Synthesis, thermal and surface activity of cationic single chain metal hybrid surfactants and their interaction with microbes and proteins

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.

Advances and Perspective on Antimicrobial Nanomaterials for Biomedical Applications

Microbial infection and antibiotic resistance is recognized as a serious problem to society from both an economical perspective and a health concern. To tackle this problem, “nanotechnology,” a multidisciplinary field of research, has provided a plethora of nanomaterials for potential applications in the antimicrobial sector. This letter discusses how antimicrobial nanomaterials are shaping this challenging field and being evaluated as therapeutic and medication delivery agents. The recently designed smart antimicrobial surfaces with switchable features that displayed synergistic antibacterial action were also highlighted. To end, we provide the current scenario and future perspectives with regards to emerging antimicrobial nano-engineered materials and nanotechnology.

Photochemical OFF/ON Cytotoxicity Switching by Using a Photochromic Surfactant with Visible Light Irradiation

Photochemical switching of cytotoxicity by using spiropyran compounds with pyridinium and alkyl groups was investigated. The spiropyran compound, SP6, with a hexyl group as the alkyl group displayed negative photochromism, in which the hydrophilic open merocyanine form (MC form) was stable and isomerized to the hydrophobic closed spiro form (SP form) by visible light irradiation. Both MC and SP forms exhibited amphiphilicity because of the hydrophobic hexyl and hydrophilic pyridinium groups introduced. Cytotoxicity toward HeLa cells was observed for both MC and SP forms of SP6 at concentrations higher than the critical aggregation concentration of the isomers CAC_MC and CAC_SP (CAC_MC > CAC_SP), respectively. In contrast, cytotoxicity by SP6 was activated by visible light irradiation at concentrations between CAC_MC and CAC_SP; thus, photochemical switching of cytotoxicity from the OFF to ON state was achieved. Cytotoxicity was revealed to be caused by disruption of the cell membrane. The results provide an important step in developing novel next-generation photochemotherapy drugs.

Tuning the surface using palladium based metallosurfactant for hydrogen evolution reaction

Synthesis of a novel electrocatalyst for hydrogen evolution reaction (HER) is highly demanding for renewable energy production. This research reports the design and development of novel palladium based metallosurfactant (PdCPC(I)) that belongs to the unique class of inorganic-organic hybrid with striking structural features that are explored for the first time in the HER. The formation of the micelle, molecular orientation and surface characteristics of the metallosurfactant are calculated by conductivity and contact angle measurements. The reduction of palladium in metallomicelles during electrolysis accelerates the HER. Metallosurfactant makes the substrate hydrophilic, which in turn enhances the activity of the modified substrate. The 269 mV and 400 mV (vs RHE) overpotential is required to achieve the 10 mA cm^-2 of current density for PdCPC(I) and CPC, respectively. Tafel slope of PdCPC(I) is 57 mV dec^-1, which signifies that the reaction follows the Volmer- Heyrovsky mechanism in the presence of catalyst. The presence of the palladium in the core of the micelle is certified by ICPMS study. The present electrocatalyst also demonstrates 40 h of electrochemical durability. This work opens the doors toward the enhancement of HER, which fulfills the dreams for future energy resources.

Optimization and utilization of single chain metallocatanionic vesicles for antibacterial photodynamic therapy (aPDT) against E. coli

Currently, bacterial infection due to multi-drug-resistant bacteria is one of the foremost problems in public health. Photodynamic therapy plays a significant role against bacterial infection, without causing any side effects. But the photosensitizers are associated with many drawbacks, which lessen their photodynamic efficiency. In this context, the current study describes the synthesis of new metallocatanionic vesicles and employs them in photodynamic therapy. These vesicles were synthesized by using a single-chain cationic metallosurfactant (CuCPC I) and sodium oleate (NaOl) as an anionic component. These vesicles were characterized from conductivity, dynamic light scattering, zeta potential, field emission scanning electron microscopy, and confocal microscopy measurements. Methylene blue (MB) was used as a photosensitizer and its singlet oxygen quantum yield in the presence of these vesicles was determined by irradiating with 650 nm wavelength laser light. These vesicles play a dual-functional role, one helping in delivering the photosensitizer and the second doubling their singlet oxygen production capability due to the presence of metal ions. Antibacterial photodynamic therapy (aPDT) was studied against E. coli bacteria (Gram-negative bacteria). These vesicles also inherit their antibacterial activity and MB-encapsulated metallocatanionic vesicles on irradiation have shown 100% killing efficiency. In summary, we offer metallocatanionic vesicles prepared via a facile approach, which encapsulate a photosensitizer and can be used to combat E. coli infection through photodynamic therapy. We envisage that these synthesized metallocatanionic vesicles will provide a new modification to the catanionic mixture family and could be used for various applications in the future.

Investigating affordable cobalt based metallosurfactant as an efficient electrocatalyst for hydrogen evolution reaction

The implementation of hydrogen evolution reaction (HER) is an essential requirement of a stable electrocatalyst that competes for the performance of noble metals (Pt, Pd), especially in acidic conditions. This research reports the design and development of affordable cobalt (Co) based metallosurfactant (CoCPC(I)) which performs under acidic medium (0.5 N H₂SO₄) for HER. Such a fabricated catalyst is able to lower the cathodic potentials efficiently and exhibits 130 mV onset potential and Tafel slope of 104 mVdec^-1 that depicts the presence of Volmer-Heyrovsky mechanism. The results of the studies confirm that our synthesized metallosurfactant forms metallomicelles on the surface of electrode and surface remains stable even after the electrochemical cycle. Further, the surfactant protects the metal centre as an active site for a longer time via forming metallo-micelles which helps to sustain activity. These outcomes reveal the efficient mass and charge transfer capability of CoCPC(I) which results in faster charge transfer kinetics. Therefore, the utilization of Co based metallosurfactant can split water easily, cost-effectively, and without using hazardous chemicals. Our demonstrated technology seems suitable for industrial applications due to features of large-scale production possibilities.

Structural alteration of myoglobin with two homologous cationic surfactants and effect of β-cyclodextrin: multifaceted insight and molecular docking study

Structural alteration and regeneration of myoglobin.

Assessment of the aggregation and adsorption behavior of newly synthesized tetradecylpyridinium-based metallosurfactants and their interaction with bovine serum albumin

Tetradecylpyridinium (TP) based metallosurfactants, TP₂[MCl₄] (M = Mn, Co, Ni, Cu, Zn): synthesis, aggregation behavior and interaction with bovine serum albumin.

Metal-Biosurfactant Complexes Characterization: Binding, Self-Assembly and Interaction with Bovine Serum Albumin

Studies on the specific and nonspecific interactions of biosurfactants with proteins are broadly relevant given the potential applications of biosurfactant/protein systems in pharmaceutics and cosmetics. The aim of this study was to evaluate the interactions of divalent counterions with the biomolecular anionic biosurfactant surfactin-C₁₅ through molecular modeling, surface tension and dynamic light scattering (DLS), with a specific focus on its effects on biotherapeutic formulations. The conformational analysis based on a semi-empirical approach revealed that Cu²⁺ ions can be coordinated by three amide nitrogens belonging to the surfactin-C₁₅ cycle and one oxygen atom of the aspartic acid from the side chain of the lipopeptide. Backbone oxygen atoms mainly involve Zn²⁺, Ca²⁺ and Mg²⁺. Subsequently, the interactions between metal-coordinated lipopeptide complexes and bovine serum albumin (BSA) were extensively investigated by fluorescence spectroscopy and molecular docking analysis. Fluorescence results showed that metal-lipopeptide complexes interact with BSA through a static quenching mechanism. Molecular docking results indicate that the metal-lipopeptide complexes are stabilized by hydrogen bonding and van der Waals forces. The biosurfactant-protein interaction properties herein described are of significance for metal-based drug discovery hypothesizing that the association of divalent metal ions with surfactin allows its interaction with bacteria, fungi and cancer cell membranes with effects that are similar to those of the cationic peptide antibiotics.