Biocompatibility inflammatory response

After 7 days, the acute inflammatory response at the implantation site was evaluated. Bisphenol A resulted in a moderate level of irritation at the implantation site and was clearly the least biocompatible test substance. Tyrosine derivatives containing the benzyloxycar-bonyl group caused a slight inflammatory response, while all other tyrosine derivatives produced no abnormal tissue response at all. These observations indicate that tyrosine dipeptide derivatives, even if fully protected, are more biocompatible than BPA, a synthetic diphenol. ... 

Historically, in vivo biocompatibility has been qualitatively assessed by histological evaluation of explanted devices.6 The presence or absence of specific inflammatory and fibrotic cell types and the degree and duration of the incidence of these cells at the implant site can be correlated to arelative degree of success or failure in terms of tissue compatibility. However, this common implant, sacrifice, explant, and evaluate single-time-point-per-animal approach is quite limited in assessment of time-depen-dent phenomena (e.g., direct assay of molecular and cellular mediators) associated with the progression of the inflammatory response and the development of the FBR. 

The synthetic polymer Nation is an anionic, inert polymer that has hydrophilic and hydrophobic properties. Nation is composed of perfluorosulfonic acid and has shown to increase the lifetime of sensors and to decrease the inflammatory response in the short term and decrease interferents (believed to be due to the anionic property). Nation can be applied as an outer coating to sensors through a dip coating or spin coating procedure to entrap the enzyme and improve biocompatibility of the... 

Polyurethanes have also been employed as outer sensor membranes. Yu et al. evaluated the biocompatibility and analytical performance of a subcutaneous glucose sensor with an epoxy-enhanced polyurethane outer membrane.15 The membrane was mechanically durable and the resulting sensors were functional for up to 56 days when implanted in the subcutaneous tissue of rats. Despite the improved sensor lifetime, all of the polyurethane-coated sensors were surrounded by a fibrous capsule, indicating an enduring inflammatory response that is undesirable due to the aforementioned effects on analytical sensor performance. To date, the clinical success of most passive approaches has been rather limited. It is doubtful that one passive material alone will be capable of imparting long-term (i.e., weeks to months) biocompatibility for in vivo use due to the extremely dynamic nature of the wound environment. 

Elastomers of silicone are widely used as biomaterials. In general, silicone elastomers have excellent biocompatibility, inducing only a limited inflammatory response following implantation. In fact, until very recently, it was assumed that silicones were almost completely inert in biological systems. It is now known, however, that certain silicone polymers can provoke inflammatory and immune responses. The biological response to implanted silicone, and the variability of that response among individuals, is the subject of considerable debate and interest. 

Polypropylene fumarate (PPF) has been in development since the mid-1990s as an injectable, absorbable bone cement with tissue engineering potential. In a 5-week in vivo study in rats, a PPF-based composite crosslinked with N-vinylpyrrolidinone showed good biocompatibility with bone ingrowth and no inflammatory response. Peter and co-workers provide an extensive review of the early development of PPF composite materials, including information about its synthesis, crosslinking, degradation, and... 

Studies in which resin-modified glass-ionomers were placed in the teeth of monkeys confirmed that there were issues of biocompatibility with these materials [77,78]. In a number of cases, pulps showed distinct inflammatory responses. However, these were of limited duration and the effects disappeared within a week or two, and there appeared to be no long-term damage [77,78]. These results are consistent with the known pattern of HEMA release from resin-modified glass-ionomers. 

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