He reserved special praise for manager Wenger, who signed him as an 18-year-old in 2006.
"Arsenal has been my home for five years and it will be in my memory forever. I had to learn things the hard way, but luckily I excelled and matured in England too," he told Sao Paulo's official website.
"I have a lot more joy than sorrow in England and I still feel honoured to have played for so long in one of the top ten clubs in the world.
"I would like to thank all the players and staff who lived in this period, but especially to Arsene Wenger, who was arguably the person who most trusted and invested in me.
"He always treated me like a son and got so far, I have no doubt that Wenger was instrumental in my development as an athlete. He is a fantastic guy."