Mechanical and thermal properties of gelatin films at different degrees of glutaraldehyde crosslinking.

The mechanical, thermal, swelling and release properties of glutaraldehyde (GTA) crosslinked gelatin films have been investigated in order to verify the influence of GTA concentration on the stability of the films. Air-dried films were submitted to treatment with GTA solutions at concentrations ranging from 0.05 to 2.5 wt%. At the smallest GTA concentration, the crosslinking degree, determined by trinitrobenzensulfonic acid assay, amounts to about 60% and increases up to values near 100%, obtained with GTA concentrations > or = 1 wt%. Simultaneously, the deformability of the films decreases, whereas the stress at break, sigmab, and the Young's modulus, E, increase. A crosslinking degree of about 85%, obtained using 0.25% GTA, is enough to prevent gelatin release in buffer solution and to provoke a significant reduction of the swelling in physiological solution. Furthermore, crosslinking greatly affects the thermal stability of the samples, as indicated by the results of differential scanning calorimetry (d.s.c.) investigation carried out on wet and air-dried films. The data suggest that the use of GTA at low concentration, which is desiderable to prevent toxicity, allows to modulate the physico-chemical properties of gelatin films, in order to obtain stable materials with a wide range of possible biomedical applications.