Determination of Cancer Cell-Based pH-Sensitive Fluorescent Carbon Nanoparticles of Cross-Linked Polydopamine by Fluorescence Sensing of Alkaline Phosphatase Activity on Coated Surfaces and Aqueous Solution

Abstract

The tumor-specific sensitive fluorescence sensing of cellular alkaline phosphatase (ALP) activity on the basis of host-guest specific and pH sensitivity was conducted on coated surfaces and aqueous states. Cross-linked fluorescent nanoparticles (C-FNP) consisting of β-cyclodextrin (β-CD)/boronic acid (BA) and fluorescent hyaluronic acid [FNP(HA)] were conjugated to fluorescent polydopamine [FNP(pDA)]. To determine the quenching effect of this system, hydrolysis of 4-nitrophenyl phosphate (NPP) to 4-nitrophenol (NP) was performed in the cavity of β-CD in the presence of ALP activated photoinduced electron transfer (PET) between NP and C-FNP. At an ALP level of 30-1000 U/L, NP caused off-emission of C-FNP because of their specific host-guest recognition. Fluorescence can be recovered under pH shock due to cleavage of the diol bond between β-CD and BA, resulting in release of NP from the fluorescent system. Sensitivity of the assays was assessed by confocal imaging not only in aqueous states, but also for the first time on coated surfaces in MDAMB-231 and MDCK cells. This novel system demonstrated high sensitivity to ALP through generation of good electron donor/acceptor pair during the PET process. Therefore, this fluorescence sensor system can be used to enhance ALP monitoring and cancer diagnosis on both coated surfaces and in aqueous states in clinical settings.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure–Property Relationships and Applications

“…enzyme concentrations, inter and intracellular pH difference, biomolecules, etc. ). ,− The externally/internally applied stimuli cause rearrangement in the molecular architecture (ordered-to-disorder or vice versa) at the supramolecular level, leading to change in the luminescence. For example, the green-fluorescent diyne 129 (Chart ) showed a change in color (yellow to red) and fluorescence quenching (a change to black) upon treatment with aniline-derivatives and benzoquinone, respectively .…”

“…The aqueous solution of lyotropic liquid crystals (LLC) based on 130 was found to be clear and highly emissive with varying colors from cyan to red (Figure , panels b and c). In summary, luminescence switching makes the fluorophores suitable candidates for multidisciplinary applications. ,− …”

Strategy for In Situ Imaging of Cellular Alkaline Phosphatase Activity Using Gold Nanoflower Probe and Localized Surface Plasmon Resonance Technique

“…Alkaline phosphatase (ALP), an essential zinc-containing dimeric enzyme that is responsible for phosphate metabolism and catalyzed the hydrolysis of phosphoryl esters in alkaline media, is widely distributed in several tissues throughout the body, particularly concentrated in the bone and liver. − Abnormally elevation of ALP activity in blood is commonly linked to various diseases such as liver diseases and bone disorders, , while low activity of ALP in blood is the sign of hypophosphatasia and some other diseases such as anemia and chronic nephritis . Meanwhile, the ALP activity fluctuates with many cellular events, including transformation, response to toxic injury, and tumor aggressiveness. , Notably, cellular ALP are overexpressed in some malignant tumors, which can be further implicated as a tumor biomarker. − Therefore, the ALP is an important biomarker for clinical diagnosis, and tracking of ALP activity at the cellular level provides valuable information on the cell differentiation and viability to identify the abnormality in cell behaviors. − To date, numbers of approaches have been developed to monitor ALP activity, including chromatography, electrochemistry, surface-enhanced resonance Raman scattering, fluorescence spectra, and colorimetry. − For example, You and co-workers proposed a new inner filter effect-based fluorescent assay for ALP sensing, ALP inhibitor investigation, and cell imaging, in which N-doped carbon dots act as fluorophore and the hydrolysate of ALP as absorber .…”

An Enzyme Cascade-Triggered Fluorogenic and Chromogenic Reaction Applied in Enzyme Activity Assay and Immunoassay

“…As an important hydrolytic enzyme in phosphate metabolism, alkaline phosphatase (ALP, EC 3.1.3.1) can catalyze the hydrolysis and transphosphorylation of a wide variety of phosphate esters in proteins, nucleic acids, and other small molecules. − Thus, ALP has been considered as a significant biomarker in laboratory research and clinic diagnosis of prostatic cancer, bone disease, hepatic dysfunction, diabetes, and so on. − Moreover, ALP is extensively adopted as a marker enzyme in the enzyme-linked immunosorbent assay (ELISA) to produce detectable signals because of its high catalytic activity, mild reaction conditions, broad substrate specificity, good stability, and easy conjugation to antibodies. − Although nature has already evolved a large number of substrates for ALP, ,− there are still many potential substrates with desirable regioselective dephosphorylation sites . To our knowledge, there is no report about an enzyme cascade system that involved participation of ALP accompanied by fluorometric and colorimetric dual-readout signals, which is evidentially probative for the cascade catalysis of the cascaded enzyme, as well as significant for both mechanism research and tailored applications in ELISA.…”