Synthesis and characterization of nanoparticles and composites as bactericides

Boosting environmental remediation: harnessing the efficiency of graphitic carbon nitride stabilized on red ocher surface for enhanced photocatalytic remove of Escherichia coli

In the present study, the antibacterial effect of graphitic carbon nitride coated on the red ocher was investigated by the photocatalytic process to remove Gram-negative Escherichia coli bacteria. The concentration effects (0.025, 0.05, and 0.1 g/mL) of disinfectant, contact time (30, 60, and 90 min), and the number of bacteria (102, 104, and 106 CFU/mL) were examined. In this research, in each experiment, 100 mL of the sample was taken, and the test work was performed. The red ocher required for this project was obtained from Hormoz Island, Hormozgan Province, Iran. Melamine was used for the synthesis and manufacture of graphitic carbon nitride. A general-purpose media was used for microbial culture using the pour and spread plate methods, as well as an LED lamp with a wavelength of 420 nm as a light source for the photocatalytic process. To obtain the important factors, the interaction of the factors and the optimal experimental design were used through the response surface methodology (RSM) based on the Box-Behnken design. According to research findings, this method is effective in eliminating E. coli. The results showed that the increase in the amount of disinfectant from 0.025 to 0.1 g/mL and also the increase of contact time from 30 to 90 min accelerated the removal rate of E. coli. The numerical value of R2 obtained for the removal of E. coli was 0.9728, indicating good agreement between experimental and predicted data. Therefore, its utilization in water disinfection seems necessary, both to ensure human health and environmental protection.

MIL-101 (Fe) @Ag Rapid Synergistic Antimicrobial and Biosafety Evaluation of Nanomaterials

Metal-organic frameworks (MOFs), which have become popular in recent years as excellent carriers of drugs and biomimetic materials, have provided new research ideas for fighting pathogenic bacterial infections. Although various antimicrobial metal ions can be added to MOFs with physical methods, such as impregnation, to inhibit bacterial multiplication, this is inefficient and has many problems, such as an uneven distribution of antimicrobial ions in the MOF and the need for the simultaneous addition of large doses of metal ions. Here, we report on the use of MIL-101(Fe)@Ag with efficient metal-ion release and strong antimicrobial efficiency for co-sterilization. Fe-based MIL-101(Fe) was synthesized, and then Ag+ was uniformly introduced into the MOF by the substitution of Ag+ for Fe3+. Scanning electron microscopy, powder X-ray diffraction (PXRD) Fourier transform infrared spectroscopy, and thermogravimetric analysis were used to investigate the synthesized MIL-101(Fe)@Ag. The characteristic peaks of MIL-101(Fe) and silver ions could be clearly seen in the PXRD pattern. Comparing the diffraction peaks of the simulated PXRD patterns clearly showed that MIL-101(Fe) was successfully constructed and silver ions were successfully loaded into MIL-101(Fe) to synthesize an MOF with a bimetallic structure, that is, the target product MIL-101(Fe)@Ag. The antibacterial mechanism of the MOF material was also investigated. MIL-101(Fe)@Ag exhibited low cytotoxicity, so it has potential applications in the biological field. Overall, MIL-101(Fe)@Ag is an easily fabricated structurally engineered nanocomposite with broad-spectrum bactericidal activity.

Assessing the potential biological activities of TiO2 and Cu, Ni and Cr doped TiO2 nanoparticles

Nanoparticles are like magic bullets and nanomaterials exhibit appealing properties. Their size and morphology can be switched by dopants for certain biological activities. Nanoparticles in combination with certain drugs enhance the antibiotic effects and may be valuable in combating bacterial resistance. The antimicrobial potency of nanoparticles depends upon their ability to bind to the surface of microbial cell membranes resulting in modulation of basic cell functions such as respiration. We report herein the antibacterial, antifungal and antioxidant activities of pure TiO₂ and TiO₂ doped with 4% Cu, Ni and Cr. The performance of pure and doped nanoparticles has been compared with reference compounds. A comparison of the antifungal activities of the samples doped with TiO₂ reveals that Cu-TiO₂ exhibits improved performance against A. fumigatus but lower antifungal activity against Mucor sp. and F. solani. Cu-TiO₂ and Ni-TiO₂ showed good antibacterial action against B. bronchiseptica, while Cr-TiO₂ nanoparticles displayed better activity against S. typhimurium as compared to pure TiO₂. Moreover, pristine TiO₂ and Ni-TiO₂ nanoparticles were found to demonstrate maximum total antioxidant capacity.

Design of a Controlled-Release Delivery Composite of Antibacterial Agent Gatifloxacin by Spherical Silica Nanocarrier

In this study, a spherical silica nanoparticle was explored as a gatifloxacin carrier synthesized by the chemical precipitation method. It was found that there was no new chemical bond formation during the loading process between gatifloxacin and silica, which implies that the binding was driven by physical interaction. In addition, the drug loading and encapsulation efficiency could be improved by appropriately increasing nano-silica content in the loading process. Meanwhile, the release rate of gatifloxacin after loading nano-silica was also improved, suggesting the successful design of a controlled-release delivery composite. The silica nanocarrier could significantly improve the antibacterial performance of Escherichia coli by 2.1 times, which was higher than the pure gatifloxacin. The 24 h bacteriostatic rate was higher than that of a simple mixture of silica nanoparticles and gatifloxacin. Strong reactive oxygen species (ROS) in GAT-SiO₂ NPs suggests that ROS might be associated with bactericidal activity. The synergy between the physicochemical effect and ROS production of this material is proposed as the mechanism of its antibacterial activity, which can also be confirmed by the cell membrane damage observed under electron microscopy and DNA damage experiments. Collectively, our finding indicates that nano-silica microspheres could serve as a promising carrier for the sustained release of gatifloxacin, thereby providing a new carrier design scheme for the improvement of the antibacterial effect.

Zeolite for Potential Toxic Metal Uptake from Contaminated Soil: A Brief Review

Soil pollution is an increasingly urgent problem for the global environment. Soil can be contaminated with potential toxic metals from many anthropogenic activities, besides fossil fuel combustion and crude oil production, ranging from industry to mining and agriculture. Many technologies have been analysed to solve this type of environmental pollution and methods involving the use of minerals (e.g., clay minerals, zeolites, and natural silica adsorbents) are widely described in the literature. This article provides a summary of studies concerning the use of zeolites in soil remediation. A considerable number of these experiments were conducted using natural zeolites, while fewer concerned the utilization of synthetic zeolites. The mechanism controlling the successful application of these minerals was analysed through referring to global data published on this topic over the last few decades. This review also briefly discusses the limitations on zeolite applications and the drawbacks of the approaches analysed.