No abstract

Keyword: GO, Open and close form of GO, Alzheimer drug entrap and release, TPP, Drug delivery. nm nmGraphene oxide, (GO) in the size range of 40 -200 nm, has been extracted from low grade coal or wood charcoal by leaching with dil nitric acid then neutralize with aqueous sodium hydroxide. We show that tetraphenylporphyrin (TPP ) type large molecule got entrapped inside GO in its closed form. Such GO -TPP composite retains the property of pure GO with respect to its solubility in ethanol in which free TPP is insoluble. Further we show that in phosphate buffered saline (PBS) this composite is soluble to retain the TPP inside displaying the combined spectral signatures of GO and TPP at pH, 6.8. The water insoluble TPP inside the composite cannot be extracted by dichloromethane where free TPP is highly soluble. On raising the pH of PBS buffer to 7.4, it releases all entrapped TPP by opening the clenched fist form. We further show that donepezil, a drug, used in Alzheimer treatment gets entrapped by GO to remain inside in PBS which is released at higher pH . The clenched and open fist forms of GO are related to pH dependent epoxide -diols inter-conversion that uniquely provide GO to act as Trojan horse in carrying a drug molecule and its delivery under physio-compatible environment.Abstract : Graphene oxide, (GO), present in the low grade coal, formed under natural coalifcation of plants is extracted by leaching with cold nitric acid. Similar easy extraction of GO is followed from wood charcoal. Such GO sheets are thermally not very stable and on aging is fragmented into small spherical shape . These can be solubilized in 10% NaOH and reprecipitating these by adjusting the pH around 7. Further purification could be achieved by extracting with ethanol where this is highly soluble . This GO is larger than graphene quantum dot and get folded to close like fisted form and it is shown to entrap tetraphenylporphyrin (TPP). The TPP in the composite is not soluble in dichloromethane where free TPP is highly soluble. Such GO -TPP composite retains the property of pure GO as it is soluble in ethanol in which free TPP is insoluble. It is shown that in phosphate buffered saline (PBS, pH , 6.8) this composite is soluble and remained intact . At higher pH of PBS buffer it releases all entrapped TPP by opening the clenched fist form. Similarly the drug Donepezil, used in Alzheimer treatment gets entrapped by GO which is also released at higher pH, 7.4. The clenched fist form of corrugated GO is related to the pH dependent epoxide dominated structure as proposed by Hofmann and Holst's model and the open structure may be dominated by hydroxyl groups ( enol ) following Ruess's model . Such pH dependent inter-conversion uniquely provide GO to act as Trojan horse in carrying a drug molecule andits release under physio-compatible environment.

Nanosized reduced graphene oxide (rGO) is found in active microcarbon used in popular face cream from the manufacturers like Ponds, Nevia, and Garnier which, under visible light exposure, gets activated by aerial oxygen to generate reactive oxygen species (ROS) harmful to skin.