Deterministic DNA barcoding using vacuum-driven loading of free oligonucleotides to microwell arrays.

Area of Science:

• Biotechnology
• Genomics
• Microfluidics

Background:

• High-throughput sequencing requires cost-effective sample pooling.
• Current DNA barcoding methods using beads in droplets/microwells are intensive and prone to errors.
• Unambiguous sample identification is crucial for pooled sequencing.

Purpose of the Study:

• To develop a deterministic, bead-free DNA barcoding strategy for arrayed microwells.
• To improve efficiency and reduce reagent use in sample barcoding for next-generation sequencing.
• To enable accurate identification of pooled samples in micro-scale formats.

Main Methods:

• Utilized a multi-layer, vacuum-driven microfluidic network for deterministic loading of oligonucleotide solutions into 512 arrayed microwells.
• Employed a Combinatorial Dual Indexing (i5, i7) scheme for unique barcode assignment.
• Implemented vacuum-assisted flow and dead-end channel design for uniform barcode patterning.

Main Results:

• Achieved uniform barcode patterning in microwells with approximately 20% coefficient of variation.
• Demonstrated reasonable barcode loading times (30-40 min per step) and reduced reagent consumption compared to bead-based methods.
• Reported low cross-contamination rates (approximately 4%) and successful on-chip PCR of DNA from a breast cancer cell line (MCF7).

Conclusions:

• The developed deterministic, bead-free DNA barcoding strategy is efficient for arrayed microwells.
• This method offers an alternative to intensive bead-based synthesis and random seeding.
• The approach supports accurate sample identification for high-throughput sequencing applications.