Acid-Responsive Polymer-Lipid Nanoparticles for Endosomal RNA Release
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Solution Overview
Problem
Current lipid nanoparticle (LNP) delivery systems for RNA therapeutics are inefficient, with only a small percentage of RNA escaping endosomes and reaching the cytosol, leading to increased dosages and adverse effects such as immunogenicity and toxicity.
Innovation Solution
Development of acid-responsive poly(lactic acid)-block-poly(carboxybetaine) zwitterionic derivatives that transition from cationic to neutral at endosomal pH, facilitating RNA release from lipid nanoparticles (LNPs) using hemiacetal esters as acid-labile protecting groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lipid nanoparticles are used for RNA delivery, then RNA can be delivered to cells, but delivery efficiency is low and only a small percentage of RNA reaches the cytosol
Solution Approach 1:
The patent applies parameter changes by utilizing pH transition as the key parameter. The polymer remains cationic at physiological pH (7.4) for stable RNA complexation but transitions to neutral at endosomal pH (5.0-6.0) to trigger RNA release. This pH-dependent parameter change enables controlled RNA delivery without requiring high positive charge throughout the entire delivery process.
Solution Approach 2:
The patent implements dynamics through the dynamic charge transition of the polymer. The polymer's charge state is not fixed but dynamically changes in response to pH conditions: cationic in the bloodstream and cytosol for stability, and neutral within the acidic endosome for release. This dynamic behavior allows the system to adapt its properties to different physiological environments.
2Productivity
If higher dosage is used to compensate for low delivery efficiency, then more RNA reaches the cytosol, but adverse effects such as immunogenicity and toxicity increase
Solution Approach 1:
The patent uses parameter changes to reduce harmful effects by transitioning the polymer charge from cationic to neutral at the endosomal pH. This eliminates the need for sustained high positive charge, thereby reducing immunogenicity and cytotoxicity associated with cationic lipids while maintaining effective RNA delivery through pH-triggered release.
Solution Approach 2:
The patent converts the harmful acidic environment of the endosome into a beneficial trigger for RNA release. The low pH that traditionally causes RNA degradation and trapping is instead utilized to trigger the charge transition and facilitate RNA dissociation from the LNP, turning a harmful condition into a useful release mechanism.
3Productivity
If polymeric nanocarriers are used to improve RNA delivery, then RNA can be protected and delivered, but high positive charge required for cellular entry can disrupt cell membranes and induce cytotoxicity
Solution Approach 1:
The patent applies dynamics through the time-dependent and pH-dependent charge transition of the polymer. The polymer is cationic only transiently during circulation and cellular uptake, then transitions to neutral after endosomal internalization. This dynamic charge modulation allows the system to achieve cellular entry without sustained cytotoxic exposure to high positive charge.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the pH difference between extracellular environment (pH 7.4) and endosomal compartment (pH 5.0-6.0). The polymer's charge state changes in response to this parameter change, being cationic for cellular uptake and neutral for cytosolic release, thereby achieving delivery without sustained cytotoxicity.
4Productivity
If RNA is released from carrier in endosome, then RNA can be delivered to cytosol, but most polyplexes fuse poorly with endosomal membrane and RNA remains trapped
Solution Approach 1:
The patent applies parameter changes by using pH transition to trigger both RNA dissociation from the polymer and endosomal membrane disruption. The charge neutralization at endosomal pH causes RNA release, and the same pH change triggers the polymer to disrupt the endosomal membrane, enabling RNA escape to the cytosol without requiring separate fusion mechanisms.
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 polymers enhance RNA delivery efficiency by up to 5.4-fold for siRNA and 4-fold for mRNA, reducing cytotoxicity and improving endosomal escape, as demonstrated in clinically approved LNP formulations like Onpattro, Pfizer, and Moderna.
Implementation Method 1
protected the pendant carboxylate groups with hemiacetal esters... following cleavage at endosomal pH
Data Source
AI summary
Lipid nanoparticles (LNPs) are widely used for RNA delivery but are limited by inefficient RNA release following endosomal escape. Disclosed herein are hybrid polymer-lipid nanoparticles (PLNPs) incorporating acid-responsive poly(lactic acid)-block-poly(carboxybetaine) zwitterionic polymers to enhance RNA delivery efficiency. The polymers are cationic at physiological pH to enable RNA complexation but become neutral at endosomal pH, reducing RNA binding affinity and promoting release. These polymers were integrated into clinically approved LNP formulations to form PLNPs. The resulting PLNPs showed up to a 5.4-fold decrease in siRNA IC50 values and a 4-fold increase in mRNA transfection across multiple cell lines. Enhanced cytosolic RNA levels were confirmed via confocal microscopy, with uptake and endosomal escape comparable to standard LNPs. The improvement in transfection efficiency was lost when acid-inert polymers were used, confirming the role of the acid-responsive polymers. This approach provides a versatile platform to improve RNA delivery from existing LNP systems.