Interactions of Microorganisms with Lipid Langmuir Layers.

Preventing microbial contamination of aquatic environments is crucial for the proper supply of drinking water. Hence, understanding the interactions that govern bacterial and virus adsorption to surfaces is crucial to prevent infection transmittance. Here, we describe a new approach for studying the organization and interactions of various microorganisms, namely, Escherichia coli (E. coli) bacteria, E. coli-specific bacteriophage T4, and plant cucumber green mottle mosaic viruses (CGMMV), at the air/water interface using the Langmuir-Blodgett (LB) technique. CGMMV were found as applicable candidates for further studying their interactions with Langmuir lipid monolayers. The zwitterionic, positively, and negatively charged LB lipid monolayers with adsorbed viruses were deposited onto solid supports and characterized by atomic force microscopy. Using polymerase chain reaction, we indicated that the adsorption of CGMMV onto the LB monolayer is a result of electrostatic interactions. These insights are useful in engineering membrane filters that prevent biofouling for efficient purification systems.

The role of hydrophobic, aromatic and electrostatic interactions between amino acid residues and a titanium dioxide surface.

Understanding the nature of interactions between inorganic surfaces and biomolecules, such as amino acids and peptides, can enhance the development of new materials. Here, we present single molecule force spectroscopy (SMFS) measurements of the interactions between an atomic force microscopy (AFM) probe, modified with various amino acids, and a titanium dioxide surface. Specifically, we study the affinity of amino acids toward a titanium dioxide surface bearing hydrophobic (Leu), aromatic (Phe) and hydrophilic (Orn) residues. We find that aromatic interactions dominate over aliphatic in their affinity to the titanium dioxide surface. In addition, we show that by combining aromatic and hydrophilic moieties in a single amino acid (NH2-Phe), the adhesion of the latter to the surface increases. Furthermore, the affinity of positively charged amino acids to the titanium dioxide surface is higher than that of uncharged, and can be increased more, with elevating the pH of the buffer above the pKa of the basic residues. The kinetic and thermodynamic parameters imply that the dynamics of the surface-amino acid interface are mostly governed by hydrophobic interactions.

Electrochemical Triggered Dissolution of Hydroxyapatite/Doxorubicin Nanocarriers.

The controlled release of drugs by an external stimulus is of pivotal interest and importance as a means of increasing administration efficacy. Accordingly, many responsive systems have been developed based on primarily pH, temperature, and light changes. Here, a novel electrochemical triggered release of a doxorubicin (Dox)-loaded hydroxyapatite (HAp) nanoparticle (NP) system is presented. Dox is loaded onto HAp NPs by producing a stable dispersion in DMSO. The Dox-HAp NPs are electrophoretically deposited on a stainless steel (S.S) surface. The adsorbed Dox-HAp NPs are released either by applying a moderate electrochemical potential pulse or upon scanning the potential. Two mechanisms were proposed. The first is that the positive potential induces the desorption of the Dox-HAp NPs. Alternatively, the positive potential could drive the oxidation of water and generation of protons, causing the dissolution of the Dox-HAp NPs. In situ characterization techniques, such as atomic force microscopy (AFM) and confocal microscopy, were used to gain insight on the release mechanism. All measurements allude to the electrochemically driven dissolution of the Dox-HAp NPs and release of the embedded drug. In vitro antitumor activity against both HT-29 and A2780 cancer cells revealed that the efficacy of the released Dox was not significantly affected by the electrochemical process. We believe that the electrochemically triggered release of NPs could be applied to many other responsive systems.