Chemical Functionalization of Polycarbonate

Rapidly growing interest for discovering new materials and surfaces for biomedical application has attracted various scientific disciplines for understanding cell material interactions [26]. Literatme of biomaterial research has shown that the artificial extracellular microenvironment so-called scaffolds play a pivotal role in the process of regenerating tissues [27]. For tissue engineering applications, mostly the bulk properties of the material are considered for use as implant for a particular tissue type. On the other hand, it is the surface properties of polymer material and not the bulk properties that tune the biocompatibility. Many of the polymers are 

The advantage of the naturally derived surfaces is their inherent biocompatibility. However, inconsistent purity arising from lot-to-lot variabihty and potential contamination of pathogens in cases where the material is obtained from a non-human source are disadvantages. On the other hand, synthetic materials are better to reproduce but they lack biological cues found in natural extracellular matrix. Therefore significant efforts have been made to search for polymer blend with functional groups that can be used to couple bioactive species on the surface. 

Among the various useful polymer materials, recent years have witnessed a strong rise in the use of polycarbonates as a material of choice in biomedical applications. Lee et al. examined the behavior of MG63 osteoblast-like cells cultured on a polycarbonate (PC) membrane surface with different micropore sizes (200 nm-8.0 pm) [29]. Welle et al. described electrospun aliphatic polycarbonate as tailored tissue scaffold, where the photochemical bulk modification indicates the possibility of spatial control of the biodegradation rate [30]. In an earlier section we mentioned the use of track-etched polycarbonate membranes that have been introduced as substrate for perfused cell culture in 3D format [31]. The microscopic cavities of the polymer scaffold provide three-dimensionality and nanoscopic pores provide nourishment to the cell culture from all around. Therefore, it is interesting to develop polycarbonate chemistry so that the desired functional groups and molecules can be introduced to the surface for obtaining cell substrate response. 

The functionalized polycarbonates are mostly prepared by premodification of the monomers or block and copolymerization with other monomers [32-34]. For instance, tyrosine-derived polycarbonate (TyrPCs) are versatile polymer platform that can be tuned to different substrate types by cop olymerization with other monomer types [35,36]. Similarly, pendant amino groups were incorporated into PC chains by polymerization 

Recently, our group has developed a structured polymer scaffold which is made of perforated polycarbonate thin film. The scaffold provides a three-dimensional microenvironment to cell culture and is continuously perfused with the nutrient medium [31]. Therefore, polycarbonate chemistry is of particular interest for our applications with a special focus on the mild reaction conditions. Moreover, most of the methods described above are for post modification of the surface of polycarbonate using aggressive reaction conditions. In this chapter we describe a mild and efficient method for the functionalization of polycarbonate using terminal diamines. 

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