Leopoldo Luque, Diego Maradona's doctor, said he did "everything he could" for the former football World Cup winner, who died of a heart attack last week.
Earlier in the day prosecutors in San Isidro, near Buenos Aires, said they were investigating Dr Luque, 39, while Argentinian television showed police raiding the doctor's surgery and home.
The investigation was opened after Maradona's daughters Dalma, Gianinna and Jana expressed concerns over the treatment he received for his heart condition at his home in Tigre, judicial sources told AFP.
Later in the day, Dr Luque, who is no relation to Maradona's former Argentina teammate of the same name, gave an emotional televised conference.
"You want to know what I am responsible for?" he asked between sobs.
"For having loved him, for having taken care of him, for having extended his life, for having improved it to the end.
"He should have gone to a rehabilitation centre. He didn't want to. I am the person who has been taking care of him.
"I'm proud of everything I've done. I have nothing to hide. I am at the disposal of justice."
Maradona's lawyer, Matias Morla, has called for an investigation into claims that ambulances took more than half an hour to reach his house in response to an emergency call on the day of his death.
A preliminary post-mortem examination report established that the cause of death for the 60-year-old was "acute lung oedema and chronic heart failure".
Toxicology reports are still to be filed.
Diego Maradona's doctor says he 'did the best he could' as prosecutors investigate him
Maradona died of a heart attack on Wednesday aged 60, and was buried on Thursday at the Jardin de Paz cemetery on the outskirts of the Argentine capital.
"Our investigations are ongoing, we are talking to witnesses including members of the family" of Maradona, a source close to the San Isidro inquiry said.
"The clinic had recommended that he go elsewhere to be hospitalised, but the family decided otherwise. His daughters signed for him to be discharged from the hospital," said a family member, on the condition of anonymity.
Luque said he did not know why there was no defibrillator in case of a heart attack in Maradona's home in Tigre, and made clear that the home care was not his responsibility.
"I am a neurosurgeon," said Luque.
Luque said an ambulance should have been parked outside.
"A psychiatrist had asked that there should always be an ambulance in front of his house. I don't know who is responsible for the fact that there was no ambulance," Luque said.
Diego "was very sad, he wanted to be alone, and it's not because he didn't love his daughters, his family, or those around him," Luque added. "He was brave."
A judicial source told AFP that no official complaint has yet been filed.
A preliminary autopsy report established that Maradona died in his sleep at noon on Wednesday of "acute lung oedema and chronic heart failure".
The prosecutor's office is awaiting the results of toxicological tests on Maradona's body. The three prosecutors working on the case have requested his medical records, as well as recordings from neighbourhood security cameras.