Study of bismuth metal organic skeleton composites with photocatalytic antibacterial activity

Nanomedicines as disruptors or inhibitors of biofilms: Opportunities in addressing antimicrobial resistance

The problem of antimicrobial resistance (AMR) has caused global concern due to its great threat to human health. Evidences are emerging for a critical role of biofilms, one of the natural protective mechanisms developed by bacteria during growth, in resisting commonly used clinical antibiotics. Advances in nanomedicines with tunable physicochemical properties and unique anti-biofilm mechanisms provide opportunities for solving AMR risks more effectively. In this review, we summarize the five "A" stages (adhesion, amplification, alienation, aging and allocation) of biofilm formation and mechanisms through which they protect the internal bacteria. Aimed at the characteristics of biofilms, we emphasize the design "THAT" principles (targeting, hacking, adhering and transport) of nanomedicines in their interactions with biofilms and internal bacteria. Furthermore, recent progresses in multimodal antibacterial nanomedicines, including biofilms disruption and bactericidal activity, and the types of currently available antibiofilm nanomedicines contained organic and inorganic nanomedicines are outlined and highlighted their potential applications in the development of preclinical research. Last but not least, we offer a perspective for the effectiveness of nanomedicines designed to address AMR and challenges associated with their clinical translation.

Multifunctional polydopamine-carboxymethyl cellulose composite gels with Ag/AgCl/ZnO heterojunction to enhance sunlight-responsive photocatalytic activity

Carboxymethyl cellulose (CMC) gel is an ideal substrate for supporting sunlight responsive photocatalysts, but the photocatalytic disinfection activity decreased due to the light-shielding effect of the gel. In order to enhance the formation of active oxygen species, polydopamine (PDA) was introduced in CMC gels to function as an intermediate to connect two semiconductors inside the gels via its quinhydrone charge-transfer complexation. CMC/PDA gel with a double-network was formed via chemical crosslinking and reversible hydrogen bonding between prepolymerized PDA and CMC, then Ag/AgCl, ZnO and Ag/AgCl/ZnO photocatalysts were formed in situ in CMC/PDA gel, respectively. Ag/AgCl/ZnO heterojunction loaded composite gel displayed a remarkable photocatalytic degradation activity, with a weight ratio of the degraded methyl orange divided by composite gels up to 0.00090 under sunlight irradiation for 30 min. Ag/AgCl/ZnO loaded gel presented the bactericidal rate of 99.9 % against E. coli and 99.8 % against S. aureus. The inhibition zone of Ag/AgCl/ZnO loaded composite gel with dopamine mass of 100 mg increased under 6 h of sunlight compared with 24 h in dark against both E. coli and S. aureus. The biocompatible Ag/AgCl/ZnO loaded composite gel with pH-responsive swelling property and sunlight-responsive antibacterial activity promised to broaden the application of CMC-based antibacterial gels.

Effect of pore structure in bismuth metal-organic framework nanorod derivatives on adsorption and organic pollutant degradation

This study explores the synthesis, characterization, and photocatalytic properties of bismuth metal-organic framework (Bi-MOF) nanorods and their derivatives such as Ag/Bi-MOF and Ag/Bi2O3. Bi-MOF nanorods exhibit significant photocatalytic activity under visible light, with the addition of silver (Ag) enhancing electron-hole pair separation and reducing their recombination. This leads to improved photocatalytic performance, particularly in the degradation of organic pollutants such as Rhodamine B (RhB) and Methylene Blue (MB). The results show that Bi-MOF and its derivatives demonstrate excellent chemical stability and high performance in photocatalytic applications, even when subjected to high temperatures and tested across a wide pH range. The large surface area and microporous structure facilitate selective adsorption of small organic molecules like MB. The pores and large surface area not only provide numerous active sites but also enhance the interaction between reactants and the catalyst surface, improving photocatalytic efficiency. Bi-MOF and its derivatives perform optimally across a broad pH range, from acidic to alkaline environments, where strong oxidizing hydroxyl radicals (·OH) are easily formed, aiding in the effective degradation of organic compounds. The study also shows that Bi-MOF and its derivatives can be reused multiple times without significant loss in performance. This research contributes to the development of advanced materials for environmental remediation, highlighting the potential of Bi-MOF-based nanocomposites in practical applications.

Chitosan/MgO NPs/CQDs bionanocomposite coating: Fabrication, characterization and determination of antimicrobial efficacy

The development of new polymer nanocomposites or antibacterial coatings is crucial in combating drug-resistant infections, particularly bacterial infections. In this study, a new chitosan polymer based nanocomposite reinforced with magnesium oxide nanopowders and carbon quantum dots was fabricated by sol-gel technique and coated on 316 L stainless steel. In order to gaining the optimal amount of components to achieve the maximum antibacterial properties, the effect of concentration of nanocomposite components on its antibacterial properties was investigated. Crystal structure, microstructure, elemental dispersion, size distribution, chemical composition and morphology of nanocomposite and coating were characterized with various analyses. The obtained results exhibited that the carbon quantum dot and magnesium oxide nanopowders were distributed uniformly and without agglomeration in the chitosan matrix and created a uniform coating. The antibacterial properties of the synthesized samples against Staphylococcus aureus bacteria (gram positive) were evaluated using disk diffusion and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) antibacterial tests. The inhibition growth zone formed around the antibiotic and nanocomposite 25 mg/ml under dark and light was about 32 and 14, 11 mm, respectively. Also, MIC and MBC values for final nanocomposite were 62.5 and 125 μg/ml, respectively.

Advanced photocatalytic disinfection mechanisms and their challenges

Currently, microbial contamination issues have globally brought out a huge health threat to human beings and animals. To be specific, microorganisms including bacteria and viruses display durable ecological toxicity and various diseases to aquatic organisms. In the past decade, the photocatalytic microorganism inactivation technique has attracted more and more concern owing to its green, low-cost, and sustainable process. A variety kinds of photocatalysts have been employed for killing microorganisms in the natural environment. However, two predominant shortcomings including low activity of photocatalysts and diverse impacts of water characteristics are still displayed in the current photocatalytic disinfection system. So far, various strategies to improve the inherent activity of photocatalysts. Other than the modification of photocatalysts, the optimization of environments of water bodies has been also conducted to enhance microorganisms inactivation. In this mini-review, we outlined the recent progress in photocatalytic sterilization of microorganisms. Meanwhile, the relevant methods of photocatalyst modification and the influences of water body characteristics on disinfection ability were thoroughly elaborated. More importantly, the relationships between strategies for constructing advanced photocatalytic microorganism inactivation systems and improved performance were correlated. Finally, the perspectives on the prospects and challenges of photocatalytic disinfection were presented. We sincerely hope that this critical mini-review can inspire some new concepts and ideas in designing advanced photocatalytic disinfection systems.

In situ construction of Ag/Bi2O3/Bi5O7I heterojunction with Bi-MOF for enhance the photocatalytic efficiency of bisphenol A by facet-coupling and s-scheme structure

In this study, Ag/Bi2O3/Bi5O7I with s-scheme heterostructures were successfully synthesized in situ by nano-silver modification of CUA-17 and halogenated hydrolysis.The growth rate of Bi2O3 crystals was effectively controlled by adjusting the doping amount of Ag, resulting in the formation of a facet-coupling heterojunctions. Through the investigation of the microstructure and compositional of catalysts, it has been confirmed that an intimate facet coupling between the Bi2O3 (120) facet and the Bi5O7I (312) facet, which provides robust support for charge transfer. Under visible light irradiation, the AgBOI.3 heterojunction photocatalyst exhibited an outstanding degradation rate of 98.2% for Bisphenol A (BPA) with excellent stability. Further characterization using optical, electrochemical, impedance spectroscopy, and electron spin resonance techniques revealed significantly enhanced efficiency in photogenerated charge separation and transfer, and confirming the s-scheme structure of the photocatalyst. Density functional theory calculations was employed to elucidate the mechanism of BPA degradation and the degradation pathway of BPA was investigated by LC-MS. Finally, the toxicity of the degradation intermediates was evaluated using T.E.S.T software.

Chitosan synergizes with bismuth-based metal-organic frameworks to construct double S-type heterojunctions for enhancing photocatalytic antimicrobial activity

In recent years, photocatalytic technology has been introduced to develop a new kind antimicrobial agents fighting antibiotic abusing and related drug resistance. The efforts have focused on non-precious metal photocatalysts along with green additives. In the present work, a novel bis-S heterojunctions based on the coupling of polysaccharide (CS) and bismuth-based MOF (CAU-17) s synthesized through a two-step method involving amidation reaction under mild conditions. The as prepared photocatalyst literally extended the light response to the near-infrared region. Owing to its double S-type heterostructure, the lifetime of the photocarriers is significantly prolonged and the redox capacity are enhanced. As a result, the as prepared photocatalyst indicated inhibition up to 99.9 % under 20 min of light exposure against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria as well as drug-resistant bacteria (MRSA). The outstanding photocatalytic performance is attributed to the effective charge separation and migration due to the unique double S heterostructure. Such a double S heterostructure was confirmed through transient photocurrent response, electrochemical impedance spectroscopy tests and electron spin resonance measurements. The present work provides a basis for the simple synthesis of high-performance heterojunction photocatalytic inhibitors, which extends the application of CAU-17 in environmental disinfection and wastewater purification.

Photocatalytic antibacterial agents based on inorganic semiconductor nanomaterials: a review

Microbial contamination and antibiotic pollution have threatened public health and it is important to develop a rapid and safe sterilization strategy. Among various disinfection strategies, photocatalytic antibacterial methods have drawn increasing attention due to their efficient disinfection performances and environment-friendly properties. Although there are some reviews about bacterial disinfection, specific reviews on photocatalysis focused on inorganic semiconductor nanomaterials are rarely reported. Herein, we present a systematic summary of recent disinfection developments based on inorganic nanomaterials (including metal oxides, sulfides, phosphides, carbon materials, and corresponding heterostructures) over the past five years. Moreover, key factors and challenges for inorganic nanomaterial-based photocatalytic disinfection are outlined, which holds great potential for future photocatalytic antibacterial applications.