Stability of Chlorophyll a Monomer Incorporated into Cremophor EL Nano-Micelles under Dark and Moderate Light Conditions

Abstract

In this paper, stability of chlorophyll a monomers encapsulated into the Cremophor EL nano-micelles was studied under dark and moderate light conditions, typical of a room with natural or artificial lighting, in the presence of oxygen. The pigment stability against visible light was determined using the dynamic light scattering and molecular spectroscopy (UV-Vis absorption and stationary fluorescence) methods. Chlorophyll a, at the molar concentration of 10-5 M, was dissolved in the 5 wt% Cremophor emulsion for comparison in the ethanolic solution. The stability of such a self-assembly pigment–detergent nano-system is important in the light of its application on the commercial-scale. The presented results indicate the high stability of the pigment monomeric molecular organization in the nano-emulsion. During the storage in the dark, the half-lifetime was calculated as about 7 months. Additionally, based on the shape of absorption and fluorescence emission spectra, chlorophyll aggregation in the Cremophor EL aqueous solution along with the time was excluded. Moreover, the average size of detergent micelles as chlorophyll carriers was not affected after 70 days of the nano-system storage. Pigment stability against the moderate white light (0.1 mW) did not differ significantly from storage conditions in the dark. The photooxidation products, detected by occurrence of new absorption and fluorescence emission bands, was estimated on the negligible level. The stability of such a self-assembly pigment–detergent nano-system would potentially broaden the field of chlorophyll a (chl a) application in the food industry, medicine or artificial photosynthesis models.

Light and Autofluorescence, Multitasking Features in Living Organisms

“…Chlorophyll optical properties have been also exploited to verify the stability of the pigment encapsulated in cremophor-nano-micelles, to overcome the pigment hydrophobicity and facilitate its use as an additive in food or drugs [43]. The optical properties of chlorophyll and of its derivatives naturally present in alimentary oils extracted from fruits and seeds are also used as biomarkers for quality controls, as to kind of cultivar, country and adulteration [44][45][46][47].…”

Effect of emulsifiers on the discoloration of chlorophyll and their potential for use in green beverages

“…It has also been reported that the discoloration of Chl was prevented in a nano-emulsion system wherein 5% of a nonionic surfactant (i.e., Cremophor EL) was employed (Janik et al, 2019(Janik et al, , 2020. This was attributed to the light stabilization of Cremophor EL through encapsulation of the monomerized Chl.…”

“…It has been reported that Chl exhibited photostability by the formation of nano-emulsions in the presence of nonionic surfactants (Janik et al, 2020(Janik et al, , 2019; such effects are also expected for emulsifiers. The purpose of this study is therefore to elucidate the effects of these selected emulsifiers on the discoloration of Chl and to determine the mechanism responsible for this effect.…”

Quantum Chemical Simulation of the Qy Absorption Spectrum of Zn Chlorin Aggregates for Artificial Photosynthesis

“…Inspired by the early studies of chlorosomes, Tamiak et al [ 11 ] synthesized Zn-centered chlorin (Zn chlorin, or Znchl for short) by replacing the central Mg atom in chlorophyll-a [ 12 , 13 ] with a Zn atom to simulate Bchl c, the dominant component of chlorosomes in the nature. Znchl (see Figure 1 b) and Bchl c molecules have similar optical properties and can self-assemble into aggregate structures in non-polar solvents, but the former is much easier to synthesize.…”