In Situ Determination of Sialic Acid on Cell Surface with a pH-Regulated Polymer Enzyme Nanoreactor

Abstract

Sialic acid (SA) is an important monosaccharide that is involved in incurable cancer immunotherapy. However, it is difficult to detect SA in situ using the existing strategy based on the SA-terminated glycopeptide extraction from the cell lysate. The countermeasures of the bottleneck caused by cell disruption and peptide extraction should be designed based on a “cell-surface attachment and controlled enzymolysis” protocol. Herein, a poly­(styrene-co-maleic anhydride-acrylic acid-concanavalin A) (PSM-PAA-ConA) was synthesized and developed as a pH-regulated enzyme nanoreactor after being loaded with sialidase and myoglobin. The nanoreactor showed controllable biocatalysis induced by a cascade enzyme reaction and applied for the in situ detection of SA on a living cell surface. The addition of an acidic solution resulted in a decrease in the size of the nanoreactor and enhancement of its permeability, triggering an “on” state of the SA catalysis. Subsequent pH increase led to increased hydrophilicity of the nanoreactor, increasing its size and resulting in the catalytic “off” state. ConA assisted the cell-surface attachment of the enzyme reactor. Furthermore, SA on the surface of living cancer cells was successfully monitored by the pH-regulated enzyme nanoreactor, demonstrating the feasibility of high specificity in situ analysis for SA. This pH-induced catalytic efficiency control by the enzyme nanoreactor provides a potential platform for functional stimuli-responsive catalytic systems as well as a strategy for in situ analysis of biomolecules on the cell surface.

Electrochemical Evaluation of Tumor Development via Cellular Interface Supported CRISPR/Cas Trans-Cleavage

“…Quartz crystal microbalance method can sensitively detect sialic acid on the surface of red blood cells by using gold nanoparticles for signal amplification [ 46 ]. The surface enhanced Raman method can detect the expression of sialic acid on the surface of single HeLa cells with the usage of silver nanoparticles functionalized with 4-mercaptophenylboric acid and 4-mercaptobenzenitrile to reduce biological interference [ 47 ]; UV-Vis method can in situ detect sialic acid by constructing enzyme nanoreactor on the cell surface which can catalyze the UV color reaction [ 48 ]. Fluorescent nanorods were self-assembled by π - π stacking and hydrophobic effect using 4-(4-(pyren-1-yl) butyramido) phenylboronic acid, and two-photon imaging of sialic acid on the surface of living cells was achieved [ 49 ].…”

Spatially Confined Nanoreactors Designed for Biological Applications

“…Reproduced with permission. [ 103 ] Copyright 2021, American Chemical Society. C) i) The development of a therapeutic nanoreactor using GOx‐loaded polyion complex vesicles (PICsomes) by self‐assembly.…”

Lanthanide Complexes for Tumor Diagnosis and Therapy by Targeting Sialic Acid

“…For the determination of SA, traditional detection methods are divided into four categories: chemical colorimetry, enzyme analysis, , high performance liquid chromatography (HPLC), , and fluorescence spectrophotometry. , Although chemical colorimetry is cost-saving, there are still problems such as poor specificity, cumbersome operation, and large reagent hazards. Enzyme analysis method is highly specific, fast, and accurate, but it is unstable and costly.…”