| Abstract
| - We present a new concept for ultrasensitive detection ofsurface-generated fluorescence which is made possibleby a new optical module. The detection method leads toan enhancement in fluorescence collection efficiency tomore than 65% of the total of emitted light, whereas high-aperture microscope objectives are able to collect 44% atbest. Moreover, by employing this new optical module,the detection volume can be restricted to ∼10-17 L. Thisallows for an exceptional discrimination of bulk-generatedagainst surface-generated fluorescence, which may be ofgreat value when surface-binding processes are monitored. We demonstrate the performance of the newdetection system by detecting single fluorescent moleculesand by determining antigen concentrations down to 5fmol.
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