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

Preparation of water-soluble imidazole-functionalized pillar[5]arenes: The activities of antibacterial and antioxidant, catalytic reduction of 4-nitrophenol

Macrocyclic supramolecular materials such as pillar[n]arenes play a prominent role in enhancing antibacterial activity through host-guest interactions. Herein, the water-soluble pillar[5]arene imidazole-1 and pillar[5]arene imidazole-2 were prepared, and their structure and chemical compositions were analyzed through multiple characterization methods. Afterward, the prepared imidazole-functionalized pillar[5]arenes were examined for antibacterial activity against Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and Salmonella typhimurium bacteria. Also, the antioxidant activities of the prepared imidazole-functionalized pillar[5]arenes were investigated using 2,2-Diphenyl-1-picrylhydrazyl. In addition, the catalytic activities of pillar[5]arene imidazole-1 and pillar[5]arene imidazole-2 by reduction of 4-nitrophenol were studied, indicating the catalytic reduction of 4-nitrophenol was 93.0 % for the pillar[5]arene imidazole-1 catalyst at 18 min. Comparison of the reactivity of pillar[5]arene imidazole-1 with that of pillar[5]arene imidazole-2 shows an increase in antibacterial and catalytic activity. This study summarized that using suitable catalysts, catalytic reduction aims to convert the most harmful and toxic organic compound 4-nitrophenol into non-toxic 4-aminophenol and popularize it in industry.

A half-natural origin approach for anticancer and antioxidant activities using sporopollenin and pillar[5]arene macroring

Sporopollenin is a natural biomacromolecule which can be found in the outer wall (exine) of spores or pollens that it can be performed with clever designing in a lot of innovative and scientific areas. In this paper, a novel sporopollenin reformed with a recently synthesized pillar[5]arene molecule were elucidated by FT-IR spectroscopy, TGA and SEM techniques. This study is the first report leading to a comprehensive investigation of the biological applications of a functionalized bio-microcapsule including antioxidant and anticancer properties. Two in vitro assays (DPPH and FRAP) were used to determine the antioxidant activities of sporopollenin and functionalized microcapsules. Furthermore, the anticancer activities of these microcapsules were tested on 2 different cancer cell lines (HT-29 and MCF-7), and a fibroblast cell line (L929) by the Alamar blue assay. Among the samples tested in the antioxidant capacity results, especially Sp-P[5] exhibited higher antioxidant capacity and stood out with IC50: 101.98 ± 4.32 μg/mL in DPPH assay and IC50: 87.97 ± 3.14 μg/mL in FRAP assay. Similar to the antioxidant result, Sp-P[5] bio-microcapsule had greater cell inhibition on HT-29 (IC50: 132.31 ± 5.38 μg/mL), MCF-7 (IC50: 107.30 ± 8.28 μg/mL), and L929 (IC50: 255.80 ± 4.91 μg/mL) cell lines than Sp and Sp-APTMS. The analysis results in the study show promise for the development of sporopollenin-based microcapsules to deliver and enhance the biological activity of compounds with therapeutic potential.

Design, Synthesis, and Biological Evaluation of Asymmetrical Disulfides Based on Garlic Extract as Pseudomonas aeruginosa pqs Quorum Sensing Inhibitors

Pseudomonas aeruginosa is a widely encountered bacterium linked to the deterioration of food products and represents a notable concern for public health safety. Disulfides serve as significant pharmacologically active scaffolds exhibiting antibacterial, antiviral, and anticancer properties; however, reports on their activity as quorum sensing inhibitors (QSIs) against P. aeruginosa are limited. In our work, asymmetrical disulfides were designed and synthesized, utilizing natural products, such as allicin, ajoene, diallyl disulfide (DADS), hordenine, and cinnamic acid, as lead compounds. By screening for lasB, rhlA, and pqsA promoter activity, two highly effective QSIs were identified. Compounds 7d and 4c show effectiveness in reducing the synthesis of different virulence factors, the creation of biofilms, and movement capabilities. Subsequent validation using the Galleria mellonella larvae model confirmed their robust in vivo efficacy. Moreover, their combination with antibiotics markedly augmented the antibacterial activity. Mechanism studies employed by transcriptome analysis, quantitative reverse transcription-PCR (qRT-PCR), surface plasmon resonance, and molecular docking demonstrate that compound 7d disrupts the quorum sensing system by interacting with PqsR. These findings suggest that our disulfide derivatives hold promise for treating P. aeruginosa infections.

Insight into the Antibacterial Activities of Pyridinium-Based Cationic Pillar[5]arene with Controllable Hydrophobic Chain Lengths against Staphylococcus aureus

The increasing number of infections caused by pathogenic bacteria has severely affected human society. More and more deaths were originated from Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) infection each year. The potential and excellent bacteriostatic activity and resistance to biofilm formation of pillar[5]arene with different functional groups attract important attention to further study the relationship between antimicrobial activity and cytotoxicity by varying the length of the hydrophobic chain, the number of positive charges, and the hydrophobic/hydrophilic balance of the molecule. In this work, four pyridinium-based cationic pillar[5]arene (PPs) with linear aliphatic chains of different lengths were synthesized. After systematic characterization, their inhibition activities against S. aureus were investigated. It revealed that PP6 (six methylenes in each linker) exhibited excellent inhibition activity against S. aureus (ATCC 6538) with a minimum inhibitory concentration (MIC) of 3.91 μg/mL and a minimum bactericidal concentration (MBC) of 62.50 μg/mL. As expected, PP6 exhibited the strongest antibiofilm ability and negligible antimicrobial resistance even after the 20th passage. A study of the action mechanism of selected PPs on the bacterial membrane depolarization and permeability by transmission electron microscopy (TEM) disclosed that the cationic pyridine groups of PPs inserted into the negatively charged bacterial membranes, thereby leading to membranolysis, cytoplasmic content leakage, and cell death. Importantly, PPs all showed very low toxicity to mammalian cells (L929 and HBZY-1), which provided a significant reference for the construction of hypotoxic antibacterial biomaterials for multiple drug-resistant bacteria based on pyridinium-grafted cationic macrocycles with controllable hydrophobic chain lengths.

Impact of Nutrient Starvation on Biofilm Formation in Pseudomonas aeruginosa: An Analysis of Growth, Adhesion, and Spatial Distribution

Objectives: This study investigates the impact of nutrient availability on the growth, adhesion, and biofilm formation of Pseudomonas aeruginosa ATCC 27853 under static conditions. Methods: Bacterial behaviour was evaluated in nutrient-rich Luria-Bertani (LB) broth and nutrient-limited M9 media, specifically lacking carbon (M9-C), nitrogen (M9-N), or phosphorus (M9-P). Bacterial adhesion was analysed microscopically during the transition from reversible to irreversible attachment (up to 120 min) and during biofilm production/maturation stages (up to 72 h). Results: Results demonstrated that LB and M9 media supported bacterial growth, whereas nutrient-starved conditions halted growth, with M9-C and M9-N inducing stationary phases and M9-P leading to cell death. Fractal analysis was employed to characterise the spatial distribution and complexity of bacterial adhesion patterns, revealing that nutrient-limited conditions affected both adhesion density and biofilm architecture, particularly in M9-C. In addition, live/dead staining confirmed a higher proportion of dead cells in M9-P over time (at 48 and 72 h). Conclusions: This study highlights how nutrient starvation influences biofilm formation and bacterial dispersion, offering insights into the survival strategies of P. aeruginosa in resource-limited environments. These findings should contribute to a better understanding of biofilm dynamics, with implications for managing biofilm-related infections and industrial biofouling.

Construction of a supramolecular antibacterial material based on water-soluble pillar[5]arene and a zwitterionic guest molecule

A new antibacterial system (HG) based on the host-guest chemistry between pillar[5]arene and a zwitterionic guest was fabricated. The HG complex displayed excellent antibacterial and biofilm formation inhibition and dispersal activities against E. coli, S. aureus and MRSA.

Pillararenes: a new frontier in antimicrobial therapy

Pillararenes have gained great interest among researchers in many fields due to their symmetric structure and facile functionalization. In this review, we summarize recent progress for pillararenes as antimicrobial agents, ranging from cationic pillararenes and peptide-modified pillararenes to sugar-functionalized pillararenes. Moreover, their structure-activity relationships are presented, and their mechanisms of action are discussed. As a state-of-the-art technology, their opportunities and outlook are also outlined in this emerging field. Overall, their potent inhibitory activity and high biocompatibility give them potential for the development of novel antimicrobial agents.

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.