Silicon-nanowire based attachment of silicon chips for mouse embryo labelling

The adhesion of small silicon chips to cells has many potential applications as direct interconnection of the cells to the external world can be accomplished. Hence, although some typical applications of silicon nanowires integrated into microsystems are focused on achieving a cell-on-a-chip strategy, we are interested in obtaining chip-on-a-cell systems. This paper reports the design, technological development and characterization of polysilicon barcodes featuring silicon nanowires as nanoscale attachment to identify and track living mouse embryos during their in vitro development. The chips are attached to the outer surface of the Zona Pellucida, the cover that surrounds oocytes and embryos, to avoid the direct contact between the chip and the embryo cell membrane. Two attachment methodologies, rolling and pushpin, which allow two entirely different levels of applied forces to attach the chips to living embryos, are evaluated. The former consists of rolling the mouse embryos over one barcode with the silicon nanowires facing upwards, while in the latter, the barcode is pushed against the embryo with a micropipette. The effect on in vitro embryo development and the retention rate related to the calculated applied forces are stated. Field emission scanning electron microscopy inspection, which allowed high-resolution imaging, also confirms the physical attachment of the nanowires with some of them piercing or wrapped by the Zona Pellucida and revealed extraordinary bent silicon nanowires.

142 ZONA PELLUCIDA TAGGING WITH BARCODES ALLOWS THE TRACEABILITY OF BOVINE EMBRYOS CULTURED IN GROUP

The low number of oocytes collected from unstimulated donors by ovum pick-up means that embryos produced from each female have to be cultured in very small groups. Because embryo quality and development rates are reduced in individual and small group culture, several methods to culture embryos individually but sharing the same medium have been designed. However, these systems prevent embryo movements, interfering with paracrine factors transmission and gradient changes. Here, we present an alternative in vitro culture method to allow the co-culture of embryos from different origins, without movement restriction and preserving their pedigree, by labelling the zygotes with polysilicon barcodes attached to the outer surface of the zona pellucida (ZP). Barcodes (10 × 6 × 1 µm) with 8 rectangular bits of binary codification (256 possible combinations), which can be read under a standard inverted microscope, were fabricated using silicon microtechnologies. To provide the barcodes with a ZP-binding capacity, they were biofunctionalized by self-assembled monolayers with the wheat germ agglutinin (WGA) lectin, which recognizes specific saccharides highly abundant in the ZP of most mammalian species. As a proof of concept, the culture method was tested on bovine zygotes produced from slaughterhouse-derived cow oocytes matured and fertilized in vitro. Using a mouth-controlled pipette, presumptive zygotes were individually rolled over WGA-biofunctionalized barcodes (8 barcodes/embryo) previously placed at the bottom of a drop of manipulation media. Four different barcodes, each one with a different codification, were used to encode 25 embryos (6–7 embryos/barcode codification), which were then cultured together in the same drop of medium. Day 7 (D7) and Day 8 (D8) blastocyst, and barcode retention rates were assessed. In addition, D7 expanded blastocysts were vitrified by the cryotop method and post-warming survival was determined as re-expansion rate at 24 h in culture. Finally, the quality of D8 blastocysts was assessed by differential staining and counting of inner cell mass (ICM) and trophectoderm (TE) cells. In all the experiments, a control group without barcodes was cultured and vitrified-warmed. Data were analyzed by chi-square and Mann–Whitney tests. The presence of barcodes attached to the ZP did not affect in vitro embryo development (D8 blastocysts: 29.7% control n = 309, 36.2% encoded n = 315), post-warming survival (86.4% control n = 66, 80.5% encoded n = 82), or blastocyst quality (IMC/TE: 22.1 ± 1.4/64.5 ± 5.7 control n = 18, 22.2 ± 1.7/64.1 ± 6.1 encoded n = 23). The labelling system was effective until D8 of culture, as all the embryos maintained barcodes attached (4 ± 1.8 barcodes/embryo) and could be identified, even after undergoing vitrification and warming. In conclusion, identification of co-cultured embryos by biofunctionalized barcodes attached to the ZP is feasible and will allow to culture embryos from different donors in the same drop, keeping the benefits of collective culture. Support was provided by Spanish MEC (TEC2011-29140-C03; RZ2010-00015-0-00; AGL2010-19069), Generalitat Catalunya (2009 SGR 282 and 621), and PIF-UAB Fellowship.

Strong coupling between mechanical modes in a nanotube resonator

We report on the nonlinear coupling between the mechanical modes of a nanotube resonator. The coupling is revealed in a pump-probe experiment where a mode driven by a pump force is shown to modify the motion of a second mode measured with a probe force. In a second series of experiments, we actuate the resonator with only one oscillating force. Mechanical resonances feature exotic line shapes with reproducible dips, peaks, and jumps when the measured mode is commensurate with another mode with a frequency ratio of either 2 or 3. Conventional line shapes are recovered by detuning the frequency ratio using the voltage on a nearby gate electrode. The exotic line shapes are attributed to strong coupling between the mechanical modes. The possibility to control the strength of the coupling with the gate voltage holds promise for various experiments, such as quantum manipulation, mechanical signal processing, and the study of the quantum-to-classical transition.

Nanomagnets with high shape anisotropy and strong crystalline anisotropy: perspectives on magnetic force microscopy

We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials.

Chemical functionalization of polysilicon microparticles for single-cell studies

In this work, two types of polycrystalline silicon (polysilicon) microparticles were modified with specific ligands in order to be selectively attached to chemical residues located at the plasma membrane and thus to be applied to study individual cells in culture. Two different functionalization approaches based on adsorption and covalent attachment were assayed. A comparative study of the efficiency of the ligand immobilization and stability of the modified particle in the culture medium was carried out using the selected ligands labeled with a fluorophore. Cylindrical microparticles (nonencoded microparticles) and shape-encoded microparticles (bar codes) were used with the aim of demonstrating the nondependence of the particle size and shape on the efficiency of the immobilization protocol. Fluorescence imaging and statistical analysis of the recorded fluorescence intensity showed that the covalent attachment of the ligand to the surface of the microparticle, previously modified with an aldehyde-terminated silane, gave the best results. As a proof of concept, Vero cells in culture were labeled with the covalently modified bar codes and successfully tracked for up to 1 week without observing any alteration in the viability of the cells. Bar code numbers could be easily read by eye using a bright-field optical microscope. It is anticipated that such modified microparticles could be feasible platforms for the introduction of other analytical functions of interest in single-cell monitoring and cell sorting in automatic analysis systems.

3-D modulable PDMS-based microlens system

The design, simulation, fabrication and characterization of 3-D modulable micro-optical system based on poly-dimethilsiloxane (PDMS) are presented in this paper. This system consists on two uncoupled PDMS lenses with different diameter (2 and 10 microm). Under stretching conditions, the dimensions of the small lens are not modified, whereas the geometry of the bigger lens is shifted from spherical to elliptical. A combination of different technologies is used to fabricate this microsystem: silicon, polymer and soft-lithography microfabrication techniques. This combination allows obtaining structures with a simple and mass production technology. Experimental results confirm the predicted numerical simulations, showing that, when the structure is under stretching conditions, the first focus is virtually invariable whereas the second focus becomes a Sturm zone.

Bullous solar elastosis

Solar elastosis (SE) is a well-recognized manifestation of chronic sun exposure, mainly affecting white patients. Well-established clinical manifestations of SE include Favre-Racouchot syndrome, cutis rhomboidalis nuchae, actinic comedonal plaques, elastomas, elastotic nodules of the ears, elastotic bands, collagenous plaques of the hands and colloid millia. Bullous SE is a very unusual presentation of SE, which consists clinically of tense bullae on chronically sun-damaged skin and is characterized histopathologically by a dermal cleft within a dermis with severe SE. Bullous SE is a rare but characteristic clinical expression of SE.

Light coupling into an optical microcantilever by an embedded diffraction grating

By measuring the excitation efficiency of an optical waveguide on a diffraction grating one can accurately register the changes in the incidence angle of the exciting light beam. This phenomenon was applied to detect ultrasmall deflections of silicon dioxide cantilevers of submicrometer thickness that were fabricated with corrugation on top to act as diffraction grating couplers. The power of light coupled into the cantilevers was monitored with a conventional photodetector and modulated using mechanical vibration of the cantilever, thus changing the spatial orientation of the coupler with respect to the incident light beam. The technique can be considered as an alternative to the methods known for detection of cantilever deflection.

Cytologic, cytochemical, immunocytochemical and ultrastructural diagnosis of a sacrococcygeal chordoma in a fine needle aspiration biopsy specimen

The cytologic, cytochemical, immunocytochemical and ultrastructural findings on the aspirated material are presented for the case of a 57-year-old man with sacrococcygeal chordoma diagnosed by fine needle aspiration biopsy. Cytologically, two types of cellular elements were differentiated: medium-sized cells with few cytoplasmic vacuoles and classic physaliferous cells. Both types showed marked cytoplasmic positivity for keratin and S-100 protein; the absence of nuclear positivity in the physaliferous cells was notable. Ultrastructural study demonstrated the existence of true intracytoplasmic vacuoles and frequent rough endoplasmic reticulum-mitochondria complexes. The cytologic differential diagnosis with chondrosarcoma, myxoid liposarcoma, ependymoma and metastases of mucosecretory carcinomas is reviewed.