Silanized carbon dot-based thermo-sensitive molecularly imprinted fluorescent sensor for bovine hemoglobin detection

Bio(sensors) based on molecularly imprinted polymers and silica materials used for food safety and biomedical analysis: Recent trends and future prospects

In recent decades, analytical techniques have increasingly focused on the precise quantification. Achieving this goal has been accomplished with conventional analytical approaches that typically require extensive pretreatment methods, significant reagent usage, and expensive instruments. The need for rapid, simple, and highly selective identification platforms has become increasingly pronounced. Molecularly imprinted polymer (MIP) has emerged as a promising avenue for developing advanced sensors that can potentially surpass the limitations of conventional detection methods. In recent years, the application of MIP-silica materials-based sensors has garnered significant attention owing to their distinctive characteristics. These types of probes hold a distinct advantage in their remarkable stability and durability, all of which provide a suitable sensing platform in severe environments. Moreover, the substrate composed of silica materials offers a vast surface area for binding, thereby facilitating the efficient detection of even minuscule concentrations of targets. As a result, sensors based on MIP-silica materials have the potential to be widely applied in various industries, including medical diagnosis, and food safety. In the present review, we have conducted an in-depth analysis of the latest research developments in the field of MIPs-silica materials based sensors, with a focus on succinctly summarizing and elucidating the most crucial findings. This is the first comprehensive review of integration MIPs with silica materials in electrochemical (EC) and optical probes for biomedical analysis and food safety.

Development of Highly Sensitive Fluorescent Sensors for Separation-Free Detection and Quantitation Systems of Pepsin Enzyme Applying a Structure-Guided Approach

Two fluorescent molecularly imprinted polymers (MIPs) were developed for pepsin enzyme utilising fluorescein and rhodamine b. The main difference between both dyes is the presence of two (diethylamino) groups in the structure of rhodamine b. Consequently, we wanted to investigate the effect of these functional groups on the selectivity and sensitivity of the resulting MIPs. Therefore, two silica-based MIPs for pepsin enzyme were developed using 3-aminopropyltriethoxysilane as a functional monomer and tetraethyl orthosilicate as a crosslinker to achieve a one-pot synthesis. Results of our study revealed that rhodamine b dyed MIPs (RMIPs) showed stronger binding, indicated by a higher binding capacity value of 256 mg g-1 compared to 217 mg g-1 for fluorescein dyed MIPs (FMIPs). Moreover, RMIPs showed superior sensitivity in the detection and quantitation of pepsin with a linear range from 0.28 to 42.85 µmol L-1 and a limit of detection (LOD) as low as 0.11 µmol L-1. In contrast, FMIPs covered a narrower range from 0.71 to 35.71 µmol L-1, and the LOD value reached 0.34 µmol L-1, which is three times less sensitive than RMIPs. Finally, the developed FMIPs and RMIPs were applied to a separation-free quantification system for pepsin in saliva samples without interference from any cross-reactors.

Nanomaterials for Fluorescent Detection of Hemoglobin

Hemoglobin plays a vital role in a series of biological activities. Abnormal levels of hemoglobin in blood are associated with many clinical diseases. Therefore, development of simple and accurate methods for sensing hemoglobin is of considerable significance. The blowout advancement in nanotechnology has urged the use of different types of fluorescent nanomaterials for hemoglobin assay. The past decades have witnessed the rapid progress of fluorescent nanosensors for hemoglobin assay. In the review, the sensing principles of fluorescent nanomaterials for sensing hemoglobin were briefly discussed. The advances of fluorescent nanosensors for detection of hemoglobin were further highlighted. And the sensing performance of fluorescent nanosensors versus traditional detection approaches was compared. Finally, the challenges and future directions of fluorescent nanomaterials for detection of hemoglobin are discussed. The review will arouse much more attention to the construction of hemoglobin sensors and facilitate rapid development of fluorescent nanosensors of hemoglobin.

Bovine Serum Albumin Molecularly Imprinted Electrochemical Sensors Modified by Carboxylated Multi-Walled Carbon Nanotubes/CaAlg Hydrogels

In this paper, sodium alginate (NaAlg) was used as functional monomers, bovine serum albumin (BSA) was used as template molecules, and calcium chloride (CaCl2) aqueous solution was used as a cross-linking agent to prepare BSA molecularly imprinted carboxylated multi-wall carbon nanotubes (CMWCNT)/CaAlg hydrogel films (MIPs) and non-imprinted hydrogel films (NIPs). The adsorption capacity of the MIP film for BSA was 27.23 mg/g and the imprinting efficiency was 2.73. The MIP and NIP hydrogel film were loaded on the surface of the printed electrode, and electrochemical performance tests were carried out by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) using the electrochemical workstation. The loaded MIP film and NIP film effectively improved the electrochemical signal of the bare carbon electrode. When the pH value of the Tris HCl elution solution was 7.4, the elution time was 15 min and the adsorption time was 15 min, and the peak currents of MIP-modified electrodes and NIP-modified electrodes reached their maximum values. There was a specific interaction between MIP-modified electrodes and BSA, exhibiting specific recognition for BSA. In addition, the MIP-modified electrodes had good anti-interference, reusability, stability, and reproducibility. The detection limit (LOD) was 5.6 × 10-6 mg mL-1.

A Review of Sensing Applications of Molecularly Imprinted Fluorescent Carbon Dots for Food and Biological Sample Analysis

Molecularly imprinted fluorescent carbon dots (MI-FCDs) find numerous applications in analytical chemistry due to their outstanding photoluminescent properties and having specific pockets for the recognition of target molecules. Despite significant advances, practical applications of MI-FCDs-based fluorescent sensors are still in their initial stages. Therefore, the topical developments in the synthesis, working, and application of MI-FCDs for sensing various target species (e.g., pharmaceuticals, biomolecules, pesticides, food additives, and miscellaneous species) in food and biological media have been highlighted. Moreover, a careful evaluation has been made to select the best methods based on their performance in terms of analytical parameters. To expand the horizons of this field, important challenges and future directions for developing MI-FCDs for practical use are also presented. This review will highlight important aspects of MI-FCDs-based fluorescent sensors for their applicability in food science, material science, environmental science, nanoscience, and biotechnology.

Constructing hollow ZIF-8/CDs@MIPs fluorescent sensor from Osmanthus leaves to specifically recognize bovine hemoglobin

To develop non-toxic, highly efficient and selective fluorescence sensors was a significance research. In this work, a novel hollow fluorescence sensor was designed with biomass carbon dots (CDs), ZIF-8 and molecularly imprinted polymers (MIPs) via aqueous polymerization. The results demonstrated such unique structure fluorescence sensor exhibited fast response time, excellent stability and highly selectively towards bovine hemoglobin (BHb). Even in a complex environment, the hollow fluorescence sensor (H-ZIF-8/CDs@MIPs) still has a good recognition effect on BHb. Under an optimized condition, the hollow fluorescence sensor was quenched linearly with BHb concentration in the range of 0.058-4.5 μM with the detection limit of 15.6 nM. In addition, a possible quenching mechanism of hollow fluorescence towards BHb was confirmed resonance energy transfer (FRET). In the actual application process, the hollow fluorescence sensor showed a better detection performance towards BHb with the recoveries ranged of 98.6-101.1 %. This work provided a strategy to design green and unique hollow fluorescence sensor for practical application.

Molecularly Imprinted Nanomaterials with Stimuli Responsiveness for Applications in Biomedicine

The review aims to summarize recent reports of stimuli-responsive nanomaterials based on molecularly imprinted polymers (MIPs) and discuss their applications in biomedicine. In the past few decades, MIPs have been proven to show widespread applications as new molecular recognition materials. The development of stimuli-responsive nanomaterials has successfully endowed MIPs with not only affinity properties comparable to those of natural antibodies but also the ability to respond to external stimuli (stimuli-responsive MIPs). In this review, we will discuss the synthesis of MIPs, the classification of stimuli-responsive MIP nanomaterials (MIP-NMs), their dynamic mechanisms, and their applications in biomedicine, including bioanalysis and diagnosis, biological imaging, drug delivery, disease intervention, and others. This review mainly focuses on studies of smart MIP-NMs with biomedical perspectives after 2015. We believe that this review will be helpful for the further exploration of stimuli-responsive MIP-NMs and contribute to expanding their practical applications especially in biomedicine in the near future.

Carbon dot-based molecularly imprinted fluorescent nanopomegranate for selective detection of quinoline in coking wastewater

Quinoline, as a refractory and toxic organic pollutant in coking wastewater, causes great harm to the environment and human health even in trace amount. To realize the selective and sensitive detection of quinoline in coking wastewater, a novel molecularly imprinted fluorescent nanopomegranate with carbon dots (CDs) as seeds and fluorescence source (CD-MIP) was prepared, using quinoline as the template, and N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH792) as the monomer. The preparation and detection conditions of CD-MIP were systematically optimized. The structure and detection performance of CD-MIP were investigated in detail. The resulting CD-MIP exhibits excellent photoluminescence performance, high detection sensitivity, good selectivity and reproducibility towards quinoline. Under the optimized conditions, the fluorescence intensity of CD-MIP shows a satisfying linearity with quinoline concentration in the range of 20-200 mg/L with a detection limit of 6.7 mg/L. Owing to the existence of imprinted cavities that highly match with quinoline, a high imprinting factor (3.46) for CD-MIP was obtained. In addition, CD-MIP represents a greater affinity towards quinoline than towards other analogues, as well as an outstanding anti-interference capability. For trace analysis in real coking wastewater, CD-MIP also gives satisfactory results. Therefore, CD-MIP shows promising application in the selective detection of trace quinoline in wastewater.

Fluorescence sensor based on molecularly imprinted polymers and core-shell upconversion nanoparticles@metal-organic frameworks for detection of bovine serum albumin

A novel strategy for sensing protein was proposed through combining the high selectivity of molecular imprinting technology with the excellent upconversion fluorescence of upconversion nanoparticles (UCNPs) and high specific surface area of metal-organic frameworks (MOFs). Herein, the UCNPs acted as signal reporter and MOFs were introduced to increase the rate of mass transfer. The UCNPs@MIL-100 as support material was prepared via a step-by-step method. The imprinted material-coated UCNPs@MIL-100 (UCNPs@MIL-100@MIPs) were obtained by sol-gel technique. The results showed that as the increase of the template protein concentration, the fluorescence intensity of UCNPs@MIL-100@MIPs quenched gradually, and the imprinting factor was 2.90. The linear in the range of 1.00 to 8.00 μM, and the detection limit was 0.59 μM. Therefore, the novel optosensing material is very promising for future applications.

Amino acid-immobilized copper ion-modified carbon-based adsorbent for selective adsorption of bovine hemoglobin

We prepared an amino acid-immobilized copper ion-modified carbon-based adsorbent (C@TA@P@A-Cu) for selective bovine hemoglobin (BHb) adsorption in biological samples. Carbon nanoparticles were used as the matrix, and copper ions were attached to the amino acid-modified carbon nanoparticles as metal chelate complexes via immobilized metal affinity. BSA, Lyz, OVA, and HRP were chosen as reference proteins for further study. Furthermore, the synthesis conditions of adsorbents, SPE conditions, selectivity, competitivity, reproducibility, and reusability were extensively investigated. The results showed that the maximum adsorption capacity of C@TA@P@A-Cu microspheres for BHb under optimal conditions was 673.0 mg g^-1. The addition of a TiO₂ layer with an increased specific surface area of the adsorbent and the addition of poly-l-lysine (PLL) inhibited the adsorbent's binding ability to non-BHb proteins, but chelated Cu²⁺ increased the adsorbent's specific binding ability to BHb. Furthermore, after six adsorption-desorption cycles, the adsorbent has satisfactory reusability with no significant change in adsorption capacity. Furthermore, C@TA@P@A-Cu was successfully used to identify BHb from real blood samples, as confirmed by SDS-PAGE, and it is expected to have potential applications in protein purification and disease diagnosis.

Application progress of magnetic molecularly imprinted polymers chemical sensors in the detection of biomarkers

Specific recognition and highly sensitive detection of biomarkers play an essential role in identification, early diagnosis and prevention of many diseases. Magnetic molecularly imprinted polymers (MMIPs) have been widely used to capture biomimetic receptors for targets in various complex matrices due to their superior recognition ability, structural stability, and rapid separation characteristics, which overcome the existing deficiencies of traditional recognition elements such as antibodies, aptamers. The integration of MMIPs as recognition elements with chemical sensors opens new opportunities for the development of advanced analytical devices with improved selectivity and sensitivity, shorter analysis time, and lower cost. Recently, MMIPs-chemical sensors (MMIPs-CS) have made significant progress in detection, but many challenges and development spaces remain. Therefore, this review focuses on the research progress of the sensor based on biomarker detection and introduces the surface modification of the magnetic support material used to prepare high selective MMIPs, as well as the selective extraction of target biomarkers by MMIPs from the complex biological sample matrix. Based on the understanding of optical sensors and electrochemical sensors, the applications of MMIPs-optical sensors (MMIPs-OS) and MMIPs-electrochemical sensors (MMIPs-ECS) for biomarker detection were reviewed and discussed in detail. Moreover, it provides an overview of the challenges in this research area and the potential strategies for the rational design of high-performance MMIPs-CS, accelerating the development of multifunctional MMIPs-CS.

Synthesis of surface protein-imprinted nanoparticles based on metal coordination and anchored carbon dots for enhanced fluorescence detection

Molecularly imprinted polymers endowed with photo-luminescent properties have attracted wide research interest in many fields such as biological analysis and diseases diagnosis. Herein, we illustrate a versatile method for the construction of surface protein-imprinted nanoparticles based on metal coordination and anchored carbon dots (CDs) for enhanced fluorescence detection of the target protein. As the fluorescent nanosupports for surface imprinting, CDs-attached SiO₂ nanoparticles were synthesized via thiol-ene click chemistry. With histidine (His)-exposed protein as templates, imprinted nanoshells were formed over the nanosupports via copolymerization of a Cu²⁺-chelating monomer and an oligo (ethylene glycol) monomer, hence producing high-quality imprinted cavities because of both the relatively strong coordination and inhibited non-specific binding. Using lysozyme as a model His-exposed template, the imprinted nanoparticles showed fluorescence enhancement while binding the target protein, and exhibited significantly increased specific fluorescence response than the controls without the metal coordination. They achieved a high imprinting factor of 5.8 and a low limit of detection of 10.1 nM. Furthermore, such sensors were applied to determine lysozyme in diluted chicken egg-white samples with satisfactory recoveries at three spiking levels ranging from 97.9 to 101.4%. Human serum albumin was also used as another template protein for preliminary confirming the generality of the presented strategy.

A UCMPs@MIL-100 based thermo-sensitive molecularly imprinted fluorescence sensor for effective detection of β-lactoglobulin allergen in milk products

In this study, a thermo-sensitive molecularly imprinted fluorescence sensor was developed for the specific detection of β-Lactoglobulin (β-LG) allergen in milk products. The metal–organic frameworks (MIL-100) with a high specific surface area was coated on the surface of upconversion micro-particles (UCMPs). As the core, an imprinted polymer layer allowing for swelling and shrinking with response to temperature was prepared, which exhibited high adsorption and mass transfer capabilities for β-LG allergen. The fluorescence intensity of UCMPs@MIL-100@MIP decreased linearly with the concentration of β-LG in the range of 0.1–0.8 mg mL⁻¹, and the limit of detection was 0.043 mg mL⁻¹. The imprinting factor reached 3.415, which indicated that excellent specificity of the UCMPs@MIL-100@MIP for β-LG allergen. In the analysis of β-LG allergen in actual milk samples, the proposed UCMPs@MIL-100@MIP fluorescence sensor produced reliable and accurate results (recovery: 86.0–98.4%, RSD: 2.8–6.8%), closely related to the results of standard HPLC method (correlation coefficient: 0.9949), indicating that its feasibility in the detection of β-LG allergen.

Preparation of carbon-based metal organic framework-modified molecularly imprinted polymers for selective recognition of bovine hemoglobin in biological samples

A carbon-based metal–organic framework-modified molecularly imprinted polymer (C@GI@Cu-MOFs@MIPs) for selective separation and enrichment of BHb.

Cobalt-Iron Double Ion-Bovine Serum Albumin Chelation-Assisted Thermo-Sensitive Surface-Imprinted Nanocage with High Specificity

To develop multifunctional protein imprinted materials, a cobalt-iron double ion-BSA directional chelation-assisted thermo-sensitive surface-imprinted hollow nanocage (Co-Fe@CBMA-MIPs) with excellent specificity is developed on the surface of ZIF-67@Co-Fe in this study by synergizing the advantages of surface imprinting, metal ion chelation, anti-protein adsorption segments, and thermo-sensitive components. Beyond previous research, well-designed multifunctional protein-imprinted materials possess high binding capacity, fast adsorption kinetics, and outstanding selectivity. When the adsorption is carried out at 32 °C, the adsorption capacity of Co-Fe@CBMA-MIPs for BSA reaches 520.35 mg/g within 50 min. The imprinting factor is 8.55. The selectivity factors of Co-Fe@CBMA-MIPs for HSA, Bhb, OVA, and Lyz are 3.72, 6.09, 4.10, and 8.41, respectively. More significantly, Co-Fe@CBMA-MIPs could specifically recognize BSA from mixed proteins and actual samples and exhibit excellent repeated use stability. Based on the above advantages, the development of this research provides an effective means to improve the recognition specificity of molecularly imprinted polymers.

A molecularly imprinted polymer based on MOF and deep eutectic solvent for selective recognition and adsorption of bovine hemoglobin

In this study, a novel kind of imprinted polymers based on metal-organic frameworks (MOF@DES-MIPs) was prepared, using bovine hemoglobin (BHb) as template molecules and deep eutectic solvents (DES) as functional monomers for selective recognition and adsorption of BHb. MOF were used as the substrates to improve the accessibility of imprinted sites and DES as the functional monomers to produce different forces for BHb to help the formation of imprinted sites. Imprinted polymer films were taken to provide analyte selectivity. The MOF@DES-MIPs prepared were characterized and evaluated by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectrometer. We also investigated the influences of BHb concentration and adsorption time on the performance of MOF@DES-MIPs. The maximal adsorption capacity of MOF@DES-MIPs to BHb reached 151.28 mg g^-1, and the MOF@DES-MIPs showed good selectivity and fast adsorption equilibrium, which might offer a novel method for the preparation and research of molecularly imprinted polymers of biomacromolecules. In addition, MOF@DES-MIPs were successfully applied in the selective recognition of BHb from a real bovine blood sample. Graphical abstract.

Fabrication of metal coordination-synergistic magnetic imprinted microspheres based on ligand-free Fe3O4-Cu for specific recognition of bovine hemoglobin

In this work, a synergistic imprinting strategy combined with metal coordination based on ligand-free Fe₃O₄-Cu was proposed to fabricate molecularly imprinted polymers (MIPs) for the recognition and isolation of bovine hemoglobin (BHb) specifically in biological samples. Copper doped magnetic microspheres prepared solvothermally in a one-pot pathway act as both magnetic core and metal affinity substrate. Upon anchoring BHb to Fe₃O₄-Cu through metal coordination, the imprinted layer was formed via dopamine self-polymerization. Profiting from the synergistic effect, the obtained imprinted microspheres exhibited an enhanced adsorption performance with the adsorption capacity of 400.86 mg g^-1, imprinting factor of 11.88, selectivity coefficient above 5.8, superior to most of other reported BHb-MIPs. Furthermore, kinetic adsorption analyses pointed to a chemisorption-limited process as described by the pseudo-second-order model, and the isothermal adsorption analyses implied monolayer adsorption, as described by the Langmuir model. In addition, the resultant magnetic MIPs can be used at least six adsorption-desorption cycles without re-incubation in the metallic salt solution, avoiding secondary environmental pollution. Furthermore, the well-defined materials showed selectivity both in individual protein samples and bovine serum, providing a promising potential in bioseparation.