Intermolecular associations between a cationic lipid and two model polymers were evaluated from preparation and characterization of hybrid thin films cast on silicon wafers. The novel materials were prepared by spin-coating of a chloroformic solution of lipid and polymer on silicon wafer. Polymers tested for miscibility with the cationic lipid dioctadecyldimethylammonium bromide (DODAB) were polystyrene (PS) and poly(methyl methacrylate) (PMMA). The films thus obtained were characterized by ellipsometry, wettability, optical and atomic force microscopy, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and activity against Escherichia coli. Whereas intermolecular ion-dipole interactions were available for the PMMA-DODAB interacting pair producing smooth PMMA-DODAB films, the absence of such interactions for PS-DODAB films caused lipid segregation, poor film stability (detachment from the silicon wafer) and large rugosity. In addition, the well-established but still remarkable antimicrobial DODAB properties were transferred to the novel hybrid PMMA/DODAB coating, which is demonstrated to be highly effective against E. coli.
The interaction between giant bacteriophage DNA and cationic biomimetic particles was characterized from sizing by dynamic light-scattering, zeta-potential analysis, turbidimetry, determination of colloid stability, visualization from atomic force microscopy (AFM), and determination of cytotoxicity against E. coli from colony forming unities counting. First, polystyrene sulfate (PSS) particles with different sizes were covered by a dioctadecyldimethylammonium bromide (DODAB) bilayer yielding the so-called cationic biomimetic particles (PSS/DODAB). These cationic particles are highly organized, present a narrow size distribution and were obtained over a range of particle sizes. Thereafter, upon adding lambda, T5 or T2-DNA to PSS/DODAB particles, supramolecular assemblies PSS/DODAB/DNA were obtained and characterized over a range of DNA concentrations and particle sizes (80-700 nm). Over the low DNA concentration range, PSS/DODAB/ DNA assemblies were cationic, colloidally stable with moderate polydispersity and highly cytotoxic against E. coli. From DNA concentration corresponding to charge neutralization, neutral or anionic supramolecular assemblies PSS/DODAB/DNA exhibited low colloid stability, high polydispersity and moderate cytotoxicity. Some nucleosome mimetic assemblies were observed by AFM at charge neutralization (zeta-potential equal to zero).
Electrostatically driven bilayer coverage from bilayer fragments onto oppositely charged latex produces a highly homodisperse particulate for biomolecules adsorption. Polystyrene sulfate (PSS) particles were covered with single cationic dioctadecyldimethylammonium bromide (DODAB) bilayers. Biomolecules adsorbed were DNA, bovine serum albumin (BSA), cholera toxin (CT) and a mixture of purified 18 kDa/14 kDa Taenia crassiceps proteins (18/14‐Tcra). Firstly, the DODAB/PSS assembly was characterized at 1 mM NaCl and 5 × 109 PSS particles/mL over a range of DODAB concentrations (0.001 ‐1 mM) by means of dynamic light scattering for particle sizing and zeta‐potential analysis. 0.01 mM DODAB was enough to produce perfectly homodisperse and cationic bilayer‐covered particles. Secondly, under these experimental conditions, BSA, CT, and 18/14‐Tcra adsorbed onto biomimetic bilayer‐covered particles yielding langmuirian isotherms with 1.23 × 1017, 0.82 × 1017, 3.37 × 1017 molecules per m2 at limiting adsorption and affinity constants (K) of 3.17 × 1010, 3.39 × 1010, and 1.75 × 1010 M−1, respectively. For DNA adsorption, isotherms did not attain an adsorption maximum up to 20 micrograms/mL DNA. PSS/DODAB/biomolecule assemblies were also characterized by means of dynamic light scattering and zeta‐potential analysis yielding highly monodisperse particles at and above maximal adsorption. In summary cationic bilayer‐covered particles are a novel, highly organized and, possibly, general support for biomolecules immobilization.
Rosa, H. Interactions between Bacteriophage DNA and Cationic Biomimetic Particles. 2008. 78p. Masters Thesis-Graduate Program in Biochemistry.
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