This paper presents the latest progress on quantitative, in vivo, transcutaneous glucose sensing using surface enhanced spatially offset Raman spectroscopy (SESORS). Silver film over nanosphere (AgFON) surfaces were functionalized with a mixed self-assembled monolayer (SAM) and implanted subcutaneously in Sprague-Dawley rats. The glucose concentration was monitored in the interstitial fluid of six separate rats. The results demonstrated excellent accuracy and consistency. Remarkably, the root mean square error of calibration (RMSEC) (3.6 mg/dL) and the root mean square error of prediction (RMSEP) (13.7 mg/dL) for low glucose concentration (< 80 mg/dL) is lower than the current International Organization Standard (ISO/DIS 15197) requirements. None of the commercially available glucose sensing techniques can achieve enough accuracy during hypoglycemic episodes. Additionally, our sensor demonstrated functionality up 17 days after implantation, including 12 days under the laser safety level for human skin exposure with only one time calibration. Therefore, our SERS based sensor shows promise for the challenge of reliable continuous glucose sensing systems for optimal glycemic control.

Surface-enhanced spatially offset Raman spectroscopy (SESORS) is a label-free vibrational spectroscopy that has the potential for in vivo imaging. Previous SESORS experiments have been limited to acquiring spectra using SERS substrates implanted under the skin or from nanoparticles embedded in tissue. Here we present SESORS measurements of SERS active nanoparticles coated with a Raman reporter molecule (nanotags) acquired, for the first time, through bone. We demonstrate the ability of SESORS to measure spectra through various thicknesses (3-8 mm) of bone. We also show that diluted nanotag samples (~2 × 10(12) particles) can be detected through the bone. We apply a least-squares support vector machine analysis to demonstrate quantitative detection. It is anticipated that these through-bone SESORS measurements will enable real-time, non-invasive spectroscopic measurement of neurochemicals through the skull, as well as other biomedical applications.

In addition to conductivity, recent evidence suggests that adhesive, self-healing, and antibacterial properties are also important aspects of wearable force sensors. However, preparation of hydrogel with these combined aspects in a facile strategy is still a challenge. In this paper, a simple method is proposed to obtain adhesive, conductive, self-healing, and antibacterial chitosan−polyoxometalate (POM) hydrogel. First, silicotungstic acid (SiW) was added into a chitosan solution to form a chitosan−silicotungstic acid (CS/ SiW) physical cross-link network. Second, the CS/SiW−poly(acrylamide) (PAM) double-network hydrogels were fabricated by the in situ polymerization of acrylamide (AM). The CS/SiW-PAM hydrogel indicated excellent repeatable adhesive capacity on the surface of various materials. The CS/SiW-PAM hydrogel also displayed highly sensitive conductivity upon strain. Moreover, the CS/SiW-PAM hydrogel had outstanding self-healing and antibacterial properties. As a result, it is envisioned that the present work will broaden the path for development of POM-based functional soft materials for various applications.

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