New insights into the nature of the Cibacron brilliant red 3B-A – Chitosan interaction

Cibacron brilliant red 3B-A (CBR) has been introduced to determine chitosan (CS) concentrations in solution, and several studies applied it to measure chitosan content in pharmaceutical formulations. So far, studies have relied on the absorbance band shift to 570 nm to determine the extent of the CBR – CS interaction. In this study, we show that CBR forms micro- to nanometer sized aggregates with CS, depending on their charge ratio and that other photophysical changes in CBR are induced by this interaction. We found that, besides the bathochromic band shift, aggregation induces emission at 600 nm and emission quenching at 360 nm. We compared changes CS induced in absorbance and fluorescence emission of CBR with the CS monomer glucosamine and poly(allylamine) hydrochloride, which both contain amino groups, and found that similar but less intense photophysical changes also occur. Furthermore, CS-induced circular dichroism in CBR suggests a twisted, chiral structure of these aggregates that should match with the previously published in silico simulations of the structure of CS in solution. The low linear charge density of CS and its chiral conformation are considered responsible for the enhanced photophysical response of CBR interacting with the polycation

Fully Biogenic Near-Infrared Phosphors: Phycobiliproteins and Cellulose at Force Toward Highly Efficient and Stable Bio-Hybrid Light-Emitting Diodes

<p>Stable/efficient low-energy emitters for photon down-conversion in bio-hybrid light-emitting diodes (Bio-HLEDs) are still challenging, as the archetypal fluorescent protein (FP) mCherry has led to the best deep-red Bio-HLEDs with poor stabilities: 3 h (on-chip)/160 h (remote). Capitalizing on the excellent refolding under temperature/pH/chemical stress, high brightness, and high compatibility with polysaccharides of phycobiliproteins (smURFP), first-class low-energy emitting Bio-HLEDs are achieved. They outperform those with mCherry regardless of using reference polyethylene oxide (on-chip: 24 h vs. 3 h) and new biopolymer hydroxypropyl cellulose (HPC; on-chip: 44 h vs. 3 h) coatings. Fine optimization of smURFP-HPC-coatings leads to stable record devices (on-chip: 2600 h/108 days) compared to champion devices with perylene diimides (on-chip: <700 h) and artificial FPs (on-chip: 35 h). Finally, spectroscopy/computational/thermal assays confirm that device degradation is related to the photo-induced reduction of biliverdin to bilirubin. Overall, this study pinpoints a new family of biogenic emitters toward superior protein-based lighting.</p&gt