The phrase "according to previous protocols" is correct and usable in written English.
You can use it when referencing established guidelines or procedures that have been set in the past.
Example: "According to previous protocols, all safety measures must be followed during the experiment."
Alternatives: "in line with earlier protocols" or "as per prior protocols".
In vitro mRNA synthesis and transfections were performed according to previous protocols.46 In brief, T7 promoter and polyA tail were added by polymerase chain reaction (PCR) using KAPA taq kit (Kapabiosystems, London, UK).
RNA isolation, cDNA synthesis, and microarray hybridization were performed according to previous protocols [45].
We used SISPA to screen and identify viral agents, according to previous protocols [11], [18], [23].
Immunoliposomes with biotinylated-PE lipid (0.1% incorporated) were engineered according to previous protocols [47].
The incubation time for all inhibitors was 20 min. Polyacrylamide gel substrates were prepared according to previous protocols [46] [48].
RUTI® was administered twice, at weeks 9 and 12, 21 days apart, according to previous protocols [59].
For quantitative analysis of gene expression, total RNA was extracted according to previous protocol (Zhang et al., 2015).
The CT320 × 6-GFP cell line was obtained by transduction with a LV-PGK-GFP lentiviral vector, kindly provided by Françoise Carlotti, Leiden University Medical Centre, The Netherlands, according to previous protocol (Carlotti et al, 2004).
Results were reported to a gene (ANKRD49) that is located in a chromosomal region (11q21) usually not altered by copy number variation in HCC. 25 HBV cccDNA (copy number/ cell) was quantified by a specific real-time PCR, according to previous protocol.
Analysis of the A TA nTAA motif in the promoter region of the UGT1A1 gene was performed by PCR, according to previous protocol (Monaghan et al, 1999), followed by automated sequencing analysis of the purified PCR products using an automated sequencer (ABI PRISM 3130XL DNA Sequencer; Applied Biosystems, Madrid, Spain).
Differentiation experiments were designed according to previous published protocols [49], [50].
