A unique off-on near-infrared cyanine-based probe for imaging of endogenous alkaline phosphatase activity in cells and in vivo

Abstract

Alkaline phosphatase (ALP) is a class of enzymes that are widely found in various tissues of the human body. It plays important roles in regulating diverse cellular functions. The aberrant levels of serum ALP are implicated in diseases. The development of sensitive and accurate detection tool for evaluating the level changes of ALP in living organisms will be very helpful in the fields of biochemistry, cytology and clinical medicine. Herein, we develop a near-infrared probe (QcyP) for the specific detection of different ALP levels both in different cell lines and in tumor-bearing mice models. The probe is composed of two moieties: a unique heptamethine cyanine fluorophore and a phosphate monoester. ALP can trigger an off-on fluorescence switch via an enzyme-catalyzed cleavage of the phosphate group. The fluorescence regulation mechanism is based on the rearrangement of the conjugated -electron system. The probe exhibits high selectivity and good sensitivity towards ALP. The results demonstrate that the probe QcyP not only can be applied to discriminate the levels of ALP in different cell lines, but also can distinguish the ALP level changes between hepatic tumor mice model and normal mice.

An Activatable AIEgen Probe for High‐Fidelity Monitoring of Overexpressed Tumor Enzyme Activity and Its Application to Surgical Tumor Excision

“…[3f] As shown in Figures S67-S70, cell viability remained high after treatment with the probes for 24 h. The probes caused no noticeable cytotoxicity.T hus,t he ability of DQM-ALP for imaging the activity of endogenous ALP was further investigated in living cells.Human cervical carcinoma cells (HeLa cells) and hepatoma carcinoma cells (HepG-2 cells) were chosen as model cells owing to their overexpression of ALP. [22] Compared to the control group (Figure 3b), obvious fluorescence signal (Figure 3e)w as observed in HeLa cells incubated with DQM-ALP for 0.5 h. This was caused by in situ enzymatic dephosphorylation, which released the nanoaggregates DQM-OH. Similarly,this was also consistently observed in HepG-2 cells treated with DQM-ALP for 0.5 h( Figure S71).…”

Activatable Off‐on Near‐Infrared QCy7‐based Fluorogenic Probes for Bioimaging

“…synthesized a turn‐on fluorescence probe 15 composed of fluorophore QCy7 and ALP recognition group phosphate monoester (Figure 9). [29] Probe 15 can not only detect endogenous ALP activity with high sensitivity and selectivity in living cells, but also can be used to quantify the expression levels of ALP in eight different cell lines. In addition, the organelle colocalization assay showed that the intracellular distribution of the probe was still mainly concentrated in mitochondria.…”

Overview of Optical and Electrochemical Alkaline Phosphatase (ALP) Biosensors: Recent Approaches in Cells Culture Techniques

“…The new probe exhibited high sensitivity to ALP with 10-fold improvement when 2.0 U/mL ALP is added. Gao et al (2018) designed and synthesized a near-infrared fluorescence probe to image and assess endogenous ALP changes in different tumor line cells [79]. The probe contained two parts: heptamethine cyanine as fluorescence modulator and phosphate monester as a response moiety for ALP enzymatic reaction.…”