The 20-year-old full-back completed a medical on Tyneside on Tuesday after Newcastle agreed a £5m fee. Alan Pardew's quest to find a replacement for José Enrique, who was sold to Liverpool earlier in the transfer window, is therefore complete.
Santon was dubbed "the new Paolo Maldini" in Italy earlier in his career. However, he spent the end of last season on loan at Cesena after falling out of favour at Inter. Santon, who can play both left- and right-back, has seven Italy caps.
With Santon on board, Pardew will step up his search for a forward before the transfer window closes. Macheda, who has slipped down the pecking order at Old Trafford, could move to St James' Park on loan, according to the 20-year-old's agent. Queens Park Rangers also have an interest in Macheda.
Modibo Maiga is another potential recruit after Sochaux confirmed they had received an offer from Newcastle for the striker.
Newcastle are also set to confirm the arrival of the Charlton Athletic goalkeeper Rob Elliot who, like Santon, underwent a medical on Tuesday.
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