Integrated ultrasonic particle positioning and low excitation light fluorescence imaging

A compact hybrid system has been developed to position and detect fluorescent micro-particles by combining a Single Photon Avalanche Diode (SPAD) imager with an acoustic manipulator. The detector comprises a SPAD array, light-emitting diode (LED), lenses, and optical filters. The acoustic device is formed of multiple transducers surrounding an octagonal cavity. By stimulating pairs of transducers simultaneously, an acoustic landscape is created causing fluorescent micro-particles to agglomerate into lines. The fluorescent pattern is excited by a low power LED and detected by the SPAD imager. Our technique combines particle manipulation and visualization in a compact, low power, portable setup

Dynamic acoustic field activated cell separation (DAFACS)

Advances in diagnostics, cell and stem cell technologies drive the development of application-specific tools for cell and particle separation. Acoustic micro-particle separation offers a promising avenue for highthroughput, label-free, high recovery, cell and particle separation and isolation in regenerative medicine. Here, we demonstrate a novel approach utilizing a dynamic acoustic field that is capable of separating an arbitrary size range of cells. We first demonstrate the method for the separation of particles with different diameters between 6 and 45 μm and secondly particles of different densities in a heterogeneous medium. The dynamic acoustic field is then used to separate dorsal root ganglion cells. The shearless, label-free and low damage characteristics make this method of manipulation particularly suited for biological applications. Advantages of using a dynamic acoustic field for the separation of cells include its inherent safety and biocompatibility, the possibility to operate over large distances (centimetres), high purity (ratio of particle population, up to 100%), and high efficiency (ratio of separated particles over total number of particles to separate, up to 100%)

Synthetic studies on terpenoids. Part 19. Synthesis of 3β,10α,14β-trimethyl-1βH,11βH-tricyclo[9.3.0.0]tetradec-6-en-5-one, a tricyclic ketone related to the ophiobolins

The tricarbocyclic ketone (36) with well defined stereochemistry at each of the four contiguous asymmetric centres has been synthesised, and the stereochemistry of these centres has been deduced mechanistically and confirmed by X-ray crystallographic analysis of the bicyclic acidic precursor (22). The orientation of the tertiary methyl group in structure (36) has been deduced from force-field calculations and confirmed by model studies. The configuration of the two ring junction hydrogen atoms and of the two methyl groups in structure (36) are the same as found in the ophiobolins. The conformations of substituted cis-perhydroindanones, bicyclo[3.3.1 ]nonanes, cyclo-octenes and cyclo-octanones, are described

Future integration of silicon electronics with miniature piezoelectric ultrasonic transducers and arrays

The long-established pace of progress in semiconductor electronics, expressed by Moore's Law, has led to new opportunities in medical ultrasound imaging. Traditionally, ultrasound systems have separated the transducer array from most of the electronic instrumentation, with multicore physical cabling in between. This avoids problems with electrical power, functional density, and communication bandwidth. However, it is far from ideal in terms of cost, ergonomics, and the need to interface instrumentation and the transducer with the cable, and it causes particular difficulties with miniature devices. Given these issues, and the relatively slow progress in front end transducer technology, integration of the transducer with electronics is certain to increase, most likely at a pace governed by financial investment, development of electronics for other applications, and the realisation of high volume ultrasound applications. This paper therefore considers motivations for increased integration, technical barriers, and relevant new techniques, particularly related to microelectromechanical systems (MEMS). Increased integration will rely on advances in integrated circuit (IC) electronics, device assembly, and microsystems engineering, with key constraints being the packaging of a system in a small volume and the power supply. System partitioning will determine where functionality will reside physically within the imaging hardware and software. This paper considers relevant recent developments in academic research and industry, with a particular focus on medical applications. IC design is important because it defines parameters such as power consumption. 45 nm ICs are now in high volume production but the present relatively small ultrasound market makes adoption difficult. Ingenuity in exploiting existing technology cost-effectively and bespoke engineering where required are likely to be important for integration of piezoelectric material with electronics technology and funct- - ionality will correspond with different layers in a device. In this paper, examples are selected from the authors' work to illustrate progress and suggest how MEMS roadmaps and application demands may relate to future systems

Acoustic Tweezing for Patterning and Discriminating Particles

We present a novel sensor device that acoustically patterns and discriminates micron-scale particles. Such techniques, that allow the micro-manipulation and isolate cells, particles or droplets by non-invasive means, are desired to facilitate biophysical or biological applications such as microarrays and tissue engineering. Here, our approach utilizing a static acoustic field to pattern particles and a dynamic acoustic field that is capable of separating an arbitrary size range of particles. We first demonstrate the method for the separation of particles with different diameters between 6 and 45 μm. The shearless, label free and low damage characteristics make this method of manipulation particularly suited for biological applications. Advantages of using a dynamic acoustic field for the separation of particles include its tunability and adapt to the entities that need to be separated, inherent safety and biocompatibility, the possibility to operate over large distances (centimetres), high purity (ratio of particle population, up to 100%), and high efficiency (ratio of separated particles over total number of particles to separate, up to 100%)

Solution structure of P01, a natural scorpion peptide structurally analogous to scorpion toxins specific for apamin-sensitive potassium channel.

International audienceThe venom of the North African scorpion Androctonus mauretanicus mauretanicus possesses numerous highly active neurotoxins that specifically bind to various ion channels. One of these, P05, has been found to bind specifically to calcium-activated potassium channels and also to compete with apamin, a toxin extracted from bee venom. Besides the highly potent ones, several of these peptides (including that of P01) have been purified and been found to possess only a very weak, although significant, activity in competition with apamin. The amino acid sequence of P01 shows that it is shorter than P05 by two residues. This deletion occurs within an alpha-helix stretch (residues 5-12). This alpha-helix has been shown to be involved in the interaction of P05 with its receptor via two arginine residues. These two arginines are absent in the P01 sequence. Furthermore, a proline residue in position 7 of the P01 sequence may act as an alpha-helix breaker. We have determined the solution structure of P01 by conventional two-dimensional 1H nuclear magnetic resonance and show that 1) the proline residue does not disturb the alpha-helix running from residues 5 to 12; 2) the two arginines are topologically replaced by two acidic residues, which explains the drop in activity; 3) the residual binding activity may be due to the histidine residue in position 9; and 4) the overall secondary structure is conserved, i.e., an alpha-helix running from residues 5 to 12, two antiparallel stretches of beta-sheet (residues 15-20 and 23-27) connected by a type I' beta-turn, and three disulfide bridges connecting the alpha-helix to the beta-sheet

Acoustophoresis of monodisperse oil droplets in water:Effect of symmetry breaking and non-resonance operation on oil trapping behavior

Acoustic manipulation of particles in microchannels has recently gained much attention. Ultrasonic standing wave (USW) separation of oil droplets or particles is an established technology for microscale applications. Acoustofluidic devices are normally operated at optimized conditions, namely, resonant frequency, to minimize power consumption. It has been recently shown that symmetry breaking is needed to obtain efficient conditions for acoustic particle trapping. In this work, we study the acoustophoretic behavior of monodisperse oil droplets (silicone oil and hexadecane) in water in the microfluidic chip operating at a non-resonant frequency and an off-center placement of the transducer. Finite element-based computer simulations are further performed to investigate the influence of these conditions on the acoustic pressure distribution and oil trapping behavior. Via investigating the Gor’kov potential, we obtained an overlap between the trapping patterns obtained in experiments and simulations. We demonstrate that an off-center placement of the transducer and driving the transducer at a non-resonant frequency can still lead to predictable behavior of particles in acoustofluidics. This is relevant to applications in which the theoretical resonant frequency cannot be achieved, e.g., manipulation of biological matter within living tissues

X-ray and carbon-13 nuclear magnetic resonance characterization of cyclopropane derivatives obtained by solvolysis of (E)-3α- and (E)-3β-hydroxy-5,10-seco-1(10)-cholesten-5-one tosylates

The stereochemistries and conformations of the cyclopropane ring containing compounds derived from (E-3α- and (E)-3β-hydroxy-5,10-seco-1(10)-cholesten-5-one tosylates have been determined by X-ray methods and the results correlated with 13C nmr chemical shift data. © 1979