Combined effect of liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate in rat skin.

In this report, we investigated the combined effect of drug liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate (ISN) in rat abdominal skin in vitro. Occlusive application of both liposomal and aqueous ISN solution, with and without addition of 5% glycerol, showed that drug liposomalization and addition of glycerol has far-reaching implications for ISN permeation and accumulation in 4 and 8 weeks old rat abdominal skin. Using 8 weeks old rat abdominal skin, the optimal concentration of glycerol to be added to liposomal ISN was found to be 5%. The ISN mean values permeated through and accumulated in stripped 8 weeks old rat abdominal skin from those formulations described above were not significant different, which might indicate the combined effect of glycerol and liposomal ISN resides solely in the stratum corneum (SC). Based on previous reports, the enhancement effect of glycerol might be due to an increase in the SC hydration, and perhaps due to subtle changes in the lipid organization caused by penetration of liposomal lipids within the SC intercellular spaces. These data might provide evidence that glycerol action on SC is useful to facilitate skin permeation and accumulation of drugs formulated in liposome.

Inducing effect of liposomalization on the transdermal delivery of hydrocortisone: creation of a drug supersaturated state.

In order to investigate the effect of liposomal drugs on skin delivery, it was postulated that the process of liposomalization might lead the drug to an overpredicted solubility state which has far-reaching implications for drug skin permeation and accumulation. In this regard, conventional (CL) and flexible liposomes (FL) were prepared by the lipid film hydration method and the particles were downsized by sonication using hydrocortisone (HC) as a poorly water soluble model drug. The solutions derived from the whole CL and FL suspensions eluted on a Sephadex G-50 column (SG-50) demonstrated that most part of HC not only resides solely in the water phase but also it might exist in an improved solubility state. The results of the in vitro study using rat abdominal skin and occlusive application indicated that HC penetrated and accumulated much better solely than when associated with CL or FL. In regard to the penetration of the non-entrapped HC associated to liposomes bilayer fragments, a very small amount of phospholipids in the non-liposomal part eluted on SG-50 was found that could not justify by itself the penetration of HC associated to liposome bilayer fragments. It was proposed that all the steps of the liposomes preparation process might contribute for the increased HC solubility state, but definitively the presence of phospholipids played a crucial role on improving the HC solubility in the absence of sodium cholate. In comparison with commercially available ointments, the non-entrapped HC solution derived from the whole CL suspension eluted on SG-50 showed a higher concentration of HC accumulated and more uniformly distributed as well in the epidermis and dermis compartments. In addition, the thermodynamic activity of the non-entrapped HC solutions maintaining a driving force of the drug across the skin barrier pointed out that the level of HC solubility achieved during liposome preparation has far-reaching implication for drug skin permeation and accumulation in the experimental conditions used. The findings also indicated that the non-entrapped drug solutions obtained on the process of liposomalization could be useful on transdermal drug delivery systems, particularly for improving the permeation and accumulation capacity of poorly soluble drugs.

A MutS protein-immobilized au electrode for detecting single-base mismatch of DNA.

A novel electrochemical biosensor was developed to detect gene mutation by using a DNA-mismatch binding protein: MutS from Escherichia coli. The MutS protein was immobilized onto an Au-electrode surface via complex formation between a histidine tag of the MutS protein and a thiol-modified nitrilotriacetic acid chemically adsorbed on the Au-electrode surface. When a target double-stranded DNA having a single-base mismatch was captured by the MutS protein on the electrode, some electrostatic repulsion arose between polyanionic DNA strands and anionic redox couple ions. Consequently, their redox peak currents on a cyclic voltammogram with the Au electrode drastically decreased, depending on the concentration of the target DNA, according to the redox couple-mediated artificial ion-channel principle. By using this assay, one can detect all types of single-base mismatch and single-base deletion.

Gene mutation assay using a MutS protein-modified electrode.

A novel electrochemical biosensor for gene mutation detection was developed using a DNA mismatch recognizing protein MutS from E. coli. The MutS protein was immobilized onto an Au electrode by coordination of His-tag at its C-terminus to vacant sites of Ni(II)-nitrilotriacetato complex attached to the surface of electrode. When a target DNA duplex having a mismatch site was captured by the MutS protein on the electrode, the electrostatic repulsion arose between polyanionic DNA duplexes and negatively-charged ferrocyanide/ferricyanide redox couple ions. Consequently, their redox peak currents on a cyclic voltammogram with the Au electrode drastically decreased depending on the concentration of the target DNA according to the redox couple-mediated artificial ion-channel principle. Using this assay, we could detect GT mismatch and deletion mutation in the double-stranded DNA.