Design and In Vitro Evaluation of Cyclodextrin-Functionalized Albumin Nanoparticles for Intranasal Carbamazepine Brain Delivery

<b>Background/Objectives</b>: Poor aqueous solubility and limited nasal permeability remain key challenges in the intranasal delivery of carbamazepine. In this study, biocompatible bovine serum albumin nanoparticles functionalized with sulfobutyl-β-cyclodextrin (SβCD-BSA NPs), comprising individually cytocompatible components with confirmed physical interactions), were formulated for intranasal delivery of carbamazepine (CBZ). <b>Methods</b>: The ethanolic desolvation method was utilised for the preparation of the nanoparticles, with the functional moiety incorporated during nanoparticle preparation. The effects of different molar ratios of SβCD-BSA and different ethanol volume ratios were studied. For crosslinking, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), a non-toxic crosslinker, was utilised. To determine the role of the SβCD, two preparation samples were formulated, with and without SβCD. <b>Results</b>: The formulation without SβCD incorporation had a mean particle size of 125 ± 0.64 nm, polydispersity index (PDI) of 0.34, encapsulation efficiency (EE%) of 61.5 ± 1.40%, and drug-loading ratio (DL%) of 31.9 ± 1.50%. Conversely, the SβCD-functionalized formulation showed a mean particle size of 128 ± 2.12 nm, PDI of 0.21 ± 0.03, EE of 64.6 ± 0.35%, and DL of 34.28 ± 1.60%. Statistical analysis revealed that the incorporation of SβCD resulted in a statistically significant increase in both DL% and EE% (<i>p</i> < 0.05). Conversely, the observed differences in particle size and PDI were not statistically significant (<i>p</i> > 0.05). This addition provides precise context regarding the comparability of the formulations while highlighting SβCD's functional benefits in solubility and permeation. The interaction between CBZ and SβCD-BSA was confirmed using Fourier-transform infrared spectroscopy. Lastly, the prepared formulations were characterised by their physicochemical attributes and in vitro biopharmaceutical studies. It was discovered that SβCD plays a dual role, enhancing the solubility of CBZ in one scenario while promoting its nasal permeation, suggesting its potential use in epilepsy treatment. <b>Conclusions</b>: These findings highlight the potential of SβCD-BSA NPs as a versatile pharmaceutics platform for the intranasal delivery of poorly soluble CNS drugs.