Does polysaccharide is an idea template selection for glycosyl imprinting?

Monitoring of Medical Wastewater by Sensitive, Convenient, and Low-Cost Determination of Small Extracellular Vesicles Using a Glycosyl-Imprinted Sensor

The monitoring of small extracellular vesicles (sEVs) in medical waste is of great significance for the prevention of the spread of infectious diseases and the treatment of environmental pollutants in medical waste. Highly sensitive and selective detection methods are urgently needed due to the low content of sEVs in waste samples and the complex sample composition. Herein, a glycosyl-imprinted electrochemical sensor was constructed and a novel strategy for rapid, sensitive, and selective sEVs detection was proposed. The characteristic trisaccharide at the end of the glycosyl chain of the glycoprotein carried on the surface of the sEVs was used as the template molecule. The glycosyl-imprinted polymer films was then prepared by electropolymerization with o-phenylenediamine (o-PD) and 3-aminophenylboronic acid (m-APBA) as functional monomers. sEVs were captured by the imprinted cavities through the recognition and adsorption of glycosyl chains of glycoproteins on sEVs. The m-APBA molecule also acted as a signal probe and was then attached on the immobilized glycoprotein on the surface of sEVs by boric acid affinity. The electrochemical signal of m-APBA was amplificated due to the abundant glycoproteins on the surface of sEVs. The detection range of the sensor was 2.1 × 104 to 8.7 × 107 particles/mL, and the limit of detection was 1.7 × 104 particles/mL. The sensor was then applied to the determination of sEVs in medical wastewater and urine, which showed good selectivity, low detection cost, and good sensitivity.

Glycan-specific molecularly imprinted polymers towards cancer diagnostics: merits, applications, and future perspectives

Aberrant glycans are a hallmark of cancer states. Notably, emerging evidence has demonstrated that the diagnosis of cancers with tumour-specific glycan patterns holds great potential to address unmet medical needs, especially in improving diagnostic sensitivity and selectivity. However, despite vast glycans having been identified as potent markers, glycan-based diagnostic methods remain largely limited in clinical practice. There are several reasons that prevent them from reaching the market, and the lack of anti-glycan antibodies is one of the most challenging hurdles. With the increasing need for accelerating the translational process, numerous efforts have been made to find antibody alternatives, such as lectins, boronic acids and aptamers. However, issues concerning affinity, selectivity, stability and versatility are yet to be fully addressed. Molecularly imprinted polymers (MIPs), synthetic antibody mimics with tailored cavities for target molecules, hold the potential to revolutionize this dismal progress. MIPs can bind a wide range of glycan markers, even those without specific antibodies. This capacity effectively broadens the clinical applicability of glycan-based diagnostics. Additionally, glycoform-resolved diagnosis can also be achieved through customization of MIPs, allowing for more precise diagnostic applications. In this review, we intent to introduce the current status of glycans as potential biomarkers and critically evaluate the challenges that hinder the development of in vitro diagnostic assays, with a particular focus on glycan-specific recognition entities. Moreover, we highlight the key role of MIPs in this area and provide examples of their successful use. Finally, we conclude the review with the remaining challenges, future outlook, and emerging opportunities.

An Electrochemiluminescent Sensor Based on Glycosyl Imprinting and Aptamer for the Detection of Cancer-Related Extracellular Vesicles

Cancer-related extracellular vesicles (EVs) are considered important biomarkers for cancer diagnosis because they can convey a large amount of information about tumor cells. In order to detect cancer-related EVs efficiently, an electrochemiluminescence (ECL) sensor for the specific identification and highly sensitive detection of EVs in the plasma of cancer patients was constructed based on dual recognitions by glycosyl-imprinted polymer (GIP) and aptamer. The characteristic glycosyl Neu5Ac-α-(2,6)-Gal-β-(1-4)-GlcNAc trisaccharide on the surface of EVs was used as a template molecule and 3-aminophenylboronic acid as a functional monomer to form a glycosyl-imprinted polymer by electropolymerization. After glycosyl elution, the imprinted film specifically recognized and adsorbed the EVs in the sample, and then the CD63 aptamer-bipyridine ruthenium (Aptamer-Ru(bpy)) was added to combine with the CD63 glycoprotein on the extracellular vesicle's surface, thus providing secondary recognition of the EVs. Finally, the EVs were quantitatively detected according to the ECL signal produced by the labeled bipyridine ruthenium. When more EVs were captured by the imprinted film, more probes were obtained after incubation, and the ECL signal was stronger. Under the optimized conditions, the ECL signal showed a good linear relationship with the concentration of EVs in the range of 9.5 × 102 to 9.5 × 107 particles/mL, and the limit of detection was 641 particles/mL. The GIP sensor can discriminate between the EV contents of cancer patients and healthy controls with high accuracy. Because of its affordability, high sensitivity, and ease of use, it is anticipated to be employed for cancer early detection and diagnosis.

Electrochemical bio- and chemosensors for cancer biomarkers: Natural (with antibodies) versus biomimicking artificial (with aptamers and molecularly imprinted polymers) recognition

Electrochemical (EC) bio- and chemosensors are highly promising for on-chip and point-of-care testing (POST) devices. They can make a breakthrough in early cancer diagnosis. Most current EC sensors for cancer biomarkers' detection and determination use natural antibodies as recognition units. However, those quickly lose their biorecognition ability upon exposure to harsh environments, comprising extreme pH, humidity, temperature, etc. So-called "plastic antibodies," including aptamers and molecularly imprinted polymers (MIPs), are hypothesized to be a smart alternative to antibodies. They have attracted the interest of the sensor research community, offering a low cost-to-performance ratio with high stability, an essential advantage toward their commercialization. Herein, we critically review recent technological advances in devising and fabricating EC bio- and chemosensors for cancer biomarkers, classifying them according to the type of recognition unit used into three categories, i.e., antibody-, aptamer-, and MIP-based EC sensors for cancer biomarkers. Each sensor fabrication strategy has been discussed, from the devising concept to cancer sensing applications, including using different innovative nanomaterials and signal transduction strategies. Moreover, employing each recognition unit in the EC sensing of cancer biomarkers has been critically compared in detail to enlighten each recognition unit's advantages, effectiveness, and limitations.

Sialyl-Tn Antigen-Imprinted Dual Fluorescent Core-Shell Nanoparticles for Ratiometric Sialyl-Tn Antigen Detection and Dual-Color Labeling of Cancer Cells

Sialyl-Tn (STn or sialyl-Thomsen-nouveau) is a carbohydrate antigen expressed by more than 80% of human carcinomas. We here report a strategy for ratiometric STn detection and dual-color cancer cell labeling, particularly, by molecularly imprinted polymers (MIPs). Imprinting was based on spectroscopic studies of a urea-containing green-fluorescent monomer 1 and STn-Thr-Na (sodium salt of Neu5Acα2-6GalNAcα-O-Thr). A few-nanometer-thin green-fluorescent polymer shell, in which STn-Thr-Na was imprinted with 1, other comonomers, and a cross-linker, was synthesized from the surface of red-emissive carbon nanodot (R-CND)-doped silica nanoparticles, resulting in dual fluorescent STn-MIPs. Dual-color labeling of cancer cells was achieved since both red and green emissions were detected in two separate channels of the microscope and an improved accuracy was obtained in comparison with single-signal MIPs. The flow cytometric cell analysis showed that the binding of STn-MIPs was significantly higher (p < 0.001) than that of non-imprinted polymer (NIP) control particles within the same cell line, allowing to distinguish populations. Based on the modularity of the luminescent core-fluorescent MIP shell architecture, the concept can be transferred in a straightforward manner to other target analytes.

Cellulose-based hydrogel on quantum dots with molecularly imprinted polymers for the detection of CA19-9 protein cancer biomarker

Molecularly imprinted polymers MIPs were successfully assembled around quantum dots (QDs), for the detection of the protein biomarker CA19-9 associated to pancreatic cancer (PC). These imprinted materials MIP@QDs were incorporated within the cellulose hydrogel with retention of its conformational structure inside the binding cavities. The concept is to use MIPs which function as the biorecognition elements, conjugated to cadmium telluride QDs as the sensing system. The excitation wavelength was set to 477 nm and the fluorescence signal was measured at its maximum intensity, with an emission range between 530 and 780 nm. The fluorescence quenching of the imprinted cellulose hydrogels occurred with increasing concentrations of CA19-9, showing linearity in the range 2.76 × 10 ^-2 - 5.23 × 10 ² U/ml, in a 1000-fold diluted human serum. Replicates of the imprinted hydrogel show a linear response below the cut-off values for pancreatic cancer diagnosis (< 23 U/ml), a limit of detection of 1.58 × 10 ^-3 U/ml and an imprinting factor (IF) of 1.76. In addition to the fact that the imprinted cellulose hydrogel displays good stability and selectivity towards CA19-9 when compared with the non-imprinted controls, the conjugation of MIPs to QDs increases the sensitivity of the system for an optical detection method towards ranges within clinical significance. This fact shows potential for the imprinted hydrogel to be applied as a sensitive, low-cost format for point-of-care tests (PoCTs).

“Out of Pocket” Protein Binding—A Dilemma of Epitope Imprinted Polymers Revealed for Human Hemoglobin

The epitope imprinting approach applies exposed peptides as templates to synthesize Molecularly Imprinted Polymers (MIPs) for the recognition of the parent protein. While generally the template protein binding to such MIPs is considered to occur via the epitope-shaped cavities, unspecific interactions of the analyte with non-imprinted polymer as well as the detection method used may add to the complexity and interpretation of the target rebinding. To get new insights on the effects governing the rebinding of analytes, we electrosynthesized two epitope-imprinted polymers using the N-terminal pentapeptide VHLTP-amide of human hemoglobin (HbA) as the template. MIPs were prepared either by single-step electrosynthesis of scopoletin/pentapeptide mixtures or electropolymerization was performed after chemisorption of the cysteine extended VHLTP peptide. Rebinding of the target peptide and the parent HbA protein to the MIP nanofilms was quantified by square wave voltammetry using a redox probe gating, surface enhanced infrared absorption spectroscopy, and atomic force microscopy. While binding of the pentapeptide shows large influence of the amino acid sequence, all three methods revealed strong non-specific binding of HbA to both polyscopoletin-based MIPs with even higher affinities than the target peptides.

Recent Progress on the Isolation and Detection Methods of Exosomes

Exosomes are known as one of extracellular vesicles, which are found in various body fluids and released by cells. As transport carrier, exosomes participate actively in intercellular communication and reflect their characteristics uniquely to the origin cells. Due to their unique biological physical properties and physiological functions, exosomes are considered to be one of best biomarkers of cancer diagnosis. At the same time, exosomes are potential therapeutic targets and drug delivery carriers. Therefore, the characteristics, functions and analytical methods of exosomes have increasingly attracted wide attention among scientists. In this review, the recent research progress on the basic characteristics and functional applications of exosomes are summarized. Furthermore and importantly, this review focuses on the recent advance in the purification and test methods of exosomes in recent years. Finally, issues pertaining to exosome detection are presented. Based on newly discovered characteristic of exosomes, the opportunities and challenges for future research of the purification and quantitative detection methods are outlined.

Coupled Fluorometer-Potentiostat System and Metal-Free Monochromatic Luminophores for High-Resolution Wavelength-Resolved Electrochemiluminescent Multiplex Bioassay

The sensitive simultaneous detection of multiple biomarkers is critical for the early diagnosis of diseases. Electrochemiluminescence (ECL) offers outstanding advantages, e.g., low background, over other optical sensing techniques. However, multiplexed ECL bioassay is hindered not only by the lack of generally available ECL spectrometers but also by the limited number of biocompatible monochromatic ECL luminophores for decades. Herein, we report addressing these issues by re-examination of the recent tabletop spectrofluorometer coupled potentiostat as a high-resolution ECL spectrum acquisition system and using carbon nitrides as monochromatic luminophores. A wavelength-resolved multiplexing ECL biosensor is demonstrated to simultaneously detect CA19-9 and mesothelin, two pancreatic cancer biomarkers, at a single-electrode interface. This work could initiate new opportunities for more general multiplex ECL biosensors with competitive performances.