Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Enhanced photocatalytic and antibacterial performance of CeO2-loaded carboxymethyl chitosan nanocomposites

Carboxymethyl chitosan (CMCs) was loaded with two different concentrations of cerium dioxide (CeO2), specifically 0.3 g and 0.6 g, and compared with CMCs. XRD, FTIR and SEM analyses were used to evaluate the structural and morphological characteristics. The nanocomposites were examined for their photocatalytic degradation of Methylene Blue (MB) dye and antibacterial capabilities. Various parameters, including catalyst concentration, dye concentration, and pH levels, were assessed to determine the photocatalytic degradation efficiency of MB dye. The results demonstrated that the 0.6CeO2/CMCs nanocomposite outperformed the 0.3CeO2/CMCs and pure CMCs in terms of photocatalytic performance, achieving complete degradation of MB dye within 210 and 240 min after treatment with 0.3CeO2/CMCs and 0.6CeO2/CMCs nanocomposites. The agar well diffusion test was employed to assess the antibacterial activity of the nanocomposites against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. 0.6CeO2/CMCs nanocomposite exhibited the highest antibacterial effectiveness, with zones of inhibition measuring 29 ± 0.63 mm for E. coli, 28 ± 0.18 mm for P. aeruginosa, 25.5 ± 0.25 mm for S. aureus, and 23.6 ± 0.51 mm for E. faecalis. Additionally, the durability and reusability of the nanocomposites were confirmed after undergoing 5 cycles of MB dye degradation, with only a slight decrease in efficiency. The findings of this study highlight the potential of CeO2/CMCs nanocomposites as powerful antibacterial and photocatalysts with important implications for environmental and biological applications.

Green Pesticide High Activity Based on TiO2 Nanosuspension Incorporated Silver Microspheres Against Phytophthora palmivora

Cocoa pod production has experienced a significant decline due to attacks by the Phytophthora palmivora (P. palmivora) fungus, which is the main cause of cocoa pod rot. To overcome this problem, Titanium dioxide (TiO2) was chosen because of its potential as an antifungal, and its activity can be increased by adding silver nanoparticles (AgNPs). This research aims to determine the antifungal properties of TiO2-Ag nanosuspension on the growth of P. palmivora under exposure to UV, Visible and without irradiation. The sol-gel process was used to synthesize TiO2, and ultrasonics was used to integrate silver nanoparticles into TiO2. Characterization of UV-Vis diffuse reflectance spectroscopy (UV-DRS) shows a change in the energy gap from 3.24 to 2.82 eV. The Fourier confirmed the crystal structure of the TiO2-Ag anatase transform infrared spectroscopy (FTIR) spectrum, which showed the stretching vibration peak of the Ti-O and Ag-O bonds (463.88 cm-1). Particle size analysis (PSA) characterization revealed that the nanoscale of TiO2-Ag was 92.4 nm. The disc diffusion method was used to test the antifungal inhibitory of 0.1%, 0.3%, and 0.5% TiO2-Ag against P. palmivora. The antifungal activity of the TiO2-Ag showed strong resistance under exposure to visible light, and the optimum concentration of TiO2-Ag was 0.5%.

Recent Advances in Antibacterial Strategies Based on TiO2 Biomimetic Micro/Nano-Structured Surfaces Fabricated Using the Hydrothermal Method

Ti and its alloys, widely utilized in orthopedic and dental implants, inherently lack antibacterial properties, posing significant infection risks, especially in the context of growing antibiotic resistance. This review critically evaluates non-antibiotic antibacterial strategies, with a particular focus on surface modifications and micro/nano-structured surfaces. Micro/nano-structured surfaces, inspired by natural topographies, utilize physical mechanisms to eradicate bacteria. Despite their potential, the antibacterial efficacy of these surfaces remains insufficient for clinical application. Titanium dioxide (TiO2), known for its excellent photocatalytic antibacterial activity and biocompatibility, is emerging as an ideal candidate for enhancing micro/nano-structured surfaces. By combining the photocatalytic antibacterial effects of TiO2 with the mechanical bactericidal properties of micro/nano-structured surfaces, superior antibacterial performance can be achieved. The hydrothermal method is frequently employed to fabricate TiO2 micro/nano-structured surfaces, and this area of research continues to thrive, particularly in the development of antibacterial strategies. With demonstrated efficacy, combined antibacterial strategies based on TiO2 micro/nano-structured surfaces have become a prominent focus in current research. Consequently, the integration of physical stimulation and chemical release mechanisms may represent the future direction for TiO2 micro/nano-structured surfaces. This review aims to advance the study of TiO2 micro/nano-structured surfaces in antibacterial applications and to inspire more effective non-antibiotic antibacterial solutions.

Mechanistic Insights into Toxicity of Titanium Dioxide Nanoparticles at the Micro- and Macro-levels

Titanium oxide nanoparticles (TiO2 NPs) have been regarded as a legacy nanomaterial due to their widespread usage across multiple fields. The TiO2 NPs have been and are still extensively used as a food and cosmetic additive and in wastewater and sewage treatment, paints, and industrial catalysis as ultrafine TiO2. Recent developments in nanotechnology have catapulted it into a potent antibacterial and anticancer agent due to its excellent photocatalytic potential that generates substantial amounts of highly reactive oxygen radicals. The method of production, surface modifications, and especially size impact its toxicity in biological systems. The anatase form of TiO2 (<30 nm) has been found to exert better and more potent cytotoxicity in bacteria as well as cancer cells than other forms. However, owing to the very small size, anatase particles are able to penetrate deep tissue easily; hence, they have also been implicated in inflammatory reactions and even as a potent oncogenic substance. Additionally, TiO2 NPs have been investigated to assess their toxicity to large-scale ecosystems owing to their excellent reactive oxygen species (ROS)-generating potential compounded with widespread usage over decades. This review discusses in detail the mechanisms by which TiO2 NPs induce toxic effects on microorganisms, including bacteria and fungi, as well as in cancer cells. It also attempts to shed light on how and why it is so prevalent in our lives and by what mechanisms it could potentially affect the environment on a larger scale.

Dhvar5-chitosan nanogels and their potential to improve antibiotics activity

Infection is one of the main causes of orthopedic implants failure, with antibiotic-resistant bacteria playing a crucial role in this outcome. In this work, antimicrobial nanogels were developed to be applied in situ as implant coating to prevent orthopedic-device-related infections. To that regard, a broad-spectrum antimicrobial peptide, Dhvar5, was grafted onto chitosan via thiol-norbornene "photoclick" chemistry. Dhvar5-chitosan nanogels (Dhvar5-NG) were then produced using a microfluidic system. Dhvar5-NG (1010 nanogels (NG)/mL) with a Dhvar5 concentration of 6 μg/mL reduced the burden of the most critical bacteria in orthopedic infections - methicillin-resistant Staphylococcus aureus (MRSA) - after 24 h in medium supplemented with human plasma proteins. Transmission electron microscopy showed that Dhvar5-NG killed bacteria by membrane disruption and cytoplasm release. No signs of cytotoxicity against a pre-osteoblast cell line were verified upon incubation with Dhvar5-NG. To further explore therapeutic alternatives, the potential synergistic effect of Dhvar5-NG with antibiotics was evaluated against MRSA. Dhvar5-NG at a sub-minimal inhibitory concentration (109 NG/mL) demonstrated synergistic effect with oxacillin (4-fold reduction: from 2 to 0.5 μg/mL) and piperacillin (2-fold reduction: from 2 to 1 μg/mL). This work supports the use of Dhvar5-NG as adjuvant of antibiotics to the prevention of orthopedic devices-related infections.

Review of Antimicrobial Properties of Titanium Dioxide Nanoparticles

There is a growing interest in the utilization of metal oxide nanoparticles as antimicrobial agents. This review will focus on titanium dioxide nanoparticles (TiO2 NPs), which have been demonstrated to exhibit high antimicrobial activity against bacteria and fungi, chemical stability, low toxicity to eukaryotic cells, and therefore high biocompatibility. Despite the extensive research conducted in this field, there is currently no consensus on how to enhance the antimicrobial efficacy of TiO2 NPs. The aim of this review is to evaluate the influence of various factors, including particle size, shape, composition, and synthesis parameters, as well as microbial type, on the antibacterial activity of TiO2 NPs against bacteria and fungi. Furthermore, the review offers a comprehensive overview of the methodologies employed in the synthesis and characterization of TiO2 NPs. The antimicrobial activity of TiO2 exhibits a weak dependence on the microorganism species. A tendency towards increased antibacterial activity is observed with decreasing TiO2 NP size. The dependence on the shape and composition is more pronounced. The most pronounced antimicrobial potential is exhibited by amorphous NPs and NPs doped with inorganic compounds. This review may be of interest to specialists in biology, medicine, chemistry, and other related fields.

Synergistic effect of SrTiO3/CuFe2O4/MIL-101(Co) as a MOF composite under Gamma-rays for antimicrobial potential versus bacteria and pathogenic fungi

The primary emphasis of this study was on the innovative and scientifically valuable hydrothermal synthesis of MIL-101(Co) as a metal-organic framework (MOF) material. Subsequently, the CuFe2O4 was incorporated into the MOF by a reduction-precipitation technique. The SrTiO3/CuFe2O4/MIL-101(Co) composite was synthesized by using hydrothermal in situ growth process. The XRD and FESEM investigations of the SrTiO3/CuFe2O4/MIL-101(Co) composite definitively verified its crystalline structure and proved its production with exact shape and dimensions. The data indicated that Candida albicans displayed the greatest vulnerability to all three produced materials, with reported Minimum Inhibitory Concentration (MIC) values of 500 µg mL-1 for MIL-101(Co). The CuFe2O4/MIL-101(Co) compound, when produced, exhibits MIC values of 200 µg mL-1. Additionally, the combination of CuFe2O4/MIL-101(Co) with SrTiO3, shows MIC values of 50 µg mL-1. The results also indicated that the MIC values for MIL-101(Co), and CuFe2O4/MIL-101(Co) against S. aureus were 100 µg mL-1. Ultimately, SrTiO3/CuFe2O4/MIL-101(Co) exhibited identical MIC values of 50 µg mL-1 against S. aureus. The concentration of the bacterial protein was increased by adding MIL-101(Co), CuFe2O4/MIL-101(Co), and SrTiO3/CuFe2O4/MIL-101(Co). The antibacterial capabilities of the SrTiO3/CuFe2O4/MIL-101(Co) were increased after being subjected to gamma doses of 100.0 kGy. This process paves a ways for manufacturing innovation in near future.

Antipathogenic Applications of Copper Nanoparticles in Air Filtration Systems

The COVID-19 pandemic has underscored the critical need for effective air filtration systems in healthcare environments to mitigate the spread of viral and bacterial pathogens. This study explores the utilization of copper nanoparticle-coated materials for air filtration, offering both antiviral and antimicrobial properties. Highly uniform spherical copper oxide nanoparticles (~10 nm) were synthesized via a spinning disc reactor and subsequently functionalized with carboxylated ligands to ensure colloidal stability in aqueous solutions. The functionalized copper oxide nanoparticles were applied as antipathogenic coatings on extruded polyethylene and melt-blown polypropylene fibers to assess their efficacy in air filtration applications. Notably, Type IIR medical facemasks incorporating the copper nanoparticle-coated polyethylene fibers demonstrated a >90% reduction in influenza virus and SARS-CoV-2 within 2 h of exposure. Similarly, heating, ventilation, and air conditioning (HVAC) filtration pre- (polyester) and post (polypropylene)-filtration media were functionalised with the copper nanoparticles and exhibited a 99% reduction in various viral and bacterial strains, including SARS-CoV-2, Pseudomonas aeruginosa, Acinetobacter baumannii, Salmonella enterica, and Escherichia coli. In both cases, this mitigates not only the immediate threat from these pathogens but also the risk of biofouling and secondary risk factors. The assessment of leaching properties confirmed that the copper nanoparticle coatings remained intact on the polymeric fiber surfaces without releasing nanoparticles into the solution or airflow. These findings highlight the potential of nanoparticle-coated materials in developing biocompatible and environmentally friendly air filtration systems for healthcare settings, crucial in combating current and future pandemic threats.

Dynamic Hydrogels against Infections: From Design to Applications

Human defense against infection remains a global topic. In addition to developing novel anti-infection drugs, therapeutic drug delivery strategies are also crucial to achieving a higher efficacy and lower toxicity of these drugs for treatment. The application of hydrogels has been proven to be an effective localized drug delivery approach to treating infections without generating significant systemic adverse effects. The recent emerging dynamic hydrogels further show power as injectable formulations, giving new tools for clinical treatments. In this review, we delve into the potential applications of dynamic hydrogels in antibacterial and antiviral treatments and elaborate on their molecular designs and practical implementations. By outlining the chemical designs underlying these hydrogels, we discuss how the choice of dynamic chemical bonds affects their stimulus responsiveness, self-healing capabilities, and mechanical properties. Afterwards, we focus on how to endow dynamic hydrogels with anti-infection properties. By comparing different drug-loading methods, we highlight the advantages of dynamic chemical bonds in achieving sustained and controlled drug release. Moreover, we also include the design principles and uses of hydrogels that possess inherent anti-infective properties. Furthermore, we explore the design principles and applications of hydrogels with inherent anti-infective properties. Finally, we briefly summarize the current challenges faced by dynamic hydrogels and present a forward-looking vision for their future development. Through this review, we expect to draw more attention to these therapeutic strategies among scientists working with chemistry, materials, as well as pharmaceutics.

Metallic nanoparticle actions on the outer layer structure and properties of Bacillus cereus and Staphylococcus epidermidis

Although the antimicrobial activity of nanoparticles (NPs) penetrating inside the cell is widely recognised, the toxicity of large NPs (>10 nm) that cannot be translocated across bacterial membranes remains unclear. Therefore, this study was performed to elucidate the direct effects of Ag-NPs, Cu-NPs, ZnO-NPs and TiO2-NPs on relative membrane potential, permeability, hydrophobicity, structural changes within chemical compounds at the molecular level and the distribution of NPs on the surfaces of the bacteria Bacillus cereus and Staphylococcus epidermidis. Overall analysis of the results indicated the different impacts of individual NPs on the measured parameters in both strains depending on their type and concentration. B. cereus proved to be more resistant to the action of NPs than S. epidermidis. Generally, Cu-NPs showed the most substantial toxic effect on both strains; however, Ag-NPs exhibited negligible toxicity. All NPs had a strong affinity for cell surfaces and showed strain-dependent characteristic dispersion. ATR-FTIR analysis explained the distinctive interactions of NPs with bacterial functional groups, leading to macromolecular structural modifications. The results presented provide new and solid evidence for the current understanding of the interactions of metallic NPs with bacterial membranes.

Undesirable consequences of the metallic nanoparticles action on the properties and functioning of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis membranes

Controversial and inconsistent findings on the toxicity of metallic nanoparticles (NPs) against many bacteria are common in recorded studies; therefore, further advanced experimental work is needed to elucidate the mechanisms underlying nanotoxicity. This study deciphered the direct effects of Ag-NPs, Cu-NPs, ZnO-NPs and TiO₂-NPs on membrane permeability, cytoplasmic leakage, ATP level, ATPase activity and fatty acid profiling of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis as model microorganisms. A multifaceted analysis of all collected results indicated the different influences of individual NPs on the measured parameters depending on their type and concentration. Predominantly, membrane permeability was correlated with increased cytoplasmic leakage, reduced total ATP levels and ATPase activity. The established fatty acid profiles were unique and concerned various changes in the percentages of hydroxyl, cyclopropane, branched and unsaturated fatty acids. Decisively, E. coli was more susceptible to changes in measured parameters than B. cereus and S. epidermidis. Also, it was established that ZnO-NPs and Cu-NPs had a major differentiating impact on studied parameters. Additionally, bacterial cell imaging using scanning electron microscopy elucidated different NPs distributions on the cell surface. The presented results are believed to provide novel, valuable and accumulated knowledge in the understanding of NPs action on bacterial membranes.