Phenolic plant extract enrichment of enzymatically mineralized hydrogels

Hydrogel mineralization with calcium phosphate (CaP) and antibacterial activity are desirable for applications in bone regeneration. Mineralization with CaP can be induced using the enzyme alkaline phosphatase (ALP), responsible for CaP formation in bone tissue. Incorporation of polyphenols, plant-derived bactericidal molecules, was hypothesized to provide antibacterial activity and enhance ALP-induced mineralization. Three phenolic rich plant extracts from: (i) green tea, rich in epigallocatechin gallate (EGCG) (herafter referred to as EGCG-rich extract); (ii) pine bark and (iii) rosemary were added to gellan gum (GG) hydrogels and subsequently mineralized using ALP. The phenolic composition of the three extracts used were analyzed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MSn). EGCG-rich extract showed the highest content of phenolic compounds and promoted the highest CaP formation as corroborated by dry mass percentage meassurements and ICP-OES de-termination of mass of elemental Ca and P. All three extracts alone exhibited antibacterial activity in the following order EGCG-rich > PI > RO, respectively. However, extract-loaded and mineralized GG hydro-gels did not exhibit appreciable antibacterial activity by diffusion test. In conclusion, only the EGCG-rich extract promotes ALP-mediated mineralization.