Oxidized Avidin Tissue Anchoring via Periodate
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Solution Overview
Problem
Current cancer therapies using the avidin-biotin system face challenges with rapid clearance of avidin from the body and inefficient localization of therapeutic agents, leading to side effects and reduced efficacy due to non-specific distribution of anticancer agents.
Innovation Solution
Chemically oxidized avidin is developed to form reversible covalent bonds with tissue proteins, enhancing tissue permanence and biotinylated agent concentration in targeted areas, achieved through sodium periodate oxidation and protection with 4-hydroxyazobenzene-2'-carboxylic acid (HABA) to prevent tryptophan residue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If native avidin is used to bind biotinylated therapeutic agents, then high affinity binding is achieved, but rapid clearance from the body occurs resulting in short half-life
Solution Approach 1:
The patent applies parameter changes by chemically modifying avidin through PEGylation (attaching polyethylene glycol chains) and oxidation (adding aldehyde groups). These chemical modifications alter the physical and chemical parameters of avidin, specifically increasing its hydrodynamic radius and changing its surface properties, which prolongs plasma half-life while preserving biotin binding capability through the modified protein structure.
Solution Approach 2:
The patent creates composite structures by combining avidin with PEG chains and oxidized sugar moieties. The PEG-avidin conjugate forms a composite material where the PEG component provides extended circulation time by reducing renal filtration and immune recognition, while the avidin component maintains biotin binding function, achieving both prolonged duration and reliable binding.
2Quantity of substance
If avidin is administered systemically to target tumour tissue, then therapeutic agent delivery is attempted, but rapid clearance prevents sufficient accumulation in the target tissue
Solution Approach 1:
The patent modifies the pharmacokinetic parameters of avidin through PEGylation and oxidation, increasing its circulation half-life from minutes to hours. This parameter change allows the modified avidin to accumulate sufficiently in tumour tissue through the enhanced permeability and retention (EPR) effect, achieving the necessary quantity for effective therapy.
Solution Approach 2:
The patent employs preliminary action by administering PEG-oxidized avidin to the circulation system before introducing the biotinylated therapeutic agent. This preliminary administration allows the modified avidin to distribute and accumulate in target tissues in advance, creating a reservoir that will subsequently bind the therapeutic agent with high efficiency, ensuring sufficient quantity at the target site.
3Duration of action of moving object
If non-modified avidin is used for tissue binding, then rapid clearance occurs, but if PEG-ylated avidin is used to prolong half-life, then immunogenicity increases
Solution Approach 1:
The patent optimizes the PEGylation parameters, specifically controlling the degree of substitution and PEG chain length, to achieve a balance between prolonged half-life and reduced immunogenicity. The oxidation of sugar moieties further modifies the protein surface properties, creating a composite structure that evades immune recognition while maintaining extended circulation time.
4Manufacturing precision
If avidin is used to deliver anticancer agents, then rapid clearance leads to non-specific distribution, but prolonged residence is needed for selective tumour targeting
Solution Approach 1:
The patent changes the pharmacokinetic parameters of avidin through chemical modification, extending circulation time to allow sufficient accumulation in tumour tissue via the EPR effect. This prolonged circulation enables selective tumour targeting, as the modified avidin remains in circulation long enough to passively accumulate in the leaky tumour vasculature while clearing from normal tissues, achieving precise delivery.
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 oxidized avidin maintains high thermal stability and biotin binding capacity, achieving prolonged tissue residence and reduced toxicity by homogenous tissue binding, allowing for effective and selective delivery of anticancer agents.
Implementation Method 1
The present invention refers to an oxidized avidin, obtained by oxidation of the sugar moieties of the glycoprotein
Implementation Method 2
able to interact with tissues in vivo, through a reversible covalent chemical bond
Implementation Method 3
4-hydroxyazobenzene-2'-carboxylic acid (HABA) to prevent tryptophan residue damage
Data Source
AI summary
The present invention describes chemically modified avidins that have higher permanence in treated tissues compared to wild type avidin. Avidin oxidation is performed by periodate incubation in the presence of the low affinity ligand HABA which, occupying the biotin binding sites, prevents protein denaturation during the oxidation step. Periodate oxidation generates CHO groups from avidin mannose ring opening that, once injected, react with tissue NH2 residues to form stable Schiff's bases. The anchored avidins maintain the ability to bind biotinylated agents endowed of therapeutic activity, like radiolabeled biotins, stem cells and somatic cells, useful for brachytherapies like Intraoperative Avidination Radionuclide Therapy (IART®) or degenerative or genetic diseases.