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The number of CD8+ T lymphocytes (CD8 cells) in peripheral blood can directly reflect the immune status of the body and is widely used for auxiliary diagnosis and prognostic evaluation of diseases. There is an urgent need to develop a simple CD8 cell-counting platform to meet clinical needs. Our group designed a paper-based cell-counting method based on a blocking competition strategy. In addition, we developed a time-resolved fluorescence-blocking competitive lateral flow immunoassay (TRF-BCLFIA) for point-of-care CD8 cell counting that functions by measuring europium nanoparticle (EuNP)-labeled CD8 antibody probes that are not captured by CD8 cells, and we indirectly calculated the concentration of CD8 cells in samples. Within 30 min, four operation steps can provide an accurate CD8 cell count for a 75-μL whole-blood sample, and this approach can be implemented on a handheld device. The TRF-BCLFIA reliably quantified CD8 cells in whole-blood samples, in which the assay exhibited a linear correlation (R2 = 0.989) readout for CD8 cell concentrations ranging from 137 to 821 cells/μL. To validate this approach, our newly developed CD8 cell-counting tool was used to assess 33 tumor patient blood samples. The results showed a high consistency with a flow cytometry-based absolute count. This analysis approach is a promising alternative for the costly standard flow cytometry-based tools for CD8 cell counting in tumor patients in community clinics, small hospitals, and low medical resource regions. This technology would deliver simple diagnostics to patients anywhere in the world, regardless of geography or socioeconomic status. [Display omitted] • We developed a CD8 cell-counting tool that called time-resolved fluorescence-blocking competitive lateral flow immunoassay. • The probes labeled CD8 antibody was europium nanoparticle (EuNP). • Within 30 min, the TRF-BCLFIA reliably quantified CD8 cells in whole-blood samples with a good a linear correlation. • The TRF-BCLFIA showed a high consistency with a flow cytometry-based absolute count. [ABSTRACT FROM AUTHOR]

SO 2 and its derivatives (bisulfite/sulfite) play crucial roles in several physiological processes. Therefore, development of reliable analytical methods for monitoring SO 2 and its derivatives in biological systems is very significant. In this paper, a FRET-based two-photon fluorescent turn-on probe, A-HCy , was proposed for specific detection of SO 2 derivatives through the bisulfite/sulfite-promoted Michael addition reaction. In this FRET system, an acedan (2-acetyl-6-dialkylaminonaphthalene) moiety was selected as a two-photon donor and a hemicyanine derivative served as both the quencher and the recognition unit for bisulfite/sulfite. A-HCy exhibited excellent selectivity and rapid response to HSO 3 − with a detection limit of 0.24 μM. More importantly, probe A-HCy was first successfully applied in two-photon fluorescence imaging of biological SO 2 derivatives in living cells and tissues, suggesting its great potential for practical application in biological systems. [ABSTRACT FROM AUTHOR]