Bacterial
endotoxins are
lipopolysaccharides bound to the bacterial cell wall and released when bacteria
rupture or disintegrate. Possible contamination of
endotoxin in ophthalmic devices can cause a painful eye
inflammation or result in toxic anterior segment syndrome after
cataract surgery. Measurement of bacterial
endotoxin in medical device materials is difficult since
endotoxin binds with
polymer matrix and some of the materials are very viscous and non-water soluble, where traditional
enzyme-based Limulus amebocyte lysate (LAL) assay cannot be applied. Here we propose a rapid and high throughput ambient ionization mass spectrometric (MS) method using direct analysis in real time (DART) for the evaluation of
endotoxin contamination in medical device materials. Large and structurally complex
endotoxin instantaneously breaks down into low-mass characteristic fragment
ions using DART and is detected by MS in both positive and negative ion modes. This method enables the identification and separation of
endotoxin from medical materials with a detection limit of 0.03 ng mL-1
endotoxins in aqueous
solution. Ophthalmic viscosurgical device materials including
sodium hyaluronate (NaHA), non-water soluble
perfluoro-n-octane (PFO) and
silicone oil (SO) were spiked with different known concentrations of
endotoxin and analyzed by DART MS, where the presence of
endotoxin was successfully detected and featured small mass fragment
ions were generated for NaHA, PFO and SO as well. Current findings showed the feasibility of measuring
endotoxin contamination in medical device materials using DART-MS, which can lead to a one-step analysis of
endotoxins in different matrices, avoiding any potential contamination during sample pre-treatment steps.