Narayana Subbiah Hari Narayana Moorthy

Natural products have long served as versatile templates for discovering lead molecules against various targets of pharmacological interest. Kojic acid, a fungal metabolite epitomizes this versatility as it elicits broad-spectrum biological properties. Described herein is a series of heteroaryl thiol-linked kojic acid derivatives that demonstrate potent acetylcholinesterase (AChE) inhibition along with anti-amyloid-β (Aβ) aggregation activity and blood brain barrier (BBB) permeability highlighting their potential as a novel class of Anti-Alzheimer’s therapeutics. Seventeen kojic acid derivatives, synthesized by incorporating three different heterocyclic thiols, were evaluated for in vitro AChE inhibition employing Ellman’s method. The most potent analogs identified from the AChE inhibition studies were further evaluated for binding to the peripheral anionic site (PAS) of AChE using the propidium iodide (PI) displacement assay, anti-amyloid-β (Aβ) aggregation inhibition using the thioflavin T assay, and BBB permeability using the PAMPA-BBB assay. Obtained findings indicated that two compounds MS 21–05 and MS 21–11 bearing a 5-methoxybenzo[d]thiazol-2-yl)thio moiety and 5-phenyl-1,3,4-oxadiazol- 2-yl)thio moiety, respectively, elicited potent AChE inhibition (IC₅₀ < 5 µM), moderate anti-Aβ aggregation effects and good BBB permeability. The molecular docking studies of compound MS 21 - 11 along with its molecular dynamics simulations at peripheral anionic site (PAS) of enzyme AChE provided structural insights into the binding mode of these derivatives. Taken together, the findings of this study establish heteroaryl thiol-linked kojic acid derivatives as a valuable molecular framework for developing anti-Alzheimer's therapeutics that target both cholinergic dysfunction and amyloid-β aggregation.

Context: Multiwalled carbon nanotubes (MWCNTs) functionalized with lysine via 1,3-dipolar cycloaddition and conjugated to galactose or mannose are potential nanocarriers that can effectively bind to the lectin receptor in MDA-MB-231 or MCF-7 breast cancer cells. In this work, a method based on molecular dynamics (MD) simulation was used to predict the interaction of these functionalized MWCNTs with doxorubicin and obtain structural evidence that allows a better understanding of the drug loading and release process. The MD simulations showed that while doxorubicin only interacted with pristine MWCNTs through π-π stacking interactions, functionalized MWCNTs were also able to establish hydrogen bonds, suggesting that the functionalized groups improve doxorubicin loading. Moreover, the elevated adsorption levels observed for functionalized nanotubes further support this enhancement in loading efficiency. MD simulations also shed light on the intratumoral pH-specific release of doxorubicin from functionalized MWCNTs, which is induced by protonation of the daunosamine moiety. The simulations show that this change in protonation leads to a lower absorption of doxorubicin to the MWCNTs. The MD studies were then experimentally validated, where functionalized MWCNTs showed improved dispersion in aqueous medium compared to pristine MWCNTs and, in agreement with the computational predictions, increased drug loading capacity. Doxorubicin-loaded functionalized MWCNTs demonstrated specific release of doxorubicin in tumor microenvironment (pH = 5.0) with negligible release in the physiological pH (pH = 7.4). Furthermore, doxorubicin-free MWNCT nanoformulations exhibited insignificant cytotoxicity. The experimental studies yielded nearly identical results to the MD studies, underlining the usefulness of the method. Our functionalized MWCNTs represent promising non-toxic nanoplatforms with enhanced aqueous dispersibility and the potential for conjugation with ligands for targeted delivery of anti-cancer drugs to breast cancer cells. Methods: The computational model of a pristine carbon nanotube was created with the buildCstruct 1.2 Python script. The lysinated functionalized groups were added with PyMOL and VMD. The carbon nanotubes and doxorubicin molecules were parameterized using the general AMBER force field, and RESP charges were determined using Gaussian 09. Molecular dynamics simulations were carried out with the AMBER 20 software package. Adsorption levels were calculated using the water-shell function of cpptraj. Cytotoxicity was evaluated via a MTT assay using MDA-MB-231 and MCF-7 breast cancer cells. Drug uptake of doxorubicin and doxorubicin-loaded MWCNTs was measured by fluorescence microscopy.

Multi-walled Carbon Nanotubes (MWCNTs) are inert structures with high aspect ratios that are widely used as vehicles for targeted drug delivery in cancer and many other diseases. They are largely non-toxic in nature however, when cells are exposed to these nanotubes for prolonged durations or at high concentrations, they show certain adverse effects. These include cytotoxicity, inflammation, generation of oxidative stress, and genotoxicity among others. To combat such adverse effects, various moieties can be attached to the surface of these nanotubes. Curcumin is a known anti-inflammatory, antioxidant and cytoprotective compound derived from a medicinal plant called Curcuma longa. In this study, we have synthesized and characterized Curcumin coated-lysine functionalized MWCNTs and further evaluated the cytoprotective, anti-inflammatory, antioxidant and antiapoptotic effect of Curcumin coating on the surface of MWCNTs. The results show a significant decrease in the level of inflammatory molecules like IL-6, IL-8, IL-1β, TNFα and NFκB in cells exposed to Curcumin-coated MWCNTs as compared to the uncoated ones at both transcript and protein levels. Further, compared to the uncoated samples, there is a reduction in ROS production and upregulation of antioxidant enzyme-Catalase in the cells treated with Curcumin-coated MWCNTs. Curcumin coating also helped in recovery of mitochondrial membrane potential in the cells exposed to MWCNTs. Lastly, cells exposed to Curcumin-coated MWCNTs showed reduced cell death as compared to the ones exposed to uncoated MWCNTs. Our findings suggest that coating of Curcumin on the surface of MWCNTs reduces its ability to cause inflammation, oxidative stress, and cell death. Graphical (a) Synthesis of Curcumin-coated-Lysine-functionalized MWCNTs. (b) Flow of research depicting experimental groups and studies performed along with the underlying techniques used.