The 26-year-old Argentine scored a hat-trick for Boro's U21s in a behind-closed-doors friendly against Blackpool on Tuesday, but his first team opportunities have been limited to just two appearances.
He made seven appearances on loan with Rotherham late last year, scoring in his final game....against Blackpool.
He is expected to go straight in to the Brighton squad for their game at home to Birmingham City on Saturday.
The Seagulls currently sit one point and one place about the relegation zone.
Aitor Karanka commented on the move: "It's not fair that someone of Emmanuel's ability should not be playing. His opportunities have been limited here and it is good that there is interest from another club who might be able to help him in terms of games played. I think this move will be good for him."