the chemistry of sight: material innovations in eye care ... · • the lens is situated behind the...

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www.acs.org/acswebinars www.acs.org/acswebinars Slides available now! Recordings will be available to ACS members after one week

2016 Material Science Series “The Chemistry of Sight: Material Innovations in Eye Care and Contact Lenses”



Mark Jones Executive External Strategy and

Communications Fellow,

Dow Chemical

Heather Sheardown Professor, Department of Chemical

Engineering, McMaster University

THE CHEMISTRY OF SIGHT: MATERIAL INNOVATIONS

IN EYE CARE AND CONTACT LENSES

Heather Sheardown

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The Eye

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Contact Lenses

• 100 million contact lens wearers

worldwide

• 1.4% of population but only 4% of

2.4 billion people who wear glasses

• To be accepted, contact lenses

need to be simpler, more

convenient and very very

comfortable

16

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Contact Lenses

3 types of lenses commonly used

• Rigid gas permeable lenses

• Soft hydrogel lenses

• Silicone hydrogel lenses

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Desirable Properties of

Contact Lenses

• Ability to correct vision

• Comfort in the eye

• Low deposition of tear components

• Mechanical properties (resistance to tear)

• Oxygen permeability

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Soft Contact Lenses

• Developed early 60s – originally from

poly (hydroxyethyl methacrylate)

• Made from slightly crosslinked

hydrophilic polymers

• Polymers added to alter water uptake

which determines oxygen permeability

• Generally thought to be very

comfortable but limited wear time due to

low oxygen permeability

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Typical Soft Contact Lenses

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Rigid Gas

Permeable Lenses

• Introduced in the late 70s

• Show high oxygen permeability but lack comfort

• Copolymers of PMMA and silicone containing materials –

typically methacryloxypropyltris(trimethyoxy) silane +

hydrophilic comonomers to impart hydrophilic character to the

lenses

• Development of fluorine containing RGP lenses based on

realization that the fluoroderivatives may improve oxygen

permeability and resistance to deposit formation on lenses

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Composition of RGP Lenses

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Silicone Hydrogel

Contact Lenses

• Recognition of outstanding oxygen permeability of silicone rubber

• Oxygen transport occurs through the silicone phase rather than water phase as with traditional soft contact lenses

• Silicone elastomers on their own stick to the cornea

• Combine HEMA with monomer so successfully used in the manufacture of RGP lenses

23

Co-Continuous Phases

• Combination of

adequate oxygen

permeability and

adequate ionic or

hydraulic permeability

• Macromer + TRIS +

Solvent, one of which

is a hydrophilic

monomer

24

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Co-Continuous Phases

• Combination of adequate

oxygen permeability and

adequate ionic or

hydraulic permeability

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Monomers Used in

Silicone Hydrogel Manufacture

TRIS 26

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TRIS Modifications

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Macromers for

Silicone Hydrogels

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Comparison of Properties

of First Two Silicone Hydrogels

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Oxygen Permeability

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Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT

• 75 million people





About how many people worldwide wear contact lenses?

CL Wearers

• CL’s represent the most widely used biomaterial worldwide

• Worn by 130 million people

– 32 million in US

– 3.5 million in Canada

• 90% wear SCL

32

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Growth in SiHy Materials

Morgan et al, CL Spectrum 2016; 31(1): 28-33

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Current Issues with

Contact Lenses

• Protein and lipid adsorption

• Rigidity

• Surface friction

• COMFORT

34

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Intraocular Lens Implants

• 10 million IOLs are implanted annually in developed world and

developing countries

• Cataracts remains the leading cause of blindness worldwide

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The Lens

• The lens is situated behind the iris in a small bag-like structure called the lens capsule

• The lens itself is generally considered to be composed of three layers, appropriately titled the lens nucleus, the lens cortex and the lens epithelium

nuclear fibres cortical fibres

epithelial cells

ANTERIOR

POSTERIOR

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DISTANCE VISION

NEAR VISION

cornea

cornea

contracted

ciliary muscle

relaxed ciliary

muscle

low power

lens

high power

lens

38


• 1938

• 1949

• 1954

• 1967

• 1971

When was the first Intraocular Lens (IOL) surgery performed?

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Current Technologies to Treat

Cataracts

• Dr. Harold Ridley is credited with performing the first IOL operation on November 29, 1949

• He chose polymethyl methacrylate as the

his material choice as he observed it induced a negligible tissue response in the eye while working as a military surgeon

39

Current Materials and

Designs

• Hydrophobic acrylic materials

• Hydrophilic acrylic materials

• Silicones

• Square edged design

40

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In Bag Positioning

41

© 2008

Phakoemulsification

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Progression of IOL Materials

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44

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© 2008

Problems with

Current Technologies

• Approximately 30% of patients with artificial intraocular lenses (IOLs) develop posterior capsule opacification (PCO) within five years of surgery and must undergo a subsequent procedure

• Currently there are only 3 accommodative IOLs on the market and none effectively reduces the incidence of PCO

45

Lens Refilling

• During this technique, the capsular bag is evacuated through a small capsular opening to be then refilled with an elastic polymer capable of responding to adequate change in surface curvature according to the varying zonular tension.

46

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In Situ Curable Silicones –

Example

• Used ROP to create prepolymers using D4 and D4H

• Hexaethyldisiloxane used as a cap to control molecular weight

• Used hydrosilation to create polymerizable groups

• Cured by UV polymerization within 5 min

47

Drug Delivery to the Eye

• Eye disease is becoming a

greater burden on society

– Aging population

– Increased incidence of health

problems

– Increased incidence of

psychological problems

• New treatments developed

based on increased

understanding of biological

mechanisms

• Challenge is delivery to the

target tissue

48

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Opportunity

Pharmacological treatments for back of the eye diseases are a growth industry

Source: Braun Consulting group

49

Problem

Biological barriers limit treatment options

Both eye drops and systemic administration of drug fail to reach

target site at therapeutic concentrations

Recurring injection is the status quo

Painful, invasive, potentially dangerous, low patient compliance

Drug delivery devices are transforming the market

Controlled release devices are seen as the next step

Iluvien from Alimera Sciences

50

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• About five percent

• About ten percent

• About twenty percent

• About thirty percent

• About fifty percent

What percentage of the drug actually gets to the desired target in the eye with topical drops?

Topical Drops

• 90% of current market formulations for disease

management

– poor insertion technique in >50%

• over-spill

– poor compliance in 50%

– tear flow drainage

– diluted by blinking

– corneal diffusion resistance

• Substantial systemic absorption

• <5% of drug gets to target

52

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Mucoadhesive Materials to

Overcome Tear Drainage Problems

• Increase the residence time on

eye by increasing contact with

the ocular surface

• Mucin layer on the surface of

cornea shown to bind to a

variety of different natural and

synthetic materials

• Use this layer to facilitate

interactions with the corneal

layer over a prolonged period of

time

53

Mucoadhesive Micelles

• Patented drug delivery technology

• Provides superior treatment with fewer side effects

54

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Drug Delivery to Retina

• Intravitreal injections

– delivery of bolus which then diffuses out

• neovascular AMD – VEGF inhibitors

– ranibizumab (Lucentis®)

– bevacizumab (Avastin®) – 40x cheaper

• DME - triamcinolone acetonide

– Kenalog 40™; Triesence™; Trivaris™

• Intravitreal sustained release implants

55

S Lee & M Robinson

Ophthalmic Res 2009; 41: 124-135

Anatomic Locations for Drug

Delivery Systems

to Treat Retinal Disease

http://www.jirehdesign.com/

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Oculopeutic Polymers

Exploit:

• Acceptability of injections

• Thermogelling properties of

poly (N-isopropyl acrylamide)

Incorporate:

• Drug binding function

• Degradability

• Synthetic flexibility

57

Degradable NIPAAm-Based

Copolymers

6

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PEGco-monomers

[

[

10

[

[

9

MW: 526 Da OH pendent

MW: 475 Da CH3 pendent

[

[

20


PEGco-monomers

[

[

10

[

[

9



[

[

20


PEGco-monomers

[

[

10

[

[

9



[

[

20


PEG Incorporation, pN(N/A)PxDy

Polymer Composition LCST Gel Appearance at 37oC

pNNP5D4 75.8: 4.9: 14.1: 5.2 35.2 Soft, translucent

pNNP5D8 76.1: 4.8: 9.3: 9.8 27.7 Stiff, opaque

pNNP5D12 75.7: 4.5: 6.7: 13.1 18.7 Stiff, opaque

pNAP5D4 75.2: 4.9: 15.2: 4.7 36.9 Soft, translucent

pNAP5D8 76.1: 5.9: 8.8: 9.2 28.3 Stiff, Opaque


pNNP4D4 75.4: 4.7: 15.4: 4.5 39.1 No gel

pNNP4D8 75.9: 4.6: 10.2: 9.3 30.9 Stiff, Opaque

pNNP4D12 75.3: 4.4: 7.3: 13.0 20.9 Stiff, Opaque

pNAP4D4 76.0: 4.8: 13.1: 6.1 41.8 No gel



pNNP11D4 76.2: 4.7: 13.1: 6.0 - No gel

pNNP11D8 76.0: 5.0: 8.3: 10.7 - No gel

pNNP11D12 76.0: 5.3: 5.7: 13.0 23.6 Stiff, transparent

pNAP11D4 75.7: 5.1: 13.9: 5.3 - No gel

pNAP11D8 75.7: 4.8: 10.3: 9.2 - No gel

pNAP11D12 75.8: 4.8: 6.6: 12.8 26.8 Stiff, transparent

Optically Transparent, Non-

Shrinking, Degradable,

Thermoresponsive Copolymers

4°C 37°C

37°C PNN-P1100-D12

4oC 37oC

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Control of Release Kinetics

61

Summary

• New materials have the potential to treat many vision disorders

• New protein based treatments for eye disease require creative

delivery methods

• Mucoadhesion is key in the front of the eye

• Long term delivery is necessary to overcome back of the eye

limitations

62

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Acknowledgements

University Partners

Industry Partners

Government and Other Partners

Custom Contact Lenses

63

64







Dow Chemical



http://www.oce-ontario.org/Pages/Home.aspx

http://www.cnib.ca/en/Default.aspx

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2016 Material Science Series http://bit.ly/2016MaterialScienceSeries



Discover the material science innovations that makes life more comfortable!


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®









Polyamide Aerogels





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Dow Chemical



Be a featured fan on an upcoming webinar! Write to us @ [email protected]

68

How has ACS Webinars benefited you?

®

“The ACS Webinar on high performance elastomers is the

standard by which all other presentations should be

measured. The material presented was at an easy level

and suitable for a broad cross section of the target

audience. The speaker was very clear and knowledgeable

in the subject. He also kept the talk to 30 minutes, which

allowed for a good Q and A session.”

Richard Walton, Ph.D.

Research Associate

Goulston Technologies, Inc.

Quote in reference to: http://bit.ly/GoElastomers

7/6/2016

35

69


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youtube.com/acswebinars

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Chemical & Engineering News (C&EN) The preeminent weekly news source.

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ACS Webinars does not endorse any products or

services. The views expressed in this

presentation are those of the presenter and do

not necessarily reflect the views or policies of the

American Chemical Society.

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