Natural polymers bioactivity

Synthetic products have acquired a negative association due to synthetic food additives, but they show many valuable properties, especially in medical applications. Synthetic polymers are valuable for therapeutic use since they can be produced in a well-defined and controlled fashion, overcoming the greatest setback of natural polymers the batch-to-batch variation. Synthetic polymers often exhibit increased cytotoxicity due to the strong positive charge, but since they can be freely modified in order to introduce desired properties, their biocompatibility can be improved, for example by incorporation of biodegradable linkers and bioactive functionalities. ... 

Physical and chemical modifications to increase electrospun polyester hydrophihcity and surface scaffold functionalization with ECM proteins, peptides, or other bioactive molecules are some examples of posttreatments in use [16]. Another strategy to improve the biocompatibihty of the scaffolds is to combine the polyester with a natural polymer or other natural biomolecule to conduct the electrospinning process [17,18]. 

Natural polymers are frequently extracted from human or animal ECM and exhibit inherent bioactivity with sequences which are able to promote cell adhesion. However, these polymers have poor physico chemical properties. Processing is difficult and they present weak mechanical characteristics and a rapid degradation rate [144]. Meanwhile, as explained above, the polyester polymers provide... 

Hydroxyapatite (HA) nanoparticles are osteoconductive bioactive ceramics that can support bone cell adhesion and proliferation and accelerate bone defects healing. HA is typically added to polymeric nanofibers to increase their mechanical strength. HA, often in the form of needle-like nanoparticles, was electrospun in the presence of synthetic biocompatible and biodegradable polymers such as PLA [5, 58-60] and PLA-PEG-PLA [61], natural polymers such as chitosan [62] and collagen [63, 64], and blends of natural and synthetic polymers such as PVA/chitosan [65] and PCL/gelatin [66]. 

Alternatively, the PURs can be synthesised with building blocks containing lateral functionalities which, after the synthesis, can be exploited for the grafting of bioactive molecules such as natural polymers or cell-specific peptides. One example is represented by PURs containing N-Boc serinol units (Park et al., 2011). Park et al. 

Natural polymers such as collagen, elastin, and fibrin make up much of the body s native extracellular matrix (ECM), and they were explored as platforms for tissue engineered constructs [34,47 9]. Polysaccharides such as chitosan, starch, alginate, and dextran were also studied for these purposes. Simultaneously, silk fibroin was widely explored for vascular applications due to its higher mechanical properties in comparison to other natural polymers, such as fibrin [48]. The utilization of natural polymers to create tissue-engineered scaffolds has yielded promising results, both in vitro and in vivo, due in part to the enhanced bioactivity provided by materials normally found within the human body [50]. However, their mechanical response is usually below the required values therefore, synthetic polymers have been explored to achieve the desired properties. 

Beyond the biocompatibility presented by medical grade and novel synthesized bioresorbable PUs, they lack the bioactivity of natural biopolymers such as collagen and elastin. In response to this challenge, many authors have blended PUs with natural polymers to improve the biocompatibility and bioactivity of vascular grafts. Table 15.4 summarizes the mechanical performance of some selected vascular grafts based on PU blends. 

In this chapter, we intend to present the obtaining and properties of new types of nanocomposites based on natural polymer (collagen) and bioactive compounds (natural layered silicate modified with maleic copolymers) which can be used as biomateiial, scaffold for bone tissue regeneration. 

Department of Natural Polymers, Bioactive and Biocompatible Materials, Petru Poni Institute... 

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