Swellable Coating Prevents Stent Delamination

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Solution Overview

Problem

Conventional drug-eluting stents for ureteral strictures face issues with drug delamination during stent expansion, leading to inadequate drug delivery and recurrence of ureteral strictures, which complicates treatment and may result in renal function loss.

Innovation Solution

A stent assembly with a swellable coating that can swell up to 1500 times its volume, incorporating an active agent, is used to enhance localized drug delivery and prevent stricture recurrence, allowing for both quick and controlled release of the drug.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polymer coating is used to contain the drug on the stent, then the drug can be delivered to the desired location, but the coating is liable to delaminations during stent expansion

Engineering Contradiction:

Improvedrug delivery reliabilityVSAvoidcoating mechanical integrity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies composite materials by combining a polymer coating layer with a swellable coating layer. The polymer coating provides drug containment and delivery, while the swellable coating (comprising hydrophilic polymers like polyethylene glycol or hyaluronic acid) provides mechanical integrity and prevents delamination during stent expansion. This composite structure resolves the contradiction by integrating the advantages of both material types.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes parameter changes by employing a swellable coating that changes its physical state and volume in response to environmental stimuli such as moisture or pH variations. The coating swells upon contact with body fluids, transitioning from a compressed state during storage to an expanded state during use, which maintains mechanical integrity and prevents delamination while ensuring reliable drug delivery.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the drug-containing coating is applied on the stent, then the drug can be delivered to the ureteral wall, but the coating may delaminate during stent expansion using a balloon

Engineering Contradiction:

Improvedrug delivery to target locationVSAvoidcoating adhesion strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent uses composite materials by layering a polymer coating (for drug containment) with a swellable coating (for adhesion and mechanical strength). The swellable coating acts as a bonding agent that maintains strong adhesion during stent expansion, preventing delamination while ensuring the drug remains delivered to the target ureteral wall location.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The swellable coating serves as an intermediary layer between the polymer coating and the stent surface. This intermediary layer provides enhanced adhesion strength and prevents direct delamination during balloon expansion, while still allowing the polymer coating to effectively deliver the drug to the ureteral wall.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a mesh type stent is used to reduce hyperplastic reaction, then the stent can prevent stricture recurrence, but the mesh is difficult to remove without further traumatising the urothelium

Engineering Contradiction:

Improvestricture preventionVSAvoidureteral trauma during removal

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs a flexible shell approach by using a swellable coating that forms a soft, flexible layer on the stent surface. This flexible coating reduces trauma to the ureteral wall during stent removal compared to rigid mesh structures, while still providing effective stricture prevention through drug delivery and anti-hyperplastic properties.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent utilizes parameter changes by employing a swellable coating that changes its physical properties in response to environmental conditions. The coating swells upon contact with body fluids, becoming more flexible and compliant, which facilitates easier removal without traumatising the urothelium, while maintaining effective stricture prevention during the indwelling period.

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 swellable coating ensures effective drug delivery to the ureteral wall, inhibiting fibroblast proliferation and reducing stricture recurrence, while maintaining mechanical integrity during stent expansion and use.

Implementation Method 1

a swellable coating which is able to swell up to 1500 times its volume

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS11357651B2Stent assembly and method of preparing the stent assembly

Publication Date: 2022.06.14 SINGAPORE HEALTH SERVICES PTE LTD

AI summary

Various embodiments relate to a stent assembly comprising a stent; a swellable coating disposed on at least a portion of an exterior surface of the stent; optionally, a carrier dispersed in the swellable coating and/or disposed on at least a portion of an exterior surface of the stent; and an active agent comprised in at least one of the swellable coating or the carrier, if present. Use of the stent assembly as a ureteric stent, and method of preparing a stent assembly are also provided.