Pampa Dutta

Studies of the Optical Properties of Metal-Pliable Polymer Composite Materials

Polymer-nano-metallic-particle composites have demonstrated technological potential due to their unique optical and electrical properties. Herein, we report on composites prepared via physical vapor deposition of silver metal onto pliable poly(dimethylsiloxane) (PDMS) polymer. Rapid Ag diffusion and nano-metallic-particle formation in a phase-separated surface layer of the PDMS creates unique sub-surface-based composites whose properties vary based on rate of deposition and average Ag thickness. Additionally, nano-metallic-particle spacing can be altered with fair reproducibility and reversibility by physically manipulating the Ag–PDMS composite. The optical properties of the materials are studied by visible wavelength optical extinction spectrometry and surface-enhanced Raman scattering (SERS), including studies performed during physical manipulation. Direct current (DC) conductivity measurements were made during Ag deposition to study percolation conditions for the materials. Depth-profiling was performed by X-ray photoelectron spectrometry. Sample Raman spectral data collected with the composite as a SERS substrate are included. A practical technological characteristic of these composite materials arises from their potential to be molded into functional devices.

Nanostructured cantilevers as nanomechanical immunosensors for cytokine detection

The use of microfabricated cantilevers as immunosensors for the detection of human interleukin-1 beta (HIL1-β), one of the proinflammatory cytokines, is demonstrated. Cytokines are important biomarkers to monitor the effect of drugs influencing the immune system or inflammation. Nanostructured microcantilevers (MCs) functionalized with anti-human interleukin-1 beta (anti HIL1-β) antibody (Ab) are used for achieving immunonanome-chanical responses. Antibody-antigen binding interaction induces an apparent surface stress, thereby causing static bending of the MC that is detected in this work by an optical beam bending technique. Specific binding of HIL1-β to surface-bound Ab produces substantial compressive surface stress, which enables its detection in presence of other interfering proteins. Combination of biospecificity of antibodies with the sensitivity of nanomechanical surface stress detection using MCs with one side nanostructured allows detection of cytokine HIL1-β in the ppb range. The nanostructured immuno-MCs, when compared to the smooth surface MC, exhibit higher responses and yet better reversibility. The detection of HIL1-β shows good measurement reproducibility (CV=10%) in the same day tested via three replicate consecutive measurements of a solution of 0.5 ppm of HIL1-β. Also, a reasonable stability of the Ab functionalized MC within 7 d of functionalization is observed. It can be envisioned that differentially functionalized MC arrays can be made in a similar fashion.