No abstract

Surface plasmon resonance (SPR) biosensors utilize refractive index changes to sensitively detect mass changes at noble metal sensor surface interfaces. As such, they have been extensively applied to immunoassays of large molecules, where their high mass and use of sandwich immunoassay formats can result in excellent sensitivity. Small molecule immunosensing using SPR is more challenging. It requires antibodies or high-mass or noble metal labels to provide the required signal for ultrasensitive assays. Also, it can suffer from steric hindrance between the small antigen and large antibodies. However, new studies are increasingly meeting these and other challenges to offer highly sensitive small molecule immunosensor technologies through careful consideration of sensor interface design and signal enhancement. This review examines the application of SPR transduction technologies to small molecule immunoassays directed to different classes of small molecule antigens, including the steroid hormones, toxins, drugs and explosives residues. Also considered are the matrix effects resulting from measurement in chemically complex samples, the construction of stable sensor surfaces and the development of multiplexed assays capable of detecting several compounds at once. Assay design approaches are discussed and related to the sensitivities obtained.

Nearly 17 years wave records from deep water and shore-based stations are used to describe the ocean wave characteristics around New Zealand. The wave environment is dominated by west and southwest swell and storm waves generated in the temperate latitude belt of westerly winds. As a result, the west and south coasts are exposed, high energy shores, the east coast is a high energy lee shore, and the northern coast from North Cape to East Cape is a low energy lee shore sheltered from these winds and waves. South of New Zealand, wave energies are extremely high; the prevailing deep water wave is 3.5-4.5 m high and has a 10-12 s period, with a slight increase in wave heights in winter. The west coast wave environment is mixed, and consists of locally generated westerly and southerly storm waves, and swell waves generated to the south. The prevailing wave is t.0-3.0 m and 6-8 s period. There are no strong seasonal rhythms, only shorter period cycles of wave height (5 day) associated with similar quasi-rhythmic cycles in the weather. The east coast also has a mixed wave climate with southerly swells, originating in the westerlies south of New Zealand, and locally generated southerly and northerly storm waves. The prevailing wave is 0.5-2.0 m and 7-11 s period. A short period rhythmic cycle, similar to that on the west coast, is superimposed on a weak seasonal cycle. The seasonal, cycle results from an increase in the frequency of local northerly waves in summer. The prevailing wave on the north coast is a northeasterly, 0.5-1.5 m high and 5-7 s period. Subtropical disturbances and southward-moving depressions generate a mixed wave environment and a possible seasonally reflecting a winter increase in. storminess.

A gold nanohole array is functionalized with a cortisol thiol derivative, and binding to a monoclonal antibody is conveniently detected using the sensitive shift in the 1060 nm transmission peak of the array. Detection is also enhanced 3-fold by the application of a secondary antibody-gold nanoparticle conjugate. This regenerable response represents a more sensitive shift than that obtained previously for higher affinity binding and opens the way to application of nanohole arrays in immunobiosensing of important biomolecules.