A glycomic approach is developed to identify oligosaccharide markers for ovarian cancer by rapidly profiling globally released oligosaccharides. Glycoproteins shed by cancer cells are found in the supernatant (or conditioned media) of cultured cells. In this approach, shed glycoproteins are profiled for their oligosaccharide content using beta-elimination conditions. Changes in glycosylation are monitored by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS). Because shed glycoproteins would also be found in serum, similar glycan profiling was performed to observe potential oligosaccharide markers. Oligosaccharide profiling data on a limited set of patient and normal serum samples were studied to determine potential glycan markers in ovarian cancer. We were able to demonstrate the presence of at least 15 unique serum glycan markers in all patients but absent in normal individuals. To determine the structure of the glycan biomarkers, a number of the ions were isolated and further analyzed using infrared multiphoton dissociation (IRMPD). One major advantage of this approach is that glycans are examined directly from patient sera without the need to obtain cancer biopsy specimens or to purify glycosylated proteins from these specimens.

The structural elucidation of oligosaccharides remains a major challenge. Mass spectrometry provides a rapid and convenient method for structural elucidation based on tandem mass spectrometry. Ions commonly are selected and subjected to collision-induced dissociation (CID) to obtain structural information. Unfortunately, N-linked oligosaccharides are relatively large compounds and are not readily fragmented using CID. In this report, we illustrate the use of infrared multiphoton dissociation (IRMPD) to obtain structural information for large N-linked oligosaccharides. The IRMPD and CID behavior of oligosaccharides were compared for high-mannose-type oligosaccharides. Fragmentation that could not be obtained through conventional CID in Fourier transform ion cyclotron resonance mass spectrometry was observed with N-linked oligosaccharides. O-Linked and N-linked glycans of similarly large sizes were compared. It was found that internal cross-ring cleavages were observed only for N-linked oligosaccharides. The mannose branch points of N-linked oligosaccharides are apparently more susceptible to cross-ring cleavages.

We have developed an efficient method for producing difunctional, bilateral nanospheres. A monolayer of nanoparticles was prepared followed by deposition of a thin layer of metal. By varying the base particle and metal deposited, bilateral nanoparticles were formed. The different regions of the nanoparticles were selectively functionalized with polymer linkers containing specific terminal groups, thereby creating bilateral, difunctional nanoparticles. Subsequent covalent cross-linking of different nanoparticles enabled the formation of stable architectures with programmed hierarchy and controlled chemical composition.