Evaluating the cytotoxicity of Ge-Sb-Se chalcogenide glass optical fibres on 3T3 mouse fibroblasts.

In vivo cancer detection based on the mid-infrared molecular fingerprint of tissue is promising for the fast diagnosis and treatment of suspected cancer patients. Few materials are mid-infrared transmissive, even fewer, which can be converted into functional, low-loss optical fibres for in vivo non-invasive testing. Chalcogenide-based glass optical fibres are, however, one of the few. These glasses are transmissive in the mid-infrared and are currently under development for use in molecular sensing devices. The cytotoxicity of these materials is however unknown. The cytotoxicity of Ge-Sb-Se chalcogenide optical glass fibres on 3T3 mouse fibroblast cells is here investigated. Fibres exposed to four different pre-treatment conditions are used: as-drawn (AD), propylamine-etched (PE), oxidised-and-washed (OW) and oxidised (Ox). To achieve the latter two conditions, fibres are treated with H2O2(aqueous (aq.)) and dried to produce a surface oxide layer; this is either washed off (OW) or left on the glass surface (Ox). Cellular response is investigated via 3 day elution and 14 day direct contact trials. The concentration of the metalloids (Ge, Sb and Se) in each leachate was measured via inductively coupled plasma mass spectrometry. Cell viability is assessed using the neutral red assay and scanning electron microscopy. The concentration of Ge, Sb and Se ions after a 3 day dissolution was as follows. In AD leachates, Ge: 0.40 mg L-1, Sb: 0.17 mg L-1, and Se: 0.06 mg L-1. In PE leachates, Ge: 0.22 mg L-1, Sb: 0.15 mg L-1, and Se: 0.02 mg L-1. In Ox leachates, Ge: 823.8 mg L-1, Sb: 2586.6 mg L-1, and Se: 3750 mg L-1. Direct contact trials show confluent cell layers on AD, PE and OW fibres after 14 days, while no cells are observed on the Ox surfaces. A >50% cell viability is observed in AD, PE and OW eluates after 3 days, when compared with Ox eluates (<10% cell viability). Toxicity in Ox is attributed to the notable pH change, from neutral pH 7.49 to acidic pH 2.44, that takes place on dissolution of the surface oxide layer in the growth media. We conclude, as-prepared Ge-Sb-Se glasses are cytocompatible and toxicity arises when an oxide layer is forced to develop on the glass surface.

Determining the continuous thermo-optic coefficients of chalcogenide glass thin films in the MIR region using FTIR transmission spectra.

A new method (FTIR continuous dn / dT method, n is refractive index and T temperature) for measuring the continuous thermo-optic coefficients of thin transparent films in the mid-infrared (MIR) spectral region is introduced. The technique is based on Fourier transform infrared (FTIR) transmission spectra measured at different temperatures. It is shown that this method can successfully determine the thermo-optic coefficient of chalcogenide glass thin films (of batch compositions Ge20Sb10Se70 at. % (atomic %) and Ge16As24Se15.5Te44.5 at. %) over the wavelength range from 2 to 25 µm. The measurement precision error is less than ± 11.5 ppm / °C over the wavelength range from 6 to 20 µm. The precision is much better than that provided by the prism minimum deviation method or an improved Swanepoel method.