However,

the direct conjugation of antibodies to NO-ELIPs results in greater than 90% loss of antibody immunoreactivity, mainly due to the denaturation induced by the gas pressurization and freeze-thawing procedures. To avoid this drawback, NO-ELIPs and antibodies have been linked by biotin/avidin-mediated coupling, providing a novel conjugation method allowing site-specific NO delivery [86]. Another class of liposomes that can be successfully used as nanocarriers is the thermosensitive Inhibitors,research,lifescience,medical liposomes, which may be employed in the storage, delivery, and active release of NO in a heat-mediated manner [87, 88]. Tai et al. [89] encapsulated spermine NONOate (SPER/N2O2), a zwitterionic diazeniumdiolate employed Inhibitors,research,lifescience,medical as an NO precursor, in liposomes composed of phospholipids of different temperature sensitivities (Figure 4). Upon heating, an influx of extraliposomal protons decreased the normally intraliposomal pH, diminishing the pH gradient across the membrane and

subsequently inducing rapid NO release. The collapse of the pH gradient suggests that heat induced an increase in the lipids bilayer’s permeability, allowing proton influx. SPER/N2O2 is known to spontaneously dissociate into two molecules at a much faster rate at physiological pH than at the basic pH, demonstrated by slower NO release from basic intra-liposomal solution than from physiological intra-liposomal solution. The degree of the slowed Inhibitors,research,lifescience,medical NO release was also dependent on the specific phospholipid composition of the liposomes. Moreover, the presence of a stronger

pH gradient when the liposomes were applied to a more acidic environment increased proton influx and thus NO release. Because heat is generated in some pathological conditions, such as in tumor tissue, selleckchem Vorinostat thermo-sensitive liposomes containing NO may have Inhibitors,research,lifescience,medical applications in anticancer therapeutics [8]. Figure 4 Schematic representation Inhibitors,research,lifescience,medical of the stabilization of zwitterionic diazeniumdiolate by loading liposomes. Reprinted from Tai et al. [89], with the permission of Elsevier. Dinh et al. [90] investigated the effect of the hydrophobic structure of liposomes’ phospholipids Brefeldin_A and surfactant micelles on NO formation from zwitterionic diazeniumdiolates. The acid-catalyzed dissociation of NO has been examined in phosphate-buffered solutions of sodium dodecyl sulfate (SDS) micelles and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-[phospho-(1-glycerol)] sodium salt (DDPG) phospholipid liposomes. Both phosphatidylcholine and phosphatidylglycerol liposomes catalyze NO dissociation from diazeniumdiolate substrates. The larger catalytic factors observed for DPPG liposomes than for DPPC liposomes and SDS micelles arise from the ability of the anionic liposome to concentrate the reactants at the liposome surface. This is accomplished through coulombic attraction of aqueous hydrogen ions and positive nitrogen centers in the diazeniumdiolate zwitterions.