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Introduction to polymer-based drugdelivery systems

micells dendrimers star -shaped polymers

4- and 6-arm starPCL- p PEGMAs synthesis characterization core degradation encapsulation properties

Conclusions

Acknowledgements

Outline


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Introduction drug-delivery systems

Polymer therapeutics term coined by Helmut Ringsdorf and Ruth Duncan

Angew. Chem. Int. Ed. 1981 , 20 , 305-325, Nat. Rev.Drug Discovery 2003 , 2 , 347-360.

Most of clinically used drugs are small hydrophobic moleculeswith molecular weights < 500 g/ mol.

rapid diffusion into healthy tissues small amounts of drugs reach the target sites therapeutics is associated with side effects

Major goal: improving the therapeutic index!(defined as ratio of the toxic dose to the therapeutic dose)

protein -polymer conjugates drug -polymer conjugates supramolecular drug -delivery systems


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Micelles

Single polymer chain

hydrophilicchain

Hydrophobicchain

weakly water-soluble drug

micelle

cmc

Drawbacks:unstable under differentenviromental conditions: high dilution pH temperauture pressure

sterilization

Dendrimers

weakly water-soluble drug

Drawbacks: low loading capacity high costs (multisteps

synthesis) not suitable for large

scale applications

DdS: Properties (II)


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Star-shaped polymers: General conceptStar-shaped polymers can effciently combine the properties of self-assembled micelles and dendrimers

core -shell structure

unimolecular micellar behavior high loading capacity

.. and they circumvent the main drawbacks of these systems: low stability high synthesis costs

guest molecules

6-hydroxycaproic acid

p PEGMA

(bio)degradation

biocompatiblehydrophilic shell

degradablebiocompatible

hydrophobic core


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hydrophobichydrophilic

Br

OBr

O

O

O

O

Br n

OR2

RO

R2O

HO

OO

OR1

RO

R1O

n

O

O

O

O

Br n

OR3

RO

R3O

O O

PEG

p

O

OOH

OHRO

OH

OH

OHOH

OOR 1

OR1R

1O

O

OR 2

OR2R

2O

OOR3

OR 3R3O

O

OOPEG

NEt 3 , THF24-72 h, RT

CuBr/PMDETAtoluene, 90 C

Tin(II)-octoate

130 C, 4 h+

R = H or R = R 1 or

R = R 2 or R = R 3 or

R 1

R 2 R 3

Star-shaped Polymers: Synthesis


10/28

Polymer Conversion

14-arm Star-PCL

Mw 3200~ 100%

24arm Star-PCL

Mw 5600~ 100%

3

4-arm Star-PCLMw 7200 ~ 100%

46-arm Star-PCL

Mw 9800~ 100%

Br

OBr

O

O

O

O

Br n

OR2R

2

O

R2OHO

O

O

OR 1R

1O

R1O

nNEt 3, THF

24-72 h, RT

1.21.41.61.82.02.22.42.62.83.03.23.43.63.84.04.24.4

1.21.41.61.82.02.22.42.62.83.03.23.43.63.84.04.24.4

d , ppm

Quantitative fuctionalization of star PCL

2000 3000 4000 5000 6000 7000 8000 9000 10000

m/z

*

f


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O

O

O

O

Br n

OR2

R2O

R2O

OO

PEG

O

O

O

O

Br n

OR3

R3O

R3O

O O

PEG

p


14 16 18 20

0.0

0.4

0.8

1.2 Temp. 70oC, [M]/[I] = 200:1

n o r m a l i z e d R I r e s p o n s e

, a . u

elution volume, mL

10 min30 min1 h2 h3 h4 h5 hStarPCL

14 15 16 17 18 19 20

0.00

0.08

0.16

0.24

0.32

0.40 Temp. 90oC , [M]/[I] = 200:1

R I r e s p o n s e

elution volume, mL

10 min30 min1 h2 h3 h4 hStar-PCL

0 50 100 150 200 2500.0

0.4

0.8

1.2

l n ( [ M

0 ] / [ M ] )

time, minutes

0 50 100 150 200 250 3000.0

0.4

0.8

1.2

l n ( [ M

0 ] / [ M

] )

time, minutes

8.5 9.0 9.5 10.0 10.5 11.0 11.5

0.0

0.2

0.4

0.6

0.8

1.0

Temp. 70 o C, [M]/[I] = 20:1

n o r m a l i z e d R I r e s p o n s e , a

. u

elution volume, mL

10 min20 min40 min

70 min2 h3 h4 h

4-arms StarPCL-Br

14 15 16 17 18 19 20

0.0

0.2

0.4

0.6

0.8

1.0

Temp. 90 o C, [M]/[I] = 20:1

n o r m a l i z e d R I r e s p o n s e

, a . u

.

elution volume, mL

10 min2 h4 hStarPCL-Br

ATRP of PEGMA

ATRP f PEGMA 1H NMR


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ATRP of PEGMA 1H NMR

star-initiator

10 minutes

30 minutes

60 minutes

O

O

O

O

Br n

OR 2RO

R2O O

O

O

O

Br n

OR3

RO

R3O

O O

PEG

p

OR2

OR 2R2O

O OR3

OR3

R3O

O

OOPEG


R = R 2 or R = R 3 or

ppm

All arms initiated the polymerization of PEGMA

S PCL PEGMA


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Upscaling of polymer P4, after precipitation: 17 g, PDI = 1.13

polymer P1 P2 P3 P4 P5 P6 P7 P8

M/I 40:1 40:1 200:1 200:1 60:1 60:1 240:1 240:1

no. of arms 4 4 4 4 6 6 6 6PEGMA Mw (Da) 475 1100 475 475 475 1100 475 1,100

Mn (Da)(GPC) 12,600 24,900 25,000 26,600 20,700 39,600 35,000 41,000

Mn (Da)(1H NMR) 21,400 48,000 51,800 59,400 32,100 65,400 83,400 170,000

Conversion 80% 85% 48% 56% 80% 85% 70% 60%

no. of PEGMA/arm 8 8.5 24 28 8 9 26 24

PDI (GPC) 1.3 1.24 1.16 1.13 1.29 1.3 1.18 1.15

Dh (nm)

(DLS, H2O)6 7.6 9.2 9.8 7.2 11.8 13.6 17.4

Dh (nm)(DLS, CH3Cl)

nd 6.4 nd 8.2 5.8 9.2 11.8 13.4

All starPCL- p PEGMA present unimolecular micellar behavior

Star PCL p PEGMAs

ATRP f PEGMA


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8 12 16 20

7.0, 1.176-arm starPCL-Br

(P5 ) 32.1, 1.29(P6 ) 65.4, 1.3

(P7 ) 83.4, 1.18(P8 ) 170, 1.15

Mn

(kg/mol), PDI

elution volume/mL

8 12 16 20

4.6, 1.17

(P1 ) 21.4, 1.30(P2 ) 48.0, 1.24

(P3 ) 52.8, 1.16(P4 ) 59.4, 1.13

4-arm starPCL-Br

Mn

(kg/mol), PDI

elution volume/mL

ATRP of acrylates using star macroinitiators is still a challenge due to star -star coupling reactions not all of the bromine end -capped sites act as initiators for ATRP

Consequences: broad polydispersity indices and unsymmetrical GPC profiles

Our optimized procedure allows the synthesis of well-defined4- and 6-arm starPCL- p PEGMA (PDI


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Selective PCL degradation

O

O

O

Br

O

OPEG

n O

O

O

O

Br

O

OPEG

n

O

O

O

OO

Br O

OPEG

n O

O

O

O

Br

O

OPEG

n

O

O

O

O

Br O

OPEG

n O O

O

O O

Br

O

OPEG

n

O

Br

OO

PEG

OH

OOH

OH

OH

OH

OH

OH

OHO

OH

p

p

p+

p

p

p

p

6

6n

acid or base catalyzed degradation enzymatic degradation

For enzymatic degradation of PCL see i.e. Eur. J. Sci. 2007 , 31 , 119-128.

aq. HCl,dioxane, RT

A id t l d d g d ti


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0.51.01.52.02.53.03.54.04.55.0

0.51.01.52.02.53.03.54.04.55.0

0.51.01.52.02.53.03.54.04.55.0

(a)

(b)

(c)

d , ppm

1 H NMR spectra of (a) p (PEGMA) from the

hydrolysis

of 6-arm starPCL- p PEGMA,(b) 6-arm star-PCL- p PEGMA,(c) 6-arm starPCL-Br.

8 12 16 20 24

PDI 1.17

PDI 1.15

PEGP8 after hydrolysis at 60 oC

P8 after hydrolysis at R.T.

P8

6arm starPCL-Br

Elution volume, mL

room temperature selective hydrolysisof the PCL-core

H2O

Acid catalyzed degradation

Enzymatic degradation of PCL core


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Enzymatic degradation of PCL core

14 16 18 20

0.0

0.2

0.4

0.6

0.8

1.0

1.2

R I r e s p o n s e ,

a . u .

Elution volume, mL

P9 - t 0P9 - 1 dayP9 - 2 daysP9 - 4 days

Lipase from Rhizopus arrhizus

Conditions: lipase/polymer 1:5, in phosphate buffer solution (pH=7), at 37 C

in vitro biodegradable core

D l ti di 3


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Dye encapsulation disperse orange 3

polymer

disperse orange 3

N NN

O

O NH2

water insoluble dye

300 400 500 600 700 800

0.0

0.4

0.8

1.2 20:1

16:112:1

10:1

8:1

4:1

1:1

0

[dye]/[P4],[P4] = 25 M

a b s o r p t i o n / a

. u .

wavelength/ nm

20:118:116:1

14:112:110:19:18:17:16:15:14:13:12:11:10.5 mM dye,0 mM P4

Dye encapsulation (II)


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300 400 500 600

0.0

0.4

0.8

1.2

[dye]/[polymer]

A b s o r p

t i o n

/ a . u .

wavelength/ nm

20:1

18:116:114:112:110:19:18:17:16:15:14:13:12:11:1

300 400 500 600 700

0.0

0.4

0.8

1.2

[dye]/[polymer]

a b s o r p

t i o n

/ a . u .

wavelength/ nm

26:124:122:120:118:116:114:112:1

0 5 10 15 20

0.4

0.8

1.2

a b s o r p

t i o n a

t 4 4 2 n m

/ a . u .

no. of encapsulted molecules of guest 1 per molecule of P4

4-arm starPCL- p PEGMA, P4 6-arm starPCL- p PEGMA, P7

12 16 20 24 28

0.6

0.8

1.0

1.2

a b s o r p

t i o n a

t 4 4 3 n m

/ a . u .

no. of encapsulated molecules of guest 1 per molecule of P7

Dye encapsulation (II)

Dye encapsulation (III)


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Dye encapsulation (III)

Unloaded polymer ( P4 ) Polymer ( P4 ) loaded with disperse orange 3Dh (DLS, H2O) 9.8 nm 11.6 nm

DLS measurements strongly support the formation of unimolecular host-guest architectures.

Simple PEGylation is not sufficient to build up stable unimolecular core-shell systems!

our systems: encapsulation inside the polymer

R. Haag et al., Angew.Chem. Int. Ed. 2007 , 46 , 1265.R. Haag et al., Macromol. Rapid Commun. 2008 , 29 , 172.

in the literature: encapsulation by polymer aggregation

Drug encapsulation: Furosemide


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8 6 4 2 0

f d+e cba

DMF

DMFH2O

P4 + guest 2

P3 + guest 2

P2 + guest 2

guest 2 + DMFin D 2O

P1 + guest 2

/ ppm

8 6 4 2 0

f d+e cba

DMF

H2O DMF

guest 2 + DMFin D 2O

P8 + guest 2

P7 + guest 2

P6 + guest 2

P5 + guest 2

/ ppm


guest 2 4 5 7 7 6 5 10 10

S

Cl

NH

OO

O

NH2

OHO

a

bc

d e

f antihypertensive and antidiuretic activity for the treatmentof excessive fluid accumulation and swelling (edema) of the

body caused by heart failure, cirrhosis, chronic kidney failure,and nephrotic syndrome

Drug encapsulation: Furosemide

Drug encapsulation: Hydrochlorothiazide


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Drug encapsulation: Hydrochlorothiazide

8 6 4 2 0

ba

H2ODMF DMF

P4 + guest 3

P3 + guest 3

P2 + guest 3

P1 + guest 3

guest 3 +DMFin D2O

/ ppm


guest 3 22 18 24 24 34 18 36 36

NH

NHSS

O

O

NH2

Cl

OOa

b

antihypertensive and antidiuretic activity for the treatmentof heart failure, cirrhosis, chronic kidney failure, also effectivefor nephrogenic diabetic insipidus and hypercalciuria

8 6 4 2 0

guest 3 + DMFin H2O

P8 + guest 3

P7 + guest 3

P6 + guest 3

P5 + guest 3

H2O DMFDMF

ba

/ ppm

in D2O

Conclusions


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New water-soluble, well-defined 4- and 6-arm star-shaped polymers as

unimolecular micelles have been successfully synthesized;

High loading encapsulation capacities of different hydrophobic drugs and

other hydrophobic guests;

Room temperature selective degradation of the PCL core has proven the

homogeneous distribution of the PEGMA units over the arms;

Enzymatic degradation experiments using lipase from Rhizopus arrhizus

have demonstrated that the PCL core of the starPCL p PEGMAs is in vitro

biodegradabile;

Potential nanocarriers for parenteral drug administration.

Conclusions

Acknowledgement Infos under


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Acknowledgement http://www.schubert-group.com

Dr. Richard Hoogenboom, Dr. Michael Meier,Prof. Jean-Franois Gohy (CMAT, Belgium), Prof. Dr. Ulrich S. Schubert

3rd Generation: Higher hydrophlicity


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3 Generation: Higher hydrophlicity

O

OH

OH

OH

O

OH

O

O

O

O

Br

Br

Br

OBr

O

Cl

O

O

O

O

Br

Br

PCl 5

Synthesis of homo-branching agents

O

O

O

O

n

OR1

R1O

R1O

O

O

O

O

Br

Br

R 2

Property screening


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Property screening

J. Am. Chem. Soc. 2004 , 126 , 11517.

0,000 0,005 0,010 0,0150,00

0,01

0,02

0,03

0,04

4 6

[ m e t h y l o r a n g e ] / ( m o l / L )

[polymer] /( mol/L)

Methylorange: pH-Indicator

NN

SN O

O

O

Na+

NN

SN

+ O

O

OH Na

+

+H+basic form; yellow color

acidic form; red color

Maximal loading: 6.6 7.2 MO/micelle

INI: approx. 0.5 MO/micelle

Transport of guest-molecules: AUC


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Transport of guest molecules: AUC

unloaded micelles:

Non UV absorbing

loaded micelles:

Guest is UV absorbing300 400 500 600 700

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

loaded micellesunloaded micelles

A b s o r b a n c e

(nm)0 1000 2000 3000 4000 5000 6000

0.0

0.2

0.4

0.6

0.8

1.0

P1P2P3P4P5P6

N o r m a

l i z e

d c (

M )

Meff

(g/mol)0 3 6 9 12 15 18

0

500

1000

1500

2000

2500

3000

3500

M e

f f ( g / m o

l )

DP PCL block


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og schramm aachen 07.02.2012

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