Pyrrole–phenylboronic acid: A novel monomer for dopamine recognition and detection based on imprinted electrochemical sensor

A ratiometric molecular imprinted electrochemiluminescence sensor based on enhanced luminescence of CdSe@ZnS quantum dots by MXene@NaAsc for detecting uric acid

An unlabeled ratiometric molecular imprinted electrochemiluminescence sensor was developed for the determination of trace uric acid, based on MXene@NaAsc nanocomposites, CdSe@ZnS quantum dots and molecularly imprinted polymer composites modified glass carbon electrode. MXene@NaAsc stably enhanced the electron transfer and improved electrochemiluminescence intensity by acting as a base platform and signal amplifier for CdSe@ZnS quantum dots. Specific molecular imprinting cavities based on electropolymerization with o-phenylenediamine were formed to specifically identify uric acid. Combining the good sensitivity of electrochemiluminescence and the excellent selectivity of molecularly imprinted polymer, the ratio of optical signal and electrical signal was used as a comprehensive signal to achieve the detection of uric acid. Based on this, uric acid was detected in the range from 1 × 10-10 to 1 × 10-4 mol/L with the LOD of 18.13 pmol/L (S/N = 3). The developed sensor with easy preparation, great selectivity and excellent sensitivity could successfully detect uric acid in human serum.

Bacteria-imprinted impedimetric sensor based on doping-induced nanostructured polypyrrole for determination of Escherichia coli

A simple and label-free bacteria-imprinted impedimetric (BIP) sensor for the sensitive measurement of Escherichia coli has been developed. The BIP sensor is fabricated by one-step electropolymerization of pyrrole (functional monomer), copper phthalocyanine-3, 4', 4'', 4'''-tetrasulfonic acid tetrasodium salt (CuPcTs, dopant), and target bacteria (E. coli O157:H7) on a glassy carbon electrode. After the removal of the bacterial template, the established imprinted sites on the CuPcTs-doped polypyrrole film (PPy/CuPcTs) enable the highly selective rebinding of target bacteria and the resulting impedance change of the sensing interface is used to detect the target bacteria. We found that during the electropolymerization process, CuPcTs induced pyrrole to form granular-like nanostructured PPy/CuPcTs with excellent conductivity compared with the PPy film, substantially improving the sensitivity of the proposed sensor. The sensor presented a wide detection range (102 ~ 107 CFU⋅mL-1, RSD 1.1% ~ 3.5%) with a limit of detection of 21 CFU⋅mL-1. Furthermore, the proposed sensor effectively distinguished E. coli O157:H7 from other non-target bacteria and exhibited good practicality with recoveries from 91 to 103% in spiked real samples, indicating the potential utility of the sensor in food safety and environmental monitoring.

Specific capture and determination of glycoprotein using a hybrid epitopes and monomers-mediated molecular-imprinted polymer enzyme-free electrochemical biosensor

A novel molecular-imprinted polymer (MIP)-based enzyme-free biosensor was created for the selective detection of glycoprotein transferrin (Trf). For this purpose, MIP-based biosensor for Trf was prepared by electrochemical co-polymerization of novel hybrid monomers 3-aminophenylboronic acid (M-APBA) and pyrrole on a glassy carbon electrode (GCE) modified with carboxylated multi-walled carbon nanotubes (cMWCNTs). Hybrid epitopes of Trf (C-terminal fragment and glycan) have been selected as templates. The produced sensor exhibited great selective recognition ability toward Trf under optimal preparation conditions, offering good analytical range (0.125-1.25 μM) with a detection limit of 0.024 μM. The proposed hybrid epitope in combination with hybrid monomer-mediated imprinting strategy was successfully applied to detect Trf in spiked human serum samples, with recoveries and relative standard deviations ranging from 94.7 to 106.0% and 2.64 to 5.32%, respectively. This study provided a reliable protocol for preparing hybrid epitopes and monomers-mediated MIP for the synergistic and effective determination of glycoprotein in complicated biological samples.

A Universal Bacterial Catcher Au-PMBA-Nanocrab-Based Lateral Flow Immunoassay for Rapid Pathogens Detection

In traditional lateral flow immunoassays (LFIA) for pathogens detection, capture antibody (CA) is necessary and usually conjugated to Au nanoparticles (NPs) in order to label the target analyte. However, the acquisition process of the Au-CA nanoprobe is relatively complicated and costly, which will limit the application of LFIA. Herein, p-mercaptophenylboronic acid-modified Au NPs (namely Au-PMBA nanocrabs), were synthesized and applied for a new CA-independent LFIA method. The stable Au-PMBA nanocrabs showed outstanding capability to capture both Gram-negative bacteria and Gram-positive bacteria through covalent bonding. The acquired Au-PMBA-bacteria complexes were dropped onto the strip, and then captured by the detection antibody on the test line (T-line). Take Escherichia coli O157:H7 as an example, the gray value of T-line was proportional to the bacteria concentration and the linear range was 10³-10⁷ cfu·mL^-1. This CA-independent strategy exhibited higher sensitivity than the traditional CA-dependent double antibody sandwich method, because detection limit of the former one was 10³ cfu·mL^-1 only by visual observation, which was reduced by 3 orders of magnitude. Besides, this platform successfully screened E. coli O157:H7 in four food samples with recoveries ranging from 90.25% to 107.25%. This CA-independent LFIA showed great advantages and satisfactory potential for rapid foodborne pathogens detection in real samples.

Ultrasensitive electrochemiluminescence sensor based on perovskite quantum dots coated with molecularly imprinted polymer for prometryn determination

A highly effective molecularly imprinted electrochemiluminescence sensor was constructed for prometryn determination in environmental and biological samples by using perovskite quantum dots coated with a molecularly imprinted silica layer (MIP/CsPbBr₃-QDs) as the recognition and response element. MIP/CsPbBr₃-QDs were immobilized on a glassy carbon electrode (GCE) through electropolymerization, and the electrochemiluminescence (ECL) response of MIP/CsPbBr₃-QDs could be motivated under the condition of H₂O₂ as co-reactant. ECL signal was selectively quenched with prometryn by hindering electron transfer and directly proportional to the logarithm of prometryn concentration (0.10-500.0 μg/L) with a correlation coefficient of 0.9960. Limits of detection in fish and seawater samples were 0.010 μg/kg and 0.050 μg/L, respectively. Excellent recoveries of 88.0%-106.0% were acquired for fish and seawater samples with a relative standard deviation below 4.2%. The constructed MIECL sensor based on MIP/CsPbBr₃-QDs showed good stability, accuracy, and precision for sensitive detection of prometryn in aquaculture products and environmental samples.

Aptazyme-induced cascade amplification integrated with a volumetric bar-chart chip for highly sensitive detection of aflatoxin B1 and adenosine triphosphate

A triple-channel volumetric bar-chart chip based on aptazyme-induced cascade signal amplification empowers visual readout of aflatoxin B1 and adenosine triphosphate concentration.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

A new molecular imprinted PEDOT glassy carbon electrode for carbamazepine detection

An electrochemical sensor for the detection of carbamazepine was fabricated by the electropolymerization of PEDOT on glassy carbon electrodes. Molecular imprinted polymer sites were synthesized by cyclic voltammetry on the electrodes' surfaces providing high selectivity and sensitivity towards carbamazepine molecules. Scanning electron microscopy validated the formation of the polymer. Extraction of carbamazepine from the polymer was performed by immersion in acetonitrile and validated by ultraviolet-visible spectroscopy along with cyclic voltammetry experiments comparing pre- and post-template extraction data. Further cyclic voltammetry and square-wave voltammetry tests aided in characterizing the electrodes' response to carbamazepine concentration in PBS solution with [Fe(CN)₆]^3-/4- as a redox pair/mediator. The limits of detection and quantification were found to be 0.98 x 10^-3 M and 2.97 x 10^-3 M respectively. The biosensor was highly sensitive to carbamazepine molecules in comparison to non-imprinted electrodes, simple to construct and easy to operate.

Serially pH-Modulated Hydrogels Based on Boronate Ester and Polydopamine Linkages for Local Cancer Therapy

Elaborately and serially pH-modulated hydrogels possessing optimized viscoelastic natures for short gelation time and single syringe injection were designed for peritumoral injection of an anticancer agent. Boronate ester bonds between phenylboronic acid (PBA) (installed in HA-PBA (HP)) and dopamine (included in HA-dopamine (HD)) along with self-polymerization of dopamine (via interactions between HD conjugates) were introduced as the main cross-linking strategies of a hyaluronic acid (HA) hydrogel. Considering pK_a values (8.0-9.5) of PBA and dopamine, the pH of each polymer dispersion was controlled elaborately for injection through a single syringe, and the final pH was tuned nearby the physiological pH (pH 7.8). The shear-thinning behavior, self-healing property, and single syringe injectability of a designed hydrogel cross-linked nearby physiological pH may provide its convenient application to peritumoral injection and prolonged retention in local cancer therapy. Erlotinib (ERT) was encapsulated in a microsphere (MS), and it was further embedded in an HP/HD-based hydrogel for sustained and locoregional delivery. A rheologically tuned hydrogel containing an ERT MS exhibited superior tumor-suppressive efficiencies compared to the other groups in A549 tumor-bearing mice. A designed injectable hydrogel through a single syringe system may be efficiently applied to local cancer therapy with lower toxicities to healthy organs.

Construction of a selective non-enzymatic electrochemical sensor based on hollow nickel nanospheres/carbon dots–chitosan and molecularly imprinted polymer film for the detection of glucose

A non-enzymatic glucose electrochemical sensor platform was fabricated by assembling hollow nickel nanospheres/carbon dots–chitosan and molecularly imprinted polymer film modified a glass carbon electrode.

Fluorescent molecularly imprinted nanoparticles with boronate affinity for selective glycoprotein detection

Specific recognition and sensing of glycoproteins are of great importance in clinical diagnostics considering their frequent utilization as biomarkers and therapeutic targets. In this work, a biomimetic fluorescent sensor for the selective and sensitive detection of glycoprotein was developed, which was based on late-model boronate fluorescent molecularly imprinted nanoparticles (B-FMIP NPs). The B-FMIP NPs were fabricated via the macromolecular assembly of a fluorescent photo-crosslinkable amphiphilic copolymer containing boronic acid with glycoprotein in aqueous solution and in situ photo-crosslinking. Due to the synergism of boronate affinity and the molecular imprinting effect, the resultant B-FMIP NPs demonstrated specific recognition and remarkable selectivity toward the template glycoprotein (ovalbumin, OVA) with a high imprinted factor (α) of 6.0 and gave rise to obvious fluorescence quenching after binding with OVA in water. Under optimized experimental conditions, the as-prepared B-FMIP NPs exhibited linearity over the OVA concentration range of 10^-13 to 10^-3 mg mL^-1 with a detection limit of 3.3 × 10^-14 mg mL^-1, as well as a rapid response time (about 10 min), which was superior to that of other previously reported OVA sensors. Finally, these B-FMIP NPs have been applied for the determination of OVA in real samples.

Enzyme-mimicking accelerated signal enhancement for visually multiplexed quantitation of telomerase activity

Here, we propose an amplification strategy involving enzyme-mimicking accelerated signal enhancement integrated with a triple-channel volumetric bar-chart chip for visually multiplexed quantitation of telomerase activity. This platform was used for evaluating the telomerase activities from different kinds of cells and a detection limit at the single-cell level was realized without any instrumental assistance.

Label-free liquid crystal-based biosensor for detection of dopamine using DNA aptamer as a recognition probe

We present a label-free liquid crystal-based biosensor for the detection of dopamine (DA) in aqueous solutions using dopamine-binding aptamers (DBA) as recognition elements. In this system, the dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP) self-assembled monolayers immobilized on glass slides support the long alkyl chains that keep the liquid crystal (LC) molecules in a homeotropic orientation. Glutaraldehyde (GA) is used as a cross-linker to immobilize DBA onto the surface of glass slides. The specific binding of DA and DBA disrupts the homeotropic orientation of LCs, thereby inducing a change in the orientation from homeotropic to a random alignment. This orientation change can be converted and visualized simply as a transition from a dark optical LC image to a brighter image under a polarized optical microscope (POM), enabling the detection of DA. The developed LC-based aptasensor shows a good linear optical response towards DA in the very wide range of 1 pM-10 μM (0.19 pg/mL to 1.9 μg/mL) and has a very low detection limit of 10 pM (∼1.9 pg/mL). The biosensor also exhibited satisfactory selectivity and could be successfully applied to detect DA in human urine. The proposed LC-based aptamer sensing method offers a simple, rapid, highly sensitive and selective, and a label-free method for the analysis of DA in real clinical samples.

Ionic liquid assisted molecular self-assemble and molecular imprinting on gold nanoparticles decorated boron-doped ordered mesoporous carbon for the detection of zearalenone

Accurate and early diagnosis of zearalenone (ZEN) is particularly significant to the food safety. Herein, we propose an ionic liquid assisted self-assembly molecular imprinting strategy for ZEN based on ionic liquid functionalized boron-doped ordered mesoporous carbon -gold nanoparticles composite (BOMC-IL-Au NPs). During the composite synthesis, increased well-dispersed and uniform Au NPs are deposited on the surface of IL modified BOMC, due to the strong electrostatic interaction between AuCl₄^- and positively charged IL. For molecular imprinting, the BOMC-IL-Au NPs/GCE is immersed into p-aminothiophenol (p-ATP) solution and template solution in turn. Thus, the mercapto group contained p-ATP self-assembles on the Au NPs. Subsequently, the template molecules self-assemble onto the composite to form dense template layer, because of the hydrophobic interaction, π-π and hydrogen bond between template and IL/or p-ATP. After electropolymerization, the template layer is embedded into the p-ATP polymer membrane and produces lots of imprinting sites. Hence, the obtained sensor exhibits high sensitivity and selectivity. Under the optimal conditions, zearalenone can be quantified from 5 × 10^-4 to 1 ng mL^-1 with the low detection limit of 1 × 10^-4 ng mL^-1, by using [Fe(CN)₆]^3-/4- probe and square wave voltammetry. This strategy can also be employed to construct sensors for the detection of other substances.

High-Performance Conducting Polymer Nanotube-based Liquid-Ion Gated Field-Effect Transistor Aptasensor for Dopamine Exocytosis

In this study, ultrasensitive and precise detection of a representative brain hormone, dopamine (DA), was demonstrated using functional conducting polymer nanotubes modified with aptamers. A high-performance aptasensor was composed of interdigitated microelectrodes (IMEs), carboxylated polypyrrole nanotubes (CPNTs) and DA-specific aptamers. The biosensors were constructed by sequential conjugation of CPNTs and aptamer molecules on the IMEs, and the substrate was integrated into a liquid-ion gating system surrounded by pH 7.4 buffer as an electrolyte. To confirm DA exocytosis based on aptasensors, DA sensitivity and selectivity were monitored using liquid-ion gated field-effect transistors (FETs). The minimum detection level (MDL; 100 pM) of the aptasensors was determined, and their MDL was optimized by controlling the diameter of the CPNTs owing to their different capacities for aptamer introduction. The MDL of CPNT aptasensors is sufficient for discriminating between healthy and unhealthy individuals because the total DA concentration in the blood of normal person is generally determined to be ca. 0.5 to 6.2 ng/mL (3.9 to 40.5 nM) by high-performance liquid chromatography (HPLC) (this information was obtained from a guidebook “Evidence-Based Medicine 2018 SCL “ which was published by Seoul Clinical Laboratory). The CPNTs with the smaller diameters (CPNT2: ca. 120 nm) showed 100 times higher sensitivity and selectivity than the wider CPNTs (CPNT1: ca. 200 nm). Moreover, the aptasensors based on CPNTs had excellent DA discrimination in the presence of various neurotransmitters. Based on the excellent sensing properties of these aptasensors, the DA levels of exogeneous DA samples that were prepared from PC12 cells by a DA release assay were successfully measured by DA kits, and the aptasensor sensing properties were compared to those of standard DA reagents. Finally, the real-time response values to the various exogeneous DA release levels were similar to those of a standard DA aptasensor. Therefore, CPNT-based aptasensors provide efficient and rapid DA screening for neuron-mediated genetic diseases such as Parkinson’s disease.

Phenylboronic Acid-polymers for Biomedical Applications

Background:

Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area.

Methods:

We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications.

Results:

We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning.

Conclusion:

The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Capacitive Saccharide Sensor Based on Immobilized Phenylboronic Acid with Diol Specificity

A capacitive sensor for saccharide detection is described in this study. The detection is based on selective interaction between diols and aminophenylboronic acid (APBA) immobilized on a gold electrode. Glucose, fructose, and dextran (MW: 40 kDa) were tested with the system over wide concentration ranges (1.0 x 10-8 M - 1.0 x 10-3 M for glucose, 1.0 x 10-8 M - 1.0 x 10-2 M for fructose and 1.0 x 10-10 M - 1.0 x 10-5 M for dextran). The limits of detection (LODs) were 0.8 nM for glucose, 0.6 nM for fructose, and 13 pM for dextran. These data were comparable to the others reported previously. In order to demonstrate glycoprotein detection with the same sensor, human immunoglobulin G (IgG) as well as horseradish peroxidase were used as model analytes. The sensor responded to IgG in the concentration range of 1.0 x 10-13 M - 1.0 x 10-7 M with a LOD value of 16 fM. The performance of the assay of peroxidase was compared to a spectrophotometric assay by determining the enzymatic activity of a captured analyte. The results showed that the method might be useful for label-free, fast, and sensitive detection of saccharides as well as glycoproteins over a wide concentration range.

Enzyme-Free Plasmonic Biosensor for Direct Detection of Neurotransmitter Dopamine from Whole Blood

Complex biological fluids without pretreatment, separation, or purification impose stringent limitations on the practical deployment of label-free plasmonic biosensors for advanced assays needed in point of care applications. In this work, we present an enzyme-free plasmonic neurotransmitter dopamine biosensor integrated with a microfluidic plasma separator. This integrated device allows the in-line separation of plasma directly from the bloodstream and channels it to the active detection area, where inorganic cerium oxide nanoparticles function as local selective dopamine binding sites through strong surface redox reaction. A thorough understanding and engineering of the nanoparticles is carried out to maximize its dopamine sensitivity and selectivity. We obtain detection of dopamine at 100 fM concentration in simulated body fluid and 1 nM directly from blood without any prior sample preparation. The detection selectivity is found to be at least five-times higher compared to the common interfering species. This demonstration shows the feasibility of the practical implementation of the proposed plasmonic system in detection of variety of biomarkers directly from the complex biological fluids.

Electrochemical preparation of surface molecularly imprinted poly(3-aminophenylboronic acid)/MWCNTs nanocomposite for sensitive sensing of epinephrine

A nanocomposite with multi-walled carbon nanotubes (MWCNTs) coated with surface molecularly imprinted polymers (MIPs) poly(3-aminophenylboronic acid) (PAPBA) was successfully prepared via potentiodynamic electropolymerization and tested as an effective electrochemical material for epinephrine (EP) detection. The morphology and properties of the sensing material were characterized with scanning electron microscopy and electrochemical impedance spectroscopy. Compared with MWCNTs or non-imprinted polymers PAPBA modified MWCNTs electrodes, the PAPBA(MIPs)/MWCNTs modified electrode showed a lower charge transfer resistance and enhanced electrochemical performance for EP detection. The improved performance can be attributed to the large amount of specific imprinted cavities with boric acid group which can selectively adsorb EP molecule and the synergistic effect between MWCNTs and PAPBA(MIPs). The effects of pH, the molar ratio between monomer and template molecule, the cycle number of electropolymerization, and the accumulation time of the modified electrode on the sensing performance were investigated. It was found that under the optimal conditions, the PAPBA(MIPs)/MWCNTs sensor could effectively recognize EP from many possible interferents of higher concentration within a wide linear range of 0.2-800 μmol·L^-1, with low detection limit of 35 nmol·L^-1, high sensitivity and good discrimination. The detection of EP in human serum and real injection samples using the PAPBA(MIPs)/MWCNTs sensor also gave satisfactory results.

Highly selective and sensitive sensor based on an organic electrochemical transistor for the detection of ascorbic acid

In this study, an organic electrochemical transistor sensor (OECT) with a molecularly imprinted polymer (MIP)-modified gate electrode was prepared for the detection of ascorbic acid (AA). The combination of the amplification function of an OECT and the selective specificity of MIPs afforded a highly sensitive, selective OECT sensor. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were carried out to monitor the stepwise fabrication of the modified electrodes and the adsorption capacity of the MIP/Au electrodes. Atomic force microscopy was employed for examining the surface morphology of the electrodes. Important detection parameters, pH and detection temperature were optimized. With the change in the relative concentration of AA from 1μM to 100μM, the MIP-OECT sensor exhibited a low detection limit of 10nM (S/N > 3) and a sensitivity of 75.3μA channel current change per decade under optimal conditions. In addition, the MIP-OECT sensor exhibited excellent specific recognition ability to AA, which prevented the interference from other structurally similar compounds (e.g., aspartic acid, glucose, uric acid, glycine, glutathione, H₂O₂), and common metal ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, and Fe²⁺). In addition, a series of vitamin C beverages were analyzed to demonstrate the feasibility of the MIP-OECT sensor. Using the proposed principle, several other sensors with improved performance can be constructed via the modification of organic electrochemical transistors with appropriate MIP films.

Fluorescent Cell-Conjugation by a Multifunctional Polymer: A New Application of the Hantzsch Reaction

Multicomponent reactions (MCRs) can form unique structures with interesting functions, therefore, multifunctional polymers might be simply prepared using MCRs as coupling tools to simultaneously link and generate different functional groups. To verify this concept, a new fluorescent polymer containing phenylboronic acid has been facilely prepared via a one pot method by combining the Hantzsch reaction with reversible addition-fragmentation chain transfer (RAFT) polymerization. The Hantzsch-RAFT system has been found robust to smoothly achieve predesigned multifunctional polymer, which can be used for cell conjugation through the interaction between phenylboronic acid and glycoprotein on cell membrane. The conjugated cells could be directly observed due to the fluorescent Hantzsch moiety in the polymer chain, demonstrating a new application of the old Hantzsch reaction (>130 years) outside organic chemistry. Meanwhile, the conjugated cells remained excellent dispersity in the presence of coagulation protein (lectin), implying that multifunctional polymer a possible anticoagulant for cell separation. We believe that the current research paves a new way to exploit new applications of MCRs in interdisciplinary fields and might prompt the development of other multifunctional polymers based on different MCRs.

Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine

Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties.

Electrochemical bacterial detection using poly(3-aminophenylboronic acid)-based imprinted polymer

Biosensors can deliver the rapid bacterial detection that is needed in many fields including food safety, clinical diagnostics, biosafety and biosecurity. Whole-cell imprinted polymers have the potential to be applied as recognition elements in biosensors for selective bacterial detection. In this paper, we report on the use of 3-aminophenylboronic acid (3-APBA) for the electrochemical fabrication of a cell-imprinted polymer (CIP). The use of a monomer bearing a boronic acid group, with its ability to specifically interact with cis-diol, allowed the formation of a polymeric network presenting both morphological and chemical recognition abilities. A particularly beneficial feature of the proposed approach is the reversibility of the cis-diol-boronic group complex, which facilitates easy release of the captured bacterial cells and subsequent regeneration of the CIP. Staphylococcus epidermidis was used as the model target bacteria for the CIP and electrochemical impedance spectroscopy (EIS) was explored for the label-free detection of the target bacteria. The modified electrodes showed a linear response over the range of 10³-10⁷cfu/mL. A selectivity study also showed that the CIP could discriminate its target from non-target bacteria having similar shape. The CIPs had high affinity and specificity for bacterial detection and provided a switchable interface for easy removal of bacterial cell.

Synthesizing a nano-composite of BSA-capped Au nanoclusters/graphitic carbon nitride nanosheets as a new fluorescent probe for dopamine detection

A strong red fluorescent nanocomposite, consisting of graphite-like carbon nitride nanosheets (g-C₃N₄ NSs) and serum albumin-capped Au nanoclusters (AuNCs), was synthesized. Dopamine (DA) can quench the red fluorescence of the nanocomposite, based on the Forster resonance energy transfer (FRET) mechanism. In this quenching process, the energy is transferred from the fluorescent g-C₃N₄ NSs-AuNCs to the oxidized DA quinine molecules (DA is easily oxidated to form DA quinine in air). The red fluorescence emission at 420 nm decreases dramatically and the quenching ratio (F₀ - F)/F₀ is linearly related to the concentration of DA in the range of 0.05-8.0 μmol L^-1 with a detection limit of 0.018 μmol L^-1 (S/N = 3). Additionally, this sensor has a potential of application to assay the DA in the real samples, such as human serum and human urine.

Current data regarding the structure-toxicity relationship of boron-containing compounds

Boron is ubiquitous in nature, being an essential element of diverse cells. As a result, humans have had contact with boron containing compounds (BCCs) for a long time. During the 20th century, BCCs were developed as antiseptics, antibiotics, cosmetics and insecticides. Boric acid was freely used in the nosocomial environment as an antiseptic and sedative salt, leading to the death of patients and an important discovery about its critical toxicology for humans. Since then the many toxicological studies done in relation to BCCs have helped to establish the proper limits of their use. During the last 15 years, there has been a boom of research on the design and use of new, potent and efficient boron containing drugs, finding that the addition of boron to some known drugs increases their affinity and selectivity. This mini-review summarizes two aspects of BCCs: toxicological data found with experimental models, and the scarce but increasing data about the structure-activity relationship for toxicity and therapeutic use. As is the case with boron-free compounds, the biological activity of BCCs is related to their chemical structure. We discuss the use of new technology to discover potent and efficient BCCs for medicinal therapy by avoiding toxic effects.

Molecularly Imprinted Polymers Based Electrochemical Sensor for 2,4-Dichlorophenol Determination

A molecularly imprinted polymers based electrochemical sensor was fabricated by electropolymerizing pyrrole on a Fe₃O₄ nanoparticle modified glassy carbon electrode. The sensor showed highly catalytic ability for the oxidation of 2,4-dichlorophenol (2,4-DCP). Square wave voltammetry was used for the determination of 2,4-DCP. The oxidation peak currents were proportional to the concentrations of 2,4-DCP in the range of 0.04 to 2.0 µM, with a detection limit of 0.01 µM. The proposed sensor was successfully applied for the determination of 2,4-DCP in water samples giving satisfactory recoveries.