Preparation of controlled nano-MgO and investigation of its bactericidal properties

Nanofibrous Dressing with Nanocomposite Monoporous Microspheres for Chemodynamic Antibacterial Therapy and Wound Healing

The excessive use of antibiotics and consequent bacterial resistance have emerged as crucial public safety challenges for humanity. As a promising antibacterial treatment, using reactive oxygen species (ROS) can effectively address this problem and has the advantages of being highly efficient and having low toxicity. Herein, electrospinning and electrospraying were employed to fabricate magnesium oxide (MgO)-based nanoparticle composited polycaprolactone (PCL) nanofibrous dressings for the chemodynamic treatment of bacteria-infected wounds. By utilizing electrospraying, erythrocyte-like monoporous PCL microspheres incorporating silver (Ag)- and copper (Cu)-doped MgO nanoparticles were generated, and the unique microsphere-filament structure enabled efficient anchoring on nanofibers. The composite dressings produced high levels of ROS, as confirmed by the 2,7-dichloriflurescin fluorescent probe. The sustained generation of ROS resulted in efficient glutathione oxidation and a remarkable bacterial killing rate of approximately 99% against Staphylococcus aureus (S. aureus). These dressings were found to be effective at treating externally infected wounds. The unique properties of these composite nanofibrous dressings suggest great potential for their use in the medical treatment of bacteria-infected injuries.

Evaluation of Nanomagnesium Oxide in Combination with Garlic Extract as an Endodontic Irrigant: An In Vitro Study

AIM

The aim of this in vitro study was to evaluate the effectiveness of the combination of garlic extract in combination with magnesium oxide (MgO) for use as an endodontic irrigant at various contact times.

MATERIALS AND METHODS

All 48 teeth were divided into 6 groups according to irrigation used after inoculation with Enterococcus faecalis and incubation. The control groups consisted of saline and sodium hypochlorite (NaOCl) used as irrigants and the test groups employed garlic extract combined with nano-magnesium oxide (nano-MgO) used as irrigant with two contact times, namely, 2 and 5 minutes, and garlic extract and nano-MgO used solely for 5 minutes each. Colony-forming units (CFUs) were counted after plating and incubation.

RESULTS

In NaOCl, and in both combination groups, there was a significant reduction in CFU counts. The saline group showed no decrease. Statistical analysis showed no difference in efficacy between NaOCl and the two combination groups. There was a statistical difference between the combination group and garlic/nano-MgO alone at both 2 and 5 minutes.

CONCLUSIONS

Under the conditions of this study, a novel irrigant, a combination of nanoparticles of MgO and garlic extract was as effective as NaOCl against E. faecalis in an in vitro model at two tested contact times.

CLINICAL SIGNIFICANCE

Combination of MgO nanoparticles and garlic extract achieves disinfection comparable to gold standard NaOCl without harmful caustic effects of hypochlorite.

MgO/carboxymethyl chitosan nanocomposite improves thermal stability, waterproof and antibacterial performance for food packaging

A novel nanocomposite film was fabricated by carboxymethyl chitosan (CMCS) and nano MgO for potential food packaging applications. The impregnation of MgO nanoparticles into CMCS was evidenced by the X-ray diffraction and FTIR spectroscopy. SEM micrographs revealed a dense layer of MgO formation in the CMCS matrix, which is a major contributor to the improvement of crystallinity. Compared with pure CMCS, CMCS/MgO composites confer improved thermal stability, better UV shielding performance, as well as water-insolubility, improving the feasibility of using CMCS-based biopolymer films as food packagings, especially in the case of water-rich food. These physical properties were further enhanced with the increase in MgO content. Furthermore, MgO nanoparticles can simultaneously provide CMCS with increased elasticity and ductility at a rather low filler content (1.0 % by weight). For biological properties, CMCS/MgO composites exhibited excellent antimicrobial activity against Listeria monocytogenes and Shewanella baltica.

The Green Synthesis of MgO Nano-Flowers Using Rosmarinus officinalis L. (Rosemary) and the Antibacterial Activities against Xanthomonas oryzae pv. oryzae

Recently, the use of herbs in the agriculture and food industry has increased significantly. In particular, Rosmarinus officinalis L. extracts have been reported to have strong antibacterial properties, which depend on their chemical composition. The present study displayed a biological method for synthesis of magnesium oxide (MgO) nano-flowers. The nano-flowers are developed without using any catalyst agent. Aqueous Rosemary extract was used to synthesize MgO nano-flowers (MgONFs) in stirring conditions and temperature at 70°C for 4 h. The mixture solution was checked by UV-Vis spectrum to confirm the presence of nanoparticles. The MgO nano-flowers powder was further characterized in this study by the X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. In addition, bacteriological tests indicated that MgO nano-flowers significantly inhibited bacterial growth, biofilm formation, and motility of Xanthomonas oryzae pv. oryzae, which is the causal agent of bacterial blight disease in rice. The electronic microscopic observation showed that bacterial cell death may be mainly due to destroy of cell integrity, resulting in leakage of intracellular content. As recommended, the use of Rosemary extract is an effective and green way to produce the MgO nano-flowers, which can be widely used in agricultural fields to suppress bacterial infection.

Physical, morphological, antimicrobial and release properties of novel MgO-bacterial cellulose nanohybrids prepared by in-situ and ex-situ methods

MgO-bacterial cellulose (BC) nanohybrids were fabricated by in-situ synthesis of nanoparticles (NPs) within BC network via two methods (the sonochemical and wet chemical). The ex-situ synthesized nanohybrid was prepared by immersing BC pellicles in the commercial MgO dispersion. The occurrence of new interactions between MgO-NPs and nanofibers was approved by Fourier transform infrared spectroscopy (FT-IR) spectra. X-ray diffraction (XRD) results indicated that the crystallinity index of nanofibers decreased after the formation of nanohybrid by the sonochemical in-situ method. The results of the field emission scanning electron microscopy (FE-SEM) indicated the formation of the small-sized NPs attached to the inner space of BC network at the in-situ synthesized nanohybrids. However, the agglomerated NPs precipitated on the surface of BC layer were observed for the ex-situ synthesized sample. The loading capacity of the ex-situ method was higher than that of the in-situ methods; but after 24 h, MgO releasing for in-situ and ex-situ synthesized nanohybrids was recorded about 16% and 28%, respectively. The antibacterial activity of the ex-situ synthesized nanohybrid against S. aureus and E. coli bacteria was more than those of both in-situ synthesized samples.

In vitro and ex vivo antimicrobial efficacy of nano-MgO in the elimination of endodontic pathogens

OBJECTIVES

The use of metal oxide nanoparticles has attracted lots of attention, mostly because of their promising antimicrobial activity along with their biocompatibility with mammalian cells. This study aims to investigate the in vitro and ex vivo antimicrobial efficiency of nano-magnesium oxide (MgO) aqueous solution against endodontic pathogens.

MATERIALS AND METHODS

The cytotoxicity of different concentrations of nano-MgO was assessed using lactate dehydrogenase cytotoxicity assay (LDH assay). A comparison of the antimicrobial efficiency of several concentrations of nano-MgO solution, sodium hypochlorite (NaOCl), and chlorhexidine (CHX) gluconate against Staphylococcus aureus, Enterococcus faecalis, and Candida albicans was made using the direct contact method. An ex vivo model of decoronated and experimentally infected human teeth was employed to compare the efficiency of nano-MgO (5 mg/L) solution with NaOCl (5.25 %) in the elimination of E. faecalis.

RESULTS

There was no statistically significant difference between nano-MgO solutions (10 and 5 mg/L), 5.25 % NaOCl, and 2 % CHX gluconate in terms of the required time to inhibit the growth of the tested pathogens (p > 0.05). The LDH assay showed no cytotoxicity of different concentrations of nano-MgO used in this study (p < 0.001). In the ex vivo model of infected human teeth, 6 h post-irrigation, there was no statistically significant difference between colony-forming units (CFU) per milliliter of nano-MgO (5 mg/L) and NaOCl (5.25 %)-treated teeth (5-6 log scale reduction). However, the nano-MgO group showed a significant decrease in colony-forming units per milliliter (7 log scale), 24 h post-irrigation (p < 0.05). At other tested time points-24, 48, 72, and 168 h-the levels of CFU per milliliter were significantly less in the nano-MgO group (2-3 log scale difference) compared to the NaOCl group, indicating long-term antibacterial activity of nano-MgO (p < 0.05). At 72 and 168 h post-irrigation, no detectable bacterial growth was observed in the nano-MgO group. The detection limit was 10 CFU/mL.

CONCLUSIONS

Nano-MgO aqueous solutions represent promising antimicrobial activities, both in vitro and ex vivo with minimal toxicity.

CLINICAL RELEVANCE

Compared to NaOCl (5.25 %), nano-MgO (5 mg/L) exhibits statistically significant long-term efficiency in the elimination of E. faecalis in the root canal system. After further investigations, nano-MgO could be considered as a new root canal irrigant.

Growth mechanisms of MgO nanocrystals via a sol-gel synthesis using different complexing agents

In the preparation of nanostructured materials, it is important to optimize synthesis parameters in order to obtain the desired material. This work investigates the role of complexing agents, oxalic acid and tartaric acid, in the production of MgO nanocrystals. Results from simultaneous thermogravimetric analysis (STA) show that the two different synthesis routes yield precursors with different thermal profiles. It is found that the thermal profiles of the precursors can reveal the effects of crystal growth during thermal annealing. X-ray diffraction confirms that the final products are pure, single phase and of cubic shape. It is also found that complexing agents can affect the rate of crystal growth. The structures of the oxalic acid and tartaric acid as well as the complexation sites play very important roles in the formation of the nanocrystals. The complexing agents influence the rate of growth which affects the final crystallite size of the materials. Surprisingly, it is also found that oxalic acid and tartaric acid act as surfactants inhibiting crystal growth even at a high temperature of 950°C and a long annealing time of 36 h. The crystallite formation routes are proposed to be via linear and branched polymer networks due to the different structures of the complexing agents.

Antibacterial and Wash Durability Properties of Untreated and Treated Cotton Fabric Using MgO and NiO Nanoparticles

We report an antibacterial and wash durability behaviour of MgO and NiO nanoparticles treated cotton fabric using sodium alginate as cross linker. The metal oxide nanoparticles treated cotton fabric using sodium alginate as a crosslinker was characterized employing SEM-EDX and their antibacterial activity was analyzed. The enhanced zone of inhibition and wash durability behaviour was observed for NiO nanoparticles treated fabric. However, MgO nanoparticles showed less significant antibacterial and wash durabilty activities when compared to NiO nanoparticles treated cotton fabrics.