1.
Generalized ratiometric fluorescence nanosensors based on carbon dots and an advanced chemometric model.
Yan, XF, Chen, ZP, Huang, Y, Kang, C, Yu, RQ
Talanta. 2019;:233-240
Abstract
Probe encapsulated by biologically localized embedding (PEBBLE) has emerged as a new type of sensing technique for complex systems. Generalized ratiometric PEBBLE nanosensors prepared by encapsulating an intensity-based probe and an inert reference dye inside the pores of stable matrix possess advantages of easy synthesis, immunity to interference, lower toxicity, and robustness to variations in probe loading. However, the selection of appropriate reference dyes used in generalized ratiometric PEBBLE nanosensors is a rather difficult task since they should satisfy some stringent requirements. In this contribution, the feasibility of using carbon dots (C-dots) as generic inert references in synthesizing PEBBLE nanosensors was first investigated in detail. And a dual-wavelength monitoring strategy and the quantitative fluorescence model for generalized ratiometric probes (QFMGRP) were adopted to solve the problems brought by the use of carbon dots as inert references. C-dots doped PEBBLE nanosensors (C-PEBBLE nanosensors) for the quantification of NO2- and free Ca2+ were synthesized by encapsulating C-dots and intensity based fluorescence probes (i.e., acriflavine for NO2-, and Rhod-2 for Ca2+, respectively) inside the pores of stable matrix. Experimental results showed that the combination of C-PEBBLEs, the QFMGRP model and the dual-wavelength monitoring strategy achieved accurate quantification of NO2- and the free Ca2+ in real-world samples. Their quantitative results were in good consistence with those determined by HPLC and atomic absorption spectrophotometer, respectively. The strategies proposed in this contribution have generic applicability in the synthesis of PEBBLE nanosensors and their quantitative applications.
2.
Haemophilus ducreyi Seeks Alternative Carbon Sources and Adapts to Nutrient Stress and Anaerobiosis during Experimental Infection of Human Volunteers.
Gangaiah, D, Zhang, X, Baker, B, Fortney, KR, Gao, H, Holley, CL, Munson, RS, Liu, Y, Spinola, SM
Infection and immunity. 2016;(5):1514-1525
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Abstract
Haemophilus ducreyi causes the sexually transmitted disease chancroid in adults and cutaneous ulcers in children. In humans, H. ducreyi resides in an abscess and must adapt to a variety of stresses. Previous studies (D. Gangaiah, M. Labandeira-Rey, X. Zhang, K. R. Fortney, S. Ellinger, B. Zwickl, B. Baker, Y. Liu, D. M. Janowicz, B. P. Katz, C. A. Brautigam, R. S. MunsonJr, E. J. Hansen, and S. M. Spinola, mBio 5:e01081-13, 2014, http://dx.doi.org/10.1128/mBio.01081-13) suggested that H. ducreyi encounters growth conditions in human lesions resembling those found in stationary phase. However, how H. ducreyi transcriptionally responds to stress during human infection is unknown. Here, we determined the H. ducreyi transcriptome in biopsy specimens of human lesions and compared it to the transcriptomes of bacteria grown to mid-log, transition, and stationary phases. Multidimensional scaling showed that the in vivo transcriptome is distinct from those of in vitro growth. Compared to the inoculum (mid-log-phase bacteria), H. ducreyi harvested from pustules differentially expressed ∼93 genes, of which 62 were upregulated. The upregulated genes encode homologs of proteins involved in nutrient transport, alternative carbon pathways (l-ascorbate utilization and metabolism), growth arrest response, heat shock response, DNA recombination, and anaerobiosis. H. ducreyi upregulated few genes (hgbA, flp-tad, and lspB-lspA2) encoding virulence determinants required for human infection. Most genes regulated by CpxRA, RpoE, Hfq, (p)ppGpp, and DksA, which control the expression of virulence determinants and adaptation to a variety of stresses, were not differentially expressed in vivo, suggesting that these systems are cycling on and off during infection. Taken together, these data suggest that the in vivo transcriptome is distinct from those of in vitro growth and that adaptation to nutrient stress and anaerobiosis is crucial for H. ducreyi survival in humans.