Antimicrobial activities of polymeric quaternary ammonium salts from poly(glycidyl methacrylate)s

Synthesis and Characterization of Novel Azole Functionalized Poly(glycidyl methacrylate)s for Antibacterial and Anticandidal Activity

BACKGROUND

Presently, rise in the infectious diseases and subsequent development of drug resistance, is a global threat to human health. However, much efforts are being made by scientists, to develop novel antimicrobials, and also to improve the efficacy of available drugs, in order to combat the lifethreatening infections.

OBJECTIVE

Synthesis and characterization of azole functional polymer systems for antimicrobial applications.

MATERIALS AND METHODS

Poly(glycidyl methacrylate) (PGMA), was produced by free radical polymerization of the monomer, glycidyl methacrylate (GMA). Different azole functional PGMAs were produced, through chemical modification with imidazole (Im), 1H-1,2,4-triazole (Tri) and 3-amino-1,2,4-triazole (ATri), to get PGMA-Imi, PGMA-Tri and PGMA-ATri, respectively. The structure was confirmed by Fourier transform infrared spectroscopy (FT-IR), thermal properties were investigated by Thermogravimetric Analysis (TGA), and surface morphology was studied by scanning electron microscopy (SEM). Newly synthesized derivatives were further explored, for their antibacterial and anticandidal activities.

RESULTS

All the three synthesized and characterized derivatives, displayed a significant activity against the tested microorganisms. The minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC), recorded against Staphylococcus aureus (S. aureus), was 0.5 &1mg/ml for PGMA-Imi, followed by PGMA-ATri & PGMA-Tri, respectively, followed by E. coli with, 1 & 2 mg/ml, 4 & 8 mg/ml, 4& 8 mg/ml, respectively, whereas the maximum MIC & MFC was recorded against C. albicans i.e., 8 & 16 mg/ml, 4 & 8 mg/ml ,4 & 8 mg/ml for PGMA-ATri, PGMA-Tri, PGMA-Imi, respectively.

CONCLUSION

In the present work, we report on the state-of-the-art, azole functional polymer systems for antimicrobial applications. These findings suggest that the synthesized azole functional polymer films have antimicrobial properties, which could be potential candidates for coating applications in the biomedical and wastewater treatment field.

Cationic Organic Nanoaggregates as AIE Luminogens for Wash-Free Imaging of Bacteria and Broad-Spectrum Antimicrobial Application

The increase in the use of bactericides is a matter of grave concern and a serious threat to human health. The present situation demands rapid and efficient detection and elimination of antibiotic-resistant microbes. Herein, we report the synthesis of a simple C₃-symmetric molecular system (TGP) with an intrinsic positive charge through a single-step Schiff base condensation. In a water-dimethyl sulfoxide (DMSO) solvent mixture (80:20 v/v), TGP molecules self-aggregate to form spherical nanoparticles with a positively charged surface that displays efficient fluorescence owing to the aggregation-induced emission (AIE) phenomenon. Both Gram-positive and Gram-negative bacteria could be effectively detected through "turn-off" fluorescence spectroscopy as the electrostatic interaction of the resultant nanoaggregates with the negatively charged bacterial surface induced quenching of fluorescence of the nanoparticles. The fluorescence analysis and steady-state lifetime studies of TGP nanoparticles suggest that a nonradiative decay through photoinduced electron transfer from the nanoparticles to the bacterial surface leads to effective fluorescence quenching. Further, the TGP nanoaggregates demonstrate potent antimicrobial activity against microbes such as multidrug-resistant bacteria and fungi at a concentration as low as 74 μg/mL. A combination of factors including ionic surface characteristics of the nanoparticles for strong electrostatic binding on the bacterial surface followed by possible photoinduced electron transfer from the nanoaggregates to the bacterial membrane and enhanced oxidative stress in the membrane resulting from reactive oxygen species (ROS) generation is found accountable for the high antimicrobial activity of the TGP nanoparticles. The effective disruption of membrane integrity in both Gram-positive and Gram-negative bacteria upon interaction with the nanoaggregates can be observed from field emission scanning electron microscopy (FESEM) studies. The development of simple pathways for the molecular design of multifunctional broad-spectrum antimicrobial systems for rapid and real-time detection, wash-free imaging, and eradication of drug-resistant microbes might be crucial to combat pathogenic agents.

Green Accelerated Synthesis, Antimicrobial Activity and Seed Germination Test of Quaternary Ammonium Salts of 1,2-bis(4-pyridyl)ethane

A family of fifteen quaternary ammonium salts (QAs), bearing the 1,2-bis(4-pyridyl)ethane core, were obtained using for the first time two different green methods, such as microwave (MW) and ultrasounds (US) irradiation, with very good yields and in much shorter times compared to the classical method, and an assay on their antimicrobial action against Escherichia coli (E. coli) was carried out. While 12 to 24 hours were required for complete alkylation of 1,2-bis(4-pyridyl)ethane by reactive halogenated derivatives in anhydrous solvent under reflux conditions, MW and US irradiation reduced the reaction time and the desired products were achieved in a few min. One of the aims of this study was to evaluate the antibacterial potential of the synthesized QAs against pathogenic bacteria, along with their impact on germination activity of wheat seeds (Triticum aestivum L.). The antibacterial activity of the QAs against Escherichia coli was explored by determining the minimum inhibitory concentration (MIC). The MIC values varied from 0.312 to 2.5 mg/mL, highlighting the lowest values attained for the derivatives containing methoxy, chlorine and benzofurane functional groups. The viability of aerobic bacteria was determined with the Tetrazolium/Formazan Test, a method that was found to be the best alternative approach with respect to the difuzimetric method. Seeds of Triticum aestivum L. were used for the evaluation of the germination indicators, such as seed germination (SG), the relative seed germination (RSG), the relative radicle growth (RRG), and the seed germination index (GI). The toxicity studies of QAs 1, 4 and 7, at two different concentrations, showed no inhibitory effect on seed germination.

Multifunctional bacterial imaging and therapy systems

Advanced antibacterial materials are classified and introduced, and their applications in multimodal imaging and therapy are reviewed.

Quaternary ammonium-based biomedical materials: State-of-the-art, toxicological aspects and antimicrobial resistance

Microbial infections affect humans worldwide. Many quaternary ammonium compounds have been synthesized that are not only antibacterial, but also possess antifungal, antiviral and anti-matrix metalloproteinase capabilities. Incorporation of quaternary ammonium moieties into polymers represents one of the most promising strategies for preparation of antimicrobial biomaterials. Various polymerization techniques have been employed to prepare antimicrobial surfaces with quaternary ammonium functionalities; in particular, syntheses involving controlled radical polymerization techniques enable precise control over macromolecular structure, order and functionality. Although recent publications report exciting advances in the biomedical field, some of these technological developments have also been accompanied by potential toxicological and antimicrobial resistance challenges. Recent evidenced-based data on the biomedical applications of antimicrobial quaternary ammonium-containing biomaterials that are based on randomized human clinical trials, the golden standard in contemporary medicinal science, are included in the present review. This should help increase visibility, stimulate debates and spur conversations within a wider scientific community on the implications and plausibility for future developments of quaternary ammonium-based antimicrobial biomaterials.

Novel LDPE/halloysite nanotube films with sustained carvacrol release for broad-spectrum antimicrobial activity

Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature melt compounding with polyethylene, and resulting in highly potent antimicrobial films.

The effect of substituent, degree of acetylation and positioning of the cationic charge on the antibacterial activity of quaternary chitosan derivatives

A series of water-soluble cationic chitosan derivatives were prepared by chemoselective functionalization at the amino group of five different parent chitosans having varying degrees of acetylation and molecular weight. The quaternary moieties were introduced at different alkyl spacer lengths from the polymer backbone (C-0, C-2 and C-6) with the aid of 3,6-di-O-tert-butyldimethylsilyl protection of the chitosan backbone, thus allowing full (100%) substitution of the free amino groups. All of the derivatives were characterized using ¹H-NMR, ¹H-¹H COSY and FT-IR spectroscopy, while molecular weight was determined by GPC. Antibacterial activity was investigated against Gram positive S. aureus and Gram negative E. coli. The relationship between structure and activity/toxicity was defined, considering the effect of the cationic group’s structure and its distance from the polymer backbone, as well as the degree of acetylation within a molecular weight range of 7–23 kDa for the final compounds. The N,N,N-trimethyl chitosan with 100% quaternization showed the highest antibacterial activity with moderate cytotoxicity, while increasing the spacer length reduced the activity. Trimethylammoniumyl quaternary ammonium moieties contributed more to activity than 1-pyridiniumyl moieties. In general, no trend in the antibacterial activity of the compounds with increasing molecular weight or degree of acetylation up to 34% was observed.