The microbiota-brain interaction is a complex network connecting gut microbiota to the enteric nervous system (ENS) and the central nervous system (CNS) that are crucial for neurotransmission and neurological health. Metabolites such as short-chain fatty acids (SCFA), neurotransmitters, and neuromodulators from the gut microbiota influence behavior and brain function. This review focuses on the study related with gut bacteria, including Bifidobacterium infantis and Lactobacillus species, producing various metabolites in gut including bile acids, SCFA, histamine, and others to communicate with the brain or CNS. Dysbiosis can lead to neurological conditions such as anxiety, depression, PD, and AD. SCFAs from gut bacteria bind to the free fatty acid receptors of intestinal epithelial cells (IECs), affecting neurones and influencing neuroactivity. Gut bacteria also produce neurotransmitters that regulate growth hormone release through interactions with the CNS and endocrine systems. Brain signals interact directly with the pituitary and adrenal glands through the hypothalamic-pituitary-adrenal (HPA) axis, which in turn communicates with enteroendocrine cells (EECs). Investigating probiotics, prebiotics, and dietary changes could open new avenues for treatment for mental and neurological problems.

Neurodegenerative disorders represent a growing global health burden and remain largely incurable, with current therapies providing only symptomatic relief and limited disease modifications. A major obstacle to effective treatment is the inability of many neuroprotective agents to reach the brain at therapeutically relevant concentrations due to poor bioavailability and the restrictive nature of the blood–brain barrier. Plant-derived phytochemicals possess well-documented antioxidant, anti-inflammatory, anti-apoptotic, and neuromodulatory activities; however, their clinical translation has been hindered by physicochemical instability, rapid metabolism, and insufficient brain exposure. This review critically examines nanoengineered delivery systems as a strategy to overcome these limitations and enable the effective brain targeting of neuroprotective phytochemicals. By integrating mechanistic insights with preclinical and emerging clinical evidence, we compared lipid-based, polymeric, vesicular, and dendritic nanocarriers, highlighting how particle size, surface chemistry, and ligand functionalization govern blood–brain barrier transport and intracerebral distribution. Particular emphasis is placed on rational design principles that consistently enhance brain bioavailability and therapeutic efficacy across models of Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and related disorders. Beyond efficacy, we analyzed key translational challenges, including nanocarrier-associated neurotoxicity, standardization of herbal activities, and regulatory gaps unique to herbal nanomedicines. Collectively, this synthesis reframes nano-phytomedicine not as an incremental formulation upgrade but as a design-driven strategy capable of unlocking the therapeutic potential of phytochemicals for neurodegenerative disease management.

Antimicrobial resistance has created an urgent need for innovative therapeutic strategies beyond conventional antibiotics. Nanotechnology offers a groundbreaking approach to addressing this challenge by providing versatile tools for targeted antimicrobial action. This chapter explores the application of nanomaterials in combating multidrug-resistant pathogens. Emphasis is placed on their mechanisms of action, such as biofilm disruption, precision drug delivery, and enhancement of antimicrobial efficacy. This chapter also discusses recent advancements in nano-engineered systems for pathogen targeting, as well as their role in overcoming resistance mechanisms. By shedding light on the potential and limitations of nanotechnology in antimicrobial therapy, this chapter aims to present nanotechnology as a transformative approach in the ongoing battle against superbugs.

The thermophilic free-living amoeba Naegleria fowleri causes primary amoebic meningoencephalitis (PAM), a nearly universally fatal infection. Emerging clusters in India have raised concern regarding freshwater exposure and clinical outcomes. We retrospectively reviewed reported Indian PAM cases from 2018 to 2025, sourced from peer-reviewed literature, hospital records, and verified media reports. Data on demographics, exposure, diagnostics, treatment, and outcomes were extracted and summarized in two tables. Eleven cases (age range: 8 months to 47 years among cases with reported ages; age not reported for some cases) from Kolkata and Kerala were identified; exposures included ponds, lakes, water-parks, domestic water, and street-side water sources. Only two patients survived. Amphotericin B-based combinations were used, though regimens varied. The increasing incidence of PAM in India underscores the need for heightened surveillance, early diagnosis, and standardized treatment protocols.