"I had formulated a methylene blue skin cream which provides a continual release."
It's nearly impossible to maintain a constant release of any active while keeping the actives at an appropriate concentration at the site of activity.
A loaded skin patch may be the closest possible answer, except for the barrier that MB seemingly faces at the skin interface.
I'd really like to know how you approached this issue and especially how you measured, or estimated the MB concentration below the superficial layers of the skin.
You need to create a concentration gradient, with the supply of MB at a (much) higher concentration than you'd want in the area of activity. The concentration gradient drives the diffusion once you can facilitate and demonstrate that you can get the MB to passively diffuse.
So whether you want to apply the MB to the surface of your skin, or drive it into the skin by a mechanical means such as needling, you need a reservoir of the MB at a high concentration to hit your < 2.5 μM concentration at the target site, and this will only be a very transient concentration unless you've got a constant supply defusing in behind what is being cleared by the body, of a fairly stable concentration of the stuff continuously waiting to diffuse in.
And that's why I went with the needling and a high localized concentration. It's a compromise, but I know for a fact that the methylene blue is where it should be.
That's not so easy to say with any certainty utilizing a cream.
This whole thing is a very non-trivial problem.
It's not a trivial problem at all, and compromises will have to be made.