Aim: Our study focuses on the liposome-based nanoformulation, which can encapsulate Pterostilbene for its subsequent testing in relevant, model systems for cancer. Background: Pterostilbene, a plant-derived, hydrophobic, dietary stilbenoid, has been studied for its ability to induce cell death and regulate caspases in the different types of cancer cells. The potential of this drug can be improved by formulating a suitable vehicle for its delivery. Biocompatible, lipid-based nanoparticles called liposomes have been studied as a potent delivery vehicle for drugs in pre-clinical as well as in clinical studies. Liposomes can improve the drug uptake and bioavailability of the drugs. Materials and Methods: Pterostilbene loaded liposomes were constructed using DOTAP and Cholesterol, by the Thin-Film Hydration method. Along with the loaded liposomes, blank liposomes (only DOTAP and Cholesterol, without Pterostilbene) were also constructed. The liposomes were characterized for their size, Polydispersity Index (PDI) and Zeta potential using DLS. Shape of the liposomes was analysed using TEM. Encapsulation Efficiency (EE) of the Pterostilbene loaded liposomes was determined. Also, UV-Vis spectrophotometer was used to ensure that Pterostilbene was encapsulated inside the liposomes and there was no interaction between the drug and the lipids. Results: Liposomes were composed of DOTAP and Cholesterol with molar ratios 2:1. The DLS showed that the size of the Pterostilbene-loaded liposomes was 435.6±5 nm (n=3), PDI was 0.5±0.07 (n=3) and Zeta potential was -16.4±0.5 mV (n=3). The drug encapsulation efficiency was found to be 97.5±0.8% (n=3). Conclusion: Reproducibility in the results (DLS and EE data for Pterostilbene-encapsulated liposomes) provides a sound, scientific basis for evaluating their cell death potential of Pterostilbene loaded liposomes against cancer cells in comparison with that of free Pterostilbene (parent compound). Also, the experimental flow of ours can be used as a teaching tool by educators in drug delivery and allied fields.

The in vitro in silico experimental flow (multi-spectroscopy and docking) demonstrated the binding of Luteolin and Quercetin separately with Bovine Serum Albumin. For the first time, we are reporting the relative UV-visible spectroscopy-based hypsochromic shifts for both luteolin (3nm) and quercetin (4.1 nm) respectively. The drug-induced conformational change may lead to the possible shift in the tryptophan residue to a more hydrophobic environment. Our demonstration of an increased static quenching of the endogenous fluorophore in BSA validated the UV-visible spectroscopy data. However, detailed experiments will further delineate the possible relative contribution of dynamic quenching processes. The strong binding (binding constant values -10 5 L/mol) and the number of binding sites (1 for luteolin and quercetin) is consistent with published findings. Under our defined conditions, the hitherto unreported non-cooperative binding was demonstrated, based on the Hill's coefficient. Thermodynamic data qualitatively validated hydrophobicity (a positive entropy change ΔS 0 ); hydrogen bonding (a negative ΔH 0 ) and electrostatic interactions (a negative ΔH 0 and a positive ΔS 0 ). For the first time, the Infra-Red Spectroscopy (FT-IR) data showed ground state complex formation of the molecules with the model protein and may serve to corroborate our fluorescence (static quenching) data. Hydrogen bonds and hydrophobic interactions for both molecules (Ligplot Analysis) provide corroborative evidence for the molecular spectroscopy and thermodynamic data. This hitherto unreported, unique, combinatorial in vitro (multispectroscopy and thermodynamic measurements) in silico (docking and Ligplot-based analysis) experimental flow (specifically for luteolin and quercetin) provides a basis for extending such binding studies for novel receptors and/or ligands.