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Researchers Aljaž Kavčič, MSc., Rok Podlipec, PhD, Ana Krišelj, MSc., Andreja Jelen, PhD and Assist. Prof. Matjaž Humar, PhD in collaboration with a colleague from the Faculty of Mechanical Engineering, University of Ljubljana have published a paper titled Intracellular biocompatible hexagonal boron nitride quantum emitters as single-photon sources and barcodes in the journal Nanoscale.

In this work, they demonstrate single-photon emission from hexagonal boron nitride (hBN) color centers embedded inside live cells and their application to cellular barcoding. The emission from live cells was observed as multiple diffraction-limited spots, which exhibited excellent single-photon characteristics with high single-photon purity of 0.1 and superb emission stability without photobleaching or spectral shifts over several hours. Due to different emission wavelengths and peak widths of the color centers, they were employed as barcodes. Each barcode can exist in one out of 470 possible distinguishable states and a combination of a few barcodes per cell can be used to uniquely tag virtually an unlimited number of cells. The barcodes developed here offer some excellent properties, including ease of production by a single-step procedure, biocompatibility and biodegradability, emission stability, no photobleaching, small size and a huge number of unique barcodes, while, due to the single photon emission, presented concepts could in future be extended to quantum-limited sensing and super-resolution imaging.

Mimoza Naseska, PhD, and Assist. Prof. Matjaž Humar, PhD, from the Department of Solid State Physics F5, in collaboration with colleagues from CENN Nanocenter, Imperial College London, and the Faculty of Mathematics and Physics, University of Ljubljana, have published an article titled Non-contact Monitoring of Glucose Concentration and pH by Integration of Wearable and Implantable Hydrogel Sensors with Optical Coherence Tomography in the journal Optics Express.

Optical coherence tomography (OCT) is a noninvasive imaging technique with large penetration depth into the tissue, but limited chemical specificity. By incorporating functional co-monomers, hydrogels can be designed to respond to specific molecules and undergo reversible volume changes. In this study, we present implantable and wearable biocompatible hydrogel sensors combined with OCT to monitor their thickness change as a tool for continuous and real-time monitoring of glucose concentration and pH. The results demonstrate the potential of combining hydrogel biosensors with OCT for non-contact continuous in-vivo monitoring of physiological parameters.

Figure: pH-sensitive hydrogel film for wound monitoring. a) The graph shows the deswelling of the film as a response to increasing pH of the solution. b) OCT B-scan of the hydrogel film located below a finger patch (upper right) and of the surrounding area with no hydrogel film (lower right). The arrows on the top right image indicate the location of the hydrogel film. The upper left image shows the location of the patch and the rectangle on the lower left image indicates the location of the hydrogel film. c) OCT B-scan of the pH sensitive film located below one layer of gauze and one layer of bandage, shown on the photo. The arrows indicate the location of the hydrogel film which is clearly visible on the OCT scan. d) OCT B-scan of the pH sensitive film located below two layers of gauze and one layer of bandage. The arrows indicate the location of the hydrogel film. The increasing number of covering layers reduces the visibility of the hydrogel under OCT.