Repentance not regret
Judas must have tried to tell Jesus you said 'A saved person cannot be demon possessed. Only an unsaved person can be demon possessed. Light and darkness cannot dwell together. I am one of your disciples.' For satan entered into him later.
Judas did not repent of his sin. He had regret for betraying "innocent blood" but notice that he did not say, "I betrayed the Messiah...the Son of David..." rather he only came to the chief priests in the morning; when he saw that Jesus was condemned to death. All night long, as Jesus was being tried and beaten and questioned, Judas held on to his money. It was only when he saw that Jesus was condemned to die that he went to the priests. It was an act to redeem himself-- a futile attempt to undo what he had done. Notice what he said, "I have betrayed..." It was still all about himself. He was trying to rid himself of his guilt. Notice he did not storm in and yell, "Jesus is innocent. He is the Messiah."
Repent in Matthew 27:3 is 3338. metamellomai (met-am-el'-lom-ahee)
As compared to "Repent" used in as used in Matthew 3:2 -"Repent for the kingdom of heaven is at hand."
3340. metanoeo (met-an-o-eh'-o)
Judas' remorse (Greek word. metamelomai) does not indicate a sorrow for sinning against God but rather a remorse for the consequences of his deed.
Kind of like someone saying. "Oh, if only I did not do it...I should have done that."
Rather than asking God for forgiveness, Judas chose to end his life. He did not believe the words of Jesus concerning hell. He hung himself, thinking that it would end it all for him--All his guilt and shame.
Repentance can bring a change in your life but just regret will never change you.