Pectin hydrogels for regenerative medicine: injectable systems, cell delivery and antimicrobial formulations

Injectable hydrogels are promising systems for the regeneration of damaged tissues due to their ability to immobilize, deliver and locally release cells, proteins, drugs, genes or growth factors. From a clinical point of view, the injectable system approach for regenerative purposes instead of traditional surgical procedures is very attractive as it reduces patient discomfort, risk of infection, scar formation, the treatment and medical cost. Pectin-based injectable hydrogels could be designed with cells/drugs/biomolecules immobilized within the network, and by chemical modifications it is possible to improve cell adhesion or antibacterial activity. Pectins are a family of polysaccharides found in the primary walls of plant cells, mainly composed of D-galacturonic acid residues partially methyl-esterified. Pectin are one of the most promising polymer for tissue regeneration, as it forms gels without the use of harsh conditions. Pectin gels are proving wide applicability as biomaterials in regenerative medicine application, such as microspheres and pectin-based biocomposites. In view to obtain an ad hoc pectin-based hydrogel for a specific purpose, pectin can be extracted from different sources and its characteristics vary according to the plant species from which it is extracted. The main characteristics of the appropriate process of extraction are the use of biocompatible chemicals and the possibility to preserve the peculiar structural characteristics such as the integrity of branched regions, which show an important role in cell interaction. A high molecular weight and a low degree of esterification need to be pursued to form stable, ionotropic gels, in conditions compatible with cell viability or biomolecules loading.