Discussing the final size and shape of the reconstructed tissues in tissue engineering.

Tissue engineering (TE) has made a revolution in repairing, replacing, or regenerating tissues or organs, but it has still a long way ahead. The mechanical properties along with suitable physicochemical and biological characteristics are the initial criteria for scaffolds in TE that should be fulfilled. This research will provide another point of view toward TE challenges concerning the morphological and geometrical aspects of the reconstructed tissue and which parameters may affect it. Based on our survey, there is a high possibility that the final reconstructed tissue may be different in size and shape compared to the original design scaffold. Thereby, the 3D-printed scaffold might not guarantee an accurate tissue reconstruction. The main justification for this is the unpredicted behavior of cells, specifically in the outer layer of the scaffold. It can also be a concern when the scaffold is implanted while cell migration cannot be controlled through the in vivo signaling pathways, which might cause cancer challenges. To sum up, it is concluded that more studies are necessary to focus on the size and geometry of the final reconstructed tissue.

Polymeric nanoparticles as therapeutic agents against coronavirus disease.

Nanotechnology has the potential to improve the combat against life-threatening conditions. Considering the COVID-19 scenario, and future outbreaks, nanotechnology can play a pivotal role in several steps, ranging from disinfection protocols, manufacture of hospital clothes, to implementation of healthcare settings. Polymeric nanoparticles are colloidal particles with size ranging from 10 to 999 nm, composed of natural or synthetic polymers. The versatility of polymeric-based nanoparticle engineering can provide (i) specificity, (ii) tunable release kinetics, and (iii) multimodal drug composition, making it possible to overcome common limitations encountered during traditional drug development. Consequently, these particles have been widely used as drug delivery systems against several diseases, such as cancer. Due to inherent competitive advantages, polymeric-based nanoparticles hold astonishing potential to counteract the new coronavirus disease (COVID-19). For this reason, in the present study, the latest advancements in polymer-based nanotechnology approaches used to fight against SARS-CoV-2 are compiled and discussed. Moreover, the importance of forefront in vitro technologies - such as 3D bioprinting and organ-on-chip - to evaluate the efficacy of nanotherapeutic agents is also highlighted. Polymeric nanoparticles can be functionalized to enhance its potential as a nanotherapeutic agent. Due to its many advantages, polymeric-based nanoparticles systems are a promising approach against coronavirus disease 2019 (COVID-19).

Adult Stem Cells Spheroids to Optimize Cell Colonization in Scaffolds for Cartilage and Bone Tissue Engineering.

Top-down tissue engineering aims to produce functional tissues using biomaterials as scaffolds, thus providing cues for cell proliferation and differentiation. Conversely, the bottom-up approach aims to precondition cells to form modular tissues units (building-blocks) represented by spheroids. In spheroid culture, adult stem cells are responsible for their extracellular matrix synthesis, re-creating structures at the tissue level. Spheroids from adult stem cells can be considered as organoids, since stem cells recapitulate differentiation pathways and also represent a promising approach for identifying new molecular targets (biomarkers) for diagnosis and therapy. Currently, spheroids can be used for scaffold-free (developmental engineering) or scaffold-based approaches. The scaffold promotes better spatial organization of individual spheroids and provides a defined geometry for their 3D assembly in larger and complex tissues. Furthermore, spheroids exhibit potent angiogenic and vasculogenic capacity and serve as efficient vascularization units in porous scaffolds for bone tissue engineering. An automated combinatorial approach that integrates spheroids into scaffolds is starting to be investigated for macro-scale tissue biofabrication.