Water infusion and drug effusion in drug release polymers and drug diffusion in mucosae and muscle

A S Clough, F E Gauntlett, M S RihawyUniversity of Surrey

M Braden, M P Patel, QMW, LondonJ Booth, Astra- Zeneca, Macclesfield

A Cruchley, Royal London and St Barts Hospital

University of SurreyGuildford

SurreyEngland

Outline of Talk

• ION BEAM MICRO-ANALYSIS OF DIFFUSION• WATER INGRESS INTO AND DRUG EGRESS

FROM IN-MOUTH POLYMERS• WATER INGRESS INTO AND DRUG EGRESS

FROM CYLINDRICAL IN-BODY POLYMERS• DRUG INGRESS INTO ORAL MUCOSAE• DRUG DIFFUSION IN MUSCLE• FUTURE WORK.

Ion Beam Analysis at Surrey 2 Years agoAccelerator: 2MV Van de Graaff Ion source: 3HeScanning Micro-beam : Beam size 10m to 200m Beam current - nA to A

Beam scan of up to 3mm 3mm.

Magnet

Computer controlled raster scanned deflection plates

Quadrupole focussing magnets

V de G Objectaperture

LN2 cooled sample stage

Scanning microbeam target chamber

Side view Front view of sample stage

Particle detectors

LN2 cooled sample stage

Focussed 3He scanning microbeam

X-ray detector

Scanning zone

Cu blocks

Sample

Scanning Microbeam Target Chamber

•NRA (Nuclear Reaction Analysis)

Protons detected from the reaction:

3He + d p + Q = 18.4 MeV

•Rutherford BackScattering (RBS)

•PIXE (Particle Induced X-ray Emission)

Water and drug profiles following water ingress into in-mouth planar polymers

Water uptake and drug release have been characterised for:

• chlorhexidine diacetate drug loadings of 0%,4.5%,9% and 15% of dry weight polymer

• 3 polymers – Addition Cured silicone, Condensation Cured silicone and PEM/THFM

• 2 immersion solutions – 90% pure H2O/10%D2O and 90% PBS/10%D2O

• a series of 7 immersion times from 1 hour to 6 months

using three techniques:

scanning 3He ion microbeam NRA ,PIXE and backscattering to profile the water ingress, correlate water and drug distributions and enable inter-sample normalisation

gravimetric measurements to establish absolute normalisation of water uptake

UV measurements to establish mass of drug released to immersion solution.

Sample Preparation

• Mix drug and silicone polymer, press into oblongs 20 mm 10 mm ~1 mm.

• Immerse in 50 ml water (10% D2O/ 90%H2O) or buffer solution (10% D2O/ 90% Buffer solution) at 37C

• Remove, hold between copper blocks on sample plate, cut section at the block height; plunge in LN2

• Mount sample plate on LN2 cooled sample stage and do 3He beam scan

0

2

4

6

8

10

12

14

1 33 65 97 129 161 193 225 257 289 321 353 385 417 449 481 513 545

Ln counts

Channel Number

ProtonsAlphas

RBS

NRA Spectrum

Drug-containing silicone polymer exposed to 90%H2O/10% D2O at 37C

Cu ClSiAl

 

 

Example of an addition-cured polymer PIXE spectrum, drug loading 4.5%, PBS immersion time 1 hour,

displayed using a square vertical scale.

9% Drug loaded Addition Polymers, 2w exposure to PBS at 37 C

RBS Silicon X-rays Cl X-rays Protons from Deuterium

0

50

100

150

200

-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3

Polymer thickness (mm)

Rel co

nc (

arb

un

its)

1-d Diffusion Profiles of Water from 90%H2O/10%D2O

Addition cured Polymer

Condensation Cured Polymer

PEMA/THFM

0

25

50

80 130 180 230D i s t a n c e a c r o s s p o l y m e r ( m m )

0

25

50

75

100

60 110 160 210 260D I s t a n c e a c r o s s p o l y m e r ( m m )

0

25

50

60 110 160 210 260

D I s t a n c e a c r o s s p o l y m e r ( m m )

1 h

2 4 h

3 3 6 h

4 0 3 6 h

1-d water diffusion profiles from 90%PBS/10%D2O

Addition Cured Polymer

Condensation Cured Polymer

PEMA/THFM

0

20

40

60

80

100

120

140

160

180

0 50 100

Immersion Time^1/2 (hours^1/2)

Wat

er u

pta

ke a

s a

per

cen

tag

e o

f p

oly

mer

mas

s

9% CondensationWater9% CondensationPBS

0

2

4

6

8

10

0 50 100

Immersion Time^1/2 (hours^1/2)

Wat

er u

pta

ke a

s a

per

cen

tag

e o

f in

itia

l p

oly

mer

mas

s

9% Addition Water9%Addition PBS

0

2

4

6

8

10

12

14

16

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

Wate

r u

pta

ke a

s a

perc

en

tag

e o

f p

oly

mer

mass

9% PEM/THFMWater9% PEM/THFMPBS

0

5

10

15

20

0 50 100

Time1/2 (Hours1/2)

fracti

on

of

ori

gin

al d

rug

0

5

10

15

20

25

0 20 40 60 80

Time1/2 (Hours1/2)

0

5

10

15

20

0 20 40 60 80

Time1/2 (Hours1/2)

Addition Cured Silicone Condensation Cured Silicone PEMA/THFM

0

4

8

12

16

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

9% PEM/THFMWater

0

60

120

180

0 20 40 60 80Immersion Time^1/2 (hours^1/2)

9% CondensationWater

=

0

2

4

6

8

10

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

Wat

er u

ptak

e %

of i

nitia

l po

lym

er m

ass

9% Add H2O

Drug Release and Water Uptake from 90%H2O/10%D2O at 37C

Addition Cured Condensation Cured PEMA/THFM

0

0.5

1

1.5

2

2.5

0 20 40 60 80

Time1/2 (Hours1/2)

Perc

en

tag

e o

f o

rig

inal d

rug

0

1

2

3

4

5

0 20 40 60 80

Time1/2 (Hours1/2)

0

0.5

1

1.5

2

2.5

0 20 40 60 80

Time1/2 (Hours1/2)

0

1

2

3

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

Wat

er u

ptak

e as

a p

erce

ntag

e of

in

itial

pol

ymer

mas

s

9% Addition PBS

0

2

4

6

8

10

12

0 20 40 60 80Immersion Time^1/2 (hours^1/2)

9% CondensationPBS

0

1.5

3

4.5

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

9% PEM/THFM PBS

Drug Release and Water uptake from 90% PBS/10%D2O at 37C

Percentage of Original Drug released to the PBS from a 9% Drug Loaded Condensation Cured

Silicone Polymer

0

1

2

3

4

5

0 20 40 60 80Time1/2 (Hours1/2)

% o

f Dru

g R

elea

sed

-25.0000

-20.0000

-15.0000

-10.0000

-5.0000

0.0000

5.0000

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

% of original polymermass lost

Cylindrical Polymer/Drug Depots

• Solid cylindrical depots (2.25 mm in diameter) of poly(dl-lactide) P(DL)LA loaded with goserelin in ratios of 20%, 30% and 40% by weight respectively were prepared by melt extrusion of drug/polymer mixtures.

• Many sections 18 mm long were cut, weighed and immersed in separate glass jars containing 45ml buffer solution mixed with 5ml D2O. These were held at a constant temperature of 37C for times between 1 hr and 7 days.

• On removal they were dried lightly with filter paper, weighed and cut into sections 3mm long. These were transferred to the sample plate, held at liquid nitrogen temperature and subsequently scanned with the 3He ion microbeam – energy 1.3 MeV, diameter 10 microns, current ~ 1nA.

20%

30%

40%

1 Hour 4 Hours 1 Day 4 Days 7 Days

Cylindrical Polymers – colour scale normalised to 7 day 30% data

1hr 4hr 1d 4d 7d

Water diffusion into 40% drug loaded cylindrical drug-release polymer from 90% PBS/ 10% D2O at 37C – colour scale normalised to 1d data

0,000

0,010

0,020

0,030

0,040

0,050

0 1 2 3 4 5 6 7

Immersion time (days)

Wat

er u

ptak

e (g

)

20%

30%

40%

Water Uptake of Drug Depots for Different Immersion Times

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6 7

Immersion time (days)

Frac

tiona

l wei

ght c

hang

e (%

)

20%

30%

40%

Fractional Weight increase of Polymer after immersion

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7

Immersion time (days)

Frac

tion

of d

rug

rele

ased

(%)

20%

30%

40%

Fraction of Drug Released

Ion Beam Analysis at Surrey TodayPresent Accelerator: 2MV TandetronIon source: 3He, 4He or protonsScanning Microbeam : Beam size 1m to 200m Beam current - nA to A

Beam scan of up to 2.5mm 2.5mm.

Magnet

Computer controlled raster scanner deflection plates

Quadrupole focussing magnets

Tandetron Magnet Objectaperture

LN2 cooled sample stage

Scanning microbeam target chamber

External Scanning microbeam (~ 10 microns spot size)

Nano beam (~10 nm spot size) under construction

Drug diffusion in pig mucosa

• Mucosa exposed to 10% solution of chlorhexidine sulphate in water for 90 minutes

• Cut perpendicular to surface, backcooled with LN2, and scanned by 2 MeV, 2 micron spot size, proton microbeam.

• Characteristic X-rays detected.

Reservoir of test compound

Threaded collar allows tightening of

chamber without disturbing tissue

Outlet portTissueInlet port

Teflon chamber

Viewing port allows air bubbles to be checked for.

Cover slip prevents evaporation of test

compound.

Flow Through Chamber

Cross-section of mucosal epithelium

Cl distribution after 90 min exposure to chlorhexidine sulphate solution

K distribution after 90 min exposure to chlorhexidinesulphate solution

Direction of Chlorhexidine ingress

Chlorhexidine uptake distribution in mucosae for a dose time of 90 minutes.

0

1020

3040

5023

21.5 20

18.5 17

15.5 14

12.5 11 9.5

86.5

53.5

20.5 -1

-2.5

Depth (microns)

Chlo

rine X

-ray

coun

ts

Fluorinated Drug Diffusion in porcine muscle tissue

Problem: Detecting fluorine at pp104 with microbeam currents (100pA) and spatial resolution of 1 micron

Solution: Use 3.2 MeV ions and the reaction :

19F (p, ) 16O*

Characteristic 6.05 MeV -rays detected with high efficiency hyper-pure Germanium detector

-Energy (MeV)

N

Spectrum of -rays from 19F (p, ) 16O*

Fluorine Ingress Profile

0

10

20

30

40

50

60

70

80

0 50 100 150 200 250

distance (mm)

no

rmal

ised

co

un

ts

Work in progressDiffusion of drugs that contain either fluorine or chlorine or are deuterated into different biological tissues

Diffusion of water(labelled with deuterium) at low concentration into resins and polymer films

Diffusion of chlorine and water into cements, mortars and concrete

Development of nano-beam and associated detectors

Reactions Detected:(iii) p + 11B + 8Be Q=8.582 MeV

Sensitivity Estimate : parts per 105

Spatial Resolution of Microbeam : ~ 1m

1

10

100

1000

10000

100000

0 1 2 3 4 5 6 7 8

Energy (MeV)

Co

un

tsRBS

Reactions Detected:(ii) p + 19F + 16O Q=8.114 MeV

Sensitivity Estimate : parts per 104

Spatial Resolution of Microbeam : ~ 1m

1

10

100

1000

10000

100000

1 2 3 4 5 6 7 8 9

Energy (MeV)

Co

un

tsRBS

RBS Pile-up

• Connected in 3 groups of 4 detectors

• Outputs are summed together

The CdZnTe ArrayThe CdZnTe Array

Reactions Detected:(i) 3He + D + p Q=18.352 MeV

0

10

20

30

40

50

60

70

80

90

1.5 4 6.5 9 11.5 14

Energy (MeV)

Co

un

ts

Sensitivity Estimate : parts per 104

Spatial Resolution of Microbeam : ~ 1m

p

• can absorb the full energy of protons up to ~15MeV

• pin connected to the front of the detector is earthed, via a thin (50-100nm) platinum contact layer diffused onto the crystal surface

•15mm x 15mm x 3mm

• other pin for signal

The CdZnTe DetectorsThe CdZnTe Detectors

The array is located ~1cm upstream of the target and subtends a useful solid angle of ~/2 steradians (1/8 sphere).

(We are improving it to allow a solid angle coverage of steradians).

ION BEAM

Cutaway View:Cutaway View:

Array Solid AngleArray Solid Angle

Addition 0% for various times in 90% H2O/10% D2O

0

50

100

150

200

-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3

mm

wate

r co

ncen

trati

on

(arb

itra

ry u

nit

s)

1 week

24 weeks

15 minutes

24 hours

Water Uptake of the Addition Cured Silicone Polymer Loaded with 0% Drug by weight for different immersion times in PBS (90%H2O/ 10%D2O)

0

5

10

15

20

25

30

35

40

80 100 120 140 160 180 200 220 240

Distance (mm)

Wat

er c

onc.

(arb

itrar

y un

its)

2 weeks

1 Day

4 Weeks

24 Weeks

2-d maps showing diffusion of deuterated water into a planar glass sample - Scott 8330 exposed to 300 C D2O

Deuterium map Si X-ray map

Cu RBS map

X-ray spectrum

0

200

400

600

800

1000

1200

0 1 2 3 4

Energy (keV)

Cou

nts

Si from polymer matrix

Cu from Cu blocks

Drug –free polymer exposed to water at 37C

3He

backscatters

Addition 9% for various times in 90% H2O/ 10% D2O

0

50

100

150

200

-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3

mm

Wat

er c

on

cen

trat

ion

(ar

bit

rary

un

its) 15 minutes

1 week

24 weeks

24 hours

1d profile:

Addition 4.5% for various times in 90% H2O/ 10% D2O

0

50

100

150

200

-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3

mm

wate

r co

ncen

trati

on

(arb

itra

ry u

nit

s)

1 week

24 weeks

15 minutes

Addifiton 15% for various times in 90% H2O/10% D2O

0

50

100

150

200

-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3

mm

Wate

r co

ncen

trati

on

(arb

itra

ry u

nit

s)

1 week

24 weeks

15 minutes

24 hours

Water Uptake of the Addition Cured Silicone Polymer Loaded with 4.5% Drug by weight for different immersion times in PBS (90%H2O/ 10%D2O)

0

5

10

15

20

25

30

35

40

80 100 120 140 160 180 200 220 240

Distance (mm)

wate

r conc. (

arb

units)

2 Weeks

1 Days

4 Weeks

24 Weeks

Water Uptake of the Addition Cured Silicone Polymer Loaded with 9% Drug by weight for different immersion times in PBS (90%H2O/ 10%D2O)

0

5

10

15

20

25

30

35

40

80 100 120 140 160 180 200 220 240

Distance across polymer (mm)

Wate

r conc. (

arb

itra

ry u

nits)

2 Weeks

1 Day

4 Weeks

24 Weeks

Water Uptake of the Addition Cured Silicone Polymer Loaded with 15% Drug by weight for different immersion times in PBS (90%H2O/ 10%D2O)

0

5

10

15

20

25

30

35

40

80 100 120 140 160 180 200 220 240

mm

Wate

r conc. (

arb

itra

ry u

nits)

2 Weeks

1 days

4 Weeks

24 Weeks

Cl/Si X-ray ratio for 9% Addition and 9% Condensation Polymers

0

0.002

0.004

0.006

0.008

0.01

0.012

0 10 20 30 40 50 60

time1/2 (hours1/2)

Cl/S

i X-r

ay r

atio

9% Condensation Polymer

9% Addition Polymer

Cl/Si Ratio for Addition-Cured Polymer

0

0.0038

0.0076

0.0114

0.0152

0 10 20 30 40 50 60

Time1/2 (hours1/2)

Cl X

-ray/S

i X

-ray In

ten

sit

y R

ati

o

15%

9%

4.50%

0%

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Radial distance (mm)

Ab

so

lute

co

nc

en

tra

tio

n o

f w

ate

r (g

cm

-3)

1 hour

4 hours

1 day

4 days

7 days

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Radial distance (mm)

Ab

so

lute

co

nc

en

tra

tio

n o

f w

ate

r (g

cm

-3) 1 hour

4 hours

1 day

4 days

7 days

Graph Showing the % Drug Mass Released and % Polymer Mass Loss for the Condensation Cured Silicone Polymer at a drug loading of 9% for Varying Immersion Times in a PBS Solution

-12.0000

-10.0000

-8.0000

-6.0000

-4.0000

-2.0000

0.0000

2.0000

4.0000

6.0000

0 10 20 30 40 50 60 70

Immersion Time^1/2 (hours^1/2)

% of original drug released

% of original polymer mass lost

Graph Showing the % Polymer Mass Loss for the Condensation Cured Silicone Polymer at a drug

loading of 9% for Varying Immersion Times in a PBS Solution

-25.0000

-20.0000

-15.0000

-10.0000

-5.0000

0.0000

5.0000

0 20 40 60 80

Immersion Time^1/2 (hours^1/2)

% of original polymermass lost

S distribution after 90 min exposure to chlorhexidine sulphate solution

P distribution after 90 min exposure to chlorhexidine sulphate solution

Cl distribution after 90 min exposure to chlorhexidine sulphate solution

S distribution after 90 min exposure to chlorhexidine sulphate solution

Direction of Chlorhexidine ingress