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CPG architecture for oligo synthesis
Controlled pore glass is one of the most widely used solid supports for solid-phase oligonucleotide synthesis. It consists of high-silica glass particles containing a carefully controlled pore size distribution that allows reagents to access growing oligonucleotide chains during synthesis.
Each particle contains a network of internal pores where oligonucleotide assembly occurs. The combination of pore architecture, particle size and surface chemistry influences synthesis efficiency, loading capacity, mass transfer and final product quality.
The rigid matrix structure of CPG makes it particularly well suited to demanding synthesis applications, including therapeutic oligonucleotides and large-scale manufacturing processes.
Selecting the right pore size
Selecting the correct pore size is one of the most important decisions when designing an oligonucleotide synthesis process.
Pore Size | Typical Considerations |
|---|---|
500 Å | Commonly used for shorter oligonucleotides and siRNA synthesis where higher surface area and loading capacity are desirable |
1000 Å | Suitable for intermediate-length oligonucleotides requiring a balance between accessibility and loading |
2000-3000 Å | Often used for long oligonucleotides where greater pore volume improves reagent access and reduces steric restriction |
As oligonucleotide length increases, larger pore sizes may help maintain synthesis efficiency by reducing crowding within the support structure.
Balancing loading and yield
Loading capacity determines how many reactive synthesis sites are available on a support. While higher loading can increase theoretical output, excessive surface density may reduce synthesis efficiency.
Balancing loading relative to available surface area is important because overcrowding can increase early coupling failures and reduce full-length product yield. Optimised loading strategies can improve productivity while maintaining product quality and impurity profiles.
For therapeutic manufacturing, loading capacity is often evaluated alongside pore size, support chemistry and synthesis scale to maximise overall process performance.
CPG, polystyrene and universal supports
Support Type | Characteristics |
|---|---|
Controlled Pore Glass (CPG) | Rigid matrix with controlled pore architecture and broad use across oligonucleotide synthesis applications |
Polystyrene Resin | Alternative solid support platform with different swelling and synthesis characteristics |
Universal Supports | Provide flexibility across multiple sequence types and synthesis workflows, including universal support platforms such as UnyLinker® Polystyrene |
The most appropriate support depends on sequence length, synthesis chemistry, modification requirements, purification strategy, and manufacturing objectives.
Phosphoramidite chemistry explained
Although the terms are sometimes confused, phosphoramidites and phosphoramidates perform different roles in oligonucleotide chemistry.
Phosphoramidites are reactive synthesis intermediates used to construct oligonucleotide sequences during solid-phase synthesis. Phosphoramidates describe a different phosphorus-containing chemical structure and are not interchangeable with phosphoramidite building blocks used in routine oligonucleotide manufacturing.
Modern therapeutic programmes also incorporate modified phosphoramidites carrying conjugation, targeting and delivery functionalities while maintaining compatibility with standard phosphoramidite coupling cycles. Understanding this distinction is important when selecting raw materials for synthesis workflows.
Advanced ASO and siRNA design
Nucleic acid therapeutic programmes frequently require specialised solid supports and phosphoramidites beyond standard synthesis reagents.
Biosearch Technologies' Nucleic Acid Therapeutics Toolbox includes lipophilic modifiers, GalNAc reagents and specialised chemistries designed to support targeted delivery strategies for ASOs and siRNA therapeutics. Available options include fatty-acid-based modifiers, cholesterol-related delivery approaches, tocopherol-related chemistries and GalNAc conjugation solutions that can be incorporated using standard phosphoramidite synthesis workflows.
These tools help developers explore targeted delivery strategies while maintaining compatibility with established oligonucleotide manufacturing processes. The extensive portfolio of modification chemistries supports a broad range of therapeutic oligonucleotide design requirements.
Scale-up and manufacturing consistency
As oligonucleotide programmes progress from development to manufacturing, consistency becomes increasingly important. Variability in pore size, loading, chemistry or support quality can affect synthesis performance and process reproducibility.
Manufacturers therefore evaluate factors such as:
- Lot-to-lot consistency
- Manufacturing scalability
- Process robustness
- Quality documentation
- Support for GMP supply requirements
- Technical collaboration during process development
Selecting suppliers with established CPG manufacturing expertise, phosphoramidite capabilities and oligonucleotide synthesis knowledge can help support efficient scale-up and long-term production success.