You can use SPR (surface plasma resonance) or QCM (quartz crystal microbalance)to study the  interactions .

I think you should study the resonant microcantilever as a sensor in evaluating the interactions between PANI and proteins.

eg;

Microcantilever Sensors Coated with a Sensitive Polyaniline Layer for Detecting Volatile Organic Compounds.

Bio-inspired sensor for insect pheromone analysis based on

polyaniline functionalized AFM cantilever sensor.

Thanks Dear Ahmad Fitri Anuar Mahayudin,

Is it possible to provide some literature about it ? 

Thanks Dear Hong Yu, 

can you provide me some literature about it ?