First-Ever Demonstration of Continuous Protein Monitoring in Whole Serum and in-vivo

The continuous monitoring of proteins in complex biological environments presents significant challenges, particularly due to biofouling on sensor surfaces. Due to proteins’ inherently large size, common antifouling methods such as membranes and hydrogels cannot be used because although they inhibit fouling well, they also block the protein of interest. Presented here is the utilization of a mixed charge monolayer to inhibit fouling in electrochemical aptamer sensors, providing a superior solution for real-time protein detection. By employing a combination of positively and negatively charged molecules in the monolayer, we create a dynamic surface that minimizes nonspecific binding while maintaining the aptamer's ability to selectively capture target proteins. The monolayer's effectiveness in reducing biofouling was evaluated through square wave voltammetry (SWV), demonstrating enhanced sensor stability and longevity during extended monitoring periods. Sensors retain greater than 70% of their response even after 2 weeks of operation in whole serum at body temperature. With a platelet derived growth factor (PDGF) aptamer sensing over the range of 1 to 100 nM is achieved with >500 % sensor response. In a rat model, initial multi-hour in-vivo testing demonstrates that large proteins partition into interstitial fluid, and currently multi-day testing is being transitioned into a porcine model. All of these results are further achieved by mimicking the commercially proven success of glucose monitors which is two-fold in design: (1) the working and counter/reference electrodes are fabricated on a needle-like polymer strip that is 400 µm wide and 5 mm long; (2) these aptamer electrode strips are then inserted into the skin using a slotted guide needle which is rapidly retracted leaving the sensor either in the dermis or hypodermis depending upon animal species and desired target tissue. Our findings highlight the potential of this aptamer biosensor strategy to enable the first ever reliable and accurate protein monitoring in both clinical and health and wellness applications. Figure 1