Nanomaterials from biologically active molecules: Self-assembly and molecular recognition
This dissertation describes the development of molecular assemblies and molecular recognition of phospholipids (PLs) that exhibit potential applications in emerging nanotechnologies. It consists of two parts: (1) structural features of PLs responsible for recognition of synthetic copolymers, and (2) design, synthesis and analysis of magnetic nanotubes obtained from PLs with a common theme of colloidal synthesis served as a platform for film formation and nano-assemblies of nanotubes. Poly(methyl methacrylate/ n -butyl acrylate) (p-MMA/nBA) colloidal particles that were stabilized by 1,2-dilauroyl- sn -glycero-3-phosphocholine (DLPC) PLs were synthesized, and upon the particle coalescence, PL stratification resulted in the formation of surface localized ionic clusters (SLICs). These entities were capable of recognizing MMA/nBA monomer interfaces along the p-MMA/nBA copolymer backbone and forming crystalline SLICs at the monomer interface. Utilizing spectroscopic analysis combined with ab initio calculations, we determined the nature of their interactions, where the two neighboring MMA and nBA units along the polymer backbone provided conducive environments to signal and attract amphiphilic groups of DLPC, thus initiating SLIC formation. Further studies were conducted on synergistic stimuli-responsive behaviors of p-MMA/nBA colloidal dispersions in the presence of sodium dioctyl sulfosuccinate (SDOSS) and DLPC. Spectroscopic analysis of p-MMA/nBA colloidal dispersions revealed the formation and the preferential orientation of SLICs at the film-air (F-A) or film-substrate (F-S) interfaces in response to the combined stimulus effects. Using bioactive 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9 PC) nanotube-forming PL as templates, concentric ferromagnetic iron oxide-carbon-iron oxide nanotubes (FMNTs) were synthesized. Their structural and morphological features were further investigated by utilizing x-ray diffraction, selected area electron diffraction, high-resolution transmission electron microscopy, and M√∂ssbauer spectroscopy, which revealed that concentric magnetite (Fe 3 O4 )/carbon/magnetite multilayer structures, where the carbon layer was sandwiched between two magnetite layers as well as magnetite was present inside the carbon interlayer. Furthermore, using the synthetic approaches, controllable and uniform diameter, wall thickness, and length of FMNTs were obtained. Further studies focused on the surface modifications of different nano-objects such as C 60 , multi-walled carbon nanotubes, FMNTs, and carbon fibers, which resulted in inhibition of gram positive bacteria and cytotoxicity. This was accomplished by utilizing microwave plasma reactions of maleic anhydride as well as attaching polyethylene glycol spacer and penicillin.