Craniofacial Regeneration—Bone
Vincenzo Guarino, Marco Antonio Alvarez-Pérez in Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Natural polymers, synthetic polymers and ceramics have been successfully investigated to be applied in developing scaffolds. The most common synthetic polymers are poly (a-hydroxy ester) such as Poly (Glycolic Acid) (PGA), Poly (Lactic Acid) (PLA), poly (E-caprolactone) (PCL) and their copolymers. These polymers are decomposed by hydrolysis of the ester bonds, their degradation products are in some cases resorbed through the metabolic pathways and their structures can be tailored by altering their degradation rates. In the case of natural polymers, some examples are alginate, chitosan, starch, cellulose, collagen, silk fibroin and albumin. These polymers are a frequently used option utilized for tissue regeneration applications because they can more closely mimic the ECM and may improve the biological recognition in the growing new tissue.
Evaluation of PCL/Chitosan/Nanohydroxyapatite/Tetracycline Composite Scaffolds for Bone Tissue Engineering
Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon in Tissue Engineering Strategies for Organ Regeneration, 2020
The main materials for fabrication of scaffolds in tissues engineering application are polymers, especially biodegradable polymeric materials. These materials can be divided into two groups, that is, natural-based materials including polysaccharides (starch, alginate, and chitin/chitosan) or proteins (soy, collagen, fibrin and silk). The other one is synthetic polymer such as poly (lactic acid) (PLA), poly (glycolic acid) (PGA), poly (3-caprolactone) (PCL), and poly (hydroxyl butyrate) (PHB). Synthetic polymers have relatively good mechanical strength and their shape and degradation rate can be easily modified. Meanwhile, natural polymers possess many functional groups such as amino, carboxylic and hydroxyl groups that are available for chemical reactions such as hydrolysis, oxidation, reduction, esterification, cross-linking and many others. In addition to various properties such as pseudo plastic behaviour, gelation ability, water binding capacity, biodegradability makes them suitable for tissues engineering application (Ehrenfreund-Kleinman et al. 2006).
Bio-Implants Derived from Biocompatible and Biodegradable Biopolymeric Materials
P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas in Advanced Studies in Experimental and Clinical Medicine, 2021
Cooper et al. [13] have developed polymers with high molecular weights. It also gives high tensile properties and melts processability similar to synthetic polymers. Hence can be used as similar as radiation sterilizable aromatic polyanhydride. Nicholas et al. [6] have developed a new route for the preparation of fluorescent bioconjugates by living radical polymerization using protein-derived macro initiators. These fluorescent bioconjugates can be easily traceable in biological environments, during biomedical assays. Cycloaddition reactions have been explored by Grayson et al. [14] to prepare macrocyclic poly(hydroxyl styrene). The presence of a phenolic hydroxyl group on each repeat unit in the cyclic polymer gives better scope for attachment of bioactive counterparts. The cyclization technique to have a wider application for preparing a wide range of functionalized macrocycles. Smith and coworkers [15] found poly(N-vinylpyrrolidinone) hydrogels functionalized with drug molecules as promising hydrogels for sustained release of drugs over several days.
Emerging PEGylated non-biologic drugs
Published in Expert Opinion on Emerging Drugs, 2019
Eun Ji Park, Jiyoung Choi, Kang Choon Lee, Dong Hee Na
Although PEGylation technology has been well established for the development of improved biopharmaceutical drugs compared with original biologics, relatively little advance has been made on the development of uniform PEG molecule resulting in homogeneous conjugates with a well-defined structure and uniform activity [47]. In most cases, the PEG used for drug development and production is polydisperse, similar to the majority of synthetic polymers. The effect of PEG polydispersity is evident in small molecules, including synthetic peptides (< MW 5 kDa), because the polydisperse nature can be detected by mass spectrometry [23,47,48]. The polydispersity of PEG produces conjugates with different MWs, which may lead to difficulties in chemical characterization and purity control, and in variability in pharmacokinetics and pharmacodynamics of the conjugates [49]. The monodisperse PEG composed of a single oligomer can solve these problems by producing a single molecular conjugate, which allows more complete chemical characterization [23,47].
Development of an omentum-cultured oesophageal scaffold reinforced by a 3D-printed ring: feasibility of an in vivo bioreactor
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Eun-Jae Chung, Hyung Woo Ju, Yeung Kyu Yeon, Ji Seung Lee, Young Jin Lee, Ye Been Seo, Park Chan Hum
Several types of auto or alloplastic circumferential oesophageal substitutes using natural and synthetic materials have been applied for oesophageal replacement [2–4]. Natural biomaterials, including decellularized extracellular matrix (ECM), collagen, chitosan and gelatine derived from animal sources, have been studied due to their excellent biocompatibility and biospecific signals cued from the ECM. Despite promising results in some in vitro or in vivo experiments, problems such as source shortage, low mechanical strength and fast degradation are limitations of these materials. This is where synthetic polymers, such as poly(caprolactone) (PCL), poly(L-lactic acid) (PLLA), poly(lactide-coglycolide), PCL/PLLA, poly(glycolic acid) and poly(L-lactide-co-caprolactone), become attractive materials. In addition to high availability, low cost and ease of design and production, a key advantage of synthetic polymers is that they can be optimized for their specific mechanical properties and applications. However, many synthetic materials have limitations to their hydrophobic and biologically inert surface [2–4].
Responsive polymer conjugates for drug delivery applications: recent advances in bioconjugation methodologies
Published in Journal of Drug Targeting, 2019
Daniel Cristian Ferreira Soares, Caroline Mari Ramos Oda, Liziane Oliveira Fonseca Monteiro, Andre Luis Branco de Barros, Marli Luiza Tebaldi
Proteins, depending on their particular function, provide unique bio-recognition and binding. The critical issues with proteins are low in vivo stability, short half-life due to degradative enzymes in the bloodstream and interactions of several events like proteolysis by enzymes, clearance mechanisms, etc. Proteins, therefore, require repeated intravascular infusions over the course of a given treatment [5–10]. While most synthetic polymers are biocompatible, non-toxic and non-immunogenic; some may have low biodegradability, which causes problems for in vivo applications. However, the chemical and thermal stability of polymers is in general higher than proteins. In this way, polymers and proteins, individually, are generally unable to achieve the adequate properties for biomedical applications [28–30]. Tailor-made protein–polymer conjugates combine the advantages of both the protein and the polymeric components, in which the protein imparts bio-functional properties while the polymer offers good stability, diversity and other useful properties [16,25,31]. The protein–polymer conjugation strategy often yields longer half-life for therapeutic proteins due to reduced renal clearance by decreasing the interaction of protein–receptor binding during endocytosis. Therefore, the conjugation of peptide/protein to a suitable polymer, in addition to increasing the stability and solubility, may also inhibit the conjugate uptake through receptors via the mononuclear phagocytic system (MPS) [32,33]. Figure 1 illustrates some benefits of attaching synthetic polymers to proteins.
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