A glucose-sensing polymer

Single-Component Electroactive Polymer Architectures for Non-Enzymatic Glucose Sensing

Organic mixed ionic-electronic conductors (OMIECs) have emerged as promising materials for biological sensing, owing to their electrochemical activity, stability in an aqueous environment, and biocompatibility. Yet, OMIEC-based sensors rely predominantly on the use of composite matrices to enable stimuli-responsive functionality, which can exhibit issues with intercomponent interfacing. In this study, an approach is presented for non-enzymatic glucose detection by harnessing a newly synthesized functionalized monomer, EDOT-PBA. This monomer integrates electrically conducting and receptor moieties within a single organic component, obviating the need for complex composite preparation. By engineering the conditions for electrodeposition, two distinct polymer film architectures are developed: pristine PEDOT-PBA and molecularly imprinted PEDOT-PBA. Both architectures demonstrated proficient glucose binding and signal transduction capabilities. Notably, the molecularly imprinted polymer (MIP) architecture demonstrated faster stabilization upon glucose uptake while it also enabled a lower limit of detection, lower standard deviation, and a broader linear range in the sensor output signal compared to its non-imprinted counterpart. This material design not only provides a robust and efficient platform for glucose detection but also offers a blueprint for developing selective sensors for a diverse array of target molecules, by tuning the receptor units correspondingly.

Glucose-Responsive Insulin and Delivery Systems: Innovation and Translation

Type 1 and advanced type 2 diabetes treatment involves daily injections or continuous infusion of exogenous insulin aimed at regulating blood glucose levels in the normoglycemic range. However, current options for insulin therapy are limited by the risk of hypoglycemia and are associated with suboptimal glycemic control outcomes. Therefore, a range of glucose-responsive components that can undergo changes in conformation or show alterations in intermolecular binding capability in response to glucose stimulation has been studied for ultimate integration into closed-loop insulin delivery or "smart insulin" systems. Here, an overview of the evolution and recent progress in the development of molecular approaches for glucose-responsive insulin delivery systems, a rapidly growing subfield of precision medicine, is presented. Three central glucose-responsive moieties, including glucose oxidase, phenylboronic acid, and glucose-binding molecules are examined in detail. Future opportunities and challenges regarding translation are also discussed.

Superwettability-Based Interfacial Chemical Reactions

Superwetting interfaces arising from the cooperation of surface energy and multiscale micro/nanostructures are extensively studied in biological systems. Fundamental understandings gained from biological interfaces boost the control of wettability under different dimensionalities, such as 2D surfaces, 1D fibers and channels, and 3D architectures, thus permitting manipulation of the transport physics of liquids, gases, and ions, which profoundly impacts chemical reactions and material fabrication. In this context, the progress of new chemistry based on superwetting interfaces is highlighted, beginning with mass transport dynamics, including liquid, gas, and ion transport. In the following sections, the impacts of the superwettability-mediated transport dynamics on chemical reactions and material fabrication is discussed. Superwettability science has greatly enhanced the efficiency of chemical reactions, including photocatalytic, bioelectronic, electrochemical, and organic catalytic reactions, by realizing efficient mass transport. For material fabrication, superwetting interfaces are pivotal in the manipulation of the transport and microfluidic dynamics of liquids on solid surfaces, leading to the spatially regulated growth of low-dimensional single-crystalline arrays and high-quality polymer films. Finally, a perspective on future directions is presented.

Metal-Coordination-Assisted Folding and Guest Binding in Helical Aromatic Oligoamide Molecular Capsules

The development of foldamer-based receptors is driven by the design of monomers with specific properties. Herein, we introduce a pyridazine-pyridine-pyridazine diacid monomer and its incorporation into helical aromatic oligoamide foldamer containers. This monomer codes for a wide helix diameter and can sequester metal ions on the inner wall of the helix cavity. Crystallographic studies and NMR titrations show that part of the metal coordination sphere remains available and may then promote the binding of a guest within the cavity. In addition to metal coordination, binding of the guest is assisted by cooperative interactions with the helix host, thereby resulting in significant enhancements depending on the foldamer sequence, and in slow guest capture and release on the NMR time scale. In the absence of metal ions, the pyridazine-pyridine-pyridazine monomer promotes an extended conformation of the foldamer that results in aggregation, including the formation of an intertwined duplex.

Imprinting of Stöber particles for chirally-resolved adsorption of target monosaccharides and disaccharides

Soft imprinting of silica particles using sugar surfactants targets chirally resolved binding of saccharides.

Bioinspired synthesis of poly(phenylboronic acid) microgels with high glucose selectivity at physiological pH

A microgel that is more sensitive towards glucose than to other saccharides is made of 4-vinylphenylboronic acid crosslinked withN,N′-bis(propene)perylene-3,4,9,10-tetracarboxyldiimide.

Rapid, sensitive, and reusable detection of glucose by a robust radiofrequency integrated passive device biosensor chip

Tremendous demands for sensitive and reliable label-free biosensors have stimulated intensive research into developing miniaturized radiofrequency resonators for a wide range of biomedical applications. Here, we report the development of a robust, reusable radiofrequency resonator based integrated passive device biosensor chip fabricated on a gallium arsenide substrate for the detection of glucose in water-glucose solutions and sera. As a result of the highly concentrated electromagnetic energy between the two divisions of an intertwined spiral inductor coupled with an interdigital capacitor, the proposed glucose biosensor chip exhibits linear detection ranges with high sensitivity at center frequency. This biosensor, which has a sensitivity of up to 199 MHz/mgmL⁻¹ and a short response time of less than 2 sec, exhibited an ultralow detection limit of 0.033 μM and a reproducibility of 0.61% relative standard deviation. In addition, the quantities derived from the measured S-parameters, such as the propagation constant (γ), impedance (Z), resistance (R), inductance (L), conductance (G) and capacitance (C), enabled the effective multi-dimensional detection of glucose.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence-Based Laboratory Medicine Committee of the American Association for Clinical Chemistry jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (HbA(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of HbA(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence Based Laboratory Medicine Committee of the AACC jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (Hb A(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of Hb A(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Isomeric glucose recognition using molecularly imprinted polymer hydrogels

The goal of this research is to produce molecular imprinted polymers (MIPs), which selectively bind glucose over other sugars. MIP hydrogels against glucose exhibited binding capacities in excess of 0.6 grams of glucose per gram of dry gel in a 100 % DI H2O glucose solution, as well as in a 50–50 % glucose-fructose solution mixture. Equilibrium binding capacities of fructose were lower than those observed with respect to glucose, indicating an isomeric preference for the binding of glucose over fructose. Although it is expected that imprinted cavities will be distorted due to the swelling of the hydrogel in water, our experiments show that even the swollen gels exhibit remarkable glucose recognition. This synthetic and characterization methodology for MIPs might thus offer exciting avenues for novel biomimetic recognition and isomeric separation techniques.

Gels and microgels for nanotechnological applications

In recent years, "smart" materials have been the focus of considerable interest, from both fundamental and applied perspectives. Polymer gels are within this category; they respond to specific environmental stimuli by changing their size. Thus, the internal structure, the refractive index, and the mechanical properties of the polymer network change. They are considered super absorbent materials, as they can absorb solvent up to several hundred times their own weight. They respond rapidly to local environmental variations, an important fact in device miniaturization and microsensor developments. As size changes are accompanied by changes in internal dimensions, microgels have found application as carriers of therapeutic drugs and as diagnostic agents. They have also been used as microreactors, optically active materials, for template synthesis of nanoparticles or fabrication of artificial muscle. In this paper we review a set of application based on the special features associated to this systems. Basic concepts on the physical-chemistry of gel swelling is first described, followed by different applications covering drug delivery, composite materials using polymer gels to modulate optical or magnetic and electrical properties, molecular imprinting, gel-based biosensors and polymer sensors and actuators used in the field of artificial muscles.

Structure-based design of robust glucose biosensors using a Thermotoga maritima periplasmic glucose-binding protein

We report the design and engineering of a robust, reagentless fluorescent glucose biosensor based on the periplasmic glucose-binding protein obtained from Thermotoga maritima (tmGBP). The gene for this protein was cloned from genomic DNA and overexpressed in Escherichia coli, the identity of its cognate sugar was confirmed, ligand binding was studied, and the structure of its glucose complex was solved to 1.7 Angstrom resolution by X-ray crystallography. TmGBP is specific for glucose and exhibits high thermostability (midpoint of thermal denaturation is 119 +/- 1 degrees C and 144 +/- 2 degrees C in the absence and presence of 1 mM glucose, respectively). A series of fluorescent conjugates was constructed by coupling single, environmentally sensitive fluorophores to unique cysteines introduced by site-specific mutagenesis at positions predicted to be responsive to ligand-induced conformational changes based on the structure. These conjugates were screened to identify engineered tmGBPs that function as reagentless fluorescent glucose biosensors. The Y13C*Cy5 conjugate is bright, gives a large response to glucose over concentration ranges appropriate for in vivo monitoring of blood glucose levels (1-30 mM), and can be immobilized in an orientation-specific manner in microtiter plates to give a reversible response to glucose. The immobilized protein retains its response after long-term storage at room temperature.

Development of fructosyl valine binding polymers by covalent imprinting

Molecularly imprinted polymers (MIPs) against fructosyl valine (Fru-Val), the N-terminal constituent of hemoglobin A1c beta-chains, were prepared by cross-linking of beta-D-Fru-Val-O-bis(4-vinylphenylboronate) with an excess of ethylene glycol dimethacrylate (EDMA) or trimethylolpropane trimethacrylate (TRIM). Control MIPs were prepared in analogy by cross-linking the corresponding vinylphenylboronate esters of fructose and pinacol. After template extraction batch rebinding studies were performed using different pH values and buffer compositions. The Fru-Val imprinted TRIM cross-linked polymer binds about 1.4 times more Fru-Val than the fructose imprinted polymer and 2.7 times more Fru-Val than pinacol imprinted polymer. The highest imprinting effect was obtained in 100 mM sodium carbonate/10% methanol (pH 11.4). The TRIM cross-linked Fru-Val imprinted polymer showed a better specificity than the EDMA cross-linked polymer. The binding of valine was very low. Thermo gravimetric analysis indicated that the generated Fru-Val imprinted polymer has high thermo stability. No change in binding was observed after incubation of the polymers in buffer at 80 degrees C for 36 h. Since the functional group of the polymers (phenyl boronic acid) targets the sugar part of Fru-Val the imprint technique used should also be applicable for the development of MIPs against other glycated amino acids and peptides.

Molecularly imprinted polymers in clinical diagnostics—Future potential and existing problems

The last five years have witnessed a fast progress in the area of molecularly imprinted polymers (MIPs). These have included the development of rational protocols for polymer design (combinatorial and computational), the development of MIPs compatible for use in aqueous environment and the development of various procedures for the integration of MIPs with sensors. The substantial improvements in the performance of imprinted polymers have also been accompanied by a growing number of MIP publications related to solving practical problems associated with their use, e.g. in environmental and clinical analysis. This paper furnishes a detailed analysis of recent achievements in MIPs design and applications related to healthcare, made by our group as well as others worldwide.

Metal ion-imprinted polymers—Novel materials for selective recognition of inorganics

Ion-imprinted polymers (IIPs) are recently identified nano-porous polymeric materials which on leaching the imprint ion can rebind, sense or transport (when cast as membranes) selectively the target analyte in presence of closely related inorganic ions. The IIPs find interesting applications in solid phase extraction, sensors and membrane separations of inorganics. Unlike the molecularly imprinted polymers, the IIP field is in its infancy and has been briefly reviewed here along with some rough guidelines and concepts for further development of IIPs.

Electrochemistry of Conductive Polymers 38. Electrodeposited Poly(3,4-ethylenedioxy-thiophene) Studied by Current Sensing Atomic Force Microscopy

Electrical and morphological properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films electrodeposited on gold-on-silicon electrodes by galvanostatic, potentiostatic, and potentiodynamic methods have been determined using current sensing atomic force microscopic experiments. Surface morphologies and vertical conductivities of PEDOT films were affected by the experimental parameters including the preparation method, the current density, the potential, and the potentiodynamic cyclic number. Band gaps obtained from current-voltage curves of dedoped PEDOT were in excellent agreement with those obtained from absorption spectra. When the film thickness was increased on the gold-on-silicon electrode, the topographic images were not very well defined due to the high roughness but conductivities increased significantly in all the galvanostatically, potetiostatically, and potentiodynamically grown PEDOT films.

Non-covalent molecular imprinting with emphasis on its application in separation and drug development

The molecular imprinting technique can be defined as the formation of specific nano-sized cavities by means of template-directed synthesis. The resulting molecularly imprinted polymers (MIPs), which often have an affinity and a selectivity approaching those of antibody-antigen systems, have thus been coined "artificial antibodies." MIPs are characterized by their high specificity, ease of preparation, and their thermal and chemical stability. They have been widely studied in connection with many potential applications, including their use for separation and isolation purposes, as antibody mimics (biomimetic assays and sensors), as enzyme mimics, in organic synthesis, and in drug delivery. The non-covalent imprinting approach, developed mainly in Lund, has proven to be more versatile than the alternative covalent approach because of its preparation being less complicated and of the broad selection of functional monomers and possible target molecules that are available. The paper presents a review of studies of this versatile technique in the areas of separation and drug development, with emphasis being placed on work carried out in our laboratory.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.

Molecularly imprinted materials as advanced excipients for drug delivery systems

The application of the molecular imprinting technology in the design of new drug delivery systems (DDS) and devices useful in closely related fields, such as diagnostic sensors or biological traps, is receiving increasing attention. Molecular imprinting technology can provide polymeric materials with the ability to recognize specific bioactive molecules and with a sorption/release behaviour that can be made sensitive to the properties of the surrounding medium. In this review, an introduction to the imprinting technology presenting the different approaches in preparing selective polymers of different formats is given, and the key factors involved in obtaining of imprinted binding sites in materials useful for pharmaceutical applications are analysed. Examples of DDS based on molecularly imprinted polymers (MIPs) can be found for the three main approaches developed to control the moment at which delivery should begin and/or the drug release rate; i.e., rate-programmed, activation-modulated or feedback-regulated drug delivery. This review seeks to highlight the most remarkable advantages of the imprinting technique in the development of new efficient DDS as well as to point out some possibilities of adapting the synthesis procedures to create systems compatible with both the relative instable drug molecules, especially of peptide nature, and the sensitive physiological tissues with which MIP-based DDS would enter into contact when administered. The prospects for future development are also analysed.

Molecularly imprinted polymers for drug delivery

Molecular imprinting technology has an enormous potential for creating satisfactory drug dosage forms. Although its application in this field is just at an incipient stage, the use of MIPs in the design of new drug delivery systems (DDS) and devices useful in closely related fields, such as diagnostic sensors, is receiving increasing attention. Examples of MIP-based DDS can be found for the three main approaches developed to control the moment at which delivery should begin and/or the drug release rate, i.e. rate-programmed, activation-modulated, or feedback-regulated drug delivery. The utility of these systems for administering drugs by different routes (e.g. oral, ocular or transdermal) or trapping undesired substances under in vivo conditions is discussed. This review seeks to highlight the more remarkable advantages of the imprinting technique in the development of new efficient DDS as well as pointing out some possibilities to adapt the synthesis procedures to create systems compatible with both the relative instable drug molecules, especially of peptide nature, and the sensitive physiological tissues with which MIP-based DDS would enter into contact when administered. The prospects for future development are also analysed.

Molecular imprinting: a dynamic technique for diverse applications in analytical chemistry

Continuous advances in analyzing complex matrices, improving reliability and simplicity, and performing multiple simultaneous assays with extreme sensitivity are increasing. Several techniques have been developed for the quantitative assays of analytes at low concentrations (e.g., high-pressure liquid chromatography, gas chromatography, immunoassay and the polymerase chain reaction technique). To achieve highly specific and sensitive analysis, high affinity, stable, and specific recognition agents are needed. Although biological recognition agents are very specific and sensitive they are labile and/or have a low density of binding sites. During the past decade molecular imprinting has emerged as an attractive and highly accepted tool for the development of artificial recognition agents. Molecular imprinting is achieved by the interaction, either noncovalent or covalent, between complementary groups in a template molecule and functional monomer units through polymerization or polycondensation. These molecularly imprinted polymers have been widely employed for diverse applications (e.g., in chromatographic separation, drug screening, chemosensors, catalysis, immunoassays etc.) owing to their specificity towards the target molecules and high stability against physicochemical perturbations. In this review the advantages, applications, and recent developments in molecular imprinting technology are highlighted.

Designing selective sites in templated polymers utilizing coordinative bonds

This review gives a survey over recent achievements on the design of selective sites in templated polymers. Particularly, coordinative bonds as driving force for the interaction between a substrate and a templated polymer are discussed. Recent achievements on the selective recognition of larger molecules, such as dipeptides and disaccharides, are highlighted that promise a fast development on biomolecule templated material towards enzyme-like catalysis in the up-coming years. Additionally, the achievements on the incorporation of catalytic centers based on transition metal complexes are summarized.

The artificial pancreas

In type 1 diabetes an absolute deficiency of insulin secretion requires exogenous insulin supply to guarantee the patient's life avoiding ketoacidotic coma and to prevent the chronic complications of diabetes. In order to obtain a more physiological replacement therapy different approaches have been pursued since the early 70s to create an artificial wearable pancreas able to deliver insulin according to the blood glucose values as determined by continuous monitoring. Four components are considered essential for the realisation of an artificial pancreas: the sampling system, the glucose sensor, the mathematical models and the related algorithms for the calculation of the insulin doses and the infusion system for the insulin delivery. At present the still unsolved issues are mainly represented by the availability of reliable continuous glucose monitor and control algorithms, while the new technologies allow for the miniaturisation of the system.

Molecularly imprinted materials--receptors more durable than nature can provide

The chapter describes the concept of molecular imprinting. This technology allows the fabrication of artificial polymeric receptors applicable in many areas of biotechnology. Polymers imprinted with selected template molecules can be used as specific recognition elements in sensors or as selective stationary phases in affinity chromatography or in capillary electrochromatography. However, also in solid phase extraction or immunoassays these polymers (MIP) are able to compete with traditional materials such as biological antibodies. Furthermore, polymers molecularly imprinted with so-called transition state analogue templates can be applied as catalysts. In other words, these kind of polymers may be used as artificial antibodies (plastibodies) or biomimicking enzymes (plastizymes). Compared to their biological counterparts, MIP offer different advantages such as simplicity in manufacturing and durability. Thus, the author expects MIP to have a major impact on the whole area of biotechnology.

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

Background: Multiple laboratory tests are used in the diagnosis and management of patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

Approach: An expert committee drafted evidence-based recommendations for the use of laboratory analysis in patients with diabetes. An external panel of experts reviewed a draft of the guidelines, which were modified in response to the reviewers’ suggestions. A revised draft was posted on the Internet and was presented at the AACC Annual Meeting in July, 2000. The recommendations were modified again in response to oral and written comments. The guidelines were reviewed by the Professional Practice Committee of the American Diabetes Association.

Content: Measurement of plasma glucose remains the sole diagnostic criterion for diabetes. Monitoring of glycemic control is performed by the patients, who measure their own plasma or blood glucose with meters, and by laboratory analysis of glycated hemoglobin. The potential roles of noninvasive glucose monitoring, genetic testing, autoantibodies, microalbumin, proinsulin, C-peptide, and other analytes are addressed.

Summary: The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are of minimal clinical value at the present time, and measurement of them is not recommended.

Molecularly imprinted polymer hydrogels displaying isomerically resolved glucose binding

Non-covalent molecular imprinting of poly(allylamine hydrochloride) (PAA HCl) with glucose phosphate mono-sodium salt produced molecularly imprinted polymer (MIP) hydrogels capable of quantitative, isomerically specific binding of glucose. By ionic association of a template molecule, glucose phosphate mono-sodium salt, to the polymer prior to covalent crosslinking, MIP hydrogels were created with an affinity for binding glucose. In this study we have synthesized MIPs using epichlorohydrin, ethylene glucol diglycidyl ether, and glycerol diglycidyl ether as crosslinkers in order to evaluate their effectiveness with respect to molecular imprinting for glucose. MIP hydrogels were also synthesized with the different crosslinkers and varying amounts of the template molecule in an attempt to elucidate the impact of imprint quantities on the effectiveness of the imprinting technique. Batch equilibration studies, using each of the MIPs and similar non-molecularly imprinted polymers were performed to determine their binding capacities with respect to glucose and fructose. The binding capacity data are discussed and employed in the evaluation of the specificity imparted by the imprinting procedure. MIP hydrogels with binding capacities in excess of 0.5 g of glucose per gram of dried gel were synthesized. Isomeric specificity in hydrogels imprinted for glucose was demonstrated by higher binding capacities of glucose than those of fructose in the same polymers.

Molecular imprinting: at the edge of the third millennium

Molecularly imprinted polymers (MIPs) represent a new class of materials that have artificially created receptor structures (1-3). Since their discovery in 1972, MIPs have attracted considerable interest from scientists and engineers involved with the development of chromatographic adsorbents, membranes, sensors and enzyme and receptor mimics.