Dissociation of magnesium oxide and magnesium hydroxide nanoparticles in physiologically relevant fluids

Abstract

Magnesium oxide (MgO) and hydroxide [Mg(OH) 2 ] are conventionally considered insoluble in water and stable at high temperatures. However, in this study, we found significant dissociation of MgO and Mg(OH) 2 into ions when they were immersed in different physiologically relevant solutions in the form of 20nm and 10-nm nanoparticles respectively, under standard cell culture conditions in vitro, i.e., a 37°C, 5% CO 2 /95% air, sterile, humidified environment. The change in Mg 2+ ion concentrations and pH measured in the physiologically relevant solutions (e.g., Dulbecco's modified Eagle's Medium (DMEM), simulated body fluid (SBF), relevant chloride solutions, and deionized water) confirmed their dissociation. Possible mechanisms and contributing factors for dissociation of MgO and Mg(OH) 2 nanoparticles were discussed. The evidence suggests that nucleophilic substitution of OH − by Cl − in Mg(OH) 2 is energetically unfavorable and it is more likely that Cl − plays a role in the stabilization of intermediate forms of MgO and Mg(OH) 2 as it dissociates. The pH and buffering capability of the immersion solutions might have played the most significant role in dissociation of these nanoparticles when compared with the roles of chloride (Cl − ), proteins, and different buffering agents. This article provided the first evidence on the dissociation of MgO and Mg(OH) 2 nanoparticles in physiologically relevant conditions and elucidated possible factors contributing to the observed behaviors of these nanoparticles in vitro, which is important for their potential medical applications in vivo. Keywords Magnesium oxide (MgO) nanoparticles . Magnesium hydroxide [Mg(OH) 2 ] nanoparticles . Biofluids . Dulbecco's modified Eagle's Medium (DMEM) . Simulated body fluid (SBF) . HEPES buffer . Chloride (Cl − ) solutions

Cytotoxicity Assessment of Surface-Modified Magnesium Hydroxide Nanoparticles

“…Indeed, the dissociation of Mg(OH) 2 is known to be heavily influenced by pH and temperature, with the physiological pH (7.2–8.2) promoting its dissociation. 33 The media pH of NP concentrations between 156.3 and 19.5 μg/mL ( Figure 4 ) corresponds to this range, thus explaining higher NP dissociation in low concentrations. Indeed, another study confirmed full degradation, hence 100% dissociation, of Mg(OH) 2 NPs at 200 μg/mL.…”

In vivo urinary compatibility of Mg-Sr-Ag alloy in swine model

“…In an examination of antimicrobial activities of biodegradable magnesium based materials, Nguyen et al [ 19 ] identified several possible mechanisms of antimicrobial activity that may occur as a single activity or in tandem, including oxidative stress, interruption of quorum sensing processes, and changes in Ca 2+ ion concentrations in extracellular fluids that result from the degradation of magnesium. The effects of these activities may also be dependent on the thickness of Gram-positive and Gram-negative peptidoglycan structures and the presence of an outer cell membrane in Gram-negative bacteria [ 20 ]. Additionally, although magnesium metal degradation leads to the release of hydrogen ions (H + ) into the surrounding solution, here it was shown that inhibition of bacterial growth was not a result of the effects of hydrogen ion release [ 19 , 20 ].…”

“…The effects of these activities may also be dependent on the thickness of Gram-positive and Gram-negative peptidoglycan structures and the presence of an outer cell membrane in Gram-negative bacteria [ 20 ]. Additionally, although magnesium metal degradation leads to the release of hydrogen ions (H + ) into the surrounding solution, here it was shown that inhibition of bacterial growth was not a result of the effects of hydrogen ion release [ 19 , 20 ]. Lock et al [ 21 ] identified a significant decrease in bacterial proliferation when magnesium alloys degraded in artificial urine.…”

“…Therefore, biodegradable stents are gaining increasing research interest duo to their natural advantage of constantly degrading surface, which are immune to biofilm formation [ [16] , [17] , [18] ]. Like the other two commonly studied biodegradable metallic materials, iron and zinc, magnesium and its alloys also have inherent antimicrobial activities [ 8 , 19 , 20 ]. Lock et al [ 21 ] identified a significant decrease in bacterial proliferation when magnesium alloys degraded in artificial urine, and similar phenomena were also reported by Zhang et al [ 22 ].…”

Morphology Design and Fabrication of Bio-Inspired Nano-MgO–Mg(OH)2 via Vapor Steaming to Enable Bulk CO2 Diffusion and Capture

“…Environmentally friendly nanomaterials have recently become vital in a variety of research and development domains. Magnesium oxide (MgO) and magnesium hydroxide (Mg(OH) 2 ) are two of the most environmentally friendly materials when compared to other materials [3][4][5]. For properties such as flame resistance, dielectric resistance, and mechanical strength; and micro structural properties such as porosity, large surface area catalysis, acid-base sites, and gas adsorption, MgO is well received in industrial applications such as ceramics, cement, and water treatments [2,[5][6][7][8][9][10][11].…”