@article{KupstatKumkeHildebrandt2011,
  author    = {Kupstat, Annette and Kumke, Michael Uwe and Hildebrandt, Niko},
  title     = {Toward sensitive, quantitative point-of-care testing (POCT) of protein markers miniaturization of a homogeneous time-resolved fluoroimmunoassay for prostate-specific antigen detection},
  series = {The analyst : the analytical journal of the Royal Society of Chemistry},
  volume    = {136},
  journal   = {The analyst : the analytical journal of the Royal Society of Chemistry},
  number    = {5},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {0003-2654},
  doi       = {10.1039/c0an00684j},
  pages     = {1029 -- 1035},
  year      = {2011},
  abstract  = {Point-of-care testing (POCT) systems which allow for a sensitive, quantitative detection of protein markers are extremely useful for the early detection and therapy progress monitoring of cancer. However, currently commercially available POCT devices are mainly limited to the qualitative detection of protein markers. In this study we demonstrate the successive miniaturization of a sensitive and fast assay for the quantitative detection of prostate-specific antigen (PSA) using a well established and clinically approved homogeneous time-resolved fluoroimmunoassay technology (TRACE (R)) on a commercial plate-reader system (KRYPTOR (R)). Regarding the initial requirements for the development of POCT devices we applied a 30-fold assay volume reduction (150 mu L to 5 mu L) to achieve a reasonable lab-on-a-chip volume and a 24-fold and 120-fold excitation pulse energy reduction to achieve reasonable pulse energies for low-cost miniature excitation sources. Due to highly efficient optimization of key POCT parameters our miniaturized PSA assay achieved a 30\% increased sensitivity and a 2-fold improved limit of detection compared to the standard plate-reader method. Our results demonstrate the successful implementation of key parameters for a significant miniaturization and for cost reduction in the clinically approved KRYPTOR (R) platform for protein detection. The technological alterations required are easy-to-implement and can be immediately adapted for more than 30 diagnostic protein markers already available for the KRYPTOR (R) platform. These features strongly recommend our assay format to be utilized in innovative, sensitive, quantitative POCT of protein markers.},
  language  = {en}
}
@article{CywinskiMoroRitscheletal.2011,
  author    = {Cywinski, Piotr J. and Moro, Artur J. and Ritschel, Thomas and Hildebrandt, Niko and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Sensitive and selective fluorescence detection of guanosine nucleotides by nanoparticles conjugated with a naphthyridine receptor},
  series = {Analytical \& bioanalytical chemistry},
  volume    = {399},
  journal   = {Analytical \& bioanalytical chemistry},
  number    = {3},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1618-2642},
  doi       = {10.1007/s00216-010-4420-2},
  pages     = {1215 -- 1222},
  year      = {2011},
  abstract  = {Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides, and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene nanoparticles functionalized by (N-(7-((3-aminophenyl) ethynyl)-1,8-naphthyridin- 2-yl) acetamide) via carbodiimide ester activation. We show that this naphthyridine nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern-Volmer constants in the range of 2.1 to 35.9mM(-1). For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined. The lowest (3 sigma) LOD was found for guanosine 3',5'-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition, we demonstrated that the spatial arrangement of bound analytes on the nanosensors' surfaces is what is responsible for their selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and the number of phosphate groups of a nucleotide. Results of molecular modeling and zeta-potential measurements confirm that the arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems.},
  language  = {en}
}