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Thermo Fisher Scientific has more than 45 years of experience developing enzymes, buffers, nucleotides, ladders, nucleic acids, and other reagents for life science research. Our dedicated OEM teams partner with customers with product development, manufacturing, and commercialization.

In your molecular assay development journey, our experts help you to select the best-fitting products for your application. Our R&D scientists support assay development efforts in RT-PCR, isothermal amplification, and NGS methods.

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Raw materials for custom assay development

Molecular diagnostic assays and kits require high quality reagents. Our vast portfolio of reagents is available off the shelf in bulk quantities or can be customized for your specifications. Figure 1 lists our most popular customization capabilities.

Infographic with text showing the three groups of customization

Figure 1. Overview of customization capabilities.

Large-scale manufacturing and production

We offer large scale manufacturing and production services include sourcing and quality control of raw materials, manufacturing the assay components, assembling kits, packaging, customizing labels, and more.

Custom reagents and material modification

We tailor our existing products to your specifications. This may involve modifying existing assays to fit specific sample types, concentration and composition, or stability requirements.

Custom assay design and development

We offer comprehensive expertise in developing and designing assays, including but not limited to protocol design, reagent and components selection, condition optimization, performance evaluation, quality validation, and regulatory compliance. These services are available for protein cloning, expression, and purification, enzyme evolution, and modification of RT and PCR enzymes and buffers.

Reagents for custom assay development

Custom assay development relies on quality reagents optimized for molecular diagnostic assay. Reagents and enzymes commonly used in custom assay development are listed in Tables 1 to 5. Click on the accordions to see the tables.

Table 1. Reverse transcriptases available for assay development.

One-step RT-qPCR

Two-step RT-qPCR

One-step RT-PCRLAMPcDNA synthesis
Invitrogen Lyo-ready SuperScript Reverse Transcriptase, One-step RT-qPCR
Invitrogen SuperScript IV Reverse Transcriptase
Invitrogen SuperScript III Reverse Transcriptase
Thermo Scientific Maxima Reverse Transcriptase
Thermo Scientific Maxima H Minus Reverse Transcriptase
Thermo Scientific RevertAid Reverse Transcriptase
Thermo Scientific RevertAid H Minus Reverse Transcriptase
RT-qPCR: Reverse transcription quantitative polymerase chain reaction
LAMP: Loop-mediated isothermal amplification

 View the enzyme selection guide to select products suitable for your application

Table 3. Modifying enzymes available for assay development.

CloningNGS library preparation LabelingNA preparationIVT


Methylation analysisIsothermal amplification
Thermo Scientific Poly(A) Polymerase, Yeast
Thermo Scientific T7 RNA Polymerase
Invitrogen DNA Polymerase I
Thermo Scientific Klenow Fragment
Thermo Scientific Klenow Fragment, exo-
Thermo Scientific T4 DNA Polymerase
Thermo Scientific T7 DNA Polymerase
Thermo Scientific T4 Polynucleotide Kinase
Thermo Scientific Terminal Deoxynucleotidyl Transferase
Thermo Scientific Endonuclease V, T. maritima
Thermo Scientific Endonuclease IV, E. coli
Thermo Scientific Exonuclease I
Thermo Scientific Exonuclease III
Thermo Scientific Exonuclease VII
Thermo Scientific T7 Gene 6 Exonuclease
Thermo Scientific Lambda Exonuclease
Thermo Scientific Pyrophosphatase, inorganic
Thermo Scientific RNase A/T1 mix
Thermo Scientific RNase A
Thermo Scientific RNase I
Thermo Scientific Ribonuclease H (RNase H)
Thermo Scientific RNase T1
Thermo Scientific T4 RNA Ligase
Thermo Scientific T4 beta-glucosyltransferase
Thermo Scientific T4 DNA Ligase
Thermo Scientific S1 Nuclease
Thermo Scientific DNase I, RNase-free
Thermo Scientific CpG methyltransferase (M.Sssl)
Thermo Scientific Uracil-DNA Glycosylase, heat-labile
Thermo Scientific Uracil DNA Glycosylase
Thermo Scientific FastAP Thermosensitive Alkaline Phosphatase
Thermo Scientific Micrococcal Nuclease
Thermo Scientific restriction enzymes
Thermo Scientific Single-Strand Binding Protein (SSB)
Thermo Scientific SP6 RNA Polymerase
Thermo Scientific T3 RNA Polymerase
Invitrogen RNaseOUT Recombinant Ribonuclease Inhibitor
Thermo Scientific RiboLock RNase Inhibitor
Thermo Scientific Proteinase K
NA: Nucleic acid
IVT:in vitro transcription
PCR: Polymerase chain reaction

 View the enzyme selection guide to select products suitable for your application

Table 4. dNTPs available for assay development.

One-step RT-qPCRTwo-step RT-qPCRLAMPcDNA synthesis
Thermo Scientific dNTP Mix
Thermo Scientific dATP Solution (100mM)
Thermo Scientific dCTP Solution (100 mM)
Thermo Scientific dGTP Solution (100 mM)
Thermo Scientific dTTP Solution (100 mM)
Thermo Scientific dUTP Solution (100 mM)
RT-qPCR: Reverse transcription quantitative polymerase chain reaction
LAMP: Loop-mediated isothermal amplification

 View the enzyme selection guide to select products suitable for your application

Table 5. Enzymes for isothermal nucleic acid amplification (INAAT)

Invitrogen Lyo-ready Bst DNA PolymeraseLAMP, HDA, EXPAR, RCA
Invitrogen SuperScript IV RT-LAMP Master MixLAMP
Invitrogen SuperScript IV Reverse Transcriptase and other RTsLAMP, NASBA, TMA
Thermo Scientific T7 RNA PolymeraseNASBA, TMA
RNase inhibitors (Ribolock, RNaseOUt, and others)LAMP, NASBA, TMA
Thermo Scientific Phi29 DNA PolymeraseMDA, WGA, RCA
Thermo Scientific EquiPhi29 DNA PolymeraseMDA, WGA, RCA
Thermo Scientific Klenow Fragment, exo–SDA
EXPAR: Exponential amplification reaction 
HDA: Helicase-dependent amplification 
LAMP: Loop-mediated isothermal amplification 
MDA: Multiple displacement amplification 
NASBA: Nucleic acid sequence-based amplification 
RCA: Rolling circle amplification 
SDA: Strand displacement amplification 
TMA: Transcription-mediated amplification 
WGA: Whole-genome amplification 

Resources for custom assay development

FAQs: Raw materials for custom assay development

No, High Fidelity enzymes are not compatible with TaqMan probes qPCR. Proofreading DNA polymerases lack 5’→ 3’-exonuclease activity which is essential for TaqMan assay.

Platinum II Taq Hot-Start DNA Polymerase works best with inhibitor-containing samples.

We recommend using Lyo-ready SuperScript Reverse Transcriptase 1-step RT-qPCR, which was specially created for one-step RT-qPCR application. We have prepared an optimized protocol for a one-step RT-qPCR application that contains Lyo-ready SuperScript Reverse Transcriptase, 1-step RT-qPCR, and Lyo-ready Platinum II Taq Hot-Start DNA Polymerase.

 Read application note: SARS-CoV-2 RNA detection with the lyo-ready one-step RT-qPCR system
 View the user guide: Lyo-ready one-step RT-qPCR system

We do not recommend using SuperScript IV reverse transcriptase for one-step RT-qPCR assay due to the high affinity to the template. This feature for one-step RT-qPCR application is excessive because it might prevent polymerase to act efficiently. SuperScript IV Reverse Transcriptase is the number one enzyme of choice for the NGS library preparation step as well as the two-step RT-qPCR assay.

Yes, Collibri Cleanup Beads and AMPure XP are interchangeable but note the differences in the cleanup/size selection protocols.

Yes, all Thermo Fisher Scientific DNA/RNA modifying enzymes are rigorously tested and suitable for NGS library prep workflows.


Check out our resources on molecular assay development.

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Support and services

Get support for your molecular assay development. For information on a personalized IVD transition plan contact us at

Other OEM and commercial supply resources

For Research Use Only. Not for use in diagnostic procedures.

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