Copolymers of Maleic Acid and Their Amphiphilic Derivatives as Stabilizers of Silver Nanoparticles

Hydrophilization and Functionalization of Fullerene C60 with Maleic Acid Copolymers by Forming a Non-Covalent Complex

In this study, we report an easy approach for the production of aqueous dispersions of C60 fullerene with good stability. Maleic acid copolymers, poly(styrene-alt-maleic acid) (SM), poly(N-vinyl-2-pyrrolidone-alt-maleic acid) (VM) and poly(ethylene-alt-maleic acid) (EM) were used to stabilize C60 fullerene molecules in an aqueous environment by forming non-covalent complexes. Polymer conjugates were prepared by mixing a solution of fullerene in N-methylpyrrolidone (NMP) with an aqueous solution of the copolymer, followed by exhaustive dialysis against water. The molar ratios of maleic acid residues in the copolymer and C60 were 5/1 for SM and VM and 10/1 for EM. The volume ratio of NMP and water used was 1:1.2-1.6. Water-soluble complexes (composites) dried lyophilically retained solubility in NMP and water but were practically insoluble in non-polar solvents. The optical and physical properties of the preparations were characterized by UV-Vis spectroscopy, FTIR, DLS, TGA and XPS. The average diameter of the composites in water was 120-200 nm, and the ξ-potential ranged from -16 to -20 mV. The bactericidal properties of the obtained nanostructures were studied. Toxic reagents and time-consuming procedures were not used in the preparation of water-soluble C60 nanocomposites stabilized by the proposed copolymers.

Investigation of the Binding of Lectins with Polymer Glycoconjugates and the Glycoconjugates Containing Silver Nanoparticles by Means of Optical Spectroscopy and Light Scattering

The synthesis of glycoconjugates, lectin-specific polymers containing a carbohydrate ligand (spacered residue of N-acetyl-D-glucosamine, β-N-Gly-GlcNAc) has been carried out. Glyconanoparticles (glycol-NPs) containing a label detectable by means of spectrophotometry, silver nanoparticles, have been prepared on the basis of the glycoconjugates. Copolymers of maleic anhydride with ethylene or N-vinylpyrrolidone have been used as a carrier to introduce the carbohydrate ligand and a stabilizer of silver nanoparticles. Solutions of the glycoconjugates and the silver glyconanoparticles have been characterized by means of light scattering, UV-visible spectroscopy, and TEM. The interaction of the obtained glycoconjugates and silver glyconanoparticles with N-acetyl-D-glucosamine-specific lectins of Solanum tuberosum agglutinin (STA) and wheat germ agglutinin (WGA) has been investigated by means of light scattering and UV-visible spectro-scopy. The data obtained via these physical methods using the carbohydrate-containing derivatives labeled with silver nanoparticles have been in agreement. It has been shown that the glycoconjugates and silver glyconanoparticles based on more hydrophilic copolymer of maleic acid with N-vinylpyrrolidone are more sensitive than the respective systems based on more hydrophobic copolymer of maleic acid with ethylene. It has been also shown that the considered systems are more sensitive to the STA lectin than to the WGA lectin. The silver glyconanoparticles have allowed more accurate and reliable detection of the lectins by means of light scattering, as compared to the glycopolymer.

Silver nanoparticles doped with silver cations and stabilized with maleic acid copolymers: specific structure and antimicrobial properties

The specificity of the structure of polymer complexes of silver nanoparticles and silver cations is revealed, and the additive antimicrobial effect of the system components is shown.

Synthesis of Functional Silver Nanoparticles and Microparticles with Modifiers and Evaluation of Their Antimicrobial, Anticancer, and Antioxidant Activity

An accumulating body of evidence reports the synthesis and biomedical applications of silver nanoparticles. However, the studies regarding the use of maleic acid and citric acid in the synthesis of nano-sized silver particles (AgNPs) and micro-sized silver particles (AgMPs) as well as their antibacterial, antifungal, and anticancer activities have not been reported. In the current study, we synthesized AgNPs and AgMPs using maleic acid and citric acid as capping agents and have characterized them by UV-Vis, energy-dispersive X-Ray spectroscopy (EDS), X-Ray diffraction (XRD), and scanning electron microscope (SEM) analysis. The capped silver particles were examined for their antimicrobial activity and cytotoxicity against bacteria, fungi, and brine shrimp. Additionally, the anticancer activity of these particles was tested against human breast and liver cancer cell lines. The free radical scavenging activity of capped silver particles was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. SEM analysis revealed a round plate-like morphology of maleic acid capped particles with an average size of 39 ± 4 nm, whereas citric acid capped particles display flower-shaped morphology with rough surfaces and an average size of 250 ± 5 nm. The uncapped AgMPs were hexagonal with 500 ± 4 nm size. EDS and XRD analysis confirmed the presence of Ag and face-centered cubic crystalline nature, respectively. Functionally, capped silver particles exhibited antibacterial activity against Gram-positive (Staphylococcus aureus, Bacillus subtilis, and Micrococcus luteus) and Gram-negative bacteria (Salmonella setubal, Enterobacter aerogenes, and Agrobacterium tumefaciens). The bactericidal activity was more active against Gram-negative bacteria with minimum inhibitory concentration (MIC) as low as 5 ppm as compared to 25 ppm for Gram-positive. Similarly, the silver particles demonstrated antifungal activity by inhibiting the growth of five fungal strains (Mucor species, Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, and Fusarium solani) up to 50% at the concentration of 500 ppm. Additionally, these particles showed substantial toxicity against brine shrimp and also significantly inhibited the proliferation of breast cancer (MCF7) and liver cancer (HePG2) cell lines (IC₅₀ 8.9-18.56 µM). Uncapped AgMPs were less effective, inhibiting only the proliferation of MCF7 cells with IC₅₀ 46.54 µM. Besides cytotoxicity, these particles acted as potential antioxidants, showing free radical scavenging up to 74.4% in a concentration-dependent manner. Taken together, our results showed that the modifiers affect the shape and size of silver particles and may, in part, contribute to the antimicrobial and antioxidant activity of silver particles. However, the contribution of maleic acid and citric acid in enhancing the antimicrobial, anticancer, and antioxidant potential independent of silver nano and microparticles needs to be studied further. In vivo experiments may determine the therapeutic effectiveness of silver particles capped with these modifiers.

Silver nanoparticles impregnated chitosan layered carbon nanotube as sensor interface for electrochemical detection of clopidogrel in-vitro

Continuous periodical monitoring of clopidogrel in physiological body fluids is indispensable in medical diagnosis of heart ailments and cardiovascular diseases. A highly sensitive electrochemical sensor has been fabricated with silver nanoparticles embedded chitosan-carbon nanotube hybrid composite (AgChit-CNT) as sensor interface for detection of the important anti-platelet drug, clopidogrel (CLP). Synthesized AgChit-CNT nanocomposite is examined by x-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy for its chemical and structural characteristics. Crystalline silver nanoparticles of about 35 nm are well distributed in the composite and have formed continuous chain like linkages with CNTs all throughout. Electrochemical responses of the fabricated AgChit-CNT nanocomposite electrode for the determination of CLP have been examined by cyclic voltammetry and electrochemical impedance spectroscopy. The nanoAg patterned CNT nanocomposite interface acts as an excellent electron transfer mediator towards the oxidation of clopidogrel. Electrochemical determination of CLP was investigated by differential pulse voltammetry (DPV) and amperometric analysis under optimized conditions. The limit of detection by DPV and amperometry were 30 nM and 10 nM, respectively, and the time of the analysis is as low as 10 s. Practical applicability for determination in artificially prepared urine and pharmaceutical formulation has been examined with good recovery limits of 95.2 to 102.6%.

Adsorption of Maleic Acid Monomer on the Surface of Hydroxyapatite and TiO2: A Pathway toward Biomaterial Composites

Poly(styrene- alt-maleic acid) adsorption on hydroxyapatite and TiO₂ (rutile) was studied using experimental techniques and complemented by ab initio simulations of adsorption of a maleic acid segment as a subunit of the copolymer. Ab initio calculations suggest that the maleic acid segment forms a strong covalent bonding to the TiO₂ and hydroxyapatite surfaces. If compared to vacuum, the presence of a solvent significantly reduces the adsorption strength as the polarity of the solvent increases. The results of first-principles calculations are confirmed by the experimental measurements. We found that the adsorbed poly(styrene- alt-maleic acid) allowed efficient dispersion of rutile and formation of films by the electrophoretic deposition. Moreover, rutile can be codispersed and codeposited with hydroxyapatite to form composite films. The coatings showed an enhanced corrosion protection of metallic implants in simulated body fluid solutions, which opens new avenues for the synthesis, dispersion, and colloidal processing of advanced composite materials for biomedical applications.

Rambutan peels promoted biomimetic synthesis of bioinspired zinc oxide nanochains for biomedical applications

A naturally occurring rambutan peel waste was employed to synthesis bioinspired zinc oxide nanochains. Rambutan peels has the ability of ligating zinc ions as a natural ligation agent resulting in zinc oxide nanochains formation due to its extended polyphenolic system over incubation period. Successful formation of zinc oxide nanochains was confirmed employing transmission electron microscopy studies. About 60% and ∼40% cell viability was lost and 50% and 10% morphological change was observed in 7 and 4 days incubated ZnO treated cells compared with control. Moreover, 50% and 55% of cell death was observed at 24 and 48 h incubation with 7 days treated ZnO cells and hence alters and disturbs the growth of cancer cells and could be used for liver cancer cell treatment.

Magnetic nanobeads decorated with silver nanoparticles as cytotoxic agents and photothermal probes

A versatile method for decorating magnetic nanobeads (being composite materials from polymers and superparamagnetic nanoparticles) with silver nanoparticles of 3-6 nm size is presented. Control over the silver nanoparticle coverage at the nanobead surface is achieved by changing the reaction parameters. Moreover, the silver-decorated magnetic nanobeads (Ag-MNBs) are studied with respect to their in vitro cytotoxicity on two distinct tumour cell lineages under different parameters, i.e., dose, incubation time, magnetic field applied during the culturing, silver ion leakage, and colloidal stability. It is found that enhanced magnetically mediated cellular uptake and silver ion leakage from the Ag-MNBs surface are the main factors which affect the toxicity of the Ag-MNBs and allow the half-maximal inhibitory dose of silver to be reduced to only 32 μg mL(-1) . Furthermore, a synergic cytotoxicity induced by photo-activation of silver nanoparticles was also found.

Ellagic acid promoted biomimetic synthesis of shape-controlled silver nanochains

In this work, ellagic acid (EA), a naturally occurring plant polyphenol, was utilized for the biomimetic synthesis of silver (Ag) nanoparticles, which over a period of time formed extended branched nanochains of hexagonal-shaped silver nanoparticles. It was found that EA not only has the capability of reducing silver ions, resulting in the formation of Ag nanoparticles, due to its extended polyphenolic system, but also appears to recognize and affect the Ag nanocrystal growth on the (111) face, leading to the formation of hexagon-shaped Ag nanocrystals. Initially, various Ag nanocrystal shapes were observed; however, over a longer period of time, a majority of hexagonal-shaped nanocrystals were formed. Although the exact mechanism of formation of the nanocrystals is not known, it appears that EA attaches to the silver nuclei, leading to lower surface energy of the (111) face. Further, the nanocrystals fuse together, forming interfaces among the aggregates, and, with time, those interfaces become lesser, and the nanoparticles merge together and share the same single crystallographic orientation, which leads to the formation of long elongated chains of hexagonal nanoparticles. This biomimetic approach may be developed as a green synthetic method to prepare building blocks with tunable properties for the development of nanodevices. Further, we explored the antibacterial properties and found that the tandem of EA-Ag nanochains substantially enhanced the antibacterial properties of both gram-positive and gram-negative bacteria compared to silver nanoparticles or EA alone. Additionally, the materials were also utilized for imaging of mammalian NRK (normal rat kidney) cells.

Aggregation and deposition of engineered nanomaterials in aquatic environments: role of physicochemical interactions

The ever-increasing use of engineered nanomaterials will lead to heightened levels of these materials in the environment. The present review aims to provide a comprehensive overview of current knowledge regarding nanoparticle transport and aggregation in aquatic environments. Nanoparticle aggregation and deposition behavior will dictate particle transport potential and thus the environmental fate and potential ecotoxicological impacts of these materials. In this review, colloidal forces governing nanoparticle deposition and aggregation are outlined. Essential equations used to assess particle-particle and particle-surface interactions, along with Hamaker constants for specific nanoparticles and the attributes exclusive to nanoscale particle interactions, are described. Theoretical and experimental approaches for evaluating nanoparticle aggregation and deposition are presented, and the major findings of laboratory studies examining these processes are also summarized. Finally, we describe some of the challenges encountered when attempting to quantify the transport of nanoparticles in aquatic environments.