Development of Paper-Based Fluorescent Molecularly Imprinted Polymer Sensor for Rapid Detection of Lumpy Skin Disease Virus

Lumpy Skin Disease (LSD) is a notifiable viral disease caused by Lumpy Skin Disease virus (LSDV). It is usually associated with high economic losses, including a loss of productivity, infertility, and death. LSDV shares genetic and antigenic similarities with Sheep pox virus (SPV) and Goat pox (GPV) virus. Hence, the LSDV traditional diagnostic tools faced many limitations regarding sensitivity, specificity, and cross-reactivity. Herein, we fabricated a paper-based turn-on fluorescent Molecularly Imprinted Polymer (MIP) sensor for the rapid detection of LSDV. The LSDV-MIPs sensor showed strong fluorescent intensity signal enhancement in response to the presence of the virus within minutes. Our sensor showed a limit of detection of 101 log10 TCID50/mL. Moreover, it showed significantly higher specificity to LSDV relative to other viruses, especially SPV. To our knowledge, this is the first record of a paper-based rapid detection test for LSDV depending on fluorescent turn-on behavior.

High-performance molecularly imprinted polymers grafted magnetic photonic crystal microspheres for selective enrichment of Ochratoxin A

Development of selective enrichment materials for the accurate analysis of ochratoxin a (OTA) in environmental and food samples is an effective way to protect human health. Here, a molecularly imprinted polymer (MIP) known as plastic antibody was synthesized onto the magnetic inverse opal photonic crystal microsphere (MIPCM) using a low-cost dummy template imprinting strategy targeting OTA. The MIP@MIPCM exhibited ultrahigh selectivity with an imprinting factor of 130, high specificity with cross-reactivity factors of 3.3-10.5, and large adsorption capacity of 60.5 μg/mg. Such MIP@MIPCM was used for selective capture of OTA in real samples which was quantified in combination with high-performance liquid chromatography, giving a wide linear detection range of 5-20,000 ng/mL, a detection limit of 0.675 ng/mL, and good recovery rates of 84-116%. Moreover, the MIP@MIPCM can be produced simply and rapidly and is very stable under different environmental conditions and easy to store and transport, so it is an ideal substitute of biological antibody modified materials for the selective enrichment of OTA in real samples.

Molecularly Imprinted Polymer-Based Luminescent Chemosensors

Molecularly imprinted polymer (MIP)-based luminescent chemosensors combine the advantages of the highly specific molecular recognition of the imprinting sites and the high sensitivity with the luminescence detection. These advantages have drawn great attention during the past two decades. Luminescent molecularly imprinted polymers (luminescent MIPs) towards different targeted analytes are constructed with different strategies, such as the incorporation of luminescent functional monomers, physical entrapment, covalent attachment of luminescent signaling elements on the MIPs, and surface-imprinting polymerization on the luminescent nanomaterials. In this review, we will discuss the design strategies and sensing approaches of luminescent MIP-based chemosensors, as well as their selected applications in biosensing, bioimaging, food safety, and clinical diagnosis. The limitations and prospects for the future development of MIP-based luminescent chemosensors will also be discussed.

Differential Refractometric Biosensor for Reliable Human IgG Detection: Proof of Concept

A new sensing platform based on long-period fiber gratings (LPFGs) for direct, fast, and selective detection of human immunoglobulin G (IgG; Mw = 150 KDa) was developed and characterized. The transducer's high selectivity is based on the specific interaction of a molecularly imprinted polymer (MIPs) design for IgG detection. The sensing scheme is based on differential refractometric measurements, including a correction system based on a non-imprinted polymer (NIP)-coated LPFG, allowing reliable and more sensitive measurements, improving the rejection of false positives in around 30%. The molecular imprinted binding sites were performed on the surface of a LPFG with a sensitivity of about 130 nm/RIU and a FOM of 16 RIU^-1. The low-cost and easy to build device was tested in a working range from 1 to 100 nmol/L, revealing a limit of detection (LOD) and a sensitivity of 0.25 nmol/L (0.037 µg/mL) and 0.057 nm.L/nmol, respectively. The sensor also successfully differentiates the target analyte from the other abundant elements that are present in the human blood plasma.

A microfluidic approach for rapid and continuous synthesis of glycoprotein-imprinted nanospheres

Many strategies have been reported for the preparation of glycoproteins imprinted polymers, but they take a long time and cannot produce imprinted polymers continuously. Herein, a microfluidic synthesis approach was developed to make glycoproteins imprinted nanospheres rapidly and continuously. By using ovalbumin as a model template and a synthesized phenylboronic acid-tagged silane reagent as the functional monomer, the synthetic conditions including the polymerization contents, the flow rate and the microfluidic reactor size were comprehensively studied. Under the optimized conditions, the glycoprotein imprinted nanospheres could be synthesized rapidly (<2 h), and exhibited high specificity with cross-reactivity factors of 1.3 (ovotransferrin), +∞ (horse-radish peroxidase), 5.1 (β-lactoglobulin) and 101 (bovine serum albumin). The kinetic and equilibrium binding behaviors, reusability and potential applications of the glycoprotein imprinted nanosphere were investigated. Such microfluidic synthesis strategy can be easily extended to produce other target glycoproteins imprinted nanospheres, as well as non-glycoproteins by using suitable functional monomers.

Recyclable nanoparticles based on a boronic acid-diol complex for the real-time monitoring of imprinting, molecular recognition and copper ion detection

Molecularly imprinted polymers (MIPs) have now become one of the most remarkable materials in the field of molecular recognition. Although many efforts have been made to study the process and mechanism of molecular imprinting, it has not been possible to monitor the interactions between the template and the growing polymer chains under real-time experimental conditions. The behavior of the template-monomer complex during the whole polymerization process has remained largely unknown. In this work, we introduce a fluorescence technique that allows monitoring of the template-functional monomer complex during an actual imprinting process, as well as the real-time signaling of template binding and dissociation from the imprinted polymer. For the first proof-of-principle, we select Alizarin Red S (ARS) and 4-vinylphenylboronic acid as the template and functional monomer, respectively, to synthesize MIP particles via precipitation polymerization. As the formation of the template-functional monomer complex leads to strong fluorescence emission, it allows the status of the template binding to be monitored throughout the whole reaction process in real time. Using the same fluorescence technique, the kinetics of template binding and dissociation can be studied directly without particle separation. The hydrophilic MIP particles can be used as a scavenger to remove ARS from water. In addition, the MIP particles can be used as a recyclable sensor to detect Cu ions. As the Cu ion forms a stable complex with ARS, it causes ARS to dissociate from the MIP nanoparticles, leading to effective fluorescence quenching. The non-separation analytical method based on fluorescence measurement provides a convenient means to study molecular imprinting reactions and the kinetics of molecular recognition using imprinted polymers. The recyclable nanoparticle sensor allows toxic Cu ions to be detected directly in water in the range of 0.1-100 μM with a recovery of 84-95%.

A simple approach to prepare fluorescent molecularly imprinted nanoparticles

Fluorescent molecularly imprinted polymers (FMIPs) are gaining increasing attention in analytical and medical sciences, particularly silica-based FMIPs due to their low cost, environmentally friendly nature and good biocompatibility. However, at present, silica-based FMIPs are usually prepared through several steps and displayed low selectivity. Here, a simple approach was utilized for preparing silica-based FMIP nanoparticles. The polymerization was initiated by 3-aminopropyltriethoxysilane (APTES), which also acted as the functional monomer in the imprinting system; in addition, to achieve one-pot synthesis, a fluorescent monomer was prepared by a simple reaction between fluorescein isothiocyanate (FITC) and APTES. The as-synthesized FMIP nanoparticles displayed high specificity and fast response time (<1 min) towards the target molecule. Environmental pH and buffer salt could affect the specific recognition behaviors of the FMIP nanoparticles. Such a simple catalyst-free synthetic technique could also be employed for the preparation of FMIP nanoparticles targeting other acidic molecules.

A functional ratio fluorescence sensor platform based on the graphene/Mn-ZnS quantum dots loaded with molecularly imprinted polymer for selective and visual detection sinapic acid

A functional ratio fluorescence sensor based on the molecularly imprinted polymer (MIP) coated double quantum dots (QDs) being composited of Mn-ZnS QDs and silica-coated graphene quantum dots (GQDs@SiO₂) had been established for the sensitive, selective and visual detection of sinapic acid (SA). MIPs@Mn-ZnS/GQDs@SiO₂ was synthesized through a simple one-pot sol-gel reaction, and it exhibited two fluorescence emission peaks with yellow fluorescence of Mn-ZnS QDs at 580 nm and the blue fluorescence of GQDs at 445 nm. SA can selectively enhance the fluorescence of GQDs but quench the Mn-ZnS QDs fluorescence to the MIPs@Mn-ZnS/GQDs@SiO₂. The ratio of fluorescence enhancement to fluorescence reduction is linear with the concentration of SA from 9 to 81 nM with the detection limits of 0.8388 nM (S/N = 3). And the constructed fluorescent probe can also be used to visually detect SA according to the change of color. More importantly, molecular imprinting technique enables the sensors to selectively recognize the SA while other similar structure molecules hardly interfere with the SA determination in the measurement environment. Meanwhile, the fluorescence sensors have the advantages of fast response time and long duration of fluorescence intensity. These excellent performances made the proposed method to be applied for the determination of SA in Semen Sinapis and Descurainiae Semen.

Molecularly Imprinted Polymer Micro- and Nano-Particles. A review

In recent years, molecularly imprinted polymers (MIPs) have become an excellent solution to the selective and sensitive determination of target molecules in complex matrices where other similar and relative structural compounds could coexist. Although MIPs show the inherent properties of the polymers, including stability, robustness, and easy/cheap synthesis, some of their characteristics can be enhanced, or new functionalities can be obtained when nanoparticles are incorporated in their polymeric structure. The great variety of nanoparticles available significantly increase the possibility of finding the adequate design of nanostructured MIP for each analytical problem. Moreover, different structures (i.e., monolithic solids or MIPs micro/nanoparticles) can be produced depending on the used synthesis approach. This review aims to summarize and describe the most recent and innovative strategies since 2015, based on the combination of MIPs with nanoparticles. The role of the nanoparticles in the polymerization, as well as in the imprinting and adsorption efficiency, is also discussed through the review.

Selective detection of phospholipids using molecularly imprinted fluorescent sensory core-shell particles

Sphingosine-1-phosphate (S1P) is a bioactive sphingo-lipid with a broad range of activities coupled to its role in G-protein coupled receptor signalling. Monitoring of both intra and extra cellular levels of this lipid is challenging due to its low abundance and lack of robust affinity assays or sensors. We here report on fluorescent sensory core-shell molecularly imprinted polymer (MIP) particles responsive to near physiologically relevant levels of S1P and the S1P receptor modulator fingolimod phosphate (FP) in spiked human serum samples. Imprinting was achieved using the tetrabutylammonium (TBA) salt of FP or phosphatidic acid (DPPA·Na) as templates in combination with a polymerizable nitrobenzoxadiazole (NBD)-urea monomer with the dual role of capturing the phospho-anion and signalling its presence. The monomers were grafted from ca 300 nm RAFT-modified silica core particles using ethyleneglycol dimethacrylate (EGDMA) as crosslinker resulting in 10–20 nm thick shells displaying selective fluorescence response to the targeted lipids S1P and DPPA in aqueous buffered media. Potential use of the sensory particles for monitoring S1P in serum was demonstrated on spiked serum samples, proving a linear range of 18–60 µM and a detection limit of 5.6 µM, a value in the same range as the plasma concentration of the biomarker.

Rational construction of a triple emission molecular imprinting sensor for accurate naked-eye detection of folic acid

Multiple emissions of blue, green and red from a molecular imprinting sensor rationally constructed, were used for the fluorescence colorimetric visualization of a fluorescent analyte of folic acid, using a flexible post-imprinting mixing strategy. That is, two kinds of folic acid-templated molecularly imprinted polymers (MIPs) were firstly synthesized by encapsulating green and red fluorescent quantum dots (g-QDs and r-QDs) individually on SiO2 cores, and they were then mixed at an appropriate ratio, resulting in a triple emission MIPs sensor. Upon folic acid recognition, the inherent blue fluorescence of folic acid was intensified, and the green and red fluorescence of the sensor QDs were gradually quenched. The quenching rate difference between g-QDs and r-QDs was greatly enhanced and used to obtain a wider-range and profuse fluorescence color evolution, by investigating the influences of the QDs modifier, eluent and imprinting layer thickness in detail. Under optimal conditions, the ratiometric intensity change of the three color emissions varied in a logistic function within 0.01-50 ppm of folic acid, and the corresponding fluorescence colors shifted from yellow to orange to red to purple and finally to blue. This excellent visualization capability of the MIPs sensor contributed to the accurate naked-eye detection of folic acid concentration using a portable ultraviolet lamp. Moreover, the MIPs sensor succeeded in determining folic acid in complicated food and serum samples, providing comparable results with the PRC standard method and satisfactory recoveries of 99.5-108.0%. The merits, including construction simplicity, high sensitivity and selectivity, and result visualization, enable such a multiple emission MIPs sensing strategy to be potentially applicable for visual identification and determination of various analytes in more fields.

Dual roles of 3-aminopropyltriethoxysilane in preparing molecularly imprinted silica particles for specific recognition of target molecules

3-Aminopropyltriethoxysilane (APTES) is a silane widely used to supply amino groups for further modifications on various materials, but it is less studied as a catalyst to catalyze sol–gel silica polymerization. Here, by using APTES as the catalyst instead of the conventional basic catalysts, a novel strategy was developed to prepare silica-based molecularly imprinted polymers (MIPs). Meanwhile, APTES was employed as the functional monomer to create imprinted nanocavities for specific recognition of target molecules. The as-synthesized MIP exhibited ultra-high recognition capability due to the elimination of the detrimental effect on the imprinting performance caused by the additional catalysts. The preparation process, specificity, pH effect, binding capacity and affinity of the MIP were studied in detail. The MIP microparticles could be packed into a solid phase extraction column for removing the target molecule in water efficiently, and the molecule could easily be enriched by 40 times. The interaction of the functional monomer and template was studied by the calculation method, giving a more clear understanding of the recognition behaviours of the imprinted polymers. The strategy could be extended not only to prepare highly specific MIPs for other small phosphoric molecules, but also for biomolecules e.g. phosphorylated peptides or proteins.

A novel strategy was developed for preparing highly selective molecularly imprinted polymers using 3-aminopropyltriethoxysilane as both a functional monomer and catalyst.

Naphthalimide-based optical turn-on sensor for monosaccharide recognition using boronic acid receptor

A highly selective and sensitive fluorescent sensor for the determination of fructose is developed. The fluorescent sensor was prepared by incorporating a new naphthalimide dye with a planar structure as a selectophore and graphene oxide (GO) nanoplatelets as a quencher for rapid optical detection of fructose. The designed probe, made with the high fusion loop-containing dye, along with the GO nanoplatelets, detected fructose over the other monosaccharides very well. The proposed sensor displays a linear response range of 7 × 10-5 to 3 × 10-2 M with a low limit of detection of 23 × 10-6 M in solution at pH 7.4. This sensor shows a good selectivity towards fructose with respect to other saccharides. The proposed sensor was then applied to the determination of fructose in human plasma with satisfactory results.

Ternary Emission of a Blue-, Green-, and Red-Based Molecular Imprinting Fluorescence Sensor for the Multiplexed and Visual Detection of Bovine Hemoglobin

A novel ternary-emission fluorescence sensor was proposed by post-imprinting mixing blue-/green-/red-emission bovine hemoglobin (BHb) imprinted polymers (b-MIPs, g-MIPs, and r-MIPs) at a proper ratio and realized the multiplexed and visual detection of BHb. The three MIPs were individually embedded with blue-emission 7-hydroxycoumarin, green-emission CdTe quantum dots (QDs), and red-emission CdTe/ZnS QDs. Upon interaction with BHb within 8 min, the fluorescence of CdTe and CdTe/ZnS QDs were simultaneously turned off, whereas the 7-hydroxycoumarin turned on the fluorescence intensity. Thereupon, the ratiometric fluorescence intensity of the ternary emission linearly varied within 0.025-3 μM BHb, accompanying the profuse fluorescence color evolution from yellowish green to yellow to salmon to plum to purple to finally blue. In comparison with the dual- or single-emission sensor, the ternary-emission fluorescence MIPs sensor provided a wider color variation covering the green-red-blue window for accurate naked-eye determination of BHb, as well as a lower detection limit down to 7.8 nM and a higher imprinting factor of 15.2. Moreover, the satisfactory recoveries of 99.25-111.7% in determining the spiked BHb in bovine urine samples, as well as the optical stability and post-imprinting construction convenience, indicated that the developed tricolor-emission fluorescence MIPs sensor provided an ideal alternative for rapid, sensitive, and visual determination of proteins in complicated samples.

Selective electrochemical detection of bisphenol A using a molecularly imprinted polymer nanocomposite

A molecularly imprinted nanocomposite with covalently connected polyacrylate, β-cyclodextrin and graphene is synthesized for selective capture and electrochemical detection of bisphenol A.

Beyond natural antibodies – a new generation of synthetic antibodies created by post-imprinting modification of molecularly imprinted polymers

Post-imprinting modification (PIM) is an innovative strategy for generating MIPs analogous to biosynthesising proteins to introduce new functionalities in a site-directed manner.

Dynamic assembly of molecularly imprinted polymer nanoparticles

Manipulation of specific binding and recycling of materials are two important aspects for practical applications of molecularly imprinted polymers. In this work, we developed a new approach to control the dynamic assembly of molecularly imprinted nanoparticles by surface functionalization. Molecularly imprinted polymer nanoparticles with a well-controlled core-shell structure were synthesized using precipitation polymerization. The specific binding sites were created in the core during the first step imprinting reaction. In the second polymerization step, epoxide groups were introduced into the particle shell to act asan intermediate linker to immobilize phenylboronic acids, as well as to introduce cis-diol structures on surface. The imprinted polymer nanoparticles modified with boronic acid and cis-diol structures maintained high molecular binding specificity, and the nanoparticles could be induced to form dynamic particle aggregation that responded to pH variation and chemical stimuli. The possibility of modulating molecular binding and nanoparticle assembly in a mutually independent fashion can be exploited in a number of applications where repeated use of precious nanoparticles is needed.