This first paper to me is exciting because it contains liposomal silver nitrate, which is highly soluble. I would have thought that if a silver ion was dissolved within a liposome, it would react with the phospholipids, but apparently this is not so. The second interesting thing from this paper is that they purposely clumped the liposomes together, which to me seems like it could create higher peak concentrations of the contained antibiotic local to bacteria. This could be preferable to ingesting evenly dispersed liposomes. This paper also suggests that 93 degrees F (34 C) is enough to release material from liposomes. This could explain in part what happens with liposomes in the body which is presumably warmer than that.
Embedded Silver Ions-Containing Liposomes in Polyelectrolyte Multilayers: Cargos Films for Antibacterial Agents A new antibacterial coating made of poly(l-lysine)/hyaluronic acid (PLL/HA) multilayer films and liposome aggregates loaded with silver ions was designed. Liposomes filled with an AgNO3 solution were first aggregated by the addition of PLL in solution. The obtained micrometer-sized aggregates were then deposited on a PLL/HA multilayer film, playing the role of a spacer with the support. Finally, HA/PLL/HA capping layers were deposited on top of the architecture to form a composite AgNO3 coating. Release of encapsulated AgNO3 from this composite coating was followed and triggered upon temperature increase over the transition temperature of vesicles, found to be equal to 34 °C. After determination of the minimal inhibitory concentration (MIC) of AgNO3 in solution, the antibacterial activity of the AgNO3 coating was investigated against Escherichia coli. A 4-log reduction in the number of viable E. coli cells was observed after contact for 120 min with a 120 ng/cm2 AgNO3 coating. In comparison, no bactericidal activity was found for PLL/HA films previously dipped in an AgNO3 solution and for PLL/HA films with liposome aggregates containing no AgNO3 solution. The strong bactericidal effect could be linked to the diffusion of silver ions out of the AgNO3 coating, leading to an important bactericidal concentration close to the membrane of the bacteria. A simple method to prepare antibacterial coatings loaded with a high and controlled amount of AgNO3 is therefore proposed. This procedure is far superior to that soaking AgNO3 or Ag nanoparticles into a coating. In principle, other small bactericidal chemicals like antibiotics could be encapsulated by this method. This study opens a new route to modify surfaces with small solutes that are not permeating phospholipid membranes below the phase transition temperature. http://pubs.acs.org/doi/abs/10.1021/la8014755 Though this is also done with poorly soluble silver compounds as in this next study. Which leads one to ask is it possible to get insoluble material into the watery core of a liposome? Topical liposomal delivery of antibiotics in soft tissue infection A new drug delivery system (lipid microcarriers) was studied in an experimental model of infected soft tissue wounds. Superficial, nonlethal infection was produced in the adult rat by injecting 1 ml containing 108 colonyforming units (CFU) of Pseudomonas aeruginosa under the superficial fascia of the paraspinus muscle of a 2-cm2 excised wound. All wounds were dressed with N-Terface, a nonadherent wound material, and covered with Kontor sponge, an open-cell polyurethane sponge containing either normal saline (group I), free tobramycin (groups III and V), liposome-entrapped tobramycin (groups II and IV), silver sulfadiazene (group VI), or liposome-entrapped silver sulfadiazene (group VII). At 24, 48, and 72 hr postinjection, animals were sacrificed and colonyforming units of P. aeruginosa per gram of muscle tissue were determined. Group I had significantly higher colony-forming units of P. aeruginosa per gram than groups II and III at 48 and 72 hr and than groups IV and V at all times. One single dose of liposome-encapsulated silver sulfadiazine significantly decreased bacterial counts compared to untreated controls and, to a similar extent, compared to multiple applications of free drug. Colonyforming units in all treatment groups (II and III, IV and V, VI and VII) were similar at all time periods within equivalent dosages. The ability of one application of liposomal-entrapped antibiotics to result in a therapeutic effect that requires multiple applications of topically applied free antibiotics offers potential clinical advantages. http://www.sciencedirect.com/science/article/pii/0022480490902584 David -- The Silver List is a moderated forum for discussing Colloidal Silver. Rules and Instructions: http://www.silverlist.org Unsubscribe: <mailto:[email protected]?subject=unsubscribe> Archives: http://www.mail-archive.com/[email protected]/maillist.html Off-Topic discussions: <mailto:[email protected]> List Owner: Mike Devour <mailto:[email protected]>
