Prototyping of a Microfluidic Modulator Chip and Its Application in Heart-Cut Strong-Cation-Exchange-Reversed-Phase Liquid Chromatography Coupled to Nanoelectrospray Mass Spectrometry for Targeted Proteomics

Recent advances in microfluidics for single-cell functional proteomics

Single-cell proteomics (SCP) reveals phenotypic heterogeneity by profiling individual cells, their biological states and functional outcomes upon signaling activation that can hardly be probed via other omics characterizations. This has become appealing to researchers as it enables an overall more holistic view of biological details underlying cellular processes, disease onset and progression, as well as facilitates unique biomarker identification from individual cells. Microfluidic-based strategies have become methods of choice for single-cell analysis because they allow facile assay integrations, such as cell sorting, manipulation, and content analysis. Notably, they have been serving as an enabling technology to improve the sensitivity, robustness, and reproducibility of recently developed SCP methods. Critical roles of microfluidics technologies are expected to further expand rapidly in advancing the next phase of SCP analysis to reveal more biological and clinical insights. In this review, we will capture the excitement of the recent achievements of microfluidics methods for both targeted and global SCP, including efforts to enhance the proteomic coverage, minimize sample loss, and increase multiplexity and throughput. Furthermore, we will discuss the advantages, challenges, applications, and future prospects of SCP.

Construction of a microfluidic platform integrating online protein fractionation, denaturation, digestion, and peptide enrichment

Microfluidic system with multi-functional integration of high-throughput protein/peptide separation ability has great potential for improving the identification capacity of biological samples in proteomics. In this paper, a sample treatment platform was constructed by integrating reversed phase chromatography, immobilized enzyme reactor (IMER) and imprinted monolith through a microfluidic chip to achieve the online proteins fractionation, denaturation, digestion and peptides enrichment. We firstly synthesized a poly-allyl phenoxyacetate (AP) monolith and a lysine-glycine-glycine (KGG) imprinted monolith separately, and investigated in detail their performance in fractionating proteins and extracting KGG from the protein digests of MCF-7 cell. The removal percentage of 94.6% for MCF-7 cell protein and the recovery of 90.8% for KGG were obtained. The number of proteins and peptides identified on this microfluidic platform was 2,004 and 8,797, respectively, which was 2.8-fold and 3.0-fold higher than that of untreatment sample. The time consumed by this platform for a sample treatment was about 9.6 h, less than that of conventional method (approximate 13.3 h). In addition, this platform can enrich some peptide fragments containing KGG based on imprinted monolith, which can be served for the identification of ubiquitin-modified proteomics. The successful construction of this integrated microfluidic platform provides a considerable and efficient technical tool for simultaneous identification of proteomics and post-translational modification proteomics information.

Recent Advances in Microfluidics-Based Chromatography—A Mini Review

Microfluidics-based liquid chromatography is based on the miniaturization of the different types of liquid chromatography (LC) systems (e.g., affinity, adsorption, size exclusion, ion exchange) on a microchip to perform on-chip separation of different types of analytes. On-chip chromatography finds applications in genomics, proteomics, biomarker discovery, and environmental analysis. Microfluidics-based chromatography has good reproducibility and small sample consumption. However, the on-chip chromatography fabrication techniques are often more challenging to perform than conventional LC column preparation. Different research groups have attempted to develop different techniques to fabricate microfluidics-based LC systems. In this review, we will summarize the recent advances in microfluidics-based chromatography.