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The failure of many antibiotics in the treatment of chronic infections caused by multidrug-resistant (MDR) bacteria necessitates the development of effective strategies to combat this global healthcare issue. Here, we report an antimicrobial platform based on the synergistic action between commercially available antibiotics and a potent synthetic antimicrobial polymer that consists of three key functionalities: low-fouling oligoethylene glycol, hydrophobic ethylhexyl, and cationic primary amine groups. Checkerboard assays with Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli demonstrated synergy between our synthetic antimicrobial polymer and two antibiotics, doxycycline and colistin. Coadministration of these compounds significantly improved the bacteriostatic efficacy especially against MDR P. aeruginosa strains PA32 and PA37, where the minimal inhibitory concentrations (MICs) of polymer and antibiotics were reduced by at least 4-fold. A synergistic killing activity was observed when the antimicrobial polymer was used in combination with doxycycline, killing >99.999% of planktonic and biofilm P. aeruginosa PAO1 upon a 20 min treatment at a polymer concentration of 128 μg mL -1 (4.6 μM) and doxycycline concentration of 64 μg mL -1 (133.1 μM). In addition, this synergistic combination reduced the rate of resistance development in P. aeruginosa compared to individual compounds and was also capable of reviving susceptibility to treatment in the resistant strains.

Cubosomes and hexosomes are soft particles of cubic and hexagonal phases, formedby self-assembled amphiphilic lipids. They have attracted great attention because ofapplications in drug delivery. Cubosomes and hexosomes have been produced at thenanoscale, exhibiting unique shapes and symmetries, but a better understandingof links between particle shapes and mesoscale structures is needed for controlledproduction and broader applications.In this thesis, a bottom-up method based on a precursor emulsion is developedto produce microscale cubosomes and hexosomes in a controlled way. Emulsiondroplets containing water, ethanol, the lipid glyceryl monooleate, and the desiredadditives are suspended in a yield stress fluid, and transform into liquid crystalswith solid-like rheology and controlled size and shape. Cubosomes are polyhedralparticles formed by growing facets on precursor droplets. Hexosomes are biconesand spinning tops with rotational symmetry. Small angle X-ray scattering confirmsthe particles are cubosomes and hexosomes, and links particle shapes to microstructures.Themicron-scale liquid crystalline particles provide a route to understandingthe effects on production of soft particles with ordered microstructure and uniqueshapes.The produced cubosomes and hexosomes are used as templates to polymerizevarious monomers and produce polymeric particles with unique micron-scalegeometric shapes. The amphiphilicity of particles allows incorporation of variousorganic monomers. Photopolymerization in the lipid templates creates polymerizedparticles preserving the shapes of cubosomes and hexosomes. Particleshapes are controlled by varying the structures and hydrophobicity of the monomers.Monomers also control the elasticity of the final particles produced.Although ultrasound is widely used to produce hexosomes in the top-downmethod, there are no direct studies of the process, and their effects on hexosomeproperties. We use high-speed microscopic imaging to directly observe b

The morphology of polymeric nanoparticles has been identified as one of the main factors affecting the drug loading capacities and biological processes in drug delivery applications. Therefore, controlling the morphology of nanoparticles becomes the main key to obtain specific morphology in order to improve the effectiveness of nanoparticles as drug carriers. In the present work, two alternative approaches to prepare polymeric nano-objects of various morphologies have been developed by using microporous membrane technology (Shirasu Porous Glass (SPG) membranes). Poly(oligoethylene glycol acrylate)-b-polystyrene (POEGA-b-PSt) diblock copolymers of different block lengths were prepared by RAFT polymerization. The first approach entails self-assembly of amphiphilic diblock copolymers employing an SPG-based system where the two liquids are miscible, i.e. an emulsion is not generated. Self-assembly using SPG membrane technology was conducted by first dissolving the polymer in tetrahydrofuran, followed by continuous passage of this copolymer solution through the membrane pores into the aqueous phase. In the second approach, polymeric nano-objects were generated through a solvent evaporation technique. The block copolymer is first dissolved in a water-immiscible organic solvent (chloroform), which is then emulsified with aqueous surfactant solution to obtain emulsion droplets. The solvent is subsequently removed by evaporation, resulting in an increase of the amphiphilic block copolymer concentration in the droplets. Results from both approaches indicate that it is possible to conveniently tune the nano-object morphology via the process parameters of pressure and pore size for a given formulation. The techniques developed were then employed to encapsulate hydrophobic drugs within various polymeric nano-objects. This study demonstrates the feasibility of using self-assembly of amphiphilic block copolymers in tandem with microporous membrane technology as a novel approach to

Graphene has received extensive attention since its discovery due to its unique structure and numerous excellent properties such as good mechanical property, excellent conductivity and high surface area. Three dimensional (3D) graphene based materials is interesting in the electrochemical energy storage as the 3D architectures assemble graphene nanosheets into macroscopic for practical applications providing fundamental frameworks with more “space” for loading inorganic nanoparticles or organic or biologic molecules. This thesis is based on the 3D graphene martial assembling from the graphene oxide (GO) which is a kind of graphene derivative with rich oxygen functional groups and good hydrophilic property.In the first part, we developed a green and simple method to form the reduced graphene oxide (rGO) hydrogel by mixing the GO and zinc nanoparticles dispersions under ambient conditions. The relative negative standard electrode potential of Zn to GO allowed the spontaneous formation of rGO-nanoZn hydrogel. Zn-free 3D rGO sponges were obtained by acid leaching of Zn species and followed by freeze drying. The result shows that such rGO hydrogel can be used as the material for the electrode of supercapacitor.Following this finding, we developed the compressed Zinc/graphene sponge where the Zinc nanoparticles are wrapped and stabilised inside the rGO sheets. Such material can be used as the dendrite-free electrode for the Zn metal batteries to improve the cycling stability of alkaline rechargeable zinc based batteries. In comparison with Zn plate and the mixture of Zn nanoparticles and carbon black, the compressed rGO-nanoZn sponge achieved better cycling performance with suppressed dendrite formation, which is attributed to the strong interconnection of Zn nanoparticles and rGO sheets.The last section is to improve the volumetric capacity by simply pressing fluffy rGO sponge into dense film. It is known that pure rGO sponges are generally delicate and fragile, which is

The photoredox catalysts pheophorbide a (PheoA) and zinc tetraphenylporphine (ZnTPP) under illumination display strong selectivity toward reversible addition–fragmentation chain transfer (RAFT) agents containing thiocarbonylthio groups, namely dithiobenzoates, xanthates, and trithiocarbonates. The underlying mechanism for the process—whether via energy or electron transfer from the photoexcited catalyst to RAFT agent—has remained unclear, as has the reason for the remarkable selectivity. Quantum chemistry and molecular dynamics calculations are utilized to provide strong evidence that none of the common energy‐transfer mechanisms (Förster resonance energy transfer; Dexter electron exchange; or internal conversion followed by vibrational energy transfer) are likely to facilitate polymerization, let alone explain the observed selectivities. In contrast, extensive quantum chemical characterizations of the excited‐state orbitals associated with the catalyst–RAFT agent complexes uncover a clear selectivity pattern associated with charge‐transfer states that is highly consistent with experimental findings. The results shed light on the intrinsic catalytic role of the photocatalysts and provide a strong indication that a reversible electron/charge‐transfer mechanism underpins the remarkable photocatalytic selectivity.

A signature of photo-mediated controlled polymerizations is the ability to modulate the rate of polymerization by turning the light source 'on' and 'off.' However, in many reported systems, growth can be reproducibly observed during dark periods. In this study, emerging photo-mediated controlled radical polymerizations are evaluated with in situ 1H NMR monitoring to assess their behavior in the dark. Interestingly, it is observed that Cu-mediated systems undergo long-lived, linear growth during dark periods in organic media.