Foreign body response, implants

See also Foreign Body Response Implant Studies. 

The first synthetic polyglycoHc acid suture was introduced in 1970 with great success (21). This is because synthetic polymers are preferable to natural polymers since greater control over uniformity and mechanical properties are obtainable. The foreign body response to synthetic polymer absorption generally is quite predictable whereas catgut absorption is variable and usually produces a more intense inflammatory reaction (22). This greater tissue compatibihty is cmcial when the implant must serve as an inert, mechanical device prior to bioresorption. 

Ward WK, Slobodzian EP, Tiekotter KL, Wood MD. The effect of microgeometry, implant thickness and polyurethane chemistry on the foreign body response to subcutaneous implants. Biomaterials 2002, 23, 4185-4192. 

Mou X. Modulation of foreign body response towards implanted microdialysis sampling probes. Ph.D. Dissertation. Rensselaer Polytechnic Institute, 2007. 

Hetrick EM, Prichard HL, Klitzman B, Schoenfisch MH. Reduced foreign body response at nitric oxide-releasing subcutaneous implants. Biomaterials 2007, 28, 4571 -580. 

A possible technique adopted to prevent fibrous capsule formation around the implant is the addition of a tissue intermediary [203,204]. Indeed, if this material has a continuous, interconnected, porous structure (pore diameter >8-10 p-m), macrophages are capable of invading structure voids. Consequently, vascularized tissue can grow in the implant and the foreign body response is avoided as this porous stmcture is able to mimic extracellular matrix. The first example of intermediary tissue use concerns the coating of an implanted catheter by means of a silicone mbber cage [205]. Typically,... 

Onuki, Y., Bhardwaj, U., Papadimitrakopoulos, F., and Burgess, D.J. (2008) A review of the biocompatibility of implantable devices current challenges to overcome foreign body response. Journal of Diabetes Science and Technology, 2 (6), 1003-1015. 

In situ hardening in the body can result in particle release and a change in alkalinity in the surrounding environment. Implantation of a cement that is hardened prior to insertion in the body has revealed a less pronounced foreign body response (Frayssinet et al. 2000). This result may be attributed to the early particle release (Pioletti et al. 2000) or the increase in pH that has been known to trigger an inflammatory response and cell death (Silver et al. 2001). 

The packaging of the pressure transducer is also a problem that needs to be addressed, especially when the transducer is in contact with blood for long periods of time. Not only must the package be biocompatible, but it also must allow the appropriate pressure to be transmitted from the biological fluid to the diaphragm. Thus, a material that is mechanically stable under corrosive and aqueous environments in the body is needed. Chronically implanted objects are usually coated with a fibrous capsule by the body as a part of the foreign body response, and this capsule can exert a force on the pressure sensor that will affect its baseline pressure. Thus, it is important to package pressure sensors with materials that will minimize this encapsulation. 

Inflammation, wound healing, foreign body response, and repair of implant sites are usually considered components of the general soft tissue response to biomaterials or medical devices. The extent or degree and temporal variations in these responses are dictated by the inherent biocompatibility characteristics of the biomaterial or medical device. Factors which may play a role in the soft tissue response include the size. 

Despite promising, the reliability of implantable systems is often undermined by factors like biofouling [100, 101] and foreign body response [102] in addition to sensor drifts and lack of temporal resolution [103]. To minimize such problems. 

The prospects of implantable devices and in particular the metabolic monitoring can only be achieved if they can be readily implanted and explanted without the need for complicated surgery, this sense, for facilitated the implantation, the implantable device should be extremely small, which calls for miniamrization of various functional components, such as electrodes, power sources, signal processing units and sensory elements. This way, miniaturized biosensors can cause less tissue damage and therefore less inflammation and foreign body response [106],... 

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