polymers Review A Comparative Review of Natural and Synthetic Biopolymer Composite Scaffolds M. Sai Bhargava Reddy 1 , Deepalekshmi Ponnamma 2 , Rajan Choudhary 3,4,5 and Kishor Kumar Sadasivuni 2, *   Citation: Reddy, M.S.B.; Ponnamma, D.; Choudhary, R.; Sadasivuni, K.K. A Comparative Review of Natural and Synthetic Biopolymer Composite Scaffolds. Polymers 2021, 13, 1105. https://doi.org/10.3390/polym13071105 Academic Editor: Hyeonseok Yoon Received: 10 February 2021 Accepted: 23 March 2021 Published: 30 March 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Center for Nanoscience and Technology, Institute of Science and Technology, Jawaharlal Nehru Technological University, Hyderabad 500085, India; msbhagi96@gmail.com 2 Center for Advanced Materials, Qatar University, Doha P.O. Box 2713, Qatar; deepalekshmi@qu.edu.qa 3 Rudolfs Cimdins Riga Biomaterials Innovations and Development Centre of RTU, Faculty of Materials Science and Applied Chemistry, Institute of General Chemical Engineering, Riga Technical University, Pulka St 3, LV-1007 Riga, Latvia; rajandeshwal@gmail.com 4 Baltic Biomaterials Centre of Excellence, Headquarters at Riga Technical University, LV-1007 Riga, Latvia 5 Center for Composite Materials, National University of Science and Technology “MISiS”, 119049 Moscow, Russia * Correspondence: kishorkumars@qu.edu.qa Abstract: Tissue engineering (TE) and regenerative medicine integrate information and technology from various fields to restore/replace tissues and damaged organs for medical treatments. To achieve this, scaffolds act as delivery vectors or as cellular systems for drugs and cells; thereby, cellular material is able to colonize host cells sufficiently to meet up the requirements of regeneration and repair. This process is multi-stage and requires the development of various components to create the desired neo-tissue or organ. In several current TE strategies, biomaterials are essential compo- nents. While several polymers are established for their use as biomaterials, careful consideration of the cellular environment and interactions needed is required in selecting a polymer for a given application. Depending on this, scaffold materials can be of natural or synthetic origin, degrad- able or nondegradable. In this review, an overview of various natural and synthetic polymers and their possible composite scaffolds with their physicochemical properties including biocompatibil- ity, biodegradability, morphology, mechanical strength, pore size, and porosity are discussed. The scaffolds fabrication techniques and a few commercially available biopolymers are also tabulated. Keywords: scaffolds; tissue engineering; natural biopolymer; synthetic biopolymer; biodegradability 1. Introduction Tissue engineering (TE) is the in vitro construction of bioartificial tissues and in vivo modification of cell growth and function through the implantation of appropriate cells isolated from donor tissues to generate biocompatible scaffold materials [1]. This approach specifically focuses on the vital imbalance between the rising number of patients waiting for organ transplantation due to end-stage failure and a limited number of donated organs available for those procedures [2]. TE and regenerative medicine integrate information and technology from various fields such as genetics, engineering, pharmaceutics, medicine, chemistry, and materials sciences to perform treatments or to restore or replace damaged tissues and organs [3–5]. It holds the promise of sustainable development due to ever-going improvement in biomaterials and implies the procedure of fusing scaffolds, molecules, and cells that are biologically active into functional tissues. The ultimate goal is to completely monitor, create a functional structure/support to repair, preserve, or improve damaged tissues or entire organs and to implement “enhanced and sustainable quality of life (QOL) with health” as stated in the prime goal of the World Health Organization (WHO) [6,7]. In this field, two primary approaches are used to generate engineered tissues. Primar- ily, scaffolding is used as a cell supporting system for seeding cells in vitro, and further cells Polymers 2021, 13, 1105. https://doi.org/10.3390/polym13071105 https://www.mdpi.com/journal/polymers