An Overview of SARS-CoV-2 Etiopathogenesis and Recent Developments in COVID-19 Vaccines.

The Coronavirus disease-2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has significantly impacted the health and socioeconomic status of humans worldwide. Pulmonary infection of SARS-CoV-2 results in exorbitant viral replication and associated onset of inflammatory cytokine storm and disease pathology in various internal organs. However, the etiopathogenesis of SARS-CoV-2 infection is not fully understood. Currently, there are no targeted therapies available to cure COVID-19, and most patients are treated empirically with anti-inflammatory and/or anti-viral drugs, based on the disease symptoms. Although several types of vaccines are currently implemented to control COVID-19 and prevent viral dissemination, the emergence of new variants of SARS-CoV-2 that can evade the vaccine-induced protective immunity poses challenges to current vaccination strategies and highlights the necessity to develop better and improved vaccines. In this review, we summarize the etiopathogenesis of SARS-CoV-2 and elaborately discuss various types of vaccines and vaccination strategies, focusing on those vaccines that are currently in use worldwide to combat COVID-19 or in various stages of clinical development to use in humans.

End-Terminated Poly(urethane-urea) Hybrid Approach toward Nanoporous/Microfilament Morphology.

In the present work, the effect of heteroatomic hydrogen bonding on the properties of -OH/-NH-terminated soft-segment-free polymers, viz, polyurethane (P-UT), polyurea (P-UR), and their hybrid (P-UT-UR), is explored. P-UT was synthesized from phloroglucinol and P-UR was synthesized from 1,3,5-triazine-2,4,6-triamine by employing hexamethylene diisocyanate as a counterpart. P-UT exhibited a spherulitic structure with varying sizes, whereas P-UR displayed a fibrillar structure characteristic as that of crystalline hard segments. The P-UT-UR hybrid exhibited a fine nanospherulitic structure with a high order of interconnectivity. Negative surface skewness values of -0.47 and -0.18 were measured (by AFM) for P-UT and P-UT-UR, respectively, which revealed that the surface is not smooth and is covered with features. Due to the increased H-bonding (-N-H···O-H) in P-UT-UR, its transparency decreased. A block copolymer hybrid of urethane-urea was synthesized, which preferred homoatomic H-bonding, whereas random urethane/urea bridges favored hetreoheteroatom H-bonding. A pentafluorophenyl end-functional hybrid (PFI-P-UT-UR) was synthesized, which displayed filaments of ∼2-3 µm length in contrast to the interconnected nanospherulitic structure observed for P-UT-UR. The self-aggregation and end folding led to the formation of a filament structure. By altering the chemical structure slightly, nano-ordered polyurethanes or their hybrids can be achieved.

Stimulus Responsive Remotely Rupturable Adhesive Marbles Realized through a Hybrid Nanoparticle Concept.

Adhesive marbles, an innovative concept derived from liquid marble technology that is "remotely breakable on demand" by external stimuli, offer diverse application prospects. Therefore, a chemically linked superomniphobic hybrid perfluorinated carbon black-silica nanoparticle (PCBSN) was realized by functionalizing surface groups and used for encapsulating adhesives. PCBSN successfully encapsulated liquids and adhesives to form water (WM, contact angle 158°), epoxy (EM, contact angle 145°), and silicone (SM, contact angle 135°) marbles, regardless of the surface tension and polarity. Studies on the interface characteristics revealed that the work performed for marble formation maintained an inverse relationship with the surface energy of particles and the surface tension of encapsulated liquids. The marble formation energy was determined to be higher for EM (1.071 × 10-17 J) and lower for SM (0.946 × 10-17 J). Upon exposure to laser, marbles showed a rapid photothermal response, and the heat transferability on the surface of marbles followed the order SM > EM > WM. The marbles were remotely rupturable by regulating the applied laser power, with breaking time being tunable from <10 to 500 s. The photothermal efficiency (%) of marbles can be graded as good and falls in the range of 88.6 × 10-3 (EM) and 162.9 × 10-3 (SM) at 1.5 W laser power. The marbles possessed high mechanical integrity and repeated cyclability before breaking on the rolling impact test. These adhesive marbles formed from PCBSNs may represent attractive candidates for such applications as "bonding from a distance" through remote means.

A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties.

Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings.