Product Overview

The E. coli DNA Assay Kit is a qPCR-based solution designed for the quantitative detection of residual Escherichia coli host cell DNA (HCD) in biopharmaceutical products. Utilizing TaqMan fluorescent probe technology, the kit delivers highly sensitive, specific, and reproducible quantification of residual E. coli DNA throughout biologics development and manufacturing.

The assay supports regulatory compliance for residual host cell DNA testing and is suitable for recombinant proteins, enzymes, vaccines, plasmid DNA products, and other biologics produced using E. coli expression systems.

Background

Escherichia coli is one of the most widely used host organisms for the production of recombinant proteins, vaccines, insulin, growth hormones, interferons, enzyme preparations, and plasmid DNA. Its rapid growth, high expression efficiency, and cost-effective cultivation make it a preferred prokaryotic expression platform.

However, residual host cell DNA can remain in the final product if not adequately removed during downstream purification. Excessive residual DNA may present potential safety risks and is therefore strictly regulated by global pharmacopoeias and regulatory agencies.

As regulatory requirements continue to evolve, qPCR has become the preferred method for residual host cell DNA analysis due to its sensitivity, specificity, and quantitative accuracy.

Figure 1: Broad Applications of the E. coli Recombinant Expression System in Biopharmaceutical and Other Fields.

However, while efficiently synthesizing target products using E. coli, the host cell's own biological components—such as host cell proteins (HCPs) and host cell DNA (HCD)—become major process-related impurities. If these residual impurities are not effectively removed by downstream purification processes, their presence in the final product may pose serious safety risks to the human body. In particular, residual host cell DNA may carry three major potential biological risks: immunogenicity, carcinogenicity, and infectivity.

Figure 2: Manual/Automated Extraction + E. coli Residual DNA Detection Workflow.

Intended Use

The E. coli DNA Assay Kit is intended for the quantitative determination of residual E. coli host cell DNA in biological products using real-time PCR technology based on TaqMan fluorescent probes.

The assay is suitable for use in:

• Recombinant proteins

• Antibodies

• Vaccines

• Enzyme preparations

• Plasmid DNA products

• Other biologics derived from E. coli expression systems

Key Features

High Sensitivity Detection

• Limit of quantification (LOQ) as low as 30 fg/μL

• Suitable for stringent residual DNA testing requirements

Excellent Specificity

• Specifically detects E. coli genomic DNA

• No significant cross-reactivity with other common host cell DNAs

Accurate Quantification

• DNA standards calibrated against national reference standards

• Concentration consistency with RSD < 5%

Robust Reproducibility

• Intermediate precision CV < 15%

• Consistent results across operators and laboratories

Reliable Stability

• Maintains performance after accelerated aging at 37°C for 14 days

• Stable after five freeze-thaw cycles

• Demonstrates strong lot-to-lot consistency

Regulatory-Oriented Design

• Primer and probe sequences developed according to pharmacopoeia methodologies

• Supports compliance with residual host cell DNA testing requirements

Applications

The E. coli DNA Assay Kit can be used throughout the biologics development lifecycle:

Process Development

• Purification process optimization

• Host cell DNA clearance evaluation

Process Validation

• Residual DNA monitoring during process validation studies

• Manufacturing consistency assessment

Quality Control

• Release testing of biological products

• In-process quality monitoring

Applicable Sample Types

• Recombinant proteins

• Enzyme preparations

• Vaccines

• Plasmid DNA products

• Other E. coli-derived biological products

Performance Data

Standard Curve Performance

The product offers a wide linear range from 30 fg/μL to 300 pg/μL, with R² = 1. 000 and an amplification efficiency of 98. 22%. The coefficient of variation (CV) at all concentrations is less than 15%.

Figure 3: E. coli Standard Curve Amplification Plot

Accuracy

Hzymes' E. coli DNA standards are calibrated against the national DNA reference standard, with a purity of 100%. qPCR-determined concentrations show RSD < 5% compared to the national standard. Primers and probes match pharmacopoeial sequences, precisely meeting regulatory expectations.

Figure 4: Electrophoresis of Hzymes E. coli DNA Standards vs National Standard.

Table 2: qPCR Quantification Results of Hzymes E. coli DNA Standards vs National Standard.

Spike Recovery Rate

Validated across multiple customers and diverse sample types, the kit is compatible with recombinant proteins, enzyme preparations, plasmid DNA, and other sample categories for E. coli HCD detection. The spike recovery rate remains consistently between 70% and 130%.

Figure 5: Spike Recovery Rates from Multiple Customers Using Different Sample Types.

Limit of Quantification and Precision

The kit provides a consistent limit of quantification (LOQ) down to 30 fg/μL. Precision testing shows that results from different operators have a CV of less than 15%, ensuring high experimental credibility and reproducibility.

Figure 6: Amplification Curve at 30 fg/μL Limit of Quantification.

Table 3: Intermediate Precision Results.

Specificity

The product demonstrates high specificity, capable of specifically detecting E. coli DNA without cross-reactivity from other common host cell DNA sources.

Figure 7: Cross-Reactivity Test with Different Genomic DNAs.

Stability

The kit maintains performance after accelerated thermal aging for 14 days at 37°C and after five freeze-thaw cycles, showing no loss in functionality. Storage and transportation are thus worry-free. Inter-lot consistency tests further demonstrate stable and uniform product performance.

Table 4: Stability under 37°C Heat Acceleration and Freeze-Thaw Conditions.

Figure 8: Amplification Curves of Different Kit Lots.

FAQ

Why is the qPCR amplification signal weak or the standard curve performance unstable?

Possible Cause 1: Inaccurate sample preparation or DNA degradation

Ensure that genomic DNA standards and samples are properly stored and avoid repeated freeze-thaw cycles. DNA degradation may reduce amplification efficiency and affect quantification accuracy.

Possible Cause 2: Inaccurate pipetting or reaction setup errors

Calibrate pipettes regularly and use low-retention, filtered tips to ensure accurate reaction setup and reduce variability between wells.

Possible Cause 3: Incomplete mixing of reaction components

Vortex and briefly centrifuge the qPCR reaction mix to ensure uniform distribution of primers, probes, and template DNA.

Why are recovery or quantification results inconsistent between runs?

Possible Cause 1: Variation in sample matrix composition

Complex biological matrices (e.g., proteins, antibodies, enzyme formulations) may affect DNA extraction or amplification efficiency. It is recommended to validate spike recovery in each matrix type.

Possible Cause 2: Improper DNA extraction efficiency (magnetic bead loss or incomplete binding)

Ensure magnetic beads are fully resuspended before use and avoid bead loss during washing steps. Carefully aspirate supernatant without disturbing beads.

Possible Cause 3: Improper elution or incomplete DNA release

Ensure sufficient mixing during elution. If beads remain aggregated, gently vortex or incubate at moderate temperature to improve DNA release efficiency.

Why does non-specific amplification or background signal appear?

Possible Cause 1: Contamination during sample handling

Use separate areas for reagent preparation, sample processing, and amplification setup. Always use aerosol-resistant tips.

Possible Cause 2: Reagent contamination

Replace reagents and verify nuclease-free water and consumables if unexpected amplification appears in negative controls.