Green Hydrogels Composed of Sodium Mannuronate/Guluronate, Gelatin and Biointeractive Calcium Silicates/Dicalcium Phosphate Dihydrate Designed for Oral Bone Defects Regeneration

Abstract

Innovative green, eco-friendly, and biologically derived hydrogels for non-load bearing bone sites were conceived and produced. Natural polysaccharides (copolymers of sodium D-mannuronate and L-guluronate) with natural polypeptides (gelatin) and bioactive mineral fillers (calcium silicates CaSi and dicalcium phosphate dihydrate DCPD) were used to obtain eco-sustainable biomaterials for oral bone defects. Three PP-x:y formulations were prepared (PP-16:16, PP-33:22, and PP-31:31), where PP represents the polysaccharide/polypeptide matrix and x and y represent the weight % of CaSi and DCPD, respectively. Hydrogels were tested for their chemical-physical properties (calcium release and alkalizing activity in deionized water, porosity, solubility, water sorption, radiopacity), surface microchemistry and micromorphology, apatite nucleation in HBSS by ESEM-EDX, FT-Raman, and micro-Raman spectroscopies. The expression of vascular (CD31) and osteogenic (alkaline phosphatase ALP and osteocalcin OCN) markers by mesenchymal stem cells (MSCs) derived from human vascular walls, cultured in direct contact with hydrogels or with 10% of extracts was analysed. All mineral-filled hydrogels, in particular PP-31:31 and PP-33:22, released Calcium ions and alkalized the soaking water for three days. Calcium ion leakage was high at all the endpoints (3 h–28 d), while pH values were high at 3 h–3 d and then significantly decreased after seven days (p < 0.05). Porosity, solubility, and water sorption were higher for PP-31:31 (p < 0.05). The ESEM of fresh samples showed a compact structure with a few pores containing small mineral granules agglomerated in some areas (size 5–20 microns). PP-CTRL degraded after 1–2 weeks in HBSS. EDX spectroscopy revealed constitutional compounds and elements of the hydrogel (C, O, N, and S) and of the mineral powders (Ca, Si and P). After 28 days in HBSS, the mineral-filled hydrogels revealed a more porous structure, partially covered with a thicker mineral layer on PP-31:31. EDX analyses of the mineral coating showed Ca and P, and Raman revealed the presence of B-type carbonated apatite and calcite. MSCs cultured in contact with mineral-filled hydrogels revealed the expression of genes related to vascular (CD31) and osteogenic (mainly OCN) differentiation. Lower gene expression was found when cells were cultured with extracts added to the culture medium. The incorporation of biointeractive mineral powders in a green bio-derived algae-based matrix allowed to produce bioactive porous hydrogels able to release biologically relevant ions and create a suitable micro-environment for stem cells, resulting in interesting materials for bone regeneration and healing in oral bone defects.

Nanomaterials in Dentistry: Current Applications and Future Scope

“…Moreover, green chemistry-based biomaterials were also invented and utilized for oral bone regeneration. Gandolfi et al formulated a hydrogel consisting of polysaccharides (copolymers of L-guluronate and D-mannuronate) and peptide (gelatin) matrix activated with biominerals (calcium silicate, dicalcium phosphate dehydrate) type of fillers and evaluated this green hydrogel for bone regeneration [ 130 ]. Also, they had developed Poly-lactic acid (PLA) based scaffolds loaded in exosomes with suitable minerals (calcium silicate and dicalcium phosphate dehydrate; DCPD) to improve the osteogenic strength of human adipose-derived mesenchymal stem cells [ 131 ].…”

Low-Temperature Plasmas Improving Chemical and Cellular Properties of Poly (Ether Ether Ketone) Biomaterial for Biomineralization

“…However, increased osteoblast viability with decreased osteogenic differentiation is a common outcome for apatite layered materials [ 43 ]. With the other chemical characterization showing higher levels of CaP surface mineralization in this study, mineralization may not occur for several days in the SBF in vitro [ 58 , 61 , 62 , 63 , 64 ]. Several studies have shown that the process of mineralization may take time in SBF for mineral formation.…”

Three-Dimensional Printing Methods for Bioceramic-Based Scaffold Fabrication for Craniomaxillofacial Bone Tissue Engineering

“…Moreover, calcium silicate biomaterials have been combined with natural polymers and collagen peptides due to their gradual resorption properties and the subsequent formation of apatite. In the literature, it has been reported that combinations such as gelatin methacryloyl (GelMA)/alginate/tri-calcium silicate and natural polysaccharides (copolymers of sodium D-mannuronate and L-guluronate)/natural polypeptides (gelatin)/calcium silicate/dicalcium phosphate dihydrate can be used to create an appropriate micro-environment for the regeneration and healing of oral bone defects [ 115 , 116 ].…”