Simone Tanzi

Manipulation of self-assembly amyloid peptide nanotubes by dielectrophoresis

Self‐assembled amyloid peptide nanotubes (SAPNT) were manipulated and immobilized using dielectrophoresis. Micro‐patterned electrodes of Au were fabricated by photolithography and lifted off on a silicon dioxide layer. SAPNT were manipulated by adjusting the amplitude and frequency of the applied voltage. The immobilized SAPNT were evaluated by SEM and atomic force microscopy. The conductivity of the immobilized SAPNT was studied by I–V characterization, for both single SAPNT and bundles. This work illustrates a way to manipulate and integrate biological nanostructures into novel bio‐nanoassemblies with concrete applications, such as field‐effect transistors, microprobes, microarrays, and biosensing devices.

Fabrication of combined-scale nano- and microfluidic polymer systems using a multilevel dry etching, electroplating and molding process

Microfabricated single-cell capture and DNA stretching devices have been produced by injection molding. The fabrication scheme employed deep reactive ion etching in a silicon substrate, electroplating in nickel and molding in cyclic olefin polymer. This work proposes technical solutions to fabrication challenges associated with chip sealing and demolding of polymer high-volume replication methods. UV-assisted thermal bonding was found to ensure a strong seal of the microstructures in the molded part without altering the geometry of the channels. In the DNA stretching device, a low aspect ratio nanoslit (1/200) connecting two larger micro-channels was used to stretch a 168.5 kbp DNA molecule, while in the other device single-HeLa cells were captured against a micro-aperture connecting two larger microfluidic channels. Different dry etching processes have been investigated for the master origination of the cell-capture device. The combination of a modified Bosch process and an isotropic polysilicon etch was found to ensure the ease of demolding by resulting in slightly positively tapered sidewalls with negligible undercut at the mask interface. (Some figures may appear in colour only in the online journal)

Polymer multilevel lab-on-chip systems for electrochemical sensing

The authors present a scheme intended for production of large quantities of lab on chip systems by means of Si dry etching, electroplating, injection molding, and pressure-assisted thermal bonding. This scheme allows for the fabrication of large numbers of samples having a combination of structures with depths as small as tens of nanometers and as big as hundreds of microns on the same polymer chip. The authors also describe in detail the fabrication procedure of polymer substrates with embedded Au and pedot:tosylate electrodes for electrochemical applications. The electrode fabrication process is simple and fit for integration in a production scheme. The electrode–substrates are then bonded to injection molded counterparts to be used for electrochemical applications. A dimensional and functional characterization of the electrodes is also presented here.

Meucin-49, a multifunctional scorpion venom peptide with bactericidal synergy with neurotoxins

Besides key roles in prey capture and predator defense, scorpion venom also functions as internal immune agents protecting the venom gland from infection and external immune agents cleaning saprophytic microbes from their own body surfaces. However, antimicrobials (typically antimicrobial peptides, AMPs) in the venom often exist in low abundance that might exclude their immune role alone, leaving an open question with regard to their in vivo biological function. Here, we report the bactericidal activity of seven peptides isolated from the scorpion Mesobuthus eupeus venom, including one classical α-helical AMP and five ion channel-targeted neurotoxins. This AMP of 49 amino acids (named Meucin-49) is a multifunctional molecule that displays a wide-spectrum and highly potent activity against Gram-positive and Gram-negative bacteria with strong hemotoxicity on scorpion’s predators (i.e., mammals, lizards, and birds) and high insecticidal activity. Although the neurotoxins targeting voltage-gated sodium (Nav) and/or large conductance calcium-activated potassium (BK) channels showed only marginal activity towards several species of bacteria, they were capable of significantly potentiating the bactericidal potency of Meucin-49. This observation highlights, for the first time, the venom’s antibacterial immune function mediated by a joint action between neurotoxins and AMPs. The findings that traditionally defined neurotoxins possess (synergistic) bactericidal activity, while the classical AMPs play predatory and defensive roles, provide new evidence in favor of a general and intrinsic multifunctionality of scorpion venom components.

Nano Imprint Lithography, a green technology

In the 3-week term June 2010 we have worked with Nano Imprint Lithography (NIL) in the course 33422. NIL is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and at low costs. NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. In this presentation we will present NIL as an energy efficient and environmental friendly technology compared to traditional micro and nano fabrication approaches. We will introduce NIL and describe why it can be considered a green technology.