Antibacterial and Antibiofilm Formation Activities of Pyridinium-Based Cationic Pillar[5]arene Against Pseudomonas aeruginosa

Volatile Organic Compounds Produced by a Deep-Sea Bacterium Efficiently Inhibit the Growth of Pseudomonas aeruginosa PAO1

The deep-sea bacterium Spongiibacter nanhainus CSC3.9 has significant inhibitory effects on agricultural pathogenic fungi and human pathogenic bacteria, especially Pseudomonas aeruginosa, the notorious multidrug-resistant pathogen affecting human public health. We demonstrate that the corresponding antibacterial agents against P. aeruginosa PAO1 are volatile organic compounds (VOCs, namely VOC-3.9). Our findings show that VOC-3.9 leads to the abnormal cell division of P. aeruginosa PAO1 by disordering the expression of several essential division proteins associated with septal peptidoglycan synthesis. VOC-3.9 hinders the biofilm formation process and promotes the biofilm dispersion process of P. aeruginosa PAO1 by affecting its quorum sensing systems. VOC-3.9 also weakens the iron uptake capability of P. aeruginosa PAO1, leading to reduced enzymatic activity associated with key metabolic processes, such as reactive oxygen species (ROS) scavenging. Overall, our study paves the way to developing antimicrobial compounds against drug-resistant bacteria by using volatile organic compounds.

Design, synthesis, and bioactivity evaluation of clindamycin derivatives against multidrug-resistant bacterial strains

Our research aims to reduce the bacterial resistance of clindamycin against Gram-positive bacteria and expand its range of bacterial susceptibility. First, we optimized the structure of clindamycin based on its structure-activity relationship. Second, we employed the fractional inhibitory concentration method to detect drugs suitable for combination with clindamycin derivatives. We then used a linker to connect the clindamycin derivatives with the identified combined therapy drugs. Finally, we tested antibacterial susceptibility testing and conducted in vitro bacterial inhibition activity assays to determine the compounds. with the highest efficacy. The results of our study show that we synthesized clindamycin propionate derivatives and clindamycin homo/heterodimer derivatives, which exhibited superior antibacterial activity compared to clindamycin and other antibiotics against both bacteria and fungi. In vitro bacteriostatic activity testing against four types of Gram-negative bacteria and one type of fungi revealed that all synthesized compounds had bacteriostatic effects at least 1000 times better than clindamycin and sulfonamides. The minimum inhibitory concentration (MIC) values for these compounds ranged from 0.25 to 0.0325 mM. Significantly, compound 5a demonstrated the most potent inhibitory activity against three distinct bacterial strains, displaying MIC values spanning from 0.0625 to 0.0325 mM. Furthermore, our calculations indicate that compound 5a is safe for cellular use. In conclusion, the synthesized compounds hold great promise in addressing bacterial antibiotic resistance.

Pillar[n]arenes in the Fight against Biofilms: Current Developments and Future Perspectives

The global surge in bacterial infections, compounded by the alarming escalation of drug-resistant strains, has evolved into a critical public health crisis. Among the challenges posed, biofilms stand out due to their formidable resistance to conventional antibiotics. This review delves into the burgeoning potential of pillar[n]arenes, distinctive macrocyclic host molecules, as promising anti-biofilm agents. The review is structured into two main sections, each dedicated to exploring distinct facets of pillar[n]arene applications. The first section scrutinizes functionalized pillar[n]arenes with a particular emphasis on cationic derivatives. This analysis reveals their significant efficacy in inhibiting biofilm formation, underscoring the pivotal role of specific chemical attributes in combating microbial communities. The second section of the review shifts its focus to inclusion complexes, elucidating how pillar[n]arenes serve as encapsulation platforms for antibiotics. This encapsulation enhances the stability of antibiotics and enables a controlled release, thereby amplifying their antibacterial activity. The examination of inclusion complexes provides valuable insights into the potential synergy between pillar[n]arenes and traditional antibiotics, offering a novel avenue for overcoming biofilm resistance. This comprehensive review highlights the escalating global threat of bacterial infections and the urgent need for innovative strategies to counteract drug-resistant biofilms. The unique properties of pillar[n]arenes, both as functionalized molecules and as inclusion complex hosts, position them as promising candidates in the quest for effective anti-biofilm agents. The exploration of their distinct mechanisms opens new avenues for research and development in the ongoing battle against bacterial infections and biofilm-related health challenges.

Synthesizing Carbon Quantum Dots via Hydrothermal Reaction to Produce Efficient Antibacterial and Antibiofilm Nanomaterials

This study aimed to synthesize antibacterial carbon quantum dots (SP-CDs) from polyethyleneimine and spermidine via hydrothermal reaction. It was revealed that SP-CDs, with small size (7.18 nm) and high positive charge (+31.15 mV), had good fluorescence properties and lots of amino groups on their surfaces. The inhibition effect of SP-CDs on Staphylococcus aureus was better than that towards Escherichia coli, and the SP-CDs also had an inhibitory effect on multi-drug-resistant E. coli. The mechanism of SP-CDs shows that the SP-CDs were adsorbed on the surface of the negatively charged cell membrane through electrostatic interaction. SP-CDs can cause changes in membrane permeability, resulting in a shift of the cell membrane from order to disorder and the decomposition of chemical components, followed by the leakage of cell contents, resulting in bacterial death. SP-CDs can also significantly inhibit biofilm formation, destroy mature biofilms and reduce the number of living cells. Moreover, SP-CDs had negligible antimicrobial resistance even after 18 generations of treatment. This study proves that SP-CDs effectively inhibit the proliferation of foodborne pathogens, providing new feasibility for the application of carbon-based nanomaterials in the food industry.

Preparation, antioxidant and antibacterial activities of cryptate copper(II)/sulfonate chitosan complexes

In this work, we synthesized cryptate copper(II) followed by complexed with sulfonate chitosan (SCS). After characterization, the evaluation of the antioxidant properties of resulting complexes were carried out by 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH•), hydroxyl radical (•OH), and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+), while the antibacterial and biofilm inhibitory activity against Pseudomonas aeruginosa PAO1 (P. aeruginosa PAO1) were also investigated. According to the results, cryptate copper(II) exhibited the best antioxidant activity followed by cryptate copper(II)/SCS complexes, and SCS. Significant antibacterial activity of cryptate copper(II) against P. aeruginosa PAO1 was observed with the minimum inhibitory concentration of MIC value 12.50 μg/mL and minimum bactericidal concentration of MBC value 100.00 μg/mL, followed by cryptate copper(II)/SCS complexes and SCS. Cryptate copper(II) and cryptate copper(II)/SCS exhibited antibacterial activity which copper ions might enter the interior of cells, and the intracellular ions made the killed bacteria serve as an antibacterial agent showing a zombie effect. The copper ions complexed with cryptate and SCS rendering potential unlimited biological activities, might become one of the most popular research areas because of their unique coordination chemistry and their long-term biological activities.

A study on the antibacterial activity and antimicrobial resistance of pyridinium cationic pillar[5]arene against Staphylococcus aureus and Escherichia coli

An increasing number of infections caused by multidrug-resistant (MDR) Staphylococcus aureus （S. aureus） and Escherichia coli （E. coli） have severely affected human society. Thus, it is essential to develop an alternative type of antibacterial agents that has a different bacterial resistance mechanism from that of traditional antibiotics. After the synthesis and structural characterization of a cationic pillar[5]arene with pyridinium groups (PP5), the antibacterial and antibiofilm activities as well as its microbial resistance were systematically investigated. In-depth evaluation of biological studies revealed that PP5 was an active antibacterial agent, with surprising antibiofilm formation ability against E. coli and S. aureus. From the results of differential scanning calorimetry and transmission electron microscopy, it was concluded that the microbicidal activity of PP5 was due to the physical disruption of the pathogen's membrane and the subsequent leakage of cytoplasmic components, which could greatly reduce the rapid generation of resistance. It was presented that the easily available PP5 has high activity to inhibit Gram-positive and Gram-negative bacteria and/or their biofilms with low cytotoxicity. This pillar[5]arene derivative can be used as a good candidate for controlling drug-resistant pathogenic bacterial infections and treating MDR bacteria.

Self-Healing Thiolated Pillar[5]arene Films Containing Moxifloxacin Suppress the Development of Bacterial Biofilms

Polymer self-healing films containing fragments of pillar[5]arene were obtained for the first time using thiol/disulfide redox cross-linking. These films were characterized by thermogravimetric analysis and differential scanning calorimetry, FTIR spectroscopy, and electron microscopy. The films demonstrated the ability to self-heal through the action of atmospheric oxygen. Using UV–vis, 2D 1H-1H NOESY, and DOSY NMR spectroscopy, the pillar[5]arene was shown to form complexes with the antimicrobial drug moxifloxacin in a 2:1 composition (logK11 = 2.14 and logK12 = 6.20). Films containing moxifloxacin effectively reduced Staphylococcus aureus and Klebsiella pneumoniae biofilms formation on adhesive surfaces.

Biodegradable polycaprolactone metallopolymer-antibiotic bioconjugates containing phenylboronic acid and cobaltocenium for antimicrobial application

This paper reports antimicrobial metallopolymers containing biodegradable polycaprolactone as the backbone with boronic acid and cobaltocenium as the side chain. While boronic acid promotes interactions with bacterial cells via boronolectin with lipopolysaccharides, cationic cobaltocenium facilitates the unique complexation with anionic β-lactam antibiotics. The synergistic interactions in these metallopolymer-antibiotic bioconjugates were evidenced by re-sensitized efficacy of penicillin-G against four different Gram-negative bacteria (E. coli, P. vulgaris, P. aeruginosa and K. pneumoniae). The degradability of the polyester backbone was validated through tests under physiological pH (7.4) and acidic pH (5.5) or under enzymatic conditions. These metallopolymers exhibited time-dependent uptake and reduction of cobalt metals in different organs of mice via in vivo absorption, distribution, metabolism, and excretion (ADME) tests.