Bioresorbable Nanostructured Chemical Sensor for Monitoring of pH Level In Vivo

Here, the authors report on the manufacturing and in vivo assessment of a bioresorbable nanostructured pH sensor. The sensor consists of a micrometer-thick porous silica membrane conformably coated layer-by-layer with a nanometer-thick multilayer stack of two polyelectrolytes labeled with a pH-insensitive fluorophore. The sensor fluorescence changes linearly with the pH value in the range 4 to 7.5 upon swelling/shrinking of the polymer multilayer and enables performing real-time measurements of the pH level with high stability, reproducibility, and accuracy, over 100 h of continuous operation. In vivo studies carried out implanting the sensor in the subcutis on the back of mice confirm real-time monitoring of the local pH level through skin. Full degradation of the pH sensor occurs in one week from implant in the animal model, and its biocompatibility after 2 months is confirmed by histological and fluorescence analyses. The proposed approach can be extended to the detection of other (bio)markers in vivo by engineering the functionality of one (at least) of the polyelectrolytes with suitable receptors, thus paving the way to implantable bioresorbable chemical sensors.

Automated summary

This study presents a bioresorbable nanostructured pH sensor that can measure local pH levels in real time. The sensor is composed of a micrometer-thick porous silica membrane coated with a nanometer-thick multilayer stack of polyelectrolytes labeled with a pH-insensitive fluorophore. It has high stability, reproducibility, and accuracy, and can continuously operate for over 100 hours. In vivo experiments on mice confirmed the real-time monitoring of pH levels through the skin. The sensor degrades completely within one week and exhibits good biocompatibility after 2 months.