Fluorescent organotin compounds as dyes in silk fibroin (Bombyx mori): ultrasound-assisted synthesis, chemo-optical characterization, cytotoxicity, and confocal fluorescence microscopy

Abstract

The fluorescent silk fibroin (FSF) is useful in a number of biomedical applications. However, some FSFs are less useful for medical applications because they are derived from toxic compounds. Here we report for the first time a fast (∼20 min), ultrasonic assisted, eco-friendly synthesis of four fluorescent organotin Schiff compounds using the corresponding aldehyde, benzoic hydrazide, and diorganotin oxide (1: MeO-L-SnPh₂, 2: tBu₂-L-SnPh₂, 3: HO-L-SnPh₂, and 4: HO-L-SnBu₂). These compounds were fully characterized by NMR spectroscopy (¹H, ¹³C, and ¹¹⁹Sn), HRMS, and UV/Vis and fluorescence spectroscopy. Single crystal X-ray diffraction investigations of complexes 1 and 2 are also reported. The as-prepared organotin Schiff compounds exhibit fluorescence at ambient temperature with good photophysical properties (fluorescence quantum yields Φ: 18–55%). These organotin compounds serve as fluorescent dyes in silk fibroin (Bombyx mori). The organotin dyed fluorescent silk fibroin showed a uniform staining, high viability, and good capacity to retain organotin compounds which might be used as innocuous scaffolds in tissue engineering.