PEG-NaCl Preservative for Cell-Free DNA Stability

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Solution Overview

Problem

Current methods for preserving cell-free DNA in biological samples, such as plasma, face challenges including low abundance, contamination with genomic DNA due to cell lysis during storage and shipping, and the use of aldehydes which can damage DNA and introduce mutation artifacts.

Innovation Solution

A preservative composition comprising polyethylene glycol (PEG), sodium chloride (NaCl), and EDTA or citrate, which stabilizes cells and prevents lysis, thereby minimizing genomic DNA contamination and allowing for extended storage of cell-free nucleic acids at ambient temperature without the use of aldehydes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If standard EDTA or sodium citrate tubes are used with cold storage and plasma preparation within 6 hours, then genomic DNA release is prevented, but equipment requirements and operational complexity increase

Engineering Contradiction:

Improveprevention of gDNA releaseVSAvoidequipment requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts the plasma separation step from the immediate post-collection process by using a preservative composition that stabilizes cells in whole blood, allowing plasma preparation to be deferred without risk of gDNA contamination

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The preservative composition is applied preliminarily to whole blood immediately after collection to stabilize cells and prevent lysis, enabling extended storage before plasma separation without compromising DNA integrity

Inventive Principle:

Principle #10Preliminary action

2Reliability

If aldehyde-based preservatives are used to stabilize cells, then cell lysis is prevented, but DNA damage and mutation artifacts occur

Engineering Contradiction:

Improvecell stabilizationVSAvoidDNA damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention replaces long-standing aldehyde-based preservatives with a novel composition using PEG and NaCl that achieves cell stabilization without the harmful cross-linking effects, effectively discarding the outdated approach

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention changes the chemical parameters of the preservative composition from aldehyde-based cross-linking agents to PEG-based osmotic stabilization with EDTA/citrate, fundamentally altering the mechanism of cell stabilization to avoid DNA damage

Inventive Principle:

Principle #35Parameter changes

3Reliability

If plasma is prepared immediately after collection, then gDNA contamination is minimized, but operational complexity and processing time increase

Engineering Contradiction:

Improvereduction of gDNA contaminationVSAvoidprocessing time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The preservative composition performs preliminary cell stabilization immediately upon blood collection, preventing lysis during storage and transport, which allows plasma separation to be delayed without increasing gDNA contamination risk

Inventive Principle:

Principle #10Preliminary action

4Reliability

If cold storage is required for plasma, then DNA degradation is prevented, but operational complexity and infrastructure requirements increase

Engineering Contradiction:

Improveprevention of DNA degradationVSAvoidstorage temperature requirements

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The invention changes the storage temperature parameter from requiring cold chain (2-8°C) to allowing ambient temperature storage by using PEG-based preservative composition that stabilizes cells and prevents DNA degradation through osmotic protection

Inventive Principle:

Principle #35Parameter changes

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 composition effectively preserves cell-free DNA for up to 28 days at room temperature with minimal genomic DNA contamination, even during movement and shipping, and prevents DNA damage, making it suitable for resource-limited settings and diagnostic applications.

Implementation Method 1

A preservative composition comprising polyethylene glycol (PEG), sodium chloride (NaCl), and EDTA or citrate, which stabilizes cells and prevents lysis

Methodology Applied

Scientific EffectOsmotic pressure: Osmotic Pressure

Implementation Method 2

A preservative composition comprising polyethylene glycol (PEG), sodium chloride (NaCl), and EDTA or citrate

Methodology Applied

Scientific EffectChelation:

Data Source

PatentEP3464588B2Preservation of cell-free nucleic acids in biological samples

Publication Date: 2025.01.08 NORGEN BIOTEK CORP

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AI summary

Provided is a composition for preserving cell-free nucleic acids and/or cells in a biological sample and methods for use thereof. The composition comprises at least one volume excluding polymer, at least one osmotic agent and at least one enzyme inhibitor. The composition optionally further comprises at least one metabolic inhibitor. Further, provided is a kit comprising the composition, preferably in a blood collection tube, or the components of the composition.