AixCrea: Continuous Biosensing for Acute Kidney Injury

AixCrea is a point-of-care continuous electrochemical biosensor designed to monitor creatinine levels in real-time, enabling early detection of Acute Kidney Injury (AKI) in Chronic Kidney Disease (CKD) patients and kidney transplant recipients. Developed by Team AixSense for the international SensUs 2024 competition, the project was awarded 1st Place in the Business Translation Award and 2nd Place in the Innovation Award.

Project Document: Download Team Results Document (PDF)
Team Platform: aixsense.de
Affiliations: RWTH Aachen University, IWE1 Institute, TMDU, Uniklinikum Aachen

Project Showcase & Demonstration Video

Clinical Motivation & Diagnostic Gap

Chronic kidney disease affects over 10% of the global population, with acute kidney injury carrying up to a 42% mortality rate in vulnerable cohorts. Serum creatinine is the gold-standard metabolic biomarker for renal clearance:

• Sudden creatinine elevations indicate acute renal decline, drug nephrotoxicity, or organ rejection in transplant recipients.
• Traditional centralized lab testing introduces hours of turnaround delay, missing critical therapeutic windows.
• AixCrea provides continuous, decentralized, and label-free creatinine monitoring at the point of care.

Transduction Principle & Metal-Organic Frameworks (MOF)

The biosensing mechanism couples Electrochemical Impedance Spectroscopy (EIS) with a metal-organic framework molecular recognition interface:

[ Electrolyte Sample: Creatinine Analyte ]
                   │
                   ▼
     ┌───────────────────────────┐
     │  Cu-HHTP MOF Thin Film     │  Selective Cu(II)-Creatinine Coordination
     ├───────────────────────────┤
     │  Au / Ti Thin Film Layer  │  Direct Electron Transfer
     ├───────────────────────────┤
     │  Glass Wafer Substrate    │
     └───────────────────────────┘

1. Molecular Recognition via Cu-HHTP

• The working electrode (WE) is modified with Cu-HHTP (2,3,6,7,10,11-hexahydroxytriphenylene), a 2D conductive MOF.
• Copper(II) coordination sites within the porous lattice selectively bind creatinine through nitrogen coordination complexes.
• Complexation alters the local charge distribution, modifying interfacial capacitance and charge-transfer resistance ($R_{ct}$).

2. Randles Equivalent Circuit Modeling

The electrode-electrolyte interface is quantified through AC impedance fitting:

Where:

• $R_s$: Uncompensated solution / electrolyte resistance.
• $C_{dl}$: Electrical double layer capacitance at the functionalized electrode boundary.
• $R_{ct}$: Charge-transfer resistance across the Cu-HHTP coordination manifold.
• $Z_W$: Warburg impedance accounting for mass diffusion at lower frequency limits.

Microfluidic Cartridge & Embedded Instrument

Multi-Layer PDMS Microfluidic Architecture

• Fabricated by vacuum-casting polydimethylsiloxane (PDMS) into 3D DLP-printed high-resolution resin master molds.
• Integrates a Staggered Herringbone Micromixer (SHM) to create chaotic advective mixing across laminar streamlines, ensuring uniform analyte exposure across the $70\,\mu\text{L}$ active detection volume without relying solely on passive diffusion.

Readout & Embedded Firmware

• Powered by the Analog Devices ADuCM350 high-precision impedance network analyzer and potentiostat on an integrated ARM Cortex-M3 core.
• Configurable for dynamic AC frequency sweeps, cyclic voltammetry (CV), and amperometric profiling.
• Transmits telemetry to a dedicated GUI for clinical real-time trend visualization and threshold alarm processing.

Translation Potential & Impact

• Unit Economics: Designed for high-volume roll-to-roll manufacturing with an estimated sensor consumable unit cost of ~€60.
• SensUs 2024 Accolades:
  • 1st Place: Business Translation Award
  • 2nd Place: Innovation Award