Microneedle-based device for the one-step painless collection of capillary blood samples.

The advancement of point-of-care diagnostics and the decentralization of healthcare have created a need for the simple, safe, standardized and painless collection of blood specimens. Here, we describe the design and implementation of a capillary blood-collection device that is more convenient and less painful than a fingerstick and venepuncture, and collects 100 µl of blood. The technology integrates into a compact, self-contained device an array of solid microneedles, a high-velocity insertion mechanism, stored vacuum, and a microfluidic system containing lithium heparin anticoagulant. The use of the device requires minimal training, as blood collection is initiated by the single push of a button. In a clinical study involving 144 participants, haemoglobin A1c measurements from device-collected samples and from venous blood samples were equivalent, and the pain associated with the device was significantly less than that associated with venepuncture. The device, which has received premarket clearance by the US Food and Drug Administration, should help improve access to healthcare, and support healthcare decentralization.

Explorations of ABO-Rh antigen expressions on erythrocyte dielectrophoresis: changes in cross-over frequency.

A quadrupole dielectrophoretic microdevice was utilized to examine the ABO-Rh dependencies on erythrocyte polarizations. This important step toward medical microdevice technology would transform key clinical blood tests from the laboratory into the field. Previous work in dielectrophoretic microdevices demonstrated that the large number of ABO antigens on erythrocyte membranes impacts their dielectrophoretic signature at 1 MHz. This work explores the dielectrophoretic behavior of native human erythrocytes categorized by their ABO-Rh blood types and directly compares these responses to the same erythrocyte sample modified to remove the A and B antigens. A ß(1-3)-galactosidase enzyme was utilized to cleave the ABO polysaccharide backbone at the galactosidase bonds. The enzymatic reaction was optimized by comparing agglutination of the native and modified blood cells in addition to UV-Vis and HPLC analysis of the reaction effluent for saccharide residues. Next, the dielectrophoretic behaviors of the native and modified erythrocytes were visually verified in a quadrupole electrode microdevice over a frequency range from 100 kHz to 80 MHz. The lower cross-over frequency (COF), which transitions from negative to positive dielectrophoresis, for ABO blood types tested (A+, A-, B+, B-, AB+, O+ and O-) differed over the range from 17 to 47 MHz. The COFs of the corresponding enzyme-modified erythrocytes were also determined and the range narrowed to 29-41 MHz. A second COF in the 70-80 MHz range was observed and was reduced in the presence of the transmembrane Rhesus factor. These results suggest that antigen expression on erythrocyte membrane surfaces influence cell polarizations in nonuniform AC fields.