Erythrosin B: a versatile colorimetric and fluorescent vital dye for bacteria

Rapidly assaying cell viability for diverse bacteria species is not always straightforward. In eukaryotes, cell viability is often determined using colorimetric dyes; however, such dyes have not been identified for bacteria. We screened different dyes and found that erythrosin B (EB), a visibly red dye with fluorescent properties, functions as a vital dye for many Gram-positive and -negative bacteria. EB worked at a similar concentration for all bacteria studied and incubations were as short as 5 min. Given EB's spectral properties, diverse experimental approaches are possible to rapidly visualize and/or quantitate dead bacterial cells in a population. As the first broadly applicable colorimetric viability dye for bacteria, EB provides a cost-effective alternative for researchers in academia and industry.

Analysis of Anthocyanins Extracted from the Acai Fruit (Euterpe oleracea): A Potential Novel Vital Dye for Chromovitrectomy

Purpose. To classify and quantify anthocyanins in a vital dye extracted from the acai fruit (Euterpe oleracea), adjust pH and osmolarity, and perform lyophilization to develop a new chromovitrectomy dye. Methods. Three dye concentrations 10%, 25%, and 35% (equivalent to 100, 250, and 350 mg of lyophilized acai fruit pulp extract samples) were evaluated when diluted in 1 ml of phosphate-buffered solution (pH 7 and 300 mOsm). The dye was analyzed by mass spectrometry and high-performance liquid chromatography (HPLC) to identify and quantify anthocyanins molecules. Results. The pH and osmolarity correction and lyophilization were performed without damaging the anthocyanin molecular structure. Mass spectrometry confirmed the presence of five anthocyanins in the three concentrations of the dye. Cyanidin-3-O-glucoside was the major anthocyanin found. HPLC showed that the concentration of anthocyanin was similar, independent of the dye concentration tested. Conclusions. Lyophilization and the correction of pH and osmolarity (7.00 and 300 mOsm, resp.) were performed successfully. Five anthocyanins are present in the dye from the acai fruit. The major anthocyanin is cyanidin-3-O-glucoside. Independent of the dye concentration tested, the anthocyanin concentration was similar. Standardized chemical characteristics of this new dye may allow its use during chromovitrectomy in humans.