Non-imprinted Polymer Research Articles

Enhancing anti-interference ability of molecularly imprinted ratiometric fluorescence sensor via differential strategy demonstrated by the detection of bovine hemoglobin

The non-specific adsorption of interferents onto the outside surface of molecularly imprinted polymers (MIPs) particles is disadvantageous for selective determination of the template molecules. Based on the fact that the responses of non-imprinted polymers (NIPs) and MIPs particles to non-template molecules are similar, the anti-interference ability of MIPs sensor can be much improved via differential strategy, demonstrated by bovine hemoglobin (BHb) determination. The MIPs for BHb were prepared via surface imprinting and sol-gel process, with graphene quantum dots@SiO2/CdTe quantum dots (GQDs@SiO2/CdTe QDs) for ratiometric fluorescence measurements. By using a weight factor of 1.283 to compensate the lower specific surface area in NIPs particles, the differential ratiometric fluorescence signals between MIPs and NIPs channels to 2.00 μM ovalbumin and phycocyanin are equivalent to BHb at the concentration of 0.025 and 0.014 μM, which are only about 11 % and 5.8 % of the interference level in the normal ratiometric fluorescence method, respectively. The differential ratiometric fluorescence measurement was also performed in a smartphone-based device for field analysis of BHb in urine samples, with the linear range of 0.05–4 μM and the detection limit of 13 nM.

Molecularly imprinted polymers prepared from a single cross-linking functional monomer for solid-phase microextraction of estrogens from milk.

In this work, a single cross-linking functional monomer, 2,5-divinylterephthalaldehyde, was designed and synthesized to simplify the preparation of molecularly imprinted polymers (MIPs). In the presence of estradiol as a template, MIPs were successfully prepared using 2,5-divinylterephthalaldehyde along with a solvent and initiator. This method reduced most of the complex variables encountered in the traditional synthesis. Characterization of the morphology and structure of the MIPs was performed by scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. Compared with non-imprinted polymers, the MIPs had higher adsorption capacities for five estrogens with imprinting factors above 2.9. The MIPs had high extraction efficiencies, good functional properties, long lifetimes, and good reproducibility, which made them suitable for solid-phase microextraction (SPME). Coupled with ultra-high performance liquid chromatography tandem mass spectrometry, the MIP-based fibers were applied to SPME for the analysis of five estrogens in milk samples. Under the best conditions, the established method had a wide linear range (0.5-10000 ng kg-1), low limits of detection (0.08-0.26 ng kg-1) and quantification (0.26-0.87 ng kg-1), good precision (3.2-8.1%, n=6), and fiber-to-fiber reproducibility (4.3%-8.8%, n=3). The MIPs-based fibers can be reused at least 60 times without apparent loss of extraction efficiency. Finally, this method was applied to the determination of target estrogens in milk samples with satisfactory relative recoveries (84.3%-105%, relative standard deviation ≤ 7.8%).

An eco-friendly sensor based on CQD@MIPs for detection of N-acylated homoserine lactones and its 3D printing applications

N-acylated homoserine lactones (AHLs), a class of auto-inducers produced by Gram-negative bacteria, are typical signaling molecules in quorum sensing (QS) systems. Importantly, AHLs play a key role in determining the virulence of foodborne pathogens and reflect the activity of spoilage bacteria. In this study, an eco-friendly fluorescence-sensing platform for the rapid and sensitive detection of AHLs was developed and characterized. Molecularly imprinted polymers embedded with yellow-emitting carbon quantum dots (CQDs) were obtained via the sol-gel process using furanone as an alternative template molecule, and long-wave-emitting CQDs with excellent optical properties were used as signal conversion materials. After template elution, the blotting cavities on the surface of the CQD@MIPs (molecularly imprinted polymers) were able to selectively recognize AHLs, demonstrating a stronger fluorescence response compared with the corresponding CQD@NIPs (non-imprinted polymers). Under optimal test conditions, a good linear relationship between the concentration of analyte and the relative fluorescence intensity of the CQD@MIPs was observed. The linear detection range was 0–2.0 μM, and the limit of detection (LOD) was 0.067 μM. Importantly, the proposed sensing platform functioned as an optical detection strategy that responded quickly (2 min) to AHLs. Additionally, this sensing platform was applied to the analysis of AHLs in bacterial supernatant samples with satisfactory results. More interestingly, the 3D-printing CQD@MIPs were tentative explored in this work, which was personalized and portable, has an advantage of point of care testing (POCT) detection in the future. Based on these results, this detection strategy has demonstrated substantial potential for application in and the field of food safety.

Study on synthesis and adsorption properties of ReO4− ion imprinted polymer

Water solution polymerization was adopted to prepare perrhenate ion imprinted polymers in this work, and preparation conditions, such as molar ratio of acrylic acid, N,N - methylene double acrylamide, hydrogen peroxide and ascorbic acid to N-vinyl pyrrolidone, polymerization time and temperature on adsorption separation property were investigated and optimized using adsorption quantities and separation degree as indexes. To enhance the adsorption selectivity, adsorption properties of samples prepared under different conditions were conducted in a mixture aqueous solution of ammonium perrhenate and potassium permanganate with the molar ratio of 1:1. Results showed that as the molar ratio of N,N - methylene double acrylamide, acrylic acid, hydrogen peroxide, ascorbic acid to N-vinyl pyrrolidone were 2.0, 1.9, 0.03, and 0.003 respectively, the reaction temperature and time were 35 °C and 24 h, adsorption quantities and separation degree arrived at 0.037 mmol/g and 2.31, respectively, while the adsorption capacities and separation degree of non-imprinted polymers were only 0.009 mmol/g and 0.22. Besides, study was also discovered that the prepared samples presented an exciting reusable stability. Based on samples prepared under optimal conditions, the structure was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, BET surface area and thermogravimetric analysis using non-imprinted polymer prepared under the same conditions as a control. Finally, the adsorption thermodynamics and kinetics were studied, and the kinetics documented that the adsorption of perrhenate ion imprinted polymers was a zero-order model process. The thermodynamics presented the adsorption was more suitable to be expressed by Langmuir model, and Scatchard analysis revealed that heterogeneous binding sites were formed in IIP.

Chitosan-based molecular imprinted polymer for extraction and spectrophotometric determination of ketorolac in human plasma

A selective chitosan-based ion exchange molecular imprinted polymer (MIP) was prepared for ketorolac (KET) using the sol-gel method and glutaraldehyde as a crosslinker. The nonimprinted polymer (NIP) was prepared and used as a control, during the whole experiment. The chemical and morphological characteristics of the prepared polymers were investigated using FTIR and SEM, respectively. The prepared MIP was applied to determine the optimum operational conditions for KET extraction from dilute aqueous solutions. The adsorption step was performed at pH5 and a contact time of 20min, using 0.1N HCl as an elution solvent for 30min. The specificity of the prepared polymer was indicated by an imprinting factor of 1.45. The prepared MIP was successfully applied for selective solid phase extraction and subsequent determination of KET in spiked human plasma samples over a range of 2-20μg/mL, with a mean % recovery of 94.62% using derivative spectroscopy.

Development of a reliable bioanalytical method based on prostate specific antigen trapping on the cavity of molecular imprinted polymer towards sensing of PSA using binding affinity of PSA-MIP receptor: A novel biosensor

In this study, electrically-conducting poly [Toluidine Blue (PTB)] was applied as artificial receptor. It was organized by molecular imprinting approaches and via electrochemical technique for the sensitive monitoring of prostate-specific antigen (PSA). The protein-imprinted PTB was electropolymerized in a pre-formed glutaraldehyde-cysteamine (GA-Cys A) matrix on the surface of gold electrode, which significantly boosted the stability against degradation of the Molecular Imprinted Polymer (MIP) on the surface of pre-modified gold electrode. Moreover, the MIP bio-receptor ability towards protein recognition was explored by some electrochemical techniques. The binding affinity of MIP system was considerably upper than that of non-imprinted polymer (NIP) system, indicating the success of the method in generating imprinted materials that was specifically use to PSA protein. The incubation of the MIP modified electrode in various concentration of PSA (from 1–60 μg/L) resulted in the increase of the Fe (CN)63−/4− redox peak current. The bio-device also showed linear response from 1–60 μg/L and LLOQ of 1 μg/L by using DPV technique, leading to PSA monitoring in clinical samples. The proposed MIP-based biosensor was satisfactorily applied to the determination of PSA in human plasma samples. Therefore, the developed bio-device provides a new approach for sensitive, simple, rapid, and cost-effective monitoring of 1 μg/L of PSA. Notably, this approach could appear as an appropriate candidate for point-of-care (POC) use in clinical and biomedical analyses.

Molecularly imprinted polymers-A closer look at the control polymer used in determining the imprinting effect: A mini review.

Molecular recognition displayed by naturally occurring receptors has continued to inspire new innovations aimed at developing systems that can mimic this natural phenomenon. Since 1930s, a technology called molecular imprinting for producing biomimetic receptors has been in place. In this technology, tailor made binding sites that selectively bind a given target analyte (also called template) are incorporated in a polymer matrix by polymerizing functional monomers and cross-linking monomers around a target analyte followed by removal of the analyte to leave behind cavities specific to the analyte. The success of the imprinting process is defined by two main figures of merit, that is, the imprinting factor, and selectivity, which are determined by comparing the amount of target analyte or structural analogue bound by the molecularly imprinted polymer (MIP) and the nonimprinted polymer (NIP). NIP is a control synthesized alongside the MIP but in the absence of the template. However, questions arise on whether these figures of merit are reliable measures of the imprinting effect because of the significant differences between the MIP and the NIP in terms of their physical and chemical characteristics. Therefore, this review critically looks into this subject, with a view of defining the best approaches for determining the imprinting effect.

Optimization of Different Parameter in Synthesis Ion Imprinted Polymers via Precipitation Polymerization for Nitrate Adsorption

An important issue in synthesis of ion imprinted polymers (IIP) is optimization of the main parameters that involved during polymerization process as those parameters can influence the performance of IIP. In this study, IIP was synthesized by precipitation polymerization using allylthiourea (ATU) as monomer, nitrate as template ion, ethylene glycol dimethacrylate (EGDMA) as crosslinker, 2,2’-azobisisobutyronitrile (AIBN) as initiator with 365 nm ultraviolet (UV) light and mixture of acetonitrile and dimethylsulfoxide (DMSO) as porogenic solvent. The influences of various polymerization parameters in the synthesis of IIPs were investigated. The parameters studied included: ratio of monomer-template, amount of crosslinker and amount of porogenic solvent. These parameters were optimized using response surface methodology (RSM) coupled with central composite design CCD). Results showed that IIP with an optimum adsorption capacity of 156.233 mg/g of nitrate ion NO3 −) can be obtained under the following polymerization conditions: 3.90 mmol of ATU, 18.67 mmol of EGDMA and 38.30 mL of porogenic solvent. The nitrate imprinted polymer and non-imprinted polymer were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The SEM micrograph showed microparticles ranging from 14.05 - 16.17 µm in diameter and the surface was rough and porous. The sorption of IIP followed Langmuir adsorption isotherm model. In this study, the binding capacity indicated that nitrate imprinted polymer recognized NO3 − in aqueous solution more effectively compared to non-imprinted polymer and this polymer particles potrayed better adsorption as compared other adsorbent

Development of Melamine Electrochemical Sensor Using Molecularly Imprinted Conducting Polyanilne-Oxalic Acid Blend as a Molecular Recognition Element

In the present work, oxalic acid doped molecularly imprinted conducting polyaniline film for melamine detection was prepared by in-situ-electrochemical polymerization on the glassy carbon electrode (GCE) using melamine as template. The optimal monomer/template molar ratio was attained to be 0.2:0.1:0.01 (aniline: oxalic acid: melamine) and molecular recognition properties towards melamine were evaluated by differential pulse voltammetry. Under optimal conditions the imprinted polymer film was used to detect different concentrations of melamine in standard solutions and real milk samples. Compared with the nonimprinted polymer (NIP), the molecularly imprinted polymer (MIP) film showed higher affinity and sensitivity towards melamine with a linear range, quantification limit and detection limit of 0.5-200 nM, 1.375 nM and 0.413 nM respectively. Furthermore, the polymer blend film showed good selectivity toward melamine, stability, reproducibility and practical applications for the determination of melamine in infant formula milk with the recovery of 92.32-102.49%. The doping of the polymer with oxalic acid enhanced the conductivity and sensitivity of the sensor.

Enhancement anti-interference ability of photoelectrochemical sensor via differential molecularly imprinting technique demonstrated by dopamine determination

Molecularly imprinting polymers (MIPs), as artificial antibodies with high recognition selectivity to template molecules, are widely used in various biosensors. To improve further the selectivity of MIPs-based photoelectrochemical (PEC) biosensors, we report a differential strategy using non-imprinted polymers (NIPs) as the reference. In a proof-to-concept example for the determination of dopamine (DA), MIPs and NIPs membranes were fabricated by electrochemical polymerization of polypyrrole membranes on the surface of graphene quantum dots (GQDs)/TiO2 nanotubes (NTs). The photocurrent difference between the two PEC cells, MIPs@GQDs/TiO2 NTs−Pt and NIPs@GQDs/TiO2 NTs−Pt, was measured as the signal. As the non-specific adsorption of non-template molecules on the outside surface of MIPs and NIPs membranes is similar, the anti-interference ability for the determination of DA is much improved by using differential strategy. In the normal and differential PEC measurement models, 10.0 μM ascorbic acid is equivalent to 3.12 and 0.40 μM DA, respectively. Further, the smaller specific surface area in NIPs membrane was compensated by using a weight factor to correct the residual interference in a modified differential model. By using 10.0 μM ascorbic acid as the balance point, the presence of 10.0 μM H2O2, glutathione, uric acid or glucose is equivalent only to 0.090, 0.061,0.11 or 0.041 μM of DA, respectively, which are about 3–7% of their interference levels in the normal photocurrent model. The differential PEC method was applied in the determination of DA in serum samples in the linear range of 0.05–12.5 μM, with the detection limit of 0.018 μM.

The molecular imprinting effect of propranolol and dibenzylamine as model templates: Binding strength and selectivity

Recent studies have shown anomalies with the most studied non-covalent molecularly imprinted polymer, the propranolol imprinted one. This imprinted polymer, like many others, binds more template than the non-imprinted control polymer, but its selectivity in template adsorption is only slightly or not at all improved by imprinting, depending on the compound compared. The reasons for this anomaly are discovered here. Simple experiments show that acid homoassociation in the prepolymerisation complex is the likely cause of the anomaly. The specific conductivity of prepolymerization mixtures at different functional monomer to template ratios follows a pattern observed in homoassociating systems. Analysis of the optimal prepolymerization mixture shows that on average two molecules of the functional monomer are complexed to the basic template, even if the template lacks any other hydrogen bonding functional group than the amino group. Molecular modeling calculations provide the structure and stability of the homoassociated prepolymerization complexes. These results lead to a plausible interpretation of the anomaly, which may not be unique for the propranolol imprinted polymer, but may affect all imprinted polymers made for basic templates by using acidic functional monomers. The analytical applications of the new imprinting model are demonstrated.

Delayed Addition of Template Molecules Enhances the Binding Properties of Diclofenac-Imprinted Polymers.

It has been reported that in the molecular imprinting technique, the use of preformed oligomers instead of functional monomers increases the stability of the non-covalent interactions with the template molecule, providing a sharp gain in terms of binding properties for the resulting imprinted polymer. Based on this theory, we assumed that the delayed addition of template molecules to a polymerization mixture enhances the binding properties of the resulting polymer. To verify this hypothesis, we imprinted several mixtures of 4-vinylpyridine/ethylene dimethacrylate (1:6 mol/mol) in acetonitrile by adding diclofenac progressively later from the beginning of the polymerization process. After polymerization, the binding isotherms of imprinted and non-imprinted materials were measured in acetonitrile by partition equilibrium experiments. Binding data confirm our hypothesis, as imprinted polymers prepared by delayed addition, with delay times of 5 and 10 min, showed higher binding affinity (Keq = 1.37 × 104 L mol−1 and 1.80 × 104 L mol−1) than the polymer obtained in the presence of template at the beginning (Keq = 5.30 × 103 L mol−1). Similarly, an increase in the imprinting factor measured vs. the non-imprinted polymer in the binding selectivity with respect to mefenamic acid was observed. We believe that the delayed addition approach could be useful in prepar imprinted polymers with higher binding affinity and increased binding selectivity in cases of difficult imprinting polymerization.

Amino-functionalised silica-grafted molecularly imprinted polymers for chloramphenicol adsorption

This research investigated the liquid-phase removal of chloramphenicol (CAP), an emerging contaminant using molecularly imprinted polymers (MIPs). CAP adsorption profiles, equilibrium, and kinetics were analysed. The adsorption performance was compared between MIPs and non-imprinted polymers (NIPs), both with silica or without silica grafting. The imprinting factor (IF) values for the [email protected] were significantly higher than the IF values for MIPs-CAP adsorbent at pH 8. The kinetics of CAP adsorption was fitted to pseudo-second-order kinetics models for MIPs-CAP (R2 = 0.9998) and [email protected] (R2 = 0.9999). The adsorption isotherm of [email protected] was well represented by the Langmuir model (R2 = 0.9991), while the Freundlich isotherm model (R2 = 0.9998) provided the best fit for MIPs-CAP. The maximum monolayer adsorption capacities, Qmax, for [email protected] (32.26 mg g−1) were higher than the Qmax for [email protected] (29.6 mg g−1). These results suggested that the silica-grafted molecularly imprinted polymers can be employed as a potential water-compatible adsorbent for the selective adsorption and removal of CAP from aqueous phase.

A model study by using polymeric molecular imprinting nanomaterials for removal of penicillin G.

We aimed to develop a molecularly imprinted polymeric systems with using penicillin G as a template molecule for removal of the antibiotic residues from environmental samples. Firstly, Pen-G-imprinted poly (2-hydroxyethyl methacrylate-N-methacryloyl-L-alanine) [p(HEMA-MAAL)] nanopolymers were synthesized by surfactant-free emulsion polymerization method. Then, template molecule (Pen-G) was extracted from nanopolymers. Synthesized nanopolymers were characterized by different methods such as Fourier-transform infrared spectroscopy (FTIR), elemental and zeta-size analysis, scanning electron microscope (SEM), and surface area calculations. Nanopolymers have 60.38nm average size and 1034.22m2/g specific surface area. System parameters on Pen-G adsorption onto Pen-G imprint nanopolymers were investigated at different conditions. The specific adsorption value (Qmax) of molecularly impirinted p(HEMA-MAAL) nanopolymers was found 71.91g/g for Pen-G in 5mg/mL Pen-G initial concentration. Pen-G adsorption of molecularly imprinted nanopolymers was 15 times more than non-imprinted polymer. It is shown that obtained p(HEMA-MAAL) nanopolymer was a reuseable product which protected its adsorption capacity of 98.9% after 5th adsorption-desorption cycle. In conclusion, we suggest a method to develop a nanostructure, selective, low-cost molecularly imprinted polymeric systems with using penicillin G as a template molecule for removal of the antibiotic residues.

Preparation of molecular imprinted polymer based on attapulgite and evaluation of its performance for adsorption of benzoic acid in water.

In order to reduce the environmental impact of benzoic acid (BA), molecular imprinted polymers based on attapulgite were facilely prepared by molecular imprinted technique. The samples were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermal gravimetric analysis. The adsorption performance, regeneration stability, and competitive selectivity of BA by benzoic acid-surface molecular imprinted polymers (BA-MIP) were systematically investigated by experiments. For this material, it has a high adsorption capacity of 41 mg/g and an equilibrium adsorption time of about 150 min. Compared with non-imprinted polymers, BA-MIP has a higher adsorption capacity for BA, and the dynamic adsorption behavior of BA by both of them conforms to the quasi-second-order kinetic model. The Langmuir adsorption isotherm equation was fitted the isothermal adsorption experiment. The thermodynamic analysis shows that the adsorption process is an exothermic reaction. The adsorption capacity of BA first increases and then decreases with an increase in pH, and the maximum adsorption capacity is reached at pH = 5. BA-MIP also has excellent selective adsorption capacity and regeneration stability for BA.

Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice

The objective of this study was to explore the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules. Here, R-, S- and R/S-1-aminoindanes (TR, TS and TR/S) were used as the model template molecules. Optimization of synthetic protocols facilitated preselection of the most efficient composition for a molecularly imprinted polymer (MIP)—methacrylic acid-co-ethylene glycol dimethacrylate—with satisfactory specificity and an imprinting factor equal to 3. This polymer composition was used further to analyse the effect of configuration of the template on adsorption properties. The results showed preferable adsorption of R-enantiomer, TR in the R-MIP and S-enantiomer, TS in the S-MIP but revealed variations in the binding capacities of TR and TS in the R- and S-cavity (stereoselectivity factor; k = 1.66 to 1.22, respectively). The theoretically analysed binding energies (ΔEB) of both TR and TS in the R-cavity (ΔEB = − 506.14 to − 256.77 kcal mol−1) and S-cavity (ΔEB = − 302.42 to − 347.18 kcal mol−1) were in agreement with empirical data. Morphology and porosity analyses revealed the impact of the template molecule on the pore system of the MIP and control (a non-imprinted polymer), but enantiomers were only found to have a negligible role. Binding characterization revealed that the physisorption-governed adsorption process and Dubinin–Radushkevich model fitted the experimental data best. Finally, terahertz spectroscopy was employed to confirm the similarity between both materials imprinted by each enantiomer.

A turn-on fluorescent ion-imprinted polymer for selective and reliable optosensing of lead in real water samples

A new fluorescent Pb(II) imprinted polymer (Pb(II)–IIP) was synthesized for the selective detection of this contaminant in natural water. To play the sensing role, a fluorescent probe specific to Pb(II), based on anthracene coupled to 5-amino-8-hydroxyquinoline and a styrene moiety, was used as a functional monomer. It was associated with ethylene glycol dimethacrylate as cross-linker (EGDMA) to prepare microbeads of IIP and NIP (corresponding non-imprinted polymer) via precipitation polymerisation in DMSO-2-methoxyethanol (1:1, v/v) mixture. Solid-state 13C NMR spectroscopy was used to analyse the structure of the polymers and attest the integration of the fluorescent monomer in the polymer matrix. The morphology of the prepared materials was analysed by scanning electron microscopy and nitrogen adsorption/desorption. Results showed high mesoporous materials with important surface areas of 346 and 232 m2·g−1 for IIP and NIP, respectively. Polymers fluorescence properties revealed that the obtained IIP showed remarkably selective fluorescent on-off characteristics towards Pb(II) compared to NIP, emphasizing an imprinting effect. IIP fluorescent calibration curve exhibited a linear range from 7.1–60 μg·L−1 in pure water with a low limit of detection of 2.1 μg·L−1. The synthesized IIP was successfully applied to the determination of Pb(II) in tap water, mineral water and seawater samples.

Recognition and adsorption characteristics of tramadol hydrochloride molecules in molecular imprinted poly(MAA-co-EGDMA)

A simple method for adsorption and recognition of tramadol-HCl in molecular imprinted poly (methacrylic acid-co-ethylene glycol dimethacrylate); poly (MAA-co-EGDMA), is described. Seven tramadol imprinted polymers (TIPs) were synthesized based on tramadol hydrochloride as the template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, chloroform as a porogenic solvent and benzoyl peroxide (BP) as an initiator. Other seven non-imprinted polymers (NIPs) were prepared with the same compositions as the TIPs without the template molecule. A simple method for determination of Tramadol concentration by optical absorption method was described. The effects of crosslinker and functional monomer concentration, soaking time and the pH on the adsorption efficiency of tramadol by the polymers were studied. TIPs exhibited more adsorption affinity than their NIPs counterparts as they acquired recognition sites to capture the tramadol molecules. The TIP polymer with 15 mmol EGDMA and 1.15 mmol MAA stirred for 3h at 7 pH tramadol solution showed 90% adsorption capability for the tramadol, while the corresponding NIP sample showed 55.6% adsorption. SEM images showed the presence of (micro/meso/macro) pores in such TIP sample.

Characterization of Imprinted Polymer of Diazepam With Methacrylic Acid and Hydroxyethyl Methacrylate Monomer in Chloroform for Selective Adsorption of Diazepam

Diazepam is a benzodiazepine class usage is regulated nationally or globally. These drugs can be used to regulate sleep patterns or sedative-hypnotic drugs because it has a calming effect. Monitoring the abuse of diazepam requires a sensitive analysis methods that required the preparation of selective methods. One of the methods that are currently developing is Moleculary Imprinted Polymer-Solid Phase Extraction (MI-SPE). In this research, step being performed include determination of the association constant, synthesis sorbent of Imprinted Polymer (IP) diazepam by bulkpolymerization method with diazepam as a template, chloroform as porogen, two kind of monomer methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) as functional monomer. Templates extracted from polymer followed by evaluation of adsorption ability test, a test of capacity and selectivity of the polymer, and also the characterization of the IP using Fourier Transform Infra-Red (FTIR),and Scanning Electron Microscope (SEM). The results showed that IP diazepam with MAA monomer has 7.95 x 10-5 mg/g of capacity, it is better than capacity of IP diazepam monomer HEMA with 7.47x 10-6 mg/g. Selectivity of IP diazepam MAA monomer has an IF value which is 2.13, which is better than IP HEMA with 1.21. In addition, IP diazepam MAA monomer more heterogenous than its Non Imprinted Polymer (NIP).Keywords: Chloroform, Diazepam, HEMA, Methacrylic acid, MI-SPE.

Molecularly Imprinted Polymers for Recognition of Engineered Nanoparticles

Introduction Engineered nanoparticles (ENPs) have found widespread use in modern technology, medicine and daily life. Ag-NPs for example are used as antimicrobials in several medical and cosmetic products, whereas Au-NPs have attracted great interest in medical applications, such as drug delivery systems. However, ENPs can potentially cause adverse toxic effects due to their small size and high surface to volume ratio and their increased utilization in different medical and consumer products leads to an increased exposure to humans. While a range of state-of-the-art technologies, such as ICP-MS, is available for the detection of ENPs, they usually require thorough sample preparation, highly trained personnel and expensive equipment. [1]To circumvent these limitations, the use of artificial recognition materials, as for instance molecularly imprinted polymers (MIPs), is a promising alternative. MIPs are synthesized via (radical) polymerization in the presence of template molecules. After template removal, cavities, which are complementary to the template in size, shape and chemical functionality, form in the material. These can rebind target molecules with high sensitivity and selectivity. [2] MIPs can be used as receptors for quartz-crystal microbalances (QCMs), which are mass-sensitive transducers that measure a change in mass via a change in resonant frequency of the oscillating quartz. [3]In this work, we report on developing an easy-to-use and low-cost MIP-based QCM sensor for detection of ENPs in aqueous matrices. Method Stamps with immobilized metal-based NPs were used to imprint template material on PU layers. Particle distribution and shape of NPs, immobilized on PDMS stamps, were analyzed using atomic force microscopy (AFM). MIPs were prepared by pressing NP-stamps onto PU layers. After polymerization overnight, stamps were removed and remaining NPs were washed off the surface. MIPs were characterized via AFM and QCM. In case of QCM, we utilized an in-house dual-electrode system. In that case, one of the two electrode pairs served as reference and was coated with the non-imprinted polymer (NIP) to compensate for external effects, such as temperature changes. Results and Discussion Two different imprinting strategies were tested for fabrication of NP MIPs: bulk and surface imprinting. Bulk imprinting did not result in cavity formation on the polymer surface as examined via AFM. Consequently, we could not observe any significant differences of sensor signals between MIP and NIP during QCM measurements. In contrast to this, surface imprinting led to more favorable outcomes. NP-stamps were used for that purpose and characterized using AFM to verify the presence of NPs on stamp surfaces. As shown in Figure 1a, NPs are distributed evenly across the surface. Figure 1b displays an AFM image of the corresponding imprinted PU layer, which clearly reveals cavities on the polymer surface, matching the template in size and shape, thus confirming successful NP imprinting. In addition, an image of the reference, the non-imprinted polymer (NIP), is given for comparison, bearing no binding sites on the polymer surface (Figure 1c).Frequency measurements of MIP and NIP coated QCMs resulted in reversible and concentration-dependent sensor responses with no cross-selectivity to larger NPs. Furthermore, frequency shifts of MIPs, caused upon injection of NP solution, were much higher than those of NIPs. Fist results on acrylate-based MIPs using self-initiating monomers seem promising. First QCM measurements revealed incorporation of NPs by MIPs, with a way higher sensor response compared to the NIP. However, there is still room for improvement regarding batch-to-batch reproducibility. Further characterization of these sensing materials is necessary and still ongoing. Conclusion and Outlook Imprinting of thin polymer-films using metal-based ENPs is a novel concept with considerable potential in the field of sensor technology. PU-based MIPs were prepared by surface imprinting and characterized using AFM, revealing corresponding NP cavities on the polymer surface and thus confirming successful imprinting of NPs. Moreover, frequency measurements of MIP coated QCMs led to sensor responses in a reversible and quantitative manner. In the near future, selectivity studies will be performed in order to assess binding responses as a function of NP size, stabilizer and core material. Moreover, surface morphology of MIPs will be further characterized using PeakForce QNM.Overall, this work demonstrates the potential use of MIPs for analysis of NPs in complex matrices, such as food, cosmetic or medical products. Acknowledgements This work has been funded by the Austrian Science Fund FWF, project number I 3568-N28, which we gratefully acknowledge.