Will negative ESD strike pose any damages to I/O port connected to TVS?
The negative hit will actually end up shunted to ground through the built-in ESD protection clamps in the IC. Even if that protection wasn't there, the TVS would shunt the hit to ground, but it would clamp at the negative clamping voltage, below ground. The bidirectional TVS really isn't helping you on your negative hits. A unidirectional TVS would do the same thing, but clamp at just a diode drop below ground.