A. Caliò

Optically monitored drug delivery patch based on porous silicon and polymer microneedles

Fabrication and characterization of an optically monitored hybrid patch for local administration of drugs, based on polymeric micro-needles and a porous silicon free-standing membrane, are reported. The micro-needles are realized by an innovative photolithographic approach that allows fine tuning of geometrical parameters, using polyethylene glycol and a commercial photo-catalyzer. The porous silicon multilayer not only increases the storage of a relevant amount of the drug, but also offers a continuous, naked-eye monitoring of the drug delivery process. As a proof-of-concept experiment, we report our results on the release of a dye molecule (fluorescein, 332 Da) in a phosphate saline buffer.

Glucose sensing electrode system based on polymeric microneedles

Microneedles are largely applied in biomedicine, both in diagnostics and therapeutics, since they can be considered the perfect interface between patient and sensing/dispensing devices. In this paper, we present an electro-chemical biosensor based on polymeric microneedles array for the measure of glucose level in interstitial fluids. The microneedles array has been fabricated by photolithography of a polymer, PolyEthylene Glycol DiAcrylate hydrogel, mixed with an enzyme, Glucose oxidase, and a redox mediator, the Vynilferrocene. The microneedles array acts as a working electrode when gold plated by sputtering and their tips have been etched to create a sensitive area. The redox reaction with glucose creates a charge transfer, enhanced by the redox mediator, resulting in a current proportional to the glucose concentration.

Diagnostic and therapeutic devices based on polymeric microneedles: fabrication and preliminary results

Applications of microneedles in biomedicine wide range from diagnostics to therapeutics. This crucial and versatile tool is the interface between the human body and often a complicated device. We present two sensing device based on hybrid microneedles array for diagnostic and therapeutic applications. The hybrid microneedles was fabricated by using a commercial photocatalyzer to solidify a liquid PolyEthylene Glycol hydrogel. After polymerization, the MNs have a porous structure, which can include a variety of biological molecules, as bioprobes or drugs. The first device presented is an electrochemical sensor where microneedles include enzymes in their matrix that interact with glucose. It is fabricated by plating with gold the MNs and etching their tips. The redox reaction with glucose, mediated by ferrocene, creates a charge transfer resulting in a current proportional to the glucose concentration. The second device is a therapeutic tool with an optically controlled release of drugs. In this case the device includes a porous silicon membrane with a Braggs mirror, whose reflection wavelength is related to the drugs concentration in the MN.

Hybrid microneedles devices for diagnostic and therapeutic applications: fabrication and preliminary results

Microneedles are newly developed biomedical devices, whose advantages are mainly in the non-invasiveness, discretion and versatility of use both as diagnostics and as therapeutics tool. In fact, they can be used both for drugs delivery in the interstitial fluids and for the analysis of the interstitial fluid. In this work we present the preliminary results for two devices based on micro needles in PolyEthylene (Glycol). The first for the drugs delivery includes a membrane whose optical reflected wavelength is related to the concentration of drug. Here, we present our preliminary result in diffusion of drugs between the membrane and the microneedles. The second device is gold coated and it works as electrode for the electrochemical detection of species in the interstitial fluid. A preliminary result in detection of glucose will be shown.

Multianalyte Biosensor Patch Based on Polymeric Microneedles

Multianalyte biosensor patch based on polymeric microneedles (MNs) have been fabricated by photolithography of poly (ethylene glycol) diacrylate (PEGDA) and have been dynamically characterized by means of quartz crystal microbalance and electrochemical measurements. The resulting flexible device acts as multianalyte working electrodes detecting glucose and lactic acid into interstitial liquid by means of redox reaction with glucose oxidase (GOx) and lactose oxidase (LOx) enzymes. Sensitivities of the order of nA mM−1 in the mM range are revealed in both case, after five minutes of swelling time and ten second of interaction.

Hybrid organic-inorganic semiconductor transducer for optical and electrical sensing

Porous silicon (PSi) non-symmetric multilayers are modified by organic molecular beam deposition of an organic semiconductor, namely the N,N’-1H,1H-perfluorobutyldicyanoperylene-carboxydi-imide (PDIF-CN2). Joule evaporation of PDIF-CN2 into the PSi sponge-like matrix not only improves but also adds transducing skills, making this solid-state device a dual (optical and electrical) signal sensor for biochemical monitoring. PDIF-CN2 modified PSi optical microcavities show an increase of about 5 orders of magnitude in electric current with respect to the same bare device. This feature can be used to sense volatile substances.

New perspectives in silicon micro and nanophotonics

In the last two decades, there has been growing interest in silicon-based photonic devices for many optical applications: telecommunications, interconnects and biosensors. In this work, an advance overview of our results in this field is presented. Proposed devices allow overcoming silicon intrinsic drawbacks limiting its application as a photonic substrate. Taking advantages of both non-linear and linear effects, size reduction at nanometric scale and new two-dimensional emerging materials, we have obtained a progressive increase in device performance along the last years. In this work we show that a suitable design of a thin photonic crystal slab realized in silicon nitride can exhibit a very strong field enhancement. This result is very promising for all photonic silicon devices based on nonlinear phenomena. Moreover we report on the fabrication and characterization of silicon photodetectors working at near-infrared wavelengths based on the internal photoemission absorption in a Schottky junction. We show as an increase in device performance can be obtained by coupling light into both micro-resonant cavity and waveguiding structures. In addition, replacing metal with graphene in a Schottky junction, a further improve in PD performance can be achieved. Finally, silicon-based microarray for biomedical applications, are reported. Microarray of porous silicon Bragg reflectors on a crystalline silicon substrate have been realized using a technological process based on standard photolithography and electrochemical anodization of the silicon. Our insights show that silicon is a promising platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.

Hybrid interfaces for a new class of optical biosensors

Interfaces play a key role in optical biosensor fabrication: biological molecules need to be integrated with inorganic transducers, both electrical and optical, preserving their functions and specificity. Single DNA stands, proteins, enzymes, and antibodies must be blocked on surface by absorption or covalently, depending on different chemistry used. In case of proteins and antibodies, also orientation of biological molecules is very important. In this work, we present our results on a biological passivation procedure that employs hydophobins, small amphiphilic proteins. Since these proteins complex with sugars in nature, we also suggest their utilization as functional layer in optical biosensor for glucose.