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  2. Biologie de synthèse

Biologie de synthèse

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What is synthetic biology?

Synthetic biology (or synbio) is a rapidly evolving, multidisciplinary scientific field. It can be summarized as the rational design and construction of new biological parts, devices and systems with predictable and reliable functional behaviour, and the re-design of existing, natural biological systems for basic research and practical applications.

There is no single internationally recognised definition of synbio and many definitions coexist (in 2014, the European Commission already listed more than 35 definitions. For information purposes, we quote below two definitions adopted respectively by the European Commission and the Convention on Biological Diversity (CBD), which illustrate the main concepts encompassed by synbio.

  • “Synthetic biology is the application of science, technology and engineering to facilitate and accelerate the design, manufacture and/or modification of genetic materials in living organisms.” (EC, 2014)
  • “Synthetic biology is a further development and new dimension of modern biotechnology that combines science, technology and engineering to facilitate and accelerate the understanding, design, redesign, manufacture and/or modification of genetic materials, living organisms and biological systems.” (CBD, 2016)

 

Synthetic biology extends beyond traditional genetic modification techniques through the use of technologies and tools - often aided by artificial intelligence or machine learning - such as de novo synthesis of entire genomes, CRISPR-based genome editing, gene drive systems, modular design and standardization of biological parts (“biobricks”), creation of non-natural metabolic pathways or chassis organisms, or the use of xeno-nucleic acids (XNAs).

 

Examples of developments in synthetic biology

The following examples illustrate key areas of research where synthetic biology is driving advances with implications for research, industry, healthcare, agriculture and the environment.

  • DNA- and RNA-based circuits

Synthetic biology enables the design of DNA and RNA sequences that act as programmable circuits inside cells. These circuits process biological signals through logic operations, controlling gene expression in response to environmental or metabolic cues. Applications include biosensors for detecting pathogens or environmental contaminants, metabolic status indicators in engineered microbes, and therapeutic gene switches in medicinal applications. Such circuits expand the potential for precise, context-dependent cellular behaviour.

  • Protein engineering

Enzymes, receptors, or structural proteins with tailored properties can be created by modifying existing amino acid sequences, by directed evolution, or by de novo design. Advances include improved catalytic efficiency for industrial enzymes such as engineered PET depolymerases for recycling plastic bottles, chimeric antigen receptors with enhanced cancer cell binding specificity expressed by T-lymphocytes (so-called CAR-T cells), or artificial binding proteins for diagnostics. Protein engineering is central to applications in pharmaceuticals, industrial biotechnology, agricultural applications and environmental remediation.

  • Metabolic pathway engineering

This approach optimises or constructs novel biochemical pathways in micro-organisms or plants to produce valuable compounds. One of the first synbio applications ready for marketing was the semi-synthetic production of artemisinin, an important drug against malaria. In this case, the metabolism of yeast cells is modified for the production of the different biosynthetic enzymes needed for the drug. Another example is the modification of bacteria or yeasts in order for them to produce their essential nutrients from the CO2 in the air, instead of from external sources of organic molecules. The ultimate goal of this research is to capture and fix atmospheric carbon dioxide into useful molecules, in order to mitigate the effect on climate of the atmospheric CO2.

  • Genome-level engineering

Genome-level engineering encompasses top-down and bottom-up approaches, as well as whole-genome improvement.

With top-down engineering, non-essential genes are removed from a whole genome in order to obtain a minimal cell that can continue to function as desired with the smallest possible genome size. This reduces the amount of undesired waste products and the potential for unexpected interactions.

Bottom-up genome engineering, on the other hand, aims at (re-)creating functional organisms with genomes made from synthesized DNA. An example of this is the synthesis of pathogens for research purposes, or the creation of protocells: self-organized, membrane-like structures of polypeptides with a minimal genome, encoding only the necessary components for desired cell functions.

Whole-genome improvement, or genome shuffling, aims at improving the phenotype of organisms, for example in industrially important microbes.

  • Xenobiology

Xenobiology explores the incorporation of non-natural building blocks into biological systems. Examples include synthetic nucleotides beyond the canonical A, T, C, and G, or amino acids with novel chemical properties. These modifications can expand the genetic code and create biomolecules with functions not possible in nature while offering intrinsic bio-containment through genetic incompatibility with natural organisms.

An emerging field within xenobiology is “mirror life”: the synthesis of biomolecules built from mirror-image (chiral-inverted) versions of the naturally occurring D-nucleotides and L-amino acids. Such chiral inversion could yield organisms whose molecular structures are incompatible with natural biochemical processes, creating an additional biosafety barrier, but with increased uncertainty regarding their ability to evade immune recognition or natural predation.

  • Cell-free systems

Cell-free systems are cell extract-based platforms for transcription and translation that enable rapid, flexible engineering of biological circuits without cell-based cloning. Such systems offer greater control over reaction conditions, accelerate development cycles, allow direct programming with DNA or RNA, and support in vitro protein synthesis. Portable diagnostics and biomolecular manufacturing are some examples of areas of research with cell-free systems.

 

Regulatory and biosafety considerations

The risk assessment of synbio organisms should always be conducted on a case-by-case basis. Most synbio organisms fall under the definition of a GMO, and the existing laws, guidances and tools for the risk assessment are therefore applicable, for activities of contained use (EU – Belgium) as well as for deliberate release in the environment (EU – Belgium).

While the risk assessment for the deliberate release of a GMO includes a comparative analysis to its conventional, non-GM counterpart, this approach might not be appropriate for all applications of synthetic biology, including those that do not meet the definition of a GMO. The case-by-case problem formulation approach for risk assessment remains a good starting point, to identify plausible pathways to harm and to determine the type of comparative assessment that may be needed. The main principles of risk assessment — case-by-case evaluation and reliance on scientific evidence — remain applicable, regardless of whether a given application of synthetic biology qualifies as a GMO.

Through several publications, EFSA has assessed the adequacy of the existing GMO risk assessment guidelines for plants, animals and micro-organisms obtained through synthetic biology, and has found them to be generally adequate, with recommendations for potential future refinement and expansion of those guidelines.

 

Biosecurity

Biosecurity deals with the prevention of misuse of biological material such as pathogens or toxins. Some applications of synthetic biology with a potential for increased biosecurity risk include the intentional design of novel pathogens, or the modification for enhanced pathogenicity of existing pathogens.

The management and prevention of such risks requires the involvement of a wide range of stakeholders. A Joint Action work programme of the European Union has issued recommendations for future biosecurity governance, addressing the responsibilities of scientists, research institutions and academia, publishers of scientific journals, funding agencies, professional organizations, the private sector, governments, and international bodies. As with many other frameworks for risk prevention, these recommendations emphasize the need to strengthen education and raise awareness among all actors. They also highlight the importance of systematic screening and identification of research with potential for misuse—whether intentional or accidental—as well as the development of clear procedures and effective communication channels across regulatory levels.

 

References, links and further reading

European Commission:

Joint Action TERROR of the European Union, Work Package 8 - Novel Threats (https://www.jaterror.eu/deliverables/):

EFSA:

Convention on Biological Diversity:

The page for synthetic biology on the website of the Convention for Biological Diversity provides an overview of the latest developments on the subject in the frame of the Convention (https://bch.cbd.int/synbio/). The document “CBD Technical Series No. 100” on synthetic biology, published in 2022, is an extensive analysis of the technical state of play on the subject, as well as of the impacts of synthetic biology on the three objectives of the Convention (namely the conservation of biological diversity, the sustainable use of the components of biological diversity, and the fair and equitable sharing of the benefits arising out of the utilization of genetic resources).

In the frame of the Cartagena Protocol on Biosafety, a guidance was developed in 2024 to support the case-by-case risk assessment of GMOs with engineered gene drives: https://www.cbd.int/documents/CBD/CP/MOP/11/9.

Other EU and member states:

Other: