Emoji in Ionic app

we are trying to use emoji in a Ionic Application in a comment form. The problem is that emoji are visualized in the page but when we get back the results from the server, everything gets lost (we see ???). We are using Restangular as network library and on the server the DB, DB connection, tables and columns are in utfmb4_unicode_ci.
Any advice?

Are the characters correctly encoded when you transmit them over the wire?

what did u mean with “correctly encoded” ?