pH-Responsive Polyvinyl Ester Polymers for Nucleic Acid Delivery
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Solution Overview
Problem
Current methods for delivering polynucleotides and other cell membrane-impermeable compounds in vivo face challenges due to the complex cell membrane, with existing transfection reagents causing toxicity and poor targeting, and requiring large nucleic acid doses and inefficient delivery.
Innovation Solution
Development of amphipathic cationic poly(vinyl ester) random copolymers that are reversibly modified with masking agents to reduce membrane activity and improve biodistribution, allowing for targeted and efficient delivery of polynucleotides by forming stable complexes with RNA interference polynucleotides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cationic transfection reagents are used to facilitate nucleic acid delivery, then delivery efficiency is improved, but in vivo toxicity increases
Solution Approach 1:
The patent employs pH-responsive polymers that dynamically change their conformation and charge state in response to pH gradients. The polymers remain collapsed and neutral at physiological pH (7.4) to minimize toxicity, then expand and become cationic in acidic endosomal environments (pH 5.0-6.5) to facilitate membrane disruption and nucleic acid delivery, thus resolving the contradiction between delivery efficiency and toxicity
Solution Approach 2:
The invention utilizes parameter changes in polymer properties based on environmental conditions. The polymers exhibit pH-dependent solubility, charge, and conformational changes that allow them to transition from a low-toxicity state in circulation to a high-delivery-efficiency state within cells, effectively balancing delivery performance with safety
2Strength
If cationic polymers are used for transfection, then membrane fusion and destabilization are enhanced, but serum stability deteriorates
Solution Approach 1:
The pH-responsive polymers dynamically switch between serum-stable and membrane-active states. At physiological pH, they maintain a compact, neutral conformation that resists serum protein binding and aggregation. Upon endosomal acidification, they transition to an extended, cationic conformation that actively destabilizes membranes, thus achieving both serum stability and membrane disruption capability
Solution Approach 2:
The polymers exhibit periodic functional behavior corresponding to the pH cycle experienced during cellular uptake: stable in neutral pH (circulation and initial cellular contact), then becoming active in acidic pH (endosomal escape), effectively using the periodic pH changes in the cellular environment to switch between stability and activity
3Productivity
If membrane active polymers are used for delivery, then cellular uptake is improved, but biodistribution and targeting are reduced
Solution Approach 1:
The patent incorporates targeting ligands (such as antibodies, peptides, or carbohydrates) conjugated to the pH-responsive polymer backbone. This creates a heterogeneous structure where the polymer core provides membrane disruption activity while the attached ligands provide site-specific targeting, allowing different parts of the conjugate to perform different functions: biodistribution control via ligand-receptor binding and cellular uptake via polymer membrane interaction
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 amphipathic poly(vinyl ester) random copolymers enable efficient and targeted delivery of polynucleotides in vivo, reducing toxicity and improving bioavailability, while maintaining membrane activity for cellular uptake, thus overcoming the limitations of existing delivery methods.
Implementation Method 1
The positive charge of in vitro transfection reagents facilitates association with nucleic acid via charge-charge (electrostatic) interactions thus forming the nucleic acid/transfection reagent complex.
Implementation Method 2
demonstrated a means to reversibly regulate membrane disruptive activity of a membrane active polyamine by reversible conversion of primary amines to pairs of carboxyl groups (β carboxyl and γ carboxyl of 2-propionic-3-methylmaleic anhydride)
Data Source
AI summary
The present invention is directed membrane active poly(vinyl ester) polymers and compositions for targeted delivery of RNA interference (RNAi) polynucleotides to cells in vivo. RNAi polynucleotides are conjugated to the poly(vinyl ester) polymers and the polymers are reversibly modified to enable in vivo targeted delivery. Membrane activity of the poly(vinyl ester) provides for movement of the RNAi polynucleotides from outside the cell to inside the cell. Reversible modification provides physiological responsiveness.