Waters Aura Systems

Significance of the topic

Particle characterization and reliable identification of aggregates and contaminants are critical for biopharmaceutical development, QC, and release decisions. Misidentification of subvisible and visible particles (e.g., protein aggregates, cells, viral capsids, degraded excipients, and polymeric fragments) can lead to incorrect formulation or process changes, regulatory delays, and safety risks. High-throughput, low-volume, and automation-compatible analytical approaches that combine morphological and molecular (fluorescence) information improve certainty in particle identity and enable continuity from early research to late-stage QC.

Objectives and overview of the system

The Aura product family provides membrane-based imaging solutions for quantitative detection and identification of visible and subvisible particles with minimal sample volume. Key objectives are to:

• Deliver accurate counts and identity for particles >1 µm across biologics, gene therapies, and cell therapies.
• Differentiate proteinaceous from non-proteinaceous particles and distinguish cells, viral capsids, polysorbate degradation, and plastics.
• Support high-throughput workflows, small-volume assays (as little as 5 µL), and automation-ready operation suitable for development and QC environments.

Methodology and analytical principles

Aura systems integrate three complementary imaging approaches:

• Brightfield Membrane Imaging (BMI): Captures a background image of a membrane before filtration and a sample image after filtration; background subtraction yields high-contrast particle images with sizes calibrated against ASTM standards. This fluidics-free membrane method amplifies contrast (~10× vs liquid imaging) and yields automated, reproducible particle detection.
• Fluorescence Membrane Microscopy (FMM): Applies fluorescent dyes or conjugated antibodies either in solution or on-membrane to label specific particle classes (protein dyes, DNA dyes, capsid- or particle-targeted antibodies). FMM overlays fluorescence channels onto BMI-detected particle locations to provide molecular-specific identification and multiplexed discrimination in heterogeneous samples.
• Side Illumination Membrane Imaging (SIMI): Enhances detection and characterization of non-biological/inorganic particles (e.g., beads, glass, fibers) by providing orthogonal contrast information to distinguish these from biological particulates.

Used instrumentation

The Aura portfolio includes multiple configurations (Aura, Aura+, AuraGT, AuraPTx, AuraCL, Aura BMI) tailored for specific workflows (biologics SVP analysis, gene therapy, cell therapy). Representative specifications:

• Imaging area: 24.6 mm2
• Illumination: Brightfield LED 455 nm; side scatter LED 465 nm; multiple fluorescence LEDs with instrument-dependent excitation/emission channels (e.g., Ex 440/40–Em 500/40 nm; Ex 488/50–Em 544/24 nm; other options and custom channels available).
• Resolution: 1.0 pixel/µm; particle detection threshold >1 µm.
• Dynamic capability: >3,000,000 particles/mL at 1.6 µm; sampling efficiency reported as 100%.
• Sample formats: 24-well or 96-well filter membranes (white polycarbonate for brightfield, black polycarbonate for fluorescence).
• Throughput: Brightfield (BMI) read ~1 min/sample; fluorescence (FMM) read 15–30 s/sample.
• Minimum sample volume: 5 µL (assay dependent); robotic compatibility for automation.

Main results and discussion

The Aura approach yields several practical performance outcomes:

• High specificity in particle ID: Combining morphology with fluorescence labeling reduces misclassification events that plague morphology-only methods (e.g., protein aggregates vs polymer fragments or ETFE plastics).
• Multiplexed discrimination: FMM enables simultaneous detection of protein, DNA (e.g., SYBR Gold for AAV genome leakage), capsid markers, cell markers, and other targeted labels—critical for gene therapy stability studies and payload leakage monitoring.
• Quantitative linearity and sensitivity: Demonstrated excellent linearity across serial dilutions (R2 > 0.99) and reproducible counting across microliter volumes, enabling triplicate analysis with minimal sample consumption.
• Expanded material characterization: SIMI provides additional contrast to resolve inorganic particulates (Dynabeads, glass, fibers), complementing BMI’s biological particle detection.
• Practical workflow continuity: Single-method transferability from discovery to QC, supported by automated image analysis (ParticleVue software) and the ability to pool well-level data for larger-sample analyses.

Benefits and practical applications

Primary benefits for laboratories and development pipelines include:

• Reduced ambiguity in particle identification, lowering the risk of unnecessary formulation or process interventions.
• Very low sample consumption (down to 5 µL) enabling analysis of precious samples (e.g., early-stage biologics, AAV preps) and retention of material for orthogonal testing.
• High throughput and automation readiness suitable for formulation screening, stability studies, lot release, and in-process monitoring.
• Multiplexed assays for targeted questions (DNA leakage in AAV, polysorbate degradation products, cell aggregates in cell therapy products) facilitating focused stability and safety assessments.
• Compatibility with standard membrane formats and robotic platforms simplifies integration into existing laboratory workflows.

Future trends and opportunities

Likely developments and applications for membrane-based fluorescence particle analysis include:

• Deeper multiplexing: Broader panels of fluorescent probes and antibody conjugates to simultaneously map multiple biomarkers on individual particles or aggregates.
• Integration with advanced data analytics: Machine learning applied to combined morphology and fluorescence features for improved classification, automated anomaly detection, and predictive stability modeling.
• Regulatory uptake and standardization: Validation against compendial methods (e.g., USP) and increased acceptance of fluorescence-based particle ID in QC and lot release frameworks.
• Expanded use in novel modalities: LNP characterisation, more extensive AAV serotype stability mapping, and routine QC for cell and gene therapies as these modalities mature commercially.
• Miniaturization and higher throughput: Further reductions in sample volume per assay and higher-density membrane formats for large screening campaigns.

Conclusion

Aura systems combine membrane imaging and fluorescence labeling to deliver high-confidence particle identification and quantitation for biologics, gene therapies, and cell therapies. The fluidics-free, membrane-based workflow provides strong contrast, low sample consumption, multiplex capabilities, and automation compatibility—addressing common pitfalls of morphology-only systems and enabling consistent methods across development and QC. These strengths make Aura suitable for stability testing (including AAV DNA leakage), formulation screening, and routine particle surveillance in regulated laboratory environments.

Reference

Waters Corporation. Aura Particle Analysis Systems — Product literature and technical specifications. Milford, MA; 2026.