*Review* **Antioxidant Functionalized Nanoparticles: A Combat against Oxidative Stress**

**Harsh Kumar 1, Kanchan Bhardwaj 2, Eugenie Nepovimova 3, Kamil Kuˇca 3,\*, Daljeet Singh Dhanjal 4, Sonali Bhardwaj 4, Shashi Kant Bhatia 5, Rachna Verma <sup>2</sup> and Dinesh Kumar 1,\***


Received: 7 June 2020; Accepted: 6 July 2020; Published: 8 July 2020

**Abstract:** Numerous abiotic stresses trigger the overproduction of reactive oxygen species (ROS) that are highly toxic and reactive. These ROS are known to cause damage to carbohydrates, DNA, lipids and proteins, and build the oxidative stress and results in the induction of various diseases. To resolve this issue, antioxidants molecules have gained significant attention to scavenge these free radicals and ROS. However, poor absorption ability, difficulty in crossing the cell membranes and degradation of these antioxidants during delivery are the few challenges associated with both natural and synthetic antioxidants that limit their bioavailability. Moreover, the use of nanoparticles as an antioxidant is overlooked, and is limited to a few nanomaterials. To address these issues, antioxidant functionalized nanoparticles derived from various biological origin have emerged as an important alternative, because of properties like biocompatibility, high stability and targeted delivery. Algae, bacteria, fungi, lichens and plants are known as the producers of diverse secondary metabolites and phenolic compounds with extraordinary antioxidant properties. Hence, these compounds could be used in amalgamation with biogenic derived nanoparticles (NPs) for better antioxidant potential. This review intends to increase our knowledge about the antioxidant functionalized nanoparticles and the mechanism by which antioxidants empower nanoparticles to combat oxidative stress.

**Keywords:** oxidative stress; antioxidants; nanoparticles; biological nano-antioxidants
