molecularly imprinted polymers
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MOLECULARLY IMPRINTED POLYMERSREVIEW SEMINAR ‘13
REVIEW SEMINAR
ON
MOLECULARLY IMPRINTED POLYMERS
SUBMITTED BY
LASHMI VARIAR C.V
M.TECH 1ST SEMESTER
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1. HISTORY
In 1931 Polyakov and co workers, from Kiev, reported some unusual adsorption
properties in silica particles prepared using a novel synthesis procedure.1 Sodium silicate
had been polymerized in water using (NH4)2CO3 as the gelating agent. After two weeks,
additives (benzene, toluene or xylene) had been added. The silica was subsequently
allowed to dry for 20–30 days, after which the additive was removed by extensive washing
in hot water. Subsequent adsorption studies revealed a higher capacity for uptake of the
additive by the silica than for structurally related ligands, i.e. some kind of memory for the
additive was apparent, at least in the cases of benzene and toluene
Linus Pauling,2 in 1940 proposed that antibody formation took place in the
presence of an antigen, captured by the cell, which served as a template for antibody
formation. Pauling suggested that the primary structure of any antibody was identical and
that the template-induced conformational effect gave rise to the remarkable selectivities
exhibited by antibodies. In addition, he proposed that this ability could be investigated by precipitating globulins under denaturing conditions in the presence of an ‘antigen’ and by
slow removal and redissolution of the globulins. The globulins would then exhibit
specificity for the antigen.
A similar methodology to that of Polyakov, was carried out by Dickey3 in 1949 in
his laboratory ,but in this case methyl orange (and other alkyl orange dyes) was used as the
template. The results of Dickey were striking demonstrating pronounced selectivity for the
‘pattern’ dye which had been present during polymerization as related to the other dyes
After two decades of rather intense research in the area, a decline of molecular
imprinting in silica appears to have coincided with the introduction of molecular imprinting
in organic polymers, made independently by Wulff and Klotzin 19724-5,
Owens et al6 in 1999 reviewed the potential of MIP-based analytical techniques in
bio- and pharmaceutical analysis They mentioned that earlier work of MIP-based chiral
stationary phases (CSPs) was almost exclusively carried out with LC and that the number
of MIP applications for CE and CEC was relatively small despite their usefulness. Ansell 7
in 2005 reviewed the literature on chiral separation of drug enantiomers using MIPs via
HPLC, TLC,csupercritical fluid chromatography (SFC), and CEC.
. Wei and Mizaikoff 8 in 2007 gave a review on recent advances of noncovalent MIPs
for affinity separations. They reviewed MIP applications in affinity separations as well as
bio-mimetic assays emphasizing the preparation of shape- and size-uniform particles
Vasapollo et al.9 in 2011 presented a very comprehensive review on present and
future prospective of MIPs aiming to summarize the molecularly imprinting processes and
principal application fields of MIPs, focusing on separation science (mostly HPLC),
chemical sensing, drug delivery, and catalysis.
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2.INTRODUCTION
In molecular imprinting, the target molecule (or a derivative
thereof) acts as the template around which interacting and cross-linking
monomers are arranged and co-polymerized to form a cast-like shell
(Figure 1). Initially, the monomers form a complex with the templatethrough covalent or noncovalent interactions. After polymerization, the
template is removed, and binding sites are exposed that are
complementary to the template in size, shape, and position of the
functional groups. In essence, a molecular “memory” is imprinted on the
polymer, which is now capable of selectively rebinding the template.
Thus, molecularly imprinted polymers (MIPs) possess two of the
most important features of biological receptors—the ability to recognize
and bind specific target molecules. However, MIPs differ from biological
receptors in that they are large, rigid, and insoluble, whereas theirnatural counterparts are smaller, flexible, and, in most instances,
soluble. Depending on their size, MIPs can have thousands or millions of
binding sites, whereas biological receptors have a few or even just one.
Moreover, the population of binding sites in MIPs, especially those
imprinted using noncovalent manner monomer–template interactions, is
heterogeneous because of the influence of the equilibria that govern the
monomer–template complex formation and the dynamic of the growing
polymer chains prior to copolymerization. In addition, the chaotic
structure of many of the polymers used for imprinting, the
heterogeneous pore size distribution, and the fact that the binding sites
are contained within the bulk material often make mass transfer slow.
Although not always problematic, these characteristics can prevent MIPs
from being substituted for natural receptors in certain applications, and
part of the current MIP research is focused on finding solutions or
workarounds to these shortcomings.
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FIGURE 1. Creating a molecular imprint in a synthetic polymer.(a) Functional monomers, (b) a cross-linker, and (c) a template molecule are mixed
together.
(1) The functional monomers form a complex with the template molecule.
(2) The functional monomers copolymerize with the cross-linker.
(3) As polymerization proceeds, an insoluble, highly cross-linked polymeric network isformed around the template.
(4) Removing the template liberates complementary binding sites that can
reaccommodate the template in a highly selective
3. APPROACHES IN MOLECULAR IMPRINTING
.
Figure :2 Schematic representation of covalent and non-covalent molecular imprinting
procedures
MIPs can be synthesised following three different imprinting approaches [1], as follows:
1. The non-covalent procedure is the most widely used because it is relatively simple
experimentally and the complexation step during the synthesis is achieved by mixing the
template with an appropriate functional monomer, or monomers, in a suitable porogen
(solvent). After synthesis, the template is removed from the resultant polymer simply by
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washing it with a solvent or a mixture of solvents. Then the step rebinding the template to
the MIP exploits non-covalent interactions.
2. All these features offer several advantages over the covalent protocol, in which
formation of covalent bonds between the template and the functional monomer is necessary
prior to polymerisation. Furthermore, to remove the template from the polymer matrix after
synthesis via the covalent protocol, it is necessary to cleave the covalent bonds. To this
end, the polymer is then refluxed in a Solvent extraction or treated with reagents in solution
3. The semi-covalent approach is a hybrid of the two previous methods. Thus, covalent
bonds are established between the template and the functional monomer before
polymerisation, while, once the template has been removed from the polymer matrix, the
subsequent re-binding of the analyte to the MIP exploits non-covalent interactions, as per
the non-covalent imprinting protocol.
4. TEMPLATE REMOVAL
Most of the developments in MIP production during the last decade have come inthe form of new polymerization techniques in an attempt to control the arrangement of
monomers and therefore the polymers structure. However, there have been very few
advances in the efficient removal of the template from the MIP once it has been
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polymerized. Due to this neglect, the process of template removal is now the least cost
efficient and most time consuming process in MIP production. [22] Furthermore, in order of
MIPs to reach their full potential in analytical and biotechnological applications, anefficient removal process must be demonstrated.
There are several different methods of extraction which are currently being used for template removal. These have been grouped into 3 main categories: Solvent extraction,
physically assisted extraction, and subcritical or supercritical solvent extraction.
9.1 Soxhlet Extraction
Solvent Extraction technique consists of placing the MIP particles into a cartridge
inside the extraction chamber, and the extraction solvent in poured into a flask connected to the
extractor chamber. The solvent is then heated and condenses inside the cartridge thereby
contacting the MIP particles and extracting the template. The main advantages to this technique
are the repeated washing of MIP particles with fresh extracting solvent, favors solubilization
because it uses hot solvent, no filtration is required upon completion to collect the MIP particles,
the equipment is affordable, and it is very versatile and can be applied to nearly any polymer
matrix. The main disadvantages are the long extraction time, the large amount of organic solvent
used, the possibility or degradation for temperature sensitive polymers, the static nature of the
technique does not facilitate solvent flow through MIP, and the automation is difficult
Incubation This involves the immersion of the MIPs into solvents that can induce swelling
of the polymer network and simultaneously favor the dissociation of the template from the
polymer. Generally this method is carried out under mild conditions and the stability of the
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polymer is not affected. However, much like the Solvant extraction technique, this method also
is very time consuming.
9.2 Physically-Assisted Extraction
Ultrasound-assisted extraction (UAE) This method uses Ultrasound which is a cyclic soundpressure with a frequency greater than 20 kHz. This method works through the process known as
cavitation which forms small bubbles in liquids and the mechanical erosion of solid particles. This
causes a local increase in temperature and pressure which favor solubility, diffusivity, penetration
and transport of solvent and template molecules.
Microwave-Assisted Extraction (MAE) This method uses microwaves which directly interact with
the molecules causing Ionic conduction and dipole rotation. The use of microwaves for extraction
make the extraction of the template occur rapidly, however, one must be careful to avoid
excessively high temperatures if the polymers are heat sensitive. This has the best results when the
technique is used in concert with strong organic acids, however, this poses another problem
because it may cause partial MIP degradation as well. This method does have some benefits in that
it significantly reduces the time required to extract the template, decreases the solvent costs, and is
considered to be a clean technique.
9.3 Subcritical or Supercritical Solvent Extraction
This method employs the use of water, which is the cheapest and greenest solvent, under high
temperatures (100–374 C) and pressures ( 10–60 bar). This method is based upon the high
reduction in polarity that liquid water undergoes when heated to high temperatures. This allows
water to solubilize a wide variety of polar, ionic and non-polar compounds. The decreased surfacetension and viscosity under these conditions also favor diffusivity. Furthermore, the high thermal
energy helps break intermolecular forces such as dipole-dipole interactions, vander Waals forces,
and hydrogen bonding between the template and the matrix.
5.OPTIMIZATION OF MIPs SYNTHESIS
There are several variables, such as kind and amount of monomer or nature of
cross-linker and solvent that affect the final characteristics of the obtained materials in
terms of capacity, affinity and selectivity for the target analytes. Thus, the obtainment of
the optimum MIP to be used in several applications might take several weeks of trial-and-
error experiments using different formulations. This fact has provoked an overuse of
certain standard formulations (i.e. the typical 1:4:20 template:monomer:cross-linker molar
ratio) [14]. Therefore, some attempts dealing with the optimisation of MIP formulations in
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a simple, fast and rational way for the obtainment of MIPs with improved molecular
recognition capabilities have been proposed.
1. Combinatorial imprinting
As mentioned above, due to the variety of parameters influencing the molecular recognition
properties of MIPs, the combinatorial approach can be an ideal tool for making easier and
faster the screening and optimisation of MIP formulations. This strategy was proposed
independently by the groups of Sellergren and co-worker [20] and Takeuchi et al. [21] and
consisted of the preparation of a quite large number of polymers directly in HPLC vials as
small monoliths (mini-MIPs). Then, the obtained mini-MIPs were screened in rebinding
experiments by measuring the template release after incubation in the presence of a suitable
solvent. This methodology has been successfully employed in the rapid evaluation and
selection of the best MIP for different analytes (triazines [20,21] and sulphonylurea
herbicides [22]). The selection of the optimum formulation can be eased by the use of
experimental design and multivariate analysis methods since such methods allow
identifying the main factors affecting the properties of MIPs [23,24]. However, in spite of the mentioned advantages, one of the main drawbacks is the limited range of
methodologies for the screening of mini-MIPs, being restricted to rebinding experiments in
equilibrium. In addition, the extrapolation of the obtained results has to be made with
caution since the fate of a mini-MIP (monolith) might differ from that obtained after
crushing and sieving the polymer.
2. Computational approach
This approach uses molecular modelling software to design and screen a virtual
library of monomers against the desired template. Through this approach it is possible to
calculate binding energies and predict template–monomer interaction positions, making
easier to select the best functional monomer to be used [15–18]. Following this
methodology, polymers with high binding capacity and selectivity have been obtained for
different analytes. In this sense, it is remarkable the results presented recently by Chianella
et al. [19] where the use of a computational protocol allowed the preparation of a MIP for
the drug abacavir with a surprisingly high binding capacity of up to 157 mg of drug per
gram of polymer. It is necessary to point out that this approach is relatively new and thus,
before being routinely used, it is still necessary to prepare and evaluate the best polymers
(also for the worst ones it would be desirable) to confirm the trueness of the computational
prediction.
5 EFFECTING OF SPECIAL MOLECULAR
RECOGNITION
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1 Optimization of the Polymer Structure
The synthesis of molecularly imprinted polymers is a chemically
complex pursuit and demands a good understanding of chemical equilibrium, molecular
recognition theory, thermodynamics and polymer chemistry in order to ensure a high levelof molecular recognition . The polymers should be rather rigid to preserve the structure of
the cavity after splitting off the template. On the other hand, a high flexibility of the
polymers should be present to facilitate a fast equilibrium between release and reuptake of
the template in the cavity. These two properties are contradictory to each other, and a
careful optimization became necessary.
2 Template
. Optically active templates have been used in most cases during optimization. In these
cases the accuracy of the structure of the imprint (the cavity with binding sites) could be
measured by its ability for racemic resolution, which was tested either in a batch procedure
or by using the polymeric materials as chromatographic supports. One of the many
attractive features of the molecular imprinting method is that it can be applied to a diverse
range of analytes, however, not all templates are directly amenable to molecular imprinting
processes..
3 Monomers
The careful choice of functional monomer is one of the utmost importance to provide
complementary interactions with the template and substrates. For covalent molecular imprinting, the effects of changing the template to functional monomer ratio is not
necessary because the template dictates the number of functional monomers that can be
covalently attached; furthermore, the functional monomers are attached in a stoichiometric
manner. For non-covalent imprinting, the optimal template /monomer ratio is achieved
empirically by evaluating several polymers made with different formulations with
increasing template.. It is very important to match the functionality of the template with the
functionality of the functional monomer in a complementary fashion (e.g. H-bond donor
with H-bond acceptor) in order to maximise complex formation and thus the imprinting
effect.
4 Crosslinkers
The selectivity is greatly influenced by the kind and amount of cross-
linking agent used in the synthesis of the imprinted polymer. The careful choice of
functional monomer is another importance choice to provide complementary interactions
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with the template and substrates (Figure 5). In an imprinted polymer, the cross-linker fulfils
three major functions: First of all, the cross-linker is important in controlling the
morphology of the polymer matrix, whether it is gel-type, macroporous or a microgel
powder. Secondly, it serves to stabilize the imprinted binding site. Finally, it imparts
mechanical stability to the polymer matrix
5 Porogenic solvents
Porogenic solvents play an important role in formation of the porous structure of
MIP, which known as macroporous polymers. It is known that the nature and level of
porogenic solvents determines the strength of non-covalent interactions and influences
polymer morphology which, obviously, directly affects the performance of MIP.
Firstly, template molecule, initiator, monomer and cross-linker have to be soluble
in the porogenic solvents.
Secondly, the porogenic solvents should produce large pores, in order to assure
good flow-through properties of the resulting polymer.
Thirdly, the porogenic solvents should be relatively low polarity, in order to reduce
the interferences during complex formation between the imprint molecule and the
monomer, as the latter is very important to obtain high selectivity MIP.
6 Initiators
Many chemical initiators with different chemical properties can be used as the radical
source in free radical polymerization Normally they are used at low levels compared to the
monomer, e.g. 1 wt. %, or 1 mol. % with respect to the total number of moles of
polymerisable double bonds. The rate and mode of decomposition of an initiator to radicals
can be triggered and controlled in a number of ways, including heat, light and by
chemical/electrochemical means, depending upon its chemical nature. For example, the
azoinitiator azobisisobutyronitrile (AIBN) can be conveniently decomposed by photolysis
(UV) or thermolysis to give stabilised, carbon-centred radicals capable of initiating the
growth of a number of vinyl monomers.
7 Polymerization condition
Several studies have shown that polymerization of MIP at lower temperatures forms
polymers with greater selectivity versus polymers made at elevated temperatures. Usually,
most people using 60℃ as the polymerization temperature. However, the initiation of the
polymerization reaction was very fast and therefore hard to control at this temperature and
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resulted in low reproducibility of molecular imprinted polymer. Furthermore, the relatively
high temperatures have a negative impact on the complex stability, which reduced the
reproducibility of the monolithic stationary phases and produced high column pressure
drops. Thus, the relatively low temperatures of with a prolonged reaction time were
selected in order to yield a more reproducible polymerization.
8 PREPERATION METHODS OF MIP
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Figure 3. Polymerization approaches forMIP-based HPLC stationary phases: (A) bulk polymerization, (B) in
situ polymerization, (C) one-step suspension or precipitation polymerization, (D) MIP composite beads.
Figure 4. Synthetic schemes for MIP compositebeads. (A) Shell-imprinted core–shellbeads, (B) MIP-silica composite beads madefrom iniferter-modified support, (C) multistepswelling polymerization for the production of MIP beads. Reprinted with permission from
reference [5].
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Fig. 2. Scanning electron micrographs of spherical MIP particles prepared by: (A) suspension polymerization(×500 magnification), from Ref. [25]; (B) multistepswelling polymerization (×2000 magnification), from Ref. [27]; (C) precipitation polymerization (the scale is 2μm), from Ref. [31]; (D) precipitation polymerization
(the bar is 22 μm), from Ref. [33].
6 New strategies in the synthesis of MIPs
6.1. Microwave-assisted synthesis.
A microwave-heating technique for preparing magnetically- imprinted polymer
beads was first proposed by Li and co-workers [7]. The preparation was performed by
dispersing the polymerization solution, which comprised the self-assembled mixture of
template, functional monomer, copolymer monomer, cross-liner and initiator. Then,
polymerization was initiated by microwave heating. The reaction time was dramatically
shortened compared to conventional heating. In addition, the resultant polymer beads
exhibited good characteristics (e.g., narrow size distribution, uniform morphology, and
superior selectivity) and showed rather higher imprinting efficiency. We conclude that
microwave heating is a powerful technique to prepare magnetic MIP beads in this simple,
efficient manner. So far, the microwave-assisted synthetic method has been applied to bulk
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polymerization, precipitation polymerization, surface-graft polymerization and sol-gel
synthesis, and shortened the polymerization time significantly. It has great potential to be
used for the efficient preparation of MIPs of different forms.
6.2. Reversible addition-fragmentation chain-transfer (RAFT)
polymerization.
So far, free-radical polymerization is the major technique employed in preparing
MIPs. However, the MIPs obtained generally have heterogeneous structures because of the
uncontrollable chaintransfer and termination reactions. Controlled or living free-radical
polymerization methods have great potential to overcomthese intrinsic limitations. Due to
its versatility and simplicity, RAFT is an ideal candidate for the controlled or living free-
radical polymerization method, where almost all the conventional radical-polymerization
monomers can be employed. Recently, MIPs with different formats have been successfully
synthesized via RAFT polymerization. Most research focuses on preparing surface-imprinted polymer. Control of the grafting can be achieved using immobilized azo-
initiators [8], iniferters or RAFT agents [9] on the surface of supports. The immobilization
of RAFT agent is the commonly used method. MIPs could also be directly grafted onto
silica NPs modified with vinyl groups by RAFT polymerization [10]. With the RAFT
process, thin imprinted films have been successfully coated on a variety of supports (e.g.,
silica gel, silica NPs, Fe3O4 microspheres, graphene oxide and polystyrene).
RAFT-precipitation polymerization (RAFTPP) was first proposed to prepare
regular MIP beads by Zhang and coworkers [11]. The presence of surface-immobilized
reactive functional groups on the microspheres obtained allows their further surface
modification. Functional polymer brushes or hydrogel layers could be used to modify these
MIPs via RAFT polymerization to prepare water-compatible MIPs.
Recently, a novel efficient one-pot approach obtained pure-water-compatible and
narrowly dispersed MIPs with surface-grafted hydrophilic polymer brushes by RAFTPP
[12]. Other formats (e.g., powders and soluble MIPs) have been reported. In general,
uniform imprinted shells with adjustable thickness, higher selectivity, improved mass-
transfer properties, much higher binding capacity and better column efficiency were
observed with RAFT polymerization compared with conventional polymerization.
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10 CONCLUSION AND FUTURE OUTLOOK
9 REFERENCE JOURNALS
1. Polyakov MV. 1931. Adsorption properties and structure of silica gel. Zhur. Fiz. Khim.
2: 799–805.
2. Pauling L. 1940. A theory of the structure and process of formation of antibodies. J. Am.
Chem. Soc. 62: 2643– 2657.
3 .Dickey FH. 1949. The preparation of specific adsorbents. Proc. Natl. Acad. Sci. USA 35:
227–229.
4. Wulff G, Sarhan A. 1972. The use of polymers with enzyme-analogous structures for
the resolution of racemates. Angew. Chem., Intl. Ed. Engl. 11: 341. DOI:
10.1002/anie.197203341
5. Takagishi T, Klotz IM. 1972. Macromolecule-small molecule interactions; introduction
of additional binding sites in polyethyleneimine by disulfide cross-linkages.
Biopolymers 11: 483–491. DOI: 10.1002/bip.1972. 360110213
6 Owens, P. K., Karlsson, L., Lutz, E. S. M., Andersson, L. I., Trends Anal. Chem. 1999,
18, 146–154.
7 Ansell, D. J., Adv. Drug Delivery Rev. 2005, 57 , 1809–1835.
8 Wei, S., Mizaikoff, B., J. Sep. Sci. 2007, 30, 1794–1805.
9 Vasapollo, G., Sole, R. D., Mergola, L., Lazzoi, M. R.,Scardino, A., Scorrano, S.,Mele, G., Int. J. Mol. Sci. 2011, 12, 5908–5945.
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