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Imprinted Polymer

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Title: Imprinted Polymer


1
  • Molecular Imprinting Polymers
  • MIPs

2
Introduction
  • In chemistry, molecular imprinting is a technique
    to create template-shaped cavities in polymer
    matrices with memory of the template molecules.

3
Schematic of molecular imprinting
4
History of Molecular Imprinting
  • Molecular imprinting was used as early as the
    1930's by MV Polyakov to selectively capture
    various additives in a silica matrix.
  • In the 1940's Linus Pauling hypothesized that a
    process similar to molecular imprinting could be
    responsible for the selectivity of antibodies to
    their respective antigens.

5
Biological systems
  • Molecular recognition plays an important role in
    biological systems and is observed in between
    receptor-ligand, antigen-antibody, DNA-protein,
    sugar-lectin, RNA-ribosome, etc

Antigens
Antigen-binding site
Antigen
6
History of Molecular Imprinting
  • The concept of molecular imprinting was revived
    in the 1970's when Günter Wulff discovered that
    highly crosslinked organic polymers could also be
    used to make molecular imprints with high
    specificity.
  • In more recent years, imprinted polymers have
    been used to capture everything from steroids to
    TNT.

7
Imprinting methodologies
  • Covalent
  • Reversible covalent linkage

8
Molecular Imprinting Covalent
Wulff Schauhoff J. Org. Chem., 1991, 56,
395-400.
9
Imprinting methodologies advantages and
disadvantages
  • Covalent Imprinting
  • Ability to fix template in place during
    polymerisation - lower dispersity in binding
    sites
  • Can be carried out in any solvent flexibility
  • Can be difficult to remove template from polymer
    - low recovery of valuable templates and low
    number of binding sites
  • Limited number of chemistries for fixing template
    to polymer reversibly - reduction in number of
    templates that can be imprinted
  • Poor kinetics of re-binding 

10
Imprinting methodologies
  • Non-covalent
  • Monomer-template complexes

11
Molecular Imprinting Non-covalent
12
Imprinting methodologies - advantages and
disadvantages
  • Non-covalent imprinting
  • Easy to remove template from polymer- good
    recovery of valuable templates and accessible
    binding sites
  • Very large number of templates amenable to
    non-covalent imprinting
  • Rapid kinetics of re-binding
  • Inability to fix template in place during
    polymerisation - polydispersity in binding sites,
    poor definition
  • Generally requires low-polarity aprotic solvents
    - incompatible with aqueous polymerisations 

13
Imprinting methodologies
  • Sacrificial spacer (semi-covalent)
  • Covalent link during synthesis
  • Non-covalent rebinding

14
Molecular Imprinting Spacer Approach
CVPC
15
Imprinting methodologies - advantages and
disadvantages
  • Sacrificial spacer method
  • Ability to fix template in place during
    polymerisation - lower dispersity in binding
    sites
  • Can be carried out in any solvent flexibility
  • Rapid kinetics of re-binding
  • Can be difficult to remove template from polymer
    - low recovery of valuable templates and low
    number of binding sites
  • Limited number of chemistries for fixing template
    to polymer reversibly - reduction in number of
    templates that can be imprinted

16
Target molecules Imprinting matrices
  • Target molecules
  • Small organic molecules, pesticides, amino
    acids, nucleotide bases, steroids ,sugars ,metal
    ion peptides, proteins and drug,
  • Imprinting matrices
  • Acrylic and vinyl polymers
  • Organic polymers
  • Other imprinting matrices

17
Preparation MIPs
  • Generally MIPs have been prepared as monoliths
    using bulk polymerization of vinylic monomer
    mixtures by free radical initiation
  • Consequently, the material requires grinding
    before use (sieving is often also employed to
    fractionate by particle size)

18
Preparation MIPs
  • In situ polymerization.
  • In order to avoid the grinding and packing of
    HPLC columns the polymer is formed inside a
    column as a porous monolith.
  • Coated silica particles.
  • A polymerizable group was first attached to
    the silica surface and polymerization was then
    carried out using template, cross-linker and
    functional monomer.

19
2
1
3
1
Molecular imprinting of theophylline immobilized
onto a solid support immobilized template with
monomers (1), composite material after
polymerization (2), imprinted polymer after
dissolution of the support.
20
Preparation MIPs
  • Precipitation polymerization.
  • Precipitation polymerization can be performed
    with similar prepolymerization mixtures as for
    bulk polymers, except that the relative amount of
    solvent present in the mixture is much higher.
    When polymerization progresses, imprinted nano-
    or microspheres precipitate instead of
    polymerizing together to form a polymer monolith.

21
Preparation MIPs
  • W/O emulsion polymerization.
  • Binding sites confined at the interior
    surface of voids within an organic polymer can be
    created by polymerization of the continuous (oil)
    phase of a water-in-oil (W/O) emulsion stabilized
    with an amphiphilic functional surfactant
    complexed with the template molecule at the
    wateroil interface.
  • and

22
Applications of imprinted polymers
  • SeparationChromatographyCapillary electro
    chromatographySolid phase extraction
  • Pseudo immunoassays
  • Synthesis Catalysis
  • Sensors

23
Separation chromatography
  • MIPs as stationary phases

Imprinted enantiomer retained on column
24
Separation Solid phase extraction
25
Pseudo immunoassays
  • An immunoassay is a biochemical test that
    measures the concentration of a substance in a
    biological liquid, typically serum or urine,
    using the reaction of an antibody or antibodies
    to its antigen. The assay takes advantage of the
    specific binding of an antibody to its antigen.
  • A promising application area for MIP development
    is as replacements for biological receptors such
    as antibodies in analogues of immunoassays.

26
Imprinted polymers-antibody binding site mimics
27
Comparison of MIPs and antibodies
MIPs
Antibodies
  • In vivo preparation
  • Limited stability
  • Limited applicability
  • Higher costs
  • In vitro preparation
  • Unlimited stability
  • General applicability
  • Lower costs

28
Sensors
  • a chemical sensor selectively recognizes a
    target molecule in a complex matrix and generates
    an output signal using a transducer that
    correlates to the concentration of the analyte .
  • Sensor performance
  • selectivity,
  • sensitivity,
  • stability,

29
MIP Sensors
  • MIPs have unique properties that make them
    especially suitable for sensor technology. They
    exhibit good specificity for various compounds of
    medical, environmental, and industrial interest
    and they have excellent operational stability.
    Their recognition properties are unaffected by
    acid, base, heat, or organic phase treatment
    making them highly suitable as recognition
    elements in chemical sensors.

30
Sensor type
  • Quartz-crystal microbalance-based sensing devices
  • Optical sensors
  • Electrochemical Sensor
  • and

31
Optical sensors Fluorescent Sensor
strongly fluorescent
Weakly fluorescent
F fluorescent tag
32
Typical set of fluorescence emission spectra of
D-fructose imprinted polymer at different
concentrations of D-fructose (?ex370nm)
33
REFERENCES
  • J. Mol. Recognit. 2006 19 106180
  • Analyst, 2001, 126, 747756
  • Analytica Chemica Acta 534(2005) 31-39
  • Anal Bioanal Chem(2006) 386 1235-1244

34
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