iPhone 4s wont turn on

My iPhone wont turn on. I have tried pressing the power and home button, and it didnt work. I left the phone to charge overnight and its still just a black screen. I have tried using different charger cables and it didnt work. When I plug the phone into the computer it launches itunes (11.1.3) but never shows the phone and its still a black screen. I have tried restarting, powering off, and tried to put it in DFU mode and it never shows on itunes. I have tried to clean the charger port using a dry toothbrush and it still wont turn on.