Supercritical phase inversion process was successfully implemented to produce loaded polymeric membranes of cellulose acetate with a synthetic clay mineral (i.e., laponite), to enhance both their mechanical and biological properties. The generated structures presented a microporous structure with a pore size ranging from 8.7 to 12.6 µm, depending on the laponite concentration: the addition of a solid in the starting solution caused a phase separation delay and a consequent pores size increasing. At the same time, the addition of laponite in form of nanodisks improved the mechanical characteristics of the material in terms of Young modulus up to 4.2 MPa. Furthermore, a relevant increase up to 80.9% on cellular adhesion (cell line BT474) was found thanks to the incorporation of laponite inside these membranes. This phenomenon can be attributed to the high surface area and the mineral properties of this clay; therefore, the inclusion of laponite in cellulose acetate membranes produced by supercritical phase inversion, drastically transformed this polymer into a suitable material for tissue engineering applications.