There's a subtle difference that you can use either one and use them interchangeably. The difference: Use 'Suspicious Of' when you just think that not in detail. But, use 'Suspicious About' when you think but in detail. (More detailed than 'suspicious of') and I think that 'Suspicious Of' is used for people, while 'Suspicious About' is used for something (Not people, but their behavior, habit etc.).

Either is fine.