Anionic Silicone Hydrogel Contact Lenses With Homogeneous Charge Density

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Solution Overview

Problem

Existing silicone hydrogel contact lenses face issues with hydrolytic instability, increased moduli upon exposure to water and heat, and undesirable uptake of positively charged components like PQ1 from cleaning solutions, while maintaining low oxygen permeability and high lysozyme uptake.

Innovation Solution

The development of anionic silicone hydrogel polymers with controlled spatial density and concentration of anionic charges, achieved through the use of anionic statistical copolymers that associate with the lens via entanglement or association, ensuring homogeneous distribution of anionic charges for increased lysozyme uptake and reduced uptake of polycationic components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If anionic components are added to silicone hydrogels to increase lysozyme uptake, then lysozyme uptake increases, but uptake of polycationic components like PQ1 also increases and hydrolytic stability decreases

Engineering Contradiction:

Improvelysozyme uptakeVSAvoidhydrolytic stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by creating distinct regions within the contact lens with different charge densities. The lens comprises a bulk region with lower anionic charge density and a surface region with higher anionic charge density. This gradient structure allows the surface to attract and retain lysozyme effectively while the bulk maintains hydrolytic stability, resolving the contradiction between increased lysozyme uptake and maintained stability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of charge density distribution within the lens structure. By controlling the spatial distribution of anionic charges to create a gradient from bulk to surface, the invention optimizes both lysozyme uptake (enhanced at surface) and hydrolytic stability (maintained in bulk), transforming a uniform structure into a functionally differentiated one.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If anionic components are added to silicone hydrogels to increase lysozyme uptake, then lysozyme uptake increases, but the modulus increases when exposed to water and heat

Engineering Contradiction:

Improvelysozyme uptakeVSAvoidmodulus

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent creates local quality differentiation by concentrating anionic charges at the lens surface while maintaining a lower charge density in the bulk. This allows the surface to provide high lysozyme uptake capability while the bulk maintains appropriate mechanical properties and modulus, preventing excessive stiffening when exposed to water and heat.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If anionic components are added to silicone hydrogels, then lysozyme uptake increases, but contact angles become higher than desired

Engineering Contradiction:

Improvelysozyme uptakeVSAvoidcontact angle

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The patent applies local quality by restricting high anionic charge density to the lens surface region while maintaining lower charge density in the bulk. This surface concentration enhances lysozyme uptake through electrostatic attraction, while the overall balanced composition prevents excessive increase in contact angle, maintaining desirable wettability.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution results in contact lenses with improved hydrolytic stability, reduced uptake of polycationic components, and enhanced lysozyme uptake, maintaining desirable oxygen permeability and comfort levels.

Implementation Method 1

anionic statistical copolymer associates with the lens either through entanglement, association or a combination thereof

Methodology Applied

Scientific EffectEntanglement:

Implementation Method 2

anionic statistical copolymer associates with the lens either through entanglement, association or a combination thereof

Methodology Applied

Scientific EffectAssociation:

Implementation Method 3

desirable tear and polycationic ophthalmic solution component uptake profiles

Methodology Applied

Scientific EffectElectrostatic attraction: Electrostatics

Implementation Method 4

reduced uptake of polycationic components

Methodology Applied

Scientific EffectElectrostatic repulsion: Ion Repulsion/Attraction

Data Source

PatentEP3581973B1Medical devices having homogeneous charge density and methods for making same

Publication Date: 2026.01.07 JOHNSON & JOHNSON VISION CARE INC

AI summary

The present invention relates to ionic silicone hydrogel polymers displaying improved lysozyme uptake, low contact angle and reduced water soluble polymeric ammonium salt uptake.