Extensive growth of microscopic algae and cyanobacteria results in harmful algal blooms (HABs) in marine, brackish, and freshwater environments. HABs can harm humans and animals through their toxicity or by producing ecological conditions such as oxygen depletion, which can kill fish and other economically or ecologically important organisms. This review summarizes the reports on various HABs that are able to bring about marine fish kills. The predominant HABs, their toxins, and their effects on fishes spread across various parts of the globe are discussed. The mechanism of HAB-driven fish kills is discussed based on the available reports, and existing mitigation methods are presented. Lapses in the large-scale implementation of mitigation methods demonstrated under laboratory conditions are projected. Clay-related technologies and nano-sorption-based nanotechnologies, although proven to make significant contributions, have not been put to use in real-world conditions. The gaps in the technology transfer of the accomplished mitigation prototypes are highlighted. Further uses of remote sensing and machine learning state-of-the-art techniques for the detection and identification of HABs are recommended.

After decades of research and development concerning cancer treatment, cancer is still at large and very much a threat to the global human population. Cancer remedies have been sought from all possible directions, including chemicals, irradiation, nanomaterials, natural compounds, and the like. In this current review, we surveyed the milestones achieved by green tea catechins and what has been accomplished in cancer therapy. Specifically, we have assessed the synergistic anticarcinogenic effects when green tea catechins (GTCs) are combined with other antioxidant-rich natural compounds. Living in an age of inadequacies, combinatorial approaches are gaining momentum, and GTCs have progressed much, yet there are insufficiencies that can be improvised when combined with natural antioxidant compounds. This review highlights that there are not many reports in this specific area and encourages and recommends research attention in this direction. The antioxidant/prooxidant mechanisms of GTCs have also been highlighted. The current scenario and the future of such combinatorial approaches have been addressed, and the lacunae in this aspect have been discussed.

Chitosan is a natural biodegradable polymer that is recovered from marine shell wastes. It has been widely employed in anticancer, antioxidant, and antibacterial applications due to its outstanding qualities, including biological compatibility, muco-adhesivity, hemocompatibility, and biodegradability. The contributions of this polymer have established it with respect to biomedical applications. The distinct morphologies of chitosan, such as in nanoparticulate and microparticulate for MS and as derivatives and composites have extended its visages even beyond biomedicine. This review specifically summarizes the biomedical highlights of chitosan-based MS. Special attention has been focused on the antimicrobial accomplishments of chitosan-based MS. The impact of chitosan MS against bacteria, fungi and viruses has been reviewed. The gaps in its usage for antimicrobial investigations have been addressed. The lack of significant contribution from chitosan MS towards antifungal and antiviral applications has been explicitly highlighted. Future recommendations and the scope for expansion have been suggested.

Chitosan derivatives and composites are the next generation polymers for biomedical applications. With their humble origins from the second most abundant naturally available polymer chitin, chitosan is currently one of the most promising polymer systems, with wide biological applications. This current review gives a bird’s eye view of the antimicrobial applications of chitosan composites and derivatives. The antiviral activity and the mechanisms behind the inhibitory activity of these components have been reviewed. Specifically, the anti-COVID-19 aspects of chitosan composites and their derivatives have been compiled from the existing scattered reports and presented. Defeating COVID-19 is the battle of this century, and the chitosan derivative-based combat strategies naturally become very attractive. The challenges ahead and future recommendations have been addressed.

Carbon nanotubes have revolutionalized various areas of science and technology. Conceptually, carbon nanotubes can be thought of as all sp² carbons arranged in graphene sheets, which have been rolled up to form a seamless hollow tube. The tubes can be capped at the ends by a fullerene type hemisphere and can have lengths ranging from tens of nanometers to several microns. They can be subdivided into two classes: the single walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT). SWNT, as the name suggests, consists of a single hollow tube with diameters between 0.4 and 2 nm while MWNTs are composed of multiple concentric nanotubes ∼0.34 nm apart where the final MWNT has diameters of 2–100 nm. The present review will describe the types of carbon nanotubes, methods of synthesis, properties and some of the applications having commercial importance emphasizing biomedical applications.