Construction of a Carcinoembryonic Antigen Surface-Enhanced Raman Spectroscopy (SERS) Aptamer Sensor Based on the Silver Nanorod Array Chip

Carcinoembryonic antigen (CEA) is a cancer-related tumor marker, which is commonly used for preventive screening, auxiliary diagnosis, and recurrence monitoring. Therefore, it is of great significance to develop a new CEA detection method. In this paper, we developed an SERS aptasensor for CEA based on silver nanorod array chip, thiol aptamer, and 4-mercaptophenylboronic acid (4-MPBA). The silver nanorod array chip modified by CEA thiol aptamer (aptamer-SH) was used as SERS capture substrates. Ag@4-MPBA was used as a surface-enhanced Raman spectroscopy (SERS) tag. This proposed SERS aptasensor could detect CEA down to 0.447 pg·mL^-1 with a wide linear range from 1 pg·mL^-1 to 100 ng·mL^-1 (R² = 0.9907). The recovery of the standard addition test for CEA in serum was between 97.25% and 102.67%, and the RSD ≤ 2.52% (n = 3). The sensor has the advantages of good specificity, high sensitivity, and a wide linear range. It provides a new method for the detection of CEA in serum.

A Universal Boronate-Affinity Crosslinking-Amplified Dynamic Light Scattering Immunoassay for Point-of-Care Glycoprotein Detection

Herein, we report a universal boronate-affinity crosslinking-amplified dynamic light scattering (DLS) immunoassay for point-of-care (POC) glycoprotein detection in complex samples. This enhanced DLS immunoassay consists of two elements, i.e., antibody-coated magnetic nanoparticles (MNP@mAb) for target capture and DLS signal transduction, and phenylboronic acid-based boronate-affinity materials as crosslinking amplifiers. Upon the addition of targets, glycoproteins are first captured by MNP@mAb and amplified by target-induced crosslinking stemming from the selective binding between the boronic acid ligand and cis-diol-containing glycoprotein, thereby resulting in a remarkably increased DLS signal in the average nanoparticle size. Benefiting from the multivalent binding and fast boronate-affinity reaction between glycoproteins and crosslinkers, the proposed immunosensing strategy has achieved the ultrasensitive and rapid quantitative assay of glycoproteins at the fM level within 15 min. Overall, this work provides a promising and versatile design strategy for extending the DLS technique to detect glycoproteins even in the field or at POC.

Molecularly Imprinted Polymer-Based Smart Prodrug Delivery System for Specific Targeting, Prolonged Retention, and Tumor Microenvironment-Triggered Release

Prodrug and drug delivery systems are two effective strategies for improving the selectivity of chemotherapeutics. Molecularly imprinted polymers (MIPs) have emerged as promising carriers in targeted drug delivery for cancer treatment, but they have not yet been integrated with the prodrug strategy. Reported here is an MIP-based smart prodrug delivery system for specific targeting, prolonged retention time, and tumor microenvironment-triggered release. 5'-Deoxy-5-fluorocytidine (DFCR) and sialic acid (SA) were used as a prodrug and a marker for tumor targeting, respectively. Their co-imprinted nanoparticles were prepared as a smart carrier. Prodrug-loaded MIP specifically and sustainably accumulated at the tumor site and then gradually released. Unlike conventional prodrug designs, which often require in-liver bioconversion, this MIP-based prodrug delivery is liver-independent but tumor-dependent. Thus, this study opens new access to the development of smart prodrug delivery nanoplatforms.

Preparation of a Sandwich-like Complex "MIPs-Target Molecule-Magnetic SERS Probe" and SERS Determination of Immunoglobulin G

Based on the reversible covalent binding between borates and glycoproteins, we proposed a scheme that can specifically recognize and detect immunoglobulin G (IgG). The application of magnetic materials to enrich SERS probes can provide an enhanced signal and repeatability. The results showed that the prepared sandwich-like complex displayed high sensitivity and excellent selectivity for IgG. The Raman peak intensity showed a good linear relationship in the concentration range of 1 mg/mL - 1 ng/mL. The linear equation was y = 657.93x + 2963.9, R² = 0.996. Parallel testing of this sandwich-like complex proved to have excellent repeatability. This method provided a new possibility for clinical non-immunity and the quantitative detection of IgG.

Orthogonal dual molecularly imprinted polymer-based plasmonic immunosandwich assay: A double characteristic recognition strategy for specific detection of glycoproteins

Sensitive and specific detection methods are critical to the detection of glycoproteins. Immunoassay has been a powerful tool for this purpose, in which antibodies or their mimics particularly molecularly imprinted polymers (MIPs) are used for specific recognition. Epitope and glycan are two structure features of a glycoprotein. However, immunoassays based on simultaneous recognition towards the two characteristics have been scarcely explored so far. Herein we present a new strategy called orthogonal dual molecularly imprinted polymer-based plasmonic immunosandwich assay (odMIP-PISA). It relies on double recognition towards a target glycoprotein by two different types of MIPs, using epitope-imprinted gold nanoparticles (AuNPs)-coated slide as capturing substrate to recognize the peptide epitope and glycans-imprinted Raman-active silver nanoparticles as labeling nanotags to recognize the glycans. Carcinoembryonic antigen (CEA), a routinely used marker for colon cancer, was used as a test glycoprotein. The orthogonal double recognition apparently improved the specificity, reducing the maximum cross-reactivity from 14.4% for epitope recognition and 15.2% for glycan recognition to 8.2% for double recognition. Meanwhile, the plasmonic nanostructure-based Raman detection provided ultrahigh sensitivity, yielding a limit of detection of 5.56 × 10^-14 M (S/N = 10). Through measuring the CEA level in human serum, this method permitted differentiation of colon cancer patient from healthy individual. Compared with the traditional immunoassay, odMIP-PISA exhibited multiple advantages, including simplified procedure (6 steps), speed (30 min), reduced cost, and so on. Therefore, this new approach holds great promise in many applications particularly clinical diagnosis.

Inhibition of HER2-Positive Breast Cancer Growth by Blocking the HER2 Signaling Pathway with HER2-Glycan-Imprinted Nanoparticles

Blocking the HER2 signaling pathway has been an effective strategy in the treatment of HER2-positive breast cancer. It mainly relies on the use of monoclonal antibodies and tyrosine-kinase inhibitors. Herein, we present a new strategy, the nano molecularly imprinted polymer (nanoMIP). The nanoMIPs, imprinted using HER2 N-glycans, could bind almost all HER2 glycans and suppress the dimerization of HER2 with other HER family members, blocking the downstream signaling pathways, thereby inhibiting HER2+ breast cancer growth. In vitro experiments demonstrated that the nanoMIPs specifically targeted HER2+ cells and inhibited cell proliferation by 30 %. In vivo experiments indicated that the mean tumor volume of the nanoMIP-treated group was only about half of that of the non-treated groups. This study provides not only a new possibility to treat of HER2+ breast cancer but also new evidence to boost further development of nanoMIPs for cancer therapy.

Boronate-Affinity Glycan-Oriented Surface Imprinting: A New Strategy to Mimic Lectins for the Recognition of an Intact Glycoprotein and Its Characteristic Fragments

Lectins possess unique binding properties and are of particular value in molecular recognition. However, lectins suffer from several disadvantages, such as being hard to prepare and showing poor storage stability. Boronate-affinity glycan-oriented surface imprinting was developed as a new strategy for the preparation of lectin-like molecularly imprinted polymers (MIPs). The prepared MIPs could specifically recognize an intact glycoprotein and its characteristic fragments, even within a complex sample matrix. Glycan-imprinted MIPs could thus prove to be powerful tools for important applications such as proteomics, glycomics, and diagnostics.