Please note that MySQL's utf8 encoding has a maximum of 3 bytes and is unable to encode *all* unicode characters.
If you need to encode characters beyond the BMP (Basic Multilingual Plane), like emoji or other special characters, you will need to use a different encoding like utf8mb4 or any other encoding supporting the higher planes. Mysql will discard any characters encoded in 4 bytes (or more).
See https://dev.mysql.com/doc/refman/5.7/en/charset-unicode-utf8mb4.html for more information on the matter