Single-Cell Library Preparation System

What is the Single-Cell Library Preparation System?

A single-cell library preparation system partitions thousands of individual cells into droplets or microwells, barcodes each cell's transcripts and builds sequencing libraries that link molecules to their cell of origin. It is used for cell atlas, tumour heterogeneity and immune profiling studies.

Overview

The system combines a microfluidic or microwell cartridge with reagents that co-encapsulate a single cell, a barcoded gel bead and reverse transcription master mix. Each barcode identifies the cell, and a unique molecular identifier tags each transcript so that PCR duplicates can be removed computationally. After encapsulation, droplets are broken, cDNA is amplified and libraries are built for short-read sequencing with a separate index. Typical runs process 500–10,000 cells in one channel with a target recovery of 50–80% and a multiplet rate that rises with loading. Data are analysed with dedicated pipelines that filter low-quality cells, cluster profiles and annotate cell types. Because the workflow is short and sensitive to handling time, temperature and cell viability, cells should be counted and assessed just before loading.

How does it work?

A sequencing library is a pool of DNA fragments flanked by known adapter sequences that the sequencer recognises. Preparation starts with fragmentation by enzymatic digestion, tagmentation or sonication, which produces a defined size distribution. End repair and 3' adenylation make the ends ligatable, and adapters carrying sample indexes are attached by ligation or added during tagmentation. Size selection with magnetic beads or gel-free methods removes fragments outside the target window, and limited-cycle PCR enriches the library and completes the index sequences. Each step is separated by a magnetic bead cleanup that removes enzymes, salts and short fragments. For RNA libraries, reverse transcription and strand-specific second-strand synthesis precede the same workflow. Quality control after preparation measures concentration by fluorometry and fragment size distribution by capillary electrophoresis.

What are the key features?

• Microfluidic or microwell partitioning of 500–10,000 cells per run
• Barcoded gel beads assign each transcript to a cell
• Unique molecular identifiers correct for PCR duplicates
• Target cell recovery of 50–80% with adjustable loading
• Integrated cDNA amplification and library construction
• Analysis software for cell filtering, clustering and annotation

What are the technical specifications?

A typical single-cell library preparation system configuration offers cells per run of 500–10,000 per channel, cell recovery of 50–80% (target), multiplet rate of approx. 1–10% depending on loading, throughput of up to 8 channels in parallel (model dependent), cell viability required of over 80% (recommended) and cell size range of approx. 5–40 µm (kit dependent). Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Single-Cell Library Preparation System is used in single-cell transcriptome atlases, tumour heterogeneity and clonal analysis, immune cell profiling and receptor sequencing and developmental and stem cell studies. Across the wider Library Preparation Systems class, laboratories also deploy it for whole-genome and exome library construction, RNA sequencing library preparation and single-cell and low-input library workflows.

Which standards and certifications apply?

Relevant standards and methods include ISO 20395, ISO 15189, CLSI MM09, IEC 61010-1 and ISO 17025. Certification candidates for this model are CE, ISO 9001 manufacturing and IEC 61010-1 safety; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Set up library preparation in a pre-PCR room separated from post-PCR and sequencing areas, and use dedicated pipettes, racks and reagents that never leave the room. Contamination from previous libraries shows up as unexpected index combinations, so include a no-template control in every batch and monitor index hopping between runs. Reagents are sensitive to freeze-thaw cycles, so aliquot enzymes and record lot numbers. Validate each new kit or automation script against a reference sample, checking yield, insert size and library complexity before routine use. Because library yield determines sequencing data quality, keep documentation that links each library to its sample, index, kit lot and operator so results can be traced during audits.

How do I select the right Single-Cell Library Preparation System?

Select a single-cell system when biological questions require per-cell resolution rather than bulk averages. Specify cell number per run, channel count, recovery and multiplet targets, supported applications such as gene expression or immune profiling, viability requirements and the analysis pipeline included with the instrument.

How does it compare with other Library Preparation Systems variants?

Begin with the sequencing platform and the input material. Short-read instruments need libraries with adapters matched to their flow cell chemistry, while long-read instruments need high molecular weight input and minimal PCR. Estimate the input amount per sample, because low-input and single-cell workflows require specialised chemistries. Then choose between manual kits for occasional use, magnetic bead automation for 8–96 samples per batch with walk-away operation, and full liquid-handling platforms for hundreds of samples with integrated normalisation and pooling. Check fragmentation method, index type and multiplexing level, size selection method, required equipment such as magnet racks or thermo mixers, and whether the supplier provides validated protocols for your sample type. Manual library preparation is a common source of batch effects, so automation usually pays back where sample numbers are high.