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The accurate determination of specific biomolecules and their monitoring in complex biological systems will help us understand their role in the body. In comparison with cumulative fluorescent probes, responsive fluorescent probes exhibit a higher level of sensitivity for the detection of biomolecules. Recently, responsive fluorescent probes based on 1,8-naphthalimide have been used widely in the biomedical field because of their excellent luminescence performance. This review focuses on the progress in research on responsive fluorescent probes obtained by modifying the C4-position of 1,8-naphthalimide to achieve biological molecule detection over the last five years. Based on the differences in species, the corresponding recognition groups and responsive probes were classified systematically and thoroughly, and the significance of the probes used specifically for biological molecule detection was discussed. Finally, we discussed the prospect of developing this type of probe, to make it a powerful diagnostic tool in clinical research. [Display omitted] • The research progress of responsive fluorescent probes obtained by modifying the C4-position of 1.8-naphthalimide. • The corresponding recognition groups and responsive probes were classified systematically and in detail. • We also introduced the significance of responsive fluorescent probes in specific biological detection in recent five years. • We discussed the prospect of developing this type of probe, to make it a powerful diagnostic tool in clinical research. [ABSTRACT FROM AUTHOR]

• Two polarity-sensitive fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) with D-A-D structures were accurately synthesized by a simple synthetic method. • The two fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) exhibit good photophysical properties, such as bright fluorescence, large Stokes shift, and resistance to chemical interference. • Both fluorescent probes (Nap-LD-Ⅰ , Nap-LD-Ⅱ) easily penetrate the cell membrane, specifically localize and aggregate in lipid droplets and lysosomes with low cytotoxicity, and yellow and red fluorescent lipid droplets and lysosomes can be observed. • Both fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) were further investigated for the separate targeting of lysosomes and lipid droplets in HepG2 cells. • Both fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) can be used for imaging of zebrafish. Lipid droplets (LDs) and lysosomes, vital subcellular organelles in cells, played irreplaceable roles in the areas involved in the synthesis of cell membranes, the movement of substances and the transfer of energy. Moreover, the imbalance of LDs could cause the occurrence of certain diseases, such as cardiovascular disease, liver cancer, atherosclerosis and diabetes. LDs and lysosomes interact in some biological processes. In this work, two polarity-sensitive fluorescent probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ) were developed and synthesized by simple 1,8-naphthalimide scaffold modifications, which exhibited large Stokes shifts (173 nm and 190 nm), viscosity, pH stability and interference resistance. Notably, they were biocompatible and showed good targeting for bioimaging. LDs, lysosomes in HepG2 cells and zebrafish could be marked by bright yellow and red fluorescence after incubation with probes (NNap-LD-Ⅰ , NNap-LD-Ⅱ). In addition, HepG2 cells were stained for NNap-LD-Ⅰ and NNap-LD-Ⅱ to monitor the corresponding reduction in the number of LDs in starvation-treated cells. Similarly, the targeting of the probes to the lysosomes was diminished during imaging after the cells were treated with chloroquine (CQ), resulting in a reduction in lamellar fluorescence. These remarkable characteristics suggested that the probes NNap-LD-Ⅰ and NNap-LD-Ⅱ were quite efficient fluorescent probes with good visualization of LDs and lysosomes. [ABSTRACT FROM AUTHOR]

As a common polymer, poly (dimethylaminoethyl methacrylate) (PDMAEMA) is mainly used to synthesize medical materials. However, there are few reports about the related polymer fluorescent probes. Moreover, as far as we know, no one has studied the effect of its molecular weight on the performance of polymer probes. In this work, polymer probes (NapNH 2 (1) -PDM (4) , NapNH 2 (1) -PDM (9) , NapNH 2 (1) -PDM (23) , NapNH 2 (1) -PDM (34) ) with different molecular weights were accurately constructed based on 1,8-naphthalimide fluorophore and poly(N , N -dimethylaminoethyl methacrylate) and their photophysical properties were systematically studied. The test results showed that they all showed good photophysical properties. Moreover, the polymer probe NapNH 2 (1) -PDM (23) , which had the best self-assembly effect and good cell permeability, was successfully screened by confocal fluorescence imaging technology. Not only that, the probe NapNH 2 (1) -PDM (23) could also label lysosomes in cells quickly and accurately. Therefore, this work provided important reference to construct relevant polymer probes with good cell permeability in the future. [Display omitted] • A series of polymer probes with different molecular weights were accurately constructed by simple synthesis method. • A series of polymer probes exhibited good photophysical properties. • The polymer probe NapNH 2 -PDM-C could perfectly self-assemble into nanoparticles in water. • The influence of different molecular weights on the cell permeability of polymer probe was studied. • The polymer probe NapNH 2 (1) -PDM (23) could realize rapid and accurate targeted imaging of lysosomes in cancer cells. [ABSTRACT FROM AUTHOR]

The AIE bio-probes have attracted extensive attention because of their good brightness, long-term in situ retention ability, photostability and low cytotoxicity. Recently, the transformation of ACQ to AIE has become very popular, which is very important for the further development of AIE probes. Herein, a series of novel dyes (NR-Lyso-Ⅰ , NR-Lyso-Ⅱ , NR-Lyso-III , NR-Lyso-IV) were designed and synthesized. It was found that alkylation of 4-aminonaphthalimide could achieve the transformation of the dye from ACQ to AIE effect due to the growth of carbon chain. Moreover, the AIE probe NR-Lyso-IV exhibited dual-state emission (DSE) and large Stokes shift (＞100 nm), excellent selectivity, photostability, and low cytotoxicity, which was able to simultaneous visualize the lipid droplets (LDs) and lysosomes of HeLa cells and zebrafish. [Display omitted] • A series of low cytotoxicity dyes (NR-Lyso-Ⅰ, NR-Lyso-Ⅱ, NR-Lyso- III , NR-Lyso- IV) were designed and synthesized based on 4- bromo-1, 8-naphthalimide by a simple synthetic method. • The experimental results showed that the alkylation of 4-aminonaphthalimide could transformation of the probe from ACQ to AIE effect. Not only that, the length of the alkyl chain could affect the emission of probes in water. • The AIE probe NR-Lyso- IV exhibited good photophysical properties, such as dual-state emission (DSE), large Stokes shift (more than 100 nm), high fluorescence quantum yield, good photostability and selectivity. • The AIE probe NR-Lyso- IV was able to simultaneously visualize the LDs and lysosomes in HeLa cells with different fluorescence intensities. • The AIE probe NR-Lyso- IV could also be used for zebrafish imaging. The AIE bio-probes have attracted extensive attention because of their good brightness, long-term in situ retention ability, photostability and low cytotoxicity. Recently, the transformation of ACQ to AIE has become very popular, which is very important for the further development of AIE probes. Herein, a series of novel dyes (NR-Lyso-Ⅰ , NR-Lyso-Ⅱ , NR-Lyso-III , NR-Lyso-IV) were designed and synthesized. It was found that alkylation of 4-aminonaphthalimide could achieve the transformation of the dye from ACQ to AIE effect due to the growth of carbon chain. Moreover, the AIE probe NR-Lyso-IV exhibited dual-state emission (DSE) and large Stokes shift (＞100 nm), excellent selectivity, photostability, and low cytotoxicity, which was able to simultaneous visualize the lipid droplets (LDs) and lysosomes of HeLa cells and zebrafish. [ABSTRACT FROM AUTHOR]