Graphical abstract The coronavirus disease-19 has left a permanent mark on the history of the human race. Severe acute respiratory syndrome coronavirus-2 is a positive-sense single-stranded RNA virus, first reported in Wuhan, China, in December 2019 and from there took over the world. Being highly susceptible to mutations, the virus's numerous variants started to appear, and some were more lethal and infectious than the parent. The effectiveness of the vaccine is also affected severely against the new variant. In this study, the infectious mechanism of the coronavirus is explained with a focus on different variants and their respective mutations, which play a critical role in the increased transmissibility, infectivity, and immune escape of the virus. As India has already faced the second wave of the pandemic, the future outlook on the likeliness of a third wave with respect to the Indian variants such as kappa, delta, and Delta Plus is also discussed. This review article aims to reflect the catastrophe of the variants of SARS-CoV-2 and the possibility of developing even more severe variants in the near future.

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A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic composite particles of FeO and rGO containing 71% (rGO-FeO-M1), 36% (rGO-FeO-M2), and 18% (rGO-FeO-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-FeO composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-FeO-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure FeO and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-FeO-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and FeO may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward Vibrio fischeri than commercial pure FeO particles.

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