Self-powered microneedle-based biosensors for pain-free high-accuracy measurement of glycaemia in interstitial fluid

In this work a novel self-powered microneedle-based transdermal biosensor for pain-free high-accuracy real-time measurement of glycaemia in interstitial fluid (ISF) is reported. The proposed transdermal biosensor makes use of an array of silicon-dioxide hollow microneedles that are about one order of magnitude both smaller (borehole down to 4 µm) and more densely-packed (up to 1×106 needles/cm2) than state-of-the-art microneedles used for biosensing so far. This allows self-powered (i.e. pump-free) uptake of ISF to be carried out with high efficacy and reliability in a few seconds (uptake rate up to 1 µl/s) by exploiting capillarity in the microneedles. By coupling the microneedles operating under capillary-action with an enzymatic glucose biosensor integrated on the back-side of the needle-chip, glucose measurements are performed with high accuracy (±20% of the actual glucose level for 96% of measures) and reproducibility (coefficient of variation 8.56%) in real-time (30 s) over the range 0–630 mg/dl, thus significantly improving microneedle-based biosensor performance with respect to the state-of-the-art

An optical microsystem based on vertical silicon-air Bragg mirror for liquid substances monitoring

In this work, an integrated optical microsystems for the continuous detection of flammable liquids has been fabricated and characterized. The proposed system is composed of a the transducer element, which is a vertical silicon/air Bragg mirror fabricated by silicon electrochemical micromachining, sealed with a cover glass anodically bonded on its top. The device has been optically characterized in presence of liquid substances of environmental interest, such as ethanol and isopropanol. The preliminary experimental results are in good agreement with the theoretical calculations and show the possibility to use the device as an optical sensor based on the change of its reflectivity spectrum

TOWARDS PAIN-FREE AND HIGH-ACCURACY POINT-OF-CARE GLYCEMIC CONTROL USING CAPILLARITY-DRIVEN MICRONEEDLES

In this work, a novel class of self-powered microneedle-based transdermal biosensors for pain-free and high accu- racy measurement of glycaemia in interstitial fluid (ISF) is reported. Autonomous, effective, and fast uptake of interstitial fluid is demonstrated by exploiting capillarity in silicon dioxide microneedles with diameter of a few micrometers and density of thousands needles/cm2. Further, high accuracy and high reproducibility real-time measurement of glucose concentration in ISF is demonstrated by coupling the microneedles with an enzymatic glucose biosensor, achieving Food and Drug Administration (FDA) approved performance in-vitro. Finally, an easy-to-use handy glucometer exploiting the microneedles operating under capillary-action for (future) effective point-of-care glycaemic control is designed, fabricated, and validated in-vitro

In-situ label-free optical detection of cells cultured in 3D microincubators

In this work, we show that high aspect-ratio silicon microstructures can play, at the same time, the roles of a cell-selective three-dimensional microincubator for cell culture and optical label-free transducer of cell morphology mapping. Silicon microincubators, integrating a periodic array of narrow (5-μm-wide), deeply etched (50-μm-deep) gaps separated by 3-μm-thick silicon walls, are fabricated by electrochemical micromachining (ECM) technology [1], and used for culturing several both epithelial and mesenchymal cell lines. Fluorescence microscopy analyses highlight that the microincubator shows cell-selective capabilities, being mostly cells with mesenchymal phenotype able to actively colonize the deeply etched gaps and grow attached to the vertical silicon walls [2]. The microincubator also features reflectivity spectral properties typical of one-dimensional (1D) photonic crystals (PhCs) structures in the near infrared range, with high reflectivity regions separated by deep reflectivity notches. According to 1DPhC optical properties, the presence of cells inside the gaps of the microincubator strongly affects the reflectivity signal, which can be measured in-situ with a fiber-optic setup orthogonally to the silicon wall surface (x-y plane). By spatially mapping the reflected power spectrum in the vertical x-y plane, it is thus possible to infer on the extension of cells growing into the microincubator attached to silicon walls. In particular, the intensity ratio between reflectivity maximum and minimum at two different wavelengths around 1.55 μm is closely related to the cell spreading on the silicon wall inside the deeply etched gaps of the microincubator. These results clearly envisage future in-situ label-free analyses of cellular activities involving changes in cell morphology and/or adhesion (e.g. apoptosis), in a three-dimensional environment. [1] M. Bassu, S. Surdo, L. M. Strambini, G. Barillaro, Adv. Funct. Mat., 22 (2012), 1222-1228; [2] F. Carpignano, G. Silva, S. Surdo, V. Leva, A. Montecucco, F Aredia, A. Scovassi, S. Merlo, G. Barillaro, G. Mazzini, Plos ONE 7 (2012) DOI: 10.1371/journal.pone.0048556

TOWARDS PAIN-FREE AND HIGH-ACCURACY POINT-OF-CARE GLYCEMIC CONTROL USING AUTONOMOUS MICRONEEDLE-BASED SYSTEM

Microneedle systems able to measure glucose concentration in interstitial fluid (ISF) have been recently proposed for pain-free glycaemic control, as an alternative to standard finger-prick systems, following the demonstration that glucose concentration in ISF parallels that in blood, though with a delay time of 10-20 minutes. In fact, besides use of microneedles for transdermal drug delivery applications [1], in the last years an increasing number of studies is being published on their use for transdermal biosensing applications both in-situ and ex-situ, among which glucose monitoring in peripheral blood and ISF is a major target [2]. In this work, a novel class of self-powered microneedle-based transdermal biosensors for pain-free and high accuracy measurement of glycaemia in ISF is reported. Microneedle chips (silicon die 0.5 cm x 0.5 cm) integrating a two-dimensional array of silicon-dioxide hollow needles protruding from the front-side and in connection with a reservoir (18 µL volume) grooved on its back-side are designed, fabricated, and tested. The microneedles feature different pitch p (16 µm@type#A and 10 µm@type#B) and internal diameter d (6 µm@type#A and 4 µm@type#B), but same protruding length (100 µm) and inner lumen length (200 µm)