Foreign-body response biocompatibility

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. 

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. 

CPCs are nontoxic to cells, biocompatible, and osteoconductive. Furthermore, CPCs are biologically active such that they remodel and incorporate in host bone, and thus do not induce a foreign-body response.These biomaterials set at a physiological pH with minimal reaction exotherm, and do not release toxic monomers or solvents.There are two primary classes of CPCs (a)... 

In this animal model for strabismus surgery, 20 Mr ad y-irradiation cross-linked poly (GVGVP), X -poly(GVGVP), presented a biocompatible barrier to the formation of adhesions, caused neither an inflammatory response nor the usual foreign body response of fibrous capsule formation, and appeared to be innocuous, its presence being ignored by the host. 

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. 

The presence of a fibrous layer surrounding the PLA coupons is characteristic of a mild foreign body response. That such a fibrous layer was not formed at the bone/material interface for poly(DTE carbonate) and poly(DTH carbonate) is an important characteristic of these polymers. Intimate contact between bone and implant, even at 48 weeks post-implantation, is a strong indicator of the biocompatibility of the tyrosine-derived polycarbonates. 

A review is given of classic foreign body responses to polymeric drug delivery devices with emphasis on the central nervous system response. In vivo biocompatibility studies of implanted drug carriers are summarised to illustrate the behaviour of different classes of polymers and the methodologies used to evaluate their tolerance. 150 refs. 

Biocompatibility issues concerns over body responses to a foreign material often raise the issues of biocompatibility and safety of an implant (discussed in the next section). 

The foreign body reaction occurring around soft tissue implants and thrombosis on surfaces in contact with blood are the major reactions encountered with implants. Both reactions involve the interaction of cells with the implant, especially in the later stages, and much previous study has therefore emphasized cellular events in the biocompatibility process. However, cells encounter foreign polymer implants under conditions that ensure the prior adsorption of a layer of protein to the polymer interface. The properties of the adsorbed layer are therefore important in mediating cellular response to the material. 

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