Bioresorbable Nanostructured Chemical Sensor for Monitoring of pH Level In Vivo

Abstract

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.

Wireless and Flexible Optoelectronic System for In Situ Monitoring of Vaginal pH Using a Bioresorbable Fluorescence Sensor

“…Assessment of each preparation step was performed monitoring the changes in the effective optical thickness (EOT) of the PSiO 2 scaffold by Fast Fourier Transformation (FFT) of the reflectance spectra (Figure S1, Supporting Information). [23,30,35] A picture of a PSiO 2 scaffold coated with the fluorescent polyelectrolyte stack on a PDMS slab, i.e., the pH sensor, is shown in Figure 2b.…”

“…The sensor then fully dissolved in additional 4 days with safe byproducts, as we reported previously. [30] We then carried out a series of experiments to investigate the performance of the pH sensor upon repeated bending and twisting cycles. Specifically, we tested the sensor as prepared and after 1, 10, and 100 bending cycles at different curvature radii, namely, 1, 2, and 2.5 cm, the latter being the radius of a commercial vaginal ring; then, we tested it upon 100 twisting cycles.…”

“…More recently, we reported on an implantable PSi fluorescence sensor able to monitor pH in vivo, leveraging a micrometer‐thick porous silica (PSiO 2 ) scaffold conformably coated with a pH‐responsive stack of fluorescent polyelectrolytes. [ 30 ] The sensor was able to perform continuous pH measurements for 4 days, then dissolve in additional 4 days. However, pH measurements were carried out with a benchtop setup featuring a discrete laser as the excitation source, a fiberoptic link to guide the laser light to the sensor and collect the sensor fluorescence, a commercial spectrometer to measure the sensor fluorescence spectrum and measure the peak intensity value.…”

An Ex Vivo Study of Wireless Linkage Distance between Implantable LC Resonance Sensor and External Readout Coil

“…In addition to these state-of-the-art solutions, various wearable and implantable systems with miniature sensors to monitor the body parameters have been developed to record the heart rate [ 10 ], temperature [ 11 , 12 , 13 ], pH [ 13 , 14 , 15 ], pressure [ 16 , 17 ], blood flow [ 18 ], and respiration rates [ 19 , 20 ]. These solutions are flexible [ 21 ], bendable [ 22 ], stretchable [ 23 , 24 , 25 ], and biocompatible, making them suitable for both wearable and implantable applications [ 26 , 27 , 28 ].…”

Dual Optical Nanosensor Based on Ormosil Nanoparticles for Monitoring O2 and pH

“…Fluorescence has high-significance advantages in terms of the precision and accuracy of optical sensors [ 3 , 4 , 5 ]. Different probes have been used for this purpose, including organic fluorophores and polymers [ 6 , 7 , 8 , 9 ]. However, most are not biocompatible and only based on measuring one parameter.…”