Biodetection Applications Research Articles

Gold Nanoparticles With Special Shapes: Controlled Synthesis, Surface-enhanced Raman Scattering, and The Application in Biodetection.

Specially shaped gold nanoparticles have intrigued considerable attention becausethey usually possess high-sensitivity surface-enhanced Raman scattering (SERS) and thusresult in large advantages in trace biodetermination. In this article, starch-capped goldnanoparticles with hexagon and boot shapes were prepared through using a nontoxic andbiologically benign aqueous-phase synthetic route. Shape effects of gold nanoparticles onSERS properties were mainly investigated, and found that different-shaped goldnanoparticles possess different SERS properties. Especially, the boot-shaped nanoparticlescould induce more 100-fold SERS enhancements in sensitivity as compared with those fromgold nanospheres. The extremely strong SERS properties of gold nanoboots have beensuccessfully applied to the detection of avidin. The unique nanoboots with high-sensitivitySERS properties are also expected to find use in many other fields such as biolabel,bioassay, biodiagnosis, and even clinical diagnosis and therapy.

Microinductive Signal Conditioning With Resonant Differential Filters: High-Sensitivity Biodetection Applications

Inductive-based devices integrated with Si technology for biodetection applications are characterized, using simple resonant differential filter configurations. This has allowed the corroboration of the viability of the proposed circuits, which are characterized by their very high simplicity, for microinductive signal conditioning in high-sensitivity sensor devices. The simulation of these simple circuits predicts sensitivities of the differential output voltage which can achieve values in the range of 0.1-1 V/nH, depending on the coil parameters. These very high-sensitivity values open the possibility for the experimental detection of extremely small inductance changes in the devices. For real microinductive devices, both series resistance and parasitic capacitive components contribute to the decrease of the differential circuit sensitivity. Nevertheless, measurements performed using micro-coils fabricated with relatively high series resistance and coupling parasitic effects have allowed detection of changes in the range of 2 nH. which are compatible with biodetection applications with estimated detection limits below the picomolarity range.

Protein detection via direct enzymatic amplification of short DNA aptamers

Aptamers are single-stranded nucleic acids that fold into defined tertiary structures to bind target molecules with high specificities and affinities. DNA aptamers have garnered much interest as recognition elements for biodetection and diagnostic applications due to their small size, ease of discovery and synthesis, and chemical and thermal stability. Here we describe the design and application of a short DNA molecule capable of both protein target binding and amplifiable bioreadout processes. Because both recognition and readout capabilities are incorporated into a single DNA molecule, tedious conjugation procedures required for protein–DNA hybrids can be omitted. The DNA aptamer is designed to be amplified directly by either polymerase chain reaction (PCR) or rolling circle amplification (RCA) processes, taking advantage of real-time amplification monitoring techniques for target detection. A combination of both RCA and PCR provides a wide protein target dynamic range (1 μM to 10 pM).

A Centrifugation-based Method for Preparation of Gold Nanoparticles and its Application in Biodetection

Gold nanoparticles (AuNPs) have found widespread applications in lifesciences. While synthesis of monodispersed AuNPs has been fairly convenient by usingchemical reduction of chloroauric acid by sodium citrate, we found that AuNPs of highquality and high concentrations were not readily obtained via this method. As an example,we showed that monodispersed 13-nm AuNPs were readily synthesized at relatively lowconcentrations (e.g. 3.5 nM); in contrast, 13-nm AuNPs of 17 nM obtained by the directreduction method were irregularly shaped and not well dispersed. In this work, wedemonstrated that AuNPs of high concentration could be prepared by a two-step approach,i.e. chemical reduction at low concentrations and subsequent centrifugation. Compared tothe direct reduction method, this new two-step method led to AuNPs with high saltresistance and high stability, which are essential for the preparation of DNA-AuNPsconjugates for DNA biodetection.

Nanostructured magnetizable materials that switch cells between life and death

Development of biochips containing living cells for biodetection, drug screening and tissue engineering applications is limited by a lack of reconfigurable material interfaces and actuators. Here we describe a new class of nanostructured magnetizable materials created with a femtosecond laser surface etching technique that function as multiplexed magnetic field gradient concentrators. When combined with magnetic microbeads coated with cell adhesion ligands, these materials form microarrays of ‘virtual’ adhesive islands that can support cell attachment, resist cell traction forces and maintain cell viability. A cell death (apoptosis) response can then be actuated on command by removing the applied magnetic field, thereby causing cell retraction, rounding and detachment. This simple technology may be used to create reconfigurable interfaces that allow users to selectively discard contaminated or exhausted cellular sensor elements, and to replace them with new living cellular components for continued operation in future biomedical microdevices and biodetectors.

Front Cover: Macromol. Rapid Commun. 10/2006

Front Cover: Water‐soluble cationic ammonium‐functionalized PPV possessing photoluminescence with high quantum efficiency interact with an anionic iron‐sulfur protein rubredoxin by attractive Coulomb interaction. Such polymer‐based biosensor exhibits high sensitivity and promising application in biodetection. Further details can be found in the article by F. Cheng, G.‐W. Zhang, X.‐M. Lu, Y.‐Q. Huang, Y. Chen, Y. Zhou, Q.‐L. Fan,* and W. Huang* on page 799.

Si technology based microinductive devices for biodetection applications

This work presents the design and fabrication of inductive devices integrated in Si technology aimed at high sensitivity biodetection applications. The sensing principle is based on the changes of the coil inductance due to the presence of magnetic particles in the active region of the device. These particles act as markers of the biological molecule to be detected. For the simulation of the devices, a very simple finite elements model has been developed. To increase the device sensibility to the presence of the magnetic particles, a magnetic layer has been locally deposited on the back of the substrate in the region of the coils. The analysis of these devices has shown their ability to detect a minimum amount of 110 magnetic particles fixed on an 0.8 mm 2 active area, which gives an estimation of the detection limit of the devices of about 4 × 10 −14 M. This corroborates the potential of the proposed microinductive devices for very high sensitivity detection of biological molecules.