Betaine microgel preparation from 2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide and its use as a catalyst system

Designing of moringa gum-zwitterionic copolymer structure through supra-molecular and covalent interactions for biomedical uses

Recently, functional materials derived from carbohydrate polymers have gained significant attention for their clinical uses due to their inherent bioactivity and biocompatibility. Therefore, the primary focus of the present research was to design bioactive moringa gum (MOGUM)-based hydrogels through covalent and supra-molecular interactions for use in biomedical applications. The copolymeric hydrogels were prepared by crosslinking of zwitterionic polymers of 2-(methacryloyloxy)ethyl] dimethyl-(3-sulfoproyl) ammonium hydroxide (MEDSAH) and carbopol (CP) onto gum for their applications in hydrogel wound dressings (HWDR) and drug delivery (DD). These copolymers were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), solid state 13C nuclear magnetic resonance (13C NMR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. Release of the encapsulated drug (minocycline) from hydrogels exhibited non-Fickian mechanism and the release profile was best described by zero order kinetic model. These HWDR were found to be blood compatible, mechanically stable, permeable to H2O and O2. The HWDR revealed muco-adhesiveness and required a detachment force 153.00 ± 6.00 mN for their separation from mucosal membrane. The antioxidant activity of dressing materials revealed 76.57 ± 1.91 % scavenging during the DPPH assay. The minocycline encapsulated HWDR elucidated antibacterial activity against P. aeruginosa, E. coli & S. aureus. These findings suggest that these hydrogels hold significant potential for application in DD systems.

Thermo-responsive/anti-biofouling chitosan hydrogel beads in situ decorated with silver nanoparticles for water disinfection

The development of a sustainable and eco-friendly silver-based hybrid nanocomposite for safe and efficient point-of-use (POU) water disinfection remains a challenge. Herein, a simple and facile approach was proposed for the in situ immobilization of silver nanoparticles (AgNPs) on chitosan-g-poly (sulfobetaine methacrylate) (CS-g-PSBMA) hydrogel beads, which have been achieved via graft copolymerization of sulfobetaine methacrylate along the chitosan chains followed by a drop method. The AgNPs-decorated CS-g-PSBMA hydrogel beads were characterized and their bactericidal efficacy towards Escherichia coli was evaluated concurrently with their anti-biofouling behaviors. The results indicated that the grafted PSBMA hydrogels on CS would not only enhance the immobilization of more AgNPs (122.63 mg/g material), but also restricted the silver release (only 0.015 % after the 14th day of incubation), which surpassed numerous other AgNPs-based nanocomposites for water disinfection. Moreover, the release of silver can be modulated by altering the temperature due to the thermosensitivity of PSBMA, and the maximum concentration of silver leaching in the effluent was 33.1-52.3 μg/L at 25-60 °C. Importantly, the synthesized AgNPs-based CS-g-PSBMA can exert both exceptional bactericidal and superior anti-biofouling capabilities as well as reusability features, indicating sustained antibacterial effectiveness and significant potential for practical applications in water disinfection.

Recent advances of zwitterionic based topological polymers for biomedical applications

Zwitterionic polymers, comprising hydrophilic anionic and cationic groups with the same total number of positive and negative charges on the same monomer residue, have received increasing attention due to their...

Multiscale simulations of polyzwitterions in aqueous bulk solutions and brush array configurations

Zwitterionic polymers are very promising candidates for antifouling materials that exhibit high chemical stability as compared to polyethylene glycol-based systems. A number of simulation and experimental studies have emerged over recent years for the investigation of sulfobetaine-based zwitterionic polymers. Investigating the structural and thermodynamic properties of such polymers requires access to broad time and length regimes, thus necessitating the development of multiscale simulation strategies. The present article advocates a mesoscopic dissipative particle dynamics (DPD) model capable of addressing a wide range of time and length scales. The mesoscopic force field was developed hand-in-hand with atomistic simulations based on the OPLS force field through a bottom-up parameterization procedure that matches the atomistically calculated strand-length, strand-angle and pair distribution functions. The DPD model is validated against atomistic simulations conducted in this work, and against relevant atomistic simulation studies, theoretical predictions and experimental correlations from the literature. Properties examined include the conformations of SPE polymers in dilute bulk aqueous solution, the density profile and thickness of brush arrays as functions of the grafting density and chain length. In addition, we compute the potential of mean force of an approaching hydrophilic or hydrophobic foulant via umbrella sampling as a function of its position relative to the poly-zwitterion-covered surface. The aforementioned observables lead to important insights regarding the conformational tendencies of grafted polyzwitterions and their antifouling properties.

Zwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications

Zwitterionic polymers by virtue of their unique chemical and physical attributes have attracted researchers in recent years. The simultaneous presence of positive and negative charges in the same repeat unit renders them of various interesting properties such as superhydrophilicity, which has significantly broadened their scope for being used in different applications. Among polyzwitterions of different architectures, micro- and/or nano-gels have started receiving attention only until recently. These 3D cross-linked colloidal structures show peculiar characteristics in context to their solution properties, which are attributable either to the comonomers present or the presence of different electrolytes and biological specimens. In this review, a concise yet detailed account is provided of the different synthetic techniques and application domains of zwitterion-based micro- and/or nanogels that have been explored in recent years. Here, the focus is kept solely on the "polybetaines," which have garnered maximum research interest and remain the extensively studied polyzwitterions in literature. While their vast application potential in the biomedical sector is being detailed here, some other areas of scope such as using them as microreactors for the synthesis of metal nanoparticles or making smart membranes for water-treatment are discussed in this minireview as well.

Flow-Through Catalytic Reactors Based on Metal Nanoparticles Immobilized within Porous Polymeric Gels and Surfaces/Hollows of Polymeric Membranes

State-of-the-art of flow-through catalytic reactors based on metal nanoparticles immobilized within the pores of nano-, micro- and macrosized polymeric gels and in the surface or hollow of polymeric membranes is discussed in this mini-review. The unique advantages of continuous flow-through nanocatalysis over the traditional batch-type analog are high activity, selectivity, productivity, recyclability, continuous operation, and purity of reaction products etc. The methods of fabrication of polymeric carriers and immobilization technique for metal nanoparticles on the surface of porous or hollow structures are considered. Several catalytic model reactions comprising of hydrolysis, decomposition, hydrogenation, oxidation, Suzuki coupling and enzymatic reactions in the flow system are exemplified. Realization of “on-off” switching mechanism for regulation of the rate of catalytic process through controlling the mass transfers of reactants in liquid media with the help of stimuli-responsive polymers is demonstrated. Comparative analysis of the efficiency of different flow-through catalytic reactors for various reactions is also surveyed.

Stimuli responsive microgel containing silver nanoparticles with tunable optical and catalytic properties

In this work, poly (vinylcaprolactam-co-itaconic acid) microgel was prepared by free radical polymerization. Silver nanoparticles were prepared in synthesized microgel networks by in situ reduction of Ag+ ions, loaded in microgel from aqueous solution of AgNO3. The prepared microgel was characterized by Fourier transformation infra-red spectroscopy, UV-Visible spectroscopy, fluorescence spectroscopy, X-ray diffraction, laser light scattering, thermal gravimetric analysis, differential scanning calorimetry and transmission electron microscopy. Swelling behavior of microgel was studied as a function of temperature and pH. The microgel was found to be in swollen state at low temperature and basic medium while in collapsed state at high temperature and acidic medium. A slight decrease in swelling capacity of microgel was observed after the fabrication of silver nanoparticles. A decrease in the emission intensity and a red shift in surface plasmon resonance wavelength of silver nanoparticles was observed with pH induced swelling of microgel. Catalytic activity of the composite microgel was studied by using them as catalyst for the reduction of 4-nitrophenol, methyl orange and methylene blue. Effects of temperature and catalyst dose were also investigated. The reduction rates of 4-NP, MB and MO were found to be 0.859, 0.0528 and 0.167 min−1, respectively. The change in catalytic performance and shift in absorption maxima and emission intensity of composite microgel as a function of temperature and pH reveals that this system has potential to be used as tunable catalyst and optical sensor.

Facile synthesis of hydrogel-nickel nanoparticle composites and their applications in adsorption and catalysis

Homopolymer bulk hydrogel of methacrylic acid was synthesized through a new single-step facile rout and used as a template for the fabrication of nickel (Ni) nanoparticles and as adsorbent to remove methylene blue (MB) and Rhodamine-6G (Rh-6G) from water. The Ni nanoparticles containing composite hydrogel was applied as catalyst for the degradation of a nitro compound. The carboxylic groups acted as highly efficient adsorption sites and their high degree was responsible for the removal of huge amounts of MB and Rh-6G from water. The maximum adsorption capacity of poly (methacrylic acid) hydrogel was 685 mg g−1 for MB and 1571 mg g−1 for Rh-6G. The adsorption data of MB was best fitted with Langmuir adsorption isotherm while that of Rh-6G with Temkin adsorption isotherm. Catalytic property of prepared hydrogel integrated with Ni nanoparticles was evaluated by using it as a catalyst for the degradation of 4-nitrophenol (4-NP). The apparent rate constant (k app) observed in this study for the reduction of 4-NP was as high as 0.038 min−1. It was found that this catalyst system can be used repetitively with a slight decrease in catalytic activity.

Reduction of Nitro Compounds Using 3d-Non-Noble Metal Catalysts

The reduction of nitro compounds to the corresponding amines is one of the most utilized catalytic processes in the fine and bulk chemical industry. The latest development of catalysts with cheap metals like Fe, Co, Ni, and Cu has led to their tremendous achievements over the last years prompting their greater application as "standard" catalysts. In this review, we will comprehensively discuss the use of homogeneous and heterogeneous catalysts based on non-noble 3d-metals for the reduction of nitro compounds using various reductants. The different systems will be revised considering both the catalytic performances and synthetic aspects highlighting also their advantages and disadvantages.

Simultaneous catalytic degradation/reduction of multiple organic compounds by modifiable p(methacrylic acid-co-acrylonitrile)–M (M: Cu, Co) microgel catalyst composites

The reactants easily diffuse into a microgel network, adsorb at the surface of catalyst nanoparticles and reduce in the presence of reducing agents.