Combination with Synthetic Polymers

Two of the most commonly used synthetic polymers in combination with HA are polyethylene glycol (PEG) and poly(lactic-co-glycolic acid) (PLGA). Hybrid hydrogels of PEG and HA can be formed by combining methacrylated HA with acrylated PEG via photopolymerisation [44]. HA has also been combined with an amine-terminated PLGA-PEG diblock copolymer. The -COOH groups of HA can be activated with l-ethyl-3-(3-dimethylaminopropyl) 

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This chapter will introduce polymer systems containing either naturally occurring maaomolecules (polysaccharides, proteins, DNA) or their subunits (bioanalogous molecules, amino acids, short peptides and peptide derivatives, polypeptides, polynucleotides), respectively. The natural building blocks can be connected by covalent bonds or by self-assembly and either can be used alone (see, e.g.. Section 5.4) or in combination with synthetic polymer units (biohybrids). Alternatively the building block itself may be a hybrid of a natural and synthetic molecule (bioconjugate cf. Section 3.5), as, for instance, a PEG-peptide conjugate. 

As described above, scaffolds made of HA alone demonstrate potential for use in cartilage regeneration. However, HA has also been combined with synthetic polymers, which provide the ability to fine tune the properties of the scaffold, as well as with other natural materials. This section provides several examples of these hybrid materials systems. 

Wood fibres and wood flour are frequently used in combination with synthetic polymers, both as general fillers or together with adhesives. TG and DSC were applied to study the thermal behaviour and crystallinity of the new blends and various other physical methods for stiffness, brittleness, moisture content and further characteristics. 

This is truly the age of the macromolecule. Essentially every important problem and advance comprises polymers, including synthetic (such as carbon nanotubes) and biological (such as the human genome and proteins). There are more chemists working with synthetic polymers than in all of the other areas of chemistry combined. 

Interest in detergent products derived from renewable resources and with better biodegradability has driven evaluation of oxidized sugars and starches as builders or co-builders in detergents.113 Builders and co-builders complex calcium and magnesium ions in hard water to prevent sealing or deposits due to precipitation of insoluble carbonate salts. In current powder detergents, the builders are usually zeolites used in combination with polycarboxylate polymers derived from synthetic acrylic-maleic acid copolymers.114... 

Knowledge about natural metal chelates induced in the first stage researdi work for artificial low molecular metal dielates. Secondly experience about the important environmental effect of natural polymers like apoprotein lead to research on the combination of synthetic polymers with a metal chelate. By intensive investigation in these fields new combinations of metal dielate/polymer may be found, even with unknown properties. 

Traditional composite panels are made from veneers and from mat-formed eomposites bonded by adhesive. More recently wood has also been combined (eompression moulded or extruded) with synthetic polymers, e.g. thermoplastic polymers, to make wood-polymer composites (WPC). WPC products have been growing very rapidly in the recent years, especially in the deeking market, where Woleott (2004) observed that their market share has grown from 2% in 1997 to 14% in 2003. Further, much research work has explored the use of fibre-reinforced polymers (FRP) to enhance the structural performance of engineered wood eomposites, ealled FRP-wood hybrid composites (Dagher et ai, 1998 Shi, 2002). 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

The combination of sohd phase peptide synthesis with polymer chemistry has proven to be a versatile method for the preparation of polymer-peptide hybrids. Introduction of native ligation methods even allows the synthesis of polymer modified polypeptides and proteins via an entire organic chemistry approach. In the field of polymer chemistry—besides the advances in NCA polymerization, which will be discussed by others and is therefore not part of the scope of this review—controlled radical polymerization has been shown to be a robust technique, capable of creating well-defined biofunctional polymer architectures. Through protein engineering, methods have been estabhshed that enable the construction of tailor-made proteins, which can be functionalized with synthetic polymer chains in a highly defined manner. 

Ito et al (16) used combinatorial bioengineering methods to produce new biomaterials based on amino acids, nucleic acid, and non-natural components. In a different way, Silvestri et al (7) produced biomaterials by combining enzymes with synthetic polymers some examples were combinations of a-amylase with poly(vinyl alcohol), poly(ethylene glycol), and poly(hydroxyethyl methacrylate). Jong (9) used soy protein as a reinforcement material in elastomers and observed an increase in the rubber modulus. 

Generally speaking, synthetic polymers have better mechanical strength than natural polymers. They allow researchers more flexibihty in the design and development of new products, but challenge them with the difficult task of minimising cytotoxicity in such products. As a result, they are usually used in combination with natural polymers or are modified or functionalised to improve their biocompatibUity. 

Many polymeric materials used in biomedical research are biohybrids, meaning a combination of synthetic polymers and biological macromolecules. In addition, the interaction of a biomacromolecule like a peptide and any synthetic polymer is of high interest for potential application, for example, if there are conformational changes or denaturation of the proteins in contact with a polymeric surface and, thus, specific characterization tools not only for the synthetic polymers are of need but also for biomacromolecules. Therefore, in the following, specific techniques are described for the characterization of polypeptides as an example for a typical biological macromolecule. 

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