## 6 Biocompatibility and Implant Associated Infections
Finally, there are a plethora of host-specific factors that play significant role in the implant tolerance [156], including genetic predisposition, biomaterial hypersensitivity, chronic diseases, diet to name a few [157,158,159]. Given the multiple materials used for the fabrication of most implantable devices that include polymers, ceramics, metals and composites, respective contributions of different types of degradation fragments should be considered. Both polymer and metallic debris were linked to activation of macrophages and giant cells in the peri-implant area, contributing to tissue loss and third-body accelerated degradation of the implant [160]. In terms of their size distribution, the metallic particles are typically smaller, more uniformly sized and more abundant compared to the polymer fragments. Given their size differences, the metallic particles are more mobile and more easily transferred from the peri-implant space to other tissues and organs, where they can activate host immune cells and trigger of an implant-associated inflammatory reaction in the host. Large, irregularly shaped ultra-high-molecular-weight polymer particles are less mobile, with a tendency to accumulate in tissues close to the implant site. The reactivity of different types of particles is also affected by their size to volume ratio, with metallic debris undergoing faster corrosion as a result of exposure to biological fluids. A comparative _in vitro_ investigation of the inflammatory response of macrophage cell to metallic and ceramic titanium based particles demonstrated the relative inertness of the ceramic TiO\({}_{2}\)_versus_ Ti particles [161]. While notably less reactive than metallic degradation fragments, ceramic particles, e.g., alumina, have been demonstrated to instigate an end-stage inflammatory response [162; 163; 164]. As the case with coatings used to control bacterial adhesion and proliferation, encapsulation can be used to enhance the biocompatibility of the implant surface, improved integration with host tissues, and limit the degradation particles from entering the tissue-biomaterial interface. Recently, a novel biocompatible packaging process for implantable electronic systems is described, combining excellent biocompatibility and hermeticity with extreme miniaturization [165]. In addition to trying to find ways to enhance the stability and biocompatibility of electronic devices when functioning _in vivo_, a recent trend concerns with the development of fully resorbable electronic systems. These systems are specifically designed to remain stable for a pre-defined length of time, during which the implanted device will perform its functions. Once the task is completed, the implantable device will break down under the influence of the physiological environment in which the implant resides. The key competencies this technology aims to achieve are precisely controlled degradation kinetics and cyto- and tissue-compatibility of the degradation by-products. Resorbable devices are particularly useful where the goal of the implantation is not to permanently replace a function, but to provide temporary physical framework and stimulation to enable tissue restoration, medical diagnostics, accurate spatio-temporal delivery of drugs and other molecules. Recently, [PERSON] _et al._ reported on the development and _in vitro_ study involving transient electronic devices based on silicon with a silk substrate [166]. The developed devices had tunable electrical properties and degradation kinetics. Devices comprising of Mg-based inductive coils, resistive doped Si NMs microheaters, and silk based substrate and packaging were suggested as a bioresorbable tool for non-antibiotic thermal therapy to control surgical site infection (Figure 3). It is important to understand, however, that biodegradation behavior of resorbable material is largely affected by its environment.