Metallosurfactant aggregates: Structures, properties, and potentials for multifarious applications

Metallosurfactants offer important scientific and technological advances due to their novel interfacial properties. As a special class of structures formed by the integration of metal ions into amphiphilic surfactant molecules, these metal-based amphiphilic molecules possess both organometallic and surface chemistries. This review critically examines the structural transitions of metallosurfactants from micelle to vesicle upon metal coordination. The properties of a metallosurfactant can be changed by tuning the coordination between the metal ions and surfactants. The self-assembled behavior of surfactants can be controlled by selecting transition-metal ions that enhance their catalytic efficiency in environmental applications by applying a hydrogen evolution reaction or oxygen evolution reaction. We present the different scattering techniques available to examine the properties of metallosurfactants (e.g., size, shape, structure, and aggregation behavior). The utility of metallosurfactants in catalysis, the synthesis of nanoparticles, and biomedical applications (involving diagnostics and therapeutics) is also explored.

Self-Assembling Metallocomplexes of the Amphiphilic 1,4-Diazabicyclo[2.2.2]octane Derivative as a Platform for the Development of Nonplatinum Anticancer Drugs

New 1-cetyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide complexes with copper(II) bromide and lanthanum(III) nitrate were characterized using dynamic light scattering and transmission electron microscopy, with self-assembly and the morphological behavior elucidated. For the lanthanum(III) nitrate complex, the 3D crystal structure was characterized using X-ray diffractometry. These metallosurfactants were tested as antitumor agents, and a high cytotoxic effect comparable with doxorubicin was revealed against the M-HeLa and A-549 cell lines. Both complexes were 2 times more active toward the MCF-7 cell line than the breast cancer drug tamoxifen. The cytotoxic mechanism of complexes is assumed to be related to the induction of apoptosis through the mitochondrial pathway.

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

A series of novel palladium(II) and nickel(II) complexes of multifunctionalized aroylaminocarbo-N-thioylpyrrolinates were synthesized and characterized by analytical and spectroscopic techniques. The biological properties of the freshly prepared compounds were screened against S. aureus, B. subtilis, A. hydrophila, E. coli, and A. baumannii bacteria and antituberculosis activity against M. tuberculosis H37Rv strains. Also, the antifungal activity was studied against C. albicans, C. tropicalis, and C. glabrata standard strains. A deep conformational survey was monitored using DFT calculations with the aim to explain the importance of the final conformation in the biological experimental results.

High antimicrobial photodynamic activity of photosensitizer encapsulated dual-functional metallocatanionic vesicles against drug-resistant bacteria S. aureus

Developments in the field of photodynamic therapy (PDT) are being made by investigating appropriate photosensitizers (PSs) and enhancing the penetration effect of light by developing new nano-carriers. So, to boost the PDT effect, in the present work, new metallocatanionic vesicles were fabricated by a convenient, efficient, green and inexpensive method to encapsulate PSs and evaluate their antimicrobial PDT against the drug-resistant bacterium Staphylococcus aureus. They were prepared from a combination of a double-chained copper-based cationic metallosurfactant (CuCPCII) and an anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol OT or AOT). The surface charge, structure and ability to encapsulate oppositely charged photosensitizers are some crucial factors that need to be controlled for their effective utilization in PDT. In this approach, two of the fractions, one each from a cationic rich and anionic rich side, were selected to encapsulate cationic (methylene blue; MB) and anionic (rose bengal (RB)) PSs after characterization by SAXS, AFM, FESEM, DLS, and zeta-potential, and conductivity measurements. Afterwards, PDT was performed on S. aureus (a multidrug-resistant bacterium) by the colony forming unit (CFU) method using PS encapsulated metallocatanionic vesicles that demonstrated high bactericidal activity by using visible light (532 nm) and facilitated the generation of singlet oxygen. The singlet oxygen generation capability of both the PSs was enhanced under irradiation when encapsulated in metallocatanionic vesicles because the presence of metal accelerated the intersystem crossing of triplet oxygen to singlet oxygen. Furthermore, these studies reveal that the metallocatanionic vesicles have dual functionality i.e. encapsulate PSs and even show dark toxicity against S. aureus. To study the killing of S. aureus, bacterial DNA was extracted and its interactions and conformational changes in the presence of metallocatanionic vesicles were analyzed via., UV-Visible, and circular dichroism (CD) spectroscopy. Comet assay (single-cell gel-electrophoresis) demonstrated the DNA damage after PDT treatment in an individual cell. The bacterial DNA damage was more with the metallosurfactant rich 70 : 30 fraction than with the 30 : 70 fraction, in combination with RB under irradiation. This work provides a new metal hybrid smart material that possesses dual functionality and is prepared by an easy, economical and feasible procedure which resulted in enhanced PDT against a drug-resistant bacterium, thus, providing an alternative for antibacterial therapy.

Kinetics Analysis and Susceptibility Coefficient of the Pathogenic Bacteria by Titanium Dioxide and Zinc Oxide Nanoparticles

Purpose: The increase of bacterial resistance to common antibacterial agents is one of the major problems of health care systems and hospital infection control programs. In this study, antimicrobial activity of titanium dioxide (TiO₂ ) and zinc oxide (ZnO) nanoparticles (NPs) was investigated against E. coli, Salmonella enteritidis, Listeria monocytogenes, and Staphylococcus aureus pathogenic bacteria by determining sensitivity coefficient and kinetics of bacterial death. Methods: Antimicrobial tests were performed with ~10⁶ CFU/mL of each bacterium at baseline. At first, minimum inhibitory concentration (MIC) was concluded by the dilution method and then, death kinetic and susceptibility coefficient of NPs suspensions was determined at 0 to 360 min. treatment time. Results: The results of this study revealed that, the highest susceptibility was observed for L. monocytogenes (Z=0.025 mL/μg) to TiO₂ NPs, whereas the lowest susceptibility was obtained in the reaction of ZnO NPs with S. enteritidis (Z=0.0033 mL/μg). The process of bacterial death in NPs suspension was assumed to follow first-degree kinetic and the survival ratio of bacteria decreased by the increase in treatment time. An increase in the concentration of NPs was seen to enhance the bactericidal action. Conclusion: Results showed that L. monocytogenes had higher sensitivity compared to S. enteritidis. The results of this study also demonstrated that TiO₂ NPs have a strong antimicrobial effect in comparison with ZnO NPs and it could be employed to aid the control of pathogenic bacteria.

Comparative study of antidiabetic, bactericidal, and antitumor activities of MEL@AgNPs, MEL@ZnONPs, and Ag-ZnO/MEL/GA nanocomposites prepared by using MEL and gum arabic

In this study, a variety of nanocomposites, namely, MEL@AgNPs, MEL@ZnONPs, and Ag-ZnO/MEL/GA were biosynthesized using MEL and gum arabic to serve in biomedical applications. The synthesized nanocomposites were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and FTIR spectroscopy. The physicochemical properties and biomedical activities of the synthesized nanocomposites were investigated. The Ag-ZnO/MEL/GA nanocomposites showed greater antidiabetic activity against α-amylase and α-glucosidase, and higher antibacterial activity compared to MEL@AgNPs and MEL@ZnONPs. Furthermore, HepG2 cells were exposed to MEL@AgNPs, MEL@ZnONPs, and Ag-ZnO/MEL/GA nanocomposites for 24 h and their IC50 values were 63.25, 26.91 and 28.97 μg mL-1 (P < 0.05), respectively. According to this comparative study, it is apparent that the Ag-ZnO/MEL/GA nanocomposites have a great potential to serve as antitumor agents against HepG2, and antidiabetic and antibacterial agents.

Hydrophobic study of increasing alkyl chain length of platinum surfactant complexes: synthesis, characterization, micellization, thermodynamics, thermogravimetrics and surface morphology

This paper contains details on the synthesis, characterization, physicochemical properties and surface morphology of five supramolecular metallosurfactants (SMMSs).