Many different substrates are used in tissue engineering as platforms to enhance cell attachment, proliferation and activity, either in-vitro, to multiply specific cell lines, or in-vivo, to induce shorter healing time of injured or missing tissue. However, their hydrophobicity and lack of specific functionalities make them non-ideal for cell adhesion and growth. Treating the surfaces by exposing them to a series of steps including, but not limited to, a diazonium based wet chemistry allows one or more functional groups to be applied to the surface improving cell adhesion and growth. Embodiments of the invention exploiting PDLLA, PMMA and roughed PEEK are demonstrated including both a one-stage and a two-stage process, and at times a vacuum treatment, allowing modification of inner and outer surfaces.