Recombinant Proteins Built for Assays, Diagnostics, Research Tools, and Genetic Medicine

A recombinant protein is only valuable if it performs in the system where it will be used.

For some companies, that system is an ELISA. For others, it is a qPCR workflow, a lateral-flow assay, a biosensor, a cell-based potency assay, a CRISPR diagnostic, an immunogenicity study, a receptor-binding assay, a vaccine antigen screen, a companion diagnostic, or a release-test method supporting a larger therapeutic program.

At Xoligo Biologics, we produce assay-ready recombinant proteins for companies that need more than generic expression. We support the development, production, purification, characterization, and stabilization of recombinant proteins that are meant to function inside real diagnostic, research, analytical, and biomanufacturing workflows.

Xoligo is a Component CDMO for genetic medicine, diagnostics, and precision biomanufacturing. That means we do not think of recombinant proteins as isolated molecules. We think of them as functional components inside larger systems involving oligonucleotides, enzymes, plasmids, RNA workflows, diagnostic reagents, standards, controls, buffers, assays, and manufacturing processes.

This is where Xoligo becomes different from a standard protein vendor.

A catalogue protein company may be useful when a researcher needs a common antigen quickly. A full-scale biologics CDMO may be useful when a therapeutic protein is ready for large GMP manufacturing. But many companies need something in between: custom recombinant proteins that are technically strong, analytically characterized, application-aware, and suitable for assay development, diagnostic manufacturing, preclinical research, or pre-GMP component supply.

That is the role Xoligo is built to fill.

From Cambridge, we support program strategy, assay context, biotech interface, and advanced modality planning. From Montreal, we support nucleic acid development, analytical characterization, and manufacturing-pathway design. From Frederick,

Maryland, we support recombinant protein expression, microbial fermentation, enzyme production, assay protein manufacturing, and diagnostic component development.

Together, these locations allow Xoligo to support recombinant protein work not as a standalone service, but as part of a complete molecular component platform.

What “Assay-Ready” Means

Assay-ready protein production means the protein is developed with the final application in mind from the beginning.

It is not enough for the protein to appear on a gel. It is not enough for the protein to be expressed at high yield. It is no

t enough for the protein to be purified once under ideal conditions.

The protein must be useful.

Depending on the application, that may mean it needs to bind correctly, retain activity, remain stable in a formulation, avoid aggregation, maintain lot-to-lot consistency, support reproducible signal, serve as a standard, function as a calibrator, act as a positive control, support antibody screening, work in a diagnostic kit, or withstand storage and shipping.

Xoligo supports assay-ready recombinant proteins including:

Recombinant antigens
Control proteins
Calibrators
Reference proteins
Cytokines
Growth factors
Receptor proteins
Ligands
Enzymes
Antibody fragments
VHHs and scFvs
Fc-fusion proteins
CRISPR-associated proteins
RNA workflow enzymes
Diagnostic assay proteins
Companion diagnostic components
Cell-based assay proteins
Protein standards
Protein-oligo system components

The goal is always the same: produce a protein that works in the customer’s system, not merely a protein that exists.

Recombinant Antigens for Diagnostics and Immunology

Recombinant antigens are central to diagnostic development, vaccine research, immunology, serology, antibody discovery, and assay manufacturing.

A poorly designed antigen can create weak signal, poor specificity, cross-reactivity, instability, or misleading assay results. In contrast, a well-designed recombinant antigen can improve screening quality, diagnostic performance, antibody selection, and downstream product development.

Xoligo supports recombinant antigen production for infectious disease diagnostics, oncology assays, autoimmune research, vaccine development, companion diagnostics, veterinary diagnostics, research tools, and immunoassay platforms.

Programs may include sequence review, domain selection, construct design, tag strategy, host-system selection, expression screening, purification development, analytical characterization, and stability support.

Some antigens express well in E. coli. Others require eukaryotic folding, secretion, disulfide-bond support, glycosylation awareness, or alternative expression systems. Xoligo evaluates each program individually rather than forcing every antigen into one host.

That matters because antigens are often judged by performance, not by expression convenience.

If the antigen does not bind the relevant antibody, support clean assay signal, or remain stable through the intended workflow, the manufacturing process has not succeeded.

Controls, Calibrators, and Standards

Diagnostics and analytical workflows depend heavily on reliable controls, calibrators, and standards.

These materials are often overlooked because they are not the final product. But they determine how the final product is measured, validated, compared, interpreted, and trusted.

Xoligo supports recombinant protein controls, calibrators, standards, and reference materials for diagnostic assays, molecular testing, immunoassays, enzyme assays, cell-based assays, potency assays, release testing, research kits, and platform development.

These materials may be used to establish assay curves, confirm reagent performance, support lot release, compare manufacturing batches, evaluate stability, qualify methods, or support customer-facing kit performance.

For these applications, protein quality must be defined around use.

A calibrator needs consistency.
A positive control needs reproducible signal.
A standard needs traceability.
A reference material needs characterization.
A kit component needs stability.
A release-test protein needs documentation.

Xoligo can support development of these materials with appropriate purification, analytical characterization, batch documentation, formulation, and stability planning.

Cytokines, Growth Factors, and Cell-Based Assay Proteins

Cell-based systems require proteins that are biologically active and consistent.

Cytokines, growth factors, ligands, receptor-binding proteins, and cell-signaling proteins are used across cell therapy, immunology, stem cell research, organoid development, vaccine research, oncology, inflammation, and potency testing.

For these applications, purity alone is not enough. Biological activity matters. Lot consistency matters. Stability matters. Low endotoxin can matter. Formulation and storage conditions can matter. The protein must behave predictably in sensitive biological systems.

Xoligo supports production of cytokines, growth factors, ligands, and receptor proteins for research, diagnostic, preclinical, and assay-development use.

Depending on the molecule, expression may be performed in microbial, yeast, mammalian, or alternative systems. Each platform offers different advantages in speed, yield, folding, modification, and cost.

Our objective is to match the protein to the correct production strategy and then characterize it in a way that supports its intended biological use.

Receptor Proteins, Binding Proteins, and Functional Assay Components

Many drug discovery and diagnostic workflows depend on recombinant proteins that preserve binding behavior.

These may include receptors, receptor domains, ligands, soluble extracellular domains, Fc-fusions, tagged proteins, assay binders, antibody targets, and protein complexes.

Producing these proteins can be more difficult than producing simple soluble enzymes or antigens. They may require correct disulfide formation, dimerization, multimerization, glycosylation awareness, tag placement, solubility optimization, aggregation control, or careful buffer selection.

Xoligo supports custom recombinant protein production for binding assays, screening assays, immunoassays, structural studies, biophysical characterization, cell-based assays, and analytical method development.

Our development approach considers not only expression yield but also functional presentation.

Where the tag is placed can matter.

Where the domain begins and ends can matter.
Whether the protein is monomeric or multimeric can matter.
Whether the protein aggregates can matter.
Whether it remains active after storage can matter.

Xoligo builds those questions into development early.

Antibody Fragments, VHHs, scFvs, and Fc-Fusion Proteins

Assay-ready recombinant proteins increasingly include antibody-derived formats.

VHHs, scFvs, Fab fragments, Fc-fusions, bispecific fragments, and antibody scaffolds are used in diagnostics, imaging, targeted delivery, research tools, immunoassays, biosensors, and therapeutic discovery.

Xoligo supports production of antibody fragments and related recombinant binding proteins for customers who need flexible, functional, assay-ready material.

These formats may require different expression strategies depending on complexity. Some antibody fragments express efficiently in microbial systems. Others benefit from yeast, mammalian, or secretion-based platforms. Fc-fusions often require additional attention to folding, dimerization, purity, and downstream characterization.

This service also connects naturally to Xoligo’s broader VHH and Antibody Fragment Production page, CRISPR Enzyme Production page, and Protein-Oligo Conjugate Development page.

The strongest use case is not simply “make my antibody fragment.” It is: help me produce the binding component that makes my assay, diagnostic, delivery system, or molecular platform work.

Assay Proteins for Genetic Medicine and RNA Workflows

Genetic medicine programs increasingly require recombinant proteins that are not themselves therapeutic products but are essential to development.

Examples include:

CRISPR proteins
Cas enzymes
RNA polymerases
Capping enzymes
RNA ligases
Nucleases
RNase inhibitors
Reporter proteins
Assay antigens
Control proteins
Transfection or delivery-related proteins
Protein standards for analytical methods
Potency assay components

These proteins support RNA therapeutics, CRISPR editing, plasmid workflows, LNP development, cell therapy manufacturing, diagnostics, and release testing.

Xoligo’s value is that we understand the relationship between these proteins and the nucleic acid systems around them.

A Cas enzyme must work with a guide RNA.
A polymerase must work with the plasmid template.
A capping enzyme must support RNA quality.
A control protein must support assay interpretation.
A reporter protein must function reliably in the assay format.
A reference protein must support comparability.

That is why assay-ready protein production belongs inside Xoligo’s component CDMO model.

Host-System Selection

The right expression system depends on the protein and its application.

Xoligo supports development across multiple production approaches, including E. coli expression, yeast or Pichia expression, mammalian expression, and partner-supported specialized systems where appropriate.

E. coli can be ideal for many enzymes, antigens, fragments, and assay proteins requiring speed, cost efficiency, and scalable production. Yeast or Pichia can support secreted proteins, certain eukaryotic proteins, enzymes, and antibody fragments. Mammalian systems may be preferred for complex glycoproteins, receptors, Fc-fusions, or proteins requiring specific folding and post-translational context.

The best CDMO does not sell one host as the answer to every problem.

The best CDMO helps the customer choose the correct system before time and money are wasted.

Xoligo brings that host-neutral judgment into assay-ready protein development.

Purification and Characterization

Assay-ready proteins need purification strategies that protect function.

Xoligo supports purification workflows including affinity capture, ion exchange, hydrophobic interaction, size exclusion, polishing, endotoxin reduction, buffer exchange, concentration, filtration, and formulation screening.

Analytical characterization may include SDS-PAGE, Western blotting, protein concentration, purity assessment, molecular weight confirmation, identity testing, aggregation analysis, endotoxin testing, residual impurity evaluation, activity testing, binding assessment, and stability studies.

The analytical package is shaped by the intended use.

A diagnostic antigen may require binding and stability data.
An enzyme may require activity testing.
A calibrator may require concentration consistency.
A cell-based assay reagent may require low endotoxin and bioactivity.
A transfer-ready material may require stronger documentation and comparability support.

Xoligo does not overcomplicate every project. But we do help customers identify what level of characterization is appropriate for the next development stage.

Formulation, Stability, and Kit Compatibility

A protein that works immediately after purification may still fail as a diagnostic or assay component.

Storage, shipping, freeze-thaw exposure, lyophilization, buffer conditions, preservatives, stabilizers, and compatibility with other reagents can all affect performance.

Xoligo supports formulation and stability work for assay-ready proteins, including buffer screening, stabilizer evaluation, storage-condition studies, freeze-thaw testing, concentration optimization, lyophilization support, and compatibility testing with assay components.

This is especially important for diagnostic kits, research reagents, field-deployable assays, enzyme systems, cell-based assay reagents, and long-term supply programs.

The protein must remain useful when the customer uses it, not just when the CDMO releases it.

Scale-Up and Supply Continuity

Many assay-ready protein programs begin small.

A customer may need only a few milligrams for feasibility testing. Then the program succeeds. Suddenly they need grams, repeat lots, better documentation, consistent specifications, and a supply chain that does not collapse when the assay moves toward commercialization.

Xoligo supports development from early research lots through larger-scale production and transfer-ready manufacturing.

We help customers think through:

scale-up potential
repeat production
batch consistency
documentation
analytical comparability
raw material strategy
storage conditions
future quality requirements
commercial reagent supply
partner transfer

This continuity is one of the main reasons to work with a component CDMO instead of a one-time reagent vendor.

Why Xoligo? You know why.

Xoligo is built for the space between discovery reagent supply and full therapeutic manufacturing.

That is where many important programs actually live.

A diagnostic company may need a custom antigen and enzyme system.
An RNA company may need a polymerase and protein standard.
A CRISPR company may need Cas protein, guide RNA, and activity assays.

A cell therapy company may need cytokines, controls, and potency assay components.
A research-tool company may need reliable recombinant proteins at repeatable quality.
A biotech startup may need pre-GMP bridge material before committing to a larger CDMO.

Xoligo supports that middle layer with technical depth and commercial flexibility.

We understand recombinant proteins.
We understand enzymes.
We understand oligonucleotides.
We understand RNA workflows.
We understand diagnostics.
We understand microbial fermentation.
We understand analytical characterization.
We understand transfer-ready development.

That combination makes Xoligo more than a protein supplier.

It makes Xoligo a development partner for the molecular components behind modern biotechnology.

From Protein to Functional System

The future of diagnostics, genetic medicine, and precision biomanufacturing will depend on better components.

Not just better therapeutic candidates.

Better assay proteins.
Better enzymes.
Better controls.
Better standards.
Better antigens.
Better binding proteins.
Better documentation.
Better stability.
Better system integration.

Xoligo Biologics was built for that reality.

Whether your team needs recombinant antigens, assay controls, calibrators, cytokines, receptor proteins, antibody fragments, CRISPR proteins, RNA workflow enzymes, or custom diagnostic components, Xoligo helps produce proteins that are designed for real use.

Because assay-ready does not mean simply purified.

It means ready to perform.