Attacking midfielder Ali Fuseini and striker Scott Spencer have completed permanent moves to Sincil Bank while Arsenal have allowed Gavin Hoyte to remain on loan at the club until the end of the season.
Elsewhere on deadline day, Accrington Stanley have re-signed Kevin Long on loan from Burnley and Shrewsbury have captured David Davis on a temporary basis from Wolves.
The Shrews are also set to sign Coventry City central defender Jermaine Grandison.
Moving within the division are Anthony Straker (Aldershot to Wycombe Wanderers) and Matt Green (Oxford United to Cheltenham).