A molecularly imprinted electrochemical sensor based on surface imprinted polymerization and boric acid affinity for selective and sensitive detection of P-glycoproteins

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

A Surface Imprinted Polymer EIS Sensor for Detecting Alpha-Synuclein, a Parkinson's Disease Biomarker

Parkinson's Disease (PD) is a debilitating neurodegenerative disease, causing loss of motor function and, in some instances, cognitive decline and dementia in those affected. The quality of life can be improved, and disease progression delayed through early interventions. However, current methods of confirming a PD diagnosis are extremely invasive. This prevents their use as a screening tool for the early onset stages of PD. We propose a surface imprinted polymer (SIP) electroimpedance spectroscopy (EIS) biosensor for detecting α-Synuclein (αSyn) and its aggregates, a biomarker that appears in saliva and blood during the early stages of PD as the blood-brain barrier degrades. The surface imprinted polymer stamp is fabricated by low-temperature melt stamping polycaprolactone (PCL) on interdigitated EIS electrodes. The result is a low-cost, small-footprint biosensor that is highly suitable for non-invasive monitoring of the disease biomarker. The sensors were tested with αSyn dilutions in deionized water and in constant ionic concentration matrix solutions with decreasing concentrations of αSyn to remove the background effects of concentration. The device response confirmed the specificity of these devices to the target protein of monomeric αSyn. The sensor limit of detection was measured to be 5 pg/L, and its linear detection range was 5 pg/L-5 µg/L. This covers the physiological range of αSyn in saliva and makes this a highly promising method of quantifying αSyn monomers for PD patients in the future. The SIP surface was regenerated, and the sensor was reused to demonstrate its capability for repeat sensing as a potential continuous monitoring tool for the disease biomarker.

Post-imprinting modification of molecularly imprinted polymer for proteins detection: A review

Inspired by protein post-translational modification (PTM), post-imprinting modification (PIM) has been proposed and developed to prepare novel molecularly imprinted polymers (MIPs), which are similar to functionalized biosynthetic proteins. The PIM involves site-directed modifications in the imprinted cavity of the MIP, such as introducing high-affinity binding sites and introducing fluorescent signal molecules. This modification makes the MIP further functionalized and improves the shortcomings of general molecular imprinting, such as single function, low selectivity, low sensitivity, and inability to fully restore the complex function of natural antibodies. This paper describes the characteristics of PIM strategies, reviews the latest research progress in the recognition and detection of protein biomarkers such as lysozyme, prostate-specific antigen, alpha-fetoprotein, human serum albumin, and peptides, and further discusses the importance, main challenges, and development prospects of PIM. The PIM technology has the potential to develop a new generation of biomimetic recognition materials beyond natural antibodies. It can be used in bioanalysis and other multitudinous fields for its unique features in molecule recognition.

Self-assembly flexible SERS imprinted membrane based on Ag nanocubes for selective detection of microcystin-LR

Silver nanocubes monolayer-modified polydimethylsiloxane (Ag NC/PDMS) flexible SERS substrates have been prepared by a three-phase interface self-assembly procedure. The combination of this method with membrane technology brings nanoparticles in close proximity, densely, and regularly arranged in monolayers over a large area, leading to excellent SERS properties. Considering the complexity of practical detection, molecular imprinted polymers (MIPs) were anchored on the surface of SERS substrate and applied to selective detection of microcystin-LR (MC-LR). It is worth mentioning that the SERS imprinted membranes (AP-MIMs) were still clearly detected at a concentration of 0.1 µg·L-1 of MC-LR in drinking water, and the detection limit was as low as 0.0067 µg·L-1. The substrate exhibited excellent uniformity with a relative standard deviation (RSD) of 6.1%. In the presence of interference molecules, AP-MIMs exhibited excellent selectivity for MC-LR. Furthermore, in the spiking and recovery tests of practical lake water samples, the method showed excellent recoveries ranging from 96.47 to 105.31%. It has been demonstrated that the prepared AP-MIMs can be applied to sensitive and specific detection of trace amounts of MC-LR in drinking water.

Construction of the molecularly imprinted adsorbent based on shaddock peel biochar sphere for highly sensitive detection of ribavirin in food and water resources

Ribavirin (RBV) that is not metabolically released into the environment can contaminate the environment and even make organisms resistant to it. Therefore, it is of great significance to establish a simple and effective method for adsorbing RBV in the environment. In this study, a novel biochar-based boronate affinity molecularly imprinted polymers (C@H@B-MIPs) were synthesized. This is the first time that shaddock peel biochar sphere was used as a carrier for specific recognition of RBV. The polymerization conditions were optimized and the binding properties of RBV were studied. Benefiting from the synergistic effect of boronate affinity and surface imprinting, the C@H@B-MIPs showed rapid equilibrium kinetics of 15 min, high adsorption capacity of 18.30 mg g-1, and excellent reusability for RBV. The linear range was 0.05-100 mg L-1, and the detection limit was 0.023 mg L-1. This method was triumphant applied to the selective adsorption of RBV in food and water resources with recovery rates of 81.4-97.7%. This study provides a practical platform for the manufacture of efficient biomass-based adsorbents.

Molecularly Imprinted Polymers Using Yeast as a Supporting Substrate

Molecularly imprinted polymers (MIPs) have gained significant attention as artificial receptors due to their low cost, mild operating conditions, and excellent selectivity. To optimize the synthesis process and enhance the recognition performance, various support materials for molecular imprinting have been explored as a crucial research direction. Yeast, a biological material, offers advantages such as being green and environmentally friendly, low cost, and easy availability, making it a promising supporting substrate in the molecular imprinting process. We focus on the preparation of different types of MIPs involving yeast and elaborate on the specific roles it plays in each case. Additionally, we discuss the advantages and limitations of yeast in the preparation of MIPs and conclude with the challenges and future development trends of yeast in molecular imprinting research.

Biorecognition element-free electrochemical detection of recombinant glycoproteins using metal-organic frameworks as signal tags

Accurate and sensitive determination of recombinant glycoproteins is in great demand for the treatment of anemia-induced chronic kidney disease and the illegal use of doping agents in sports. In this study, an antibody and enzyme-free electrochemical method for the detection of recombinant glycoproteins was proposed via the sequential chemical recognition of hexahistidine (His₆) tag and glycan residue on the target protein under the cooperation interaction of nitrilotriacetic acid (NTA)-Ni²⁺complex and boronic acid, respectively. Specifically, NTA-Ni²⁺ complex-modified magnetic beads (MBs-NTA-Ni²⁺) are employed to selectively capture the recombinant glycoprotein through the coordination interaction between His₆ tag and NTA-Ni²⁺ complex. Then, boronic acid-modified Cu-based metal-organic frameworks (Cu-MOFs) were recruited by glycans on the glycoprotein via the formation of reversible boronate ester bonds. MOFs with abundant Cu²⁺ ions acted as efficient electroactive labels to directly produce amplified electrochemical signals. By using recombinant human erythropoietin as a model analyte, this method showed a wide linear detection range from 0.01 to 50 ng/mL and a low detection limit of 5.3 pg/mL. With the benefits from the simple operation and low cost, the stepwise chemical recognition-based method shows great promise in the determination of recombinant glycoproteins in the fields of biopharmaceutical research, anti-doping analysis and clinical diagnosis.

Immobilized horseradish peroxidase on boric acid modified polyoxometalate molecularly imprinted polymer for biocatalytic degradation of phenol in wastewater: Optimized immobilization, degradation and toxicity assessment

The degradation of phenol from wastewater is crucial for environmental protection. Biological enzymes, such as horseradish peroxidase (HRP), have shown great potential in the degradation of phenol. In this research, we prepared a hollow CuO/Cu2O octahedron adsorbent with a carambola matrix shape through the hydrothermal method. The surface of the adsorbent was modified by silane emulsion self-assembly, where 3-aminophenyl boric acid (APBA) and polyoxometalate (PW9) were combined with silanization reagents and grafted onto the surface. The adsorbent was then molecularly imprinted with dopamine to obtain boric acid modified polyoxometalate molecularly imprinted polymer (Cu@B@PW9@MIPs). This adsorbent was used to immobilize HRP, which served as a biological enzyme catalyst from horseradish. The adsorbent was characterized, and its synthetic conditions, experimental conditions, selectivity, reproducibility, and reusability were evaluated. The maximum adsorption amount of HRP under optimized conditions was 159.1 mg g-1, as determined using high-performance liquid chromatography (HPLC). At pH 7.0, the immobilized enzyme showed a high efficiency of up to 90.0% in removing phenol, after 20 min of reaction with 25 mmol L-1 H2O2 and 0.20 mg mL-1 Cu@B@PW9@HRP. Growth tests of aquatic plants confirmed that the adsorbent reduced harm. Gas chromatography-mass spectrometry (GC-MS) tests revealed that the degraded phenol solution contained about fifteen phenol derivatives intermediates. This adsorbent has the potential to become a promising biological enzyme catalyst for dephenolization.

A Label-Free and Antibody-Free Molecularly Imprinted Polymer-Based Impedimetric Sensor for NSCLC-Cells-Derived Exosomes Detection

In this study, a label-free and antibody-free impedimetric biosensor based on molecularly imprinting technology for exosomes derived from non-small-cell lung cancer (NSCLC) cells was established. Involved preparation parameters were systematically investigated. In this design, with template exosomes anchored on a glassy carbon electrode (GCE) by decorated cholesterol molecules, the subsequent electro-polymerization of APBA and elution procedure afforded a selective adsorption membrane for template A549 exosomes. The adsorption of exosomes caused a rise in the impedance of the sensor, so the concentration of template exosomes can be quantified by monitoring the impedance of GCEs. Each procedure in the establishment of the sensor was monitored with a corresponding method. Methodological verification showed great sensitivity and selectivity of this method with an LOD = 2.03 × 10³ and an LOQ = 4.10 × 10⁴ particles/mL. By introducing normal cells and other cancer cells derived exosomes as interference, high selectivity was proved. Accuracy and precision were measured, with an obtained average recovery ratio of 100.76% and a resulting RSD of 1.86%. Additionally, the sensors' performance was retained at 4 °C for a week or after undergoing elution and re-adsorption cycles seven times. In summary, the sensor is competitive for clinical translational application and improving the prognosis and survival for NSCLC patients.

Novel Dual-Signal SiO2-COOH@MIPs Electrochemical Sensor for Highly Sensitive Detection of Chloramphenicol in Milk

In view of the great threat of chloramphenicol (CAP) to human health and the fact that a few producers have illegally used CAP in the food production process to seek economic benefits in disregard of laws and regulations and consumer health, we urgently need a detection method with convenient operation, rapid response, and high sensitivity capabilities to detect CAP in food to ensure people's health. Herein, a molecularly imprinted polymer (MIP) electrochemical sensor based on a dual-signal strategy was designed for the highly sensitive analysis of CAP in milk. The NiFe Prussian blue analog (NiFe-PBA) and SnS₂ nanoflowers were modified successively on the electrode surface to obtain dual signals from [Fe(CN)₆]^3-/4- at 0.2 V and NiFe-PBA at 0.5 V. SiO₂-COOH@MIPs that could specifically recognize CAP were synthesized via thermal polymerization using carboxylated silica microspheres (SiO₂-COOH) as carriers. When the CAP was adsorbed by SiO₂-COOH@MIPs, the above two oxidation peak currents decreased at the same time, allowing the double-signal analysis. The SiO₂-COOH@MIPs/SnS₂/NiFe-PBA/GCE sensor used for determining CAP was successfully prepared. The sensor utilized the interactions of various nanomaterials to achieve high-sensitivity dual-signal detection, which had certain innovative significance. At the same time, the MIPs were synthesized using a surface molecular imprinting technology, which could omit the time of polymerization and elution and met the requirements for rapid detection. After optimizing the experimental conditions, the detection range of the sensor was 10^-8 g/L-10^-2 g/L and the limit of detection reached 3.3 × 10^-9 g/L (S/N = 3). The sensor had satisfactory specificity, reproducibility, and stability, and was successfully applied to the detection of real milk samples.

Magnetic porous cellulose surface-imprinted polymers synthetized with assistance of deep eutectic solvent for specific recognition and purification of bisphenols

Magnetic porous cellulose molecularly imprinted polymers-based bisphenols have been developed using Fe₃O₄ as the magnetic material, a deep eutectic solvent as the assisted solvent, and N-isopropylacrylamide as the functional monomer. The resulting magnetic porous cellulose molecularly imprinted polymers were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, thermal gravimetric analysis, and Brunauer-Emmett-Teller analysis. Moreover, the adsorption properties of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A, bisphenol F, and bisphenol AF were investigated using static, dynamic, and selective adsorption experiments. The introduction of porous cellulose materials significantly improves the capabilities of the material. The adsorption capacity, mass transfer efficiency, and selectivity of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A were 5.9, 4.0, and 4.4 times those of traditional molecularly imprinted polymers. Moreover, the adsorption stability of the magnetic porous cellulose molecularly imprinted polymers was investigated under different temperature and pH conditions. The adsorption characteristics of the magnetic porous cellulose molecularly imprinted polymers toward the target molecules were investigated using adsorption isotherm, kinetic, and thermodynamic models. Hydrogen bonding is the main interaction formed between the magnetic porous cellulose molecularly imprinted polymers and the target molecules. Magnetic porous cellulose molecularly imprinted polymers have great application value with excellent stability and reusability. Finally, the combination of the magnetic porous cellulose molecularly imprinted polymers and high-performance liquid chromatography or ultra-performance liquid chromatography-mass spectrometry was successfully used for the purification and detection of bisphenols in milk (1.349 ng/mL bisphenol F and 3.014 ng/mL bisphenol AF), canned fruits (1129 ng/mL bisphenol A, 10.11 ng/mL bisphenol F, and 91.87 ng/mL bisphenol AF), and fish (11.91 ng/mL bisphenol AF) samples. Furthermore, the magnetic porous cellulose molecularly imprinted polymer method is more selective, sensitive, and accurate than the traditional precipitation method.