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A visual observation of the bending angle changes for the novel and easy detection of proteins is introduced in this study by fabricating bovine serum albumin (BSA) imprinted hydrogel strips with a one sided 3D porous structure using a combination of polystyrene colloidal crystal templating and the molecular imprinting approach using BSA as the template protein and several functional monomers. [ABSTRACT FROM AUTHOR]

Surface imprinting used for template recognition in nanocavities can be controlled and improved by surface morphological changes. Generally, the lithographic technique is used for surface patterning concerning sensing signal amplification in molecularly imprinted polymer (MIP) thin films. In this paper, we describe the effects of silanized silica molds on sensing the properties of MIP films. Porous imprinted poly(MAA–co–EGDMA) films were lithographically fabricated using silanized or non-treated normal silica replica molds to detect 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide as the standard template. The silanized mold MIP film (st-MIP) (Δf = −1021 Hz) exhibited a better sensing response than the non-treated normal MIP (n-MIP) (Δf = −978 Hz) because the imprinting effects, which occurred via functional groups on the silica surface, could be reduced through silane modification. Particularly, two non-imprinted (NIP) films (st-NIP and n-NIP) exhibited significantly different sensing responses. The st-NIP (Δfst-NIP = −332 Hz) films exhibited lower Δf values than the n-NIP film (Δfn-NIP = −610 Hz) owing to the remarkably reduced functionality against nonspecific adsorption. This phenomenon led to different imprinting factor (IF) values for the two MIP films (IFst-MIP = 3.38 and IFn-MIP = 1.86), which was calculated from the adsorbed 2,4-D mass per poly(MAA–co–EGDMA) unit weight (i.e., QMIP/QNIP). Moreover, it was found that the st-MIP film had better selectivity than the n-MIP film based on the sensing response of analogous herbicide solutions. As a result, it was revealed that the patterned molds' chemical surface modification, which controls the surface functionality of imprinted films during photopolymerization, plays a role in fabricating enhanced sensing properties in patterned MIP films. [ABSTRACT FROM AUTHOR]

This study successfully fabricated BPA-imprinted poly(4-vinylpyridine-co-ethylene glycol dimethacrylate) (poly(4-VP-co-EGDMA)) quartz crystal microbalance (MIP-QCM) sensors on a silica skeleton surface and gold pinholes of silica inverse opal through surface-initiated atom transfer radical polymerization (SI-ATRP). The sensing features of the two MIP films on the structured silica surface and nano-scale local gold surface were investigated by measuring the resonant frequency change (∆f) in QCM sensors. The ∆f values for the p-MIP (MIP on gold pinholes) and s-MIP films (MIP on silica skeleton surface) were obtained with the ∆f value of −199 ± 4.9 Hz and −376 ± 19.1 Hz, respectively, whereas for p-/s-NIP films, the ∆f values were observed to be −115 ± 19.2 Hz and −174 ± 5.8 Hz by the influence of non-specific adsorption on the surface of the films. Additionally, the imprinting factor (IF) appeared to be 1.72 for p-MIP film and 2.15 for s-MIP film, and the limits of quantitation (LOQ) and detection (LOD) were 54.924 and 18.125 nM (p-MIP film) and 38.419 and 12.678 nM (s-MIP film), respectively. Using the Freundlich isotherm model, the binding affinity of the BPA-imprinted films was evaluated. This was measured in an aqueous solution of BPA whose concentration ranged between 45 and 225 nM. It was found that the p-MIP film (m = 0.39) was relatively more heterogeneous than the s-MIP film (m = 0.33), both of which were obtained from the slope of the linear regressions. Finally, the selectivity of the MIP-QCM sensors for BPA detection was determined by measuring the effect of other analogous chemicals, such as bisphenol F (BPF), bisphenol AP (BPAP), and bisphenol B (BPB), in aqueous solutions. The selectivity coefficients (k*) of the two MIP films had ~1.9 for the p-MIP and ~2.3 for the s-MIP films, respectively. The results reveal that, with respect to signal amplification of the QCM sensors, the s-MIP film has better sensing features and faster detection responses than the p-MIP film. [ABSTRACT FROM AUTHOR]

In this study, protein-imprinted sensors with thin bulk films were electrochemically fabricated on gold-coated quartz crystal electrodes with hemispherical porous gold patterns for detecting trypsin (Trp). The gold patterns were electrodeposited on a polystyrene colloidal monolayer and then rinsed using toluene. For Trp imprinting on the gold patterned electrodes, a thin layer with a poly(o -phenylenediamine) and Trp protein was formed using a cyclic voltammetry method under optimized conditions. In addition, a two-dimensional molecularly imprinted polymer (2D-MIP) film was prepared on a planar gold electrode under the same conditions to compare to the dependence of Trp selective recognition on three-dimensional (3D) thin MIP structure, and each corresponding nonimprinted polymer film were constructed by electropolymerization, in the absence of Trp template, to compare molecular imprinting effects. The sensing properties of Trp imprinted sensors were investigated using electrochemical, such as cyclic voltammetry and electrochemical impedance spectroscopy, and microgravimetric methods to confirm the sensitivity and selectivity of MIP films. The 3D-MIP films demonstrated a higher imprinting factor (3.51) in 48-μg/mL of Trp concentration than the 2D-MIP film, and the limit of detection was calculated to be 70.9-ng/mL. In addition, the films exhibited higher electrochemical sensing responses due to increased Trp recognition by the effective molecular imprinting over a larger surface area. Thus, the construction of 3D-MIP films for the protein imprinting could provide excellent specificity, faster kinetics, and higher sensitivity for detecting macromolecular proteins than 2D-MIP films. [Display omitted] • Trypsin-imprinted sensors. • Gold-coated quartz crystal electrodes with hemispherical porous gold patterns. • Electropolymerized poly(o -phenylenediamine) for protein imprinting. • Electrochemical and microgravimetric sensing responses on molecularly imprinted polymers. • High sensitivity and selectivity in detecting trypsin. [ABSTRACT FROM AUTHOR]

Here, we developed extended-gate field-effect transistor (EG-FET)-based chemosensors with molecularly imprinted polymers (MIPs) on a gold-dendritic (AD) electrode to detect tumor necrosis factor-α (TNF-α) in serum. The poly(β-cyclodextrin) film was electrochemically prepared on the AD electrode using a potentiodynamic technique, followed by TNF-α immobilization by host-guest interaction. The MIP film was formed via electropolymerization of thiophene-3-amidoxime (T3A) monomer in PBS solution with one scan cycle at an applied voltage of 0–1.2 V. After electrochemical optimization, the sensing behavior (based on drain current, I ds) of the MIP films was investigated to explore the validity of the sensors, resulting in excellent reproducibility, reusability, and stability. Based on the Δ I ds – C TNF-α regression curves obtained in serum containing various analyte concentrations, the imprinting factor (IF) of MIP-based EG-FET sensor was 5.55. The selectivity was evaluated by comparing sensing property using analogous cytokine proteins (interleukin 1β [IL-1β] and interleukin-6 [IL-6]). The MIP-based EG-FET sensors exhibited high sensitivity (LOD: 0.55 pg/mL, LOQ: 1.82 pg/mL) and excellent selectivity (coefficient (α)> 3). Based on the excellent sensing performances, including high sensitivity and selectivity, excellent reproducibility, robustness, reusability, and stability, our (EG-FET)-based chemosensor with TNF-α-recognizing MIP film can be used for the early diagnosis and point–of–care of immune-related diseases. [Display omitted] • Highly selective detection of serum TNF-α was achieved. • Extended-gate field-effect transistors (EG-FETs) were employed for TNF-α sensing. • A poly (β-CD) layer was electrodeposited on gold dendrite electrodes. • The TNF-α template self-assembled on a poly(β-CD) layer. • Protein imprinting was performed on modified electrodes for TNF-α detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Patterned formaldehyde-imprinted poly(TFMAA-–co–EGDMA–co–ST) films were fabricated using colloidal lithography and photosynthesis. • The porous MIP–QCM sensor showed the more enhanced sensing features rather than the planar MIP film. • The adsorption isotherms and kinetics of the formaldehyde-imprinted films were evaluated using nonlinear fitting models. • The selectivity features of the porous MIP film for formaldehyde detection were investigated. In this study, formaldehyde (HCHO)-imprinted hemispherical pore-patterned thin films, consisting of poly(2-(trifluoromethyl)acrylic acid–co–ethylene glycol dimethacrylate–co–styrene) (poly(TFMAA–co–EGDMA–co–ST)), were fabricated using the design of molecularly imprinted polymers (MIPs) and a subsequent lithographic micro/nanoimprinting method to amplify HCHO sensing signals in quartz crystal microbalance (QCM) sensors. Its molecular imprinting condition was optimized by controlling the added amount of a ST monomer in a MIP precursor solution. From the resonant frequency change with respect to HCHO adsorption, the imprinting factor of the porous MIP film was calculated to have a value of 2.38 and the sensitivity (0.132 mg g−1 ppm−1) of the porous MIP film exhibited markedly improved characteristics with respect to the porous non-imprinted polymer (NIP) film (0.05 mg g−1 ppm−1). The selectivity of the MIP-QCM sensors for the detection of HCHO was examined in the presence of other analogous toxic gases such as hydrogen chloride and hydrogen fluoride. The HCHO-absorbed porous MIP film had higher selective features with selectivity coefficients (k * ≈ 3.83 (HCl) and 4.46 (HF)) than porous NIP films (k * ≈ 1.53 (HCl) and 2.20 (HF)). Moreover, the relative selectivity of the porous MIP film appeared to be 2.03–2.5, which was higher than those of the planar MIP film (1.70–1.73). [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA), which is extensively used in the plastic industry, is a known endocrine disrupting chemical whose release into the environment from industrial products is detrimental to human health. In this study, to characterize BPA-detectable imprinted films on quartz crystals (QCs), sensitive molecularly imprinted quartz crystal microbalance (MIP-QCM) sensors were fabricated. The MIP films were synthesized on 2D porous SiO 2 and Au pinholes that were generally observed from replica structures prepared using a polystyrene colloidal monolayer as an insulating mold. For MIP film formation, surface-initiated atom transfer radical polymerization was precisely controlled to adjust the MIP film growth on initiator-modified porous structures. Note that three BPA-imprinted poly(4-VP-co-EGDMA) films, i.e., MIP(8-h), MIP(16-h), and MIP(24-h), under reaction time control were successfully prepared. Furthermore, all imprinted patterned surfaces were characterized via atomic force microscopy (AFM) and scanning electron microscopy (SEM). The MIP(24-h) film demonstrated the highest imprinting factor (i.e., IF ≈ 2.4) and sensitivity (i.e., 1.219 ± 0.079 Hz nM−1), although the maximum binding capacity (Q max) and binding capacity (Q e) at 1-h rebinding equilibrium was relatively lesser than those of the MIP(8-h) and MIP(16-h) owing to the differentiation of the deposited MIP mass. Using the Freundlich isotherm model, the binding affinity of the BPA imprinted MIP films measured in an aqueous solution of BPA whose concentration ranged between 45 and 225 nM was evaluated. Finally, the selectivity of the MIP-QCM sensors for BPA detection was investigated in aqueous solutions in the presence of other analogous chemicals such as bisphenol F (BPF), bisphenol AP (BPAP), and bisphenol B (BPB). The MIP(8-h) film showed extremely high recovery percentage (≈ 94.54 %) owing to the relatively thinner film formation, which was significantly comparable with that of other MIP films, i.e., 68.37 % for MIP(16-h) and 61.99 % for MIP(24-h). However, the MIP(24-h) film appeared to have higher selective features with selectivity coefficients and relative selectivity (k * and k ' ≈ 2.5, respectively) despite measurement in a limited period (i.e., 1-h rebinding process). • Bisphenol A-imprinted poly(4-VP-co-EGDMA) films were synthesized via surface-initiated atom transfer radical polymerization. • The MIP–QCM (MIP-24h) sensor showed the more enhanced sensing features rather than other MIP films. • The binding affinity of the Bisphenol A-imprinted films was evaluated using the Freundlich isotherm model. • The selectivity of the structured MIP films for Bisphenol A detection was investigated. [ABSTRACT FROM AUTHOR]