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- Gene delivery using dendrimer/pDNA complexes immobilized in electrospun fibers using the Layer-by-Layer techniquePublication . Ramalingam, Kirthiga; Castro, Rita; Pires, Pedro; Shi, Xiangyang; Rodrigues, João; Xiao, Shili; Tomás, HelenaA gene delivery platform for potential use in tissue engineering applications was developed by surface functionalization of biodegradable electrospun poly(lactic-co-glycolic acid) (PLGA) fibers with nanolayers of chitosan (cationic polymer) and alginate (anionic polymer) using the Layer-by-Layer (LbL) technique. The developed system not only supported the attachment and growth of human Mesenchymal Stem Cells (hMSCs), but also was capable of delivering pDNA/dendrimer complexes and inducing cell differentiation towards the osteogenic lineage when a pDNA codifying for human Bone Morphogenetic Protein-2 (BMP-2) was used. Beyond providing a means for pDNA/dendrimer complex immobilization, the polyelectrolyte coating conferred sustained release properties to the scaffold that resulted in pDNA protection from degradation. The polyelectrolyte coating, by itself, also contributed to enhance cell differentiation.
- Recent advances in β-galactosidase and fructosyltransferase immobilization technologyPublication . Ureta, Maria Micaela; Martins, Gonçalo Nuno; Figueira, Onofre; Pires, Pedro Filipe; Castilho, Paula Cristina; Gomez-Zavaglia, AndreaThe highly demanding conditions of industrial processes may lower the stability and affect the activity of enzymes used as biocatalysts. Enzyme immobilization emerged as an approach to pro mote stabilization and easy removal of enzymes for their reusability. The aim of this review is to go through the principal immobilization strategies addressed to achieve optimal industrial proc esses with special care on those reported for two types of enzymes: b-galactosidases and fructo syltransferases. The main methods used to immobilize these two enzymes are adsorption, entrapment, covalent coupling and cross-linking or aggregation (no support is used), all of them having pros and cons. Regarding the support, it should be cost-effective, assure the reusability and an easy recovery of the enzyme, increasing its stability and durability. The discussion provided showed that the type of enzyme, its origin, its purity, together with the type of immobilization method and the support will affect the performance during the enzymatic synthesis. Enzymes’ immobilization involves interdisciplinary knowledge including enzymology, nanotechnology, molecular dynamics, cellular physiology and process design. The increasing availability of facilities has opened a variety of possibilities to define strategies to optimize the activity and re-usability of b-galactosidases and fructosyltransferases, but there is still great place for innovative developments.