A novel allergy biosensor is designed and fabricated by using thin film bulk acoustic resonator (TFBAR) devices with shear mode ZnO piezoelectric thin films. To fabricate TFBAR devices, the off-axis RF magnetron sputtering method for the growth of piezoelectric ZnO piezoelectric thin films is adopted. The influences of the relative distance and sputtering parameters are investigated. In this report, the piezoelectric ZnO thin films with tilting angle are set by controlling the deposition parameters. The properties of the shear mode ZnO thin films are investigated by X-ray diffraction and scanning electron microscopy. The frequency response is measured using an HP8720 network analyzer with a CASCADE probe station. The resonance frequency of the shear mode is 796.75 MHz. The sensitivity of the shear mode is calculated to be 462.5 kHz·cm2/ng.

The sensor team at the Los Alamos National Laboratory is an integrated multidisciplinary group that develops both core technologies as well as accessory tools for efficient biodetection. We have developed a waveguide-based optical biosensor for the efficient and ultra-sensitive, rapid detection of biological agents. We have previously demonstrated the use of this technology for the detection of biomarkers associated with many diseases. Herein, we present the preliminary data demonstrating the extension of this technology to the discovery and detection of Traumatic Brain Injury (TBI). TBI afflicts a significant percentage of US troops deployed in Iraq and Afghanistan, but is difficult to diagnose efficiently. Currently, only neuropsychological questionnaires are being used for the diagnosis of this condition, which can range from mild concussion to severe brain damage. The ultimate goal of this project is to develop a rapid biomarker-based diagnostic for TBI in blood. However, this cannot be accomplished until a comprehensive repertoire of biomarkers secreted during brain injury is established. This requires an integrated biomarker discovery and detection approach that is sampled directly from human serum and cerebrospinal fluid.

The results reported here are preliminary steps in that direction wherein we aim to develop two different methods for the discovery of novel biomarkers of TBI in blood and cerebrospinal fluid, as well as develop assays for two biomarkers on an ultra-sensitive waveguide-based platform that was developed at LANL. We were able to evaluate two different methods for biomarker discovery: Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and two dimensional gel electrophoresis (2-DE) in serum samples. In addition to development of depletion protocols to remove abundant proteins in serum, we were also able to detect spiked TBI biomarkers using both methods. However, the results clearly show that for protein biomarkers, MALDI MS is much more sensitive than 2-DE. We also developed a sandwich immunoassay on a waveguide-based platform for a TBI biomarker, procalcitonin, using commercially available antibodies. We show with our methods that we were able to directly detect procalcitonin from human serum. While our discovery and detection methods show promising results, these methods need to be further optimized before we can apply it to clinically relevant samples.

Two typed bio-conjugated soft-interface for highly sensitive immunoassay was developed by integrating a phospholipid polymer. Nano-sphered surface with poly [2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)-co-p-nitrophenyloxycarbonyl poly(ethylene glycol) methacrylate (MEONP)]: PMBN) was prepared by electrospray deposition (ESD) method. The three dimensional nano-sphered surface can be captured an antibody with high density around 860 ng/cm2. The theoretical amount of closest packed immobilized antibodies on flat surface is around 650 ng/cm2, thus large amount of antibodies were immobilized on the nano-sphere surface. The water stability of PMBN nanostructure was improved by crosslinking with 1,4-butylenediamine and by heating. Both heated and cross-linked PMBN nanostructure was not changed at all remaining high porosity after immersing in water. The specific signal in the immunoassay was enhanced with both heated and cross-linked PMBN nanostructure. The PMBN nanostructure which has high porosity and high water stability realized highly sensitive immunoassay.

As the other platform, we developed a novel soft-interface consisting of a well-defined phospholipid polymer surface on which Staphylococcal Protein A (SpA) was site-selectively immobilized. The phospholipid polymer platform was prepared on silicon substrates using the surface-initiated atom transfer radical polymerization (SI-ATRP) technique. Orientation-controlled antibodies were achieved using enzymatic reactions, and these antibodies captured 1.8 ± 0.1 antigens on average, implying that at least 80% of immobilized antibodies reacted with 2 antigens. Theoretical multivalent binding analysis further revealed that orientation-controlled antibodies had antigen-antibody reaction equilibrium dissociation constants (Kd) as low as 8.6 × 10-10 mol/L, whereas randomly oriented and partially oriented antibodies showed Kd values of 2.0 × 10-7 mol/L and 1.2 × 10-7 mol/L, respectively. These findings support the significance of antibody orientation because controlling the orientation resulted in high reactivity and theoretical binding capacity.