TEM images of HAp1 powder combined with 0.05 wt% chitosan (a) and of HAp1 cement combined with 20 wt% gelatin (b). Drug release profiles of HAp1 powder, HAp1 powder combined with 0.05 wt% chitosan, HAp1 cement and HAp1 cement combined with 20 wt% gelatin (c), along with the linear fits of the release from the HAp1 powder combined with 0.05 wt% chitosan (d) and from the HAp1 cement combined with 20 wt% gelatin (e) to the Korsmeyer–Peppas model, from which the Korsmeyer–Peppas exponent, n, was derived.