The in vivo biodegradation of nylon 6 utilized in a particular IUD.
The particular IUD of this study was composed of a plastic shield and a nylon 6 coated filament tail string. This IUD was unique, in the fact that its tail string was the only one (and has been to date) that consisted of a coated multifilament arrangement. Studies on the tail string have revealed bacteria and debris existing between the outer filaments that are underneath the coating. Other studies have reported that removed devices were found to exhibit an unusually high incidence of breaks in the tail string coating. Studies at the University of Lowell also found that upon examination of devices that had been in vivo for periods of two years or longer, 67% of these devices examined had breaks in the coating of the tail string. Investigations have determined that the design of the tail string was serving as an avenue of transport for the bacteria to bypass the protective cervical mucus barrier and enter the sterile uterine cavity through the breaks in the tail string coating. This mechanism has been suggested to account for the higher frequency of uterine infections associated with this device. Research at the University of Lowell was undertaken to study the degradation of the nylon 6 coating and to determine the in vivo degradation mechanism. The biochemistry of the fluids present in the reproductive tract were carefully documented and the more aggressive ones selected for in vitro trials. The results of the study revealed that the in vivo physical breakdown of the coating may depend upon a series of mechanisms and variables.