Synthesis of Carbon Nanodots from Sugarcane Syrup, and Their Incorporation into a Hydrogel-Based Composite to Fabricate Innovative Fluorescent Microstructured Polymer Optical Fibers.

Carbon nanodots (CNDs) are interesting materials due to their intrinsic fluorescence, electron-transfer properties, and low toxicity. Here, we report a sustainable, cheap, and scalable methodology to obtain CNDs from sugarcane syrup using a domestic microwave oven. The CNDs were characterized by infrared spectroscopy, dynamic light scattering, atomic force microscopy, absorption, and emission spectroscopies. The CNDs have 3 nm in diameter with low polydispersity and are fluorescent. A fluorescent hydrogel-CNDs composite was obtained using gelatin polypeptide as the polymeric matrix. The new hydrogel-CNDs composite was incorporated in the cavities of a double-clad optical fiber using an innovative approach that resulted in a microstructured polymer optical fiber with intrinsic fluorescence. This work shows a promising alternative for the fabrication of fluorescent materials since the CNDs synthesis is sustainable and environmentally friendly. These CNDs might substitute the rare-earth and other heavy metals of high cost and toxicity, which are usually incorporated in double-clad fibers for applications on lasers, amplifiers, and spectroscopy.

A modular, reversible sealing, and reusable microfluidic device for drug screening.

Preclinical tests for evaluating potential drug candidates using conventional protocols can be exhaustive and high-cost processes. Microfluidic technologies that can speed up this process and allow fast screening of drugs are promising alternatives. This work presents the design, concept, and operational conditions of a simple, modular, and reversible sealing microdevice useful for drug screening. This microdevice allows for the operation of 4 parallel simultaneous conditions and can also generate a diffusive concentration gradient in sextuplicates. We used laminated polydimethylsiloxane (PDMSLAM) and glass as building materials as proof of concept. The PDMSLAM parts can be reused since they can be easily sterilized. We cultured MCF-7 (Michigan Cancer Foundation-7) breast cancer cells. Cells were exposed to a doxorubicin diffusive concentration gradient for 3 h. They were monitored by automated microscopy, and after data processing, it was possible to determine cell viability as a function of doxorubicin concentration. The reversible sealing enabled the recovery of the tested cells and image acquisition. Therefore, this microdevice is a promising tool for drug screening that allows assessing the cellular behavior in dynamic conditions and the recovery of cells for afterward processing and imaging.