Tissue Growth-Inhibiting Coating for Pacemaker Retrieval
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Solution Overview
Problem
Chronically implanted medical devices, such as leadless cardiac pacemakers, face challenges in removal due to substantial tissue growth, which complicates extraction.
Innovation Solution
The use of a titanium outer surface with a tissue growth-inhibiting layer formed by covalently bonding polyethylene glycol molecules to titanium atoms, either through hydroxylation and subsequent bonding with hydroxyl-terminated polyethylene glycol molecules, or via plasma treatment to provide hydroxyl groups for bonding, reduces tissue growth and facilitates easier extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a leadless cardiac pacemaker is designed for long life chronic implantation, then device longevity and reliability are improved, but substantial tissue growth occurs around and over the device making removal difficult
Solution Approach 1:
The device surface is segmented into different functional zones: retrieval features with tissue growth-inhibiting coatings for easy removal, fixation features with tissue-engaging structures for secure anchoring, and electrical leadless pacemaker components for cardiac function. This segmentation allows different parts of the device to have opposing tissue interaction characteristics.
Solution Approach 2:
Different portions of the device have different surface properties: the retrieval feature has a tissue growth-inhibiting coating (such as PEG, diamond-like carbon, or titanium nitride) to prevent tissue adhesion, while the fixation feature has a tissue-engaging structure (such as hooks, tines, or barbs) to promote tissue integration and secure anchoring. This local differentiation resolves the contradiction between easy removal and secure fixation.
2Ease of operation
If tissue growth-inhibiting coatings are applied to the entire device surface, then tissue growth is reduced and device retrieval is easier, but fixation capability and electrical function are compromised
Solution Approach 1:
The device surface is divided into distinct functional zones: retrieval features receive tissue growth-inhibiting coatings to facilitate removal, while fixation features maintain tissue-engaging structures for secure anchoring, and electrical components preserve their conductive properties for cardiac pacing function.
Solution Approach 2:
Tissue growth-inhibiting coatings are applied selectively only to retrieval features rather than the entire device surface. This localized application ensures that retrieval is facilitated while fixation capability and electrical function in other areas remain uncompromised.
3Strength
If conventional titanium surfaces are used without special coatings, then device structure and electrical properties are maintained, but extensive tissue growth occurs making extraction difficult
Solution Approach 1:
Tissue growth-inhibiting coatings (such as PEG, diamond-like carbon, or titanium nitride) are applied selectively to retrieval features while preserving the conventional titanium surface structure elsewhere. This localized coating approach maintains overall structural integrity while facilitating extraction at critical points.
Solution Approach 2:
The device combines conventional titanium structural materials with advanced tissue growth-inhibiting coating materials on retrieval features. This composite approach integrates the mechanical strength of titanium with the anti-fouling properties of specialized coatings, resolving the contradiction between structural integrity and ease of extraction.
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 effectively inhibits tissue growth on the medical device, reducing resistance to removal and ensuring easier retrieval of chronically implanted devices without compromising their electrical properties.
Implementation Method 1
A tissue growth-inhibiting layer may extend over the titanium outer surface and may, for example, include a plurality of polyethylene glycol molecules, at least some of which are covalently bonded via an ether bond to one of the plurality of titanium atoms
Implementation Method 2
subjecting the titanium outer surface to a plasma treatment to provide hydroxyl groups on the titanium outer surface, the hydroxyl groups covalently bonded to titanium atoms within the titanium outer surface
Implementation Method 3
the tissue growth-inhibiting layer is formed by hydroxylating at least some of the plurality of titanium atoms and covalently bonding a plurality of hydroxyl-terminated polyethylene glycol molecules to the hydroxylated titanium atoms
Data Source
AI summary
An implantable medical device (IMD) may include an outer housing having a titanium outer surface, the titanium outer surface including a plurality of titanium atoms. A tissue growth-inhibiting layer may extend over the titanium outer surface. In some cases, the tissue growth-inhibiting layer may include a plurality of polyethylene glycol molecules, at least some of the plurality of polyethylene glycol molecules covalently bonded via an ether bond to one of the plurality of titanium atoms.