Aura CL System

Significance of the topic

The reliable detection, counting and characterization of cellular aggregates, protein aggregates and subvisible particles is critical for quality control in cell therapy and biopharmaceutical manufacturing. Robust, high-throughput methods that operate on low sample volumes and provide composition-specific information (cell vs non-cell, viable vs non-viable) help ensure product safety, efficacy and process consistency while reducing assay time and consumable use.

Objectives and study overview

This specification sheet presents the design and intended performance of the Aura CL System, a benchtop instrument created to perform high-throughput quantitation and identification of cellular aggregates and subvisible particles in a 24- or 96-well filter membrane format. The system aims to deliver 100% sampling efficiency, composition discrimination (cellular vs protein vs extrinsic), and rapid per-sample read times without fluidic flowlines that can clog or require cleaning.

Methodology and Instrumentation

The Aura CL employs a combination of three complementary imaging techniques to detect and characterize particles retained on membrane filters:

• Backgrounded Membrane Imaging (BMI) — full-well brightfield imaging optimized for counting and morphological analysis with complete sampling of the membrane area.
• Fluorescence Membrane Microscopy (FMM) — two fluorescence channels used for compositional ID (cell-specific dyes, viability markers, protein stains) and for differentiating particle classes.
• Side Illumination Membrane Imaging (SIMI) — side-scatter style illumination to enhance contrast for small or low-contrast particulates.

Key instrument specifications summarized:

• Imaging area: 24.6 mm2 per well.
• Objectives: 4x and 10x optical options; 4x provides 100% sampling efficiency.
• Resolution: ~1.0 pixel/µm.
• Detectable equivalent circular diameter (ECD) range: lower limit >1 µm, upper limit <5 mm.
• Minimum sample volume: ~5 µL (assay dependent).
• Illumination: Brightfield LED at 455 nm; side-scatter LED at 465 nm; two fluorescence excitation/emission channel pairs (Ch1 Ex 440 nm / Em 500 nm; Ch2 Ex 376 nm / Em 440 nm).
• Read times: Brightfield (BMI) ≈ 1 minute per sample; Fluorescence (FMM) ≈ 30 seconds per sample.
• Sample format: 24- or 96-well filter membrane plates with two membrane types — white polycarbonate for brightfield and black polycarbonate for fluorescence.
• Software: Particle Vue 5.x for image acquisition and analysis.
• Robotic compatibility and Windows OS; universal power input; instrument footprint ~13.5 × 18 × 13 in and weight ≈57 lb.

Instrumentation used

The specification identifies the following instrument and consumable elements:

• Aura CL System (Waters Corporation) incorporating BMI, FMM and SIMI optical modules.
• Optical objectives: interchangeable 4x and 10x lenses.
• LED illumination sources at specified wavelengths for BF, SIMI and two fluorescence channels.
• Filter membrane plates (24- or 96-well) with white polycarbonate membranes for brightfield imaging and black polycarbonate membranes for fluorescence imaging.
• Particle Vue 5.x software for capture and automated image analysis.

Main results and discussion

As a product specification, the document reports intended capabilities rather than experimental datasets. From the provided metrics the system is positioned to deliver:

• High-throughput throughput: per-well read times compatible with plate-scale workflows (≈1 min BF, 0.5 min FL), enabling rapid screening of dozens to hundreds of wells per run.
• Complete sampling: 100% sampling efficiency with the 4x objective reduces statistical uncertainty linked to subsampling and improves detection sensitivity for rare aggregates.
• Composition discrimination: dual-channel fluorescence plus morphology and scatter contrast enable straightforward separation of cellular aggregates from protein or extrinsic particulates and support viability and cell-type assays.
• Low sample volume: capability to operate with as little as 5 µL supports precious cell therapy samples and limited-material studies.

Potential limitations and practical considerations include:

• Lower detection limit is approximately 1 µm ECD; detection of smaller nanoparticles or molecular-scale aggregates is outside the instrument's stated range.
• Fluorescence channels are specified with fixed excitation/emission pairs; dye selection should be matched to these channels or require validation with alternative filters if needed.
• Consumable dependence: membrane-based capture simplifies optics and avoids fluidics but introduces ongoing costs and handling steps (filtration, membrane handling).

Benefits and practical applications of the method

The Aura CL System's combination of full-well imaging, compositional fluorescence, and membrane-based sampling offers several practical advantages:

• Quality control for cell therapies: direct identification and quantitation of cellular aggregates and subvisible particulates supports release testing and in-process monitoring.
• Formulation and stability studies: rapid screening of protein aggregation and particulate load across conditions.
• Viability and phenotyping assays: fluorescence capability enables viability stains and cell-type markers to be integrated into particulate analysis.
• High-throughput process development: compatibility with 96-well formats and robotics facilitates automated workflows and higher experimental throughput.

Future trends and possible applications

Potential developments and extensions that would enhance utility and market fit include:

• Expanded fluorescence capacity: additional channels or tunable filters would broaden compatible dyes and multiplexing of cell- and aggregate-specific labels.
• Integrated AI/ML classification: deeper machine-learning models trained on curated datasets could further automate ID of aggregate subtypes and reduce user intervention.
• Tighter LIMS/manufacturing integration: direct data pipelines for electronic batch records and QC reporting to streamline regulated workflows.
• Lowering detection limits: optical or sampling innovations to extend sensitivity below 1 µm for nanoparticle and early aggregation detection.
• Consumable optimization: reusable or lower-cost membrane designs to reduce running costs and environmental footprint.

Conclusion

The Aura CL System is designed as a purpose-built, high-throughput platform for quantifying and differentiating cellular aggregates and subvisible particles in cell therapy and biologics contexts. Its full-well membrane imaging approach provides complete sampling, while dual-channel fluorescence and side-illumination contrast enable compositional discrimination and viability assays. The instrument balances throughput, low-volume operation and ease-of-use for QC and R&D applications, with foreseeable improvements centering on expanded fluorescence flexibility, advanced analytics and deeper automation.

Reference

Waters Corporation. Aura CL System specification sheet. October 2025. Waters Corporation, Milford, MA. Product specification and feature summary.