An in Vivo Blood Microsampling Device for Pharmacokinetic Applications

This paper describes an
in vivo
microsystem for automated blood microsampling from a lab mouse for pharmacokinetic (PK) studies. Intended to be mounted as a "backpack" on a mouse, it uses a micro-needle, reservoir, and an actuator. It is designed to suddenly prick the animal for a time-point sample, minimizing the potential impact of stress-related endocrine changes. The blood is collected by the 33-gauge micro-needle(210 μm OD) into the ≈1 μL micro-electro-discharge machined steel reservoir. The small volume enables repeated sampling, permitting a full PK profile to be obtained from a single mouse. The voice coil actuator provides a peak force of ≈170 mN, which can easily pierce the needle through mouse skin. The device was tested for blood vessel sampling using a mock vessel with adjustable pressure, and the reservoir was filled in <0.15 sec by a combination of the capillary effect and blood pressure. For interstitial fluid sampling, the capillary effect of the needle inner surface was enhanced by electropolishing. Blood from fresh bovine tissue was collected into the reservoir to simulate interstitial fluid sampling.