I think,the movement to the W-O interface is due to DNA aggregation (dependent on all other charged species in your system).Thereby the DNA charges are neutralized and therefore the aggregate becomes more hydrophobic and avoids the bulk water phase, prefering the interface.Ii may become possible to modulate the processes involved via variation of monovalent salt concentration,

First, is your modified DNA pure. It also could be secondary structure. Using an alkaline buffer or glycerol, formamide, urea etc maybe a solution.

Thanks for your reply!

Dikeos Mario Soumpasis

I already screened salt concentrations. Therefore, I used two different buffer systems:

1. 15 mM Phosphate Buffer (ph 6.5)

2. 15 mM Phosphate Buffer , 300 mM NaCl (ph 6.5)

Strangely, when preincubating PEG-maleimide with DNA, both buffers do not show any agglomerates. When I prepare W/O emulsion by mixing the conjugate with hyaluronic acid, it forms this corona and additionally lots of aggromerates in case of the buffer containing 300 mM NaCl. Hyaluronic acid is an polyanionic material. Might this also be an effect of electrostatic repulsion between hyaluronic acid and the DNA? Is there another way instead of adding monovalent salts to avoid this corona?

Alexader Ryncarz

I checked DNA on agarose gel and it is pure giving one clear band. Maybe a simple question, but what is a change to an alkaline buffer affecting and in that case what pH/buffer are you suggesting?

You have a very complicated system involving 2 polyanions (DNA,Hyaluronic) protons and Na+,H+ counterions,Cl- coions and water.The phase diagram depends on all concentrations involved via their screened electrostatic interactions (i.e.also the DNA-hyaluronic interaction in the presence of salt and water).What is actually your goal?Do you have to use hyaluronic?

Dikeos Mario Soumpasis

I wanna use hyaluronic acid-based hydrogel particles for gene expression on microscale. I know, hyaluronic acid is not the best candidate as a polyanion. There are two reasons why I am aiming for hyaluronic acid based platform. The Gels need to be porous enough to allow for diffusion of the ribosomes throughout the particles. Second, the HA is further functionalized with binding motives and therefore HA needs to be quantitatively functionalized (possible due to the carboxyl group of HA). So switching to chitosan or agarose is not really an option.