What electrical parameter do you wish to measure using the Microfluidic sensor, considering impedance is a function of R,L,C,f or is it phase, surface velocity, Q, delay or ?
Your choice of Op Amp is current feedback, very high BW and near 0-ohm output impedance with negative feedback.
Why do you need a TVS? If it is polar type, you had it backwards and will add small capacitance in the correct orientation with cathode bar to +ve voltage and anode to ground.