Detection of DNA hybridization on a liposome surface using ultrasound velocimetry and turbidimetry methods

Enhanced water dispersibility of coenzyme Q10 by complexation with albumin hydrolysate

The biologically important coenzyme Q10 (CoQ10) is widely used as a drug for chronic heart failure, as a nutritional supplement, and in cosmetics. However, the oral bioavailability of CoQ10 is poor due to its extremely low solubility in aqueous media. In this study, complexation of CoQ10 with albumin hydrolysate as a peptide mixture (Pep) was shown to enhance the water dispersibility of CoQ10. An aqueous solution of Pep and an acetone solution of CoQ10 were mixed and lyophilized to obtain a white-yellow powder containing peptides and CoQ10 complex (Q10-Pep). The water dispersibility of Q10-Pep was much higher than that of CoQ10 alone and increased with the quantity of Pep. The particle size of Q10-Pep in aqueous media was 170-280 nm, suggesting that Q10-Pep was present as a hydrocolloidal material. Characterization of Q10-Pep using differential scanning calorimetry showed that CoQ10 was incorporated in the hydrocolloid in an amorphous state.

Optimization of DNA-tagged liposomes for use in microtiter plate analyses

Dye-encapsulating unilamellar DNA oligonucleotide-tagged liposomes were prepared and characterized for use as signal-enhancing reagents in a microtiter plate sandwich-hybridization analyses of single-stranded RNA or DNA sequences. The liposomes were synthesized using the reversed-phase evaporation method and tagged with DNA oligonucleotides by adding cholesteryl-modified DNA reporter probes to the initial lipid mixture. Liposomes were prepared using probe coverages of 0.0013-0.103 mol% of the total lipid input, several hydrophobic and poly(ethylene glycol)-based spacers between the cholesteryl anchor and the probe, and liposome diameters ranging from 200 nm to 335 nm. Their signal enhancement functionality was compared by using them in microtiter plate sandwich-hybridization assays for the detection of single-stranded DNA sequences. In these assays, an optimal reporter probe concentration of 0.103 mol%, a liposome diameter of 274 nm, and a phospholipid concentration of 0.3 mM were found. The length between the cholesteryl anchor and the probe was optimal when a spacer composed of TEG+(CH2O)3 was used. Under optimal conditions, a detection limit of 0.5 nM for a truncated synthetic DNA sequence was found with a coefficient of variation of 4.4%. A 500-fold lower limit of detection using fluorescence was found using lysed dye-encapsulating liposomes versus a single fluorescein-labeled probe. Finally, when this method was applied to the detection of atxA RNA extracted from E.coli SG12036-pIu121 and amplified using NASBA, a minimum extracted concentration of RNA of 1.1x10(-7) microg/microL was found.

Specific volume and compressibility of human serum albumin–polyanion complexes

The ultrasound velocimetry, densitometry, and differential scanning calorimetry have been used to study the formation of the complexes between human serum albumin (HSA) and polyanions heparin (HEP) and/or dextran sulfate (DS). The values of the ultrasound velocity and specific volume allowed us to determine the specific adiabatic compressibility, phi(K)/beta(0), which reflects the degree of volume compressibility of the complexes. We showed that in the presence of HEP and DS the adiabatic compressibility of HSA decreases with increasing concentration of polyanions. HEP more strongly interacts with HSA than DS. pH of electrolyte in the range 4.7-8.5 weakly affects the adiabatic compressibility. Changes of compressibility of HSA can be caused by increase of the hydration due to the formation of the HSA-polyanion complexes and due to partial unfolding of HSA. The HSA-polyanion interaction resulted in decrease of phase transition temperature of the protein. This evidences about protein destabilization in the presence of polyanions.