Straight long-range surface plasmon waveguides are demonstrated as biosensors for the detection of cells, proteins and changes in the bulk refractive index of solutions. The sensors consist of 5 μm wide 22 nm thick Au stripes embedded in polymer (CYTOP™) with microfluidic channels etched into the top cladding. Bulk sensing is demonstrated by sequentially injecting six solutions of different refractive indices in 2 × 10(-3) RIU increments; such index steps were detected with a signal-to-noise ratio of ~1000. Selective capture of cells is demonstrated using Au waveguides functionalized with antibodies against blood group A, and red blood cells of group A and O in buffer as positive and negative analyte. Bovine serum albumin in buffer was used to demonstrate protein sensing. A monolayer of bovine serum albumin physisorbed on a carboxyl-terminated self-assembled monolayer on Au was detected with a signal-to-noise ratio of ~300. Overall, the biosensor demonstrated a good capability for detecting bulk changes in solution and for sensing analyte over a very wide range of mass (from cells to proteins). The biosensors are compact, inexpensive to fabricate, and may find use over a wide range of cost-sensitive sensing and detection applications.

We present a compact, cost-effective, label-free, real-time biosensor based on long-range surface plasmon polariton (LRSPP) gold (Au) waveguides for the detection of dengue-specific immunoglobulin M (IgM) antibody, and we demonstrate detection in actual patient blood plasma samples. Two surface functionalization approaches are proposed and demonstrated: a dengue virus serotype 2 (DENV-2) functionalized surface to capture dengue-specific IgM antibody in blood plasma and the reverse, a blood plasma functionalized surface to capture DENV-2. The results obtained via these two surface functionalization approaches are comparable to, or of greater quality, than those collected by conventional IgM antibody capture enzyme linked immunosorbent assay (MAC-ELISA). Our second functionalization approach was found to minimize nonspecific binding, thus improving the sensitivity and accuracy of the test. We also demonstrate reuse of the biosensors by regenerating the sensing surface down to the virus (or antibody) level or down to the bare Au.

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Articles you may be interested inEfficient end-fire coupling of surface plasmons on flat metal surfaces for improved plasmonic Mach-Zehnder interferometer J. Appl. Phys. 113, 053101 (2013); 10.1063/1.4789809 Refractive index sensor based on hybrid coupler with short-range surface plasmon polariton and dielectric waveguide Appl. Phys. Lett. 100, 111108 (2012); 10.1063/1.3693408Demonstration of long-range surface plasmon-polariton waveguide sensors with asymmetric double-electrode structures Appl.A high sensitivity refractometer based upon a long period grating Mach-Zehnder interferometer Rev.We demonstrate refractometric sensing using long-range surface plasmons on a compact integrated Mach-Zehnder interferometer (MZI) formed from thin Au stripes in Cytop with an etched microfluidic channel defining the sensing arm. The transfer characteristics of MZIs were obtained by sequentially injecting solutions of increasing refractive index in the sensing arm. A detection limit of 9 Â 10 À7 RIU was achieved at k 0 ¼ 1310 nm, limited by unbalanced losses in the sensing and reference arms. A model is proposed for the MZIs, taking into account all loss mechanisms, and may be applied to MZI sensors in other technologies. V C 2013 AIP Publishing LLC.