This paper reports on the synthesis and application of biocompatible and sensitive SERS nanoparticles for the study of uptake of nanoparticles into living cells in a microfluidic chip through surface-enhanced Raman spectroscopy (SERS). The nanoparticles were fabricated as beta-cyclodextrin-coated silver nanoparticles (Ag@CD NPs) modified with para-aminothiophenol (p-ATP) and folic acid (FA) on the surface. The p-ATP molecules act as the Raman reporter while the FA tags have high affinity for folate receptors (FR) that are over-expressed on the surface cancerous cells, so that the nanoparticles can enter the cells and be monitored by the Raman reporter. Therefore, the nanoparticles could be utilized not only as cell invaders due to endocytosis but also as a SERS sensitive probe to monitor the effect of FR-targeted drugs such as dihydroartemisinin (DHA) that induce the population change of FR on the membrane of living cells. As a result, we have successfully demonstrated that we are able to employ the Ag@CD@p-ATP@FA NPs to evaluate the number of NPs entering living cells quantitatively and correspondingly the drug effect on cancer cells in a well-controlled way.
Nowadays, researchers are focusing on sorting, characterizing and detecting micron or submicron particles or bacteria in microfluidic chips. However, some contradictions hinder the applications of conventional microfluidic chips, including the low working distance of high resolving power microscopy and the low light transmittance of conventional microfluidic chips. In this paper, a rapid and readily accessible microfluidic fabrication method is presented to realize observation with high magnification microscopy. With the one-step molding process, the interconnections, the thin observation interface of polydimethylsiloxane (PDMS) membrane and microfluidic channels were integrated into an intact PDMS replica. Three kinds of PDMS replicas with different auxiliary beams were designed and optimized by leakage experiments and analytical software. The observation interfaces of a 170 μm thickness PDMS membrane enlarges the application domain of microfluidic chips. By adopting a solution of high magnification observation, microfluidic devices could be applied widely in medical science, biology and material science.
Microfluidic system is widely employed in the detection of environmental contaminants and biological specimens. One of the critical issues which limits the applications of microfluidic chips is the limit of detection of trace specimens. Liquid–liquid extraction is of great importance in the preprocessing in microfluidic devices. In this paper, we developed a real-time fluorescence detection microfluidic chip combined with a microstructure-enhanced liquid–liquid laminar extraction technique, which concentrated the trace compound and realized real-time monitoring. Auxiliary microstructures integrated in the microfluidic chip were applied to increase the extraction efficiency, which was proved by the FEM (finite element method) simulation as well. A common fluorescence probe, Rhodamine 6G (Rh6g), was used in the experiment to demonstrate the performance of the microfluidic system. It revealed that the liquid–liquid laminar extraction combined with auxiliary microstructures of a cross shape was an effective method for enrichment. The efficiency of microstructure-enhanced liquid–liquid extraction was increased by 350% compared to the traditional laminar flow extraction.
The `missing wedge', which is due to a restricted rotation range, is a major challenge for quantitative analysis of an object using tomography. With prior knowledge of the grey levels, the discrete algebraic reconstruction technique (DART) is able to reconstruct objects accurately with projections in a limited angle range. However, the quality of the reconstructions declines as the number of grey levels increases. In this paper, a modified DART (MDART) was proposed, in which each independent region of homogeneous material was chosen as a research object, instead of the grey values. The grey values of each discrete region were estimated according to the solution of the linear projection equations. The iterative process of boundary pixels updating and correcting the grey values of each region was executed alternately. Simulation experiments of binary phantoms as well as multiple grey phantoms show that MDART is capable of achieving high-quality reconstructions with projections in a limited angle range. The interesting advancement of MDART is that neither prior knowledge of the grey values nor the number of grey levels is necessary.
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