We report a multicolor ECL device based on closed bipolar electrode (BPE) for the visualized sensing of prostate-specific antigen (PSA) in human blood serum. As the emission color of concomitant electrochemiluminophores is potential resolved, similar to a three-electrode system, selective excitation of ECL could be achieved by tuning the interfacial potential at the poles of BPE. Via modulating the resistance of BPE, multicolor ECL emission of [Ru(bpy)] and [Ir(ppy)] mixture using tripropylamine (TPrA) as the co-reactant was observed at the anode and the principle was elaborated. The concept was utilized to the quantification of clinical biomarkers with the color variation. A PSA concentration dependent silver bridge was constructed in the gap of the BPEs as an electric conductivity modulator. On the basis of a multicolor BPE-ECL device, the cutoff values (4.0 and 10.0 ng/mL) of human PSA could be recognized with naked eyes by the green-yellow-red ECL emission changing. As the first multicolor ECL device in biological analysis, BPE may raise the application of potential-resolved ECL to a new level.

In the work, we showed that the use of nanoemitters (tip dimension <1 μm, typically ∼100 nm) could dramatically reduce the nonspecific metal adduction to peptide or protein ions as well as improve the matrix tolerance of electrospray ionization mass spectrometry (ESI-MS). The proton-enriched smaller initial droplets are supposed to have played a significant role in suppressing the formation of metal adduct ions in nanoemitters. The proton-enrichment effect in the nanoemitters is related to both the exclusion-enrichment effect (EEE) and the ion concentration polarization effect (ICP effect), which permit the molecular ions to be regulated to protonated ones. Smaller initial charged droplets generated from nanoemitters need less fission steps to release the gas-phase ions; thus, the enrichment effect of salt was not as significant as that of microemitters (tip dimension >1 μm), resulting in the disappearing of salt cluster peaks in high mass-to-charge (m/z) region. The use of nanoemitters demonstrates a novel method for tuning the distribution of the metal-adducted ions to be in a controlled manner. This method is also characterized by ease of use and high efficiency in eliminating the formation of adduct ions, and no pretreatment such as desalting is needed even in the presence of salt at millimole concentration.

In this work, a synchronized polarization induced electrospray ionization (SPI-ESI) method is developed and applied for the analysis of single-cell samples. In SPI-ESI, periodic alternating current square wave voltage (AC-SWV) is applied to induce the bipolar spray and both positive-ion and negative-ion mass spectra are obtained through one measurement by synchronizing the mode of mass analyzer with the bipolar spray process. Compared with conventional nanoelectrospray ionization (nESI, flow rate< 1000 nL/min), ultralow spray flow rate (pico-electrospray ionization, pESI, flow rate < 1000 pL/min) is achieved in SPI-ESI without loss of its sensitivity. The decrease of flow rate prolongs the MS signal duration from single-cell samples to acquire ms(2) data for components determination. To our knowledge, this is the first time to successfully achieve comprehensive analysis of single-cell samples by combining both positive-ion and negative-ion mass spectra. Ultimately, 86 components are profiled from single Allium cepa cells and 94 components are profiled from single PC-12 cells.

It is a great challenge to design a drug delivery system with a controlled manner, especially one triggered by an exclusive endogenous disease marker and with an easily tracked release process. Herein, we developed a drug delivery platform of carbon dots which were connected to a stem-loop molecular beacon loaded with doxorubicin and polyethylene glycol modified folic acid. Such a platform enables one to release drugs on demand under the stimuli of endogenous microRNA-21, and turn on the fluorescence of carbon dots and doxorubicin, which allows one to monitor the drug release process. The intracellular experiment indicated that folic acid could mediate endocytosis of the nanocarrier, and the overexpressed endogenous microRNA-21 served as a unique key to unlock the drug nanocarrier by competitive hybridization with the molecular beacon, which finally resulted in fluorescence recovery and realized a chemotherapeutic effect within human breast cancer cells. The nanocarrier may have potential application in personalized treatment of different cancer subtypes in which the corresponding miRNAs are overexpressed.

Three endogenous biothiols in single cells were simultaneously quantified by plasmonic Raman probes and quantitative principal component analysis (qPCA).