Automated Cationic Oligonucleotide Synthesis via Phosphoramidite Segmentation
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Solution Overview
Problem
Current methods for synthesizing cationic oligonucleotides are not routine, particularly for stepwise automated synthesis, and face challenges with solubility, purification, and characterization, especially in water, which hinders their application in molecular biology and therapeutics.
Innovation Solution
The development of an online, computer-driven synthesis method using an oligonucleotide synthesizer with activated and protected oligocationic derivatives to create mixed oligonucleotide-oligocation molecules via automated phosphoramidite chemistry, allowing for high-yield production of cationic oligonucleotides with specific sequences and lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stepwise automated synthesis of oligonucleotide-cationic peptide conjugates is attempted, then sequence selectivity and hybridization specificity are improved, but the synthesis process is not yet routine and lacks ease of manufacture
Solution Approach 1:
The synthesis process is segmented into modular phosphoramidite building blocks, each containing specific cationic amino acid sequences. This allows automated synthesizers to assemble complex oligonucleotide-cationic conjugates through standardized coupling reactions, making the process routine while maintaining sequence precision
Solution Approach 2:
Phosphoramidite intermediaries are used as protected precursors that enable stepwise automated synthesis. These intermediaries contain cationic amino acid sequences in protected forms that can be reliably coupled by automated synthesizers, then deprotected afterward to yield the final conjugates with high sequence selectivity
2Productivity
If conjugation chemistry between preformed large blocks is used, then synthesis speed is improved, but solubility and purification problems arise in water
Solution Approach 1:
Instead of conjugating large preformed blocks, the invention segments the synthesis into smaller phosphoramidite units that are coupled stepwise. This segmentation maintains solubility throughout synthesis and enables straightforward purification at each stage, avoiding the intractable problems of large block conjugation
Solution Approach 2:
The invention changes the physical-chemical parameters of the synthesis by using protected phosphoramidite intermediaries in organic solvents during coupling, then transitioning to aqueous conditions for final deprotection and purification. This parameter change maintains solubility and simplifies purification while preserving synthesis efficiency
3Reliability
If cationic groups are added to oligonucleotide structure, then cell membrane crossing ability is improved, but hybridization specificity and enzyme activity may be affected
Solution Approach 1:
Cationic amino acid sequences are placed locally at specific positions within the oligonucleotide structure rather than uniformly distributed. This local placement optimizes cell membrane interaction while preserving the hybridization specificity of the nucleotide sequence, as the cationic regions are positioned to interact with membranes without interfering with base pairing
Solution Approach 2:
The invention uses natural amino acid sequences (such as oligoarginine and oligolysine) that have been proven to facilitate cellular uptake. By copying these naturally occurring cationic sequences, the invention achieves reliable cell permeation while maintaining compatibility with biological systems and preserving oligonucleotide function
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
This approach enables the production of cationic oligonucleotides that form stable complexes with complementary sequences, enhance cell permeation, and maintain sequence selectivity, making them suitable for molecular biology, diagnostics, and therapeutic applications such as antisense therapy and gene correction.
Implementation Method 1
automated phosphoramidite chemistry
Implementation Method 2
hybridization to a complementary sequence borne by another polyanionic nucleic acid
Implementation Method 3
Simple electrostatic considerations imply that hybridization energy and cell binding could benefit from the addition of cationic groups to the oligonucleotide structure
Implementation Method 4
As drug candidates, they must also be capable of crossing the anionic cell membrane
Data Source
AI summary
The invention relates to oligonucleotide-oligocation molecules AiBjH that can be synthetized via automated phosphoramidite chemistry having oligonucleotides moieties Ai and oligocations moieties Bj, wherein .Ai is an i-mer oligonucleotide residue, with i=5 to 50, where nucleotide A is an oligomer with naturally or non naturally occurring nucleobases and/or pentafuranosyl groups and/or native phosphodiester bonds, for example selected from the group comprising deoxyribo, ribo, locked (LNA) nucleotides as well as their chemical modifications or substitutions such as phosphorothioate, 2′-fluoro, 2′-O-alkyl, or a marker group such as a fluorescent agent, .Bj is a j-mer organic oligocation moiety, with j=1 to 50, where B is selected from the group comprising .—HPO3—R1—(X—R2n)n1—X—R3—O—, where R1, R2n and R3, identical or different, are lower alkylene, X is NH or NC(NH2)2, n varies from 1 to 5 and n1=2 to 20, .—HPO3—R4—CH(R5X1)—R6—O—, where R4 is lower alkylene, R5 and R6, identical or different, are lower alkylene and X1 is putrescine, spermidine or spermine residue, .—HPO3—R7-(aa)n2-R8—O—, where R7 is lower alkylene and R8 is lower alkylene, serine, a natural aminoalcohol, (aa)n2 is a peptide containing natural aminoacids with cationic side chains, such as Arginine, Lysine, Ornithine, -Histidine, Diaminopropionic acid and n2=2 to 20.