First of all, we would like to thank Mackay and Lakhtakia1 who have carefully read our paper and for their valuable comments on our manuscript. We agree that the polarizability is a dyadic.
For our aims (analytical models, full-wave simulations, and sensitivity analysis), we have assumed the impinging electromagnetic field as a plane wave having the electric field parallel to the nanoparticle principal axis (-axis as depicted in the Fig. 1 of the paper). In this case, Eq. (1) and the following equations refer only to scalar component of the dyadic polarizability (sufficient to evaluate the nanoparticle response under the aforementioned excitation condition).
We have to point out that for sensing applications the analyzed polarization is crucial in order to obtain the best sensitivity performances.