDTA) as the mobile phase, the defect of QD and ion adsorption onto the SEC column was overcome, thus realizing the accurate quantification of ionic species. Besides, the concentration of QDs was achieved through subtracting the ion concentration from the total concentration. Selecting CdSe@ZnS as the typical QDs, the Cd2+ release process in four typical simulated body fluids, namely, simulated gastric fluid, simulated sweat, Gamble's solution, and artificial lysosomal fluid, was monitored using the developed SEC–ICP–MS method. The media pH is identified as the decisive factor which controls the dissolution of ZnS shells and also the Cd2+ release kinetics and final concentration. Our results suggest that the oral pathway for QD uptake poses the biggest risk to human health. [ABSTRACT FROM AUTHOR]

A novel model of biodegradable PHA copolymer films preparation was applied to evaluate the biodegradability of various PHA copolymers and to discuss its biomedical applicability. In this study, we illustrate the potential biomaterial degradation rate affectability by manipulation of monomer composition via controlling the biosynthetic strategies. Within the experimental investigation, we have prepared two different copolymers of 3-hydroxybutyrate and 4-hydroxybutyrate—P(3HB-co-36 mol.% 4HB) and P(3HB-co-66 mol.% 4HB), by cultivating the thermophilic bacterial strain Aneurinibacillus sp. H1 and further investigated its degradability in simulated body fluids (SBFs). Both copolymers revealed faster weight reduction in synthetic gastric juice (SGJ) and artificial colonic fluid (ACF) than simple homopolymer P3HB. In addition, degradation mechanisms differed across tested polymers, according to SEM micrographs. While incubated in SGJ, samples were fragmented due to fast hydrolysis sourcing from substantially low pH, which suggest abiotic degradation as the major degradation mechanism. On the contrary, ACF incubation indicated obvious enzymatic hydrolysis. Further, no cytotoxicity of the waste fluids was observed on CaCO-2 cell line. Based on these results in combination with high production flexibility, we suggest P(3HB-co-4HB) copolymers produced by Aneurinibacillus sp. H1 as being very auspicious polymers for intestinal in vivo treatments. [ABSTRACT FROM AUTHOR]

Spherical-like hydroxyapatite (HA, Ca10(PO4)6(OH)2) particles were prepared by the co-precipitation method in a simulated physiological environment. The effect of calcining temperature, calcining time and the Ca/P ratio of the initial feeding on the morphology and crystallinity of HA were investigated in detail. Interestingly, while the Ca/P ratio of the initial feeding is 1.80, the obtained HA powders calcined at 800 °C for 2 h contain trace amounts of Na and Mg ions, and the (Ca+Na+Mg)/P ratio is equal to 1.66, which is close to the stoichiometric ratio 1.67 of HA. And a better route with shorter reaction time for the synthesis of HA containing trace amounts of Na and Mg elements was acquired.

Silicone rubber (SR) has extensively been used for different industrial and biomedical applications, in view of its good elasticity, chemical inertness, and biocompatibility. However, cure inhibition features, poor mechanical properties, and hydrophobicity, often, limit the possible expansion of its spectrum of applications. The present work has been designed to address these issues by embedding a potential biocompatible filler, nano‐hydroxylapatite (n‐HA), within the SR matrix, through compression molding. The n‐HA particles were initially synthesized by a wet chemical method, and were subsequently introduced into SR quantitatively. The rheological features, compressive properties, simulated body fluid (SBF) uptake, bovine serum albumin (BSA) adsorption, blood compatibility, and cytocompatibility of n‐HA modified SR systems have been investigated. The change in rheological characteristics after n‐HA embedding within SR clearly indicated the favorable interactions between them, and a compatible functional existence under external stresses. The compressive strength, which is critical for the different applications of SR, has been found to be increased with an increase in n‐HA loading. In‐vitro mineralization studies using SBF showed the formation of apatite crystals on the surface of SR/n‐HA system indicating its biocompatibility. This has been confirmed by SEM and FTIR examinations. It has further been observed that the addition of n‐HA particles into SR matrix enhances the protein adsorption characteristics. The n‐HA embedded system exhibited excellent blood compatibility, which has been complemented through hemolysis (%) studies and thrombogenicity assay. The results indicate that the strategy of n‐HA embedding would do significant value addition to SR, and widen its scope in the industrial and biomedical sectors. [ABSTRACT FROM AUTHOR]

Characteristics of phenanthrene and pyrene's sorption and desorption on two local soils in solutions of simulated groundwater, simulated lung fluid, and simulated saliva were studied with batch equilibrium experiments to understand the fate of PAHs in the karst region of southwestern China and to assess the environmental exposure and the health risk of PAHs. The results showed that the sorption and desorption isotherms of phenanthrene and pyrene on two target soils in the three solution systems could be adequately described by the Freundlich model, while the fitted isotherm parameters for the simulated groundwater solution distinguished notably from those for the simulated body fluid solutions. For the sorption experiments, in the simulated groundwater, the n values were 0.722 and 0.672 for phenanthrene and were 0.724 and 0.663 for pyrene, respectively, on the yellow soil and the limestone soil; The log KF values were 3.118 and 3.323 for phenanthrene and were 3.648 and 3.846 for pyrene, respectively, on the yellow soil and the limestone soil. In the simulated body fluids, the n values for phenanthrene and pyrene ranged from 0.622 to 0.836 and from 0.590 to 0.865, respectively, and the log KF values of phenanthrene and pyrene ranged from 2.845 to 3.327 and from 3.344 to 3.779, respectively. For the desorption experiments, in the simulated groundwater, the n values were 0.662 and 0.744 for phenanthrene and were 0.702 and 0.647 for pyrene, respectively, on the yellow soil and the limestone soil. The log KF values were 3.666 and 3.686 for phenanthrene and were 4.128 and 4.225 for pyrene, respectively, on the yellow soil and the limestone soil. In the simulated body fluids, the n values for phenanthrene and pyrene ranged from 0.612 to 0.668 and from 0.631 to 0.819, respectively, and the log KF values of phenanthrene and pyrene ranged from 3.134 to 3.407 and from 3.533 to 3.839, respectively. The limestone soil had relatively higher log KF values but lower KOC values compared to those of the yellow soil, indicated that the nature of sorbent soils played the dominant role in sorption and desorption behaviors of PAHs. The experimental results showed a remarkable differences in sorption and desorption behaviors of PAHs in simulated body fluids and groundwater. The nonlinearities of measured isotherms and the measured sorption capacities of soils in simulated body fluids were significantly lower than corresponding those in the simulated groundwater, and HI values for simulated body fluids systems were significantly smaller than corresponding those for the simulated groundwater systems. The results underscore cautions in assessing environmental exposure and health risks of PAHs based on their sorption–desorption data in simulated groundwater as this is traditionally done. [ABSTRACT FROM AUTHOR]

Bone supports animal bodies, is the place where blood is produced, and is essential for the immune system, among other important functions. The dominant inorganic component in bone is hydroxyapatite (Hap), the structure and dynamics of which still pose many unsolved puzzles. An updated understanding of HAp is of great significance to osteology, dentistry, and the development of artificial bone and other biomaterials. In this work, HAp nanoparticles were synthesized with the wet chemical precipitation method and their structure and morphologies were controlled by varying pH and adding fluoride ions by two different routes: (1) fluoride ions were added during synthesis, and (2) fluoride ions were introduced after the samples were synthesized by soaking the samples in solutions with fluoride ions. XRD and HRTEM were employed to confirm the composition and structure, while various multinuclear (1H, 19F, 31P) solid-state nuclear magnetic resonance (NMR) methods including 1D single pulse, cross-polarization under magic-angle spinning (CPMAS), and 2D heteronuclear correlation (HETCOR) were used to characterize the structure, morphology, and dynamics, validating the general core-shell morphology in these F-HAp samples. It was found that all hydroxide ions were substituted when the fluoride ion concentration was above 0.005 M. An NMR peak corresponding to water structure emerged and the bulk water peak was shifted upfield, indicating that fluoride substitution modifies both the crystalline core and the amorphous shell of F-HAp nanoparticles. With the second route of fluoride substitution, increases in soaking time or fluoride ion concentration could increase fluoride substitution in HAp, but could not achieve complete substitution. Finally, with 1H-31P CPMAS and HETCOR, it was established that there are two types of phosphorous, one in the crystalline core (PO43−) and the other in the amorphous shell (HPO42−). These results are valuable for clarifying the fluoride substitution mechanism in HAp in biomaterials or in organisms, and provide insights for developing next generation replacement materials for bone, tooth, or coating films, drug delivery systems, etc.

The plasma sprayed hydroxyapatite coating (HA) has shown promising prospects in orthopedic implant and dental surgery. The long-term stability of the coating is largely dependent upon the coating integrity, particularly the coating/substrate adhesion and coating crystallinity. However, the short-term clinical performance required that the coating should have loose structure containing some soluble phases, which can promote the osteoblast cells growth and bone fixation after surgery. The first step of this work was to develop a strategy to deposit a graded bi-layer HA coating, in which the bottom layer was dense with high crystallinity and well-adhered to substrate, while the top layer was porous with loose structure. By turning the spraying parameters, especially the melting state of spraying particles and the substrate temperature, the coating with different structural characteristics was prepared on Ti-6Al-4V substrate. Then, the structurally graded HA coating was investigated in vitro for fatigue test. It was shown that spalling was preferentially generated at the loose-structure top layer under cyclic stress. The dense-structure layer with higher bond strength presented improved resistance to crack propagation and therefore the dense layer was favorable to maintain the long-term integrity of coating. • By varying the process parameters, HA coatings with different structural characteristics were prepared by APS. • The coatings' porosity, bond strength and crystallinity was highly dependent upon the particles' melting state. • The fatigue behavior of the optimized bi-layer HA coating was particularly examined in wet condition. [ABSTRACT FROM AUTHOR]

In order to improve the NiTi alloy biocompatibility, surface treatments become very important. Nevertheless, researchers use different solutions to simulate the body fluids in electrochemical assays, and the correlation between the obtained results is difficult and might not even be possible. The present paper evaluated the electrochemical behavior of polished NiTi surfaces exposed to different simulated body fluid solutions: Hanks solution, Hanks’ balanced salt (HBSS) solution, saline body fluid (SBF) solution, and Ringer solution. The electrochemical behavior of NiTi was evaluated by open circuit potential (OCP) and cyclic voltammetry tests. The surfaces of the samples were also characterized by scanning electron microscopy, which was performed after the electrochemical tests. The results demonstrated that the NiTi alloy shows the same corrosion mechanism (pitting) in all simulated body fluids that were studied. However, the corrosion potential changes for each electrolyte, being HBSS, SBF and Ringer the most corrosive solutions. Furthermore, the Hanks and HBSS solutions demonstrated good reproducibility of the electochemical results. Considering that the HBSS represents an extreme environment, this solution seems to be the most indicated to study the corrosion behavior of NiTi treated surfaces.

Abstract This study investigates the use of anodization in NH 4 F/NaCl electrolyte in the formation of self-assembled nanotube arrays on a Ti–7.5Mo surface. As anodic oxidation potential increased from 5 V to 10 V, the pore size and tube length of the nanotubes gradually increased approximately from 23–27 to 31–44 nm, and 550 to 700 nm. The XRD results indicated that the oxide layers on the surface of the anodized samples were all amorphous structures. After annealing at 450 °C for 3 h, peaks of anatase phase were observed. The results of the XPS analysis showed that the major components on the surfaces of the annealed nanotube arrays were TiO 2 , MoO 2 , and MoO 3. In vitro testing of the annealed nanotube arrays demonstrated that rapid deposition of apatite spheroids on these nanostructures occurred after only 12 h immersion in simulated body fluids (SBF), a result that was particularly evident in the samples anodized at 10 V. Cell culture experiments showed that the anodized Ti–7.5Mo alloy is biocompatible and can support cell attachment. Highlights • Nanotubes on Ti–7.5Mo surface were fabricated by anodic oxidation in NaCl/NH 4 F. • A tube length of 550 nm at 5 V and 700 nm at 10 V on Ti–7.5Mo surface. • Components on annealed nanotubes of Ti–7.5Mo surfaces were TiO 2 , MoO 2 , and MoO 3. • After soaking in SBF, Ca P layer covered the entire nanotubular surface within 1 d. [ABSTRACT FROM AUTHOR]

Health risk assessment of trace elements (TrElems) in fine particulate matter (PM 2.5 ) has been studied based on the total element concentrations or more recently on the phosphate buffered saline (PBS)-soluble concentrations. However, behaviors of the TrElems released from PM 2.5 change considerably as the interacting media change. In this study, the bioaccessibility of particulate-bound TrElems (V, Mn, Co, Ni, Cu, As, Cd and Pb) were investigated using three kinds of simulated body fluids, artificial lung fluid (ALF), artificial sweat (AS), and artificial gastric juice (AGJ), comparing with the commonly used PBS. Many TrElems, especially Pb, showed lower solubility in PBS than that in other fluids. Cu, Mn, V and As were observed to be the most soluble TrElems in all simulated body fluids. Carcinogenic and non-carcinogenic effects were evaluated using ALF, AS and AGJ-soluble fractions (representing the corresponding exposure routes: inhalation, dermal contact and ingestion) according to the United States Environmental Protection Agency (USEPA) human health risk assessment model. The carcinogenic risks of As and Pb were higher than 1 × 10 −6 (the acceptable level) for both adults and children. High hazard quotient (HQ) values for As and Pb were also observed for children, indicating a potential non-carcinogenic risk posed by these toxic elements. Our results demonstrated that the health risks of particulate-bound TrElems might be misjudged if using the PBS-soluble or total element contents alone. [ABSTRACT FROM AUTHOR]

Purpose: Most of the studies concerning gellan have been focused on its application as a food ingredient, however, gellan is often considered as a candidate for the development of novel pharmaceutical formulations. Taking into account that gellan is ion-sensitive, it can be assumed that its initial mechanical properties can change upon contact with body secretions. Therefore, the aim of the work was to investigate the rheological properties of pure high-acyl gellan gum hydrogel (0.4%) and its mixtures with selected simulated body fluids. Methods: The rheological investigations were performed on rotational rheometer and included oscillatory temperature, amplitude, and frequency sweeping. The results enabled estimation of the linear viscoelastic regime, calculation of the cross-over points, and percentage of structure recovery. Results: In the case of pure hydrogel no evidence of thermosensitivity was observed in the range of 20-40[sup °]C. In pH = 1.2 (NaCl/HCl) the hydrogel structure was almost entirely destroyed. Mixing with phosphate buffer (pH = 4.5) resulted in higher gel strength than after dilution with deionized water. The opposite effect was observed in the case of pH = 7.4. The studies performed for the mixture of GG hydrogel and mucin indicated interaction between the components. The hydrogel elasticity increased in the presence of simulated tear, but decreased in simulated saliva and vaginal fluid. Conclusions: In this study, it was shown that the stability of a three-dimensional gellan structure may be affected by pH and the presence of mucin which most probably competed with gellan gum in divalent cations binding. The observations presented in this study may be important in terms of potential application of gellan gum as a potential carrier in drug delivery systems. [ABSTRACT FROM AUTHOR]

Rolled Zn-0.8Li-0.2Ag(wt%) alloy as candidates for biodegradable materials. The biodegradable behavior of Zn-0.8Li-0.2Ag alloy in different solutions (Ringer’s, DMEM, SBF and DMEMp) was investigated. The cytotoxicity of Zn-0.8Li-0.2Ag alloy and its antibacterial properties against staphylococcus aureus, enterobacter faecalis and candida albicans were evaluated. The results showed that Zn-0.8Li-0.2Ag alloy consists of zinc matrix and a LiZn _4 secondary phase. The presence of Cl ^− causes locally corroded of Zn-0.8Li-0.2Ag alloy in Ringer’s solution, and its corrosion resistance is lower than that of the alloy which is uniformly corroded in other solutions containing CO _3 ^2− and PO _4 ^3− . Zn-0.8Li-0.2Ag alloy is non-toxic and exhibits better antibacterial properties than the experimental reference group without silver.

The cause of this publication was the problem with the reproducibility of the earlier results conducted with using simulated body fluids. After the exclusion of other factors, the suspicion fall on SBF liquids, which as proved by this publication, in many cases were unstable. Simulated body fluids, such as artificial blood plasma, artificial urine and artificial saliva, are an important testing environment to predict e.g. a potential bone-bonding behavior through the apatite layer formation on its surface; for drug delivery systems examination or osteoinductive material properties. Consequently, it is necessary to ensure constant pH, constant ionic strength and undisturbed access to the calcium (and phosphate) in an artificial body fluids. Therefore, pH value were measured in this work by using pH meters (from two companies) and ion concentrations (Na + and Ca 2 + ) by using inductively coupled plasma – mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS). The result of the work is answer to the question concerning the stability of the tested liquids. All tested simulated body fluids incubated at 36 °C above the week demonstrated changes in pH and ion concentration. The largest change was observed with calcium ions which plays a crucial role in the hydroxyapatite growth during the artificial blood plasma application. Furthermore only in a few cases storage of fluids at 5 °C did not significantly affected their stability. [ABSTRACT FROM AUTHOR]

The electrochemical performance of the Fe–14Cr–8Mn alloy in physiological fluids was investigated in this study. In simulated body solutions, the capacities of the significant biomolecules tyrosine, tryptophan, and l -histidine to inhibit the corrosion of the alloy were also studied. Scanning electron microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy were utilized to investigate the surface morphology and elemental composition of the alloy in various simulated solutions. Potentiodynamic polarization and electrochemical impedance spectroscopy data were used to analyze the electrochemical performance of the alloy. The results showed that the amino acids inhibited the corrosion of Fe–14Cr–8Mn alloy in the simulated body solutions, with maximum inhibitory efficiencies of 55%, 63%, and 70.1% for histidine, tyrosine, and tryptophan, respectively. Quantum chemical computations were also conducted and the findings indicated that even in very aggressive solutions, the alloy had a good passivation capacity. The high stability of the alloy was attributed to the formation of a stable Cr protective film on the alloy surface, which was found to depend on the Cr/Fe oxide ratio. The quantum chemical calculations agreed with the electrochemical results. Tyrosine and l -histidine were effective corrosion inhibitors, but tryptophan protected the solutions better. • The performance of Fe–14Cr–8Mn alloy in physiological fluids was investigated. • Tyrosine, tryptophan, and l -histidine, as biomolecules corrosion inhibitors. • The studied alloy had a good passivation capacity in simulated body solutions. • Quantum chemical calculations were complied with the electrochemical results. • SEM, EDX and XPS methods were used to investigate the surface morphology. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles (IONs) are of great interest in nanomedicine for imaging, drug delivery, or for hyperthermia treatment. Although many research groups have focused on the synthesis and application of IONs in nanomedicine, little is known about the influence of the surface properties on the particles' behavior in the human body. This study analyzes the impact of surface coatings (dextran, polyvinyl alcohol, polylactide-co-glycolide) on the nanoparticles' cytocompatibility, agglomeration, degradation, and the resulting oxidative stress induced by the particle degradation. All particles, including bare IONs (BIONs), are highly cytocompatible (>70%) and show no significant toxicity towards smooth muscle cells. Small-angle X-ray scattering profiles visualize the aggregation behavior of nanoparticles and yield primary particle sizes of around 20 nm for the investigated nanoparticles. A combined experimental setup of dynamic light scattering and phenanthroline assay was used to analyze the long-term agglomeration and degradation profile of IONs in simulated body fluids, allowing fast screening of multiple candidates. All particles degraded in simulated endosomal and lysosomal fluid, confirming the pH-dependent dissolution. The degradation rate decreased with the shrinking size of particles leading to a plateau. The fastest Fe 2+ release could be measured for the polyvinyl-coated IONs. The analytical setup is ideal for a quick preclinical study of IONs, giving often neglected yet crucial information about the behavior and toxicity of nanoparticles in the human body. Moreover, this study allows for the development and evaluation of novel ferroptosis-inducing agents., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

Although stainless steel is a material widely used for biomedical applications, its surface properties for long term application are still a serious concern. 316L stainless steel (SS 316L) is a material commonly used in dentistry for orthodontic braces, wires and in some cases as dental crowns. The pH value of natural saliva from the oral cavity can undergo sudden modification due to food products which are rich in citric acid. The electrochemical corrosion behavior of 316L stainless steel was evaluated in two simulated body fluid solutions, Fusayama-Mayer artificial saliva with pH=5 and Fusayama-Mayer artificial saliva adjusted with citric acid to a pH=1.58 which simulates the environmental conditions of the oral cavity. The surface of SS316L was investigated by optical microscope before and after corrosion assays. The electrochemical corrosion behavior was studied by open circuit potential, potenitodynamic polarization and linear polarization. Optical microscopy was used to characterize the corrosion damage after the electrochemical assays.

We demonstrate, for the first time, that the (Fe 0.75 B 0.15 Si 0.1 ) 100 − x Nb x (x = 0, 1 and 3 at.%) metallic glasses without toxic and allergic elements exhibit excellent apatite-forming ability in simulated body fluids (SBF), which is expected to be a new generation of biomaterials in stents and orthopedic implants. For the alloys without any surface treatment, spherical particles corresponding to octacalcium phosphate are spontaneously nucleated and precipitated throughout the alloy surface after immersion only for 1 day, indicating that the present alloys possess an unusual high bioactivity. During the subsequent in-vitro immersion for 3 days, SEM image reveals the typical ‘cauliflower’ morphology of bone-like hydroxyapatite (HA) with Ca/P ratio of 1.65. In addition, it is surprising to find that the in-vitro SBF immersion not only leads to the formation and growth of the apatite layer but also causes the progressive development of the underlying alloy substrate. Moreover, for the alloys immersed for 3 or 9 days, the substrate alloy just beneath the apatite layer consists of a hierarchical nano/macro-porous structure through selective dissolution of the active components Fe and B in the surface. XPS analysis indicates that the apatite nucleation on the present alloys in SBF is attributed to the specific dissolution properties of the present alloys and the fast formation of Si-OH and Fe–OH or Nb-OH functional groups, followed by combination of these groups with Ca 2 + and phosphate ions. [ABSTRACT FROM AUTHOR]

The metastable and stable equilibria during the precipitation of calcium phosphates in three biomimetic systems, namely SBFc-CaCl-KHPO-HO, SBFc-CaCl-MgCl-KHPO-HO and SBFc-CaCl-ZnCl-KHPO-HO, where SBFc denotes a conventional simulated body fluid, were modeled by a thermodynamic approach (ion-association model, computer program PHREEQCI v.2.14.3). In all cases the highest saturation indices (SI) and the thermodynamic stability were calculated for hydroxyapatite, Ca(PO)OH. Co-precipitation of metastable phases of seven salts in the first system, co-precipitation of additional four magnesium salts in the second system, and no co-precipitation of zinc salts in the third system were calculated at pH 8. Precipitation of amorphous calcium phosphate incorporating Mg, Na, K, $$ {\text{CO}}_{3}^{2 - } $$ and Cl ions at levels close to those of natural enamel, dentin and bone, instead of the thermodynamically stable hydroxyapatite, was experimentally found. This reveals that kinetic factors are decisive for the precipitation processes. In addition, the phase transformations of the precipitated metastable amorphous products (9.94 > SI > 0) during their maturation in the three simulated body fluids, differing in their concentrations of $$ {\text{HCO}}_{3}^{ - } $$ and Cl ions and organic macromolecules, were also modeled. Dissolution of all magnesium salts was found to occur and equilibrium of the more stable calcium salts was established, depending on the $$ {\text{HCO}}_{3}^{ - } $$ concentration. In contrast, transformation of the stable equilibrium products (SI > 0) to the thermodynamically stable hydroxyapatite (SI = 0), independent of the $$ {\text{HCO}}_{3}^{ - } $$ concentration, was both calculated and experimentally proven. Analogous distribution of the species was calculated for the initial and equilibrium solutions of the studied SBFs, while it was different for the metastable solutions. The predominance of free Me ions (Me = Ca, Mg) was calculated in all studied cases. [ABSTRACT FROM AUTHOR]

In vitro degradation behavior of squeeze cast (CAST) and equal channel angular pressed (ECAP) ZM21 magnesium alloy (2.0 wt% Zn-0.98 wt% Mn) was studied using immersion tests up to 4 w in three different biological environments. Hanks' Balanced Salt Solution (Hanks), Earle's Balanced Salt Solution (Earle) and Eagle minimum essential medium supplemented with 10% (v/v) fetal bovine serum (E-MEM + 10% FBS) were used to investigate the effect of carbonate buffer system, organic compounds and material processing on the degradation behavior of the ZM21 alloy samples. Corrosion rate of the samples was evaluated by their Mg 2 + ion release, weight loss and volume loss. In the first 24 h, the corrosion rate sequence of the CAST samples was as following: Hanks > E-MEM + 10% FBS > Earle. However, in longer immersion periods, the corrosion rate sequence was Earle > E-MEM + 10% FBS ≥ Hanks. Strong buffering effect provided by carbonate buffer system helped to maintain the pH avoiding drastic increase of the corrosion rate of ZM21 in the initial stage of immersion. Organic compounds also contributed to maintain the pH of the fluid. Moreover, they adsorbed on the sample surface and formed an additional barrier on the insoluble salt layer, which was effective to retard the corrosion of CAST samples. In case of ECAP, however, this effect was overcome by the occurrence of strong localized corrosion due to the lower pH of the medium. Corrosion of ECAP samples was much greater than that of CAST, especially in Hanks, due to higher sensitivity of ECAP to localized corrosion and the presence of Cl − . The present work demonstrates the importance of using an appropriate solution for a reliable estimation of the degradation rate of Mg-base degradable implants in biological environments, and concludes that the most appropriate solution for this purpose is E-MEM + 10% FBS, which has the closest chemical composition to human blood plasma. [ABSTRACT FROM AUTHOR]

The application of mesoporous silica nanoparticles as a platform for drug delivery and bioimaging requires a good understanding of the degradability of these particles under physiological conditions. Optimally, the degradability should be studied in vivo using relevant administration routes and dosings, but such studies are complicated and expensive. Thus, the biodegradability is often studied in vitro using simulated body fluids. However, such studies are scarce to date, and the results are partially conflicting. The aims of this study were therefore (a) to determine the influence of the composition of different simulated body fluids on the observed silica dissolution rates and (b) to establish morphological key parameters that determine the dissolution kinetics of silica nanoparticles. As dissolution media, simulated body fluid (SBF), simulated lung fluid (SLF), simulated gastric juice (SGF) and PBS buffer were used, and the silica concentration was kept below the silica saturation limit. Three mesoporous silica particles of different sizes were studied together with one non-porous Stöber-type silica particle. The observed silica dissolution rates followed the order SLF > SBF ≈ PBS ≫ SGF. Apart from general pH effects, the presence of organic acids in SLF is suggested to enhance the silica dissolution rate. The specific surface area was identified as the main parameter controlling the rate of dissolution of the different silica particles studied, while particle size influences were minor. Graphical Abstract: The dissolution of mesoporous silicas with different particle sizes has been studied in four different physiological buffers. [ABSTRACT FROM AUTHOR]

Although stainless steel is a material widely used for biomedical applications, its surface properties for long term application are still a serious concern. 316L stainless steel (SS 316L) is a material commonly used in dentistry for orthodontic braces, wires and in some cases as dental crowns. The pH value of natural saliva from the oral cavity can undergo sudden modification due to food products which are rich in citric acid. The electrochemical corrosion behavior of 316L stainless steel was evaluated in two simulated body fluid solutions, Fusayama-Mayer artificial saliva with pH=5 and Fusayama-Mayer artificial saliva adjusted with citric acid to a pH=1.58 which simulates the environmental conditions of the oral cavity. The surface of SS316L was investigated by optical microscope before and after corrosion assays. The electrochemical corrosion behavior was studied by open circuit potential, potenitodynamic polarization and linear polarization. Optical microscopy was used to characterize the corrosion damage after the electrochemical assays. [ABSTRACT FROM AUTHOR]

Transient cartilage and a mineralizing microenvironment play pivotal roles in mesenchymal cell ossification during bone formation. In order to recreate these microenvironmental cues, C3H10T1/2 murine mesenchymal stem cells (MSCs) were exposed to chondrocyte-conditioned medium (CM) and seeded onto three-dimensional mineralized scaffolds for bone regeneration. Expansion of C3H10T1/2 cells with CM resulted in enhanced expression levels of chondrogenic markers such as aggrecan, type II collagen, type X collagen, and Sox9, rather than of osteogenic genes. Interestingly, CM expansion led to reduced expression levels of osteogenic genes such as alkaline phosphatase ( ALP), type I collagen, osteocalcin, and Runx2. However, CM-expanded C3H10T1/2 cells showed enhanced osteogenic differentiation as indicated by increased ALP and Alizarin Red S staining upon osteogenic factor exposure. In vivo, CM-expanded C3H10T1/2 mesenchymal cells were seeded onto mineralized scaffolds (fabricated with polydopamine and coated with simulated body fluids) and implanted into critical-sized calvarial-defect mouse models. After 8 weeks of implantation, mouse skulls were collected, and bone tissue regeneration was evaluated by micro-computed tumography and Masson's trichrome staining. In accordance with the in vitro analysis, CM-expanded C3H10T1/2 cells gave enhanced bone mineral deposition. Thus, chondrocyte-conditioned factors and a mineralized microenvironment stimulate the bone formation of MSCs. [ABSTRACT FROM AUTHOR]

The electrochemical corrosion behaviour of biomedical Ti-25Nb-3Mo-3Zr-2Sn (TLM) alloy was investigated in various simulated body fluids at 37±0.5° utilising potentiodynamic polarisation and current-time curves. The Ti-6Al-4V (TC4) alloy was also investigated to make a comparison. The different simulated body fluids comprised of 0.9%NaCl saline, Hank's and Ringer's solution were employed. The effect of heat treatment on the electrochemical behaviour of the TLM alloy was also considered. It was discovered that all the test specimens were passivated once immersed into the simulated body fluids. It was also found that the TLM alloy has poorer corrosion resistance in Hank's solution, due to the chemical composition of the Hank's. After different heat treated, the TLM alloy had different phases and microstr°ture, and the corrosion behaviour of the TLM alloy was different. In this study, after the heat treatment of 760°/1 h/AC+550°/6 h/AC, the TLM alloy had better corrosion resistance. Owing to the corrosion resistance of the TLM alloy was influenced by numerous factors, s°h as microstr°ture and the chemical composition of electrolyte, the corrosion behaviour of the TLM alloy is complex. By comparing with the corrosion behaviour of the TC4 alloy, the TLM alloy has poorer corrosion resistant than the TC4 alloy under the same conditions. But the current-time curves of the TLM alloy were more stable than these of the TC4 alloy with further experiments, because of the more passivation film on the surface of the TLM alloy. [ABSTRACT FROM AUTHOR]

Objective: To determine the micro hardness of novel Pakistani manufactured osteosynthetic titanium bone mini plates (MPP) and imported osteosynthetic titanium bone mini plates (MPG) in body like conditions. Study Design: Descriptive study. Place and Duration of Study: This study was carried out at School of Chemical and Material Engineering, NUST from March to May 2013. Material and Methods: Microvicker hardness tester was used for assessment of micro hardness of two types of plates. The hardness was checked before conditioning and after conditioning at (six different places) on interval of 1, 7,14,21,28 and 40 days in modified simulated body fluid with ph 7.4 and temperature 37°C. Results: Result showed that hardness of MPG was higher than MPP and after conditioning in simulated body fluid at all time periods, hardness of both types of plates was increased. Conclusion: It can be concluded from this study that micro hardness of imported plates is more than local plates so recommendations should be sent to manufacturers of local industry of Pakistan to improve the hardness of local plates so that they can meet international standards. [ABSTRACT FROM AUTHOR]

Abstract: The effect of particle size distribution, binder content, processing parameters, and sintering schedule on the microstructure and mechanical properties of porous constructs was investigated. The porous constructs were produced by indirect selective laser sintering (SLS) of 13-93 bioactive glass using stearic acid as a polymeric binder. The binder content and d 50 particle size in the feedstock powders were simultaneously reduced from 22 to 12wt% and from 20 to 11μm, respectively, to identify the minimum binder content required for the SLS fabrication. An average particle size of ∼16μm with a binder content of 15wt% significantly reduced post-processing time and improved mechanical properties. Increasing the laser power and scan speed at the energy density of 1cal/cm2 maintained the feature sharpness of the parts during the fabrication of green parts and could almost double the mechanical properties of the sintered parts. Changes in the heating rates, ranging from 0.1 to 2°C/min, during the post-processing of the fabricated “green” scaffolds showed that the heating rate significantly affects the densification and mechanical properties of the sintered scaffolds. The compressive strength of the scaffolds manufactured with the optimized parameters varied from 41MPa, for a scaffold with a porosity of ∼50%, to 157MPa, for a dense part. The bioactive scaffolds soaked in simulated body fluids for durations up to 6 weeks were used to evaluate the change in mechanical properties in vitro. [Copyright &y& Elsevier]

Abstract: Hydroxyapatite (HAp) nano-rods were successfully synthesized by a modified sol–gel method using a solution of CaCl2·2H2O in water, along with a solution of H3PO4 in triethylamine and NH4OH as starting materials. The Ca/P molar ratio was maintained at 1.67. The sol obtained was dried in an oven for 2days at 100°C after being dialyzed for 12h. Pellets were made from the crystalline powders and immersed in simulated body fluid (SBF) to check its biocompatibility after 15, 45 and 180days of immersion. The HAp powders and pellets were characterized by X-Ray Diffraction crystallography (XRD), Fourier transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The HAp nano-rods had an average diameter of 25nm and length 110–120nm. Immersion of the HAp pellets in SBF led to the formation of a highly porous interconnecting HAp layer on the surface. The porosity increased with increase in immersion time. [Copyright &y& Elsevier]

Biomimetic formation of extracellular matrix (ECM) like coatings on artificial biomaterials provides a promising route to gain bioactive materials for tissue engineering applications. Organic ECM is also a template for apatite mineralization in bone tissue. This study was aimed at designing a multilayer film containing an ECM-like molecule on biomaterial surfaces to direct apatite mineralization and to develop biomimetic biomaterials for bone tissue engineering. A multilayer film consisting of gelatin and poly(ethylenimine) molecules was formed on a poly(L-lactic acid) substrate via electrostatic self-assembly technique. Bone-like apatite coating was formed on the multilayer film modified poly(L-lactic acid) substrate in simulated body fluids (SBFs). The amount of forming apatite could be controlled by the Ca2+ and HPO4 2- concentrations in SBF and also through the mineralization time. Gelatin terminated multilayer film can induce the apatite formation with a weak orientation in the (002) plane and the apatite is similar in composition to the natural bone. The gelatin multilayer film/apatite composite coating may serve as a promising microenvironment for bone tissue formation and growth. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) is extensively used to characterise the surface of materials used in bioengineering. Its ability to characterise both the elemental composition and structural characteristics of the surface makes it particularly useful, as it can identify the functional groups present on the surface of any material and implicitely give insight into biointerfacial interactions. The paper summarizes some XPS results obtained on compact and porous materials with potential biomedical applications, before and after their interaction with simulated body fluids. [ABSTRACT FROM AUTHOR]

The deposition of a bonelike mineral on the surface of polymer scaffolds results in the formation of hybrid biomaterials, possessing enhanced osteoconductivity while retaining appropriate biodegradability. However, current methods of fabricating such composite scaffolds use a prolonged incubation process, which permits scaffold deformation and premature loss of incorporated macromolecules. We hypothesized that the fabrication of biomineralized polymer scaffolds could be achieved using premineralized polymer microspheres generated through incubation in a modified simulated body fluid (mSBF). We explored the material characteristics of these substrates and characterized the in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs) when cultured on these novel scaffolds. Unlike scaffolds prepared using the conventional approach, premineralized scaffolds maintained their initial conformation after fabrication, achieved improved mineral distribution throughout the substrate, and enabled significantly greater incorporation efficiency of a model protein. We did not detect differences in osteogenic differentiation as determined by alkaline phosphatase activity and osteopontin secretion. However, we did observe a significant increase in cell-secreted calcium by hMSCs seeded on scaffolds prepared from premineralized polymer. These results demonstrate that the use of premineralized polymeric materials to fabricate biodegradable polymer scaffolds is an improved method for composite scaffold formation and may have numerous advantages for use in bone tissue engineering. [ABSTRACT FROM AUTHOR]