Poly inflammatory reactions

The tissue reaction in vivo to implanted PHB films and medical devices was studied. In most cases, a good biocompatibility of PHB was demonstrated. In general, no acute inflammation, abscess formation, or tissue necrosis were observed in tissue surrounding of the implanted PHB materials. In addition, no tissue reactivity or cellular mobilization occurred in areas remote from the implantation site [13, 16, 31, 71]. On the one hand, it was shown that PHB elicited similar mild tissue response as PLA did [16], but on the other hand, the use of implants consisting of poly lactic acid, polyglicolic acid, and their copolymers is not without a number of sequelae related with the chronic inflammatory reactions in tissue [81-85]. 

In general, polymers of the poly(a-hydroxy acids) group undergo bulk degradation. The molecular weight of the polymer starts to decrease upon placement in an aqueous media. When molecular chains are reduced to a certain small size, they can freely diffuse out of the polymer matrix [75]. The mass loss is accompanied by the release of acidic by-products. In vivo, massive release of such acidic by-products results in inflammatory reactions, a serious clinical drawback well documented in literature [76-78]. Therefore, it is important that the scaffold-cell construct is constantly exposed to sufficient quantities of neutral culture media, especially during the period when the mass loss of the polymer matrix occurs [79]. 

Bioresorbable composites combine a bioresorbable polymer (PLLA, poly(glycolic) acids and poly(butyric) acids) with HAP particles or of resorptive calcium phosphate. In order to guarantee a successful combination of calcium phosphates with a bioresorbable polymer, it is important to adapt the resorption of the two constituents to avoid inflammatory reactions due to the release of ceramic particles. 

Researchers at Rutgers University have developed biocompatible polymers that degrade into nonsteroidal anti-inflammatory drugs. For example, the reaction of two equivalents of benzyl salicylate and one equivalent of sebacoyl chloride forms a poly(anhydride ester) called PolyAspirin, which hydrolyzes to salicylic acid (an anti-inflammatory agent) and sebacic acid, which is excreted. This technology can perhaps be used for localized drug delivery at specific sites of injury. What is the structure of PolyAspirin ... 

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