A Portable Digital Loop-Mediated Isothermal Amplification Platform Based on Microgel Array and Hand-Held Reader.

Digital polymerase chain reaction (dPCR) has found widespread applications in molecular diagnosis of various diseases owing to its sensitive single-molecule detection capability. However, the existing dPCR platforms rely on the auxiliary procedure to disperse DNA samples, which needs complicated operation, expensive apparatus, and consumables. Besides, the complex and costly dPCR readers also impede the applications of dPCR for point-of-care testing (POCT). Herein, we developed a portable digital loop-mediated isothermal amplification (dLAMP) platform, integrating a microscale hydrogel (microgel) array chip for sample partition, a miniaturized heater for DNA amplification, and a hand-held reader for digital readout. In the platform, the chip with thousands of isolated microgels holds the capability of self-absorption and partition of DNA samples, thus avoiding auxiliary equipment and professional personnel operations. Using the integrated dLAMP platform, λDNA templates have been quantified with a good linear detection range of 2-1000 copies/µL and a detection limit of 1 copy/µL. As a demonstration, the epidermal growth factor receptor L858R gene mutation, a crucial factor for the susceptibility of the tyrosine kinase inhibitor in non-small-cell lung cancer treatment, has been accurately identified by the dLAMP platform with a spiked plasma sample. This work shows that the developed dLAMP platform provides a low-cost, facile, and user-friendly solution for the absolute quantification of DNA, showing great potential for the POCT of nucleic acids.

Point-of-Care Periodontitis Testing: Biomarkers, Current Technologies, and Perspectives.

Periodontitis has become one of the most universal chronic inflammatory diseases worldwide. Subclinical symptom progression, ultimately leading to permanent damage, calls for early diagnosis and long-term monitoring. However, traditional clinical diagnostic methods are complex and expensive, and cannot meet these requirements. Recently, with more biomarkers and the development of new technologies, various point-of-care testing (POCT) platforms have been developed for periodontitis diagnosis and monitoring. These are easy to perform, rapid, low-cost, and are perfectly suited for high-frequency diagnosis of periodontitis at the point-of-care (POC). We summarize existing biomarkers of different periodontitis stages and recent developed POCT platforms (including lab-on-a-chip, paper-based platforms, and chairside tests), discuss their existing challenges and future potential, and provide some inspiration and guidelines for future POC periodontitis testing.

Labeling and long-term tracking of bone marrow mesenchymal stem cells in vitro using NaYF4:Yb(3+),Er(3+) upconversion nanoparticles.

UNLABELLED: Mesenchymal stem cells (MSCs) hold great promise as cell therapy candidate in clinics. However, the underlying mechanisms remain elusive due to the lack of effective cell tracking approaches during therapeutic processes. In this study, we successfully synthesized and utilized NaYF4:Yb(3+),Er(3+) upconversion nanoparticles (UCNPs) to label and track rabbit bone marrow mesenchymal stem cells (rBMSCs) during the osteogenic differentiation in vitro. To improve their biocompatibility and cellular uptake, we modified the UCNPs with negatively-charged poly(acrylic acid) and positively-charged poly(allylamine hydrochloride) in turns (i.e., PAH-PAA-UCNPs). The effect of cellular uptake of UCNPs on the osteogenic differentiation of rBMSCs was systematically evaluated, and no significant difference was found between rBMSCs labeled with UCNPs (concentration range of 0-50µg/mL) and UCNPs-free rBMSCs in terms of cell viability, ALP activity, osteogenic protein expressions and production of mineralized nodules. Moreover, the PAH-PAA-UCNPs at a concentration of 50µg/mL exhibited the highest biocompatibility and stability, which could well track rBMSCs during the osteogenesis process. These results would provide a positive reference for the application of these lanthanide-doped UCNPs as fluorescent nanoprobes for stem cell tracking to further understand the mechanism of stem cell fate in tissue engineering and stem cell therapy. STATEMENT OF SIGNIFICANCE: Upconversion nanoparticles (UCNPs) have attracted increasing attention as alternative probes for tracking various types of cells including stem cells. The reported fluorapatite-based UCNPs with the needle-like morphology showed a little poor performance on stem cell tracking, which was possibly attributed to the low upconversion efficiency and cell labeling efficiency potentially due to nanomaterial composition, crystal structure and shape. Here, we synthesized the positively-charged NaYF4:Yb(3+),Er(3+) UCNPs with hexagonal phase and sphere-like morphology to enhance their upconversion efficiency, biocompatibility and cellular uptake, leading to a successful tracking of rBMSCs in osteogenesis process without impairing cell viability and differentiation capacity. This study provided a necessary reference for the application of UCNPs in stem cell tracking to better understand the mechanism of stem cell fate in tissue engineering, stem cell therapy, etc.