Purpose: Immunomodulatory and broad-spectrum antiviral activities have motivated the evaluation of curcumin for Coronavirus
infection 2019 (COVID-19) management. Inadequate bioavailability is the main impediment to the therapeutic effects of oral Cur. This
study aimed to develop an optimal curcumin transferosome-loaded thermosensitive in situ gel to improve its delivery to the lungs.
Methods: Transferosomes were developed by using 33 screening layouts. The phospholipid concentration as well as the concentration
and type of surfactant were considered independent variables. The entrapment efficiency (EE%), size, surface charge, and polydispersity
index (PDI) were regarded as dependent factors. A cold technique was employed to develop thermosensitive in-situ gels.
Optimized transferosomes were loaded onto the selected gels. The produced gel was assessed based on shape attributes, ex vivo
permeability enhancement, and the safety of the nasal mucosa. The in vitro cytotoxicity, antiviral cytopathic effect, and plaque assay
(CV/CPE/Plaque activity), and in vivo performance were evaluated after intranasal administration in experimental rabbits.
Results: The optimized preparation displayed a particle size of 664.3 ± 69.3 nm, EE% of 82.8 ± 0.02%, ZP of −11.23 ± 2.5 mV, and
PDI of 0.6 ± 0.03. The in vitro curcumin release from the optimized transferosomal gel was markedly improved compared with that of
the free drug-loaded gel. An ex vivo permeation study revealed a significant improvement (2.58-fold) in drug permeability across nasal
tissues of sheep. Histopathological screening confirmed the safety of these preparations. This formulation showed high antiviral
activity against SARS-CoV-2 at reduced concentrations. High relative bioavailability (226.45%) was attained after the formula
intranasally administered to rabbits compared to the free drug in-situ gel. The curcumin transferosome gel displayed a relatively
high lung accumulation after intranasal administration.
Conclusion: This study provides a promising formulation for the antiviral treatment of COVID-19 patients, which can be evaluated
further in preclinical and clinical studies.

Development of Multitarget-Directed Ligands (MTDLs) is a promising approach to combat the complex etiologies of Alzheimer’s disease (AD). Herein we report the design, synthesis, and characterization of a new series of 1,4- bisbenzylpiperazine-2-carboxylic acid derivatives 3-5(a-g), 7a-f, 8a-s, and their piperazine-2-yl-1,3,4-oxadiazole analogs 6a-g. In vitro inhibitory effect against Electrophorus electricus acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) from Equine serum was evaluated using modified Ellman’s method, considering donepezil and tacrine as reference drugs. Lineweaver–Burk plot analysis of the results proved competitive inhibition of AChE and BChE with Ki values, in low micromolar range. The free carboxylic acid series 4a-g showed enhanced selectivity for AChE. Hence, 4c, 1,4-bis (4-chlorobenzyl)-piperazinyl-2-carboxylic acid), was the most active member of this series (Ki (AChE) = 10.18 ± 1.00 µM) with clear selectivity for AChE (SI ~ 17.90). However, the hydroxamic acids 7a-f and carboxamides 8a-s congeners were more potent and selective inhibitors of BChE (SI ~ 5.38 – 21862.5). Extraordinarily, 1,4-bis (2-chlorobenzyl)-piperazinyl-2-hydroxamic acid 7b showed promising inhibitory activity against BChE enzyme (Ki = 1.6 ± 0.08 nM, SI = 21862.5), that was significantly superior to that elicited by donepezil (Ki = 12.5 ± 2.6 µM) and tacrine (Ki = 17.3 ± 2.3 nM). Cytotoxicity assessment of 4c and 7b, on human neuroblastoma (SH-SY5Y) cell lines, revealed lower toxicity than staurosporine and was nearly comparable to that of donepezil. Molecular docking and molecular dynamics simulation afforded unblemished insights into the structure–activity relationships for AChE and BChE inhibition. The results showed stable binding with fair H-bonding, hydrophobic and/or ionic interactions to the catalytic and peripheral anionic sites of the enzymes. In silico predicted ADME and physicochemical properties of conjugates showed good CNS bioavailability and safety parameters. In this regard, compound (7b) might be considered as a promising inhibitor of BChE with an innovative donepezil-based anti-Alzheimer activity. Further assessments of the most potent AChE and BChE inhibitors as potential MTDLs anti-Alzheimer’s agents are under investigation with our research group and will be published later.