Digital Microneedles for Multiplexed Transdermal Sensing via Fluorescent QR Codes.

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Materials Science

Background:

• Current biosensors face challenges like signal drift and calibration needs for in vivo monitoring.
• Wearable and transdermal biosensors have limited multiplexing capabilities.
• Real-time biochemical sensing is crucial for advancing precision medicine.

Purpose of the Study:

• To develop a novel digital biosensing platform using microneedles.
• To overcome limitations of existing transdermal biosensors, including calibration requirements and signal drift.
• To enable calibration-free, multiplexed in vivo biochemical detection.

Main Methods:

• Introduction of digital fluorescent microneedles employing threshold-activated probes.
• Microneedles function as binary fluorescent switches, activating above specific analyte thresholds.
• Development of biodegradable microneedles with a "baby-bottle" design for reliable skin insertion and tip detachment.
• Rational engineering of fluorescent probes with discrete activation thresholds for pH and glucose detection.
• Tuning probe loading for reproducible threshold activation and digital encoding.

Main Results:

• Achieved fully digital, multiplexed detection of pH and glucose in skin.
• Demonstrated high classification accuracies: 93% for pH and 85% for glucose.
• Established a QR code-based output for direct, quantitative biochemical information.
• Validated the robustness of microneedles against tissue heterogeneity and environmental noise.
• Showcased the broad extensibility of the digital encoding concept to other biomarkers.

Conclusions:

• Digital fluorescent microneedles offer a scalable route to calibration-free, multiplexed biosensing in vivo.
• The QR-based output facilitates decentralized diagnostics and integration into digital health workflows.
• This technology presents a versatile and clinically relevant platform for advanced transdermal biosensing.