Diffusion-Controlled Drug-Eluting Stent Coating

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Solution Overview

Problem

Conventional drug-eluting stents experience issues with partial bolus-like release of active ingredients, leading to local overdosing and inadequate pharmacokinetics, which increases the risk of complications such as restenosis, due to their thick polymer coatings.

Innovation Solution

A medical implant with a structure comprising a biodegradable or permanent base body coated with a primer layer, an active ingredient layer, and a diffusion-controlling layer, where the diffusion-controlling layer regulates the release of active ingredients, reducing the risk of bolus-like release and minimizing the stent's wall thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick polymer coating is used to contain active ingredients, then the active ingredient release can be maintained, but bolus-like release occurs leading to local overdosing and inadequate pharmacokinetics

Engineering Contradiction:

Improvepharmacokinetics controlVSAvoidlocal overdosing

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The coating is divided into multiple functional layers: a primer layer for adhesion, an active ingredient-containing polymer layer, and a diffusion-controlling top layer. This segmentation allows each layer to perform its specific function, with the top layer regulating diffusion to prevent bolus release while the primer ensures proper bonding to the stent surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent modifies the coating structure by introducing a diffusion-controlling layer with specific thickness parameters (5-20 μm) and composition characteristics. This parameter change transforms the release profile from bolus-like to controlled diffusion, achieving adequate pharmacokinetics without local overdosing.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If a thick polymer coating is applied to the stent, then active ingredient delivery is achieved, but the stent wall thickness increases approximately doubling the original thickness

Engineering Contradiction:

Improveactive ingredient capacityVSAvoidstent wall thickness

Core Design Contradiction:

Quantity of substanceVSLength of stationary object

Solution Approach 1:

The patent employs thin film technology with the diffusion-controlling layer applied at a thickness of only 5-20 μm. This thin film approach maintains adequate active ingredient delivery capacity while minimizing the increase in stent wall thickness, avoiding the approximation doubling effect of conventional thick coatings.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The coating system uses composite material structure combining a polymer matrix with embedded active ingredients and a diffusion-controlling top layer. This composite approach optimizes the balance between active ingredient capacity and coating thickness, achieving effective drug delivery with minimal wall thickness increase.

Inventive Principle:

Principle #40Composite materials

3Quantity of substance

If conventional coating methods are used, then active ingredients can be delivered, but the release pattern is bolus-like rather than controlled

Engineering Contradiction:

Improveactive ingredient deliveryVSAvoidrelease pattern control

Core Design Contradiction:

Quantity of substanceVSDuration of action of moving object

Solution Approach 1:

The diffusion-controlling layer acts as an intermediary between the active ingredient reservoir and the external environment. This intermediate layer regulates the diffusion process, transforming the release pattern from bolus-like to controlled and sustained, thereby extending the duration of action and achieving adequate pharmacokinetics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

By changing the physical and chemical parameters of the top layer (composition, thickness, cross-linking density), the patent controls the diffusion rate of active ingredients. This parameter modification transforms the release kinetics from rapid bolus release to controlled sustained release, improving the duration and pattern of active ingredient delivery.

Inventive Principle:

Principle #35Parameter changes

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 allows for controlled and optimized release of active ingredients, reducing the risk of restenosis and improving physiological and physicochemical properties, while maintaining the original mechanical functions of the stent, such as dilatability and flexibility.

Implementation Method 1

a diffusion-controlling layer (4) applied to at least a portion of the active ingredient layer (3) wherein diffusion of the active ingredients of the active ingredient layer (3) is controlled

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS8257729B2Implants with membrane diffusion-controlled release of active ingredient

Publication Date: 2012.09.04 BIOTRONIK AG

AI summary

An implant for implantation in a human or animal body having a structure comprising a) an implant base body; b) a primer layer which is partially or completely applied to the surface of the implant; c) an active ingredient layer consisting of one, two, three or more active ingredients applied entirely or partially to the surface of the primer layer; and d) a diffusion-controlling layer which is applied partially or entirely to the active ingredient layer, and optionally to the primer layer, wherein diffusion of the active ingredients of the active ingredient layer is controlled. Also disclosed is a manufacturing method for an implant.