A novel microfluidic picoliter-scale sample introduction approach was developed by combining the spontaneous injection approach with a capillary electrophoresis (CE) system based on a short capillary and slotted-vial array. A droplet splitting phenomenon at the capillary inlet end during the spontaneous sample introduction process was observed for the first time. On the basis of this phenomenon, a translational spontaneous injection approach was established to reduce sample injection volumes to the sub-100 pL range. A versatile high-speed capillary electrophoresis (HSCE) system was built on the basis of this sample injection approach with separation performance comparable to or even better than those reported in microfluidic chip-based CE systems. The HSCE system was composed of a short fused-silica capillary and an automated sample introduction system with slotted sample and buffer reservoirs and a computer-programmed translational stage. The translational spontaneous sample injection was performed by linearly moving the stage, allowing the capillary inlet first to enter the sample solution and then removing it. A droplet was left at the tip end and spontaneously drawn into the capillary by surface tension effect to achieve sample injection. The stage was continuously moved to allow the capillary inlet to be immersed into the buffer solution, and CE separation was performed by applying a high voltage between the buffer and waste reservoirs. With the use of the novel system, high-speed and efficient capillary zone electrophoresis (CZE) separation of a mixture of five fluorescein isothiocyanate (FITC) labeled amino acids was achieved within 5.4 s in a short capillary with a separation length of 15 mm, reaching separation efficiencies up to 0.40 microm plate height. Outstanding peak height precisions ranging from 1.2% to 3.7% RSD were achieved in 51 consecutive separations. By extension of the separation length to 50 mm, both high-speed and high-resolution CZE separation of eight FITC-labeled amino acids could be obtained in less than 21 s with theoretical plates ranging from 163,000 to 251,000 (corresponding to 0.31-0.20 microm plate heights). The present HSCE system also allowed fast chiral separations of FITC-labeled amino acids under micellar electrokinetic chromatography (MEKC) mode within 6.5 s.

Peripheral nerve diseases are significantly correlated with severe fractures or trauma and surgeries, leading to poor life quality and impairment of physical and mental health. Human dental pulp stem cells (DPSCs) are neural crest stem cells with a strong multi-directional differentiation potential and proliferation capacity that provide a novel cell source for nerve regeneration. DPSCs are easily extracted from dental pulp tissue of human permanent or deciduous teeth. DPSCs can express neurotrophic and immunomodulatory factors and, subsequently, induce blood vessel formation and nerve regeneration. Therefore, DPSCs yield valuable therapeutic potential in the management of peripheral neuropathies. With the purpose of summarizing the advances in DPSCs and their potential applications in peripheral neuropathies, this article reviews the biological characteristics of DPSCs in association with the mechanisms of peripheral nerve regeneration.