Surface treatment of sodium alginate matrices

Sodium alginate-based matrices loaded with either sodium salicylate or theophylline as test drugs were prepared. The soaking procedure of the matrices in aqueous solutions of calcium cholide allowed to obtain directly a superficial calcium alginate membrane. On the contrary, the deposition of inorganic salt amid the sodium alginate is obtained by soaking the matrices with alcoholic solutions. The formation mechanism of the superficial film affected the release behaviour.