imprinted polymer
TRANSCRIPT
Molecular Imprinting PolymersMolecular Imprinting Polymers
MIPsMIPs
IntroductionIntroduction
In chemistry, In chemistry, molecular imprintingmolecular imprinting is a is a technique to create template-shaped technique to create template-shaped cavities in polymer matrices with memory cavities in polymer matrices with memory of the template molecules. of the template molecules.
Schematic of molecular imprintingSchematic of molecular imprinting
Templateassembly
(binding)Template
a
c
b1- add cross-linker2- polymerise(in porogenicsolvent)
Template
re-binding
templateremoval
recognition site
History of Molecular ImprintingHistory of Molecular Imprinting Molecular imprinting was used as early as the 1930's by Molecular imprinting was used as early as the 1930's by
MV PolyakovMV Polyakov to selectively capture various additives in to selectively capture various additives in a silica matrix.a silica matrix.
In the 1940's In the 1940's Linus PaulingLinus Pauling hypothesized that a process hypothesized that a process similar to molecular imprinting could be responsible for similar to molecular imprinting could be responsible for the selectivity of antibodies to their respective antigens.the selectivity of antibodies to their respective antigens.
Biological systems Biological systems
Molecular recognition plays an important role in Molecular recognition plays an important role in biological systems and is observed in between receptor-biological systems and is observed in between receptor-ligand, antigen-antibody, DNA-protein, sugar-lectin, ligand, antigen-antibody, DNA-protein, sugar-lectin,
RNA-ribosome, etcRNA-ribosome, etc AntigensAntigens
AntigenAntigen
Antigen-binding site
History of Molecular ImprintingHistory of Molecular Imprinting
The concept of molecular imprinting was revived in the The concept of molecular imprinting was revived in the 1970's when Günter Wulff discovered that highly 1970's when Günter Wulff discovered that highly crosslinked organic polymers could also be used to crosslinked organic polymers could also be used to make molecular imprints with high specificity.make molecular imprints with high specificity.
In more recent years, imprinted polymers have been In more recent years, imprinted polymers have been
used to capture everything from steroids to TNT.used to capture everything from steroids to TNT.
Imprinting methodologiesImprinting methodologies
CovalentCovalent Reversible covalent linkageReversible covalent linkage
OH
OH
R1
R2
+ B R3HO
HO O
B
OR1
R2
R3
- 2 H2O
+ 2 H2O
Molecular Imprinting: CovalentMolecular Imprinting: Covalent
O
OO
O
O OH
B
B
O
OO
O
O OH
B
B
OHHO
OH
OH
B
B
O
OO
O
polymerize
- galactose
+ galactose
Wulff & Schauhoff J. Org. Chem., 1991, 56, 395-400.
Imprinting methodologies Imprinting methodologies advantagesadvantages and and disadvantagesdisadvantages
Covalent ImprintingCovalent Imprinting Ability to fix template in place during polymerisation - Ability to fix template in place during polymerisation -
lower dispersity in binding siteslower dispersity in binding sites Can be carried out in any solvent flexibilityCan be carried out in any solvent flexibility Can be difficult to remove template from polymer - Can be difficult to remove template from polymer -
low recovery of valuable templates and low number low recovery of valuable templates and low number of binding sitesof binding sites
Limited number of chemistries for fixing template to Limited number of chemistries for fixing template to polymer reversibly - reduction in number of templates polymer reversibly - reduction in number of templates that can be imprintedthat can be imprinted
Poor kinetics of re-bindingPoor kinetics of re-binding
Imprinting methodologiesImprinting methodologies
Non-covalent
Monomer-template complexes
+R1
O
OHN
R3
R2
R1
O
OH
R2
R3
N
Molecular Imprinting: Non-covalentMolecular Imprinting: Non-covalent
OO
H
O
O
H
CH3
O
OO
O
HN
NH
H3C
HN
H
O
O
O
OH
HO
O
CH3
O
OO
O
HN
NH
H3C
HN
O
OH H
OO
OH
O
H
O
O
O
O
H
EGDMA,polymerize
Non-covalent template-monomer complex Imprint is spatially and functionally complemetary to template
Ramström et.al. Tetrahedron: Asymmetry, 1994, 5, 649-656.
Imprinting methodologies Imprinting methodologies - - advantagesadvantages and and disadvantagesdisadvantages
Non-covalent imprintingNon-covalent imprinting Easy to remove template from polymer- good Easy to remove template from polymer- good
recovery of valuable templates and accessible recovery of valuable templates and accessible binding sitesbinding sites
Very large number of templates amenable to non-Very large number of templates amenable to non-covalent imprintingcovalent imprinting
Rapid kinetics of re-bindingRapid kinetics of re-binding Inability to fix template in place during polymerisation Inability to fix template in place during polymerisation
- polydispersity in binding sites, poor definition- polydispersity in binding sites, poor definition Generally requires low-polarity aprotic solvents - Generally requires low-polarity aprotic solvents -
incompatible with aqueous polymerisationsincompatible with aqueous polymerisations
Imprinting methodologiesImprinting methodologies
Sacrificial spacer (semi-covalent) Covalent link during synthesis
Non-covalent rebinding
R1 R2O
O
OR1
O
O ClR2
OH
+
R1
OH
HO
R2
Molecular Imprinting: Spacer ApproachMolecular Imprinting: Spacer Approach
O
OO O O
O
O
H
OH
O
H
O
OO
O
AIBN, 65oC, 24h
1M NaOH/MeOH reflux
Cholesterolin n-hexane
Whitcombe et al. J. Am. Chem. Soc., 1995, 117, 7105-7111.
CVPC
Imprinting methodologies Imprinting methodologies - advantages and disadvantages- advantages and disadvantages
Sacrificial spacer methodSacrificial spacer method Ability to fix template in place during polymerisation - Ability to fix template in place during polymerisation -
lower dispersity in binding siteslower dispersity in binding sites Can be carried out in any solvent flexibilityCan be carried out in any solvent flexibility Rapid kinetics of re-bindingRapid kinetics of re-binding Can be difficult to remove template from polymer - Can be difficult to remove template from polymer -
low recovery of valuable templates and low number low recovery of valuable templates and low number of binding sitesof binding sites
Limited number of chemistries for fixing template to Limited number of chemistries for fixing template to polymer reversibly - reduction in number of templates polymer reversibly - reduction in number of templates that can be imprintedthat can be imprinted
Target molecules & Imprinting Target molecules & Imprinting matricesmatrices
Target moleculesTarget molecules
Small organic molecules:, pesticides, amino acids, Small organic molecules:, pesticides, amino acids, nucleotide bases, steroids ,sugars ,metal ion peptides, nucleotide bases, steroids ,sugars ,metal ion peptides, proteins and drug,…proteins and drug,…
Imprinting matricesImprinting matrices
Acrylic and vinyl polymersAcrylic and vinyl polymers
Organic polymersOrganic polymers
Other imprinting matricesOther imprinting matrices
Preparation MIPsPreparation 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)
Preparation MIPsPreparation 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.
Molecular imprinting of theophylline immobilized onto a solidsupport: immobilized template with monomers (1), composite material after polymerization (2), imprinted polymer after dissolution of the support.
1 2 31
Preparation MIPsPreparation 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.
Preparation MIPsPreparation 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 water–oil interface.
and…
Applications of imprinted polymers Applications of imprinted polymers
SeparationSeparationChromatographyChromatographyCapillary electro chromatographyCapillary electro chromatographySolid phase extractionSolid phase extraction
Pseudo immunoassays
Synthesis & CatalysisSynthesis & Catalysis
SensorsSensors
Separation: Separation: chromatographychromatography
MIPs as stationary phases:MIPs as stationary phases:
Imprinted enantiomer retained on columnImprinted enantiomer retained on column
Separation:Separation: Solid phase extraction
Pseudo immunoassays
An An immunoassayimmunoassay is a biochemical test that measures is a biochemical test that measures the concentration of a substance in a biological liquid, the concentration of a substance in a biological liquid, typically serum or urine, using the reaction of an typically serum or urine, using the reaction of an antibody or antibodies to its antigen. The assay takes antibody or antibodies to its antigen. The assay takes advantage of the specific binding of an antibody to its advantage of the specific binding of an antibody to its
antigen.antigen.
A promising application area for MIP development is as replacements for biological receptors such as antibodies in analogues of immunoassays.
Imprinted polymers-antibody binding site mimicsImprinted polymers-antibody binding site mimics
N
N N
N
O
H3C
O
CH3
H O
OH+
O
OH
H
CH3
O
H3C
O
N
NN
N
HO
O
HO
O
EGDMApolymerize
O
OH
H
CH3
O
H3C
O
N
NN
N
HO
O
HO
O
O
OH
extract rebind
HO
O
HO
O
HO
O
HO
O
O
OH
N
N N
N
O
H3C
O
CH3
CH3
N
N N
N
O
H3C
O
CH3
CH3
X
Theophylline
Caffeine
Comparison of MIPs and Comparison of MIPs and antibodiesantibodies
In vivo In vivo preparationpreparation
Limited stabilityLimited stability
Limited applicabilityLimited applicability
Higher costsHigher costs
In vitro In vitro preparationpreparation
Unlimited stabilityUnlimited stability
General applicabilityGeneral applicability
Lower costsLower costs
Antibodies MIPs
SensorsSensors
a chemical sensor selectively recognizes a a chemical sensor selectively recognizes a target molecule in a complex matrix and target molecule in a complex matrix and generates an output signal using a transducer generates an output signal using a transducer that correlates to the concentration of the that correlates to the concentration of the analyte .analyte .
Sensor performanceSensor performance selectivity,selectivity, sensitivity, sensitivity, stability,stability,
MIPs have unique properties that MIPs have unique properties that make them especially suitable for make them especially suitable for sensor technology. They exhibit sensor technology. They exhibit good specificity for various good specificity for various compounds of medical, compounds of medical, environmental, and industrial environmental, and industrial interest; and they have excellent interest; and they have excellent operational stability. Their operational stability. Their recognition properties are recognition properties are unaffected by acid, base, heat, or unaffected by acid, base, heat, or organic phase treatment making organic phase treatment making them highly suitable as them highly suitable as recognition elements in chemical recognition elements in chemical sensors.sensors.
MIP Sensors
Sensor typeSensor type
Quartz-crystal microbalance-based sensing devices
Optical sensors
Electrochemical Sensor
and…
Optical sensors : Fluorescent Sensor
F = fluorescent tag
Weakly fluorescent strongly fluorescent
Typical set of fluorescence emission spectra of D-fructoseimprinted polymer at different concentrations of D-fructose (λex=370nm)
REFERENCESREFERENCES
J. Mol. Recognit. 2006; 19: 106–180
Analyst, 2001, 126, 747–756
Analytica Chemica Acta 534(2005) 31-39
Anal Bioanal Chem(2006) 386 1235-1244
