Selective Delivery Molecules for Targeted Cancer Imaging
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Solution Overview
Problem
Selective delivery molecules face challenges with rapid pharmacokinetic clearance, broad distribution, and non-specific uptake in non-target tissues, leading to short plasma half-life and inefficient targeting of cancerous tissues for imaging agents.
Innovation Solution
Development of selective delivery molecules with a cleavable linker and a macromolecular carrier, such as PEG polymers, that allow targeted delivery of imaging agents to cancerous tissues by cleaving in specific pathological environments, enhancing accumulation and bio-distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If selective delivery molecules are used for targeted delivery, then imaging agents can be delivered to cancerous tissues, but the molecules face rapid pharmacokinetic clearance and broad distribution leading to short plasma half-life
Solution Approach 1:
The selective delivery molecule is divided into separate components: a macromolecular carrier (e.g., PEG polymer) that provides long circulation half-life, a targeting ligand that binds to cancerous tissue, and a cleavable linker that connects them. The carrier and ligand are separated by the cleavable linker, allowing the carrier to circulate long without being taken up by cells, while the ligand remains available for targeting. Upon reaching the target, the linker is cleaved to release the ligand for specific binding.
Solution Approach 2:
The cleavable linker serves as an intermediary between the macromolecular carrier and the targeting ligand. It maintains the connection during circulation, allowing the carrier to protect the ligand from premature clearance, while enabling specific release at the target site through enzymatic or chemical cleavage. This intermediary mechanism resolves the contradiction by providing both long circulation time and effective targeting.
2Measurement precision
If selective delivery molecules are used, then imaging agents can be delivered to target tissues, but there is non-specific uptake in non-target tissues leading to reduced contrast
Solution Approach 1:
By segmenting the delivery system into a non-uptaking macromolecular carrier and a cell-binding ligand separated by a cleavable linker, the system prevents non-specific uptake in non-target tissues. The carrier circulates without being internalized by non-target cells, maintaining low background signal. Only after linker cleavage at the target site does the ligand become available for specific binding, ensuring high contrast imaging.
Solution Approach 2:
The system exploits parameter changes in the biochemical environment between circulation and target sites. The cleavable linker is designed to be stable under circulation conditions but undergoes specific enzymatic or chemical cleavage in the pathological microenvironment of cancerous tissues (e.g., higher protease activity, specific pH). This parameter change triggers the transition from a circulating complex to a bound complex only at the target site, eliminating non-specific uptake.
3Duration of action of moving object
If the molecule circulates longer in vivo, then more imaging agent accumulates in target tissues, but the molecule may be cleared by the kidneys or liver
Solution Approach 1:
The macromolecular carrier is designed with specific physical parameters (molecular weight, hydrodynamic radius, surface charge) that place it below the renal filtration threshold but large enough to avoid rapid hepatic clearance. By carefully controlling these parameters, the carrier achieves extended circulation half-life. The PEGylation further modifies these parameters to reduce opsonization and reticuloendothelial system uptake, maximizing circulation time while minimizing clearance.
Data Source
AI summary
Disclosed herein is a selective delivery molecule comprising: (a) an acidic sequence (portion A) which is effective to inhibit or prevent the uptake into cells or tissue retention, (b) a molecular transport or tissue retention sequence (portion B), and (c) a linker between portion A and portion B, and (d) cargo moieties (portion DA and DB).