GB2418428A - Design and use of imprinted polymers, with specific affinity affecting controlled release of chemicals - Google Patents

Abstract

The presented invention describes an application of rationally designed molecularly imprinted polymers with prearranged affinity and their use for the controlled release of chemicals in situ. The first embodiment of this patent covers the design of these materials to obtain the properties required to allow a steady rate of release into the required medium. The second embodiment covers the use of these polymers as a medium for the release of chemicals into the environment. The third embodiment lists the potential applications of this technology. The preferred chemical to be released is the herbicide simazine and the preferred monomers are methacylic acid, ethylene glycoldimethacrylate and hydroxyethlmethacrylate.

Description

4. Whitcombe, M. J., Martin, L. & Vulfson E. N. (1998). Predicting the

selectivity of unprinted polymers (,hromalo>'raph/a 47 457-464 1 anza, F. & Sellergren, B. (1999). Method for synthesis and screening of large groups of molecularly imprinted polymers. Analytical ('hem/./y 71 2092-2096.

6 Takeuchi 1. Fukuma D. & Matsui J. (1999). Combinatorial molecular imprmtmg an approach to synthetic polymer receptors Analytical ( hem/. siry 71 285-290 7. Piletsky, S. A. Karim, K. Piletska E. V. Day C.J., lireebairn' K. W. Legge, C. H. & Turner, A. P. [. (20()1). Recognition of ephedrine enantiomers by MIPs designed USmg a computational approach. Analyst 126 1826-1830.

8 Chianella l. l otierzo M., Piletsky S. A. Iothill l. E. Chen B., Karim K. & Turner A. P. F. (2002). Rational design of a polymer specific for microcystin- I R using computational approach. Analytical (.,hem/Asiry 74, 1288- 1293.

Background of the Invention

Molecular modelling and computational design methods in general have been used previously for the design of polymers with predetermined alfmity (PCT/GBOI/00324 UK 0400306.7). this method involved screening of a virtual library of molecular models of functional monomers (those containing polymerizable residues and residues able to form electrostatic interactions) on their ability to interact with molecular model of the target compound (template). For each monomer a binding score is calculated and these along with monomer postonmg are used to select the monomers for polymer synthesis 1 he presence of the template in solution helped to co-ordinate mutual positioning of the selected monomers m the synthesized polymer leading to the fonnation of selective binding sites The previous art teaches use of computationally designed polymers (both synthessed m the presence or in the absence of the template) in separation purification removal, analysis, sensing, as protective and antiadhesive coatings and in choral separation The present invention describes computational and combinatorial design of polymers with prearranged affinity for the programmable release of entrapped or adsorbed chemicals into the environment Controlled release frown the polymeric materials has been described previously with application of latex dispersion (US5,260,259), layered hydrogels, (US4,814,182) or starch integration with the required chemical (US4,738,724). Further to this controlled release of chemicals Is achieved by encapsulation methods which provide a shield which gradually degrades over time allowing for release (F.PI,166,866).

Tl1e controlled release has been achieved in most cases through on of three mechanisms or their combination. In one such process the release is based on slow leaching of the adsorbed or entrapped compound from the polymer In another approach controlled release is achieved through the slow dil'fusion of the chemical t:hrougl1 the membrane of capsule or container. Yet In another approach the controlled release Is achieved through the hydrolysis of chemicals covalently attached to the matrix polymer.

All these approaches have they own advantages and disadvantages. The serious problem is difficulty in tailoring the profile or- kinetics of chemicals release. Tlls is the reason for continuing search for the tecilnology which provides et'fectve and broad control over the release and whicl1 would be generic, simple, inexpensive and reliable.

The present invention offers a possible solution for existing problems.

Summary of the Invention

In the previous patent (PCT/GBO]/00324) we described the rational design technique for the rapid development and optimization of polymer cornpositron. For most systems using these polymers (e g. sensors, separation) it is important to obtain high affinity, and hence specificity for the template A. However, it is known that the affinity of any polymer relates to its components parts, namely the functional monomers which interact with the target template t-7 An added bonus of this computa.tonal design method Is that the Interactions between the monomers and template can be measured, in teens of their budding score. This allows us to predict the affinity (and specificity) of a polymer from its composition We have shown float the predicted scores obtained by the modelling relates directly to their affinity to a.template molecule (PCT/GBOI/00324) 7'8 The combinatorial approach, as described by Lanzas and 'I'akeuchi6 is an alternative approach whrcl1 allows for testing of polymers affinity by altering', certain characteristics of the polymer make up in batch testing, leading to identification of the properties of each polymer made Through these two methods, separately or in combination, it is possible to design a composition leading to an ntnnsically inert polymer with programmable affinity and with ability to release adsorbed or entrapped chemical with profile specific for a par-ticuIar need.

In the core of the Invention hes hypothesis that the release of any chemical adsorbed by the polymer would be adversely proportional to the affinity of this chemical to the polymer. Thus by rational selection of the polymer composition it would be possible to tailor release of adsorbed chemical in a pattern desirable for a specific application. To achieve it we have developed a computational screening approach which helps to identify monomers with varying affinity towards target compound (PC'I'/GBOI/00324). The screening process pennits to rank functional monomers accordingly to their binding score to the target chemical compound From this list it world be possible to select these monomers which have higher or lower affimty depending on required release profile.

Thus if it is required to provide slow release of low concentration of' adsorbed chemical then these monomers would be selected which have highest affimty towards the target compound. If it is required to provide fast release of large quantity of adsorbed chemical then these monomers would be selected which have low affinity. It is possible also to use mixture of two or more polymers with different affinity if the required release has more complex profile.

Therefore the embodiments of this patent lie with the design of the polymer and their uses The first embodiment of the present invention describes ranking of the monomers on the basis of their binding score to the target compound determined by computational screening. Using a computational method as desert teed in patent PCT/GBOI/00324 a virtual hbrary oi'fuctional monomers is designed and screened against a target template.

Functional monomers should possess polymerizable residues and residues able to interact with the template through electrostatic hydrophobic vander-Waals forces dipole-dipole interactions or reversible covalent bonds. Tile library of functional monomers Precludes monomers that can be vmyl monomers allyl monomers acetylenes acrylates methacrylates amino acids nucleosides nucleotides carbohydrates phenols heterocycles amlne end theirdervatves.

I his screening allows calculating the interactions between the target template and monomers and ranking them In order of strength and position of interaction These calculations allow the composition of a polymer to be produced which will have a specific (varying) affinity and specificity for the template.

The second embodiment of the present Invention describes an application of cormbmatorial methods for the selection of monomer(s) for polymer composition suitable for programmable release of the adsorbed (entrapped) chemical compound. The process involves design of the library of polymers containing monomer or monomer residue co- polynersed or covalently attached to the matrix. This library then screened against of target compound using bndmg assay chromatography or sensor chip m order to establish binding (affinity) ranking for each of these monomers T he thud embodiment of the present invention describes selection of the monomers and synthesis of the polymers for controlled release of the chemicals. The selection process Involves an identification of the monomers from the screening list which In theory from previous experience or- on the basis of testing have expected release properties. In some applications it would be required to provide rnnmal testing of the release profiles of some of the polymers contamng the monomers from the screening list. Thus if it appears that the synthessed polymers have too high affinity for the target then it would Justify the selection of the monomers from the hst with lower bmdTng score for the preparation of polymer Specific release profile might also require combination of different polymers with different affimtes (e g one releasing a smaller amount faster tharI a second one releasing a larger amount slower).

The fourth embodiment of the present nventror, describes synthesis of polymers. The polymers can be synthesised by free radical polyTnensation, I1VIng POIYmerISatIOn' TOnIC polymerTsatTon or polycondensatioT, Polymers can be also prepared in a form suitable for future applications - coatings pa.rtTcles membranes or bulk material. Selected monomers can be grafted to the matrix surface or mTlToblised on its surface. The physical embodiment of the MlPs for controlled release would be solid partculates which would either be used ANTI granule' powder or solid monolith (shaped) form granules compressed or glued Into shaped fond or the particulates contained with a paint or other Such medIUTn. TI1TS array of MIP formats Is to embody any use of the materials also to confer the knowledge that surface area w'II contribute to the release of template. The target release chemical could be entrapped into the polymer during the polymerization step In another application target chemical can be adsorbed or re-adsorbed by the polymer.

The t;fth embodiment of the present Invention describes the use of polymers for controlled release. Invention describes several potential applications for the polymers prepared in SUCll a maimer as described above. One sucil application is for the controlled release of herbicides mto suitable environments mcludng but not limited to ponds (commercial and private) pools and aquaria This also covers the releases of chemicals consisting of but not restricted to herbicides insecticides fungicides algaecdes acarcides nematocides and nitrificaton Inhibitors into similar environments Fruther applications Intended for this patent are release of drugs from contact lenses for both recreational (e g. to treat tiredness) and medical uses (e g to treat infection) release of ntitrient chemicals for use in garden industry by pellet or net incorporation of MIP into paint for release of anti-fouling and anti fungal antibacterial chemicals from the painted surface mcorporaton of MIP into devices for release of ant-foulng anti Bengal antibacterial and similar chemicals at specific site incorporation of MIP Into plastic or other sleeting for release of anti fungal antibacterial anti-vral and similar chemicals at specific site (e g. I'ners work surface) incorporation of MIP into "patches" for chemical release for medical and recreational uses ( e.g ncotne caffeine delivery) subcutaneous delivery of pharmaceuticals from MIP controlled release of pharmaceuticals from implants which incorporates MIP and dental materials controlled release of pharmaceuticals by orally ingested powder controlled release of anti fungal anti- bacteral ant'-viral and similar chemicals t'or use of water sewage and enviromnental industries controlled release of perfumes from solid medium Incorporating MIP (e.g. paper wall paper work surfaces packaging)

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure I The library of functional monomers selected for screening.

Figure 2 Minimised representation of simane.

Figures Molecular complex formed between charged simazine and methacrylic acid.

Figure 4 Molecular complex fonned between charged smazine and HEM.

Figure 5. The release of simazine from MIP I. Figure 6 Tle release of simazine from MIP 2.

Figure 7. The release of sJmazne from MIP 3.

Figure 8: The kinetics of release of simazne from the HEM polymer (MIP 2) m water Table I. Binding energy table of monomers with charged smazine in vacuum.

Table 2 Polymer compositions Table 3. Polymer compositions Example 1. Experimental results which support the concept.

Release of simazine entrapped in molecularly imprinted polymer prepared in the presence of simazine The experiment below was performed using the computational method as described in patent PCT/GB01/00324 and covered In embodiment 1 Virtual library of functional monomers.

The workstation used to simulate monomer-template interactions was a Silicon Graphics Octane rowing the IRIX 6.5 operating system The workstation was configured with 195 MHz reduced instructions set processor I GB memory and a 10 GB fixed dove. This system was vised to execute the software packages SYBYL 6.9 (Tripos Inc. St Louis Missouri USA). The LEAPFROG algorithm was vised to screen the library of functional monomers on their possible interactions with the template The library used for this project contained 3 I commonly used t'unctonal monomers (neutral and charged) which possess polymensable residues and residues able to Interact with a template through 1 electrostatic hydrophobic van-der-Waals forces dpole-dpole interactions or reversible covalent bonds. The charges for each atom were calculated and the structures of the monomers were refined using moleculai mechanical methods. Energy mindnisaton was performed on each of the monomers in the database to a value of O 01 kcal mold The program was applied for 30 0()0 iterations and the results of these were examined and the empirical balding energy score evaluated (see Tables) The interactions contributing to the binding energy score are ionic and hydrogen bonds van-der-Waals dipole-dpole interactions and steric factors T he table of monomers is shown in Figure I Screening Firstly a molecular model of sunazine was designed The structure Is drawn and then all the atoms are given fonnal charges based on Gastieger-Huckel charged and then minimized giving tle lowest energy of this structure based on its charge and confnnaton to a value 0.0()1 kcal mold. This value is nonnally reached If the model is given at least 2000 Iterations and Is usually repeated to ensure the template has been fully minimsed. The minmsed structures of non-cilarged and charged atraz.ine are shown in Figure 2. The oxygen atoms are shown m red and the nitrogen atom is shown m dark blue The white atoms are carbon and the light blue atoms are hydrogen. The molecule of simazne was screened with the virtual library of functional monomers using the Leapfrog algorithm resulting in tables ranking the monomers with the highest binding score ( I able I) The binding energy shows that the best monomer for charged simaz.'ne is charged methacr-yhc acid. rifle methacrylc acid has been chosen as the best candidate to form a strong complex with the template. Example of molecular complex between simazine and methacrylic acid is shown in figure 3 As example of monomer forming weak interactions with smazne is hydroxyethyl methacrylate (HEM) (see Table 1) and portrayed in Figure 4.

From these results we synthesized polymers MIPI (MA-polymer) - molecular ratio i 5 smazine MA MIP2 (1-lEM-polymer)- molecular ratio 1.10 smazine. HEM MIP 3 (EGDMA-polymer)- no monomers, only cross-linker The polymers were synthesised by co-polymerzing 20% (w/w) monomer with 80% Of crosslinL;er in Methyl fonnamde using thermou,taton (see Table 2) Table 2: Polymer compositions Polymer MiPI MIP2 Simazine, mg 201 201 201 _. _ Methacrylic acid, 430 HEM, g _ _. .. __; ..

EGDMA, g 2 5 6.4 6

-

DMF, g 3.2 7.5 7.5 Initiator, mg 63 __ _ _ ln order to monitor the polymer performance, 500 mg of polymers were placed in I 1, of distilled water which was exchanged every second day. The simazme concentrations were measured by HPLC-MS. The quantification of simazne was performed on Waters HPLC In tandem with a bench-top triple quadrupole mass spectrometer model Micromass Quatro Micro (Waters, USA) equipped with an electrospray probe. The values of the voltages applied to the sampimg cone (40 V), capillary (3.2 V), extractor (1 V) and collision cell (20 eV) were optimized by continuous infusion nil order to achieve the highest possible sensitivity for simazine The electrospray probe was maintained at +350 C with a spray voltage of 450 V for positive onza.hon mode. The electron multiplier was set at 650 V HPLC-MS-MS analyses were earned out m MIRM mode, where one daughter fragment (124 m/z) was monitored. The Ht'LC conditions were next: mobile please- Acetonitrile containing 0 1% Fonnic acid, flow rate- 0 2 nl/nin, column- Luna 3 fun, i d.- mm, length- 50 mm (Phenomenex, UK) Every injection was earned for 5 min The q'antiiicaton was performed using the Massl,ynx software I'he results of the simazine release showed the correlation with molecular modelhug. Tile MA-based polymer demonstrated the high affinity towards the template and very slow and steady release of romaine into water (Figure 5).

The simazine release from mcthacrylic acid based polymer Total quantity released - : 180 approx. 0.35 mg in 25 days 1

CJ 140 100

ill go () , . . , , .. . , . . , _.

0 2 4 6 8 10 12 14 16 18 20 22 24 2fi 28 Tim,, days Example 2. Development of optical chip for combinatorial screening of polymer-target chemical interactions.

Monomer mixture for slide modification were prepared as 20% solution of monomer and ethylene glycol dimethacrylate (1 9 ratio (w/w)) in DMSO cillorofonn (80. 20) Tle initiator azobs-(cyclohexanecarbontrile) was added at To (w/vol). l he compositions of the polymers are in Table 3. Idle solution was soncated for 5 min Alquots of 0.3 pL of monomer solution were deposited on a cellulose acetate slide and polymersation was carried out placing the slide under a UV source for 10 min Table 3. Polymer compositions _Polymer Monome (g) _ _ Crosslinker (g) So_vent (g) __PI M_acrylcacid (0 5 g)_ __ _128 _ 3 14 P2 Acrylamide (0 5 g) 0 154 3. 20 P3 2-Vynilprdine (0.5 g) 0.104 3.02

_

P4 2-Vynlimidazole (0 5 g) 0.117 3.08 __ P6 Acrylic acid _ _ (0 5 L;) 0.153 _3 26 _P7 jV nilpirdine_ (0.5_) __ _04 3.02 P9 Allylamine (0 5 g) 0.193 3.46 PI l! ltaconic acid (O 5 g) 0 084 2.92 _ P 12 _1 bisacrylamde _ (0 5 g) _ 0.071 _ __ 2 85 P16 DEAEM (0.5 g) 0. 072 2.86 1, . .. _.

P17 AMPSA (0 5 g) 0 053 _ _ 2 76 _. _ _ _. _. _ _.. . _. _. _. _...

The screening of the binding of target compounds (dyes and toxins) was performed visually Is

Claims (5)

EXEMPLARY CLAIM(s) We claim.

1. Rational design procedure for the rapid development and optimization of polymers for release of the adsorbed (entrapped) chemical compound which includes. (i) selection of appropriate monomers watt affinity to ensure appropriate level of' bmdmg-release ol' target compound, and (i') polymer:zmg corresponding monomers us the presence of target compound leading lo entrapment ol' such compounds by created polymer.

2. Else procedure as described m Claim 1 where the ratona.l selection of appropriate monomers Is based on computational approaches and molecular modeling.

3 The procedure as described In Clann I where the rational selection of appropriate monomers Is based on combinatorial approaches

4 A procedure as described In Claim 1 where monomers selected from these possessing polymerzable r esidues and residues, able to interact with a target through electrostatic, hydroplobc, van-der-Waals forces, dpole- dipole interactions or reversible covalent bonds. The monomers are selected from group of vinyl monomers, allyl monomers, acetylenes, acrylates, methacrylates, amino acids, nucleosides, nucleotides, carbohydrates, phenols, heterocycles, aniline, and their derivatives.

5. 'I'he target used in Claim I is selected from a. group mcludmg drugs, pesticides, fragrances or other synthetic molecules possessing biological activity.

6 The polymers synthesized by using procedures described In Claims 1-5 for application in healtlIcare, enviromnental treatment, homecare, personal hygiene, and agriculture.