Neurodegenerative disorders (NDs) have become a serious health problem worldwide due to the rapid increase in the number of people that are affected and the constantly aging population. Among all NDs, Alzheimer’s and Parkinson’s disease are the most common, and many efforts have been made in the development of effective and reliable therapeutic strategies. The intranasal route of drug administration offers numerous advantages, such as bypassing the blood–brain barrier and providing a direct entrance to the brain through the olfactory and trigeminal neurons. The present review summarizes the available information on recent advances in micro- and nanoscale nose-to-brain drug-delivery systems as a novel strategy for the treatment of Alzheimer’s and Parkinson’s disease. Specifically, polymer- and lipid-base micro- and nanoparticles have been studied as a feasible approach to increase the brain bioavailability of certain drugs. Furthermore, nanocomposites are discussed as a suitable formulation for administration into the nasal cavity.

Direct nose-to-brain drug delivery offers the opportunity to treat central nervous system disorders more effectively due to the possibility of drug molecules reaching the brain without passing through the blood–brain barrier. Such a delivery route allows the desired anatomic site to be reached while ensuring drug effectiveness, minimizing side effects, and limiting drug losses and degradation. However, the absorption of intranasally administered entities is a complex process that considerably depends on the interplay between the characteristics of the drug delivery systems and the nasal mucosa. Various preclinical models (in silico, in vitro, ex vivo, and in vivo) are used to study the transport of drugs after intranasal administration. The present review article attempts to summarize the different computational and experimental models used so far to investigate the direct delivery of therapeutic agents or colloidal carriers from the nasal cavity to the brain tissue. Moreover, it provides a critical evaluation of the data available from different studies and identifies the advantages and disadvantages of each model.

Nanotherapeutics have emerged as novel unparalleled drug delivery systems (DDSs) for the treatment of neurodegenerative disorders. By applying different technological approaches, nanoparticles can be engineered to possess different functionalities. In recent years, the developed, stimuli-responsive nanocarriers stand out as novel complex DDSs ensuring selective and specific drug delivery in response to different endogenous and exogenous stimuli. Due to the multifaceted pathophysiology of the nervous system, a major challenge in modern neuropharmacology is the development of effective therapies ensuring high efficacy and low toxicity. Functionalization of the nanocarriers to react to specific microenvironmental changes in the nervous system tissues or external stimulations significantly enhances the efficacy of drug delivery. This review discusses the microenvironmental characteristics of some common neurological diseases in-depth and provides a comprehensive overview on the progress of the development of exogenous and endogenous stimuli-sensitive nanocarriers for the treatment of Alzheimer’s and Parkinson’s disease.

Despite the progress made in the fight against the COVID-19 pandemic, it still poses dramatic challenges for scientists around the world. Various approaches are applied, including repurposed medications and alternative routes for administration. Several vaccines have been approved, and many more are under clinical and preclinical investigation. This review aims to systemize the available information and to outline the key therapeutic strategies for COVID-19, based on the nasal route of administration.

The present work is focused on the preparation of an optimal model of poly-ε-caprolactone nanoparticles as potential carriers for nasal administration of idebenone. A solvent/evaporation technique was used for nanoparticle preparation. Poly-ε-caprolactone with different molecular weights (14,000 and 80,000 g/mol) was used. Polysorbate 20 and Poloxamer 407, alone and in combination, were used as emulsifiers at different concentrations to obtain a stable formulation. The nanoparticles were characterized using dynamic light scattering, SEM, TEM, and FTIR. The resulting structures were spherical in shape and their size distribution depended on the type of emulsifier. The average particle size ranged from 188 to 628 nm. The effect of molecular weight and type of emulsifier was established. Optimal models of appropriate size for nasal administration were selected for inclusion of idebenone. Three models of idebenone-loaded nanoparticles were developed and the effect of molecular weight on the encapsulation efficiency was investigated. Increased encapsulation efficiency was found when poly-ε-caprolactone with lower molecular weight was used. The molecular weight also affected the drug release from the nanostructures. Dissolution study data were fitted into various kinetic models and the Korsmeyer–Peppas model was found to be indicative of the release mechanism of idebenone.

Neurodegenerative disorders (NDs), including Alzheimer’s disease and Parkinson’s disease, pose a significant global health challenge characterized by progressive neuronal loss and limited therapeutic options. Early diagnosis remains a considerable hurdle due to the absence of reliable biomarkers and the restrictive nature of the blood–brain barrier (BBB), which complicates effective drug delivery. Magnetic nanoparticles (MNPs), particularly those based on iron oxide, have emerged as promising tools for both diagnostic and therapeutic applications in NDs, thanks to their superparamagnetism, biocompatibility, and customizable surfaces. This review examines various synthesis strategies for MNPs, encompassing physical methods (such as lithography, ball milling, and laser ablation) and chemical approaches (co-precipitation, thermal decomposition, hydrothermal synthesis, sol–gel processes, and polyacrylamide gel techniques), while highlighting how these techniques influence particle properties. This review also explores recent advancements in surface functionalization using polymers and coatings to enhance circulation time in the bloodstream and improve BBB penetration for targeted delivery. Furthermore, it emphasizes both in vitro and in vivo applications, showcasing MNPs’ effectiveness in enhancing imaging sensitivity and enabling targeted drug and gene delivery. By linking synthesis methods, functionalization techniques, and biomedical outcomes, this review illustrates the transformative potential of MNPs as next-generation theranostic agents in precision medicine for neurodegenerative diseases.