Green nanotechnology is a promising technology that has a wide range of applications in pharmaceuticals today because they offer a higher surface-area-to-volume ratio. Algal-based nanoparticles (NPs) are the subject of intense research interest today for their potential to treat and prevent infections caused by infectious microorganisms that are antibiotic resistant. Algae contain a variety of therapeutically potential bioactive ingredients, including chlorophyll, phycobilin, phenolics, flavonoids, glucosides, tannins, and saponins. As a result, NPs made from algae could be used as therapeutic antimicrobials. Due to their higher surface-area-to-volume ratios compared to their macroscopic components, metallic nanoparticles are more reactive and have toxic effects on their therapy. For pharmaceutical and biomedical applications, green synthesis restricts the use of physical and chemical methods of metallic nanoparticle synthesis, and it can be carried out in an environmentally friendly and relatively low-cost manner. The majority of macroalgae and some microalgae have latent antimicrobial activity and are used in the synthesis of metallic nanoparticles. A potential application in the field of nanomedicine and the establishment of a potential pharmacophore against microorganisms may result from the synthesis of algal-based NPs. Only a few studies have been done on the potential antimicrobial, antifungal, and antibacterial activity of algae-based NPs. As a result, the study will concentrate on the environmentally friendly synthesis of various NPs and their therapeutic potential, with a focus on their antibacterial activity. Thus, the aim of this study is to review all the literature available on the synthesis and characterization of the algal nanoparticles and their potential application as an antibacterial agent.

Plants rely heavily on a complex innate immune system to repel microbial attacks, and antimicrobial peptides (AMPs) play a crucial role as central immune modulators of their immune response. These small, structurally diverse molecules exhibit broad-spectrum activities against bacteria, fungi, viruses, and nematodes through direct membrane disruption, interference with intracellular targets, and modulation of host signaling networks. Recent progress in multi-omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, combined with synthetic biology, has led to a significant increase in our understanding of classification, biosynthetic pathways, structure-function relationships, and the regulatory integration of AMPs within pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). Some of these latter tools accelerate rational peptide design and enable applications in agriculture: among others, transgenic crops possessing constitutive or pathogen-inducible AMP expression, as well as peptide-based agrochemicals, represent eco-friendly alternatives to classical pesticides. Despite such breakthroughs, major challenges persist that currently limit large-scale deployment: rapid pathogen evolution of resistance, insufficient target specificity, peptide instability under field conditions, potential phytotoxicity, and complex regulatory approval pathways. Such barriers will require integrated systems-biology approaches, improved delivery platforms, for example, nanotechnology or bioencapsulation, and precise engineering of AMP-host interactions. This review consolidates current information on plant AMPs, highlighting transformative multi-omics insights and critically assessing the remaining hurdles to be overcome for the full utilization of AMPs in next-generation sustainable crop protection and global food security.