Objective:

To evaluate a microneedle patch for measuring the kidney injury biomarker neutrophil gelatinase-associated lipocalin in dermal interstitial fluid.

Approach:

• Patch Development: A patch with 121 antibody-coated microneedles was developed to capture neutrophil gelatinase-associated lipocalin from interstitial fluid.
• Testing in Mice: The patch was first evaluated in mice with lipopolysaccharide-induced acute kidney injury, showing increased biomarker levels within four hours.
• Human Testing: In healthy volunteers, paired interstitial fluid and plasma measurements were taken, showing strong correlation despite lower concentrations in interstitial fluid.
• Storage Stability: Patches were coated with zeolitic imidazolate framework-8 to improve storage stability, retaining 94% of fluorescence signal after temperature cycling.

Key Findings:

• Neutrophil gelatinase-associated lipocalin levels increased in interstitial fluid before changes in serum creatinine.
• The assay had a detection limit of 16 pg/mL in mouse samples and 9 pg/mL in human samples.
• The patch left small skin openings that healed within 30 minutes.
• Protected patches maintained assay sensitivity after temperature cycling and transport.

Interpretation:

Interstitial fluid could serve as an alternative matrix for minimally invasive kidney biomarker testing.

Limitations:

• The study did not test the patch in patients with kidney disease.
• The current system requires post-removal processing, not being a fully self-contained test.
• Sample-specific reference ranges are needed due to lower concentrations measured by the patch compared to serum.

Conclusion:

Further studies are required to establish clinically actionable thresholds and assess diagnostic performance in patients.

Sources:

• Advanced Materials