Carbon Quantum Dots Found and Isolated from Egg Yolk Oil

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Egg yolk oil (EYO), is a traditional Chinese medicine that has been used for more than a thousand years to treat all kinds of burn wounds and eczema, with the first recorded treatment being published in 500 AD. In an interesting study, a new material was isolated from EYO and identified as carbon dots (CDs). Additional pharmacodynamics (conducted in mice) revealed that these CDs exerted a dose-dependent effect on haemostasis.

A team of researchers from China’s Beijing University of Chinese Medicine have discovered, and isolated, carbon quantum dots from EYO, which show significant haemostatic properties. Traditionally, egg yolk oil (EYO) is produced by refining cooked egg yolks of Gallus gallus domesticus Brisson (Black-Bone Silky Fowl). It has been used as a traditional medicine throughout Chinese history, to as far back as the Ming Dynasty. EYO is currently used for all kinds of burns and eczema treatments in various clinics due to its analgesic, anti-oxidative, and anti-aging properties. It is also known to enhance memory, reduce blood fat, and improve microcirculation and oedema.EYO is produced by heating cooked eggs under a low flame, followed by water evaporation, and then heating under a high flame until an oil flow is induced. This EYO is black in color, with an unpleasant odor. It is quite unstable and only produced in low yields.

Many synthetic methods attempt to extract EYO such as dry distillation, baking, reduced pressure distillation, solvent extraction, supercritical CO2 extraction, sub-critical propane extraction and enzyme-based processes.

The synthetic method to produce EYO is noted to be similar to the method of carbon dot formation. Carbon dots are one of the most promising fluorescent nanocomposite materials in research today- due to their unique photoluminescence, high resistance to photo-bleaching, high aqueous solubility, high biocompatibility and low toxicity properties. The similarities between the methods, prompted the researchers to ask the following question: ‘do carbon dots exist in EYO?’

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To test this premise, the researchers extracted EYO using pure water and studied the water components. The extract possessed a strong bright blue fluorescence at 365 nm, prompting the researchers to use a combination of water extraction, dialysis, and ultra-filtration methods to extract and purify the EYO. They identified the active ingredients to be carbon dots; further tests were carried to study their properties and activities.

To prove the existence of carbon dots, the researchers used a combination of Transmission electron microscopy (TEM, JEN-1230, Japan Electron Optics Laboratory), high-resolution transmission electron microscopy (HR-TEM, Tecnai G2 20 TEM, FEI), fluorescence microscopy (OLYMPUS IX73), ultraviolet-visible (UV-Vis) spectroscopy (CECIL) and Fourier-transform infrared spectroscopy (FTIR, Thermo spectrometer).

The researchers found that the carbon dots were almost spherical in nature, with an average size of less than 10 nm, a lattice spacing of 0.267 nm and were mainly composed of carbon, oxygen and iron atoms.. From their analyses, the researchers concluded that the carbon dots were mainly composed of sp2 hybridized graphitic carbon atoms, with sp3 carbons and oxygen containing moieties occupying the surface. The surface groups are the active sites.

The researchers also investigated the haemostatic properties of the carbon dots on male Kunming mice. . The researchers found that the carbon dots released a dose-dependent effect on haemostasis. Both the tail and liver hemorrhaging experiments showed a significantly shorter bleeding time in the mice treated with carbon dots. The coagulation assays showed that the intrinsic blood coagulation system and the fibrinogen system were activated in the presence of the carbon dots. It has therefore been concluded that these carbon dots have the ability to activate haemostasis.

The discovery of such properties will allow further investigation into this field and other areas of traditional Chinese medicine.

Sources and Further Reading

This article was updated on 12th March, 2019.

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