Optical imaging using unspecific contrast agents as well as targeted and disease-specific agents play a vital role in preclinical research. Moreover, optical imaging is on the verge of establishing itself as a clinically relevant imaging modality. Also in-vitro diagnostical procedures rely to a large degree on optical labels to report disease-specific events. Materials that fulfill the basic requirements of this market are being used today, with cyanine dyes and semiconductor quantum dots being excellent examples. Other materials are being tested in laboratories throughout the world. Design rules suitable to develop new optical labels for in-vivo near-infrared optical imaging procedures have been formulated by us, and we have developed synthesis routes that lead to nano particles with small diameter, narrow size distribution, high quantum yield, and with stable surfaces required for bioconjugation to disease-specific ligands.
Novel optical labels based on nanophosphor materials like LaPO<sub>4</sub>:Ce,Tb and CePO<sub>4</sub>:Tb-LaPO<sub>4</sub> core-shell nanophosphors
were presented. Core particles could be synthesised smaller than 10nm and stabilized in aqueous media. Polymer
coatings of individual nanoparticles increased long term stability and introduced functional groups of interest for
bioconjugation chemistry. A new strategy for conjugation of bioligands via His-tags was given. In feasibility studies for
in-vitro diagnostic applications these dnanophosphors featured their advantage over organic dyes. As an example the
detection of hybridization and thermal induced denaturation events of DNA strands read out by FRET processes was