An Infusion and Pressure System to Measure Hydraulic Conductivity at a Microscale Level

In studies on nervous tissues, researchers have investigated the relationship between tracer distributions, infusion pressure, flow rate, and tissue properties to optimize and implement infusion techniques [1]. Intratumoral infusion studies have also measured pressure gradients in vitro and determined how drug delivery depends on intrinsic tissue structures [2]. Measuring pressure gradients allows for the calculation of tissue transport properties such as hydraulic conductivity. This property is necessary for modeling extracellular flow and convective transport through tissues. However, it remains a challenge to measure in vivo pressure gradients due to difficulties in measuring small changes in pressure over short distances and the invasive nature of these experiments. Porous media models of infusion predict exponential decay of the pressure profile in tissues [3], but experimental studies to validate these results in biological tissue or hydrogels are lacking. In this study, we measured the pressure within a hydrogel at different distances from an infusion source. The measured pressure gradient was used to estimate hydraulic conductivity of the hydrogel. Eventually, the developed infusion-pressure testing system may be used to characterize hydraulic conductivity of biological tissues.