Hollow silicon microneedle fabrication using advanced plasma etch technologies for applications in transdermal drug delivery

A novel production process flow is presented here for the manufacture of hollow silicon microneedles using deep reactive-ion etching (DRIE) technology. The patent-pending three-step process flow has been developed to produce multiple arrays of sharp-tipped, hollow microneedles, which facilitate easy insertion and controlled fluid injection into excised skin samples. A bevelled tip and vertical sidewalls for the microneedle have been achieved with good uniformity, despite >45% open etch area. Processing steps and etch challenges are discussed, and preliminary skin testing results are presented, showing effective needle insertion and delivery of fluorescent dye into ex vivo skin from human breast tissue

Accuracy of the short-form Montreal Cognitive Assessment: systematic review and validation

Introduction: Short‐form versions of the Montreal Cognitive Assessment (SF‐MoCA) are increasingly used to screen for dementia in research and practice. We sought to collate evidence on the accuracy of SF‐MoCAs and to externally validate these assessment tools. Methods: We performed systematic literature searching across multidisciplinary electronic literature databases, collating information on the content and accuracy of all published SF‐MoCAs. We then validated all the SF‐MoCAs against clinical diagnosis using independent stroke (n = 787) and memory clinic (n = 410) data sets. Results: We identified 13 different SF‐MoCAs (21 studies, n = 6477 participants) with differing test content and properties. There was a pattern of high sensitivity across the range of SF‐MoCA tests. In the published literature, for detection of post stroke cognitive impairment, median sensitivity across included studies: 0.88 (range: 0.70‐1.00); specificity: 0.70 (0.39‐0.92). In our independent validation using stroke data, median sensitivity: 0.99 (0.80‐1.00); specificity: 0.40 (0.14‐0.87). To detect dementia in older adults, median sensitivity: 0.88 (0.62‐0.98); median specificity: 0.87 (0.07‐0.98) in the literature and median sensitivity: 0.96 (range: 0.72‐1.00); median specificity: 0.36 (0.14‐0.86) in our validation. Horton's SF‐MoCA (delayed recall, serial subtraction, and orientation) had the most favorable properties in stroke (sensitivity: 0.90, specificity: 0.87, positive predictive value [PPV]: 0.55, and negative predictive value [NPV]: 0.93), whereas Cecato's “MoCA reduced” (clock draw, animal naming, delayed recall, and orientation) performed better in the memory clinic (sensitivity: 0.72, specificity: 0.86, PPV: 0.55, and NPV: 0.93). Conclusions: There are many published SF‐MoCAs. Clinicians and researchers using a SF‐MoCA should be explicit about the content. For all SF‐MoCA, sensitivity is high and similar to the full scale suggesting potential utility as an initial cognitive screening tool. However, choice of SF‐MoCA should be informed by the clinical population to be studied

Design, fabrication, and characterisation of a silicon microneedle array for transdermal therapeutic delivery using a single step wet etch process

The fabrication of silicon in-plane microneedle arrays from a simple single wet etch step is presented. The characteristic 54.7° sidewall etch angle obtained via KOH etching of (1 0 0) orientation silicon wafers has been used to create a novel microneedle design. The KOH simultaneously etches both the front and back sides of the wafer to produce V shaped grooves, that intersect to form a sharp pyramidal six-sided microneedle tip. This method allows fabrication of solid microneedles with different geometries to determine the optimal microneedle length and width for effective penetration and minimally invasive drug delivery. A modified grooved microneedle design can also be used to create a hollow microneedle, via bonding of two grooved microneedles together, creating an enclosed hollow channel. The microneedle arrays developed, effectively penetrate the skin without significant indentation, thereby enabling effective delivery of active ingredients via either a poke and patch application using solid microneedles or direct injection using hollow microneedles. This simple, scalable and cost effective method utilises KOH to etch the silicon wafer in-plane, allowing microneedles with variable length of several mm to be fabricated, as opposed to out-of-plane MNs, which are geometrically restricted to dimensions less than the thickness of the wafer. These microneedle arrays have been used to demonstrate effective delivery of insulin and hyaluronic acid into the skin

Hollow silicon microneedle fabrication using advanced plasma etch technologies for applications in transdermal drug delivery

A novel production process flow is presented here for the manufacture of hollow silicon microneedles using deep reactive-ion etching (DRIE) technology. The patent-pending three-step process flow has been developed to produce multiple arrays of sharp-tipped, hollow microneedles, which facilitate easy insertion and controlled fluid injection into excised skin samples. A bevelled tip and vertical sidewalls for the microneedle have been achieved with good uniformity, despite >45% open etch area. Processing steps and etch challenges are discussed, and preliminary skin testing results are presented, showing effective needle insertion and delivery of fluorescent dye into ex vivo skin from human breast tissue