Next-generation sequencing (NGS): principles and challenges

Next-generation sequencing (NGS) has profoundly transformed molecular biology by enabling rapid, massive, and cost-effective genome analysis. By 2025, this technology has become essential in many fields, ranging from personalized medicine to ecology, including cancer research and rare diseases. Its ability to generate precise and voluminous data has enabled unprecedented advances, but also poses new technical, ethical, and financial challenges. At a time of increasing technological innovations, how does NGS continue to push the boundaries of science while remaining accessible? What are its practical applications and major challenges for research and healthcare? In this article, we will explore in detail the operating principle of NGS, its techniques, its varied uses, and its challenges, incorporating the latest advances in a rapidly expanding sector. The objective is to understand how this revolutionary method is shaping the genomics of today and tomorrow, with its promises, but also its limitations. The Fundamental Principles of Next-Generation Sequencing

The core of next-generation sequencing lies in its ability to analyze millions of DNA or RNA fragments in parallel, enabling it to produce massive amounts of data in record time. Unlike the Sanger method, which sequenced one by one, NGS uses parallel techniques, making it possible to process entire genomes in very short timeframes.

This process begins with the fragmentation of DNA or RNA. Specific adapters are then added to each end of the fragments. These adapters serve a dual purpose: they facilitate the attachment of the fragments to a solid surface and enable their amplification. The next crucial step involves clonal amplification—often by PCR—to increase the quantity of each fragment, making it easier to read later.

Sequencing itself relies on several methods, including next-generation synthesis and oligonucleotide ligation. These techniques use fluorescent or electrical signals to identify each nucleotide as it is incorporated or hybridized. Once the reading is complete, bioinformatics software assembles all these small sequences, providing a comprehensive view of the genome or RNA being analyzed. Key steps in the NGS process

🔪 DNA or RNA fragmentation

🧬 Addition of specific adapters

• 🔗 Clonal amplification, often by PCR
• 🧪 Parallel sequencing: synthesis or ligation
• 💾 Data analysis and assembly via bioinformatics
• This precise and rapid chain of steps allows the production of millions of reads that will be processed by sophisticated algorithms to obtain a faithful and usable sequence. This massively parallel process is the basis for all the advances in NGS, enabling in particular the detection of mutations or the understanding of genetic diversity worldwide.
• The different next-generation sequencing techniques in detail

NGS techniques are varied, each adapted to specific applications, with their own advantages and limitations. Among them, two main methods dominate the market: sequencing by synthesis (SBS) and sequencing by ligation (SBL). Other innovative techniques, such as nanopore real-time sequencing or sequencing by synthesis from Oxford Nanopore Technologies, are also beginning to gain traction.

Sequencing by synthesis (SBS)

SBS, developed by Illumina, is currently the most widely used technique. It relies on the sequential incorporation of fluorescent nucleotides, detected by a sophisticated optical system. After binding the fragments to a solid surface, each incorporation cycle produces a specific color for each base. These signals are recorded, and the software then constructs the sequence. The advantages of SBS:

🎯 High precision

🕒 Reliable results, suitable for clinical analyses

💻 Broad compatibility with numerous bioinformatics software

• However, SBS also requires longer processing time and is expensive, which remains a barrier for certain large-scale applications. Companies like Roche and Agilent Technologies are constantly working to improve these parameters to further reduce the cost per sequence.
• Sequencing by Ligation (SBL)
• The SBL technique is valued for its speed. It uses small oligonucleotides that hybridize to the target DNA, then ligate to reveal the sequence. Detection is achieved by reading the hybrid signals, enabling high-throughput sequencing, ideal for metagenomic studies or the diagnosis of complex diseases.

Strengths:

⚡ High processing speed

💰 Lower cost in large quantities

🤏 Suitable for sequencing large environmental samples

• However, the limitation of SBL lies in its slightly lower precision, especially for the analysis of individual bases. The medicine of tomorrow will likely see a combined use of these methods to exploit their respective strengths.
• Real-time sequencing innovations with Oxford Nanopore Technologies
• Nanopore sequencing represents a major advance, using synthetic or biological nanopores to directly read the bases of a DNA or RNA chain without prior preparation. Real-time analysis allows for instant observation of a sample’s composition, a real asset in emergency diagnostics or field analyses.

This original process also offers the possibility of sequencing very long molecules, well beyond traditional limits, paving the way for unprecedented structural studies. Oxford Nanopore Technologies, with its MinION devices, facilitates access to this technology for a variety of applications, including for community researchers and field practitioners. The Major Challenges of Next-Generation Sequencing in 2025

While NGS has experienced exponential growth, it now faces several challenges. On the one hand, the management, storage, and analysis of massive amounts of data are becoming a logistical and technological challenge. On the other, the reliability of results and cost reduction remain key concerns for the industry.

Technical and Ethical Challenges

🔍 Guaranteeing the accuracy and reliability of sequences, with a decreasing error rate thanks to new platforms such as those from Illumina and PacBio.

🖥️ Bioinformatics Challenges: Assembling and interpreting gigabytes of data requires powerful infrastructures and increasingly sophisticated algorithms, such as those used by Genomatix and Qiagen.

⚖️ Ethical questions regarding the confidentiality and security of genetic data, particularly with projects involving the sequencing of entire populations.

Financial and regulatory issues

• 💸 Cost reduction remains strategic to further democratize its use, particularly through the optimization of techniques, in partnership with leaders such as BGI and Roche.📜 Regulations, particularly regarding the Protection of Personal Health Data, are constantly evolving to govern these technologies. 💡 The key to success also lies in the integration of automated solutions, such as biotechnology automation, to accelerate the implementation of large-scale projects (more information here). The main applications of next-generation sequencing in research and medicine The diversity of uses for NGS is impressive. In medicine, it is revolutionizing diagnostics, particularly in the treatment of cancers, rare diseases, and infectious diseases. In biology, it allows us to decipher biodiversity, study the microbiome, and better understand the evolution of species.
• Human Genomics and Personalized Medicine
• In 2025, whole genome sequencing will foster precision medicine. Some laboratories are already using platforms such as those from Illumina, Roche, and Qiagen to detect rare or complex mutations, particularly in targeted therapies for cancer or rare genetic diseases.

Studies show that no mutation should be left to chance: complete sequencing allows treatment to be tailored to the patient’s specific genetic characteristics, thus reducing side effects and improving efficacy.

• Applications in Microbiology and Ecology
• In the environmental field, metagenomics is becoming a real tool for exploring microbial biodiversity. Massively parallel sequencing helps analyze water, soil, or air samples to identify little-known microorganisms or detect the presence of pathogens. BGI, along with Oxford Nanopore and Agilent Technologies, are competing to provide innovative tools for these large-scale analyses.
• Challenges for cancer research and epidemiologyNGS enables the early detection of specific mutations, providing a better understanding of tumor mechanisms. The identification of biomarkers aids in the development of innovative and personalized treatments. Pharmaceutical companies, notably Roche and PadBio, are investing heavily to make these techniques more accessible and faster.Future challenges and prospects for sequencing by 2025

Despite everything, the road is still long. The demand for infrastructure, trained specialists, and data processing software remains very high. Collaboration between industry, universities, and startups is essential to continue advancing this field.

Innovations such as the miniaturization of devices (e.g., the Oxford Nanopore portable repeaters) or the integration of artificial intelligence into bioinformatics analysis already offer promising prospects. The key also lies in the democratization of these tools for universally accessible medicine, including in remote or low-resource areas.

The challenges of artificial intelligence and the cloud

☁️ Harnessing the potential of the cloud to store and process data on a large scale

🤖 Developing AI algorithms to improve diagnostic accuracy

🧠 Ensuring ethical and transparent oversight of the use of AI

Frequently asked questions about next generation sequencing in 2025

What is the average cost of sequencing a human genome in 2025?

The price has decreased considerably, with an estimate around 300 to 500 euros, thanks to technological progress made by Illumina, PacBio or Oxford Nanopore Technologies.

Can NGS detect all mutations?

Although very powerful, NGS still has limitations, particularly for certain types of complex rearrangements or in difficult-to-read regions, but innovations continue to narrow these shortcomings.

What are the main uses in the clinic?

Mainly accurate diagnosis of mutations, precision medicine, early detection, and monitoring the progression of diseases such as cancer or infectious diseases.

1. How to guarantee the security of genomic data?
2. By adopting strict protocols and using secure infrastructures, with the collaboration of players like Qiagen or Roche, to respect the privacy of patients.