Imprinting Film Research Articles

A fluorescent biosensor based on surface cell imprinting film for Salmonella typhimurium detection

Salmonella typhimurium (S. typhimurium) is a major foodborne pathogen that poses a potentialrisk to public health. The development of biosensors that are specific, sensitive, and easy to manipulate can greatly reduce the potential risk posed by S. typhimurium. A robust, highly sensitive and specific fluorescent biosensor was proposed by combining N-succinyl-chitosan-doped surface bacterial cell imprinted film (SCIF) with typical aggregation induced emission (AIE) fluorescent substance Au(I)-disulfide nanoparticles. The proposed fluorescent sensor can achieve linear detection of S. typhimurium in the concentration range from 10 to 106 CFU/mL with a detection limit of 4 CFU/mL. In addition, the modification of the SCIF on the surface enables specific abiotic recognition of the target bacteria. This fluorescence sensing strategy can be used for the detection of S. typhimurium in chicken meat samples. The platform can be replicated for the detection of other bacteria or cells via making different SCIFs, which is promising for the detection of practical samples for clinical and biological applications.

Molecular imprinting film and turn-on fluorescence probe working in tandem for Salmonella Typhimurium detection

Salmonella is one of the most common pathogens that cause foodborne illnesses. Rapid qualitative and quantitative detection of Salmonella Typhimurium (S. Typhimurium) is important for human health. In this study, a Förster resonance energy transfer (FRET)-based platform was proposed to activate fluorescence sensing with a bacteria-imprinted film to facilitate S. Typhimurium detection. Imprinted films with surface cavity sites that match the surface cavity sites of S. Typhimurium was prepared. The modification of the films using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS), weakened the hydrophobicity of the films, inhibiting the nonspecific adsorption of nontarget bacteria. Copper nanoclusters and gold nanoparticles, which are good fluorescent molecular donors and acceptors, respectively, can be used to prepare fluorescence quenching-recovery probes based on FRET. The competitive binding of the bacteria to the probes enabled the restoration of fluorescence, facilitating bacteria quantification based on the fluorescence intensity. The optimized fluorescent sensor showed a linear response to S. Typhimurium concentrations in the range of 10–107 CFU/mL with a detection limit of 17.38 CFU/mL. Thus, the proposed label-free fluorescent sensor is sensitive to S. Typhimurium, showing potential applications in the detection of this pathogen as well as other foodborne pathogens in food samples.

Disulfide-Bridged Dendritic Organosilicas-Based Biodegradable Molecularly Imprinted Polymers for Multiple Targeting and pH/Redox-Responsive Drug Release toward Chemical/Photodynamic Synergistic Tumor Therapy.

In this study, a sialic acid (SA) and transferrin (TF) imprinted biodegradable disulfide bridging organosilicas-based drug delivery system (SS-DMONS/DOX-Ce6@MIPs) for targeted cancer therapy is constructed, for the first time. Disulfide bridged dendritic mesoporous organosilicas nanoparticles (SS-DMONs) not only enhance drug loading as the drug repository, but also provide enough specific surface area for the molecular imprinting shell to expose more degradation and imprinted sites on the surface. In addition, SS can be disturbed in a highly reducing tumor microenvironment to achieve degradation. The biodegradable imprinting film, prepared with customized 2-amino-N-(3,4-dihydroxyphenethyl)-3-mercaptopropanamide and 4-mercaptophenylboronic acid as functional monomers, endows SS-DMONs with active targeting capacity, and responsive drug release through degradation under acidic and highly reductive tumor microenvironment. SS-DMONS/DOX-Ce6@MIPs after binding of TF can target tumor cells actively through multiple interactions, including the affinity between antigen and antibody, and the specific recognition between molecularly imprinted polymers and template molecules. Under laser irradiation the loaded chlorin e6 (Ce6) that can produce toxic reactive oxygen, combined with the doxorubicin (DOX), achieves chemical/photodynamic synergistic anticancer effects. SS-DMONS/DOX-Ce6@MIPs present excellent tumor targeting and dual-responsive drug release, which provides an effective strategy for chemical/photodynamic antitumor therapy.

Anion Exchange Affinity-Based Controllable Surface Imprinting Synthesis of Ultrathin Imprinted Films for Protein Recognition.

Anion exchange affinity-based controllable surface imprinting is an effective approach to overcome low imprinting efficiency and high non-specific binding capacity. The template proteins were first immobilized on the anchored tetraalkylammonium groups of the nanoparticles via anion exchange affinity-based interactions, enabling monolayer sorption using a low template concentration. The combined use of surface-initiated photoiniferter-mediated polymerization to precisely control the imprinted film thickness, allowing the formation of homogeneous binding cavities, and the construction of effective binding sites resulted in a low non-specific binding capacity and high imprinting efficiency. The obtained imprinted films benefited from the anion exchange mechanism, exhibiting a higher imprinting factor and faster binding rate than the reference material. Binding tests revealed that the binding strength and selective recognition properties could be tuned to a certain extent by adjusting the NaCl concentration. Additionally, in contrast to the harsh template elution conditions of the covalent immobilization approach, over 80% of the template molecules were readily removed from the imprinted films using supersonic elution with an aqueous mixture of NaCl and HAc. Introducing template immobilization by anion exchange interactions to the synthesis of imprinted materials may provide a new approach for effective biomacromolecular imprinting.

Fabrication of imprinted photonic films via predesigned multiple UV‐polymerizations and their ability to detect solvents and metal ions in aqueous solution

AbstractTo synthesize photonic films without a chiral dopant, a predesigned multiple photopolymerization process was carried out. The photonic films were prepared by the photopolymerization of a mixture of chiral nematic liquid crystals. After polymerization, the chiral dopant, CB15, was removed and recycled. The imprinted photonic polymer films showed Bragg reflection without the presence of the chiral dopant. Upon the sensing of solvents in aqueous solution, significant color changes and peak shifts were observed by the naked eye and ultraviolet–visible spectroscopy, respectively. A linear calibration curve between the central wavelength of the reflection band of the fabricated imprinting film and the volume ratio of 1,4‐dioxane in water was observed. Furthermore, the sensing of chloroform content in methanol, ethanol, and acetone via the imprinted film were also investigated. The results suggest that the synthesized imprinted photonic films can detect different kinds of mixed solvents. The sensing properties of the photonic films were further improved by copolymerization with a rhodamine‐derived monomer. The synthesized modified photonic films can detect heavy metal ions in aqueous solution. This study reports a novel, recyclable, and easy approach to detect organic solvents and copper ions in aqueous solution.

L-phenylalanine-imprinted polydopamine-coated CdS/CdSe n-n type II heterojunction as an ultrasensitive photoelectrochemical biosensor for the PKU monitoring

A simple and highly sensitive photoelectrochemical biosensor towards L-phenylalanine, as a kind of typical essential amino acid and phenylketonuria biomarker was developed on a surface molecular imprinted (MIP) polydopamine-coated CdS/CdSe/Zn heterojunction. Hierarchical marigold flower-like Zn layer decorated by n-type dichalcogenides interfacial heterojunction was successfully designed and synthesized on Ti foil for PEC converter by in situ electrodeposition. A visible-light-driven molecular imprinting film was prepared through the electropolymerization of dopamine in the presence of L-Phe as biomarker. The combination of bio-MIP and photoelectrochemistry overcomes the defects of the PEC method, which is the absence of selectivity, and offers a new PEC sensor with high sensitivity and selectivity based on visible-light-driven heterojunction and biopolymer-enhanced strategy. The unique interfacial between the Zn marigold flower layer as low work function support and CdS/CdSe n-n heterojunction as well as n-type characteristics of polydopamine imprinted by L-Phe biomarker drastically increase the light trapping and absorption in the visible range, and dramatically inhibit the charge carrier recombination, which is crucial for boosting the Bio-PEC activity. Photocatalytic, electrocatalytic and physicochemical properties of the above-mentioned layers were fully characterized. As-prepared PEC biosensor displayed superb performance for the detection of L-Phe biomarker in the optimized condition obtained from central composite design modeling, showing two linear range 0.005–2.5 and 2.5–130 μM and a low detection limit of 0.9 nM. This work suggests that such L-Phe-imprinted polydopamine-coated Zn/CdS/CdSe heterojunction is greatly promising for being applied in photoelectrochemical biosensing with high photo-electron conversion efficiency.

A molecularly imprinted photoelectrochemical sensor based on the use of Bi2S3 for sensitive determination of dioctyl phthalate.

A molecularly imprinted polymer photoelectrochemical (MIP-PEC) sensor based on bismuth sulfide (Bi2S3) is described for the determination of the plasticizer dioctyl phthalate (DOP). Bi2S3 was used as the photoelectrical converter of the sensor, and visible light was utilized as the excitation source. The molecular imprinting film was prepared through the electropolymerization of monomers in the presence of DOP. Under optimal experimental conditions, the photoelectrochemical response was linearly proportional to the logarithm of the DOP concentration in the 0.5-70 pM DOP concentration range, and the detection limit was 0.1 pM. The method is highly stable and reproducible. It was applied to the determination of DOP in spiked water samples. Graphical abstract A novel molecularly imprinted photoelectrochemical sensor with high sensitivity and high selectivity based on Bi2S3 was developed for dioctyl phthalate detection. Bi2S3 was firstly used as a photoelectric converter in photoelectrochemical sensor to improve the sensitivity of the sensor. Combining photocurrent measurement with molecular imprinting technique makes the sensor highly selective.

Molecularly imprinted polymer-based reusable biosensing device on stainless steel for spatially localized detection of cytokine IL-1β

A molecularly imprinted polymer (MIP) based biosensing device on stainless steel (SS) for detection of locally variable concentration of cytokine interleukin-1β (IL-1β) was successfully developed using a sandwich assay scheme. The SS surface was firstly modified with a layer of polydopamine (PDA) followed by the attachment of a layer of poly(ethyleneimine) (PEI) by electrostatic adsorption. Subsequently, the template protein IL-1β was adsorbed on the PEI terminated SS surface due to electrostatic adsorption. A PDA imprinting film was then in-situ synthesized on the surface of the modified SS substrate with incorporated template cytokine. Finally, the template was washed off the SS substrate leaving behind cavities with specific shape and capable of capturing cytokines thus forming a MIP biosensing interface. After exposure to the analyte IL-1β, the MIP biosensing device was incubated with IL-1β detection antibody-modified fluorescent polystyrene beads allowing to determine the amount of captured IL-1β based on fluorescence intensity. The device has been demonstrated to detect IL-1β with low detection limit of 10.2 pg mL−1, and a linear detection range of 25–400 pg mL−1. This MIP biosensing device can be regenerated more than three times with coefficient of variation 2.08%. The device was applied for the detection of IL-1β secreted by rat macrophages, where the good specificity and selectivity were achieved. MIP serves in this device as a superior substitute of antibody with exceptional stability and reusability. The MIP based biosensing technology presented in our work paves a new way for developing a universal and robust sensing platform for the detection of spatially localised small proteins with low physical concentration.

A Surface Plasmon Resonance-Based Optical Fiber Probe Fabricated with Electropolymerized Molecular Imprinting Film for Melamine Detection.

Molecularly imprinted polymer (MIP) films prepared by bulk polymerization suffer from numerous deficiencies, including poor mass transfer ability and difficulty in controlling reaction rate and film thickness, which usually result in poor repeatability. However, polymer film synthesized by electropolymerization methods benefit from high reproducibility, simplicity and rapidity of preparation. In the present study, an Au film served as the refractive index-sensitive metal film to couple with the light leaked out from optical fiber core and the electrode for electropolymerizing MIP film simultaneously. The manufactured probe exhibited satisfactory sensitivity and specificity. Furthermore, the surface morphology and functional groups of the synthesized MIP film were characterized by Atomic Force Microscopy (AFM) and Fourier transform infrared microspectroscopy (FTIR) for further insights into the adsorption and desorption processes. Given the low cost, label-free test, simple preparation process and fast response, this method has a potential application to monitor substances in complicated real samples for out-of-lab test in the future.

Molecularly imprinted electrochemical sensor, formed on Ag screen-printed electrodes, for the enantioselective recognition of d and l phenylalanine

In this study, electrochemical sensors for the enantioselective recognition of d and l phenylalanine were prepared using a molecular imprinting technique in which the electro-polymerization of pyrrole was carried out by Chronopotentiometry(CP) with the target molecules being present on a Ag screen printed electrode's (SPE) surface. The sensing performance was evaluated by multi-potential steps at 0 and 2V(vs. Ag/AgCl) held for 1s and 2s, respectively, for 20 cycles (with the two enantiomers being present at the same concentration). The individual selectivity's for l and d- phenylalanine on their respective imprinted films were estimated to be L/D = 23.480 ± 2.844/1 and D/L = 19.134 ± 1.870/1 respectively, based on the current change between 0 and 2V (vs. Ag/AgCl) with the two enantiomers being present at the same concentration (10mM). Several parameters affecting recognition ability were investigated including: cross-selectivity of d and l- phenylalanine imprinted film, phenylalanine concentration effects, interfering species, deactivation and the storage life of electrode. The phenylalanine imprinted films were also characterized by AC impedance, chronoamperometry, Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscope(SEM), and Energy Dispersive X-Ray Spectroscopy (EDS). Finally, a recognition mechanism for the interaction of the polypyrrole film with its template under the influence of applied negative and positive potentials is proposed.

Ultrasensitive Electrochemical Detection of Glycoprotein Based on Boronate Affinity Sandwich Assay and Signal Amplification with Functionalized SiO2@Au Nanocomposites.

Herein we propose a multiple signal amplification strategy designed for ultrasensitive electrochemical detection of glycoproteins. This approach introduces a new type of boronate-affinity sandwich assay (BASA), which was fabricated by using gold nanoparticles combined with reduced graphene oxide (AuNPs-GO) to modify sensing surface for accelerating electron transfer, the composite of molecularly imprinted polymer (MIP) including 4-vinylphenylboronic acid (VPBA) for specific capturing glycoproteins, and SiO2 nanoparticles carried gold nanoparticles (SiO2@Au) labeled with 6-ferrocenylhexanethiol (FcHT) and 4-mercaptophenylboronic acid (MPBA) (SiO2@Au/FcHT/MPBA) as tracing tag for binding glycoprotein and generating electrochemical signal. As a sandwich-type sensing, the SiO2@Au/FcHT/MPBA was captured by glycoprotein on the surface of imprinting film for further electrochemical detection in 0.1 M PBS (pH 7.4). Using horseradish peroxidase (HRP) as a model glycoprotein, the proposed approach exhibited a wide linear range from 1 pg/mL to 100 ng/mL, with a low detection limit of 0.57 pg/mL. To the best of our knowledge, this is first report of a multiple signal amplification approach based on boronate-affinity molecularly imprinted polymer and SiO2@Au/FcHT/MPBA, exhibiting greatly enhanced sensitivity for glycoprotein detection. Furthermore, the newly constructed BASA based glycoprotein sensor demonstrated HRP detection in real sample, such as human serum, suggesting its promising prospects in clinical diagnostics.

A calcium ion-imprinted porous film prepared from a cellulose-alginate composite

An ion-imprinted (IIP) film has been successfully prepared in this work. Firstly, mixture solution of cellulose and alginate was obtained by dissolving those polymers in a NaOH/urea aqueous solution. Then the mixture solution was cast onto glass plate and coagulated in CaCl2 aqueous solution bath to prepare a composite film. The matrix of the film was further fixed by cross-linking. Finally, the chelated Ca2+ in the matrix was removed to obtain the IIP film. The IIP film was characterized to show satisfactory mechanical properties, and to exhibit porous mesh network microstructure. The equilibrium swelling ratio of the IIP film was determined to be 700 %. The IIP film was immersed into Ca2+, Ca2+/Cu2+, Ca2+/Zn2+ and Ca2+/Mg2+ solutions to check the adsorption behavior, respectively. The results indicate that the IIP film displayed highly selective Ca2+ recognition, and the presence of additional cations had little effect on the Ca2+ recognition. Thus prepared Ca2+ imprinted film have potential applications in fields such as hard water softening, and Ca2+ enrichment or recognition.

Grazing-incidence wide-angle X-ray diffraction study on molecular aggregation state of imprinted polyimide film before and after hard baking

Nanoimprint lithography (NIL) was carried out on precursor of polyimide (PI), poly(amic acid) film, and then hard baking to obtain imprinted PI film. The molecular aggregation states of imprinted PI films before and after hard baking were investigated by grazing-incidence wide-angle X-ray diffraction comparing with the one of flat PI film. It was found that NIL and hard baking can strongly affect the molecular aggregation states of PI film. Before hard baking, PI chain is aligned parallel to the line direction on the line. After hard baking, the alignment in ordered domain was changed to that the PI molecule of which chain axis is perpendicular to the line direction is significantly increased, while, PI molecule of which chain axis is parallel to the line direction is decreased after hard baking. Through comparing with the flat PI, crystallinity of imprinted PI film has been significantly enhanced.

Layer-by-layer assembly sensitive electrochemical sensor for selectively probing l-histidine based on molecular imprinting sol–gel at functionalized indium tin oxide electrode

A novel sensitive and selective imprinted electrochemical sensor was successfully constructed for the direct detection of l -histidine by combination of a molecular imprinting film and multi-walled carbon nanotubes (MWNTs). The sensor was fabricated onto an indium tin oxide (ITO) electrode via stepwise modification of MWNTs and a thin film of molecularly imprinted polymers (MIPs) via sol–gel technology. The introduced MWNTs exhibited noticeable enhancement on the sensitivity of the MIPs sensor. Meanwhile, the molecularly imprinted film displayed high sensitivity and excellent selectivity for the target molecule l -histidine. The proposed imprinted sensor was characterized by using scanning electron microscope (SEM) and electrochemical methods involving cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometric i–t curve. A linear ranging from 2.0 μmol L −1 to 1.0 mmol L −1 for the detection of l -histidine was observed with the detection limit of 5.8 × 10 −9 mol L −1 for S/N = 3. This imprinted electrochemical sensor was successfully employed to detect l -histidine in human blood serum.

Molecularly imprinted electrochemical sensor able to enantroselectivly recognize d and l-tyrosine

Electrochemical sensors were fabricated on nickel electrodes by molecularly imprinting d and l-tyrosine on polypyrrole films to form complementary cavities for subsequent template recognition. The performance of the imprinted films was evaluated by coulometry using an applied positive potential to induce adsorption of the target molecules. Using this procedure high enantioselectivities was found for each imprinted film. The individual selectivities for l and d-tyrosine on their respective imprinted films were estimated to be l/ d = 9.4/1 and d/ l = 27.2/1, determined by applying potential at a sweep rate of 0.1 V/s from −0.1 to 0.5 V (versus Ag/AgCl) with the two enantiomers being present at the same concentration (5 mM). Several factors affecting rebinding, such as extraction time, film thickness, template concentration and sweep rate were investigated to achieve optimum recognition ability. The diffusion of target molecules in the polypyrrole films was also examined. A recognition mechanism for the interaction of the polypyrrole film for its template under the influence of an applied positive potential is proposed in this study.