Being a major constituent of hard tissues found in humans, synthetic hydroxyapatite (HA) as a substitute to natural bone and teeth is gaining importance. In particular, nano hydroxyapatite is expected to impart considerably superior properties. The current research focuses on identification of mechanism of the formation of HA nano-crystals during its preparation when surfactant nano reactors are used for their nucleation and growth. In addition to having a rod-shaped morphology, high resolution electron microscopy has revealed the presence of 2-5 nm crystals within individual particles of HA. The HA particles were not completely hollow, rather nano sized spherical pores of about 5 nm size, have been observed in TEM. These pores are suggested to have formed due to evolution of gases during processing.

The COVID-19 pandemic has impacted the world population adversely, posing a threat to human health. In the past few years, various strains of SARS-CoV-2, each with different mutations in its structure, have impacted human health in negative ways. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutations influence the virulence, antibody evasion, and Angiotensin-converting enzyme 2 (ACE2) affinity of the virus. These mutations are essential to understanding how a new strain of SARS-CoV-2 has changed and its possible effects on the human body. This review provides an insight into the spike mutations of SARS-CoV-2 variants. As the current scientific data offer a scattered outlook on the various type of mutations, we aimed to categorize the mutations of Beta (B.1.351), Gamma (P.1), Delta (B.1.612.2), and Omicron (B.1.1.529) systematically according to their location in the subunit 1 (S1) and subunit 2 (S2) domains and summarized their consequences as a result. We also compared the miscellany of mutations that have emerged in all four variants to date. The comparison shows that mutations such as D614G and N501Y have emerged in all four variants of concern and that all four variants have multiple mutations within the N-terminal domain (NTD), as in the case of the Delta variant. Other mutations are scattered in the receptor binding domain (RBD) and subdomain 2 (SD2) of the S1 domain. Mutations in RBD or NTD are often associated with antibody evasion. Few mutations lie in the S2 domain in the Beta, Gamma, and Delta variants. However, in the Omicron variant many mutations occupy the S2 domain, hinting towards a much more evasive virus.

Copper oxide is a p-type semiconductor which has many applications in a different field. Copper oxide has excellent applications as an antioxidant, antibacterial, and antitumor or anticancer. Copper oxide nanoparticle combines with the cell membrane and enters into a cell; generate reactive oxygen specie (ROS), which causes oxidative stress in the cell. Oxidative stress leads to metastasis, cancer proliferation, apoptosis, DNA damage, cytotoxicity, and unregulated cell signaling. Hydroxyl free radical generated by Nanoparticles, combined with DNA and yield 8-hydroxyl-2-deoxyguanosine (8-OHdG), resultantly DNA is damaged. CuO nanoparticle shows antibacterial activity on different bacterial strains such as staphylococcus aureus, bacillus circulens BP2, Escherichia coli, and P. aeruginosa. Recently, CuO nanoparticles have applications in the detection of Cholesterol, lactate biosensor, DNA sequencing of microbe, and anti-HIV drug analysis. There is specialized CuO nanoparticle such as Glucose sensor, Hydrogen peroxide sensor, Immunosensor, Dopamine sensor for the detection of the different biomolecule. ROS generated by CuO nanoparticle causes toxicity, which leads to cell death. There is a fascinating area of research against tumors by nanoparticle use because of its antitumor nature. Metal nanoparticle exhibits anticancer activity due to physicochemical properties as antioxidant action or use of external stimuli. Free radical which are produced by the metal nanoparticle, kill cancer cells.

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