Biodegradable Tissue Marker with Drug-Refillable Coating
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Solution Overview
Problem
Conventional tissue markers face challenges such as migration, visualization difficulties, irritation, discomfort, and degradation over time, making it hard to accurately locate the site of tissue resection post-biopsy or lumpectomy procedures.
Innovation Solution
A biocompatible and biodegradable tissue marker is developed, comprising a detectable marker encapsulated within a biodegradable polymer layer and a coating layer that includes hydrophobic materials and therapeutic agents, designed for controlled release and to prevent migration, with a hydrophobic coating to reduce friction and prevent premature swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tissue marker is implanted to mark the resection site, then the location can be precisely identified, but the marker may migrate from the target site
Solution Approach 1:
The tissue marker employs a nested structure where a permanent detectable marker (inner core) is encapsulated within a biodegradable polymer layer (intermediate layer), which is further surrounded by a coating layer (outer layer). This multi-layer nesting ensures the permanent marker remains securely positioned at the resection site while the biodegradable layers provide temporary support and controlled degradation, preventing migration during the healing process.
Solution Approach 2:
The tissue marker utilizes composite materials combining a permanent detectable marker material (such as metal or glass) with biodegradable polymers (such as PLGA, PGA, or PLA). This composite structure leverages the permanent marker's stability for accurate localization and the biodegradable polymer's controlled degradation to provide temporary structural support and therapeutic functionality, resolving the contradiction between permanent positioning and temporary biocompatibility.
2Measurement precision
If the tissue marker remains permanent for long-term detection, then localization is maintained, but the marker may cause irritation or discomfort to the implantee
Solution Approach 1:
The invention extracts the permanent detectable marker from direct contact with surrounding tissues by encapsulating it within a biodegradable polymer layer. This intermediate layer acts as a buffer, isolating the permanent marker material from direct tissue interaction, thereby reducing irritation and discomfort while preserving the marker's detection capabilities through imaging modalities.
Solution Approach 2:
The tissue marker employs local quality differentiation where the permanent detectable marker provides localized detection capability at the resection site, while the surrounding biodegradable polymer layers provide localized biocompatibility and controlled degradation. This spatial differentiation of material properties allows permanent detection functionality without permanent tissue exposure to potentially irritating materials.
3Object-affected harmful factors
If the tissue marker degrades over time, then biocompatibility improves, but localization becomes difficult
Solution Approach 1:
The tissue marker is segmented into distinct functional layers: a permanent detectable marker core for long-term localization and biodegradable polymer layers for temporary structural support and therapeutic delivery. This segmentation allows the permanent core to maintain localization accuracy indefinitely while the biodegradable segments provide time-limited biocompatibility and therapeutic functionality, resolving the contradiction between permanent detection and temporary biocompatibility.
Solution Approach 2:
Instead of using a completely permanent marker that causes irritation, the invention inverts the approach by using a permanent detectable core surrounded by degradable protective layers. The degradation occurs outward from the permanent core, allowing the permanent localization element to persist while the biocompatible layers gradually dissolve, reversing the conventional approach of using entirely degradable markers.
4Ease of operation
If the tissue marker is delivered through a delivery device, then implantation is facilitated, but surface interactions may frustrate delivery
Solution Approach 1:
The coating layer's physical and chemical parameters are specifically designed to change during delivery and implantation. The coating provides a low-friction surface for smooth delivery through the catheter, then undergoes controlled degradation or transformation upon implantation to provide structural support and therapeutic functionality. This parameter change optimizes both delivery ease and implantation reliability.
Solution Approach 2:
The coating layer acts as an intermediary between the permanent detectable marker and the delivery device, as well as between the marker and the surrounding tissue. During delivery, the coating mediates low-friction interaction with the catheter; after implantation, it mediates controlled interaction with surrounding tissues, enabling both easy delivery and reliable implantation.
5Power
If therapeutic agents are released immediately, then treatment effectiveness is enhanced, but the treatment duration may be insufficient for long-term therapy
Solution Approach 1:
The biodegradable polymer layers are designed to degrade periodically over time, releasing therapeutic agents in a controlled, periodic manner. This periodic degradation provides sustained treatment delivery, transitioning from immediate high-concentration release to extended lower-concentration release, thereby maintaining both treatment effectiveness and extended duration of action.
Solution Approach 2:
The tissue marker employs dynamic therapeutic release where the degradation rate and drug release kinetics are tuned to match the healing process. The system transitions from a static, fixed-dose marker to a dynamic system that adapts its therapeutic delivery over time, providing high initial effectiveness followed by sustained maintenance dosing as the biodegradable layers gradually degrade.
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 tissue marker provides precise localization of the resection site, reduces discomfort, and ensures controlled release of therapeutic agents, minimizing migration and irritation, while the biodegradable components facilitate healing and tissue regeneration.
Implementation Method 1
the coating layer and/or the encapsulation layer degrade over time within the subject as the site of placement within the subject heals and the subject's tissue regenerates and refills the space
Implementation Method 2
a coating layer that includes hydrophobic materials and therapeutic agents, designed for controlled release and to prevent migration, with a hydrophobic coating to reduce friction and prevent premature swelling
Implementation Method 3
Each of the distinct structures includes an outer shell designed to open upon the application of focused ultrasound and a therapeutic agent within the outer shell
Data Source
AI summary
A tissue marker is provided having a permanent portion and a biodegradable portion. The permanent portion includes a material detectable by an imaging modality. The biodegradable portion surrounds the permanent portion. The biodegradable portion includes a polymer body, a coating, and a plurality of distinct structures dispersed in the polymer body. The coating covers an outer surface of the polymer body. Each of the distinct structures include an outer shell designed to open upon the application of focused ultrasound to release a therapeutic agent within the outer shell into the polymer body. Therapeutic agents may be introduced into the biodegradable portion of the tissue marker after a period of time after introduction of the tissue marker into the tissue. In addition, methods of fabricating a three-layer tissue marker are provided.