Optimization of whispering gallery resonator design for biosensing applications.

Whispering gallery modes (WGMs) within microsphere cavities enable highly sensitive label-free detection of changes in the surrounding refractive index. This detection modality is of particular interest for biosensing applications. However, the majority of biosensing work utilizing WGMs to date has been conducted with resonators made from either silica or polystyrene, while other materials remain largely uninvestigated. By considering characteristics such as the quality factor and sensitivity of the resonator, the optimal WGM sensor design can be identified for various applications. This work explores the choice of resonator refractive index and size to provide design guidelines for undertaking refractive index biosensing using WGMs.

Identification of biomarkers for apoptosis in cancer cell lines using metabolomics: tools for individualized medicine.

BACKGROUND: Metabolomics is a versatile unbiased method to search for biomarkers of human disease. In particular, one approach in cancer therapy is to promote apoptosis in tumour cells; this could be improved with specific biomarkers of apoptosis for monitoring treatment. We recently observed specific metabolic patterns in apoptotic cell lines; however, in that study, apoptosis was only induced with one pro-apoptotic agent, staurosporine. OBJECTIVE: The aim of this study was to find novel biomarkers of apoptosis by verifying our previous findings using two further pro-apoptotic agents, 5-fluorouracil and etoposide, that are commonly used in anticancer treatment. METHODS: Metabolic parameters were assessed in HepG2 and HEK293 cells using the newborn screening assay adapted for cell culture approaches, quantifying the levels of amino acids and acylcarnitines with mass spectrometry. RESULTS: We were able to identify apoptosis-specific changes in the metabolite profile. Moreover, the amino acids alanine and glutamate were both significantly up-regulated in apoptotic HepG2 and HEK293 cells irrespective of the apoptosis inducer. CONCLUSION: Our observations clearly indicate the potential of metabolomics in detecting metabolic biomarkers applicable in theranostics and for monitoring drug efficacy.