Biofouling tissues

Wisniewski N, Klitzman B, Miller B, Reichert WM. Decreased analyte transport through implanted membranes differentiation of biofouling from tissue effects. Journal of Biomedical Materials Research 2001, 57, 513-521. 

Flow-Based Systems Needle-type sensors with a fluid flowing over the sensor tip seem to resist biofouling and extend sensor lifetime.31 There are numerous methods that have been investigated for flow-based sensors, such as microperfusion systems,75 microdialysis,76 77 and ultrafiltration.78 Reduced fouling was found with an open microflow system where slow flow of protein-free fluid over the sensor surface at the implant site is effected.73 Different from the other flow-based sensors, the open microflow is controlled by the subcutaneous tissue hydrostatic pressure and does not require a pump. 

The clinical utility of electrochemical sensors for continuous glucose monitoring in subcutaneous tissue has been limited by numerous challenges related to sensor component and biocompatibility-based failures.1,2 Sensor component failures include electrical failure, loss of enzyme activity, and membrane degradation,3 4 while examples of biocompatibility-based failures include infection, membrane biofouling (e.g., adsorption of small molecules and proteins to the sensor surface), and bbrous... 

The effect of this subtle difference in device function can be seen when the measured signal in the presence of biofouling is modeled. As a model patient, we considered the transient response of an individual with basal insulin provided after each of the three daily meals. Blood glucose dynamics predicted by Sorensen was corrected for diffusion to subcutaneous tissue using the mass transport model of Schmidtke et al.24 25 Figure 11.1 shows a model comparison between the sensor response of an electrochemical sensor and an optical sensor with an assumed... 

The major problem that has plagued these kinds of implantable biosensors is the gradual decrease in sensitivity and in some cases a complete loss of function within just hours of implantation. Biofouling, oxygen limitation, electrochemical interference and GOD inactivation have been considered as explanations of this behaviour. For instance, a tissue reaction to the sensor implantation may result in a limitation in the blood supply to the tissue surrounding the probe and thus in a lower availability of glucose and oxygen. 

A semi-permeable membrane will shield sensor elements from mechanical trauma, and from the harsh environment of the tissue, including attack from cells and their reactive oxygen species, and protein and platelet deposition (biofouling). 

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