with a DDA ranging between 70% and 85% becomes soluble in dilute acidic solutions such as acetic acid or formic acid. [1] Indeed, the primary amino groups of chitosan have a pK a of ≈6.5 so that, following protonation, they confer upon chitosan the feature of solubility in weakly acidic aqueous solution, allowing the polymer to be easily manipulated. [3] The DDA of chitosan plays a key role in determining its physicochemical properties, which are affected by the proportion of free amino groups (-NH 2) remaining on the polymeric chain upon deacetylation. Both the primary amino and secondary hydroxyl groups behave as reactive functional groups on chitosan. Indeed, these groups allow chitosan to be susceptible to chemical modifications such as acylation, tosylation, quaternization, alkylation, and O-carboxymethylation. [4] As a result, the chitosan structure can be functionalized and optimized to improve drug loading or release. [5] Chitosan-based nanocarriers (ChNCs), including nanoparticles (NPs), micelles, or polyplexes, have received significant attention for their numerous advantageous features such as natural sourcing, biodegradability, easy functionalizations, and low toxicity. [6] The mucoadhesive property of chitosan is key for drug delivery purposes. [7] Indeed, chitosan is a positively charged polymer that can form electrostatic bonds with the negatively charged mucous layer, made of mucin glycoproteins that cover the epithelial cells of the mucosa. The establishment of these bonds allows drug-loaded ChNCs to exhibit higher absorption and retention times at the target, while reducing dosing frequency. [8] Furthermore, chitosan is used as permeation enhancer since increases the uptake of the drugs through a transient and reversible opening of the tight junctions (TJs) protecting the paracellular pathway between endothelial cells in the so-called blood-brain barrier (BBB). [9] This is due to F-actin depolymerization and leakage of the TJ protein zonula occludens-1. [7] The small size and large surface area of NCs allow their passage through biological membranes, such the BBB, and accumulation at the intracellular (such as lysosomes) or intranuclear (DNA or RNA) target site. [10] ChNCs are distinctive for their ability to protect the encapsulated therapeutic agent and improve its bioavailability by altering the pharmacokinetics. [10] The endocytic mechanisms responsible for the internalization of ChNCs as a drug delivery system may differ according to the cell type and the drug to be delivered. Numerous biological and pharmacological properties characterize chitosan. These include antitumor, antifungal, antioxidant, immunoenhancing, and wound healing properties. [11] Furthermore, chitosan is Chitosan-based nanocarriers (ChNCs) are considered suitable drug carriers due to their ability to encapsulate a variety of drugs and cross biological barriers to deliver the cargo to their target site. Fluorescein isothiocyanatelabeled chitosan-based NCs (FITC@ChNCs) are used extensively in biomedical and pharmacological...