Design of acemannan-based films as a platform for delivery of bioactive agents

In the last years, a renewed interest in the use of natural compounds derived medicinal plants arises due to their composition and intrinsic bioactive properties. Therefore, the beneficial health effects of aloe vera (AV), and its phytocompounds have been demonstrated in the treatment of many diseases such as diabetes, cancer and skin diseases. Acemannan (ACE), the main polysaccharide of AV leaves is recognized for its cytocompatibility, wound healing inducer, antibacterial action and immunomodulator activity. Thus, the association of ACE with natural polymers namely chitosan (CHT) and alginate (ALG) can result in strong synergistic effects, as a consequence of the interaction among these polymers and the formation of mixed junction zones. The combination of these polymers may be applied as wound dressings, as CHT/AV membranes were found to be promising wound dressing materials as they display a higher antibacterial potency. In this work, ACE-based films were prepared to combine ACE with CHT and ALG. For that purpose, 2.5% (w/v) solutions of ACE, ALG and CHT were prepared using water and acetic acid 1%(v/v), respectively. The blended solutions, defined as CHT/ACE, ALG/ACE or CHT/ALG, were prepared by the combination of different volumes of the original solutions. Those were casted in the moulds and left to dry at 37ºC for 24h. CHT/ALG system act as a comparable model. The developed films were characterized using FTIR, DSC, and XPS to evaluate their physical features and chemical composition as well as the interaction established between the matrices in the blended formulations.  Moreover, the antibiotic release was evaluated immersing the films in phosphate buffer solution (PBS) for pre-determined times. The XPS spectra of the blended samples, when compared with films of the isolated polymers, present some differences in the N1s, besides the two peaks atributed to amine and amide groups a third peak representative of the protonated amine appears, related to the arrangement of the polymers. To enable the prepared films to be used as a wound bioactive dressings they were doped with gentamicin. The antibiotic was incorporated into the polymeric solution before cast. Further, the gentamicin release in PBS demonstrates that the films can release in a sustained manner over the studied period. The findings, obtained until now, suggested, that the ACE-based films could be good candidates as wound bioactive dressings.