**1. Introduction**

Biodegradable polymers are often used as packaging materials. However, these polymers can also play an important role in tissue engineering as so called scaffolds (i.e. threedimensional porous structures). The success of these biodegradable scaffolds strongly depends on the reaction of them with their surrounding biological environment. This reaction is mainly governed by the surface features of the scaffold and different approaches have already been tested to change the surface properties of biodegradable polymers. In particular, the research field on the use of non-thermal plasmas for a selective surface modification has known a steep rise. Therefore, this chapter will give an introductory and critical overview on recent achievements in plasma-assisted surface modification of biodegradable polymers. Firstly, we will discuss in short the most commonly biodegradable polymers. Secondly, we will go into more detail about surface modification by a nonthermal plasma and finally we will focus on some examples of plasma-treated biodegradable polymers.

### **2. Biodegradable polymers**

### **2.1 Biomedical applications**

A biodegradable polymer is defined as a polymer that preserves its mechanical strength and other material performances during its practical application, but that is finally degraded to low molecular weight compounds such as H2O, CO2 and other non-toxic byproducts (Ikada & Tsuji, 2000). Next to their use as packaging material, which is not in the scope of this chapter, biodegradable polymers could play a key role in biomedical engineering for a variety of reasons (Ikada & Tsuji, 2000). Firstly, since the polymer degrades, it is clear that a device made of such a polymer can be implanted in the human body without necessitating a second surgery to remove the device (Athanasiou et al., 1998, Middleton & Tipton, 2000). Moreover, this prevented second operation makes the use of biodegradable polymers even more beneficial in other ways. For example, a fractured bone, fixated with a rigid, non-biodegradable stainless steel implant, has an inclination to fracture again when the implant is taken away because during the healing process the bone does not carry sufficient load, since the load is entirely intercepted by the rigid steel implant. This is in contrast to a biodegradable implant which degrades little by little and transfers by degrees the load from the implant to the fractured bone. This gradually movement of the load results in less bone re-fracture (Middleton & Tipton, 2000, Athanasiou et al., 1998).

Secondly, another interesting application field for biodegradable polymers is tissue engineering. This research branch aims to produce completely biocompatible tissues which could be employed to replace damaged or diseased tissues in reconstructive surgery (Djordjevic et al., 2008). Today's focus in this field is the use of so called scaffolds. These scaffolds are 3D artificial matrices that guarantee optimal support and conditions for growth of tissue (Djordjevic et al., 2008). Optimally, these scaffolds should fulfil the following two requirements (Ryu et al., 2005):


Finally, biodegradable polymers can also contribute in controlled drug delivery (Amass et al., 1998). A gradual delivery of antibiotics can be beneficial for the treatment of deep skeletal infections after a surgery, while the healing process of a fractured bone can be enhanced by a delivery in stages of bone morphogenetic proteins (Agrawal et al., 1995, Wang et al., 1990, Ramchandani & Robinson, 1998).
