Contents lists available at ScienceDirect Journal of CO 2 Utilization journal homepage: www.elsevier.com/locate/jcou scCO 2 -foamed silk fibroin aerogel/poly(ε-caprolactone) scaffolds containing dexamethasone for bone regeneration Leticia Goimil a , Víctor Santos-Rosales a , Araceli Delgado b , Carmen Évora b , Ricardo Reyes c , Antonio A. Lozano-Pérez d , Salvador D. Aznar-Cervantes d , Jose Luis Cenis d , Jose Luis Gómez-Amoza a , Angel Concheiro a , Carmen Alvarez-Lorenzo a, ⁎ , Carlos A. García-González a, ⁎ a Departamento de Farmacología, Farmacia y Tecnología Farmacéutica, R+D Pharma Group (GI-1645), Facultad de Farmacia and Health Research Institute of Santiago de Compostela (IDIS), Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain b Departamento de Ingeniería Química y Tecnología Farmacéutica, Instituto de Tecnologías Biomédicas (ITB), Centro de Investigaciones Biomédicas de Canarias, Universidad de La Laguna, 38200 La Laguna, Spain c Departamento de Bioquímica, Microbiología, Biología celular y Genética Instituto de Tecnologías Biomédicas (ITB), Centro de Investigaciones Biomédicas de Canarias, Universidad de La Laguna, 38200 La Laguna, Spain d Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario, 30150, La Alberca, Murcia, Spain ARTICLE INFO Keywords: Scaffolds Silk fibroin aerogel Supercritical foaming Dexamethasone In vivo bone repair ABSTRACT Bone scaffolds prepared with porogens and bioactive agents can accelerate bone tissue formation by providing a suitable 3D-porous structure that promotes cell colonization and differentiation towards the osteogenic lineage. In this work, scaffolds containing poly(ε-caprolactone) (PCL) as biopolymeric matrix, silk fibroin as cell adhesion promoter, and dexamethasone as osteogenic differentiation agent, were prepared by supercritical foaming (37 °C, 140 bar, 1 h), a solvent-free method providing a straightforward and effective route for the processing of bioactive grafts. Silk fibroin aerogels in the form of submicron-sized particles were herein developed for the first time and evaluated as porosity inducers. These aerogels incorporated in the scaffolds refined the porous structure and facilitated cell infiltration and the biological fluid transport. Dexamethasone was used in two different forms (base, DX and phosphate salt, DS) to unveil their role in bone regeneration. The morphology of the scaffolds was evaluated using mercury intrusion porosimetry, helium pycnometry and in silico structure modelling. Different release profiles were recorded when using DX or DS. The biological performance was as- sessed in in vivo tests in calvarial defects using a rat model. Results unveiled the interesting morphological properties of the scaffolds in terms of porosity, pore size distribution and interconnectivity, which are compa- tible with their application in bone repair. In vivo tests showed the importance of the dexamethasone form and release profile in promoting the bone tissue regeneration with a significant increase in the number of ossification foci and in bone repair extent 14 weeks post-implantation for certain formulations. 1. Introduction The advent of regenerative medicine discipline boosted the devel- opment of engineered bone grafts comprising a polymeric matrix, bioactive agents and even cells [1,2]. The polymeric matrix is designed to provide a provisional mechanical support and to serve as a 3D- template for cell colonization and tissue ingrowth. Bioactive agents should be able to promote cell growth and proliferation as well as differentiation towards the osteogenic lineage. Cells can be either pre- seeded in the grafts using bioreactors before implantation or may colonize the scaffold after the surgical procedure emulating the normal healing process. The proper choice and design of these three elements of the grafts will largely influence the scaffold performance and the osteointegration. Regarding the polymeric matrix, synthetic polymers provide better reproducibility between batches with respect to natural polymers in terms of molecular weight and purity leading to a more precise control of biodegradation rate to match the biological tissue growth rate [3,4]. Among them, polyesters (e.g., poly(ε-caprolactone), poly(lactic acid) and poly(lactic-co-glycolic acid)) are the most common choice with https://doi.org/10.1016/j.jcou.2019.02.016 Received 19 July 2018; Received in revised form 18 February 2019; Accepted 24 February 2019 ⁎ Corresponding authors. E-mail addresses: carmen.alvarez.lorenzo@usc.es (C. Alvarez-Lorenzo), carlos.garcia@usc.es (C.A. García-González). Journal of CO₂ Utilization 31 (2019) 51–64 2212-9820/ © 2019 Elsevier Ltd. All rights reserved. T