Bioactive Composite Methacrylated Gellan Gum for 3D-Printed Bone Tissue-Engineered Scaffolds

Abstract

Gellan gum (GG) was chemically modified with methacrylic moieties to produce a photocrosslinkable biomaterial ink, hereinafter called methacrylated GG (GGMA), with improved physico-chemical properties, mechanical behavior and stability under physiological conditions. Afterwards, GGMA was functionalized by incorporating two different bioactive compounds, a naturally derived eumelanin extracted from the black soldier fly (BSF-Eumel), or hydroxyapatite nanoparticles (HAp), synthesized by the sol–gel method. Different ink formulations based on GGMA (2 and 4% (w/v)), BSF-Eumel, at a selected concentration (0.3125 mg/mL), or HAp (10 and 30% wHAp/wGGMA) were developed and processed by three-dimensional (3D) printing. All the functionalized GGMA-based ink formulations allowed obtaining 3D-printed GGMA-based scaffolds with a well-organized structure. For both bioactive signals, the scaffolds with the highest GGMA concentration (4% (w/v)) and the highest percentage of infill (45%) showed the best performances in terms of morphological and mechanical properties. Indeed, these scaffolds showed a good structural integrity over 28 days. Given the presence of negatively charged groups along the eumelanin backbone, scaffolds consisting of GGMA/BSF-Eumel demonstrated a higher stability. From a mechanical point of view, GGMA/BSF-Eumel scaffolds exhibited values of storage modulus similar to those of GGMA ones, while the inclusion of HAp at 30% (wHAp/wGGMA) led to a storage modulus of 32.5 kPa, 3.5-fold greater than neat GGMA. In vitro studies proved the capability of the bioactivated 3D-printed scaffolds to support 7F2 osteoblast cell growth and differentiation. BSF-Eumel and HAp triggered a different time-dependent physiological response in the osteoblasts. Specifically, while the ink with BSF-Eumel acted as a stimulus towards cell proliferation, reaching the highest value at 14 days, a higher expression of alkaline phosphatase activity was detected for scaffolds consisting of GGMA and HAp. The overall findings demonstrated the possible use of these biomaterial inks for 3D-printed bone tissue-engineered scaffolds.

Bone Tissue Engineering and Nanotechnology: A Promising Combination for Bone Regeneration

“…Jo et al demonstrated that the injection of chitosan-PEO hydrogel, in combination with BMP-2 and MSCs, promoted bone formation in vivo [83]. Despite their limitations in terms of biocompatibility and biodegradability in vivo [84], their flexibility, i.e., the ability to adjust the structural parameters during the manufacturing processes [85], and the possibility of minimally invasive implantation [86], strongly encourage their application in the BTE field.…”

“…Specifically, HA NPs are generally combined with synthetic polymers like PLA [214,215] and PCL [216,217] in order to overcome their limits for clinical uses by enhancing cell adhesion and mineral deposition in vitro. For the same reason, HA NPs were also used to improve the mechanical and biological properties, as well as the stability under physiological conditions, of hydrogel scaffolds, such as Gellan Gum, in which it was observed that the integration of HA NPs enhanced cell proliferation and ALP activity in vitro [84].…”

Microbial Exopolysaccharide Composites in Biomedicine and Healthcare: Trends and Advances

“…Alvel et al [52] also prepared a composite hydrogel of xanthan with Konjac glucomannan, which also focused on wound healing. On the other hand, a 3D scaffold for tissue engineering was prepared with alginate-gellan gum [53] and methacrylated gellan gum [54]. The applications of EPS composites with various polymers have been summarized below:…”