Purple to Yellow Silicone Elastomers: Design of a Versatile Sensor for Screening Antioxidant Activity

Abstract

Antioxidants play a key role in counteracting the adverse effects of oxidative stress in human organisms. Thus, there is a huge demand for the development of smart and convenient assays for the evaluation of antioxidant activity of synthetic and natural compounds, food samples, plant extracts, etc. The design of a solid-state, flexible, and portable format of the traditional in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical test is reported. For the first time, purple DPPH radicals are physically immobilized into a silicone matrix by means of a facile and rapid process. The working principle of the resulting sensor is based on the colorimetric process that is associated with the redox reaction of DPPH radicals with antioxidants. When an antioxidant reacts with the sensor, a color change from purple to yellow can be perceived by the naked eye. The response of the sensor is investigated qualitatively and quantitatively toward food samples and selected antioxidants of different natures, and solubilized in different media. It is demonstrated that the DPPH silicone sensor is highly versatile and can be used as a ready-to-use sensor for direct colorimetric detection of antioxidants.

Learning from the trees: biomimetic crosslinking of silicones by phenolic coupling

“…S6A ESI †); 19 a very distinct purple to yellow transition occurs upon reaction with phenol reducing agents. 21,22 Based on these assays, the AO activity directly correlated with the quantity of eugenol present on the silicone polymer for the product Tn-Eu and Px-Eu oils, (Fig. S6 ESI †).…”

Antioxidant Silicone Elastomers without Covalent Cross-Links

“…It has previously been shown that reactions of DPPH (2,2-diphenyl-1-picrylhydrazyl)a redox indicator that antioxidants cause to convert from a purple to yellow colorcan be performed in a silicone environment . All of the natural phenols shown in Figure exhibit antioxidant activity on their own to differing degrees; pyrogallol is a more efficient antioxidant in comparison to catechol. , Once within a silicone matrix, the differences between antioxidants were more subtle.…”

Antioxidant silicone oils from natural antioxidants

“…Traditional strategies for controlling M c allows one to choose both eugenol content in the elastomers and crosslink density; the latter property links directly to hardness/modulus and extension at break. DPPH is a particularly useful molecule to quantify antioxidant activity (Figure S2B, ESI †) 29,30 by a readily observable colorimetric change from purple to yellow, 31 along with other traditional spectroscopic means. The AO activities of PDMS modified with retinoate 3T, 3P, vitamin E (-tocopherol) 4T (for 4P-17, 4P-26 see Figure S10, ESI †) or eugenol 5T, 5P-6 were measured in 96-well plates at active antioxidant concentrations ranging from 0.1 mM to 100 mM (based on the respective antioxidant moiety); the pendent HSi silicone oil (P-4) and Please do not adjust margins Please do not adjust margins vitamin A, homoallyl retinoate, vitamin E, and eugenol were used as negative and positive controls, respectively.…”

“…DPPH is a particularly useful molecule to quantify antioxidant activity (Fig. S2B, ESI †) 29,30 by a readily observable colorimetric change from purple to yellow, 31 along with other traditional spectroscopic means. The AO activities of PDMS modified with retinoate 3T, 3P, vitamin E (α-tocopherol) 4T (for 4P-17, 4P-26 see Fig.…”