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@#Objective To prepare a national reference standard for the quantification of HEK293 cell DNA content,so as to provide a support for the determination of residual DNA in HEK293 cells in the industry.Methods HEK293 cell DNA prepared using Genomic-tip 500/G and genomic DNA purification reagents was used as source materials,and the purity and content were assessed using ultraviolet spectrophotometry and agarose gel electrophoresis.After dilution to approximately 100 ng/μL,the DNA was aliquoted at 160 μL/tube.Five different laboratories were organized for collaborative calibration by using ultraviolet spectrophotometry, and the stability and applicability were evaluated.Results The HEK293 cell DNA national reference standard exhibited A_(260)/A_(280) ratios between 1.8 and 2.0 and displayed a single band on electrophoresis,meeting the specified criteria.Collaborative calibration across five laboratories yielded 78 valid data points with an average content of 104.8 ng/μL,a relative standard deviation(RSD) of 4.2%.The 95% confidence interval for the mean was 103.8—105.8 ng/μL,and the 95% reference range for single measurements was 96.0—113.6 ng/μL.The average confidence limit rate was 1.0%,and the recommended storage condition was-80 ℃.Applicability studies were conducted using two different models of fluorescence quantitative PCR instruments.The reference standard exhibited good applicability within the range of 0.3—3 000 pg/reaction,with amplification efficiencies of 101% and 95%,and R~2 values of 0.999 2 and 0.999 5 for the standard curves,respectively.Conclusion This batch of HEK293 cell DNA national reference standard meets all required specifications and can be utilized as a national reference standard for fluorescence quantitative PCR detection,with a certified content of 104.8 ng/μL,assigned batch number 270039-202301.
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@#Objective To develop and verify a qPCR method for the qualitative and quantitative analysis of residual host DNA in human rabies vaccine(Vero cells) stock solution.Methods The qPCR standard curve was established by using the Vero cell DNA quantitative national standard,and the residual host DNA was extracted using magnetic beads.The specificity,repeatability,intermediate precision,accuracy and durability of the method were verified,and the linear range and limit of quantification were determined.The residual DNA of three batches of human rabies vaccine(Vero cells) stock solution was quantitatively analyzed and the fragment size was qualitatively analyzed by using this method.Results The correlation coefficients(R~2) of Vero cell DNA quantitative national standard amplification standard curve were all more than 0.99 by qPCR,and the quantitative range was 0.3 pg/mL～30 ng/mL.The method showed good specificity and repeatability.In the verification of intermediate precision,accuracy and durability,the relative standard deviations(RSD)of detection results of the samples were all less than 10%.The residual DNA content of Vero cells in three batches of stock solution was 0.20～0.77 ng/dose,which met the relevant standard of Chinese Pharmacopoeia(Volume Ⅲ,2020edition).The residual DNA fragments greater than 154 bp accounted for 52%～63%.Conclusion The developed qPCR method for the detection of residual DNA in human rabies vaccine(Vero cells) stock solution had good specificity,repeatability,intermediate precision and durability,and qualitatively and quantitatively analyzed the residual DNA rapidly and accurately,which was of great significance for improving the detection and control of residual DNA content in the production process and final product of human rabies vaccine(Vero cells).
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OBJECTIVE: To prepare the national standard substance for quantitative determination of residual DNA in mouse myeloma(NS0)cells. METHODS: NS0 cell DNA was prepared using genomic DNA purification reagents QIAGEN and Genomic-tip 500/G,analyzed for purity and concentration by UV spectrophotometry and agarose gel electrophoresis, and split in 100 microliters and frozen in screw cap tubes. Then five independent laboratories were organized to calibrate the first batch of NS0 DNA national standard using UV spectrophotometry, and evaluated the stability and applicability. RESULTS: The prepared national standard substance of NSO DNA was qualified as indicated by A260/A280 between 1.7 and 1.9 and a single specific band in agarose gel electrophoresis. The standard substance was calibrated for 90 times by the five laboratories,and the results showed a geometric mean concentration of 87.5 μg•mL-1, the 95% confidence interval of the geometric mean concentration in a single determination was 86.6-88.5 μg•mL-1. Short-term stability experiments showed that there was no significant change in the standard DNA concentration and A260/A280 ratio after being stored at 4 ℃ for 4 m. The results of storage stability test at -20 and -70 ℃ for 1 year revealed that there was no significant change in the standard DNA concentration and A260/A280 ratio, and the electrophoresis strip was single, so the standard substance was stable at -20 ℃. In applicability studies using the NS0 DNA standard substance, the real-time PCR had high sensitivity up to 0.003 pg of DNA with good linearity (r20.999) in the content range of 3 fg•μL-1-300 pg•μL-1. CONCLUSION: The prepared standard substance with batch number of 330002-201701 and DNA concentration of 87.52 μg•mL-1 is qualified in all tests and may be used as national standard substance for residual DNA assay by real-time PCR method.
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OBJECTIVE: To develop and verify a magnetic beads-based extraction combined with quantitative PCR(q-PCR)method for determination of residual host cell DNA in recombinant human albumin products expressed in Pichia pastoris. METHODS: The residual Pichia pastoris host cell DNA in samples were extracted by magnetic beads-based extraction method and then determined by Taqman probe-based q-PCR. The residual DNA content was calculated according to the standard curve. The developed method was verified for accuracy and precision with different derivation albumin matrixes and concentrations, and the residual DNA of 3 batches of recombinant human albumin products expressed in Pichia pastoris were detected. RESULTS: The minimum detection limit of Pichia pastoris residual DNA by the developed method was 3 fgμL-1, the linear range was 3 fgμL-1-300 pgμL-1, and the correlation coefficient(r2) was 0.998 3. The recovery rates of spiked samples in rHA matrix were 93.58%(RSD 19.6%, n=4)at 100 fgμL-1 and 215.56%(RSD 42.9%, n=4) at 10 fgμL-1, respectively. The recovery rates of spiked samples in HSA matrix were 67.09%(RSD 6.9%,n=3)at 100 fgμL-1 and 113.40%(RSD 11.1%, n=3) at 10 fgμL-1, respectively. The residual Pichia pastoris DNA contents in 3 batches of recombinant human albumin products expressed in Pichia pastoris determined by the developed method were 5.98, 4.16, 4.49 fgμL-1(n=7) respectively and not more than 1 ng per 10 g protein. CONCLUSION: Magnetic beads extraction method combined with fluorescence quantitative PCR method solves the technical problem of quantitative determination of trace DNA in recombinant human albumin products with ultra-high concentration protein. The method is accurate and reproducible, and can be used for quantitative determination of DNA residue in recombinant human albumin expressed by Pichia pastoris.
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Objective To develop and verify a method for determination of residual host cell DNA in recombinant human interferon α2b substances, which is used for the quality control of the product.Methods The residual host cell DNA was extracted by wako DNA extractor kit and determined by SYBRGreen based q-PCR using standard DNA as control.The residual host cell DNA was analyzed according to the standard curve.The developed method was verified by primer specifity, results accuracy and precision and used for determination of 3 batches of interferon substances. Results The minimum quantitative limit of residual host cell DNA by the developed method was 12 fg/μL, while the linear range was 12 fg/μL-120 ng/μL, with a correlation coefficient (r) of 0.998.The designed primers were specific to the DNA templates.The recovery rates of spiked samples with different DNA quantity were between 50%-200%.The residual host cell DNA determined by this method were not more than the limit, which were complied with the requirements for residual host cell DNA in Chinese Pharmacopeia ( volume III,2010 edition and 2015 edition) .Conclusion The wako DNA extractor kit could successfully solved the technical difficulties of sample pretreatment during residual DNA assay.The q-PCR method was simple, rapid and accurate for quantitation of residual host cell DNA in interferon substances.
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OBJECTIVE: To prepare the national standard substance for quantitative determination of residual DNA in CHO cells. METHODS: CHO cell DNA was prepared using QIAGEN Genomic-tip 500/G and genomic DNA purification reagents and analyzed for purity and concentration by UV spectrophotometry and agarose gel electrophoresis. Then the standard substance of CHO DNA was calibrated collaboratively, and evaluated for stability and applicability. RESULTS: The prepared national standard substance of CHO DNA was qualified as indicated by A260/A280 between 1.7 and 1.9 and a single specific band in agarose gel electrophoresis. The standard substance was calibrated for 90 times by six laboratories, and the results showed a geometric mean concentration of 93.63 μg · mL-1 (95% confidence interval 92.86-94.40 μg · mL-1). The 95% confidence interval of the geometric mean concentration in a single determination was 86.51-100.89 μg · mL-1. The mean confidence limit rate was 0.81%. The DNA concentration was stable after storage at-20, 4, 25 and 37°C for 4 months, but A260/A280 was decreased when stored at 37°C for 4 months. The electrophoresis results showed a single band after storage at -20, 4 and 25°C for 4 months, but showed degradation after storage at 37°C for 4 months. The long term stability test revealed that the DNA concentration and purity were stable after storage at -20°C for 12 months. In applicability studies using the CHO DNA standard substance, the fluorescence method showed good linearity (r > 0.9900) in the concentration range of 0.781-100 ng · mL-1, with RSD of less than 10%. The real-time PCR had high sensitivity up to 10-2 pg of DNA with good linearity (r > 0.9900) in the content range of 10-2-103 pg, and the melting curve showed a single peak. CONCLUSION: The prepared standard substance with batch number of 270026-201101 and DNA concentration of 93.63 μg · mL-1 is qualified in overall tests and may be used as national standard substance for residual DNA assay by fluorescence and real-time PCR methods. Copyright 2013 by the Chinese Pharmaceutical Association.