Can silk be considered as an electret?

As I understand, this is currently an open question as to whether or not filters made from silk are rightly considered "electrets." Generally, I think the issue is that the innate electric dipole moment required for an electret to be effective is too weak for silk, so they must be treated in some way with other materials.

However, silk nanofabrics have shown great potential for filtration purposes, especially regarding pollutants such as PM$_{2.5}$. See this paper for a study about this, where they found silk nanofibers to have very high filtration efficacy for particulate matter.

For a larger discussion about these things, see this paper. Specifically section 5.4 and the discussion at the end where they describe current methods, including ways of taking advantage of electret and nanofiber properties of materials.