I am not sure why your answers so far have all said no.
You can convert c++ classes that you have created to blueprint classes - the unreal UMG tutorial uses this.
You can create a blueprint function library and add new blueprint nodes which will execute c++ code that you have written.
There are good reasons to do both of these things - mainly to give non programmers the ability to change variables in your C++ class or to call new functions that do not exist as standard.
I wrote a serial port plugin that could be used via blueprint nodes. It was all written in c++ so, again, I do not understand why others have simply said no.
cheers
Podge